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"Global information systems have the potential of providing decision makers with timely spatial information about earth systems. This information will come from diverse sources, including field monitoring, remotely sensed imagery, and environmental models. Of the three the latter has the greatest potential of providing regional and global scale information on the behavior of environmental systems, which may be vital for setting multi-governmental policy and for making decisions that are critical to quality of life. However, environmental models have limited prootocol for quality control and standardization. They tend to have weak or poorly defined semantics and so their output is often difficult to interpret outside a very limited range of applications for which they are designed. This paper considers this issue with respect to spatially distributed environmental models. A method of measuring the semantic proximity between components of large, integrated models is presented, along with an example illustrating its application. It is concluded that many of the issues associated with weak model semantics can be resolved with the addition of self-evaluating logic and context-based tools that present the semantic weaknesses to the end-user."
"Many commercial database systems use some form of statistics, typically histograms, to summarize the contents of relations and permit efficient estimation of required quantities. While there has been considerable work done on identifying good histograms for the estimation of query-result sizes, little attention has been paid to the estimation of the data distribution of the result, which is of importance in query optimization. In this paper, we prove that the optimal histogram for estimating the size of the result of a join operator is optimal for estimating its data distribution as well. We also study the effectiveness of these optimal histograms in the context of an important application that requires estimates for the data distribution of a query result: load-balancing for parallel Hybrid hash joins. We derive a cost formula to capture the effect of data skew in both the input and output relations on the load and use the optimal histograms to estimate this cost most accurately. We have developed and implemented a load balancing algorithm using these histograms on a simulator for the Gamma parallel database system. The experiments establish the superiority of this approach compared to earlier ones in handling all kinds and levels of skew while incurring negligible overhead."
"This chapter describes an efficient method for maintaining materialized views with non-distributive aggregate functions, even in the presence of super aggregates. Incremental view maintenance is an extremely important aspect of the modern database management systems. It enables the fast execution of complex queries without sacrificing the freshness of the data. However, the maintenance of views defined with non-distributive aggregate functions was not sufficiently explored. Incremental refresh has been studied in depth only for a subset of the aggregate functions. Materialized views, or automatic summary tables (ASTs), are increasingly being used to facilitate the analysis of the large amounts of data being collected in relational databases. The use of ASTs can significantly reduce the execution time of a query, often by orders of magnitude, which is particularly significant for databases with sizes in the terabyte to petabyte range, whose queries are designed by business intelligence tools or decision support systems. Such queries tend to be extremely complex, involving a large number of join and grouping operations."
"Although many of the problems that must be solved by an object-oriented database system are similar to problems solved by relational systems, there are also significant problems that are unique. In particular, an object query can include a path expression to traverse a number of related collections. The order of collection traversals given by the path expression may not be the most efficient to process the query. This generates a critical problem for object query optimizer to select an algorithm to process the query based on direct navigation or various combinations of joins. This paper studies the different algorithms to process path expressions with predicates, including depth first navigation, forward and reverse joins. Using a cost model, it then compares their performances in different cases, according to memory size, selectivity of predicates, fan out between collections, etc.. It also presents a heuristic-based algorithm to find profitable n-ary operators for traversing collections, thus reducing the search space of query plans to process a query with a qualified path expression. An implementation based on the O2 system demonstrates the validity of the results."
"The spatial join operation is benchmarked using variants of well-known spatial data structures such as the R-tree, R -tree, R + -tree, and the PMR quadtree. The focus is on a spatial join with spatial output because the result of the spatial join frequently serves as input to subsequent spatial operations (i.e., a cascaded spatial join as would be common in a spatial spreadsheet). Thus, in addition to the time required to perform the spatial join itself (whose output is not always required to be spatial), the time to build the spatial data structure also plays an important role in the benchmark. The studied quantities are the time to build the data structure and the time to do the spatial join in an application domain consisting of planar line segment data. Experiments reveal that spatial data structures based on a disjoint decomposition of space and bounding boxes (i.e., the R + -tree and the PMR quadtree with bounding boxes) outperform the other structures that are based upon"
"Searching a database of 3D-volume objects for objects which are similar to a given 3D search object is an important problem which arises in number of database applications- for example, in Medicine and CAD. In this paper, we present a new geometrybased solution to the problem of searching for similar 3D-volume objects. The problem is motivated from a real application in the medical domain where volume similarity is used as a basis for surgery decisions. Our solution for an efficient similarity search on large databases of 3D volume objects is based on a new geometric index structure. The basic idea of our new approach is to use the concept of hierarchical approximations of the 3D objects to speed up the search process. We formally show the correctness of our new approach and introduce two instantiations of our general idea, which are based on cuboid and octree approximations. We finally provide a performance evaluation of our new index structure revealing significant performance improvements over existing approaches."
"Authors and publishers who wish their publications to be considered for review in Computational Linguistics should send a copy to the book review editor, Graeme Hirst, Department of Computer Science, University of Toronto, Toronto, Canada M5S 3G4. All relevant books received will be listed, but not all can be reviewed. Technical reports (other than dissertations) will not be listed or reviewed. Authors should be aware that some publishers will not send books for review (even when instructed to do so); authors wishing to inquire as to whether their book has been received for review may contact the book review editor."
"The explosion in complex multimedia content makes it crucial for database systems to support such data efficiently. This paper argues that the ¡°blackbox¡± ADTs used in current object-relational systems inhibit their performance, thereby limiting their use in emerging applications. Instead, the next generation of object-relational database systems should be based on enhanced abstract data type (E-ADT) technology. An (E-ADT) can expose the semantics of its methods to the database system, thereby permitting advanced query optimizations. Fundamental architectural changes are required to build a database system with E-ADTs; the added functionality should not compromise the modularity of data types and the extensibility of the type system. The implementation issues have been explored through the development of E-ADTs in Predator. Initial performance results demonstrate an order of magnitude in performance improvements."
"DART '96 was held in conjunction with the Conference of Information and Knowledge Management (CIKM) on Nov 15th in Baltimore. Its goal was to provide a forum for researchers and practitioners involved in integrating concepts and technologies from active and real-time databases to discuss the state of the art and chart a course of action. To this end, nine speakers from academia, industry, and research laboratories were invited to provide a perspective on the theory and practice underlying active real-time databases. In addition, some selected papers were presented briefly to complement the invited speakers' talks. The second half of the workshop was devoted to discussions aimed at identifying the problems that still need to be addressed in the contexts of the diverse target applications."
"Object-Relational DBMSs have been receiving a great deal of attention from industry analysts and press as the next generation of database management systems. The motivation for a next generation DBMS is driven by the reality of shortened business cycles. This dynamic environment demands fast, cost-effective, time-to-market of new or modified business processes, services, and products. To support this important business need, the next generation DBMS must: 1. leverage the large investments made in existing relational technology, both in data and skill set; 2. Take advantage of the flexibility, productivity, and performance benefits of OO modeling; and 3. Integrate robust DBMS services for production quality systems. The objective of this article is to provide a brief overview of UniSQL's commercial object-relational database management system."
"In this work, we devise and evaluate control strategies for combining two potentially powerful buffer management techniques in object bases: (1) buffer pool segmentation with segment-specific replacement criteria and (2) dual buffering consisting of copying objects from pages into object buffers. We distinguish two dimensions for exerting control on the buffer pool: (1) the copying time determines when objects are copied from their memory-resident home page and (2) the relocation time determines the occasion on which a (copied) object is transferred back into its home page. Along both dimensions, we distinguish an eager and a lazy strategy. Our extensive experimental results indicate that a lazy object copying combined with an eager relocation strategy is almost always superior and significantly outperforms page-based buffering in most applications. 1 Introduction In the Eighties, object-oriented database systems emerged as the potential next-generation database technology."
"Streams are continuous data feeds generated by such sources as sensors, satellites, and stock feeds. Monitoring applications track data from numerous streams, filtering them for signs of abnormal activity, and processing them for purposes of filtering,"
"Active databases and real-time databases have been important areas of research in the recent past. It has been recognized that many benefits can be gained by integrating active and real-time database technologies. However, there has not been much work done in the area of transaction processing in active real-time databases. This paper deals with an important aspect of transaction processing in active real-time databases, namely the problem of assigning priorities to transactions. In these systems, time-constrained transactions trigger other transactions during their execution. We present three policies for assigning priorities to parent, immediate and deferred transactions executing on a multiprocessor system and then evaluate the policies through simulation. The policies use different amounts of semantic information about transactions to assign the priorities. The simulator has been validated against the results of earlier published studies."
"Many applications require the management of spatial data. Clustering large spatial databases is an important problem which tries to find the densely populated regions in the feature space to be used in data mining, knowledge discovery, or efficient information retrieval. A good clustering approach should be efficient and detect clusters of arbitrary shape. It must be insensitive to the outliers (noise) and the order of input data. We pro-pose WaveCluster, a novel clustering approach based on wavelet transforms, which satisfies all the above requirements. Using multi-resolution property of wavelet transforms, we can effectively identify arbitrary shape clus-ters at different degrees of accuracy. We also demonstrate that WaveCluster is highly effi-cient in terms of time complexity. Experi-mental results on very large data sets are pre-sented which show the efficiency and effective-ness of the proposed approach compared to the other recent clustering methods"
"In this paper we present a mechanism for approximately translating Boolean query constraints across heterogeneous information sources. Achieving the best translation is challenging because sources support different constraints for formulating queries, and often these constraints cannot be precisely translated. For instance, a query [score > 8] might be ""perfectly"" translated as [rating > 0.8] at some site, but can only be approximated as [grade = A] at another. Unlike other work, our general framework adopts a customizable ""closeness"" metric for the translation that combines both precision and recall. Our results show that for query translation we need to handle interdependencies among both query conjuncts as well as disjuncts. As the basis, we identify the essential requirements of a rule system for users to encode the mappings for atomic semantic units. Our algorithm then translates complex queries by rewriting them in terms of the semantic units. We show that, under practical assumptions, our algorithm generates the best approximate translations with respect to the closeness metric of choice. We also present a case study to show how our technique may be applied in practice."
"Classification is an important data mining problem. Although classification is a well-studied problem, most of the current classi-fication algorithms require that all or a por-tion of the the entire dataset remain perma-nently in memory. This limits their suitability for mining over large databases. We present a new decision-tree-based classification algo-rithm, called SPRINT that removes all of the memory restrictions, and is fast and scalable. The algorithm has also been designed to be easily parallelized, allowing many processors to work together to build a single consistent model. This parallelization, also presented here, exhibits excellent scalability as well. The combination of these characteristics makes the proposed algorithm an ideal tool for data min-ing."
"Text documents often contain valuable structured data that is hidden in regular English sentences. This data is best exploited if available as a relational table that we could use for answering precise queries or for running data mining tasks. We explore a technique for extracting such tables from document collections that requires only a handful of training examples from users. These examples are used to generate extraction patterns, that in turn result in new tuples being extracted from the document collection. We build on this idea and present our Snowball system. Snowball introduces novel strategies for generating patterns and extracting tuples from plain-text documents. At each iteration of the extraction process, Snowball evaluates the quality of these patterns and tuples without human intervention, and keeps only the most reliable ones for the next iteration."
"Decision support applications involve complex queries on very large databases. Since response times should be small, query optimization is critical. Users typically view the data as multidimensional data cubes. Each cell of the data cube is a view consisting of an aggregation of interest, like total sales. The values of many of these cells are dependent on the values of other cells in the data cube..A common and powerful query optimization technique is to materialize some or all of these cells rather than compute them from raw data each time. Commercial systems differ mainly in their approach to materializing the data cube. In this paper, we investigate the issue of which cells (views) to materialize when it is too expensive to materialize all views. A lattice framework is used to express dependencies among views. We present greedy algorithms that work off this lattice and determine a good set of views to materialize. The greedy algorithm performs within a small constant factor of optimal under a variety of models. We then consider the most common case of the hypercube lattice and examine the choice of materialized views for hypercubes in detail, giving some good tradeoffs between the space used and the average time to answer a query."
"Abstract¡ªCommercial applications usually rely on precompiled parameterized procedures to interact with a database. Unfortunately, executing a procedure with a set of parameters different from those used at compilation time may be arbitrarily suboptimal. Parametric query optimization (PQO) attempts to solve this problem by exhaustively determining the optimal plans at each point of the parameter space at compile time. However, PQO is likely not cost-effective if the query is executed infrequently or if it is executed with values only within a subset of the parameter space. In this paper, we propose instead to progressively explore the parameter space and build a parametric plan during several executions of the same query. We introduce algorithms that, as parametric plans are populated, are able to frequently bypass the optimizer but still execute optimal or near-optimal plans. Index Terms¡ªParametric query optimization, adaptive optimization, selectivity estimation."
"Data warehousing systems integrate information from operational data sources into a central repository to enable analysis and mining of the integrated information. During the integration process, source data typically undergoes a series of transformations, which may vary from simple algebraic operations or aggregations to complex ¡°data cleansing ¡± procedures. In a warehousing environment, the data lineage problem is that of tracing warehouse data items back to the original source items from which they were derived. We formally define the lineage tracing problem in the presence of general data warehouse transformations, and we present algorithms for lineage tracing in this environment. Our tracing procedures take advantage of known structure or properties of transformations when present, but also work in the absence of such information. Our results can be used as the basis for a lineage tracing tool in a general warehousing setting, and also can guide the design of data warehouses that enable efficient lineage tracing."
"With the use of data warehousing and online analytical processing (OLAP) for decision support applications new security issues arise. The goal of this paper is to introduce an OLAP security design methodology, pointing out fields that require further research work. We present possible access control requirements categorized by their complexity. OLAP security mechanisms and their implementations in commercial systems are presented and checked for their suitability to address the requirements."
"We present a random walk as an e?cient and accurate approach to approximating cer-tain aggregate queries about web pages. Our method uses a novel random walk to produce an almost uniformly distributed sample of web pages. The walk traverses a dynamically built regular undirected graph. Queries we have es-timated using this method include the cover-age of search engines, the proportion of pages belonging to.com and other domains, and the average size of web pages. Strong experimen-tal evidence suggests that our walk produces accurate results quickly using very limited re-sources."
" In addition it constructs a special node Authors() and connects it to all pages corresponding to ""Author""s. The output graph is called SiteGraph. One way to write this in StruQL is: input DataGraph where Root(x); x ! ! y; y ! l ! z; l in f""Paper"", ""TechReport"", ""Title"", ""Abstract"", ""Author""g create Authors(); Page(y); Page(z) link Page(y) ! l ! Page(z) where x ! ! y1; y1 ! ""Author"" ! z1 link Authors() ! ""Author"" ! Page(z1) output SiteGraph 2 In order to integrate information from several source, we allow multiple input graphs. When multiple input graphs are present, every occurrence of a collection needs to be preceded by a graph name. For clarity of presentation however, we focus on queries with only one input graph. Intermixing the where; create; link clauses makes the query easier to read. This is nothing more than syntactic convenience, since the meaning is the same as that of the query in which all clauses are joined together: input DataGraph where Root"
" Several formal models for database access control have been proposed. However, little attention has been paid to temporal issues like authorizations with limited validity or obtained by deductive reasoning with temporal constraints. We present an access control model in which authorizations contain periodic temporal intervals of validity. An authorization is automatically granted in the time intervals specified by a periodic expression and revoked when such intervals expire. Deductive temporal rules with periodicity and order constraints are provided to derive new authorizations based on the presence or absence of other authorizations in specific periods of time. We prove the uniqueness of the set of implicit authorizations derivable at a given instant from the explicit ones, and we propose an algorithm to compute the global set of valid authorizations."
" Data mining is computationally expensive. Since the benefits of data mining results are unpredictable, organizations may not be willing to buy new hardware for that purpose. We will present a system that enables data mining applications to run in parallel on networks of workstations in a fault-tolerant manner. We will describe our parallelization of a combinatorial pattern discovery algorithm and a classification tree algorithm. We will demonstrate the effectiveness of our system with two real applications: discovering active motifs in protein sequences and predicting foreign exchange rate movement."
" A very promising idea for fast searching in traditional and multimedia databases is to map objects into points in k-d space, using k feature-extraction functions, provided by a domain expert [Jag91]. Thus, we can subsequently use highly fine-tuned spatial access methods (SAMs), to answer several types of queries, including the `Query By Example' type (which translates to a range query); the `all pairs' query (which translates to a spatial join [BKSS94]); the nearest-neighbor or best-match query, etc. However, designing feature extraction functions can be hard. It is relatively easier for a domain expert to assess the similarity/distance of two objects. Given only the distance information though, it is not obvious how to map objects into points. This is exactly the topic of this paper. We describe a fast algorithm to map objects into points in some k-dimensional space (k is user-defined), such that the dis-similarities are preserved."
" The database systems have nowadays an increasingly important role in the knowledge-based society, in which computers have penetrated all fields of activity and the Internet tends to develop worldwide. In the current informatics context, the development of the applications with databases is the work of the specialists. Using databases, reach a database from various applications, and also some of related concepts, have become accessible to all categories of IT users. This paper aims to summarize the curricular area regarding the fundamental database systems issues, which are necessary in order to train specialists in economic informatics higher education. The database systems integrate and interfere with several informatics technologies and therefore are more difficult to understand and use. Thus, students should know already a set of minimum, mandatory concepts and their practical implementation: computer systems, programming techniques, programming languages, data structures. The article also presents the actual trends in the evolution of the database systems, in the context of economic informatics."
" Web caching proxy servers are essential for improving web performance and scalability, and recent research has focused on making proxy caching work for database-backed web sites. In this paper, we explore a new proxy caching framework that exploits the query semantics of HTML forms. We identify two common classes of form-based queries from real-world database-backed web sites, namely, keyword-based queries and function-embedded queries. Using typical examples of these queries, we study two representative caching schemes within our framework: (i) traditional passive query caching, and (ii) active query caching, in which the proxy cache can service a request by evaluating a query over the contents of the cache. Results from our experimental implementation show that our form-based proxy is a general and flexible approach that efficiently enables active caching schemes for database-backed web sites. Furthermore, handling query containment at the proxy yields significant performance advantages over passive query caching, but extending the power of the active cache to do full semantic caching appears to be less generally effective."
" Structured data stored in les can bene t from standard database technology. In particular, we show here how such data can be queried and updated using declarative database languages. We introduce the notion of structuring schema which consists of a grammar annotated with database programs. Based on a structuring schema, a le can be viewed as a database structure, queried and updated as such. For queries, weshow that almost standard database optimization techniques can be used to answer queries without having to construct the entire database. For updates, we study in depth the propagation to the le of an update speci ed on the database view of this le. The problem is infeasible in general and we present anumber of negative results. The positive results consist of techniques that allow to propagate updates e ciently under some reasonable locality conditions on the structuring schemas."
" The challenge of peer-to-peer computing goes beyond simple file sharing. In the DBGlobe project, we view the multitude of peers carrying data and services as a superdatabase. Our goal is to develop a data management system for modeling, indexing and querying data hosted by such massively distributed, autonomous and possibly mobile peers. We employ a service-oriented approach, in that data are encapsulated in services. Direct querying of data is also supported by an XML-based query language. In this paper, we present our research results along the following topics: (a) infrastructure support, including mobile peers and the creation of context-dependent communities, (b) metadata management for services and peers, including locationdependent data, (c) filters for efficiently routing path queries on hierarchical data, and (d) querying using the AXML language that incorporates service calls inside XML documents."
"Because of the Internet we believe that in the long run there will be alternative providers for all of these three resources for any given application. Data providers will bring more and more data and more and more different kinds of data to the net. Likewise, function providers will develop new methods to process and work with the data; e.g., function providers might develop new algorithms to compress data or to produce thumbnails out of large images and try to sell these on the Internet. It is also conceivable, that some people allow other people to use spare cycles of their idle machines in the Internet (as in the Condor system of the University of Wisconsin) or that some companies (cycle providers) even specialize on selling computing time to businesses that occasionally need to carry out very complex operations for which regular hardware is not sufficient."
"Conduct of scientific and engineering research is becoming critically dependent on effective management of scientific and engineering data and technical information. The rapid advances in scientific instrumentation, computer and communication technologies enable the scientists to collect, generate, process, and share unprecedented volumes of data. For example, the Earth Observing System Data and Information System (EOSDIS) has the task to manage the data from NASA¡¯s Earth science research satellites and field measurement programs, and other data essential for the interpretation of these measurements in support of global change research. Apart from being able to handle a stream of 1 terabyte of data daily by the year 2000, EOSDIS will also need to provide transparent access to heterogeneous data held in the archives of several US government agencies, organizations and countries. A single graphical user interface employing the Global Change Master Directory needs to help users locate data sets of interest among massive and diverse data sets, or find the appropriate data analysis tools, regardless of their location. Another major international effort in the area of human genome research faces some similar, as well as unique issues due to the complexity of the genome data, special querying requirements and much more heterogeneous collections of data."
"Recently there has been an increasing interest in supporting bulk operations on multidimensional index structures. Bulk loading refers to the process of creating an initial index structure for a presumably very large data set. In this paper, we present a generic algorithm for bulk loading which is applicable to a broad class of index structures. Our approach differs completely from previous ones for the following reasons. First, sorting multidimensional data according to a predefined global ordering is completely avoided. Instead, our approach is based on the standard routines for splitting and merging pages which are already fully implemented in the corresponding index structure. Second, in contrast to inserting records one by one, our approach is based on the idea of inserting multiple records simultaneously. As an example we demonstrate in this paper how to apply our technique to the R-tree family. For R-trees we show that the I/O performance of our generic algorithm meets the lower bound of external sorting. Empirical results demonstrate that performance improvements are also achieved in practice without sacrificing query performance"
"To speed-up clustering algorithms, data summarization methods have been proposed, which first summarize the data set by computing suitable representative objects. Then, a clustering algorithm is applied to these representatives only, and a clustering structure for the whole data set is derived, based on the result for the representatives. Most previous methods are, however, limited in their application domain. They are in general based on sufficient statistics such as the linear sum of a set of points, which assumes that the data is from a vector space. On the other hand, in many important applications, the data is from a metric non-vector space, and only distances between objects can be exploited to construct effective data summarizations. In this paper, we develop a new data summarization method based only on distance information that can be applied directly to non-vector data. An extensive performance evaluation shows that our method is very effective in finding the hierarchical clustering structure of non-vector data using only a very small number of data summarizations, thus resulting in a large reduction of runtime while trading only very little clustering quality."
"Detecting and extracting modifications from information sources is an integral part of data warehousing. For unsophisticated sources, in practice it is often necessary to infer modifications by periodically comparing snapshots of data from the source. Although this sapshot di/rem tial problem is closely related to traditional joins and outerjoins, there are significant differences, which lead to simple new algorithms. In particular, we present algorithms that perform (possibly lossy) compression of records. We also present a window algorithm that works very well if the snapshots are not ""very different."" The algorithms are studied via analysis and an implementation of two of them; the results illustrate the potential gains achievable with the new algorithms."
This paper describes a model that integrates the execution of triggers with the evaluation of declarative constraints in SQL database systems. This model achieves full compatibility with the 1992 international standard for SQL (SQL92). It preserves the set semantics for declarative constraint evaluation while allowing the execution of powerful procedural triggers. It was implemented in DB2 for common servers and was recently accepted as the model for the emerging SQL standard (SQW).
"Applications in which plain text coexists with structured data are pervasive. Commercial relational database management systems (RDBMSs) generally provide querying capabilities for text attributes that incorporate state-of-the-art information retrieval (IR) relevance ranking strategies, but this search functionality requires that queries specify the exact column or columns against which a given list of keywords is to be matched."
"Real-world entities are inherently spatially and temporally referenced, and database applications increasingly exploit databases that record the past, present, and anticipatedfu tu locations of entities, e.g., the residences ofcuEERRx7 obtained by the geo-coding of addresses. Indices that efficiently suient quient on the spatio-temporal extents ofsuE entities are needed. However, past indexing research has progressed in largely separate spatial and temporal streams. Adding time dimensions to spatial indices, as if time were a spatial dimension, neither suther7 nor exploits the special properties of time. On the other hand, temporal indices are generally not amenable to extension with spatial dimensions. This paper proposes the first efficient and versatile index for a general class of spatio-temporal data: the discretely changing spatial aspect of an object may be a point or may have an extent; both transaction time and valid time are su;wkP-7y and a generalized notion of thecu;kx: time, now, is accommodated for both temporal dimensions. The index is based on the R # -tree and provides means of prioritizing space versu time, which enables it to adapt to spatially and temporally restrictivequ@;-P7 Performance experiments are reported that evalu-; pertinent aspects of the index."
"This paper presents a novel strategy for temporal coalescing. Temporal coalescing merges the temporal extents of value-equivalent tuples. A temporal extent is usually coalesced offline and stored since coalescing is an expensive operation. But the temporal extent of a tuple with now, times at different granularities, or incomplete times cannot be determined until query evaluation. This paper presents a strategy to partially coalesce temporal extents by identifying regions that are potentially covered. The covered regions can be used to evaluate temporal predicates and constructors on the coalesced extent. Our strategy uses standard relational database technology. We quantify the cost using the Oracle DBMS."
"The paper presents a systematic review of the relative efficacy of traditional listing and the USPS address list as sampling frames for national probability samples of households. NORC and ISR collaborated to compare these two national area-probability sampling frames for household surveys. We conducted this comparison in an ongoing survey operation which combines the current wave of the HRS with the first wave of NSHAP. Since 2000, survey samplers have been exploring the potential of the USPS address lists to serve as a sampling frame for probability samples from the general population. We report the relative coverage properties of the two frames, as well as predictors of the coverage and performance of the USPS frame. The research provides insight into the coverage and cost/benefit trade-offs that researchers can expect from traditionally listed frames and USPS address databases."
"Because the truth is that relational database management systems aren¡¯t very good at what they were supposed to do-help us get answers from our data-unless we ignore a good deal of relational dogma and use a new approach to data modeling when we¡¯re building a decision support database. The relationally correct data modeling everyone is taught in school is only useful for achieving high performance in on-line transaction processing. The resulting model fragments the data into many tables of relatively equal width and depth to speed transactions along. But using that model with a realworld decision support system almost guarantees failure. Take the case of a mid-size durable goods manufacturer, one ofthe smokestacks on the horizon. After a year¡¯s effort, IS staffers had a database design, had loaded several hundred megabytes of data from 6 miilion invoices into a multiprocessor Teradata relational database machine, and users had begun to try to use the system. But there were 50 tables in their fairly typical schema."
"With recent advances in storage and network technology it is now possible to provide movie on demand (MOD) service, eliminating the inflexibility inherent in todays broadcast cable systems. A MOD server is a computer system that stores movies in compressed digital form and provides support for different portions of compressed movie data to be accessed and transmitted concurrently. In this paper, we present a low-cost storage architecture for a MOD server that relies principally on disks. The high bandwidths of disks in conjunction with a clever strategy for striping movies on them is utilized in order to enable simultaneous access and transmission of ""certain"" different portions of a movie. We also present a wide range of schemes for implementing VCR-like functions."
"Database management systems (DBMS) store and manage large sets of shared data whereas application programs perform the data processing tasks, e. g., to run the business of a company. Often, these programs are written in various programming languages (PLs) embodying different type systems. Thus, DBMSs should be ¡°multi-lingual¡° to serve the application requests. This is typically achieved by providing a DBMS and its database language (DBL), like SQL2, with an own type system. To access the database (DB), a DBL/PL-coupling called database API (DB-API or API for short) is required."
"Clustering is the process of grouping a set of objects into classes of similar objects. Although definitions of similarity vary from one clustering model to another, in most of these models the concept of similarity is based on distances, e.g., Euclidean distance or cosine distance. In other words, similar objects are required to have close values on at least a set of dimensions. In this paper, we explore a more general type of similarity. Under the pCluster model we proposed, two objects are similar if they exhibit a coherent pattern on a subset of dimensions. For instance, in DNA microarray analysis, the expression levels of two genes may rise and fall synchronously in response to a set of environmental stimuli. Although the magnitude of their expression levels may not be close, the patterns they exhibit can be very much alike. Discovery of such clusters of genes is essential in revealing significant connections in gene regulatory networks. E-commerce applications, such as collaborative filtering, can also benefit from the new model, which captures not only the closeness of values of certain leading indicators but also the closeness of (purchasing, browsing, etc.) patterns exhibited by the customers."
"Introduction MOCHA1 is a novel database middleware system designed to interconnect data sources distributed over a wide area network. MOCHA is built around the notion that the middleware for a large-scale distributed environment should be selfextensible. This means that new application-specific data types and query operators needed for query processing are deployed to remote sites in automatic fashion by the middleware system itself. In MOCHA, this is realized by shipping Java classes implementing these types or operators to the remote sites, where they can be used to manipulate the data of interest. All these Java classes are first stored in one or more code repositories from which MOCHA later retrieves and deploys them on a ¡°need-to-do¡± basis. A major goal behind this idea of automatic code deployment is to fulfill the need for application-specific processing components at remote sites that do not provide them. MOCHA capitalizes on its ability to automatically deploy code to provide an efficient query processing service. By shipping code for query operators, MOCHA can produce efficient plans that place the execution of powerful data-reducing operators (filters) on the data sources. Examples of such operators are aggregates, predicates and data mining operators, which return a much smaller abstraction of the original data. In contrast, datainflating operators that produce results larger that their arguments are evaluated near the client."
"Though the query is posted in key words, the returned results contain exactly the information that the user is querying for, which may not be explicitly specified in the input query. The required information is often not contained in the Web pages whose URLs are returned by a search engine. FACT is capable of navigating in the neighborhood of these pages to find those that really contain the queried segments. The system does not require a prior knowledge about users such as user profiles or preprocessing of Web pages such as wrapper generation."
"Regular readers of this column will have become familiar with database language SQL -- indeed, most readers are already familiar with it. We have also discussed the fact that the SQL standard is being published in multiple parts and have even discussed one of those parts in some detail[l].Another standard, based on SQL and its structured user-defined types[2], has been developed and published by the International Organization for Standardization (ISO). This standard, like SQL, is divided into multiple parts (more independent than the parts of SQL, in fact). Some parts of this other standard, known as SQL/MM, have already been published and are currently in revision, while others are still in preparation for initial publication.In this issue, we introduce SQL/MM and review each of its parts, necessarily at a high level."
"Adapt/X Harness is an information integration system, platform, and tool set that provides integrated and seamless access to heterogeneous and distributed information in a networked environment (LAN, WAN, Intranets, and the global Internet). It allows cost-effective access, keyword and attribute queries, navigation, and linking and operations on these information resources using popular Internet browsers without requiring any translation, transfer, or rehosting of the original information resource. Information resources such as text and multimedia documents, files of various types, software applications, relational databases, email messages, and references can all be ¡°registered¡± with Adapt/X Harness and are organized into collections. Information consumers can then use a standard WWW browser to search for required the information with specific (keyword or attribute) queries or they can browse through a ¡°repository¡± looking for items of interest."
XML data is likely to be widely used as a data exchange format but users also need to store and query XML data. The purpose of this panel is to explore whether and how to best provide this functionality.
"Data warehousing and on-line analytical processing (OLAP) are essential elements of decision support, which has increasingly become a focus of the database industry. Many commercial products and services are now available, and all of the principal database management system vendors now have offerings in these areas. Decision support places some rather different requirements on database technology compared to traditional on-line transaction processing applications. This paper provides an overview of data warehousing and OLAP technologies, with an emphasis on their new requirements. We describe back end tools for extracting, cleaning and loading data into a data warehouse; multidimensional data models typical of OLAP; front end client tools for querying and data analysis; server extensions for efficient query processing; and tools for metadata management and for managing the warehouse. In addition to surveying the state of the art, this paper also identifies some promising research issues, some of which are related to problems that the database research community has worked on for years, but others are only just beginning to be addressed."
"Multimedia information systems have emerged as an essential component of many application domains ranging from library information systems to entertainment technology. However, most implementations of these systems cannot support the continuous display of multimedia objects and suffer from frequent disruptions and delays termed hiccups. This is due to the low I/O bandwidth of the current disk technology, the high bandwidth requirement of multimedia objects, and the large size of these objects that almost always requires them to be disk resident. One approach to resolve this limitation is to decluster a multimedia object across multiple disk drives in order to employ the aggregate bandwidth of several disks to support the continuous retrieval (and display) of objects."
"Sensor networking technologies have developed very rapidly in the last ten years. In many situations, high quality multimedia streams may be required for providing detailed information of the hot spots in a large scale network. With the limited capabilities of sensor node and sensor network, it is very difficult to support multimedia streams in current sensor network structure. In this paper, we propose to enhance the sensor network by deploying limited number of mobile ""swarms"". The swarm nodes have much higher capabilities than the sensor nodes in terms of both hardware functionalities and networking capabilities. The mobile swarms can be directed to the hot spots in the sensor network to provide detailed information of the intended area. With the help of mobile swarms, high quality of multimedia streams can be supported in the large scale sensor network without too much cost. The wireless backbone network for connecting different swarms and the routing schemes for supporting such a unified architecture is also discussed and verified via simulations."
Some problems connected with the handling of null values in SQL are discussed. A definition of sure answers to SQL queries is proposed which takes care of the ¡°no information¡± meaning of null values in SQL. An algorithm is presented for modifying SQL queries such that answers are not changed for databases without null values but sure answers are obtained for arbitrary databases with standard SQL semantics.
"Materialization is a useful abstraction pattern that can be identified in many application settings. Intuitively, materialization is the relationship between a class of categories (e.g., models of cars) and a class of more concrete objects (e.g., individual cars). This paper gives a quasi-formal semantic definition of materialization in terms of the usual is-a and isof abstractions, and of a class/metaclass correspondence. New and powerful inheritance mechanisms are associated with materialization. Examples, properties, and extensions of materialization are also presented. Providing materialization as an abstraction mechanism for conceptual modeling enhances expressiveness by a controled introduction of classification at the application level."
"The emergence of dynamic page generation is primarily driven by the need to deliver customized and personalized Web pages. Dynamic scripting technologies allow Web sites to assemble pages \on the y"" based on various run-time parameters (e.g., form-based parameters) in an attempt to tailor content to each individual user. Web developers have a wide variety of choices in dynamic scripting languages, e.g., Java Server Pages (JSP) and servlets from Sun; Active Server Pages (ASP) from Microsoft. A major disadvantage of dynamic scripting technologies, however, is that they reduce Web and application server scalability because of the additional load placed on the Web/application server. In addition to pure script execution overhead, there are several other types of delay associated with generating dynamic pages"
"Semantic data modelling I is the established method for the requirements definition and the conceptual specification of application systems. In large projects and especially in enterprise data models the cost of creating a data model amount to a large proportion of the overall cost. On the other hand there is a general pressure to reduce the cost of data modelling for application systems to harness the skyrocketing costs of data processing in a colnpany. The standard textbook modelling process calls for the modelling of single entities to represent simple facts and combining these into a model in a bottom up fashion: 'An entity is a concept, person, thing"
"Over the past years several works have proposed access con- trol models for XML data where only read-access rights over non-recursive DTDs are considered. A small number of works have studied the access rights for updates. In this paper, we present a general model for specifying access con- trol on XML data in the presence of the update operations of W3C XQuery Update Facility. Our approach for enforc- ing such update specification is based on the notion of query rewriting. A major issue is that query rewriting for recursive DTDs is still an open problem. We show that this limitation can be avoided using only the expressive power of the stan- dard XPath, and we propose a linear algorithm to rewrite each update operation defined over an arbitrary DTD (re- cursive or not) into a safe one in order to be evaluated only over the XML data which can be updated by the user. This paper represents the first effort for securely XML updating in the presence of arbitrary DTDs (recursive or not) and a rich fragment of XPath"
"The Information Management Group at Dublin City University has research themes such as digital multimedia, interoperable systems and database engineering. In the area of digital multimedia, a collaboration with our School of Electronic Engineering has formed the Centre for Digital Video Processing, a university designated research centre whose aim is to research, develop and evaluate content-based operations on digital video information. To achieve this goal, the range of expertise in this centre covers the complete gamut from image analysis and feature extraction through to video search engine technology and interfaces to video browsing. The Interoperable Systems Group has research interests in federated databases and interoperability, object modelling and database engineering. This report describes the research activities of the major groupings within the Information Management community in Dublin City"
"RasDaMan is a universal ¡ª i.e., domain-independent ¡ª array DBMS for multidimensional arrays of arbitrary size and structure. A declarative, SQL-based array query language offers flexible retrieval and manipulation. Efficient server-based query evaluation is enabled by an intelligent optimizer and a streamlined storage architecture based on flexible array tiling and compression."
"The proliferation of mobile and pervasive computing devices has brought energy constraints into the limelight, together with performance considerations. Energy-conscious design is important at all levels of the system architecture, and the software has a key role to play in conserving the battery energy on these devices. With the increasing popularity of spatial database applications, and their anticipated deployment on mobile devices (such as road atlases and GPS based applications), it is critical to examine the energy implications of spatial data storage and access methods for memory resident datasets."
"Microsoft SQL Server was successful for many years for transaction processing and decision sup- port workloads with neither merge join nor hash join, relying entirely on nested loops and index nested loops join. How much difference do addi- tional join algorithms really make, and how much system performance do they actually add? In a pure OLTP workload that requires only record-to-record navigation, intuition agrees that index nested loops join is sufficient. For a DSS workload, however, the question is much more complex. To answer this question, we have analyzed TPC-D query perform- ance using an internal build of SQL Server with merge-join and hash-join enabled and disabled. It shows that merge join and hash join are both re- quired to achieve the best performance for decision support workloads"
"A star schema is very popular for modeling data warehouses and data marts. Therefore, it is important that a database system which is used for implementing such a data warehouse or data mart is able to efficiently handle operations on such a schema. In this paper we will describe how one of these operations, the join operation --- probably the most important operation --- is implemented in the IBM Informix Extended Parallel Server (XPS)."
"Smartcards are the most secure portable computing device today. They have been used successfully in applications involving money, and proprietary and personal data (such as banking, healthcare, insurance, etc.). As smartcards get more powerful (with 32-bit CPU and more than 1 MB of stable memory in the next versions) and become multi-application, the need for database management arises. However, smartcards have severe hardware limitations (very slow write, very little RAM, constrained stable memory, no autonomy, etc.) which make traditional database technology irrelevant. The major problem is scaling down database techniques so they perform well under these limitations."
"With the increasing importance of XML, LDAP directories, and text-based information sources on the Internet, there is an ever-greater need to evaluate queries involving (sub)string matching. In many cases, matches need to be on multiple attributes/dimensions, with correlations between the multiple dimensions. Effective query optimization in this context requires good selectivity estimates. In this paper, we use pruned count-suffix trees (PSTs) as the basic data structure for substring selectivity estimation. For the 1-D problem, we present a novel technique called MO (Maximal Overlap)."
"The main characteristics of the language are its descriptiveness, its capability to map between schemas written in the relational, object-oriented, ER, or EXPRESS data model, and its facilities for specifying user-defined update operations on the view that are to be propagated to the data sources. Finally, we briefly discuss how this mapping information is employed to convert queries formulated with respect to the integrated view, into database operations over the heterogeneous data sources."
"There are also problems in using values obtained from the study populations to those in economic models and the difficulty of predicting health state values in those who avoid a fracture. The review recommends a set of health state values as part of a ¡°reference case¡± for use in economic models. Due to the paucity of good quality of estimates in this area, further recommendations are made regarding the design of future studies to collect HSVs relevant to economic models."
"To begin with, which RM do we mean? There are several lines of RM and each has had its own evolution. The original line was originated by E.F.Codd who developed during the Seventies what he later named RM/VI. In 1979 he proposed a new model, the RM/T that meant a huge change from the original RM approach. In the Eighties, sensing that plain people did not keep up with him"
"Historically, there has been little overlap between the database and networking research communities; they operate on very different levels and focus on very different issues. While this strict separation of concerns has lasted for many years, in this talk I will argue that the gap has recently narrowed to the point where the two fields now have much to say to each other."
"Our design enables self starting distributed queries that jump directly to the lowest common ancestor of the query result, dramatically reducing query response times. We present a novel query-evaluate gather technique (using XSLT) for detecting (1) which data in a local database fragment is part of the query result, and (2) how to gather the missing parts. We define partitioning and cache invariants that ensure that even partial matches on cached data are exploited and that correct answers are returned, despite our dynamic query-driven caching. Experimental results demonstrate that our techniques dramatically increase query throughputs and decrease query response times in wide area sensor databases."
"Query processing is one of the most, critical issues in Object-Oriented DBMSs. Extensible opt,imizers with efficient, search strategies require a cost model to select the most efficient execution plans. In this paper we propose and partially validate a generic cost-model for Object-Oriented DBMSs. The storage model and its access methods support clust,ered and nested collections, links, and path indexes. Queries may involve complex predicates with qualified path expressions. We propose a, method for estimating the number of block a,ccesses to clustered collections and a paramet,erized execution model for evaluating predicat,es. We estimate the costs of path expression traversals in different cases of physical clustering of the supporting collections. Thr model is validated through experiments with the 02 DBMS."
"Data warehouses are used to collect and analyze data from remote sources. The data collected often originate from transactional information and can become very large. This paper presents a framework for incrementally removing warehouse data (without a need to fully recompute offering two choices. One is to expunge data, in which case the result is as if the data had never existed. The second is to expire data, in which case views defined over the data are not necessarily affected. the framework, a user or administrator can specify what data to expire or expunge, what auxiliary data is to be kept for facilitating incremental view maintenance, what type of updates are expected from external sources, and how the system should compensate when data is expired or other parameters changed. We present algorithms for the various expiration and compensation actions, and we show how our framework can be implemented on top of a conventional RDBMS."
"Three topic areas relevant to the database community are identi ed. First is user-centered information analysis environments for correlation and manipulation of multimedia and complex information resources based on semantic content, visualizing complex and abstract information spaces, value-based ltering, and search, retrieval, and manipulation of multimedia and complex documents. Second is scalable, secure, and interoperable information repositories supporting a wide range of information resources and services. Issues to be addressed include: registration and security of information resources and services, access control and rights management, automatic classi cation and federation, and distributed service quality assurance facilities. Third is the intelligent integration of information."
"In this paper, we present and evaluate alternative techniques to effect the use of location-independent identifiers in distributed database systems. Location-independentidentifiers are important to take full advantage of migration and replication as they allow accessing objects without visiting the servers that created the objects. We will show how a distributed index structure can be used for this purpose, we will present a simple, yet effective replication strategy for the nodes of the index, and we will present alternative strategies to traverse the index in order to dereference identifiers (i.e., find a copy of an object given its identifier). Furthermore, we will discuss the results of performance experiments that show some tradeoffs of the proposed replication and traversal strategies and compare our techniques to an approach that uses locationdependent identifiers like many systems today"
We capture such queries in our definition of preference queries that use a weight function over a relation's attributes to derive a score for each tuple. Database systems cannot efficiently produce the top results of a preference query because they need to evaluate the weight function over all tuples of the relation. PREFER answers preference queries efficiently by using materialized views that have been pre-processed and stored.
"This is my first issue as associate editor of software reviews for The American Statistician. In this column, I will introduce myself, comment on the types of software reviews that can be published in this section of The American Statistician, and encourage others in the profession to consider taking on the task of reviewing statistical software packages."
"We have developed an XML repository management system, called Rainbow, designed to exploit relational database technology to manage XML da ta based on a flexible mapping strategy [2].As shown in Figure 1, the Rainbow system is composed of three sub-systems, e.g., a loading manager, a mapping manager, and an XML query engine build on top of a relational database. Rainbow first loads an XML Schema into the relational database via the loading query provided by the loading manager. Loading queries are expressed in XQuery. Then the mapping manager provides an extraction view query genera ted from the loading query."
"A major challenge still facing the designers and implementors of database programming languages (DBPLs) is that of query optimisation. In the paper we first give the syntax of our archetypal DBPL and briefly discuss its semantics. We then define a small but powerful algebra of operators over the set data type, provide some key equivalences for expressions in these operators, and list transformation principles for optimising expressions."
"This article gives methods for statically analyzing sets of active database rules to determine if the rules are (1) guaranteed to terminate, (2) guaranteed to produce a unique final database state, and (3) guaranteed to produce a unique stream of observable actions. If the analysis determines that one of these properties is not guaranteed, it isolates the rules responsible for the problem and determines criteria that, if satisfied, guarantee the property. The analysis methods are presented in the context of the Starburst Rule System"
"The ORES TDBMS will support the efficient and user friendly representation and manipulation of temporal knowledge and it will be developed as an extension of the relational database management system INGRES. The ORES project will result in a general purpose TDBMS, the development of which is based on a practical and yet theoretically sound approach. More specifically, the overall objectives of the ORES project are: i) to develop a formal foundation for temporal representation and reasoning, ii) to develop a temporal query language that will be upwards consistent with SQL2, iii) to develop models, techniques and tools for user friendly and effective definition, manipulation and validation of temporal database applications, and iv) to evaluate the ORES environment using a hospital case study"
"We report the finding of ""triply magic"" conditions (the doubly magic frequency-intensity conditions of an optical dipole trap plus the magic magnetic field) for the microwave transitions of optically trapped alkali-metal atoms. The differential light shift (DLS) induced by a degenerate two-photon process is adopted to compensate a DLS associated with the one-photon process. Thus, doubly magic conditions for the intensity and frequency of the optical trap beam can be found. Moreover, the DLS decouples from the magnetic field in a linearly polarized optical dipole trap, so that the magic condition of the magnetic field can be applied independently."
"Multimedia applications demand specific support from database management systems due to the characteristics of multimedia data and their interactive usage. This includes integrated support for high-volume and time-dependent (continuous) data types like audio and video. One critical issue is to provide handling of continuous data streams including buffer management as needed for multimedia presentations. Buffer management strategies for continuous data have to consider specific requirements like providing for continuity of presentations, for immediate continuation of presentations after frequent user interactions by appropriate buffer resource consumption. Existing buffer management strategies do not sufficiently support the handling of continuous data streams in highly interactive multimedia presentations."
"Hardware developments allow wonderful reliability and essentially limitless capabilities in storage, networks, memory, and processing power. Costs have dropped dramatically. PCs are becoming ubiquitous. The features and scalability of DBMS software have advanced to the point where most commercial systems can solve virtually all OLTP and DSS requirements. The Internet and application software packages allow rapid deployment and facilitate a broad range of solutions."
 In this paper we present a second enhancement: a single operator that lets the analyst get summarized reasons for drops or increases observed at an aggregated level. This eliminates the need to manually drill-down for such reasons. We develop an information theoretic formulation for expressing the reasons that is compact and easy to interpret. We design a dynamic programming algorithm that requires only one pass of the data improving significantly over our initial greedy algorithm that required multiple passes.
" This paper studies workfile disk management for concurrent mergesorts ina multiprocessor database system. Specifically, we examine the impacts of workfile disk allocation and data striping on the average mergesort response time. Concurrent mergesorts in a multiprocessor system can creat severe I/O interference in which a large number of sequential write requests are continuously issued to the same workfile disk and block other read requests for a long period of time. We examine through detailed simulations a logical partitioning approach to workfile disk management and evaluate the effectiveness of datastriping."
 The current paper outlines a number of important changes that face the database community and presents an agenda for how some of these challenges can be met. This database agenda is currently being addressed in the Enterprise Group at Microsoft Corporation. The paper concludes with a scenario for 2001 which reflects the Microsoft vision of ¡°Information at your fingertips.¡±
" With increasing global exposure, today's enterprises must react quickly to changes, rapidly develop new services and products, and at the same time improve productivity and quality and reduce cost. Business process re-engineering and workflow automation to coordinate activities throughout the enterprise are recognized as important emerging technologies to support these requirements. Rosy estimates of a multi-billion dollar marketplace for workflow software has resulted in significant commercial activities in the area, with nearly hundred products now claiming to support workflow automation. While many help to automate document- and image-driven office applications"
" After having grown briskly in the last several years, Internet services have not only entered the mainstream of society but also moved into areas where a plain best-effort service model is no longer adequate. This phenomenon is well illustrated by two major thrust areas: Electronic commerce where poor performance or unavailability could be very expensive, and streaming media services (including voice over IP) where quality of service is a fundamental requirement. These areas have brought to light a host of performance, availability and architectural issues that must be resolved effectively in order to prevent widespread customer dissatisfaction that could adversely affect the long-term growth of online services. In particular, the unresponsiveness and apparent failures of ecommerce servers, and consequent loss in revenue for ecommerce industry is well noted. Similarly, the difficulties in providing adequate quality of service have stunted the proliferation of streaming media services on the Internet."
"The problem of answering queries using views is to find efficient methods of answering a query using a set of previously materialized views over the database, rather than accessing the database relations. The problem has received significant attention because of its relevance to a wide variety of data management problems, such as data integration, query optimization, and the maintenance of physical data independence. To date, the performance of proposed algorithms has received very little attention, and in particular, their scale up in the presence of a large number of views is unknown. We first analyze two previous algorithms, the bucket algorithm and the inverse-rules, and show their deficiencies. We then describe the MiniCon, a novel algorithm for finding the maximally-contained rewriting of a conjunctive query using a set of conjunctive views. We present the first experimental study of algorithms for answering queries using views."
"When Alex Labrinidis asked me to write this essay, I initially balked. I was loathe to speak for academics worldwide, or even just those in SIGMOD. But I then realized that I could speak from personal experience. So these random musings will be of necessity entirely subjective, highly individualistic, and unrepresentative---attributes that a scholar normally attempts to vigorously avoid in his writing. I'm definitely not a ""typical"" academic (I don't know such an animal), but I can speak with some authority as to what motivates me.As another caveat, I make few comparisons with alternatives such as working in a research lab or as a developer. I won't even attempt to speak for them.The final caveat (distrust all commentaries that start with caveats, but perhaps more so those that don't!) is that my assumed audience comprises students who are considering such a profession. Current academics will find some of my observations trite or may disagree loudly, as academics are oft to do (see below).T"
"Set value attributes are a concise and natural way to model complex data sets. Modern Object Relational systems support set value attributes and allow various query capabilities on them. In this paper we initiate a formal study of indexing techniques for set value attributes based on similarity, for suitably deened notions of similarity between sets. Such techniques are necessary in modern applications such as recommendations through collaborative ltering and automated advertising. Our techniques are probabilistic and approximate in nature. As a design principle we create structures that make use of well known and widely used data structuring techniques, as a means to ease integration with existing infrastructure."
"Support vector machines (SVMs) have shown superb performance for text classification tasks. They are accurate, robust, and quick to apply to test instances. Their only potential drawback is their training time and memory requirement. For n training instances held in memory, the best-known SVM implementations take time proportional to na, where a is typically between 1.8 and 2.1. SVMs have been trained on data sets with several thousand instances, but Web directories today contain millions of instances that are valuable for mapping billions of Web pages into Yahoo!-like directories. We present SIMPL, a nearly linear-time classification algorithm that mimics the strengths of SVMs while avoiding the training bottleneck."
"Over the past decade, there has been a lot of work in developing middleware for integrating and automating enterprise business processes. Today, with the growth in e-commerce and the blurring of enterprise boundaries, there is renewed interest in business process coordination, especially for inter-organizational processes. This paper provides a historical perspective on technologies for intraand interenterprise business processes , reviews the state of the art, and exposes some open research issues. We include a discussion of process-based coordination and event/rule-based coordination, and corresponding products and standards activities. We provide an overview of the rather extensive work that has been done on advanced transaction models for business processes, and of the fledgling area of business process intelligence"
"In this paper, I will examine a field of science in which this is emphatically not the case ¡ª the field of biodiversity science. Crane¡¯s model works best in physics, where there is no assumption that information collected in the early nineteenth century will still be of interest to the current generation of field theorists. There is the assumption [6, for example] that new theories will reorder knowledge in the domain effectively and efficiently; and since Kuhn [5] most would accept that a major paradigm change in, say, the understanding of ¡®gravity¡¯ renders previous work on incline planes literally incommensurable ¡ª not to mention technical improvements making the older work too imprecise. Astronomers trawl back further in time, seeking traces of supernovae in ancient manuscripts ¡ª but sporadically; they are just as likely to look at monastery records as at Tycho Brahe¡¯s original data. Biodiversity information is fundamentally historical in three different ways."
"Many aspects of time-based media¡ªcomplex data encoding, compression, ¡°quality factors,¡± timing¡ªappear problematic from a data modeling standpoint. This paper proposes timed streams as the basic abstraction for modeling time-based media. Several media-independent structuring mechanisms are introduced and a data model is presented which, rather than leaving the interpretation of multimedia data to applications, addresses the complex organization and relationships present in multimedia."
"In the bottom-up evaluation of logic programs and recursively defined views on databases, all generated facts are usually assumed to be stored until the end of the evaluation. Discarding facts during the evaluation, however, can considerably improve the efficiency of the evaluation: the space needed to evaluate the program, the I/O costs, the costs of maintaining and accessing indices, and the cost of eliminating duplicates may all be reduced. Given an evaluation method that is sound, complete, and does not repeat derivation steps, we consider how facts can be discarded during the evaluation without compromising these properties. We show that every such space optimization method has certain components, the first to ensure soundness and completeness, the second to avoid redundancy (i.e., repetition of derivations), and the third to reduce ¡°fact lifetimes¡± (i.e., the time period for which each fact must be retained during evaluation). We present new techniques based on providing bounds on the number of derivations and uses of facts, and using monotonicity constraints for each of the first two components, and provide novel synchronization techniques for the third component of a space optimization method."
"Many societal applications, for example, in domains such as health care, land use, disaster management, and environmental monitoring, increasingly rely on geographical information for their decision making. With the emergence of the World WideWeb this information is typically located in multiple, distributed, diverse, and autonomously maintained systems. Therefore, strategic decision making in these societal applications relies on the ability to enrich the semantics associated to geographical information in order to support a wide variety of tasks including data integration, interoperability, knowledge reuse, knowledge acquisition, knowledge management, spatial reasoning, and many others."
"The present article will highlight, through an analysis of the media¡¯s treatment of the legislative reform process in Hong Kong, the political issues at stake in this ban, and in particular the grey areas of the public debate. It tries to break with the dichotomy ¡°for¡± or ¡°against¡± that are often typical of debates on the extinction of these emblematic mammals. In this press review I undertake a detailed analysis of local newspaper articles, essentially those of the English-language press. Of the 41 articles examined, I selected 21 on the basis of their relevance to legislative reform in Hong Kong and the diversity of their content. Two articles from the Chinese-language local press (selected from 28 articles), as well as six articles from the mainland¡¯s English-language press (selected from 47 articles) serve to underscore this analysis. These articles were published between 2015 and July 2018, that is, from the announcement of the reform until its initial implementation. This article will refer to the timeline of the reform with respect to several key moments and questions that require particular attention"
"This paper proposes and evaluate Prefetching B+-Trees (pB+-Trees), which use prefetching to accelerate two important operations on B+-Tree indices: searches and range scans. To accelerate searches, pB+-Trees use prefetching to effectively create wider nodes than the natural data transfer size: e.g., eight vs. one cache lines or disk pages. These wider nodes reduce the height of the B+-Tree, thereby decreasing the number of expensive misses when going from parent to child without significantly increasing the cost of fetching a given node. Our results show that this technique speeds up search and update times by a factor of 1.21-1.5 for main-memory B+-Trees. In addition, it outperforms and is complementary to ¡°Cache-Sensitive B+-Trees.¡± To accelerate range scans, pB+-Trees provide arrays of pointers to their leaf nodes. These allow the pB+-Tree to prefetch arbitrarily far ahead, even for nonclustered indices, thereby hiding the normally expensive cache misses associated with traversing the leaves within the range. Our results show that this technique yields over a sixfold speedup on range scans of 1000+ keys."
"We will share with readers some good news on NSF and Defense budget, and report on several interesting new programs at DARPA and NSF."
"A major challenge still facing the designers and implementors of database programming languages (DBPLs) is that of query optimisation. We investigate algebraic query optimisation techniques for DBPLs in the context of a purely declarative functional language that supports sets as first-class objects. Since the language is computationally complete issues such as non-termination of expressions and construction of infinite data structures can be investigated, whilst its declarative nature allows the issue of side effects to be avoided and a richer set of equivalences to be developed. The support of a set bulk data type enables much prior work on the optimisation of relational languages to be utilised. Finally, the language has a well-defined semantics which permits us to reason formally about the prop erties of expressions, such as their equivalence with other expressions and their termination"
"We present an optimization method and al gorithm designed for three objectives: physi cal data independence, semantic optimization, and generalized tableau minimization. The method relies on generalized forms of chase and ""backchase"" with constraints (dependen cies). By using dictionaries (finite functions) in physical schemas we can capture with con straints useful access structures such as indexes, materialized views, source capabilities, access support relations, gmaps, etc. The search space for query plans is defined and enumerated in a novel manner: the chase phase rewrites the original query into a ""universal"" plan that integrates all the access structures and alternative pathways that are allowed by appli cable constraints. Then, the backchase phase produces optimal plans by eliminating various combinations of redundancies, again according to constraints. This method is applicable (sound) to a large class of queries, physical access structures, and semantic constraints."
"Query processing in data integration occurs over network-bound, autonomous data sources. This requires extensions to traditional optimization and execution techniques for three reasons: there is an absence of quality statistics about the data, data transfer rates are unpredictable and bursty, and slow or unavailable data sources can often be replaced by overlapping or mirrored sources. This paper presents the Tukwila data integration system, designed to support adaptivity at its core using a two-pronged approach. Interleaved planning and execution with partial optimization allows Tukwila to quickly recover from decisions based on inaccurate estimates. During execution, Tukwila uses adaptive query operators such as the double pipelined hash join, which produces answers quickly, and the dynamic collector, which robustly and efficiently computes unions across overlapping data sources."
"The European Commission opens in its 7th IST call for proposals an action line for Semantic Web Technologies. It builds on ideas that have been looming for many years but have received their greatest push when the World Wide Web Consortium set up an interest group on that theme. The Semantic Web aims to make content machine understandable in order to automate a wide range of new tasks within the context of heterogeneous and distributed systems. The action line centres on four aspects: formalisation of the semantics, derivation of attributes, intelligent ltering and information visualisation. The Web is currently a mighty collection of ashy data but diAEcult to exploit. Adding semantics to content and ensuring their interoperability will turn it into an eAEcient knowledge source."
"Parallel implementations based on OpenMP or MapReduce also adopt the pruning policy and do not solve the problem thoroughly. In this context, taking into account features of document datasets, we propose 2Step-SSJ, which solves the document similarity self-join in CUDA environment on GPUs. 2Step-SSJ performs the similarity self-join in two steps, i.e., similarity computing on the inverted list and similarity computing on the forward list, which compromises between the memory visiting and dot-product computation. The experimental results show that 2Step-SSJ could solve the problem much faster than existing methods on three benchmark text corpora, achieving the speedup of 2x-23x against the state-of-the-art parallel algorithm in general, while keep a relatively stable running time with different values of the threshold."
"In this article, we first describe the XFilter and YFilter approaches and present results of a detailed performance comparison of structure matching for these algorithms as well as a hybrid approach. The results show that the path sharing employed by YFilter can provide order-of-magnitude performance benefits. We then propose two alternative techniques for extending YFilter's shared structure matching with support for value-based predicates, and compare the performance of these two techniques. The results of this latter study demonstrate some key differences between shared XML filtering and traditional database query processing. Finally, we describe how the YFilter approach is extended to handle more complicated queries containing nested path expressions"
"In this paper, we propose the first space-efficient algorithmic solution for estimating the cardinality of full-fledged set expressions over general update streams. Our estimation algorithms are probabilistic in nature and rely on a novel, hash-based synopsis data structure, termed ""2-level hash sketch. We demonstrate how our 2-level hash sketch synopses can be used to provide low-error, high-confidence estimates for the cardinality of set expressions (including operators such as set union, intersection, and difference) over continuous update streams, using only small space and small processing time per update. Furthermore, our estimators never require rescanning or resampling of past stream items, regardless of the number of deletions in the stream. We also present lower bounds for the problem, demonstrating that the space usage of our estimation algorithms is within small factors of the optimal. Preliminary experimental results verify the effectiveness of our approach"
"Many database applications make extensive use of bitmap indexing schemes. In this paper, we study how to improve the efficiencies of these indexing schemes by proposing new compression schemes for the bitmaps. Most compression schemes are designed primarily to achieve good compression. During query processing they can be orders of magnitude slower than their uncompressed counterparts. The new schemes are designed to bridge this performance gap by reducing compression effectiveness and improving operation speed."
"To reduce the storage costs, the sparse prefix sums technique exploits sparsity in the data and avoids to materialize prefix sums for empty rows and columns in the data grid; instead, look-up tables are used to preserve constant query time. Sparse prefix sums are the first approach to achieve O ( 1 ) query time with sub-linear storage costs for range-sum queries over sparse low-dimensional arrays. A thorough experimental evaluation shows that the approach works very well in practice. On the tested real-world data sets the storage costs are reduced by an order of magnitude with only a small overhead in query time, thus preserving microsecond-fast query answering"
"The Flexible Authorization Framework (FAF) defined by Jajodia et al. [2001] provides a policy-neutral framework for specifying access control policies that is expressive enough to specify many known access control policies. Although the original formulation of FAF indicated how rules could be added to or deleted from a FAF specification, it did not address the removal of access permissions from users. We present two options for removing permissions in FAF and provide details on the option which is representation independent"
"The Web is based on a browsing paradigm that makes it difficult to retrieve and integrate data from multiple sites. Today, the only way to achieve this integration is by building specialized applications, which are time-consuming to develop and difficult to maintain. We are addressing this problem by creating the technology and tools for rapidly constructing information mediators that extract, query, and integrate data from web sources. The resulting system, called Ariadne, makes it feasible to rapidly build information mediators that access existing web sources"
"In this article, we review pairwise spatial join algorithms and show how they can be combined for multiple inputs. In addition, we explore the application of synchronous traversal (ST), a methodology that processes synchronously all inputs without producing intermediate results. Then, we integrate the two approaches in an engine that includes ST and pairwise algorithms, using dynamic programming to determine the optimal execution plan. The results show that, in most cases, multiway spatial joins are best processed by combining ST with pairwise methods. Finally, we study the optimization of very large queries by employing randomized search algorithms."
"Users typically view the data as multidimensional data cubes. Each cell of the data cube is a view consisting of an aggregation of interest, like total sales. The values of many of these cells are dependent on the values of other cells in the data cube. A common and powerful query optimization technique is to materialize some or all of these cells rather than compute them from raw data each time. Commercial systems differ mainly in their approach to materializing the data cube. In this paper, we investigate the issue of which cells (views) to materialize when it is too expensive to materialize all views. A lattice framework is used to express dependencies among views. We present greedy algorithms that work off this lattice and determine a good set of views to materialize. The greedy algorithm performs within a small constant factor of optimal under a variety of models. We then consider the most common case of the hypercube lattice and examine the choice of materialized views for hypercubes in detail, giving some good tradeoffs between the space used and the average time to answer a query"
"SQL3, the name given to the new draft of the SQL standard that is likely to become an international s tandard replacing SQL92 in 1996 or 1997, contains several object-oriented extensions. When defining such extensions, X3H2 (the American Committee responsible for the specification of SQL3) and DBL (the International Committee for the same purpose) have had to make (and are still making) some of the same decisions made by the designers of other object-oriented languages. Among these decisions is the one described by Zdonik and Mater in. Zdonik and Mater observed that it is not possible to combine more than three of the following four features in a single language"
"In Sept. 1999 SQLJ Part 1 was adopted as NCITS 331.1-1999 and it is now available for purchase from NCITS. It is worth mentioning that this specification is extremely approachable, with a lengthy tutorial section that introduces its more normative elements. Sybase brought SQLJ Part 1 to the SQLJ group in early 1997. Phil Shaw, of Sybase, has acted as editor of this document throughout its development. SQLJ Part 1 allows Java classes, contained in Jar files, to be brought into a DBMS. Methods in these classes may then be used as the implementation of SQL stored procedures and stored functions (together referred to as stored routines). Given how these methods are used, we¡¯ll provide a brief introduction to SQL routines before we discuss the features of SQLJ Part 1."
"We study a set of linear transformations on the Fourier series representation of a sequence that can be used as the basis for similarity queries on time-series data. We show that our set of transformations is rich enough to formulate operations such as moving average and time warping. We present a query processing algorithm that uses the underlying R-tree index of a multidimensional data set to answer similarity queries efficiently. Our experiments show that the performance of this algorithm is competitive to that of processing ordinary (exact match) queries using the index, and much faster than sequential scanning. We relate our transformations to the general framework for similarity queries of Jagadish et al"
"We have developed a web-based architecture and user interface for fast storage, searching and retrieval of large, distributed, files resulting from scientific simulations. We demonstrate that the new DATALINK type defined in the draft SQL Management of External Data Standard can help to overcome problems associated with limited bandwidth when trying to archive large files using the web. We also show that separating the user interface specification from the user interface processing can provide a number of advantages. We provide a tool to generate automatically a default user interface specification, in the form of an XML document, for a given database. This facilitates deployment of our system by users with little web or database development experience. The XML document can be customised to change the appearance of the interface"
"Web-based data sources, particularly in Life Sciences, grow in diversity and volume. Most of the data collections are equipped with common document search, hyperlink and retrieval utilities. However, users' wishes often exceed simple document-oriented inquiries. With respect to complex scientific issues it becomes imperative to aid knowledge gain from huge interdependent and thus hard to comprehend data collections more efficiently. Especially data categories that constitute relationships between two each or more items require potent set-oriented content management, visualization and navigation utilities. Moreover, strategies are needed to discover correlations within and between data sets of independent origin."
"The use of social media in advocacy, and particularly transnational advocacy, raises concerns of privacy and security for those conducting the advocacy and their contacts on social media. This chapter presents high-level summaries of cases of social media in advocacy and activism from the perspectives of information warfare and information security. From an analysis of these, the impact and relationships of social media in transnational advocacy and information security is discussed. Whilst online advocacy can be considered to be a form of information warfare aligned to a Cyber Macht theory, it can be argued that social media advocacy negatively impacts information security as it encourages various actors to actively attempt to breach security."
"In a temporal OODB, an OID index (OIDX) is needed to map from OID to the physical location of the object. In a transaction time temporal OODB, the OIDX should also index the object versions. In this case, the index entries, which we call object descriptors (OD), also include the commit timestamp of the transaction that created the object version. The OIDX in a non-temporal OODB only needs to be updated when an object is created, but in a temporal OODB, the OIDX has to be updated every time an object is updated. This has previously been shown to be a potential bottleneck, and in this paper, we present the Persistent Cache (PCache), a novel approach which reduces the index update and lookup costs in temporal OODBs."
"We examine the estimation of selectivities for range and spatial join queries in real spatial databases. As we have shown earlier, real point sets: (a) violate consistently the ¡°uniformity¡± and ¡°independence¡± assumptions, (b) can often be described as ¡°fractals¡±, with non-integer (fractal) dimension. In this paper we show that, among the infinite family of fractal dimensions, the so called ¡°Correlation Dimension¡± Dz is the one that we need to predict the selectivity of spatial join. The main contribution is that, for all the real and synthetic point-sets we tried, the average number of neighbors for a given point of the point-set follows a power law, with LI& as the exponent. This immediately solves the selectivity estimation for spatial joins, as well as for ¡°biased¡± range queries (i.e., queries whose centers prefer areas of high point density)."
"A key aspect of interoperation among data-intensive systems involves the mediation of metadata and ontologies across database boundaries. One way to achieve such mediation between a local database and a remote database is to fold remote metadata into the local metadata, thereby creating a common platform through which information sharing and exchange becomes possible. Schema implantation and semantic evolution, our approach to the metadata folding problem, is a partial database integration scheme in which remote and local (meta)data are integrated in a stepwise manner over time."
"In this paper, a new probe-based distributed deadlock detection algorithm is proposed. It is an enhanced version of the algorithm originally proposed by Chandy's et al.. The new algorithm has proven to be error free and suffers very little performance degradation from the additional deadlock detection overhead. The algorithm has been compared with the modified probe-based and timeout methods. It is found that under high data contention, it has the best performance. Results also indicate that the rate of probe initiation is significantly reduced in the new algorithm"
"In late 2000, work was completed on yet another part of the SQL standard, to which we introduced our readers in an earlier edition of this column.Although SQL database systems manage an enormous amount of data, it certainly has no monopoly on that task. Tremendous amounts of data remain in ordinary operating system files, in network and hierarchical databases, and in other repositories. The need to query and manipulate that data alongside SQL data continues to grow. Database system vendors have developed many approaches to providing such integrated access.In this (partly guested) article, SQL's new part, Management of External Data (SQL/MED), is explored to give readers a better notion of just how applications can use standard SQL to concurrently access their SQL data and their non-SQL data."
"An order-dependent query is one whose result (interpreted as a multiset) changes if the order of the input records is changed. In a stock-quotes database, for instance, retrieving all quotes concerning a given stock for a given day does not depend on order, because the collection of quotes does not depend on order. By contrast, finding a stock's five-price moving-average in a trades table gives a result that depends on the order of the table. Query languages based on the relational data model can handle order-dependent queries only through add-ons. SQL:1999, for instance, has a new ""window"" mechanism which can sort data in limited parts of a query. Add-ons make order-dependent queries di_cult to write and to optimize. In this paper we show that order can be a natural property of the underlying data model and algebra. We introduce a new query language and algebra, called AQuery, that supports order from-the-ground-up. New order-related query transformations arise in this setting. We show by experiment that this framework - language plus optimization techniques - brings orders-of-magnitude improvement over SQL:1999 systems on many natural order-dependent queries"
"The enhanced pay-per-view (EPPV) model for providing continuous-media-on-demand (CMOD) services associates with each continuous media clip a display frequency that depends on the clip¡¯s popularity. The aim is to increase the number of clients that can be serviced concurrently beyond the capacity limitations of available resources, while guaranteeing a constraint on the response time. This is achieved by sharing periodic continuous media streams among multiple clients. In this paper, we provide a comprehensive study of the resource scheduling problems associated with supporting EPPV for continuous media clips with (possibly) different display rates, frequencies, and lengths. Our main objective is to maximize the amount of disk bandwidth that is effectively scheduled under the given data layout and storage constraints. This formulation gives rise to -hard combinatorial optimization problems that fall within the realm of hard real-time scheduling theory. Given the intractability of the problems, we propose novel heuristic solutions with polynomial-time complexity. Preliminary results from an experimental evaluation of the proposed schemes are also presented."
"Real-time Virtual Walkthrough Data representing virtual environments (VEs) are getting increasingly large in order to better simulate real scenes. This poses interesting challenges to organize, store, and render the data for interactive navigation in VEs, or walkthrough. A large VE usually consists of thousands of 3D objects, each of which can be represented by hundreds of polygons, and may take thousands of megabytes of storage space. The amount of data is so large that it is impossible to store all of them in the main memory. Even for memory resident models, the graphics pipeline can become a bottleneck quickly with a large amount of data and slow down the rendering to an unacceptable frame rate for the walkthrough."
"The random data perturbation (RDP) method of preserving the privacy of individual records in a statistical database is discussed. In particular, it is shown that if confidential attributes are allowed as query-defining variables, severe biases may result in responses to queries. It is also shown that even if query definition through confidential variables is not allowed, biases can still occur in responses to queries such as those involving proportions or counts. In either case, serious distortions may occur in user statistical analyses. A modified version of RDP is presented, in the form of a query adjustment procedure and specialized perturbation structure which will produce unbiased results."
"The Web today consists exclusively of HTML documents designed for the human eye. While many of them are generated automatically by applications, it is difficult for other applbcations to read and process them. This may soon change, due to a series of new standards frorn the World Wide Web Consortium centered around XML (Extensible Markup Language). XML is designed to express the document content, while HTML expresses its presentation. In short, XML is a data exchange format, easily understood by applications. It enables data exchange on the Web, both intra-enterprise, across platforms (intranet), and inter-enterprise (internet). The focus of the Web shifts from document management to data management, and topics like queries, views, data warehouses, mediators, which were the domain of databases, become of interest to the Web."
"Loading data is one of the most critical operations in any data warehouse, yet it is also the most neglected by the database vendors. Data must be loaded into a warehouse in a fixed batch window, typically overnight. During this period, we need to take maximum advantage of the machine resources to load data as efficiently as possible. A data warehouse can be on line for up to 20 hours of a day, which can leave only a window of 4 hours to complete the load. The Red Brick loader can validate, load and index at up to 12GB of data per hour on an SMP system."
"One of the main difficulties in supporting global applications over a number of localized databases and migrating legacy information systems to modern computing environment is to cope with the heterogeneities of these systems. In this paper, we present a novel flexible architecture (called HODFA) to dynamically connect such localized heterogeneous databases in forming a homogenized federated database system and to support the process of transforming a collection of heterogeneous information systems onto a homogeneous environment. We further develop an incremental methodology of homogenization in the context of our HODFA framework, which can facilitate different degrees of homogenization in a stepwise manner, so that existing applications will not be affected during the process of homogenization"
"As our reliance on computers and computerized data has increased, we have come to expect more from our computers. We no longer expect our computers to act as large expensive calculators that merely spit out bills and paychecks. We now, additionally, expect our systems to rapidly access and interactively present us with large volumes of accurate data. In fact, our expectations have changed so much, in the past decade, that we no longer focus on what our systems are but rather on what they do. We no longer refer to our systems as computer systems but rather information systems. With these new expectations have come new responsibilities for the information systems professional. We can no longer concern ourselves merely with keeping our systems up and running. We now need to concern ourselves with subjective concepts such as response time and throughput. With current expectations what they are, performance tuning has become vitally important."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues"
"An electronic dictionary system (EDS) is developed with object-oriented database techniques based on ObjectStore. The EDS is composed of two parts: the Database Building Program (DBP), and the Database Querying Program (DQP). DBP reads in a dictionary encoded in SGML tags, and builds a database composed of a collection of trees which holds dictionary entries, and several lists which contain items of various lexical categories. With text exchangeability introduced by the SGML, DBP is able to accommodate dictionaries of different languages with different structures, after easy modification of a configuration file. The tree model, the Category Lists, and an optimization procedure enables DQP to quickly accomplish complicated queries, including context requirements, via simple SQL-like syntax and straightforward search methods. Results show that compared with relational database, DQP enjoys much higher speed and flexibility."
"This Tutorial presents the latest developments in the area of Java and Relational Databases. The material is based on the SQLJ consortium effort whose goal is to leverage Java technology for SQL processing. The SQLJ effort is driven by major industry vendors such as Oracle, Sybase, Tandem, JavaSoft, IBM, Informix and others. The SQLJ specifications describe Embedded SQL in Java, Java Stored Procedures, Java UDFs and Java Data Types."
"In this paper, we ask if the traditional relational query acceleration techniques of summary tables and covering indexes have analogs for branching path expression queries over tree- or graph-structured XML data. Our answer is yes --- the forward-and-backward index already proposed in the literature can be viewed as a structure analogous to a summary table or covering index. We also show that it is the smallest such index that covers all branching path expression queries. While this index is very general, our experiments show that it can be so large in practice as to offer little performance improvement over evaluating queries directly on the data."
"One important step in integrating heterogeneous databases is matching equivalent attributes: Determining which fields in two databases refer to the same data. In semantic integration, attributes are compared in a pairwise fashion to determine their equivalence. Automation is critical to integration as the volume of data or the number of databases to be integrated increase. Semiut ¡°discovers¡± how to match equivalent attributes from information that can be automatically extracted from databases; as opposed to requiring human lmowledge to predefine what makes attributes equivalent."
"This article serves three purposes. First of all, to introduce dbjobs, the database of database jobs, and also describe its functionality and architecture. Secondly, to present statistics for the dbgrads system, after 18 months of continuous operation. Finally, to describe exciting future projects for SIGMOD Online."
"The experimental results show that distributed commit processing can have considerably more influence than distributed data processing on the throughput performance and that the choice of commit protocol clearly affects the magnitude of this influence. Among the protocols evaluated, the new optimistic commit protocol provides the best transaction throughput performance for a variety of workloads and system configurations. In fact, OPT's peak throughput is often close to the upper bound on achievable performance. Even more interestingly, a three-phase (i.e., non-blocking) version of OPT provides better peak throughput performance than all of the standard two-phase (i.e., blocking protocols evaluated in our study"
Several negative results are proved about the ability to type-check queries in the only existing proposed standard for object-oriented databases. The first of these negative results is that it is not possible to type-check OQL queries in the type system underlying the ODMG object model and its definition language ODL. The second negative result is that OQL queries cannot be type-checked in the type system of the Java binding of the ODMG standard either. A solution proposed in this paper is to extend the ODMG object model with explicit support for parametric polymorphism (universal type quantification). These results show that Java cannot be a viable database programming language unless extended with parametric polymorphism.
"In the rnid-1980s. Chrts Dare¡¯s ¡°12 rules¡± for distributed database systems included replication. Repi ication makes transparent the problems of remote access de]dys and the management of data redundancy. The commercial market for distributed database features has been slowly building over the years. beginning with simple remote access gateways. Today. replication appears to dehver on the 1980s ideal, with a robust a-wrrchrcmuus infrasrntctnre. Current commercial tmhnology though. continues to fall shotl of that ideal."
"e is no longer among us. The Italian Surgical Community has lost one of its best sons, because of this tragedy that is hitting our civilized world. A world-renowned surgeon, Prof. Valerio Di Carlo started his career in the Emergency Surgery Department of the Policlinico in Milan under the mentorship of Prof. Vittorio Staudacher. In 1978, he became Professor of Surgery at the Vita-Salute University of San Raffaele and was responsible for the General Surgery Department from 1980 to 2010."
"Query optimization which is done by making a graph of the query and moving predicates around in the graph so that they will be applied early in the optimized query generated from the graph. Predicates are first propagated up from child nodes of the graph to parent nodes and then down into different child nodes. After the predicates have been moved, redundant predicates are detected and removed. Predicates are moved through aggregation operations and new predicates are deduced from aggregation operations and from functional dependencies. The optimization is not dependent on join order and works where nodes of the graph cannot be merged."
"The Strudel system applies concepts from database management systems to the process of building Web sites. Strudel's key idea is separating the management of the site's data, the creation and management of the site's structure, and the visual presentation of the site's pages. First, the site builder creates a uniform model of all data available at the site. Second, the builder uses this model to declaratively define the Web site's structure by applying a ¡°site-definition query¡± to the underlying data. The result of evaluating this query is a ¡°site graph¡±, which represents both the site's content and structure. Third, the builder specifies the visual presentation of pages in Strudel's HTML-template language. The data model underlying Strudel is a semi-structured model of labeled directed graphs. We describe Strudel's key characteristics, report on our experiences using Strudel, and present the technical problems that arose from our experience."
"Time-referenced data are pervasive in most real-world databases. Recent advances in temporal query languages show that such database applications may benefit substantially from built-in temporal support in the DBMS. To achieve this, temporal query optimization and evaluation mechanisms must be provided, either within the DBMS proper or as a source level translation from temporal queries to conventional SQL. This paper proposes a new approach: using a middleware component on top of a conventional DBMS. This component accepts temporal SQL statements and produces a corresponding query plan consisting of algebraic as well as regular SQL parts. The algebraic parts are processed by the middleware, while the SQL parts are processed by the DBMS. The middleware uses performance feedback from the DBMS to adapt its partitioning of subsequent queries into middleware and DBMS parts. The paper describes the architecture and implementation of the temporal middleware component, termed TANGO, which is based on the Volcano extensible query optimizer and the XXL query processing library."
"BIRCH incrementally and dynamically clusters incoming multi-dimensional metric data points to try to produce the best quality clustering with the available resources (i.e., available memory and time constraints). BIRCH can typically find a good clustering with a single scan of the data, and improve the quality further with a few additional scans. BIRCH is also the first clustering algorithm proposed in the database area to handle ""noise"" (data points that are not part of the underlying pattern) effectively."
"Time-parameterized queries (TP queries for short) retrieve (i) the actual result at the time that the query is issued, (ii) the validity period of the result given the current motion of the query and the database objects, and (iii) the change that causes the expiration of the result. Due to the highly dynamic nature of several spatio-temporal applications, TP queries are important both as standalone methods, as well as building blocks of more complex operations. However, little work has been done towards their efficient processing. In this paper, we propose a general framework that covers time-parameterized variations of the most common spatial queries, namely window queries, k-nearest neighbors and spatial joins. In particular, each of these TP queries is reduced to nearest neighbor search where the distance functions are defined according to the query type. This reduction allows the application and extension of well-known branch and bound techniques to the current problem."
"One of the important problems in data mining is discovering association rules from databases of transactions where each transaction consists of a set of items. The most time consuming operation in this discovery process is the computation of the frequency of the occurrences of interesting subset of items (called candidates) in the database of transactions. To prune the exponentially large space of candidates, most existing algorithms, consider only those candidates that have a user defined minimum support. Even with the pruning, the task of finding all association rules requires a lot of computation power and time. Parallel computers offer a potential solution to the computation requirement of this task, provided efficient and scalable parallel algorithms can be designed. In this paper, we present two new parallel algorithms for mining association rules."
Rules in active database systems can be very difficult to program due to the unstructured and unpredictable nature of rule processing. We provide static analysis techniques for predicting whether a given rule set is guaranteed to terminate and whether rule execution is confluent (guaranteed to have a unique final state). Our methods are based on previous techniques for analyzing rules in active database systems. We improve considerably on the previous techniques by providing analysis criteria that are much less conservative: our methods often determine that a rule set will terminate or is confluent when previous methods could not make this determination.
"This paper presents the parallel enhancements which allowed the port of the Teradata Database from TOS, a proprietary ldbit Operating System, to an SVR4 Unix system. It gives an architectural overview of how the Teradata Database solves the main VLDB problems: performance and reliability. We will present he transition from the Database Computer DBC/lOlZ nodes (Interface Processors-IFPs and Access Module Processors AMPS) to the virtual processors (vprocs), which run concurrently in, a collection of SMP nodes. We also present the Parallel Database Environment (PDE) add-on package to Unix that makes this possible. We will discuss the results of our performance enhancement work and the directions for the future"
"Dwarf is a highly compressed structure for computing, storing, and querying data cubes. Dwarf identifies prefix and suffix structural redundancies and factors them out by coalescing their store. Prefix redundancy is high on dense areas of cubes but suffix redundancy is significantly higher for sparse areas. Putting the two together fuses the exponential sizes of high dimensional full cubes into a dramatically condensed data structure. The elimination of suffix redundancy has an equally dramatic reduction in the computation of the cube because recomputation of the redundant suffixes is avoided"
"Imagine that you are a ¡°knowledge worker¡± in the coming millenium. That means you must synthesize information and make decisions such as ¡°Which benefits plan to use?¡± ¡°What do the regulations say about this course of action?¡± ¡°How does my job fit into the corporate business plan?¡± ¡°What should I be careful about when I approach this client?¡± or even ¡°HOW does this program work?¡± If the dream of digital libraries is to bring you all material relevant to your task, you may find yourself drowning before long. Reading is harder than talking to people who know the relevant documents and can tell you what you¡¯re interested in. That is what many current knowledge workers do, giving rise to professions such as insurance consultant, lawyer, benefits specialist, and so on. Imagine by contrast that the documents you retrieve could be tailored precisely to your needs. That is, imagine that the document might ask you questions and produce a document filtered and organized according to those you have answered."
"In this paper, we present an efficient method to do online reorganization of sparsely-populated B+-trees. It reorganizes the leaves first, compacting in short operations groups of leaves with the same parent. After compacting, optionally, the new leaves may swap locations or be moved into empty pages so that they are in key order on the disk. After the leaves are reorganized, the method shrinks the tree by making a copy of the upper part of the tree while leaving the leaves in place. A new concurrency method is introduced so that only a minimum number of pages are locked during reorganization. During leaf reorganization, Forward Recovery is used to save all work already done while maintaining consistency after system crashes. A heuristic algorithm is developed to reduce the number of swaps needed during leaf reorganization, so that better concurrency and easier recovery can be achieved. A detailed description of switching from the old B+-tree to the new B+-tree is described for the first time."
"In this paper, we investigate which problems exist in very large real databases and describe which mechanisms are provided by Informix Extended Parallel Server (XPS) for dealing with these problems. Currently the largest customer XPS database contains 27 TB of data. A database server that has to handle such an amount of data has to provide mechanisms which allow achieving adequate performance and easing the usability. We will present mechanisms which address both of these issues and illustrate them with examples from real customer systems."
"In existing relational database systems, processing of group-by and computation of aggregate functions are always postponed until all joins are performed. In this paper, we present transformations that make it possible to push group-by operation past one or more joins and can potentially reduce the cost of processing a query significantly. Therefore, the placement of group-by should be decided based on cost estimation. We explain how the traditional System-R style optimizers can be modified by incorporating the greedy conservative heuristic that we developed. We prove that applications of greedy conservative heuristic produce plans that are better (or no worse) than the plans generated by a traditional optimizer. Our experimental study shows that the extent of improvement in the quality of plans is significant with only a modest increase in optimization cost. Our technique also applies to optimization of Select Distinct queries by pushing down duplicate elimination in a cost-based fashion."
"We describe SCC-kS, a Speculative Concurrency Control (SCC) algorithm that allows a DBMS to use efficiently the extra computing resources available in the system to increase the likelihood of timely commitment of transactions. Using SCC-kS, up to k shadow transactions execute speculatively in behalf of a given uncommitted transaction so as to protect against the hazards of blockages and resterts. SCC-kS allows the system to scale the level of speculation that each transaction is allowed to perform, thus providing a straightforward mechanism of trading resources for timeliness. Also, we describe SCC-DC, a value-cognizant SCC protocol that utilizes deadline and criticalness information to improve timeliness through the controlled deferment of transaction commitments. We present simulation results that quantify the performance gains of our protocols compared to other widely used concurrency control protocols for real-time databases."
"Data Mining: Practical Machine Learning Tools and Techniques offers a thorough grounding in machine learning concepts as well as practical advice on applying machine learning tools and techniques in real-world data mining situations. This highly anticipated third edition of the most acclaimed work on data mining and machine learning will teach you everything you need to know about preparing inputs, interpreting outputs, evaluating results, and the algorithmic methods at the heart of successful data mining. Thorough updates reflect the technical changes and modernizations that have taken place in the field since the last edition, including new material on Data Transformations, Ensemble Learning, Massive Data Sets, Multi-instance Learning, plus a new version of the popular Weka machine learning software developed by the authors."
"The Eighth International Workshop on Knowledge Representation Meets Databases (KRDB) was held at the Ponti cia Universit a Urbaniana, in Rome, right after VLDB 2001. KRDB was initiated in 1994 to provide an opportunity for researchers and practitioners from the two areas to exchange ideas and results. This year's focus was on Modeling, Querying andManaging Semistructured Data. The one day program included ten research papers, one invited talk, and a panel. Eight of the accepted papers addressed various topics related to representation of information and reasoning in XML, one was on data integration and one on transaction processing."
"Document sources are available everywhere, both within the internal networks of organizations and on the Internet. Even individual organizations use search engines from different vendors to index their internal document collections. These search engines are typically incompatible in that they support different query models and interfaces, they do not return enough information with the query results for adequate merging of the results, and finally, in that they do not export metadata about the collections that they index (e.g., to assist in resource discovery). This paper describes STARTS, an emerging protocol for Internet retrieval and search that facilitates the task of querying multiple document sources. STARTS has been developed in a unique way. It is not a standard, but a group effort coordinated by Stanford's Digital Library project, and involving over 11 companies and organizations. The objective of this paper is not only to give an overview of the STARTS protocol proposal, but also to discuss the process that led to its definition"
"To avoid this problem, we introduce a new organization of the directory which uses a split algorithm minimizing overlap and additionally utilizes the concept of supernodes. The basic idea of overlap-minimizing split and supernodes is to keep the directory as hierarchical as possible, and at the same time to avoid splits in the directory that would result in high overlap"
"The duplicate elimination problem of detecting multiple tuples, which describe the same real world entity, is an important data cleaning problem. Previous domain independent solutions to this problem relied on standard textual similarity functions (e.g., edit distance, cosine metric) between multi-attribute tuples. However, such approaches result in large numbers of false positives if we want to identify domain-specific abbreviations and conventions. In this paper, we develop an algorithm for eliminating duplicates in dimensional tables in a data warehouse, which are usually associated with hierarchies. We exploit hierarchies to develop a high quality, scalable duplicate elimination algorithm, and evaluate it on real datasets from an operational data warehouse."
"This chapter discusses how to manage one's personal databases or database striptease. The database management problem has been entering everyone's life. To realize its presence it suffices to sit down and tally the electronic data sources crucial for survival in the modern society. As long as data sources are independent, devices are never replaced, nor do new devices enter the realm of existence, it will survive easily in the digital jungle. However, life runs a different course. Each time one meets a new person, one may have to synchronize several databases with his address information. The limitations of the human brain to cope with the information overload calls upon better support to ¡°remember¡± where, what and when has been accumulated in the fabric of data sources making up the environment. Buying a new PDA surely means a re-organization and possibly retyping the content of the database."
"Today's Internet based businesses need a level of interoperability which will allow trading partners to seamlessly and dynamically come together and do business without ad hoc and proprietary integrations. Such a level of interoperability involves being able to find potential business partners, discovering their services and business processes, and conducting business ""on the fly"". This process of dynamic interoperation is only possible through standard B2B frameworks. Indeed a number of B2B electronic commerce standard frameworks have emerged recently. Although most of these standards are overlapping and competing, each with its own strenghts and weeknesses, a closer investigation reveals that they can be used in a manner to complement one another.In this paper we describe such an implementation where an ebXML infrastructure is developed by exploiting the Universal Description, Discovery and Integration (UDDI) registries and RosettaNet Partner Interface Processes (PIPs)."
"Although research on temporal database systems has been active for about 20 years, implementations have not appeared until recently. This is one reason why current commercial database systems provide only limited temporal functionality. This paper summarizes extant state of the art of temporal database implementations. Rather than being very specific about each system we have attempted to provide an indication of the functionality together with pointers to additional information. It is hoped that this leads to more efforts pushing the implementation of temporal database systems in the near future."
Query answers are ranked using extended information-retrieval techniques and are generated in an order similar to the ranking. Advanced indexing techniques were developed to facilitate efficient implementation of XSEarch. The performance of the different techniques as well as the recall and the precision were measured experimentally.
"In this paper, we present OPOSSUM, a flexible, customizable, and extensible schema management system. Working within the established paradigm of schema editing through direct manipulation, OPOSSUM employs several novel techniques to offer the following capabilities: enhancement of schema visualizations with user-specific information; exploration of schemas through choice of visual representations; and creation of new visual representation styles when existing ones prove unsatisfactory. We discuss the architecture of the system and the methodology that guided its development, and illustrate its most important features through examples of how it has been used. OPOSSUM is operational and is in use by three groups of experimental scientists on the University of Wisconsin campus as a tool for experiment and database design."
"Processes are increasingly being used to make complex application logic explicit. Programming using processes has significant advantages but it poses a difficult problem from the system point of view in that the interactions between processes cannot be controlled using conventional techniques. In terms of recovery, the steps of a process are different from operations within a transaction. Each one has its own termination semantics and there are dependencies among the different steps. Regarding concurrency control, the flow of control of a process is more complex than in a flat transaction. A process may, for example, partially roll back its execution or may follow one of several alternatives. In this article, we deal with the problem of atomicity and isolation in the context of processes. We propose a unified model for concurrency control and recovery for processes and show how this model can be implemented in practice, thereby providing a complete framework for developing middleware applications using processes."
"Recovery can be extended to new domains at reduced logging cost by exploiting ¡°logical¡± log operations. During recovery, a logical log operation may read data values from any recoverable object, not solely from values on the log or from the updated object. Hence, we needn't log these values, a substantial saving. In [8], we developed a redo recovery theory that deals with general log operations and proved that the stable database remains recoverable when it is explained in terms of an installation graph. This graph was used to derived a write graph that determines a flush order for cached objects that ensures that the database remains recoverable. In this paper, we introduce a refined write graph that permits more flexible cache management that flushes smaller sets of objects."
"The project focuses on the field of Technical Information Systems, where there is a need for tools supporting modeling of complex objects. Designers in this field usually use incremental design or step by step prototyping, because this seems to be best suited for users coping with complexity and uncertainty about their own needs or requirements. The IMPRESS DDT aims at supporting the database design part of this process."
"Recent demands for querying big data have revealed various shortcomings of traditional database systems. This, in turn, has led to the emergency of a new kind of query mode, approximate query.Online aggregation is a sample-based technology for approximate querying. It becomes quite indispensable in the era of information explosion today. Online aggregation continuously gives an approximate result with some error estimation (usually confidence interval) until all data are processed."
"Our results show that the policies are effective at achieving user-specified levels of I/O operations and database garbage percentage. We also investigate the sensitivity of the policies over a range of object connectivities. The evaluation demonstrates that semi-automatic, self-adaptive policies are a practical means for flexibly controlling garbage collection rate."
A single pass computing and visualization engine will be demonstrated that allows one to interactively analyze VLDBs that contain tens of millions of multivariate records. The engine allows one to compute millions of different quantities from a single pass over the records. Each computation can be performed for the entire multivariate domain and for all subdomains that can be obtained by constraining one or more discrete variables to span any subset of their values and one or more continuous variables to span any subset of their predefined bins. Each new computation takes less than one second irrespective of the number of records.
"Specifically, we use state-of-the-art concepts from morphology, n;,mely the ¡®pattern spectrum¡¯ of a shape, to map each shape to a point in n-dimensional space. FollowingThis text is a guide to the foundations of method engineering, a developing field concerned with the definition of techniques for designing software systems. The approach is based on metamodeling, the construction of a model about a collection of other models. The book applies the metamodeling approach in five case studies, each describing a solution to a problem in a specific domain. Suitable for classroom use, the book is also useful as a reference for practitioners. The book first presents the theoretical basis of metamodeling for method engineering, discussing information modeling, the potential of metamodeling for software systems development, and the introduction of the metamodeling tool ConceptBase. , we organize the n-d points in an R-tree. We show that the L, (= max) norm in the n-d space lower-bounds the actual distance. This guarantees no false dismissals for range queries. In addition, we present a nearest neighbor algorithm that also guarantees no false dismissals."
"This text is a guide to the foundations of method engineering, a developing field concerned with the definition of techniques for designing software systems. The approach is based on metamodeling, the construction of a model about a collection of other models. The book applies the metamodeling approach in five case studies, each describing a solution to a problem in a specific domain. Suitable for classroom use, the book is also useful as a reference for practitioners. The book first presents the theoretical basis of metamodeling for method engineering, discussing information modeling, the potential of metamodeling for software systems development, and the introduction of the metamodeling tool ConceptBase."
"Camps rightly focuses on certain important facets of the evolution of relational theory since 1969, in particular our ideas about what our revered originator, E.F. Codd, chose to call doma/ns. Camps's tone at times suggests that we (in the relational camp) have been guilty of waging war over issues on which we have subsequently recanted, too late. I think this is an exaggeration, and that we could make a reasonable counter-claim to the effect that all of the clarifications we have been able to suggest, after very careful study, over those many years, are compatible with what we said before. I would not strongly object if Camps retorted that that, too, is something of an exaggeration, but obviously I think my way of expressing it is closer to the troth"
"This paper describes the external forces that motivate financial institutions to collect, aggregate, analyze, and mine data so that it can be transformed into information, one of a financial institution¡¯s most valuable assets. In this paper we refer to this strategic information asset as ¡°information currency.¡± In general, we describe the state of banking and the rapid global changes that affect financial institutions. We analyze how Bank of America (BofA) created and employed its information currency using the TeradataTM Relational Database Management System (Teradata RDBMS). The Teradata RDBMS manages a very large data warehouse (NCR Scalable Data Warehouse) for BofA using an NCR WorldMarkTM 51OOM MPP (Massive Parallel Processing) platform."
"Tree patterns form a natural basis to query tree-structured data such as XML and LDAP. To improve the efficiency of tree pattern matching, it is essential to quickly identify and eliminate redundant nodes in the pattern. In this paper, we study tree pattern minimization both in the absence and in the presence of integrity constraints (ICs) on the underlying tree-structured database. In the absence of ICs, we develop a polynomial-time query minimization algorithm called CIM, whose efficiency stems from two key properties: (i) a node cannot be redundant unless its children are; and (ii) the order of elimination of redundant nodes is immaterial. When ICs are considered for minimization, we develop a technique for query minimization based on three fundamental operations: augmentation (an adaptation of the well-known chase procedure), minimization (based on homomorphism techniques), and reduction. We show the surprising result that the algorithm, referred to as ACIM, obtained by first augmenting the tree pattern using ICs, and then applying CIM, always finds the unique minimal equivalent query. While ACIM is polynomial time, it can be expensive in practice because of its inherent non-locality. We then present a fast algorithm, CDM, that identifies and eliminates local redundancies due to ICs, based on propagating ¡±information labels¡± up the tree pattern. CDM can be applied prior to ACIM for improving the minimization efficiency. We complement our analytical results with an experimental study that shows the effectiveness of our tree pattern minimization techniques."
"For reasons of simplicity and communication efficiency, a number of existing object-oriented database management systems are based on page server architectures; data pages are their minimum unit of transfer and client caching. Despite their efficiency, page servers are often criticized as being too restrictive when it comes to concurrency, as existing systems use pages as the minimum locking unit as well. In this paper we show how to support object-level locking in a page server context. Several approaches are described, including an adaptive granularity approach that uses page-level locking for most pages but switches to object-level locking when finer-grained sharing is demanded. We study the performance of these approaches, comparing them to both a pure page server and a pure object server. For the range of workloads that we have examined, our results indicate that a page server is clearly preferable to an object server. Moreover, the adaptive page server is shown to provide very good performance, generally outperforming the pure page server, the pure object server, and the other alternatives as well."
"Successful companies organise and run their business activities in an efficient manner. Core activities are completed on time and within specified resource constraints. However to stay competitive in today's markets, companies need to continually improve their efficiency ¡ª business activities need to be completed more quickly, to higher quality and at lower cost. To this end, there is an increasing awareness of the benefits and potential competitive advantage that well designed business process management systems can provide. In this paper we argue the case for an agent-based approach: showing how agent technology can improve efficiency by ensuring that business activities are better scheduled, executed, monitored, and coordinated."
"In this continuation of Esther Duflo¡¯s in depth research from 1998-2008 on the impact of female leaders in India, the goal was to measure whether regions with a female Chief Minister (head of state) has resulted in an increase in education investment compared to the regions where men have remained dominant in leadership roles. To do this, six regions in India with female Chief Ministers are analyzed and six with male Ministers are analyzed for comparison."
"There is an increasing demand for systems that can automatically analyze images and extract semantically meaningful information. IRIS, an Integrated Retinal Information system, has been developed to provide medical professionals easy and unified access to the screening, trend and progression of diabetic-related eye diseases in a diabetic patient database. This paper shows how mining techniques can be used to accurately extract features in the retinal images. In particular, we apply a classification approach to determine the conditions for tortuousity in retinal blood vessels."
"Substantive changes in the business environment¡ªand aggressive initiatives in business process reengineering¡ªare driving corresponding changes in the information technology architectures of large enterprises. Those changes are enabled by the convergence of a long list of maturing new technologies. As one of its many implications, the new IT architecture demands revised assumptions about the design and deployment of databases. This paper reviews the components of the architectural shift now in process, and offers strategic planning assumptions for database professionals."
"Information integration provides a competitive advantage to businesses and is fundamental to on demand computing. It is strategic area of investment by software companies today whose goal is to provide a unified view of the data regardless of differences in data format, data location and access interfaces, dynamically manage data placement to match availability, currency and performance requirements, and provide autonomic features that reduce the burden on IT staffs for managing complex data architectures. This paper describes the motivation for integrating information for on demand computing, explains its requirements, and illustrates its value through usage scenarios. As shown in the paper, there is still a tremendous amount of research, engineering, and development work needed to make the full information integration vision a reality and it is expected that software companies will continue to heavily invest in aggressively pursing the information integration vision."
"This article presents a database programming language, Th¨¦mis, which supports subtyping and class hierarchies, and allows for the definition of integrity constraints in a global and declarative way. We first describe the salient features of the language: types, names, classes, integrity constraints (including methods), and transactions. The inclusion of methods into integrity constraints allows an increase of the declarative power of these constraints. Indeed, the information needed to define a constraint is not always stored in the database through attributes, but is sometimes computed or derived data. Then, we address the problem of efficiently checking constraints."
"Together with techniques developed for relational databases, this basis in logic means that deductive databases are capable of handling large amounts of information as well as performing reasoning based on that information. There are many application areas for deductive database technology. One area is that of decision support systems. In particular, the exploitation of an organization's resources requires fi~tbniy sufficient information about the current and future status of the resources themselves, but also a way of reasoning effectively about plans for the future. The present generation of decision support systems are severely deficient when it comes to reasoning about future plans. Deductive database technology is an appropriate solution to this problem. Another fruitful application area is that of expert systems. There are many computing applications in which there are large amounts of information, from which the important facts may be distilled by a simple yet tedious analysis. For example, medical analysis and monitoring can generate a large amount of data, and an error can have disastrous consequences.We demonstrate the COUGAR System, a new distributed data management infrastructure that scales with the growth of sensor interconnectivity and computational power on the sensors over the next decades. Our system resides directly on the sensor nodes and creates the abstraction of a single processing node without centralizing data or computation."
The aerospace industry poses significant challenges to information management unlike any other industry. Data management challenges arising from different segments of the aerospace business are identified through illustrative scenarios. These examples and challenges could provide focus and stimulus to further research in information management.
"In the last few years, workflow management has become a hot topic in the research community and, especially, in the commercial arena. Workflow management is multidisciplinary in nature encompassing many aspects of computing: database management, distributed client-server systems, transaction management, mobile computing, business process reengineering, integration of legacy and new applications, and heterogeneity of hardware and software. Many academic and industrial research projects are underway. Numerous successful products have been released. Standardization efforts are in progress under the auspices of the Workflow Management Coalition."
"Visual information, especially videos, plays an increasing role in our society for both work and entertainment as more sources become available to the user. Set-top boxes are poised to give home users access to videos that come not only from TV channels and personal recordings, but also from the Internet in the form of downloaded and streaming videos of various types. Current approaches such as Electronic Program Guides and video search engines search for video assets of one type or from one source. The capability to conveniently search through many types of video assets from a large number of video sources with easy-to-use user profiles cannot be found anywhere yet. VideoAnywhere has developed such a capability in the form of an extensible architecture as well as a specific implementation using the latest in Internet programming (Java, agents, XML, etc.) and applicable standards."
"After a system crash, databases recover to the last committed transaction, but applications usually either crash or cannot continue. The Phoenix purpose is to enable application state to persist across system crashes, transparent to the application program. This simplifies application programming, reduces operational costs, masks failures from users, and increases application availability, which is critical in many scenarios, e.g., e-commerce. Within the Phoenix project, we have explored how to provide application recovery efficiently and transparently via redo logging. This paper describes the conceptual framework for the Phoenix project, and the software infrastructure that we are building."
"Clustering is an unsupervised process since there are no predefined classes and no examples that would indicate grouping properties in the data set. The majority of the clustering algorithms behave differently depending on the features of the data set and the initial assumptions for defining groups. Therefore, in most applications the resulting clustering scheme requires some sort of evaluation as regards its validity. Evaluating and assessing the results of a clustering algorithm is the main subject of cluster validity. In this paper we present a review of the clustering validity and methods. More specifically, Part I of the paper discusses the cluster validity approaches based on external and internal criteria."
"The end of the Cold War bas brought significant changes for GM Hughes Electronics, one of the world¡¯s leading satellite and defense electronics companies. Their response to the loss of defense revenue was to marry their satellite communications expertise with the rapidly expanding entertainment industry to produce DIRECTV¡±, the first all-digital direct broadcast satellite (DBS) service in the United States. For years, customers in rural areas have used large, unsightly satellite dishes to receive television programming. The cost, size and complexity of these systems has limited their appeal. Hughes has now launched two geosynchronous satellites that use higher powered transmitters to send streams of compressed digital data to 18 inch antennas that can be mounted inauspiciously. A specialized video processor decompresses the signal and displays it on the consumer¡¯s television with better-thanbroadcast quality audio and video. The programming offered inchrdes a number of cable-like television broadcast services, music and scores of offerings of pay-per-view movies, sports and special events."
"This paper presents an approach that preserves the semi-atomicity (a weaker form of atomicity) of flexible transactions, allowing local sites to autonomously maintain serializability and recoverability. We offer a fundamental characterization of the flexible transaction model and precisely define the semi-atomicity. We investigate the commit dependencies among the subtransactions of a flexible transaction. These dependencies are used to control the commitment order of the subtransactions. We next identify those restrictions that must be placed upon a flexible transaction to ensure the maintenance of its semi-atomicity. As atomicity is a restrictive criterion, semi-atomicity enhances the class of executable global transactions."
"The distinctions among the protocols in terms of performance are significant. For example, an offered load where 70% - 80% of transactions under the global locking protocol were aborted, only 10% of transactions were aborted under the protocols based on the replication graph. The results of the study suggest that protocols based on a replication graph offer practical techniques for replica management. However, it also shows that performance deteriorates rapidly and dramatically when transaction throughput reaches a saturation point."
"The publish/subscribe paradigm is a simple to use interaction model that consists of information providers, who publish events to the system; and of information consumers, who subscribe to events of interest within the system. The publish/subscribe system ensures the timely notification of subscribers upon event occurrence. Events can be seen as data items (, tuples, columns, or tables) in the relational database model and subscriptions closely resemble database queries. From this point of view, publish/subscribe systems solve a problem inverse to database query processing (that is, evaluate an event on a set of subscriptions to identify the matching ones). Information dissemination services are often ¡°add-ons¡± to auction sites, shopping sites, or information services (for example, news, sports, traffic) that allow a subscriber to express interest in certain events and consequently be notified upon the occurrence of the event. For instance, a site offering apartments (rental or sale) may allow a user to submit a detailed subscription constraining location, size, price, and nearby attractions of the ideal apartment."
"In this article we introduce the first index structure, called the QIC-M-tree, that can process user-defined queries in generic metric spaces, that is, where the only information about indexed objects is their relative distances. The QIC-M-tree is a metric access method that can deal with several distinct distances at a time: (1) a query (user-defined) distance, (2) an index distance (used to build the tree), and (3) a comparison (approximate) distance (used to quickly discard from the search uninteresting parts of the tree). We develop an analytical cost model that accurately characterizes the performance of the QIC-M-tree and validate such model through extensive experimentation on real metric data sets. In particular, our analysis is able to predict the best evaluation strategy (i.e., which distances to use) under a variety of configurations, by properly taking into account relevant factors such as the distribution of distances, the cost of computing distances, and the actual index structure."
"Materialized views and view maintenance are important for data warehouses, retailing, banking, and billing applications. We consider two related view maintenance problems: 1) how to maintain views after the base tables have already been modified, and 2) how to minimize the time for which the view is inaccessible during maintenance.Typically, a view is maintained immediately, as a part of the transaction that updates the base tables. Immediate maintenance imposes a significant overhead on update transactions that cannot be tolerated in many applications. In contrast, deferred maintenance allows a view to become inconsistent with its definition. A refresh operation is used to reestablish consistency. We present new algorithms to incrementally refresh a view during deferred maintenance."
"We use conventional hardware for servers and clients and examine bottlenecks and optimization options systematically, in order to reduce jitter and increase the maximum number of clients that the system can support. We show that the diversity of client performance characteristics can be taken into account, so that all clients are well supported for delay-sensitive retrieval in a heterogeneous environment. We also show that their characteristics can be exploited to maximize server throughput under server memory constrains."
"We demonstrate the COUGAR System, a new distributed data management infrastructure that scales with the growth of sensor interconnectivity and computational power on the sensors over the next decades. Our system resides directly on the sensor nodes and creates the abstraction of a single processing node without centralizing data or computation."
"Data exchange formats were originally devised for moving data between programs and between groups of researchers in a platform-independent file format. They are mostly self-describing, containing data element definitions along with the base data, though in some cases they involve a standardized external data dictionary. DXS allow exchange of data structures between programs, not just byte streams. They tend not to support a behavioral component as part of the interchange format, though some have assertions and derived data elements. They are typically implemented as a procedure library that is linked with an application, along with some stand-alone utilities, An interesting phenomenon is that DXS are being used for data management, alt bough they were originally intended for data exchange. Research groups keep their data in files using one of these formats, and reprogram their tools or write adaptors to use data in that format. The self-description means that, as with a database management system, there is no longer a dependence on a particular application program in order to be able to read and decode the data, This use of DXS for data storage is acknowledged in the tools that are appearing, such as DX-file browsers and cataloging facilities."
"This paper takes the next logical step: It considers the use of timestamping for capturing transaction and valid time in the context of transactions. The paper initially identifies and analyzes several problems with straightforward timestamping, then proceeds to propose a variety of techniques aimed at solving these problems. Timestamping the results of a transaction with the commit time of the transaction is a promising approach. The paper studies how this timestamping may be done using a spectrum of techniques. While many database facts are valid until now, the current time, this value is absent from the existing temporal types. Techniques that address this problem using different substitute values are presented. Using a stratum architecture, the performance of the different proposed techniques are studied. Although querying and modifying time-varying data is accompanied by a number of subtle problems, we present a comprehensive approach that provides application programmers with simple, consistent, and efficient support for modifying bitemporal databases in the context of user transactions."
"SilkRoute composes the application query with the public-view query, translates the result into SQL, executes this on the relational engine, and assembles the resulting tuple streams into an XML document. This work makes some key contributions to XML query processing. First, it describes an algorithm that translates an XQuery expression into SQL. The translation depends on a query representation that separates the structure of the output XML document from the computation that produces the document's content. The second contribution addresses the optimization problem of how to decompose an XML view over a relational database into an optimal set of SQL queries. We define formally the optimization problem, describe the search space, and propose a greedy, cost-based optimization algorithm, which obtains its cost estimates from the relational engine. Experiments confirm that the algorithm produces queries that are nearly optimal."
"Motivated by this, we propose a new index structure called the TPR*- tree, which takes into account the unique features of dynamic objects through a set of improved construction algorithms. In addition, we provide cost models that determine the optimal performance achievable by any data-partition spatio-temporal access method. Using experimental comparison, we illustrate that the TPR*-tree is nearly-optimal and significantly outperforms the TPR-tree under all conditions."
"This issue presents you with three workshop reports organized by Brian Cooper, the new associate editor for the workshop reports and technical notes. The first report summarized the events and discussions at the EDBT summer school on XML and Databases, contributed by Riccardo Torlone and Paolo Atzeni. The second report by Ioana Manolescu and Tannis Papakonstantinou, gives an overview of the workshop on the XQuery implementation, Experience, and Perspectives, which was held this year in Paris, France, incorporation with the ACM SIGMOD conference. The third workshop My term as the Editor of the SIGMOD RECORD is ending delighted to present y"
"We present a novel framework and a tool (ToMAS) for automatically adapting mappings as schemas evolve. Our approach considers not only local changes to a schema, but also changes that may affect and transform many components of a schema. We consider a comprehensive class of mappings for relational and XML schemas with choice types and (nested) constraints. Our algorithm detects mappings affected by a structural or constraint change and generates all the rewritings that are consistent with the semantics of the mapped schemas. Our approach explicitly models mapping choices made by a user and maintains these choices, whenever possible, as the schemas and mappings evolve. We describe an implementation of a mapping management and adaptation tool based on these ideas and compare it with a mapping generation tool."
"To support efficient similarity searches in an NDDS, we propose a new dynamic indexing technique, called the ND-tree. The key idea is to extend the relevant geometric concepts as well as some indexing strategies used in CDSs to NDDSs. Efficient algorithms for ND-tree construction are presented. Our experimental results on synthetic and genomic sequence data demonstrate that the performance of the ND-tree is significantly better than that of the linear scan and M-tree in high dimensional NDDSs."
"For many years, TIBCO (the Information Bus Company) has pioneered the use of Publish/Subscribe¡ªa form of push technology ¡ª to build flexible, real-time loosely-coupled distributed applications. Today, Publish/Subscribe is used by 300 of the world's largest financial institutions, deployed in 6 of the top 10 semiconductor manufacturer' factory floors, utilized in the implementation large-scale Internet services like Yahoo, Intuit, and ETrade, and chosen by many of the world's leading corporations as the enterprise infrastructure for integrating disparate applications. In this paper, we will:Contrast the Publish/Subscribe event-driven interaction paradigm against the traditional demand-driven request-reply interaction paradigm"
"Query optimizers nowadays draw upon many sources of information about the database to optimize queries. They employ runtime statistics in cost-based estimation of query plans. They employ integrity constraints in the query rewrite process. Primary and foreign key constraints have long played a role in the optimizer, both for rewrite opportunities and for providing more accurate cost predictions. More recently, other types of integrity constraints are being exploited by optimizers in commercial systems, for which certain semantic query optimization techniques have now been implemented."
"The main components of MIND are a global query processor, a global transaction manager, a schema integrator, interfaces to supported database systems and a user graphical interface.In MIND all local databases are encapsulated in a generic database object with a well defined single interface. This approach hides the differences between local databases from the rest of the system. The integration of export schemas is currently performed manually by using an object definition language (ODL) which is based on OMG's interface definition language. The DBA builds the integrated schema as a view over export schemas. the functionalities of ODL allow selection and restructuring of schema elements from existing local schemas.MIND global query optimizer aims at maximizing the parallel execution of the intersite joins of the global subqueries. Through MIND global transaction manager, the serializable execution of the global transactions are provided."
"There are a variety of main-memory access structures, such as segment trees, and quad trees, whose properties, such as good worstcase behaviour, make them attractive for database applicdions. Unfortunately, the structures are typically ¡®long and skinny¡¯, whereas disk data structuies must be ¡®shortand-fat (that is, have a high fanout and low height) in order to minimize I/O. We consider how to cluster the nodes (that is, map the nodes to disk pages) of mainmemory access structures such that although a path may traverse many nodes, it only traverses a few disk pages. The number of disk pages traversed in a path is called the external path length. We address several versions of the clustering problem. We present a clustering algorithm for tree structures that generates optimal worst-case external path length mappings; we also show how to make it dynamic, to support updates. We extend the algorithm to generate mappings that minimize the average weighted external path lengths. We also show that some other clustering problems, such as finding optimal external path lengths for DAG structures"
"This paper describes an advanced development program to create a medical information system called the National Medical Knowledge Bank (NMKB). This five year program is sponsored in part by a grant from the National Institute of Standards and Technology Advanced Technology Program. The goals of the program, covering computer-assisted diagnosis, medical training, remote consultation, and medical records storage, are defined. The webbased architecture of the medical knowledge bank is presented, including the Teradata Multimedia Services, an object/relational database which serves as the central data repository for medical data stored in multiple data types. Also described are the applications of physician support, including case-based reasoning and image analysis for determining case similarity; virtual medical conferences; and initial/continuing medical education."
"In this special issue on metadata management, we present a new work on creating, gathering, managing, and understanding metadata. The work in this issue highlights the reality that the lack of metadata and effective techniques for managing them is currently one of the biggest challenges to meaningful use and sharing of the wealth (or should we say glut) of data available today."
"The overall theme of the FQAS conferences is innovative query systems that are aimed at providing easy, flexible and intuitive access to information. Such systems are intended to facilitate retrieval from information repositories such as databases, libraries, and the World Wide Web. These repositories are typically equipped with standard query systems, which are often inadequate, and the focus of FQAS is the development of query systems that are more expressive, informative, cooperative and productive."
"This paper proposes a system for personalization of web portals. A specic implementation is discussed in reference to a web portal containing a news feed service. Techniques are proposed for effective categorization, management, and personalization of news feeds obtained from a live news wire service. The process consists of two steps: first manual input is required to build the domain knowledge which could be site-specific; then the automated component uses this domain knowledge in order to perform the personalization, categorization and presentation. Effective schemes for advertising are proposed, where the targeting is done using both the information about the user and the content of the web page on which the advertising icon appears. Automated techniques for identifying sudden variations in news patterns are described; these may be used for supporting news-alerts. A description of a version of this software for our customer web site is provided."
"Growing amount of XML encoded data exchanged over the In- ternet increases the importance of XML based publish-subscribe (pub-sub) and content based routing systems. The input in such systems typically consists of a stream of XML documents and a set of user subscriptions expressed as XML queries. The pub-sub system then filters the published documents and passes them t o the subscribers. Pub-sub systems are characterized by very high input ratios, therefore the processing time is critical."
"The growth of the geomatics industry is stunted by the difficulty of obtaining and transforming suitable spatial data. This paper describes a remedy: the Open Geospatial Datastore Interface (OGDI), which permits application software to access a variety of spatial data products. The discussion compares the OGDI approach to other standards efforts and describes the characteristics and use of OGDI, which is in the public domain."
"In this issue of Leaven, we explore the theme of local church ministry by honoring the legacy of Paul and Kay Watson. The following reflections and essays are written by those who bear appreciative witness to the faithful service of this Christian couple. Paul and Kay have dedicated their time, love, and spiritual gifts for the last three decades to the Cole Mill Road congregation in Durham, North Carolina. And through their missionary travels and a host of teaching opportunities, their influence has been felt by those far beyond their home church."
"In this paper, we propose novel techniques for performing SVD-based dimensionality reduction in dynamic databases. When the data distribution changes considerably so as to degrade query precision, we recompute the SVD transform and incorporate it in the existing index structure. For recomputing the SVD-transform, we propose a novel technique that uses aggregate data from the existing index rather than the entire data. This technique reduces the SVD-computation time without compromising query precision. We then explore efficient ways to incorporate the recomputed SVD-transform in the existing index structure. These techniques reduce the computation time by a factor of 20 in experiments on color and texture image vectors. The error due to approximate computation of SVD is less than 10%."
"¡°Push Technology¡± stands for the ability to transfer information as a reaction to event occurrence. This demonstration proposal describes Amit, a middleware framework that resolves a major problem in this area: the gap that exists between events that are reported by various channels, and the actual cases in which the user needs to react to, hereby called; reactive situations. These situations are composition of events or other situations (for example, ¡°when atleast four events of the same type occurred¡±) or content filtering on events (for example, ¡°only events that relate to IBM stocks¡±) or both (¡°when atleast four purchases of more than 50,000 shares have been performed on IBM stocks in a single week¡±). This paper describes the generic application development tool, the middleware architecture and framework, and describes the demo."
"Oracle Corporation, the world¡¯s second largest software company, is the leading supplier of software for enterprise information management. The company has two major businesses-one providing the lowest cost information technology infrastructure and another offering business and competitive advantage through high-value applications Oracle is one of the first software companies to implement its model of enterprise software management through network computing, and is the first major software company to make full-featured products available electronically on the Internet. Oracle is the only company capable of implementing end-to-end enterprise IT infrastmcture and applications solutions on a global scale."
Our algorithm has the following characteristics: (1) It requires only one pass over the data; (2) It is deterministic; (3) It produces good lower and upper bounds of the true values of the quantiles; (4) It requires no a priori knowledge of the distribution of the data set; (5) It has a scalable parallel formulation; (6) Extra time and memory for computing additional quantiles (beyond the first one) are constant per quantile. We present experimental results on the IBM SP-2. The experimental results show that the algorithm is indeed robust and does not depend on the distribution of the data sets.
"The chief editor' s ethics are the requirements put forward by the authors,editors and readers in ethical system based on identifying the scholarly publishing environment values for maintaining the moral attitudes and behavior in academic exchanges."
"We present a novel framework for mapping between any combination of XML and relational schemas, in which a high-level, user-specified mapping is translated into semantically meaningful queries that transform source data into the target representation. Our approach works in two phases. In the first phase, the high-level mapping, expressed as a set of inter-schema correspondences, is converted into a set of mappings that capture the design choices made in the source and target schemas (including their hierarchical organization as well as their nested referential constraints). The second phase translates these mappings into queries over the source schemas that produce data satisfying the constraints and structure of the target schema, and preserving the semantic relationships of the source. Nonnull target values may need to be invented in this process. The mapping algorithm is complete in that it produces all mappings that are consistent with the schema constraints. We have implemented the translation algorithm in Clio, a schema mapping tool, and present our experience using Clio on several real schemas."
"Repositories manage metadata. Metadata describes complex artifacts that are the subject of formal design activities, such as business processes, application interfaces, database (DB) schemas, engineering drawings, software configurations, ,and document libraries, Demand for them is growing, fueled by enterprise re-engineenng, integrated CASE, data warehouse, <and management systems for networks, computer systems, information resources, documents, web sites, etc. It¡¯s hard 10 measure product revenue, because repositories ,are often embedded in other products, but it¡¯s arguably already a billion dollar per year business. It¡¯s likely to get a lot bigger."
"We revise the historical evolution of the societies devoted to Developmental Biology from the early activities of the Institut International dEmbryologie (IIE), founded in 1911, with particular emphasis on the more recent constitution of the Spanish Sociedad Espa?ola de Biolog¨ªa del Desarrollo (SEBD), founded in 1994, and the Portuguese Sociedade Portuguesa de Biologia do Desenvolvimento (SPBD), founded in 2006. We also describe the role played by The International Journal of Developmental Biology (IJDB) in the constitution of the SEBD and its projection and support to international Developmental Biology societies and individual researchers in the world, according to its mission to be a non-for-profit publication for scientists, by scientists."
"In this paper, we give an overview of the semantic integrity support in the most recent SQL-standard SQL:1999, and we show to what extent the different concepts and language constructs proposed in this standard can be found in major commercial (object-)relational database management systems. In addition, we discuss general design guidelines that point out how the semantic integrity features provided by these systems should be utilized in order to implement an effective integrity enforcing subsystem for a database."
"Four different pointer swizzling techniques allowing object replacement are investigated and compared with the performance of an object manager employing no pointer swizzling. The extensive qualitative and quantitative evaluation¡ªonly part of which could be presented in this article¡ªdemonstrate that there is noone superior pointer swizzling strategy forall application profiles. Therefore, an adaptable object base run-time system is devised that employs the full range of pointer swizzling strategies, depending on the application profile characteristics that are determined by, for example, monitoring in combination with sampling, user specifications, and/or program analysis."
"Galax is a light-weight, portable, open-source implementation of XQuery 1.0. Started in December 2000 as a small prototype designed to test the XQuery static type system, Galax has now become a solid implementation, aiming at full conformance with the family of XQuery 1.0 specifications. Because of its completeness and open architecture, Galax also turns out to be a very convenient platform for researchers interested in experimenting with XQuery optimization."
"We propose a new notion of surprising temporal patterns in market. basket data, and algorithms to find such pat,terns. This is distinct, from finding frequent pat-terns as addressed in the common mining literature. We argue that. once the analyst. is already familiar with prevalent patterns in t,he data, the greatest, increment,al benefit. is likely t,o be from changes in the relationship between item frequencies"
"To take advantage of this batch processing in achieving fast response time, this paper uses prediction methods to predict future values. FFT is used to compute the cross correlations of the predicted series (with the values that have already arrived) and the database patterns, and to obtain predicted distances between the incoming time series at many future time positions and the database patterns. When the actual data value arrives, the prediction error together with the predicted distances is used to filter out patterns that are not possible to be the nearest or near neighbors, which provides fast responses. Experiments show that with reasonable prediction errors, the performance gain is significant."
"We introduce and study a new class of queries that we refer to as OPAC (optimization under parametric aggregation constraints) queries. Such queries aim to identify sets of database tuples that constitute solutions of a large class of optimization problems involving the database tuples. The constraints and the objective function are specified in terms of aggregate functions of relational attributes, and the parameter values identify the constants used in the aggregation constraints."
"Deductive databases generalize relational databases by providing support for recursive views and non-atomic data. Aditi is a deductive system based on the client-server model; it is inherently multi-user and capable of exploiting parallelism on shared-memory multiprocessors. The back-end uses relational technology for efficiency in the management of disk-based data and uses optimization algorithms especially developed for the bottom-up evaluation of logical queries involving recursion. The front-end interacts with the user in a logical language that has more expressive power than relational query languages. We present the structure of Aditi, discuss its components in some detail, and present performance figures."
"A major bottleneck in implementing sampling as a primitive relational operation is the inefficiency of sampling the output of a query. It is not even known whether it is possible to generate a sample of a join tree without first evaluating the join tree completely. We undertake a detailed study of this problem and attempt to analyze it in a variety of settings. We present theoretical results explaining the difficulty of this problem and setting limits on the efficiency that can be achieved. Based on new insights into the interaction between join and sampling, we develop join sampling techniques for the settings where our negative results do not apply. Our new sampling algorithms are significantly more efficient than those known earlier. We present experimental evaluation of our techniques on Microsoft's SQL Server 7.0."
"In this paper we present FeedbackBypass, a new approach to interactive similarity query processing. It complements the role of relevance feedback engines by storing and maintaining the query parameters determined with feedback loops over time, using a wavelet-based data structure (the Simplex Tree). For each query, a favorable set of query parameters can be determined and used to either ¡°bypass¡± the feedback loop completely for already-seen queries, or to start the search process from a near-optimal configuration. FeedbackBypass can be combined well with all state-of-the-art relevance feedback techniques working in high-dimensional vector spaces. Its storage requirements scale linearly with the dimensionality of the query space, thus making even sophisticated query spaces amenable."
"Over the last few years, there has been a tremendous increase in the number of interactive multimedia presentations prepared by different individuals and organizations. In this paper, we present an algebra for querying multimedia presentation databases. In contrast to the relational algebra, an algebra for interactive multimedia presentations must operate on trees whose branches reflect different possible playouts of a family of presentations. The query language supports selection type operations for locating objects and presentation paths that are of interest to the user, join type operations for combining presentations from multiple databases into a single presentation, and finally set theoretic operations for comparing different databases. The algebra operations can be used to locate presentations with specific properties and also for creating new presentations by borrowing different components from existing ones. We prove a host of equivalence results for queries in this algebra which may be used to build query optimizers for interactive presentation databases."
"In this article we consider a number of different possible options in the behavior of an active DBMS, based on a broad analysis of some of the best known implemented systems and prototypes. We encode these options in a user-readable form, called Extended ECA. A rule from any existing system can be rewritten in this formalism making all the semantic choices apparent. Then an EECA rule can be automatically translated into an internal (less readable) format, based on a logical style, which is called core format: the execution semantics of core rules is specified as the fixpoint of a simple transformation involving core rules. As an important premise to this research, a semantics for database updates and transactions has also been established, with respect to a notion of state that comprises both data and events. The article also presents an extensive bibliography on the subject of active databases."
"The contribution of this project is threefold: (1) efficient generation for large itemsets by hash method (2) effective reduction on itemsets scan required by the division approach and (3) the option of reducing the number of database scans required Our proposed hash and division-based techniques, HD algorithm, is very efficient for the generation of candidate large itemsets where the number of candidate large itemsets generated by HD is, smaller than that by many methods such as the Apriori algorithm, DHP algorithm and DIC algorithm According to our simulation results, the proposed approach is more efficient than any existing algorithms."
"Earth observation (EO) and simulation data share some core characteristics: they resemble raster data of some spatio-temporal dimensionality; the complete objects are extremely large, well into Tera- and Petabyte volumes; data generation and retrieval follow very different access patterns. EO time series additionally share that acquisition/generation happens in time slices."
"The structural representation we consider are strings and the distance metric is string edit distance permitting variable length don't cares. Our techniques incorporate string matching algorithms and novel heuristics for discovery and optimization, most of which generalize to other combinatorial structures."
"The PBSM algorithm partitions the inputs into manageable chunks, and joins them using a computational geometry based plane-sweeping technique. This paper also presents a performance study comparing the the traditional indexed nested loops join algorithm, a spatial join algorithm based on joining spatial indices, and the PBSM algorithm. These comparisons are based on complete implementations of these algorithms in Paradise, a database system for handling GIS applications. Using real data sets, the performance study examines the behavior of these spatial join algorithms in a variety of situations, including the cases when both, one, or none of the inputs to the join have an suitable index. The study also examines the effect of clustering the join inputs on the performance of these join algorithms."
"An infrastructure for transactional processes hasto support all these run-time features. Furthermore,a graphical process modeling tool should support thespeci?cation of all these features. An important aspectis that such a modeling tool is transparently integratedinto the process management environment.In addition to the transactional semantics of ser-vice composition, several other run-time aspects arecrucial. Usually, several semantically equivalent webservices are available at di?erent places. An infrastruc-ture for process execution should equally distribute theload over all web service providers. Similarly, processexecutions should take costs and expected executiontimes into account to optimize response times."
"In this paper, we review and compare the existing algorithms for clustering highdimensional data and show the impact of the curse of dimensionality on their e ectiveness and e ciency. The comparison reveals that condensation-based approaches (such as BIRCH or STING) are the most promising candidates for achieving the necessary e ciency, but it also shows that basically all condensation-based approaches have severe weaknesses with respect to their e ectiveness in highdimensional space. To overcome these problems, we develop a new clustering technique called OptiGrid which is based on constructing an optimal grid-partitioning of the data. The optimal grid-partitioning is determined by calculating the best partitioning hyperplanes for each dimension (if such a partitioning exists) using certain projections of the data. The advantages of our new approach are (1) it has a rm mathematical basis (2) it is by far more e ective than existing clustering algorithms for highdimensional data (3) it is very e cient even for large data sets of high dimensionality. To demonstrate the e ectiveness and e ciency of our new approach, we perform a series of experiments on a number of di erent data sets including real data sets from CAD and molecular biology. A comparison with one of the best known algorithms (BIRCH) shows the superiority of our new approach."
"The database area has been one of those areas of computerscience which have very directly been driven by applicationrequirements; this is true today in three ways: First, the userswant more application specific support from the database, and theyexpect the DBMS to have more semantic application knowledge.Second, users want database support for new applications which aresometimes far from the traditional database applications andintroduce completely new requirements as well as the need tosmoothly integrate database technology with other advancedtechnologies (e.g. neural nets) in one application. Finally, theembedding of databases into interactive work environments - forinstance, the use of databases in cooperative environments(computer supported cooperative work) - forces the databasecommunity to reconsider some of the traditional beliefs aboutdatabases."
"While work in recent years has demonstrated that wavelets can be efficiently used to compress large quantities of data and provide fast and fairly accurate answers to queries, little emphasis has been placed on using wavelets in approximating datasets containing multiple measures. Existing decomposition approaches will either operate on each measure individually, or treat all measures as a vector of values and process them simultaneously. We show in this paper that the resulting individual or combined storage approaches for the wavelet coefficients of different measures that stem from these existing algorithms may lead to suboptimal storage utilization, which results to reduced accuracy to queries. To alleviate this problem, we introduce in this work the notion of an extended wavelet coefficient as a flexible storage method for the wavelet coefficients, and propose novel algorithms for selecting which extended wavelet coefficients to retain under a given storage constraint. Experimental results with both real and synthetic datasets demonstrate that our approach achieves improved accuracy to queries when compared to existing techniques."
"This distributes Business Modeling computations across many query blocks, making applications coded in SQL hard to develop. The limitations of RDBMS have been filled by spreadsheets and specialized MOLAP engines which are good at formulas for mathematical modeling but lack the formalism of the relational model, are difficult to manage, and exhibit scalability problems. This demo presents a scalable, mathematically rigorous, and performant SQL extensions for Relational Business Modeling, called the SQL Spreadsheet. We present examples of typical Business Modeling computations with SQL spreadsheet and compare them with the ones using standard SQL showing performance advantages and ease of programming for the former. We will show a scalability example where data is processed in parallel and will present a new class of query optimizations applicable to SQL spreadsheet."
"After revealing the strong performance shortcomings of the state-of-the-art algorithm for k-nearest neighbor search [Korn et al. 1996], we present a novel multi-step algorithm which is guaranteed to produce the minimum number of candidates. Experimental evaluations demonstrate the significant performance gain over the previous solution, and we observed average improvement factors of up to 120 for the number of candidates and up to 48 for the total runtime."
"In this paper, we propose the novel idea of hierarchical subspace sampling in order to create a reduced representation of the data. The method is naturally able to estimate the local implicit dimensionalities of each point very effectively, and thereby create a variable dimensionality reduced representation of the data. Such a technique has the advantage that it is very adaptive about adjusting its representation depending upon the behavior of the immediate locality of a data point. An interesting property of the subspace sampling technique is that unlike all other data reduction techniques, the overall efficiency of compression improves with increasing database size. This is a highly desirable property for any data reduction system since the problem itself is motivated by the large size of data sets. Because of its sampling approach, the procedure is extremely fast and scales linearly both with data set size and dimensionality. Furthermore, the subspace sampling technique is able to reveal important local subspace characteristics of high dimensional data which can be harnessed for effective solutions to problems such as selectivity estimation and approximate nearest neighbor search."
"A function-based approach and mechanism to support sharing among the component database systems in a federation is described. In the context of a functional object-based database model, a technique to support inter-component information unit and behavior sharing is presented. An experimental system that implements the function-based sharing mechanism is described, its underlying algorithms are outlined, and its practical utility and effectiveness are assessed. This work is couched in the framework of the Remote-Exchange research project and experimental system."
"Lotus Notes is a commercial product that empowers individuals and organizations to collaborate and share information [1].Notes enables the easy development of applications such as messaging, document management, workflow, and asynchronous conferencing. Notes applications can be deployed globally, across independent organizations, among a heterogeneous network of loosely coupled computers that range in size from small notebooks to large multi-processor systems.The third major release of Lotus Notes occurred in May 1993."
"Recently, the use of XML documents, where some of the data is given explicitly, while other parts are defined by programs that generate the relevant data, started gaining popularity. This chapter refers to such documents as intensional documents. Materialization is the process of invoking some of the programs included in an XML document and replacing them by their results. The goal of this demonstration is to advocate for the exchange of such intensional XML documents between applications, and to illustrate the new possibilities and the great flexibility they bring to application design."
"A remote backup is a copy of a primary database maintained at a geographically separate location and is used to increase data availability. Remote backup systems are typically log-based and can be classified into 2-safe and 1-safe, depending on whether transactions commit at both sites simultaneously or first commit at the primary and are later propagated to the backup. We have built an experimental database system on which we evaluated the performance of the epoch and the dependency reconstruction algorithms, two 1-safe algorithms we have developed. We compared the 1-safe with the 2-safe approach under various conditions."
"We extend this work by considering how these languages can be used in practice. Specifically, we consider a restricted class of higher order views and show the power of these views in integrating legacy structures. Our results provide insights into the properties of restructuring transformations required to resolve schematic discrepancies. In addition, we show how the use of these views permits schema browsing and new forms of data independence that are important for global information systems. Furthermore, these views provide a framework for integrating semi-structured and unstructured queries, such as keyword searches, into a structured querying environment. We show how these views can be used with minimal extensions to existing query engines. We give conditions under which a higher order view is usable for answering a query and provide query translation algorithms."
"We propose a new class of algorithms that can be used to speed up the execution of multi-way join queries or of queries that involve one or more joins and a group-by. These new evaluation techniques allow to perform several hash-based operations (join and grouping) in one pass without repartitioning intermediate results. These techniques work particularly well for joining hierarchical structures, e.g., for evaluating functional join chains along key/foreign-key relationships. The idea is to generalize the concept of hash teams as proposed by Graefe et.al [GBC98] by indirectly partitioning the input data. Indirect partitioning means to partition the input data on an attribute that is not directly needed for the next hash-based operation, and it involves the construction of bitmaps to approximate the partitioning for the attribute that is needed in the next hash-based operation. Our performance experiments show that such generalized hash teams perform significantly better than conventional strategies for many common classes of decision support queries."
"TPC-DS is a new decision support benchmark currently under development by the Transaction Processing Performance Council (TPC). This paper provides a brief overview of the new benchmark. The benchmark models the decision support functions of a retail product supplier, including data loading, multiple types of queries and data maintenance. The database consists of multiple snowflake schemas with shared dimension tables; data is skewed; and the query set is large. Overall, the benchmark is considerably more realistic than previous decision support benchmarks."
"DataJoiner (DJ) is a heterogeneous database system that provides a single database image of multiple databases. It provides transparent access to tables at remote databases through user defined aliases (nicknames) that can be accessed as if they were local tables. DJ is also a fully functional relational database system. A couple of salient features of the DataJoiner query optimizer are: (1) A query submitted to DataJoiner is optimized using a cost model that takes into account the remote optimizer¡¯s capabilities in addition to the remote query processing capabilities and (2) If a remote database system lacks some functionality (eg: sorting), DataJoiner compensates for it. In this paper, we present the design of the Datajoiner query optimizer."
"A system that supports both late binding and inverted functions must be able to solvefn(y)-.x for a given x and unknown y whenfn is late bound, i.e. the resolvent (implementation of a function name) to apply on y is selected based on the type of y. This combination of late binding and inverted function calls require novel query processing capabilities to fully utilize indexes referenced in late bound function calls. This paper presents an approach to the management of late binding in query processing. The main result is a query processing method where late bound function calls are efficiently executed and optimized for both inverted and regular execution. The proposed solution is based on substituting each late bound function call in the execution plan with a special function, DTR, which dynamically selects the actual resolvent to call. We define the inverse of DTR and its correctness. We show a dramatic execution time improvement by making DTR invertible and by defining its cost model for query optimization. The improvements are verified by performance measurements."
"Assume that each object in a database has m grades, or scores, one for each of m attributes. For example, an object can have a color grade, that tells how red it is, and a shape grade, that tells how round it is. For each attribute, there is a sorted list, which lists each object and its grade under that attribute, sorted by grade (highest grade first). Each object is assigned an overall grade, that is obtained by combining the attribute grades using a fixed monotone aggregation function, or combining rule, such as min or average. In this overview, we discuss and compare algorithms for determining the top k objects, that is, k objects with the highest overall grades."
"This demo shows several advanced use cases of location-based services and demonstrates how these use cases are facilitated by a mediation middleware for spatial information, the Nexus Platform. The scenario shows how a mobile user can access location-based information via so called Virtual Information Towers, register spatial events, send and receive geographical messages or find her friends by displaying other mobile users. The platform facilitates these functions by transparently combining spatial data from a dynamically changing set of data providers, tracking mobile objects and observing registered spatial events."
"In this paper, we present the first incremental clustering algorithm. Our algorithm is based on the clustering algorithm DBSCAN which is applicable to any database containing data from a metric space, e.g., to a spatial database or to a WWW-log database. Due to the density-based nature of DBSCAN, the insertion or deletion of an object affects the current clustering only in the neighborhood of this object. Thus, efficient algorithms can be given for incremental insertions and deletions to an existing clustering. Based on the formal definition of clusters, it can be proven that the incremental algorithm yields the same result as DBSCAN. A performance evaluation of IncrementalDBSCAN on a spatial database as well as on a WWW-log database is presented, demonstrating the efficiency of the proposed algorithm. IncrementalDBSCAN yields significant speed-up factors over DBSCAN even for large numbers of daily updates in a data warehouse."
"n the theoretical side, we prove that with high probability, it produces a result that is a (1 + ¦Å) factor approximation to the Euclidean nearest neighbor. On the practical side, it turns out to be extremely efficient, often exploring no more than 5% of the data to obtain very high-quality results. This method is also database-friendly, in that it accesses data primarily in a pre-defined order without random accesses, and, unlike other methods for approximate nearest neighbors, requires almost no extra storage. Also, we extend our approach to deal with the k nearest neighbors.We conduct two sets of experiments to evaluate the efficacy of our methods. Our experiments include two scenarios where nearest neighbors are typically employed---similarity search and classification problems."
"In this paper, we introduce the concept of extended feature objects for similarity retrieval. Conventional approaches for similarity search in databases map each object in the database to a point in some high-dimensional feature space and define similarity as some distance measure in this space. For many similarity search problems, this feature-based approach is not sufficient. When retrieving partially similar polygons, for example, the search cannot be restricted to edge sequences, since similar polygon sections may start and end anywhere on the edges of the polygons. In general, inherently continuous problems such as the partial similarity search cannot be solved by using point objects in feature space. In our solution, we therefore introduce extended feature objects consisting of an infinite set of feature points. For an efficient storage and retrieval of the extended feature objects, we determine the minimal bounding boxes of the feature objects in multidimensional space and store these boxes using a spatial access structure. In our concrete polygon problem, sets of polygon sections are mapped to 2D feature objects in high-dimensional space which are then approximated by minimal bounding boxes and stored in an R-Tree."
"Service composition is gaining momentum as the potential silver bullet for the envisioned Semantic Web. It purports to take the Web to unexplored efficiencies and provide a flexible approach for promoting all types of activities in tomorrow¡¯s Web. Applications expected to heavily take advantage of Web service composition include B2B E-commerce and E-government. To date, enabling composite services has largely been an ad hoc, time-consuming, and error-prone process involving repetitive low-level programming. In this paper, we propose an ontology-based framework for the automatic composition of Web services. We present a technique to generate composite services from high-level declarative descriptions. We define formal safeguards for meaningful composition through the use of composability rules. These rules compare the syntactic and semantic features of Web services to determine whether two services are composable. We provide an implementation using an E-government application offering customized services to indigent citizens. Finally, we present an exhaustive performance experiment to assess the scalability of our approach."
"The proliferation and affordability of smart sensors such as webcams, microphones, etc., has created opportunities for exciting new classes of distributed services. While such sensors are inexpensive and easy to deploy across a wide area, realizing useful services requires addressing a number of challenges, such as preventing transfer of large data feeds across the network, efficiently discovering relevant data among the distributed collection of sensors and delivering it to interested participants, and efficiently handling static meta-data information, live readings from sensor feeds, and historical data."
"A range query applies an aggregation operation over all selected cells of an OLAP data cube where the selection is specified by providing ranges of values for numeric dimensions. We present fast algorithms for range queries for two types of aggregation operations: SUM and MAX. These two operations cover techniques required for most popular aggregation operations, such as those supported by SQL."
"We develop algorithms for extracting detailed information about query plans through narrow optimizer interfaces, and we perform the characterization using database statistics from a published run of the TPC-H benchmark and a wide range of storage parameters.We show that, when data structures such as tables, indexes, and sorted runs reside on different storage devices, the optimizer can derive significant benefits from having accurate and timely information regarding the cost of accessing storage devices."
"In this paper we describe an efficient, non-blocking mechanism for reordering, which can be used over arbitrary data streams from files, indexes, and continuous data feeds. We also investigate several policies for the reordering based on the performance goals of various typical applications. We present results from an implementation used in Online Aggregation in the Informix Dynamic Server with Universal Data Option, and in sorting and scrolling in a large-scale spreadsheet. Our experiments demonstrate that for a variety of data distributions and applications, reordering is responsive to dynamic preference changes, imposes minimal overheads in overall completion time, and provides dramatic improvements in the quality of the feedback over time. Surprisingly, preliminary experiments indicate that online reordering can also be useful in traditional batch query processing, because it can serve as a form of pipelined, approximate sorting."
"We address the new issues pose by nested queries. In particular, the answer space begins with a superset of the final answers and is refined as the aggregates from the inner query blocks are refined. For the intermediary answers to be meaningful, they have to be interpreted with the aggregates from the inner queries. We also propose a multi-threaded model in evaluating such queries: each query block is assigned to a thread, and the threads can be evaluated concurrently and independently. The time slice across the threads is nondeterministic in the sense that the user controls the relative rate at which these subqueries are being evaluated. For enumerative nested queries, we propose a priority-based evaluation strategy to present answers that are certainly in the final answer space first, before presenting those whose validity may be affected as the inner query aggregates are refined. We implemented a prototype system using Java and evaluated our system. Results for nested queries with a level and multiple levels of nesting are reported. Our results show the effectiveness of the proposed mechanisms in providing progressive feedback that reduces the initial waiting time of users significantly without sacrificing the quality of the answers."
"In this article, we present an extended relational algebra with universally or existentially quantified classes as attribute values. The proposed extension can greatly enhance the expressive power of relational systems, and significantly reduce the size of a database, at small additional computational cost. We also show how the proposed extensions can be built on top of a standard relational database system."
"Internet, Web and distributed computing infrastructures continue to gain in popularity as a means of communication for organizations, groups and individuals alike. In such an environment, characterized by large distributed, autonomous, diverse, and dynamic information sources, access to relevant and accurate information is becoming increasingly complex. This complexity is exacerbated by the evolving system, semantic and structural heterogeneity of these potentially global, cross-disciplinary, multicultural and rich-media technologies. Clearly, solutions to these challenges require addressing directly a variety of interoperability issues."
"he ¦Ë-DB OQL compiler is a C++ preprocessor that accepts a language called ¦Ë-OQL, which is C++ code with embedded DML commands to perform transactions, queries, updates, etc. The preprocessor translates ¦Ë-OQL programs into C++ code that contains calls to the ¦Ë-DB evaluation engine. We also provide a visual query formulation interface, called VOODOO, and a translator from visual queries to OQL text, which can be sent to the ¦Ë-DB OQL interpreter for evaluation. Even though a lot of effort has been made to make the implementation of our system simple enough for other database researchers to use and extend, our system is quite sophisticated since it employs current state-of-the-art query optimization technologies as well as new advanced experimental optimization techniques which we have developed through the years, such as query unnesting."
"This paper presents an overview of OLE DB, a set of interfaces being developed at Microsoft whose goal is to enable applications to have uniform access to data stored in DBMS and non-DBMS information containers. Applications will be able to take advantage of the benefits of database technology without having to transfer data from its place of origin to a DBMS. Our approach consists of defining an open, extensible Collection of interfaces that factor and encapsulate orthogonal, reusable portions of DBMS functionality. These interfaces define the boundaries of DBMS components such as record containers, query processors, and transaction coordinators that enable uniform, transactional access to data among such components."
"Several techniques that compute the join between two spatial datasets have been proposed during the last decade. Among these methods, some consider existing indices for the joined inputs, while others treat datasets with no index, providing solutions for the case where at least one input comes as an intermediate result of another database operator. In this paper we analyze previous work on spatial joins and propose a novel algorithm, called slot index spatial join (SISJ), that efficiently computes the spatial join between two inputs, only one of which is indexed by an R-tree. Going one step further, we show how SISJ and other spatial join algorithms can be implemented as operators in a database environment that joins more than two spatial datasets. We study the differences between relational and spatial multiway joins, and propose a dynamic programming algorithm that optimizes the execution of complex spatial queries."
"Our hypothesis is that keyphrases that are automatically extracted from documents can support this aim. We report on a user study that compared how accurately users categorized result documents on small screens when the document surrogates consisted of either keyphrases only, or document titles. We found no significant performance differences between the two conditions. In addition to these encouraging results, keyphrases have the benefit that they can be extracted and presented when no other document metadata can be identified."
"We examine how to apply the hash-join paradigm to spatial joins, and define a new framework for spatial hash-joins. Our spatial partition functions have two components: a set of bucket extents and an assignment function, which may map a data item into multiple buckets. Furthermore, the partition functions for the two input datasets may be different.We have designed and tested a spatial hash-join method based on this framework. The partition function for the inner dataset is initialized by sampling the dataset, and evolves as data are inserted. The partition function for the outer dataset is immutable, but may replicate a data item from the outer dataset into multiple buckets. The method mirrors relational hash-joins in other aspects. Our method needs no pre-computed indices. It is therefore applicable to a wide range of spatial joins.Our experiments show that our method outperforms current spatial join algorithms based on tree matching by a wide margin."
"We propose a file structure to index high-dimensionality data, which are typically points in some feature space. The idea is to use only a few of the features, using additional features only when the additional discriminatory power is absolutely necessary. We present in detail the design of our tree structure and the associated algorithms that handle such ¡°varying length¡± feature vectors. Finally, we report simulation results, comparing the proposed structure with theR*-tree, which is one of the most successful methods for low-dimensionality spaces.The results illustrate the superiority of our method, which saves up to 80% in disk accesses."
"When an update to a view is requested by a user, there may be no unique way of up dating the stored relations in the database to realize the requested update. Chosing one of the alternatives for updating stored relations may not reflect the change that has actually taken place in the real world; in the presence of other derived views, the database may actually present a very wrong model of the world to the user. The problem is even more severe in the case of deductive databases. For avoiding this problem, we introduce a new notion of view updates, called cumulative updates. The key idea behind cumulative updates is that update mechanisms should wait for further update requests to resolve ambiguities. Equivalently, current update requests must also take into account previous requests made to the knowledge base. Cumulative updates, therefore, subsume conventional updates in which only the current update request is considered. In this paper, we motivate the need for cumulative updates and formally define the notion of such updates as well as the different classes therein. We then give methods for computing one particular class of cumulative updates."
"In its seventeenth edition, SBBD 2002 included the presentation of 21 selected papers, 4 tutorials (both invited and selected from submission), 5 mini-courses and 3 invited talks. It congregated more then 450 attendees among researchers, students and practitioners, who contributed to the discussion of research problems, related to the main topics in modern database areas. Being the main national forum for discussions and presentations of research results developed both in Brazil and abroad, the SBBD has held incooperation status from ACM-SIGMOD since 1998. This year, SBBD2002 has also obtained some financial support from the VLDB Endowment."
"SIGMOD has had for the past few years an over-arching vision of enabling all information on the database field to befreelyaccessible toeveryone. Of course, this goal runs smack into the economic realities of scientific publishing. So the SIGMOD Executive Committee over the period of 1997¨C2001 tempered its initial goals to the following strategy, emphasizing free CDROM accessibility first, followed by online accessibility, followed by reduced subscription prices."
"The movement from client-server computing to multi-tier computing has created a potpourri of so-called middleware systems, including application servers, workflow products, EAI systems, ETL systems and federated data systems. In this paper we argue that the explosion in middleware has created a myriad of poorly integrated systems with overlapping functionality. The world would be well served by considerable consolidation, and we present some of the ways this might happen. Some of the points covered in this paper have been previously explored in [BERN96]."
Data security issues today go far beyond the traditional questions of grant/revoke in an RDBMS. We will discuss what the new research agenda should be.
"In this paper, we describe the Oracle Large User Population Demonstration and highlight the scalability mechanisms in the Oracle8 Universal Data Server which make it possible to support as many as 50,000 concurrent users on a single Oracle8 database without any middle-tier TP-monitor software. Supporting such large user populations requires many mechanisms for high concurrency and throughput. Algorithms in all areas of the server ranging from process and buffer management to SQL compilation and execution must be designed to be highly scalable. Efficient resource sharing mechanisms are required to prevent server-side resource requirements from growing unboundedly with the number of users. Parallel execution across multiple systems is necessary to allow user-population and throughput to scale beyond the restrictions of a single system. In addition to scalability, mechanisms for high availability, ease-of-use, and rich functionality are necessary for supporting complex user applications typical of realistic workloads."
"In this paper we present a mechanism for approximately translating Boolean query constraints across heterogeneous information sources. Achieving the best translation is challenging because sources support different constraints for formulating queries, and often these constraints cannot be precisely translated. For instance, a query [score > 8] might be ¡°perfectly¡± translated as [rating > 0.8] at some site, but can only be approximated as [grade = A] at another. Unlike other work, our general framework adopts a customizable ¡°closeness¡± metric for the translation that combines both precision and recall. Our results show that for query translation we need to handle interdependencies among both query conjuncts as well as disjuncts. As the basis, we identify the essential requirements of a rule system for users to encode the mappings for atomic semantic units. Our algorithm then translates complex queries by rewriting them in terms of the semantic units."
"There is a wide array of programming languages available to express user-defined logic. The principal advantage of such an approach is that the workflow logic is kept directly where the workflow data resides, resulting in a more efficient, simpler and more compact system design. It also aids with the embedding of database-centric workflow into a larger framework application, since a DBMS is part of all enterprise applications. Finally, I discuss the advantages and disadvantages of this conceptual approach, and show how additional common workflow features can be added to the current architecture of the Informix Media360 workflow component."
"This paper proposes a different approach, motivated by integrating large numbers of data sources on the Internet. On this ""deep Web,"" we observe two distinguishing characteristics that offer a new view for considering schema matching: First, as the Web scales, there are ample sources that provide structured information in the same domains (e.g., books and automobiles). Second, while sources proliferate, their aggregate schema vocabulary tends to converge at a relatively small size. Motivated by these observations, we propose a new paradigm, statistical schema matching: Unlike traditional approaches using pairwise-attribute correspondence, we take a holistic approach to match all input schemas by finding an underlying generative schema model. We propose a general statistical framework MGS for such hidden model discovery, which consists of hypothesis modeling, generation, and selection."
"To provide high accessibility of continuous-media (CM) data, CM servers generally stripe data across multiple disks. Currently, the most widely used striping scheme for CM data is round-robin permutation (RRP). Unfortunately, when RRP is applied to variable-bit-rate (VBR) CM data, load imbalance across multiple disks occurs, thereby reducing overall system performance. In this paper, the performance of a VBR CM server with RRP is analyzed. In addition, we propose an efficient striping scheme called constant time permutation (CTP), which takes the VBR characteristic into account and obtains a more balanced load than RRP. Analytic models of both RRP and CTP are presented, and the models are verified via trace-driven simulations. Analysis and simulation results show that CTP can substantially increase the number of clients supported, though it might introduce a few seconds/minutes of initial delay."
"To address this problem, we developed Cache Investment - a novel approach for integrating query optimization and data placement that looks beyond the performance of a single query. Cache Investment sometimes intentionally generates a ¡°suboptimal¡± plan for a particular query in the interest of effecting a better data placement for subsequent queries. Cache Investment can be integrated into a distributed database system without changing the internals of the query optimizer. In this paper, we propose Cache Investment mechanisms and policies and analyze their performance. The analysis uses results from both an implementation on the SHORE storage manager and a detailed simulation model. Our results show that Cache Investment can significantly improve the overall performance of a system and demonstrate the trade-offs among various alternative policies."
"The latest, and the subject of this review, is a set of course notes published by the Mineralogical Association of Canada, compiled to accompany a short course on PGE exploration held at the recent PGE Symposium in Oulu, Finland."
"Hello Everyone, I hope you all enjoyed your summer as our thoughts now turn to fall and all the wonders it brings. In this issue, I am responding to several assisted living (AL) nursing concerns we have received regarding advance directives (ADs)."
"Continuous queries over data streams may suffer from blocking operations and/or unbound wait, which may delay answers until some relevant input arrives through the data stream. These delays may turn answers, when they arrive, obsolete to users who sometimes have to make decisions with no help whatsoever. Therefore, it can be useful to provide hypothetical answers - ""given the current information, it is possible that X will become true at time t"" - instead of no information at all."
"As object-oriented model becomes the trend of database technology, there is a need to convert relational to object-oriented database system to improve productivity and flexibility. The changeover includes schema translation, data conversion and program conversion. This paper describes a methodology for integrating schema translation and data conversion. Schema translation involves semantic reconstruction and the mapping of relational schema into object-oriented schema. Data conversion involves unloading tuples of relations into sequential files and reloading them into object-oriented classes files. The methodology preserves the constraints of the relational database by mapping the equivalent data dependencies."
"In this paper, we introduce a new type of integrity constraint, which we call a statistical constraint, and discuss its applicability to enhancing database correctness. Statistical constraints manifest embedded relationships among current attribute values in the database and are characterized by their probabilistic nature. They can be used to detect potential errors not easily detected by the conventional constraints. Methods for extracting statistical constraints from a relation and enforcement of such constraints are described. Preliminary performance evaluation of enforcing statistical constraints on a real life database is also presented."
"While the number of database management systems (DBMSs) increases and the various DBMSs get more and more complex, no uniform method for DBMS construction exists. As a result, developers are forced to start more or less from scratch again for every desired system, resulting in a waste of time, effort, and cost. Hence, the database community is challenged with the development of an appropriate method, i.e. the time-saving application of engineering principles (e.g., reuse). Problems related to a construction method are described, as well as approaches towards solutions."
"In this paper, we study efficient methods for computing iceberg cubes with some popularly used complex measures, such as average, and develop a methodology that adopts a weaker but anti-monotonic condition for testing and pruning search space. In particular, for efficient computation of iceberg cubes with the average measure, we propose a top-k average pruning method and extend two previously studied methods, Apriori and BUC, to Top-k Apriori and Top-k BUC. To further improve the performance, an interesting hypertree structure, called H-tree, is designed and a new iceberg cubing method, called Top-k H-Cubing, is developed. Our performance study shows that Top-k BUC and Top-k H-Cubing are two promising candidates for scalable computation, and Top-k H-Cubing has better performance in most cases."
"Queries navigate semistructured data via path expressions, and can be accelerated using an index. Our solution encodes paths as strings, and inserts those strings into a special index that is highly optimized for long and complex keys. We describe the Index Fabric, an indexing structure that provides the efficiency and flexibility we need. We discuss how ""raw paths"" are used to optimize ad hoc queries over semistructured data, and how ""refined paths"" optimize specific access paths. Although we can use knowledge about the queries and structure of the data to create refined paths, no such knowledge is needed for raw paths."
"We propose a mathematical formulation for the notion of optimal projective cluster, starting from natural requirements on the density of points in subspaces. This allows us to develop a Monte Carlo algorithm for iteratively computing projective clusters. We prove that the computed clusters are good with high probability. We implemented a modified version of the algorithm, using heuristics to speed up computation. Our extensive experiments show that our method is significantly more accurate than previous approaches. In particular, we use our techniques to build a classifier for detecting rotated human faces in cluttered images."
"Databases, the center of today's information systems, are becoming more and more important judging by the huge volume of business they generate. In fact, database related material is included in a variety of curricula proposed by international organizations and prestigious universities. However, a systemized database body of knowledge (DBBOK), analogous to other works in Software Engineering (SWEBOK) or in Project Management (PMBOK) is needed. In this paper, we propose a first draft for this DBBOK based on degree programs from a variety of universities, the most relevant international curricula and the contents of the latest editions of principle books on databases."
"Recent work in data integration has shown the importance of statistical information about the coverage and overlap of sources for efficient query processing. Despite this recognition there are no effective approaches for learning the needed statistics. In this paper we present StatMiner, a system for estimating the coverage and overlap statistics while keeping the needed statistics tightly under control. StatMiner uses a hierarchical classification of the queries, and threshold based variants of familiar data mining techniques to dynamically decide the level of resolution at which to learn the statistics. We will demonstrate the major functionalities of StatMiner and the effectiveness of the learned statistics in BibFinder, a publicly available computer science bibliography mediator we developed. The sources that BibFinder integrates are autonomous and can have uncontrolled coverage and overlap. An important focus in BibFinder was thus to mine coverage and overlap statistics about these sources and to exploit them to improve query processing."
"The tutorial ""Software as a Service: ASP and ASP aggregation"" will give an introduction and overview of the concept of ""renting"" access to software to customers (subscribers). Application service providers (ASPs) are enterprises hosting one or more applications and provide access to subscribers over the Internet by means of browser technology. Furthermore, the underlying technologies are discussed to enable application hosting. The concept of ASP aggregation is introduced to provide a single access point and a single sign-on capability to subscribers sub-scribing to more than one hosted application in more than one ASP."
"DBMS are widely used and successfully applied to a huge range of applications. However the transaction paradigm that is, with variations like nested transactions and workflow systems, the basis for durability and correctness is poorly suited to many modern applications. Transactions do not scale well and behave poorly at high concurrency levels and in distributed systems."
"The summer school tutorial program on New Frontiers in Data Mining was presented under the auspices of DIMACS, the Center for Theoretical Computer Science at Rutgers University. It took place from August 13, 2001 to August 17, 2001 at the DIMACS center at Rutgers. Dimitrios Gunopulos and Nick Koudas were the organizers of the tutorial that included a large list of invited speakers and presenters. The National Science Foundation provided funding for this event. Fred Roberts, the DIMACS director, provided guidance during the course of this work."
"Recently, technological advances have resulted in the wide availability of commercial products offering near-line, robot-based, tertiary storage libraries. Thus, such libraries have become a crucial component of modern largescale storage servers, given the very large storage requirements of modern applications. Although the subject of optimal data placement (ODP) strategies has received considerable attention for other storage devices (such as magnetic and optical disks and disk arrays), the issue of optimal data placement in tertiary libraries has been neglected. The latter issue is more critical since tertiary storage remains three orders of magnitude slower than secondary storage. In this paper, we address this issue by deriving such optimal placement algorithms."
"In this paper, we present a unified framework that can enforce multiple access control policies within a single system. The framework is based on a language through which users can specify security policies to be enforced on specific accesses. The language allows the specification of both positive and negative authorizations and incorporates notions of authorization derivation, conflict resolution, and decision strategies. Different strategies may be applied to different users, groups, objects, or roles, based on the needs of the security policy. The overall result is a flexible and powerful, yet simple, framework that can easily capture many of the traditional access control policies as well as protection requirements that exist in real-world applications, but are seldom supported by existing systems. The major advantage of our approach is that it can be used to specify different access control policies that can all coexist in the same system and be enforced by the same security server."
"This paper presents an algorithm, called ARIES/CSA (Algorithm for Recovery and Isolation Exploiting Semantics for Client-Server Architectures), for performing recovery correctly in client-server (CS) architectures. In CS, the server manages the disk version of the database. The clients, after obtaining database pages from the server, cache them in their buffer pools. Clients perform their updates on the cached pages and produce log records. The log records are buffered locally in virtual storage and later sent to the single log at the server. ARIES/CSA supports a write-ahead logging (WAL), fine-granularity (e.g., record) locking, partial rollbacks and flexible buffer management policies like steal and no-force. It does not require that the clocks on the clients and the server be synchronized. Checkpointing by the server and the clients allows for flexible and easier recovery."
"Relational database systems do not effectively support complex queries containing quantifiers (quantified queries) that are increasingly becoming important in decision support applications. Generalized quantifiers provide an effective way of expressing such queries naturally. In this paper, we consider the problem of processing quantified queries within the generalized quantifier framework. We demonstrate that current relational systems are ill-equipped, both at the language and at the query processing level, to deal with such queries. We also provide insights into the intrinsic difficulties associated with processing such queries. We then describe the implementation of a quantified query processor, Q2P, that is based on multidimensional and boolean matrix structures. We provide results of performance experiments run on Q2P that demonstrate superior performance on quantified queries. Our results indicate that it is feasible to augment relational systems with query subsystems like Q2P for significant performance benefits for quantified queries in decision support applications."
"Database support for multidimensional arrays is an area of growing importance; a variety of highvolume applications such as spatio-temporal data management and statistics/OLAP become focus of academic and market interest. RasDaMan is a domain-independent array database management system with server-based query optimization and evaluation. The system is fully operational and being used in international projects. We will demonstrate spatio-temporal retrieval using the rView visual query client. Examples will encompass 1-D time series, 2-D images, 3-D and 4-D voxel data. The real-life data sets used stem from life sciences, geo sciences, numerical simulation, and climate research."
"The primary session of the workshop took place the morning of the first day. In this session, each of the participants had up to 10 min to deliver a brief message, using just one slide. Researchers were asked to answer the question: ¡®In your view, what is the most urgent, unsolved question/issue in verbal lie detection?¡¯ Similarly, practitioners were asked: ¡®As a practitioner, what question/issue do you wish verbal lie detection research would address?¡¯ The issues raised served as the basis for the discussions that were held throughout the workshop. The current paper first presents the urgent, unsolved issues raised by the workshop group members in the main session, followed by a message to researchers in the field, designed to deliver the insights, decisions, and conclusions resulting from the discussions."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
"Many applications compute aggregate functions (such as COUNT, SUM) over an attribute (or set of attributes) to find aggregate values above some specified threshold. We call such queries iceberg queries because the number of above-threshold results is often very small (the tip of an iceberg), relative to the large amount of input data (the iceberg). Such iceberg queries are common in many applications, including data warehousing, information-retrieval, market basket analysis in data mining, clustering and copy detection. We propose efficient algorithms to evaluate iceberg queries using very little memory and significantly fewer passes over data, as compared to current techniques that use sorting or hashing. We present an experimental case study using over three gigabytes of Web data to illustrate the savings obtained by our algorithms."
"The goal of the Paradise project is to apply object-oriented and parallel database technology to the task of implementing a parallel GIS system capable of managing extremely large (multi-terabyte) data sets such as those that will be produced by the upcoming NASA EOSDIS project [Car92]. The project is focusing its resources on algorithms, processing, and storage techniques, and not on making new contributions to the data modeling, query language, or user interface domains."
"Soon, the world. will need far more truly large databases then any of us ever imagined; yet, ironically, without a lot of care, VLDB¡¯s,as we know them today may be left along the wayside. The way in which we think about, design and build enormous databases will have to completely change if we are to participate in this revolution. By now everybody, including database people, realizes that the computer world is going through not one but two revolutionary changes. First, of course, there¡¯s the wh+e imiact of personal computers, commodity hardwar& and ever increasing speed and capacity. Second, there¡¯s the impact of the internet i put them together,. and the impact is. explosive. This paper deals with the particular impact of this changing world scene on the ckepts behind and implementation of very large databases. By the time we¡¯re done, the meanings of ¡°very¡±, ¡°large¡± and ¡°datab&e¡± will be pret& different than it is today."
"In this paper we present a method for automatically segmenting unformatted text records into structured elements. Several useful data sources today are human-generated as continuous text whereas convenient usage requires the data to be organized as structured records. A prime motivation is the warehouse address cleaning problem of transforming dirty addresses stored in large corporate databases as a single text field into subfields like ¡°City¡± and ¡°Street¡±. Existing tools rely on hand-tuned, domain-specific rule-based systems."
"A matrix comprising a water-insoluble beta -1,3-glucan gel in the shape of beads with diameters within the range of about 5 to 1000 mu is prepared by, for example, dispersing an alkaline aqueous solution of a water-soluble beta -1,3-glucan in a water-immiscible organic solvent, and adding an organic acid to the resultant dispersion. The matrix is useful as carrier materials for immobilized enzymes, affinity chromatography, gel filtration, ion exchange and other applications."
"Together with bit-sliced addition, this permits us to solve a common basic problem of text retrieval: given an object-relational table T of rows representing documents, with a collection type column K representing keyword terms, we demonstrate an efficient algorithm to find k documents that share the largest number of terms with some query list Q of terms. A great deal of published work on such problems exists in the Information Retrieval (IR) field. The algorithm we introduce, which we call Bit-Sliced Term-Matching, or BSTM, uses an approach comparable in performance to the most efficient known IR algorithm, a major improvement on current DBMS text searching algorithms, with the advantage that it uses only indexing we propose for native database operations."
"Those of us who were able to come to our Annual Meeting in Cancun had a most enjoyable time. Thanks to Laurie Levinson, Janet Szydlo, and their Program Committee, the scientific sessions were stimulating and productive ones. Our three English guests ¡ª Mark Solms, Peter Fonagy, and Mary Target ¡ª presented informative and challenging papers and both Peter Blos¡¯ discussion of Solms¡¯ paper and the ensuing discussion groups raised many important issues about the mind-body relationship in psychosomatic conditions in children."
"HYPERQUERY is a hypertext query language for object-oriented pictorial database systems. First, we discuss object calculus based on term rewriting. Then, example queries are used to illustrate language facilities. This query language has been designed with a flavor similar to QBE as the highly nonprocedural and conversational language for object-oriented pictorial database management system OISDBS."
"This paper presents BUCKY, a new benchmark for object-relational database systems. BUCKY is a query-oriented benchmark that tests many of the key features offered by object-relational systems, including row types and inheritance, references and path expressions, sets of atomic values and of references, methods and late binding, and user-defined abstract data types and their methods. To test the maturity of object-relational technology relative to relational technology, we provide both an object-relational version of BUCKY and a relational equivalent thereof (i.e., a relational BUCKY simulation). Finally, we briefly discuss the initial performance results and lessons that resulted from applying BUCKY to one of the early object-relational database system products."
"Based on this probabilistic model, we develop three utility-theoretic based types of prefetching algorithms that anticipate how users will interact with the presentation. These prefetching algorithms allow efficient visualization of the query results in accordance with the underlying specification. We have built a prototype system that incorporates these algorithms. We report on the results of experiments conducted on top of this implementation."
"The problem of data cleaning, which consists of emoving inconsistencies and errors from original data sets, is well known in the area of decision support systems and data warehouses. However, for non-conventional applications, such as the migration of largely unstructured data into structured one, or the integration of heterogeneous scientific data sets in inter-discipl- inary fields (e.g., in environmental science), existing ETL (Extraction Transformation Loading) and data cleaning tools for writing data cleaning programs are insufficient. The main challenge with them is the design of a data flow graph that effectively generates clean data, and can perform efficiently on large sets of input data. The difficulty with them comes from (i) a lack of clear separation between the logical specification of data transformations and their physical implementation and (ii) the lack of explanation of cleaning results and user interaction facilities to tune a data cleaning program."
"Browsing ANd Keyword Searching (BANKS) enables almost effortless Web publishing of relational and eXtensible Markup Language (XML) data that would otherwise remain (at least partially) invisible to the Web. Relational databases store large amounts of data that are queried using structured query languages. A user needs to know the underlying schema and the query language in order to make meaningful ad hoc queries on the data. This is a substantial barrier for casual users, such as users of Web-based information systems. HTML forms can be provided for predefined queries. A university Website may provide a form interface to search for faculty and students. Searching for departments would require yet another form, as would search for courses offered. However, creating an interface for each such task is laborious, and is also confusing to users since they must first expend effort finding which form to use. search can provide a very simple and easy-to-use mechanism for casual users to get information from databases."
"Garbage collection is important in object-oriented databases to free the programmer from explicitly deallocating memory. In this paper, we present a garbage collection algorithm, called Transactional Cyclic Reference Counting (TCRC), for object-oriented databases. The algorithm is based on a variant of a reference-counting algorithm proposed for functional programming languages The algorithm keeps track of auxiliary reference count information to detect and collect cyclic garbage. The algorithm works correctly in the presence of concurrently running transactions, and system failures. It does not obtain any long-term locks, thereby minimizing interference with transaction processing. It uses recovery subsystem logs to detect pointer updates; thus, existing code need not be rewritten."
"To overcome the verbosity problem, the research on compressors for XML data has been conducted. However, some XML compressors do not support querying compressed data, while other XML compressors which support querying compressed data blindly encode tags and data values using predefined encoding methods. Thus, the query performance on compressed XML data is degraded.In this paper, we propose XPRESS, an XML compressor which supports direct and efficient evaluations of queries on compressed XML data. XPRESS adopts a novel encoding method, called reverse arithmetic encoding, which is intended for encoding label paths of XML data, and applies diverse encoding methods depending on the types of data values."
"While the desire to support fast, ad hoc query processing for large data warehouses has motivated the recent introduction of many new indexing structures, with a few notable exceptions (namely, the LSM-Tree and the Stepped Merge Method) little attention has been given to developing new indexing schemes that allow fast insertions. Since additions to a large warehouse may number in the millions per day, indices that require a disk seek (or even a significant fraction of a seek) per insertion are not acceptable. In this paper, we offer an alternative to the B+-tree called the Y-tree for indexing huge warehouses having frequent insertions. The Y-tree is a new indexing structure supporting both point and range queries over a single attribute, with retrieval performance comparable to the B+-tree. For processing insertions, however, the Y-tree may exhibit a speedup of 100 times over batched insertions into a B+-tree."
"trees that minimize the computation and communication costs of parallel execution. We address the problem of finding parallel plans for SQL queries using the two-phase approach of join ordering and query rewrite (JOQR) followed by parallelization. We focus on the JOQR phase and develop optimization algorithms that account for communication as well as computation costs. Using a model based on representing the partitioning of data as a color, we devise an efficient algorithm for the problem of choosing the partitioning attributes in a query tree so as to minimize total cost. We extend our model and algorithm to incorporate the interaction of data partitioning with conventional optimization choices such as access methods and strategies for computing operators. Our algorithms apply to queries that include operators such as grouping, aggregation, intersection and set difference in addition to joins."
"Four degradation patterns were determined objectively through the clustering approach, each of which showed similar trends and characteristics. Based on the distribution of clusters, interval 2 was determined to have the worst overall condition. The LSTM network was used for performance prediction in each cluster. Compared with the traditional multilayer neural network, the LSTM also exhibited good prediction effectiveness. The predicted data are well consistent with the observed data with correlation coefficient R2 equaling to 88.4%."
"We propose a solution that eliminates the need of such a trusted authority. The solution builds a centralized privacy-preserving index in conjunction with a distributed access-control enforcing search protocol. Two alternative methods to build the centralized index are proposed, allowing trade offs of efficiency and security. The new index provides strong and quantifiable privacy guarantees that hold even if the entire index is made public. Experiments on a real-life dataset validate performance of the scheme. The appeal of our solution is twofold: (a) content providers maintain complete control in defining access groups and ensuring its compliance, and (b) system implementors retain tunable knobs to balance privacy and efficiency concerns for their particular domains."
"To address these limitations of the current restructuring technology, we have proposed the SERF framework which aims at providing a rich environment for doing complex user-defined transformations flexibly, easily and correctly. The goal of our work is to increase the usability and utility of the SERF framework and its applicability to re-structuring problems beyond OODB evolution. Towards that end, we provide re-usable transformations via the notion of SERF Templates that can be packaged into libraries, thereby increasing the portability of these transformations. We also now have a first cut at providing an assurance of consistency for the users of this system, a semantic optimizer that provides some performance improvements via enhanced query optimization techniques with emphasis on the re-structuring primitives. In this demo we give an overview of the SERF framework, its current status and the enhancements that are planned for the future. We also present an example of the application of SERF to a domain other than schema evolution, i.e., the web restructuring."
"The article proposes a scalable protocol for replication management in large-scale replicated systems. The protocol organizes sites and data replicas into a tree-structured, hierarchical cluster architecture. The basic idea of the protocol is to accomplish the complex task of updating replicated data with a very large number of replicas by a set of related but independently committed transactions. Each transaction is responsible for updating replicas in exactly one cluster and invoking additional transactions for member clusters. Primary copies (one from each cluster) are updated by a cross-cluster transaction. Then each cluster is independently updated by a separate transaction. This decoupled update propagation process results in possible multiple views of replicated data in a cluster. Compared to other replicated data management protocols, the proposed protocol has several unique advantages."
"Building such a database system requires fundamental changes in the architecture of the query processing engine; we present the system-level interfaces of PREDATOR that support E-ADTs, and describe the internal design details."
"The contents of many valuable web-accessible databases are only accessible through search interfaces and are hence invisible to traditional web ¡°crawlers.¡± Recent studies have estimated the size of this ¡°hidden web¡± to be 500 billion pages, while the size of the ¡°crawlable¡± web is only an estimated two billion pages. Recently, commercial web sites have started to manually organize web-accessible databases into Yahoo!-like hierarchical classification schemes. In this paper, we introduce a method for automating this classification process by using a small number of query probes. To classify a database, our algorithm does not retrieve or inspect any documents or pages from the database, but rather just exploits the number of matches that each query probe generates at the database in question. We have conducted an extensive experimental evaluation of our technique over collections of real documents, including over one hundred web-accessible databases."
"We present an approach to database interoperation that exploits the semantic information provided by integrity constraints defined on the component databases. We identify two roles of integrity constraints in database interoperation. First, a set of integrity constraints describing valid states of the integrated view can be derived from the constraints defined on the underlying databases. Moreover, local integrity constraints can be used as a semantic check on the validity of the specification of the integrated view. We illustrate our ideas in the context of an instance-based database interoperation paradigm, where objects rather than classes are the unit of integration. We introduce the notions of objectivity and subjectivity as an indication of whether a constraint is valid beyond the context of a specific database, and demonstrate the impact of these notions."
"A new access method, called M-tree, is proposed to organize and search large data sets from a generic ¡°metric space¡±, i.e. where object proximity is only defined by a distance function satisfying the positivity, symmetry, and triangle inequality postulates. We detail algorithms for insertion of objects and split management, which keep the M-tree always balanced - several heuristic split alternatives are considered and experimentally evaluated. Algorithms for similarity (range and k-nearest neighbors) queries are also described. Results from extensive experimentation with a prototype system are reported, considering as the performance criteria the number of page I/O¡¯s and the number of distance computations. The results demonstrate that the Mtree indeed extends the domain of applicability beyond the traditional vector spaces, performs reasonably well in high-dimensional data spaces, and scales well in case of growing files."
"The PMG offers the user one of the possible path-methods and the user verifies from his knowledge of the intended purpose of the request whether that path-method is the desired one. If the path method is rejected, then the user can utilize his now increased knowledge about the database to request (with additional parameters given) another offer from the PMG. The PMG is based on access weights attached to the connections between classes and precomputed access relevance between every pair of classes of the OODB. Specific rules for access weight assignment and algorithms for computing access relevance appeared in our previous papers [MGPF92, MGPF93, MGPF96]. In this paper, we present a variety of traversal algorithms based on access weights and precomputed access relevance. Experiments identify some of these algorithms as very successful in generating most desired path-methods. The PMG system utilizes these successful algorithms and is thus an efficient tool for aiding the user with the difficult task of querying and updating a large OODB."
"Metadata has been identified as a key success factor in data warehouse projects. It captures all kinds of information necessary to analyse, design, build, use, and interpret the data warehouse contents. In order to spread the use of metadata, enable the interoperability between repositories, and tool integration within data warehousing architectures, a standard for metadata representation and exchange is needed. This paper considers two standards and compares them according to specific areas of interest within data warehousing. Despite their incontestable similarities, there are significant differences between the two standards which would make their unification difficult."
"Language comprehension and production are generally assumed to use the same representations, but resumption poses a problem for this view: This structure is regularly produced, but judged highly unacceptable. Production-based solutions to this paradox explain resumption in terms of processing pressures, whereas the Facilitation Hypothesis suggests resumption is produced to help listeners comprehend."
"In this paper, we propose a bulk-algebra, TIX, and describe how it can be used as a basis for integrating information retrieval techniques into a standard pipelined database query evaluation engine."
". In more deteil, we use a sliding window over the data sequence and extract its features; the result is a trail in feature space. We propose an efficient and effective algorithm to divide such trails into sub-trails, which are subsequently represented by their Minimum Bounding Rectangles (MBRs). We develop new evaluation strategies essential to obtaining good performance, including a stack-based TermJoin algorithm for efficiently scoring composite elements. We report results from an extensive experimental evaluation, which show, among other things, that the new TermJoin access method outperforms a direct implementation of the same functionality using standard operators by a large factor."
An increasing number of database applications demands high availability combined with online scalability and soft real-time transaction response. This means that scaling must be done online and non-blocking. This paper extends the primary/hot standby approach to high availability with online scaling operations. The challenges are to do this without degrading the response time and throughput of transactions and to support high availability throughout the scaling period. We measure the impact of online scaling on response time and throughput using di erent scheduling schemes. We also show some of the recovery problems that appear in this setting.
"Computing multidimensional aggregates in high dimensions is a performance bottleneck for many OLAP applications. Obtaining the exact answer to an aggregation query can be prohibitively expensive in terms of time and/or storage space in a data warehouse environment. It is advantageous to have fast, approximate answers to OLAP aggregation queries."
"The increasing usage of Web services on the Internet has led to much interest in the area of service discovery. Web Service Discovery is the process of locating a machine-process able description of a web service that may previously unknown and that meets certain functional criteria. In industry, many applications are built by calling different web services available on internet. These applications are highly dependent on discovering correct and efficient web service. This paper gives overview of the web services discovery process from multidimensional view."
"We present algorithms for performing backup and recovery of the DBMS data in a coordinated fashion with the files on the file servers. Our algorithms for coordinated backup and recovery have been implemented in the IBM DB2/DataLinks product. We also propose an efficient solution to the problem of maintaining consistency between the content of a file and the associated meta-data stored in the DBMS from a reader's point of view without holding long duration locks on meta-data tables. In the model, an object is directly accessed and edited in-place through normal file system APIs using a reference obtained via an SQL Query on the database. To relate file modifications to meta-data updates, the user issues an update through the DBMS, and commits both file and meta-data updates together."
"The aim of this workshop was to bring together researchers from academia and industry as well as practitioners to discuss views on how to integrate semantics into current geographic information systems, and how this will benefit the end users. The workshop was organized in a way to highly stimulate interaction among the participants. Three or four experts from the same or a closely related discipline to the authors reviewed each of the 32 submissions. I would like to sincerely thank the Program Committee and the additional experts who realized an excellent work in carefully reviewing the papers: they made a strong contribution to the quality of the workshop."
"Mainstream database management systems are designed for general use. Various compromises have been done to satisfy the most common users and the largest markets. One application which has been mostly ignored, is the network equipment made for the telco operators. The equipment used in the telco industry has requirements differing from traditional database applications with respect to availability and real-time performance."
"This chapter presents a generic technique called progressive merge join (PMJ) that eliminates the blocking behavior of sort-based join algorithms. The basic idea behind PMJ is to have the join produce results, as early as the external mergesort generates initial runs. Many state-of-the-art join techniques require the input relations to be almost fully sorted before the actual join processing starts. Thus, these techniques start producing first results only after a considerable time has passed. This blocking behavior is a serious problem when consequent operators have to stop processing in order to wait for first results of the join. Furthermore, this behavior is not acceptable if the result of the join is visualized or/and requires user interaction. These are typical scenarios for data mining applications. The off-time of existing techniques even increases with growing problem sizes."
We describe the implementation of the magic-sets transformation in the Starburst extensible relational database system. To our knowledge this is the first implementation of the magic-sets transformation in a relational database system. The Starburst implementation has many novel features that make our implementation especially interesting to database practitioners (in addition to database researchers).
"In traditional software systems, significant attention is devoted to keeping modules well separated and coherent with respect to functionality, thus ensuring that changes in the system are localized to a handful of modules. Reuse is seen as the key method in reaching that goal. Ontology-based systems on the Semantic Web are just a special class of software systems, so the same principles apply. In this article, we present an integrated framework for managing multiple and distributed ontologies on the Semant ic Web."
"Outlier detection is an integral component of statistical modelling and estimation. For high-dimensional data, classical methods based on the Mahalanobis distance are usually not applicable. We propose an outlier detection procedure that replaces the classical minimum covariance determinant estimator with a high-breakdown minimum diagonal product estimator. The cut-off value is obtained from the asymptotic distribution of the distance, which enables us to control the Type I error and deliver robust outlier detection. Simulation studies show that the proposed method behaves well for high-dimensional data."
"The results show that there are both performance and energy trade-offs between the indexing schemes for the different queries. The nature of the query also plays an important role in determining the energy-performance trade-offs. Further, technological trends and architectural enhancements are influencing factors on the relative behavior of the index structures. The work in the query has a bearing on how and where (on a mobile client or/and on a server) it should be performed for performance and energy savings."
"A novel execution model for rule application in active databases is developed and applied to the problem of updating derived data in a database represented using a semantic, object-based database model. The execution model is based on the use of ¡°limited ambiguity rules¡± (LARs), which permit disjunction in rule actions. The execution model essentially performs a breadth-first exploration of alternative extensions of a user-requested update. Given an object-based database schema, both integrity constraints and specifications of derived classes and attributes are compiled into a family of limited ambiguity rules. A theoretical analysis shows that the approach is sound: the execution model returns all valid ¡°completions¡± of a user-requested update, or terminates with an appropriate error notification. The complexity of the approach in connection with derived data update is considered."
"This chapter reveals that the loader and compressor convert XML documents in a compressed, yet queryable format. The compressed repository stores the compressed documents and provides: access methods to this compressed data, and a set of compression-specific utilities that enable, e.g., the comparison of two compressed values. The query processor optimizes and evaluates XQuery queries over the compressed documents. Its complete set of physical operators allows for efficient evaluation over the compressed repository. The chapter motivates the choice of the storage structures for compressed XML, and of the compression algorithms employed. It describes the XQueC query processor, its set of physical operators, and outlines its optimization algorithm."
"Overall performance can be improved by algorithms that enable operations to adjust their memory usage at run time in response to the actual size of their inputs and fluctuations in total memory demand. Sorting is a frequent operation in database systems. It is used not only to produce sorted output, but also in many sort-based algorithms, such as grouping with aggregation, duplicate removal, sort-merge join and set operations. Sorting can also improve the efficiency of algorithms like nested-loop joins and row retrieval via an index. This paper concentrates on dynamic memory adjustment for sorting but the same approach can be applied to other memory intensive operations."
"The FileNet Integrated Document Management (IDM) products consists of a family of client applications and Imaging and Electronic Document Management (EDM) services. These services provide robust facilities for document creation, update, and deletion along with document search capabilities. Document properties are stored in an underlying relational database (RDBMS); document content is stored in files or in a specialized optical disk hierarchical storage manager. FileNet Corporation's Visual WorkFlo? and Ensemble? workflow products can be utilized in conjunction with FileNet's IDM technologies to automate production and ad hoc business processes respectively."
"Computers running database management applications often manage large amounts of data. Typically, the price of the I/O subsystem is a considerable portion of the computing hardware. Fierce price competition demands every possible savings. Lossless data compression methods, when appropriately integrated with the dbms, yield signiflcant savings. Roughly speaking, a slight increase in cpu cycles is more than offset by savings in I/O subsystem. Various design issues arise in the use of data compression in the dbms from the choice of algorithm, statistics collection, hardware versus software based compression, location of the compression function in the overall computer system architecture, unit of compression, update in place, and the application of log¡¯ to compressed data."
"We represent the occurrence time of an event with a set of possible instants, delimiting when the event might have occurred, and a probability distribution over that set. We also describe query language constructs to retrieve information in the presence of indeterminacy. These constructs enable users to specify their credibility in the underlying data and their plausibility in the relationships among that data. A denotational semantics for SQL's select statement with optional credibility and plausibility constructs is given. We show that this semantics is reliable, in that it never produces incorrect information, is maximal, in that if it were extended to be more informative, the results may not be reliable, and reduces to the previous semantics when there is no indeterminacy. Although the extended data model and query language provide needed modeling capabilities, these extensions appear initially to carry a significant execution cost. A contribution of this paper is to demonstrate that our approach is useful and practical."
"There is a new emerging world of web services. In this world, services will be combined in innovative ways to form elaborate services out of building blocks of other services. This is predicated on having a common ground of vocabulary and communication protocols operating in a secured environment. Currently, massive standardization efforts [UDDI, WSDL, ebXML, RosettaNet] are aiming at achieving this common ground. We explore possible architectures for deploying computerized traders internal services. This encompasses both the structure and the functionalities of ¡°traders¡± and ¡°services¡± and the form in which these functionalities could be realized in actual implementations."
"In a recent paper, we proposed adding aSTOP AFTER clause to SQL to permit the cardinality of a query result to be explicitly limited by query writers and query tools. We demonstrated the usefulness of having this clause, showed how to extend a traditional cost-based query optimizer to accommodateit, and demonstrated via DB2-basedsimulations that large performancegains are possible whenSTOP AFTER queries are explicitly supported by the database engine. In this paper, we present several new strategies for efficiently processing STOP AFTER queries. These strategies, based largely on the use of range partitioning techniques, offer significant additional savings for handling STOP AFTER queries that yield sizeable result sets. We describe classes of queries where such savings would indeed arise and present experimental measurements that show the benefits and tradeoffs associated with the new processing strategies"
"Data replication has recently become a topic of increased interest among customers. Several database vendors provide products that perform data replication, The capabilities of these products and the customer problems they solve vary widely. This talk starts by identifying some of the dimensions of the replication solution space including latency, concurrency, logical and physical units of replication, network link requirements, heterogeneity, replica topology, replica transparency, and data transformation requirements. Digital Equipment Corporation provides three products that allow customers to replicate data. The distributed, two-phase commit products allow customers to program and coordinate replicated updates. DECTM Reliable Transaction Router provides an OLTP environment with transactional data replication. Transactions succeed in the face of site and network failures."
"This paper proposes a cache-conscious version of the R-tree called the CR-tree. To pack more entries in a node, the CR-tree compresses MBR keys, which occupy almost 80% of index data in the two-dimensional case. It first represents the coordinates of an MBR key relatively to the lower left corner of its parent MBR to eliminate the leading O's from the relative coordinate representation. Then, it quantizes the relative coordinates with a fixed number of bits to further cut off the trailing less significant bits. Consequently, the CR-tree becomes significantly wider and smaller than the ordinary R-tree."
"The customization of Web to find out the confidence of Web page in the community graph and to calculate the page rank of the pages in the graph, is described. The confidence factor of the page plays significant role in page ranking. Web can be efficiently traversed in search of pages related with specific topic, if viewed from the search topic perspective. Customizing the graph to the graph of pages with only relevant features, removes the citations from the irrelevant pages and hence uses only the relevant weight for calculating page rank."
"This paper discusses the design and implementation of SEQ, a database system with support for sequence data. SEQ models a sequence as an ordered collection of records, and supports a declarative sequence query language based on an algebra of query operators, thereby permitting algebraic query optimization and evaluation. SEQ has been built as a component of the PREDATOR database system that provides support for relational and other kinds of complex data as well. that could describe a wide variety of sequence data, and a query algebra that could be used to represent queries over sequences."
"Data warehousing is the latest ¡°hot topic¡± in the industry. With market projections of $8 billion by the year 2000, vendors of all flavors are claiming the suitability and superiority of their products for this market segment. This has led to a great deal of confusion, with terms such as OLAP, ROLAP, MDDB, decision support systems (DSS) and data warehousing being defined, re-defined, and sometimes even used interchangeably."
"In this paper, we introduce a multi-agent system architecture and an implemented prototype for software component market-place. We emphasize the ontological perspective by discussing the ontology modeling for component market-place, UML extensions for ontology modeling, and the idea of ontology transfer which makes the multi-agent system to adapt itself to the dynamically changing ontologies."
"Opening a series of concrete works to follow, this vision paper identifies, motivates, and abstracts the problem of model management. It proposes to support ¡°models¡± and their ¡°mapping¡± as first-class constructs, with high-level algebraic operations to manipulate. In the winter of 2000, I was a starting faculty at UIUC, and this paper inspired me immensely at the time when I had to create a research agenda of my own. I have always been interested in information integration, on various topics like query translation and data mapping. The area was exciting to me, as it was full of ¡°real-world¡± problems. However, it was also not hard to see that these problems seemed inherently messy and their solutions inherently heuristic. Probably because many problems remained unsolved, most research works were only able to address separate topics, without a clear context of an overall application."
"This article investigates the minimization problem for a wide fragment of XPath (namely X P[?]), where the use of the most common operators (child, descendant, wildcard and branching) is allowed with some syntactic restrictions. The examined fragment consists of expressions which have not been specifically studied in the relational setting before: neither are they mere conjunctive queries (as the combination of ¡°//¡± and ¡°*¡± enables an implicit form of disjunction to be expressed) nor do they coincide with disjunctive ones (as the latter are more expressive). Three main contributions are provided. The ¡°global minimality¡± property is shown to hold: the minimization of a given XPath expression can be accomplished by removing pieces of the expression, without having to re-formulate it (as for ¡°general¡± disjunctive queries). Then, the complexity of the minimization problem is characterized, showing that it is the same as the containment problem. Finally, specific forms of XPath expressions are identified, which can be minimized in polynomial time."
"Performance needs of many database applications dictate that the entire database be stored in main memory. The Dali system is a main memory storage manager designed to provide the persistence, availability and safety guarantees one typically expects from a diskresident database, while at the same time providing very high performance by virtue of being tuned to support in-memory data. Dali follows the philosophy of treating all data, including system data, uniformly as database files that can be memory mapped and directly accessed/updated by user processes. Direct access provides high performance; slower, but more secure, access is also provided through the use of a server process."
"This paper describes alternative methods for data access that are available to developers using the Java#8482; platform and related technologies to create a new generation of enterprise applications. The paper highlights industry trends and describes Java technologies that are responsible for a new paradigm in data access. Java technology represents a new level of portability, scalability, and ease-of-use for applications that require data access."
"To ease schema evolution, we propose to support exceptions to the behavioral consistency rules without sacrificing type safety. The basic idea is to detect unsafe statements in a method code at compile-time and check them at run-time. The run-time check is performed by a specific clause that is automatically inserted around unsafe statements. This check clause warns the programmer of the safety problem and lets him provide exception-handling code. Schema updates can therefore be performed with only minor changes to the code of methods."
"In the past decade, advances in the speed of commodity CPUs have far out-paced advances in memory latency. Main-memory access is therefore increasingly a performance bottleneck for many computer applications, including database systems. In this article, we use a simple scan test to show the severe impact of this bottleneck. The insights gained are translated into guidelines for database architecture, in terms of both data structures and algorithms. We discuss how vertically fragmented data structures optimize cache performance on sequential data access. We then focus on equi-join, typically a random-access operation, and introduce radix algorithms for partitioned hash-join. The performance of these algorithms is quantified using a detailed analytical model that incorporates memory access cost. Experiments that validate this model were performed on the Monet database system. We obtained exact statistics on events such as TLB misses and L1 and L2 cache misses by using hardware performance counters found in modern CPUs. Using our cost model, we show how the carefully tuned memory access pattern of our radix algorithms makes them perform well, which is confirmed by experimental results."
"The design of a distributed deductive database system differs from the design of conventional non-distributed deductive database systems in that it requires design of distribution of both the database and rulebase. In this paper, we address the rule allocation problem. We consider minimisation of data communic& tion cost during rule execution as a primary basis for rule allocation. The rule allocation problem can be stated in terms of a directed acyclic graph, where nodes represent rules or relations, and edges represent either dependencies between rules or usage of relations by rules. The arcs are given weights representing volume of data that need to flow between the connected nodes. We show that rule allocation problem is NP-complete. Next, we propose a heuristic for nonreplicated allocation based on successively combining adjacent nodes for placement at same site which are connected by highest weight edge, and study its performance vib*vis the enumerative algorithm for optimal allocation."
"The present paper introduces techniques that solve this problem. Experience with a working prototype optimizer demonstrates (i) that the additional optimization and start-up overhead of dynamic plans compared to static plans is dominated by their advantage at run-time, (ii) that dynamic plans are as robust as the ¡°brute-force¡± remedy of run-time optimization, i.e., dynamic plans maintain their optimality even if parameters change between compile-time and run-time, and (iii) that the start-up overhead of dynamic plans is significantly less than the time required for complete optimization at run-time. In other words, our proposed techniques are superior to both techniques considered to-date, namely compile-time optimization into a single static plan as well as run-time optimization. Finally, we believe that the concepts and technology described can be transferred to commercial query optimizers in order to improve the performance of embedded queries with host variables in the query predicate and to adapt to run-time system loads unpredictable at compile time."
"We present an approach to searching genetic DNA sequences using an adaptation of the sufx tree data structure deployed on the general purpose persistent Java platform, PJama. Our implementation technique is novel, in that it allows us to build su x trees on disk for arbitrarily large sequences, for instance for the longest human chromosome consisting of 263 million letters. We propose to use such indexes as an alternative to the current practice of serial scanning. We describe our tree creation algorithm, analyse the performance of our index, and discuss the interplay of the data structure with object store architectures. Early measurements are presented."
"In contrast, our method has been optimized based on the special properties of high-dimensional spaces and therefore provides a near-optimal distribution of the data items among the disks. The basic idea of our data declustering technique is to assign the buckets corresponding to different quadrants of the data space to different disks. We show that our technique - in contrast to other declustering methods - guarantees that all buckets corresponding to neighboring quadrants are assigned to different disks. We evaluate our method using large amounts of real data (up to 40 MBytes) and compare it with the best known data declustering method, the Hilbert curve."
"Analysis of expected and experimental results of various join algorithms show that a combination of the optimal nested block and optimal GRACE hash join algorithms usually provide the greatest cost benefit, unless the relation size is a small multiple of the memory size. Algorithms to quickly determine a buffer allocation producing the minimal cost for each of these algorithms are presented. When the relation size is a small multiple of the amount of main memory available (typically up to three to six times), the hybrid hash join algorithm is preferable."
"We study various kinds of operations in a database context, and show how the inner loop of the operations can be accelerated using SIMD instructions. The use of SIMD instructions has two immediate performance benefits: It allows a degree of parallelism, so that many operands can be processed at once. It also often leads to the elimination of conditional branch instructions, reducing branch mispredictions.We consider the most important database operations, including sequential scans, aggregation, index operations, and joins. We present techniques for implementing these using SIMD instructions. We show that there are significant benefits in redesigning traditional query processing algorithms so that they can make better use of SIMD technology."
"In this paper, we describe an approximation technique that reduces the storage cost of the cube without incurring the run time cost of lazy evaluation. The idea is to provide an incomplete description of the cube and a method of estimating the missing entries with a certain level of accuracy. The description, of course, should take a fraction of the space of the full cube and the estimation procedure should be faster than computing the data from the underlying relations. Since cubes are used to support data analysis and analysts are rarely interested in the precise values of the aggregates (but rather in trends), providing approximate answers is, in most cases, a satisfactory compromise."
"Database management is one of the main areas of research of the School of Computer Science at The University of Oklahoma (OU). The objective of the database research team at OU (OUDB) is to help solve the many issues and challenges facing the database research community, especially with respect to emerging technology. Currently, many projects are being conducted in the following areas: real-time databases, object-oriented databases, mobile databases, multimedia databases, data mining and data warehouses. These projects have been funded by federal and state agencies as well as private industries such as National Science Foundation, the U.S. Department of Education, Oklahoma State Department of Environmental Quality, and Objectivity, Inc."
"We follow the stack-baaed approach to query languages which is a new formal and intellectual paradigm for integrating querying and programming for object-oriented databases. Queries are considered generalized programing expressions which may be used within macroscopic imperative statements, such as creating, updating, inserting, and deleting data objects. Queries may be also used as procedures¡¯ parameters, as well as determine the output from functional procedures (SQL-like views). The semantics, including generalized query operators (selection, projection, navigation, join, quantifiers, etc.), is defined in terms of operations on two stacks. The environment stack deals with the scope control and binding names."
"The purpose of a textual database is to store textual documents. These documents have not only textual contents, but also structure. Many traditional text database systems have focused only on querying by contents or by structure. Recently, a number of models integrating both types of queries have appeared. We argue in favor of that integration, and focus our attention on these recent models, covering a representative sampling of the proposals in the field. We pay special attention to the tradeoffs between expressiveness and efficiency, showing the compromises taken by the models. We argue in favor of achieving a good compromise, since being weak in any of these two aspects makes the model useless for many applications."
"Recent work in query optimization has addressed the issue of placing expensive predicates in a query plan. In this paper we explore the predicate placement options considered in the Montage DBMS, presenting a family of algorithms that form successively more complex and effective optimization solutions. Through analysis and performance measurements of Montage SQL queries, we classify queries and highlight the simplest solution that will optimize each class correctly. We demonstrate limitations of previously published algorithms, and discuss the challenges and feasibility of implementing the various algorithms in a commercial-grade system."
"In this paper, we explore an approach of interleaving a bushy execution tree with hash filters to improve the execution of multi-join queries. Similar to semi-joins in distributed query processing, hash filters can be applied to eliminate non-matching tuples from joining relations before the execution of a join, thus reducing the join cost. Note that hash filters built in different execution stages of a bushy tree can have different costs and effects. The effect of hash filters is evaluated first. Then, an efficient scheme to determine an effective sequence of hash filters for a bushy execution tree is developed, where hash filters are built and applied based on the join sequence specified in the bushy tree so that not only is the reduction effect optimized but also the cost associated is minimized. Various schemes using hash filters are implemented and evaluated via simulation."
"The MultiView Project is an ongoing 5-year NFS-ftrnded effort at the University of Michigan to develop and apply object-oriented view technology to address the needs of recently emerging applications such as data warehousing and workflow management systems that require the sharing, virtual restructuring, and caching of data [5]. Through Multi-View, users can dynamically create and modify virtual classes and schemata at any time ."
"In this paper, we present two algorithms for deriving optimal and near-optimal vertical class partitioning schemes. The cost-driven algorithm provides the optimal vertical class partitioning schemes by enumerating, exhaustively, all the schemes and calculating the number of disk accesses required to execute a given set of applications. For this, a cost model for executing a set of methods in an OODB system is developed. Since exhaustive enumeration is costly and only works for classes with a small number of instance variables, a hill-climbing heuristic algorithm (HCHA) is developed, which takes the solution provided by the affinity-based algorithm and improves it, thereby further reducing the total number of disk accesses incurred."
"In this paper, we develop the core of a formal data model for network directories, and propose a sequence of efficiently computable query languages with increasing expressive power. The directory data model can naturally represent rich forms of heterogeneity exhibited in the real world. Answers to queries expressible in our query languages can exhibit the same kinds of heterogeneity. We present external memory algorithms for the evaluation of queries posed in our directory query languages, and prove the efficiency of each algorithm in terms of its I/O complexity. Our data model and query languages share the flexibility and utility of the recent proposals for semi-structured data models, while at the same time effectively addressing the specific needs of network directory applications, which we demonstrate by means of a representative real-life example."
"In this paper we describe the architecture and interface of KODA, a production strength database kernel. KODA is unique in the industry in its ability to support two different data models viz. Oracle Rdb (a relational database system) and Oracle CODASYL DBMS (a CODASYL database system). Our experience in designing and implementing KODA demonstrates . the feasibility of implementing multiple data models on top of a common kernel, l the benefits of leveraging performance and feature enhancements for multiple products, . the benefits of maintainability of a common code base, . ease of migration and interoperability between the two products without customers having to re-learn common kernel utilities like backups, data file organization and analysis tools."
"When building a database, it is mandatory to design a friendly interface, which allo ws the nal user to easily access the data of interest. V ery often,such an interface exploits the pow er of visualization and direct manipulation mechanisms. How ever, it is not su?cient to associate \any"" visual represen tation to a database, but the visual representation should be carefully chosen to e ectively con vey all and only the database information content. We are curren tly w orkingon a general theory (see ) for establishing the adequacy of a visual representation, once speci ed the database characteristics, and we are developing a system, called D ARE: Drawing Adequate REpresentations, which implements such a theory."
"Data streams are a new class of data that is becoming pervasively important in a wide range of applications, ranging from sensor networks, environmental monitoring to finance. In this article, we propose a novel framework for the online diagnosis of evolution of multidimensional streaming data that incorporates Recursive Wavelet Density Estimators into the context of Velocity Density Estimation. In the proposed framework changes in streaming data are characterized by the use of local and global evolution coefficients. In addition, we propose for the analysis of changes in the correlation structure of the data a recursive implementation of the Pearson correlation coefficient using exponential discounting."
"In this paper, we introduce a formalism for expressing and reasoning about order properties: ordering and grouping constraints that hold of physical representations of relations. In so doing, we can reason about how the relation is ordered or grouped, both in terms of primary and secondary orders. After formally defining order properties, we introduce a plan refinement algorithm that infers order properties for intermediate and final query results on the basis of those known to hold of query inputs, and then exploits these inferences to avoid unnecessary sorting and grouping."
"Multimedia data mining is the mining of high-level multimedia information and knowledge from large multimedia databases. A multimedia data mining system prototype, MultiMediaMiner, has been designed and developed. It includes the construction of a multimedia data cube which facilitates multiple dimensional analysis of multimedia data, primarily based on visual content, and the mining of multiple kinds of knowledge, including summarization, comparison, classification, association, and clustering."
"Bitmaps are popular indexes for data warehouse (DW) applications and most database management systems offer them today. This paper proposes query optimization strategies for selections using bitmaps. Both continuous and discrete selection criteria are considered. Query optimization strategies are categorized into static and dynamic. Static optimization strategies discussed are the optimal design of bitmaps, and algorithms based on tree and logical reduction. The dynamic optimization discussed is the approach of inclusion and exclusion for both bit-sliced indexes and encoded bitmap indexes."
"In this column, we review these three books."
"I first came across the AMS paper when I started getting interested in the data-streaming area, in the spring of 2001. Reading this paper was a real eye-opener for me. It was just amazing to see how simple randomization ideas and basic probabilistic tools (like the Chebyshev inequality and the Chernoff bound) can come together to provide elegant, space-efficient randomized approximation algorithms for estimation problems that, at first glance, would seem impossible to solve. The second-moment method described in the AMS paper is essentially the father of all ¡°sketch-based¡± techniques for data-stream management."
"The World-Wide Web (WWW) is an ever growing, distributed, non-administered, global information resource. It resides on the worldwide computer network and allows access to heterogeneous information: text, image, video, sound and graphic data. Currently, this wealth of information is difficult to mine. One can either manually, slowly and tediously navigate through the WWW or utilize indexes and libraries which are built by automatic search engines (called knowbots or robots). We have designed and are now implementing a high level SQL-like language to support effective and flexible query processing, which addresses the structure and content of WWW nodes and their varied sorts of data. Query results are intuitively presented and continuously maintained when desired. The language itself integrates new utilities and existing Unix tools (e.g. grep, awk)."
"We will consider both academic and non-academic positions, with special attention to some of the trickier points of academic job searches. In addressing these questions, we will draw on our combined personal experience of two-body job hunts as recent as 2003 and as long ago as 1987, along with information gleaned from the two-body job searches of friends and colleagues. At the end of the article, we give references for further reading."
"In the past two years, Nimble Technology has developed a product for this market. Spawned from over a person-decade of data integration research, the product has been deployed at several Fortune-500 beta-customer sites. This abstract reports on the key challenges we faced in the design of our product and highlights some issues we think require more attention from the research community."
"e consider the execution of multi-join queries in a hierarchical parallel system, i.e., a shared-nothing system whose nodes are shared-memory multiprocessors. In this context, load balancing must be addressed at two levels, locally among the processors of each shared-memory node and globally among all nodes. In this paper, we propose a dynamic execution model that maximizes local load balancing within shared-memory nodes and minimizes the need for load sharing across nodes. This is obtained by allowing each processor to execute any operator that can be processed locally, thereby taking full advantage of inter- and intra-operator parallelism. We conducted a performance evaluation using an implementation on a 72-processor KSR1 computer."
"A data warehouse is a redundant collection of data replicated from several possibly distributed and loosely coupled source databases, organized to answer OLAP queries. Relational views are used both as a specification technique and as an execution plan for the derivation of the warehouse data. In this position paper, we summarize the versatility of relational views and their potential."
Data Grids are being built across the world as the next generation data handling systems to manage peta-bytes of inter organizational data and storage space. A data grid (datagrid) is a logical name space consisting of storage resources and digital entities that is created by the cooperation of autonomous organizations and its users based on the coordination of local and global policies. Data Grid Management Systems (DGMSs) provide services for the confluence of organizations and management of inter-organizational data and resources in the datagrid.The objective of the tutorial is to provide an introduction to the opportunities and challenges of this emerging technology.
"Given the complexity of many queries over a Data Warehouse (DW), it is interesting to precompute and store in the DW the answer sets of some demanding operations, so called materialized views. In this paper, we present an algorithm, including its experimental evaluation, which allows the materialization of several views simultaneously without losing sight of processing costs for queries using these materialized views."
"French government has launch in 2000 a public debate about conservation of data and electronic documents. Due to the widespread use of Internet and extranet technologies, especially with electronic document exchange, we had have to adapt the politic of document conservation to this new challenge: ¡°avoid the lack of memory in public administration¡±. A guide-book was produced. This guide-book is an important step to introduce a reflection about the conservation and to give some guidelines."
"To achieve these goals, Rainbow allows the user to configure and program the distributed environment, transactions, and transaction management protocols, and to observe local as well as global executions (history and measured behavior and performance). Rainbow also lends itself as an open system that can be easily changed and extended by students and researchers."
"We present a framework for designing, in a declarative and flexible way, efficient migration programs and an undergoing implementation of a migration tool called RelOO whose targets are any ODBC compliant system on the relational side and the 02 system on the object side. The framework consists of (i) a declarative language to specify database transformations from relations to objects, but also physical properties on the object database (clustering and sorting) and (ii) an algebrabased program rewriting technique which optimizes the migration processing time while taking into account physical properties and transaction decomposition."
"In order to cope with the dynamic scenario of fast changing business requirements enterprises have embraced web technologies to manage their business processes. However, the ability to integrate business processes like procurement, customer relationship management, finance, human resources and manufacturing in a typical supply chain on the web is a challenging task. Today¡¯s virtual enterprises need to integrate different workflows within and across enterprises efficiently so as to provide seamless services."
"his book Databases and Transaction Processing constitutes a standard database textbook for advanced undergraduate and graduate courses¡ª albeit with a somewhat different focus compared to the established books. As the subtitle An Application-Oriented Approach indicates, the authors put an emphasis on teaching the systematic usage of database systems¡ªrather than concentrating on an in-depth coverage of implementation techniques for building database systems. The rationale for this focus is that many more students will be implementing applications than will actually be implementing database systems."
"Here we propose the PeerOLAP architecture for supporting On-Line Analytical Processing queries. A large number low-end clients, each containing a cache with the most useful results, are connected through an arbitrary P2P network. If a query cannot be answered locally (i.e. by using the cache contents of the computer where it is issued), it is propagated through the network until a peer that has cached the answer is found. An answer may also be constructed by partial results from many peers. Thus PeerOLAP acts as a large distributed cache, which amplifies the benefits of traditional client-side caching. The system is fully distributed and can reconfigure itself on-the-fly in order to decrease the query cost for the observed workload."
"This paper briefly describes an approach to business-to-business Internet commerce following a n-suppliers:m-customers scenario in order to provide for a virtual market place on the Internet. The RMP project, partially funded by the European Commission, realizes such a e-commerce system in the domain of small and medium-sized companies in rural areas. The RMP system provided for Internet trading makes heavy use of database technology and has been implemented in Java."
"The emergence and growing popularity of Internet-based electronic market-places, in their various forms, has raised the challenge to explore genericity in market design. In this paper we present a domain-specific software architecture that delineates the abstract components of a generic market and specifies control and data-flow constraints between them, and a framework that allows convenient pluggability of components that implement specific market policies. The framework was realized in the GEM system. GEM provides infrastructure services that allow market designers to focus solely on market-issues. In addition, it allows dynamic (re)configuration of components."
"Data warehouses support the analysis of historical data. This often involves aggregation over a period of time. Furthermore, data is typically incorporated in the warehouse in the increasing order of a time attribute, e.g., date of sale or time of a temperature measurement. In this paper we propose a framework to take advantage of this append only nature of updates due to a time attribute. The framework allows us to integrate large amounts of new data into the warehouse and generate historical summaries efficiently. Query and update costs are virtually independent from the extent of the data set in the time dimension, making our framework an attractive aggregation approach for append-only data streams."
"Archiving is important for scientific data, where it is necessary to record all past versions of a database in order to verify findings based upon a specific version. Much scientific data is held in a hierachical format and has a key structure that provides a canonical identification for each element of the hierarchy. In this article, we exploit these properties to develop an archiving technique that is both efficient in its use of space and preserves the continuity of elements through versions of the database, something that is not provided by traditional minimum-edit-distance diff approaches. The approach also uses timestamps. All versions of the data are merged into one hierarchy where an element appearing in multiple versions is stored only once along with a timestamp. By identifying the semantic continuity of elements and merging them into one data structure, our technique is capable of providing meaningful change descriptions, the archive allows us to easily answer certain temporal queries such as retrieval of any specific version from the archive and finding the history of an element."
"Successful companies organise and run their business activities in an efficient manner. Core activities are completed on time and within specified resource constraints. However to stay competitive in today's markets, companies need to continually improve their efficiency ¡ª business activities need to be completed more quickly, to higher quality and at lower cost. To this end, there is an increasing awareness of the benefits and potential competitive advantage that well designed business process management systems can provide. In this paper we argue the case for an agent-based approach: showing how agent technology can improve efficiency by ensuring that business activities are better scheduled, executed, monitored, and coordinated."
"XQuery is the XML query language currently under development in the World Wide Web Consortium (W3C). XQuery specifications have been published in a series of W3C working drafts, and several reference implementations of the language are already available on the Web. If successful, XQuery has the potential to be one of the most important new computer languages to be introduced in several years. This tutorial will provide an overview of the syntax and semantics of XQuery, as well as insight into the principles that guided the design of the language."
"In this paper, we describe an architecture for an open marketplace exploiting the workflow technology and the currently emerging data exchange and metadata representation standards on the Web. In this market architecture electronic commerce is realized through the adaptable workflow templates provided by the marketplace to its users. Having workflow templates for electronic commerce processes results in a component-based architecture where components can be agents (both buying and selling) as well as existing applications invoked by the workflows. Other advantages provided by the workflow technology are forward recovery, detailed logging of the processes through workflow history manager and being able to specify data and control flow among the workflow components."
Model-driven engineering technologies offer a promising approach to address the inability of third-generation languages to alleviate the complexity of platforms and express domain concepts effectively.
"Beginning in 1989 an ad-hoc collection of senior DBMS researchers has gathered periodically to perform a "" group grope "" i.e. an assessment of the state of the art in DBMS research as well as a prediction concerning what problems and problem areas deserve additional focus. The fifth ad-hoc meeting was held May 4-6, 2003 in Lowell, Ma. A report on the meeting is in preparation, and this panel discussion will summarize the upcoming document and discuss its conclusions."
"We are living in an exciting time in the field of clinical research. There are changes occurring that will alter how medical care is provided, and it is the work of clinical research professionals that will lead these changes. In this column, the Chair of ACRP¡¯s Association Board of Trustees considers the impact of genetics in medicine and their application through precision medicine."
"MOTIVATION A large number of useful databases are currently accessible over the Web and within corporate networks. In addition to being frequently updated, this collection of databases tends to be highly dynamic: new databases appear often, and databases (just like Web sites) also disappear. In this environment, the goal of providing flexible, timely and declarative query access over all these databases remains elusive."
"IP network operators collect aggregate traffic statistics on network interfaces via the Simple Network Management Protocol (SNMP). This is part of routine network operations for most ISPs; it involves a large infrastructure with multiple network management stations polling information from all the network elements and collating a real time data feed. This demo will present a tool that manages the live SNMP data feed on a fully operational large ISP at industry scale. The tool primarily serves to study correlations in the network traffic, by providing a rich mix of ad-hoc querying based on a user-friendly correlation interface and as well as canned queries, based on the expertise of the network operators with field experience."
"In the last years, the exponential growth of computer networks has created an incredibly large offer of products and services in the net. Such a huge amount of information makes it impossible for a single person to analyze all existing offers of a product on the net and decide which of them fits better her requirements. This problem is solved with the intelligent trade agents (ITA), which are programs that have the ability to roam a network, collect business-related data and use them to make decisions to buy goods on their owners' behalf. Known ITA systems do not provide anonymity in transactions, require an on-line trusted third party and implicitly assume that the user trusts the ITA. We present a new scheme for an intelligent untrusted trade agent system allowing anonymous electronic transactions with an off-line trusted third party."
"This article describes a novel way of combining data mining techniques on Internet data in order to discover actionable marketing intelligence in electronic commerce scenarios. The data that is considered not only covers various types of server and web meta information, but also marketing data and knowledge. Furthermore, heterogeneity resolution thereof and Internet- and electronic commerce-specific pre-processing activities are embedded. A generic web log data hypercube is formally defined and schematic designs for analytical and predictive activities are given. From these materialised views, various online analytical web usage data mining techniques are shown, which include marketing expertise as domain knowledge and are specifically designed for electronic commerce purposes."
"Query optimization is a computationally intensive process, especially for the complex queries that are typical in current data warehousing and mining applications. The inherent overheads of query optimization are compounded by the fact that a new query is typically optimized afresh, providing no opportunity to amortize these overheads over prior optimizations. While current commercial query optimizers do provide facilities for reusing execution plans generated for earlier queries (e.g. ""stored outlines"" in Oracle 9i), the query matching is extremely restrictive-only if the incoming query has a close textual resemblance with one of the stored queries is the associated plan re-used to execute the new query."
"ROLEX is a research system for closely coupled XML-relational interoperation [2]. Whereas typical XML-based applications interoperate with existing relational databases via a ¡°shred-and-publish¡± approach, the ROLEX system seeks to provide direct access to relational data via XML interfaces at the speed of cached XML data. To achieve this, ROLEX is integrated tightly with both the DBMS and the application through a standard interface supported by most XML parsers, the Document Object Model (DOM). Thus, in general, an application need not be modified to be used with ROLEX."
"VideoAnywhere has developed such a capability in the form of an extensible architecture as well as a specific implementation using the latest in Internet programming (Java, agents, XML, etc.) and applicable standards. It automatically extracts and manages an extensible set of metadata of major types of videos that can be queried using either attribute-based or keyword-based search. It also provides user profiling that can be combined with the query processing for filtering. A user-friendly interface provides management of all system functions and capabilities. VideoAnywhere can also be used as a video search engine for the Web, and a servlet-based version has also been implemented."
"This is a beautifully simple paper that I feel encompasses many ideas that keep reappearing in different guises every decade or so! The paper proposes the replication of a dictionary (basically a set of key and value pairs) to all relevant sites in a distributed system. Updates and deletes are propagated in a lazy manner through the system as sites communicate with each other using a simple notion of a log. Queries are answered based on the local copy. The notion of correctness is based on the causal dependency between operations. A simple data structure keeps track of ""who knows what"", and is used for reducing the propagated information as well as garbage collection"
"The database community has been researching problems in similarity query for time series databases for many years. The techniques developed in the area might shed light on the query by humming problem. In this demo, we treat both the melodies in the music databases and the user humming input as time series. Such an approach allows us to integrate many database indexing techniques into a query by humming system, improving the quality of such system over the traditional (contour) string databases approach. We design special searching techniques that are invariant to shifting, time scaling and local time warping. This makes the system robust and allows more flexible user humming input."
"We have extended Rainbow, our existing XML data management system, as shown in Figure 1. Rainbow accepts an XQuery query or an update request in an extended XQuery syntax from the user. The XQuery is parsed into an algebraic representation, called XML Algebra Tree (XAT). The XAT is then optimized by the global query optimizer using algebraic rewrite rules. We have introduced a separate phase of XAT cleanup which includes the XAT table schema cleanup and cutting of unnecessary XML operators. This optimization often significantly improves the query performance. The optimized XAT is then executed by the query manager."
"The Brazilian Symposium on Database Systems (SBBD) is a traditional conference in Brazil, and is sponsored by the Brazilian Computer Society. SBBD's technical program contemplates the following activities: presentation of peer reviewed full technical papers, invited talks, tutorials (either invited and selected from submissions), discussion panels and presentation of tools."
"XML has become ubiquitous, and XML data has to be managed in databases. The current industry standard is to map XML data into relational tables and store this information in a relational database. Such mappings create both expressive power problems and performance problems.In the TIMBER project we are exploring the issues involved in storing XML in native format. We believe that the key intellectual contribution of this system is a comprehensive set-at-a-time query processing ability in a native XML store, with all the standard components of relational query processing, including algebraic rewriting and a cost-based optimizer."
The OASIS Prototype is under development at Dublin City University in Ireland. We describe a multi-database architecture which uses the ODMG model as a canonical model and describe an extention for construction of virtual schemas within the multidatabase system. The OMG model is used to provide a standard distribution layer for data from local databases. This takes the form of CORBA objects representing export schemas from separate data sources.
"Companies are using the Web for information dissemination, sparking interest in models and efficient mechanisms for controlled access to information. In this context, securing XML documents is important. Much of the work on XML access control to date has studied models for the specification of XML access control policies, focusing on issues such as granularity of access and conflict resolution. However, there has been little work on enforcement of access control policies for queries. A naive two-step solution to secure query evaluation is to first compute query results, and then use access control policies to filter the results. Consider the XML database of an online-seller, which has information on books and customers."
"The Senior Therapist's Grandiosity: Clinical and Ethical Consequences of Merging Multiple Roles"" is the second paper by ROBERT S. PEPPER, C.S.W., Ph.D. to appear in this Journal on this very important topic in the contemporary practice of psychotherapy. He notes that some senior therapists engage in multiple roles with grandiosity and other unresolved narcissistic pathology, doing harm to their patients, while violating professional and ethical codes of conduct."
"This paper describes issues and solutions related to the creation of a product information database in the enterprise, and using this database as a foundation for deploying an electronic catalog. Today, product information is typically managed in document composition systems and communicated on paper. In the new wired world, these processes are undertaking fundamental changes to cope with the time to market pressure and the need for accurate, complete, and structured presentation of product information. Electronic catalogs are the answer."
"With the popularity of XML, it is increasingly common to nd data in the XML format. This highlights an important question: given an XML document S and a DTD D, how to extract data from S and construct another XML document T such that T conforms to the xed D? Let us refer to this as DTD-conforming XML to XML transformation. The need for this is evident in, e.g., data exchange: enterprises exchange their XML documents with respect to a certain prede ned DTD. Although a number of XML query languages (e.g., XQuery, XSLT) are currently being used to transform XML data, they cannot guarantee DTD conformance. Type inference and (static) checking for XML transformations are too expensive to be used in practice; worse, they provide no guidance for how to specify a DTD-conforming XML to XML transformation. In response to the need we have developed TREX (TRansformation Engine for XML), a middleware system for DTDconforming XML to XML transformations."
"A long-term water quality study has been initiated by the Korean Ministry of Environment(MOE) - The G-7 Project--in cooperation with two national research institutes, an University research tn and a consulting firm. This study includes the development of computer software for total water quality management system, so called ISWQM (Integrated System of Water Quality Management). ISWQM includes four major components: a GIS database; two artificial intelligence (AI) based expert systems to estimate pollutant loadings and to provide cost-effective wastewater treatment system for small and medium size urban areas; and computer programs to integrate the database and expert systems."
"The proliferation and affordability of smart sensors such as webcams, microphones, etc., has created opportunities for exciting new classes of distributed services. While such sensors are inexpensive and easy to deploy across a wide area, realizing useful services requires addressing a number of challenges, such as preventing transfer of large data feeds across the network, efficiently discovering relevant data among the distributed collection of sensors and delivering it to interested participants, and efficiently handling static meta-data information, live readings from sensor feeds, and historical data."
"For several years now, you've been hearing and reading about an emerging standard that everybody has been calling SQL3. Intended as a major enhancement of the current second generation SQL standard, commonly called SQL-92 because of the year it was published, SQL3 was originally planned to be issued in about 1996¡­but things didn't go as planned."
"In this paper, we describe the system architecture and its underlying technology, and report on our ongoing implementation effort, which leverages the PostgreSQL open source code base. We also discuss open issues and our research agenda."
"This paper considers this issue with respect to spatially distributed environmental models. A method of measuring the semantic proximity between components of large, integrated models is presented, along with an example illustrating its application. It is concluded that many of the issues associated with weak model semantics can be resolved with the addition of self-evaluating logic and context-based tools that present the semantic weaknesses to the end-user."
"Phrase matching is a common IR technique to search text and identify relevant documents in a document collection. Phrase matching in XML presents new challenges as text may be interleaved with arbitrary markup, thwarting search techniques that require strict contiguity or close proximity of keywords. We present a technique for phrase matching in XML that permits dynamic specification of both the phrase to be matched and the markup to be ignored. We develop an effective algorithm for our technique that utilizes inverted indices on phrase words and XML tags."
The STREAM project at Stanford is developing a general-purpose system for processing continuous queries over multiple continuous data streams and stored relations. It is designed to handle high-volume and bursty data streams with large numbers of complex continuous queries. We describe the status of the system as of early 2003 and outline our ongoing research directions.
"This paper reports on the principles underlying the semantic and pedagogic interoperability mechanisms built in the European Knowledge Pool System, developed by the European research project ARIADNE. This system, which is the central feature of ARIADNE, consists in a distributed repository of pedagogical documents (or learning objects) of diverse granularity, origin, content, type, language, etc., which are stored in view of their use (and reuse) in telematics-based training or teaching curricula."
"It's my pleasure to announce that SIGMOD is financially strong. Our conference is the best in the field technically. This research excellence has contributed to financial health, enabling the conference to continue to generate more than enough revenue to cover its expenses. SIGMOD '98 took in approximately $25K more than it cost to produce."
"MTCache is a prototype midtier database caching solution for SQL server that achieves this transparency. It builds on SQL server's support for materialized views, distributed queries and replication. We describe MTCache and report experimental results on the TPC-W benchmark. The experiments show that a significant part of the query workload can be offloaded to cache servers, resulting in greatly improved scale-out on the read-dominated workloads of the benchmark. Replication overhead was small with an average replication delay of less than two seconds."
"Internet, Web and distributed computing infrastructures continue to gain in popularity as a means of communication for organizations, groups and individuals alike. In such an environment, characterized by large distributed, autonomous, diverse, and dynamic information sources, access to relevant and accurate information is becoming increasingly complex. This complexity is exacerbated by the evolving system, semantic and structural heterogeneity of these potentially global, cross-disciplinary, multicultural and rich-media technologies. Clearly, solutions to these challenges require addressing directly a variety of interoperability issues."
"A wealth of information is hidden within unstructured text. This information is often best utilized in structured or relational form, which is suited for sophisticated query processing, for integration with relational databases, and for data mining. For example, newspaper and e-mail archives contain information that could be useful to analysts and govenment agencies. Information extraction systems produce a structured representation of the information that is ¡°buried¡± in text documents. Unfortunately, processing each document is computationally expensive, and is not feasible for large text databases or for the web. With many database sizes exceeding millions of documents, processing time is becoming a bottleneck for exploiting information extraction technology."
"In this demonstration, we present a prototype peer-topeer (P2P) application called PeerDB that provides database capabilities. This system has been developed at the National University of Singapore in collaboration with Fudan University, and is being enhanced with more features and applications. The concept behind PeerDB is similar to the analogy of publishing personal web sites, except that it is now applied to personal databases."
"The goal of this paper is to describe the MOMIS (Mediator envirOnment for Multiple Information Sources) approach to the integration and query of multiple, heterogeneous information sources, containing structured and semistructured data. MOMIS has been conceived as a joint collaboration between University of Milano and Modena in the framework of the INTERDATA national research project, aiming at providing methods and tools for data management in Internet-based information systems."
"GridDB is an innovative solution built within Toshiba to solve these complex problems faced by its numerous customers. The foundation of GridDB¡¯s principles is based upon offering a versatile data store that is optimized for IoT, provides high scalability, tuned for high performance, and ensures high reliability."
"Obtaining high quality information has become in recent years a challenging task as data should be gathered and filtered from a large, open and frequently changing network of distributed data sources, with blurred semantics, and no central control over the data sources' structure and availability. This technical challenge is highlighted by the advent of the World Wide Web, its current status and its evolving nature. This state of affair creates a need for technologies for building information services, capable of providing high quality information obtained from distributed, heterogeneous, and autonomous data sources on an as-needed basis."
"Semantic interoperability is a growing challenge in the United States Department of Defense (DoD). In this paper, we describe the basis of an infrastructure for the reconciliation of relevant, but semantically heterogeneous attribute values. Three types of information are described which can be used to infer the context of attributes, making explicit hidden semantic conflicts and making it possible to adjust values appropriately. Through an extended example, we show how an automated integration agent can derive the transformations necessary to perform four tasks in a simple semantic reconciliation."
Database queries often take the form of correlated SQL queries. Correlation refers to the use of values from the outer query block to compute the inner subquery. This is a convenient paradigm for SQL programmers and closely mimics a function invocation paradigm in a typical computer programming language. Queries with correlated subqueries are also often created by SQL generators that translate queries from application domain-specific languages into SQL. Another significant class of queries that use this correlated subquery form is that involving temporal databases using SQL. Performance of these queries is an important consideration particularly in large databases.
"Data warehouses form the essential infrastructure for many data analysis tasks. A core operation in a data warehouse is the construction of a data cube, which can be viewed as a multi-level, multi-dimensional database with aggregate data at multiple granularity."
We deal with the issue of combining dozens of classifiers into a better one. Our first contribution is the introduction of the notion of communities of classifiers. We build a complete graph with one node per classifier and edges weighted by a measure of similarity between connected classifiers. The resulting community structure is uncovered from this graph using the state-of-the-art Louvain algorithm. Our second contribution is a hierarchical fusion approach driven by these communities.
"With these new expectations have come new responsibilities for the information systems professional. We can no longer concern ourselves merely with keeping our systems up and running. We now need to concern ourselves with subjective concepts such as response time and throughput. With current expectations what they are, performance tuning has become vitally important."
"The amount of services and deployed software agents in the most famous o spring of the Internet, the World Wide Web, is exponentially increasing. In addition, the Internet is an open environment, where information sources, communication links and agents themselves may appear and disappear unpredictably. Thus, an e ective, automated search and selection of relevant services or agents is essential for human users and agents as well. We distinguish three general agent categories in the Cyberspace, service providers, service requester, and middle agents."
"As our reliance on computers and computerized data has increased, we have come to expect more from our computers. We no longer expect our computers to act as large expensive calculators that merely spit out bills and paychecks. We now, additionally, expect our systems to rapidly access and interactively present us with large volumes of accurate data. In fact, our expectations have changed so much, in the past decade, that we no longer focus on what our systems are but rather on what they do."
"Rapid growth in the volume of documents, their diversity, and terminological variations render federated digital libraries increasingly difficult to manage. Suitable abstraction mechanisms are required to construct meaningful and scalable document clusters, forming a cross-digital library information space for browsing and semantic searching. This paper addresses the above issues, proposes a distributed semantic framework that achieves a logical partitioning of the information space according to topic areas, and provides facilities to contextualize and landscape the available document sets in subject-specific categories."
"Given the complexity of many queries over a Data Warehouse (DW), it is interesting to precompute and store in the DW the answer sets of some demanding operations, so called materialized views. In this paper, we present an algorithm, including its experimental evaluation, which allows the materialization of several views simultaneously without losing sight of processing costs for queries using these materialized views."
"In view of this, we propose shifting from a cardinality-based approach to a rate-based approach, and give an optimization framework that aims at maximizing the output rate of query evaluation plans. This approach can be applied to cases where the cardinality-based approach cannot be used. It may also be useful for cases where cardinalities are known, because by focusing on rates we are able not only to optimize the time at which the last result tuple appears, but also to optimize for the number of answers computed at any specified time after the query evaluation commences. We present a preliminary validation of our rate-based optimization framework on a prototype XML query engine, though it is generic enough to be used in other database contexts."
"Welcome to SIGMOD 2002! We think you will find both the conference and the setting to be invigorating. The natural timeless beauty of British Columbia will provide a fitting counterpoint to the dynamism of our field in which large scale, high performance, and ever more intelligent database systems are being conceived and deployed. This dynamism is reflected in our (extreme) keynote presentations, tutorials, research papers, demonstrations, industrial papers, and product presentations. The only unfortunate side of our program is that the five parallel session structure may prevent you from hearing every talk in which you are interested."
"The InfoSleuth T M Project at MCC has developed a distributed agent architecture that addresses the need for semantic interoperability among information sources and analytical tools within diverse application domains. InfoSleuth is being used as a significant component of the Environmental Data Exchange Network (EDEN) 2. The current EDEN pilot demonstration enables integrated access via web browser to environmental information resources provided by offices of these agencies located in several states. At the application level, InfoSleuth provides for semantic interchange among users by allowing an application developer to express the concepts and relationships of the application domain in high-level terms that are then translated into the low-level types of database schemas or semantic analyses of text and image resources."
"A point data retrieval algorithm for the HG-tree is introduced which improves the number of nodes accessed. The HG-tree is a multidimensional indexing tree designed for point data and it is a simple modification from the Hilbert R-tree for indexing spatial data. The HG-tree data search method mainly makes use of the Hilbert index values to search for exact data, instead of using conventional point search methods as used in most of the R-tree papers. The use of Hilbert curve values and MBR can reduce the spatial cover of an MBR."
"Clustering of large databases is an important research area with a large variety of applications in the data base context. Missing in most of the research efforts are means for guiding the clustering process and understand the results, which is especially important if the data under consideration is high dimensional and has not been collected for the purpose of being analyzed. Visualization technology may help to solve this problem since it allows an effective support of different clustering paradigms and provides means for a visual inspection of the results."
"The integrated design of the Web interface and of data content gives several advantages in the design of data-intensive Web sites. The main objectives of this design process are (a) associating the Web with a high-level description of its content, that can be used for querying, evolution, and maintenance; (b) providing multiple views of the same data; (c) separating the de nition of information content from Web page composition, navigation, and presentation, which should be de ned independently and autonomously; (d) storing the meta-information collected during the design process within a repository used for the dynamic generation of Web pages; (e) collecting information about the Web site usage, obtained both statically (user registration) and dynamically (user tracking); (f) supporting selective access to information based on users' requirements and needs; (g) using business rules to improve the generation of e ective Web pages and to present each user with personalised views of the Web site."
"Currently gene expression data are being produced at a phenomenal rate. The general objective is to try to gain a better understanding of the functions of cellular tissues. In particular, one specific goal is to relate gene expression to cancer diagnosis, prognosis and treatment. However, a key obstacle is that the availability of analysis tools or lack thereof, impedes the use of the data, making it difficult for cancer researchers to perform analysis efficiently and effectively."
"The chair of ACRP¡¯s Association Board of Trustees recounts how he left manufacturing and research and development a decade ago to take a position as a clinical research administrator. It was a move that place him into a role he knew little about, having not been engaged in clinical research beforehand."
"There are a number of database systems available free of charge for the research community, with complete access to the source code. Some of these systems result from completed research projects, others have been developed outside the research community. How can the database community best take advantage of these publically available systems? The most widely used open-source database is MySQL. Their objective is to become the 'best and most used database in the world'. Can they do it without the database research community?"
"Heavily used in both academic and corporate R&D settings, ACM Transactions on Database Systems (TODS) is a key publication for computer scientists working in data abstraction, data modeling, and designing data management systems. Topics include storage and retrieval, transaction management, distributed and federated databases, semantics of data, intelligent databases, and operations and algorithms relating to these areas."
"From recent conferences, position papers, special journal issues, and informal hallway discussions, we have witnessed a quickly rising tide of interest among the database research community in querying and processing data streams. Numerous modem applications operate over data that arrives in the form of rapid, continuous streams, and in many of these applications simply diverting the streams in their entirety into a conventional DBMS and querying them in a conventional fashion is infeasible in terms of performance and functionality. Example applications include sensor networks, Web tracking, financial monitoring, telecommunications, network monitoring and traffic engineering, and manufacturing processes."
"Currently, many projects are being conducted in the following areas: real-time databases, object-oriented databases, mobile databases, multimedia databases, data mining and data warehouses. These projects have been funded by federal and state agencies as well as private industries such as National Science Foundation, the U.S. Department of Education, Oklahoma State Department of Environmental Quality, and Objectivity, Inc."
"Operators of large networks and providers of network services need to monitor and analyze the network traffic flowing through their systems. Monitoring requirements range from the long term (e.g., monitoring link utilizations, computing traffic matrices) to the ad-hoc (e.g. detecting network intrusions, debugging performance problems). Many of the applications are complex (e.g., reconstruct TCP/IP sessions), query layer-7 data (find streaming media connections), operate over huge volumes of data (Gigabit and higher speed links), and have real-time reporting requirements (e.g., to raise performance or intrusion alerts).We have found that existing network monitoring technologies have severe limitations. One option is to use TCPdump to monitor a network port and a user-level application program to process the data. While this approach is very flexible, it is not fast enough to handle gigabit speeds on inexpensive equipment."
This paper aims at classifying existing approaches which can be used to query heterogeneous data sources. We consider one of the approaches ¡ª the mediated query approach ¡ª in more detail and provide a classification framework for it as well.
"In this demo, we show how database-style declarative queries can be executed over data streaming from sensor networks. Our demo consists of two major components: a set of Berkeley TinyOS battery-powered, wireless sensor ""motes"" (see Figure 1) that produce and process data, and a desktop-based query processor which parses queries, distributes them over motes, and collects and displays answers. Specifically, we allow conference attendees standing at our query processing workstation to query a number of motes distributed throughout the demo space."
"Internet search engines have popularized keyword based search. While relational database systems offer powerfifl structured query languages such as SQL, there is no support for keyword search over databases. The simplicity of keyword search as a querying paradigm offers compelling values for data exploration. Specifically, keyword search does not require a priori knowledge of the schema. The above is significant as much information in a corporation is increasingly being available at its intranet. However, it is unrealistic to expect users who would browse and query such information to have detailed knowledge of the schema of available databases. Therefore, just as keyword search and classification hierarchies complement each other for document search, keyword search over databases can be effective."
"We are pleased to announce an excellent technical program for the 6th International Conference on Pervasive Computing and Communications. The program covers a broad cross section of topics in pervasive computing and communications. This year, 160 papers were submitted for consideration to the program committee. As a result, the selection process was highly competitive, and the result is a program of high-quality papers."
"Welcome to IPDPS 2004 in Santa Fe. This year¡¯s program includes 17 workshops with a total of 306 papers. Many of the workshops have grown steadily in strength and are now operating with parallel sessions or on multiple days. We are pleased to welcome one new workshop this year, in the area of High Performance Grid Computing. As always, we are looking for new workshop proposals for the next IPDPS."
"Data cube enables fast online analysis of large data repositories which is attractive in many applications. Although there are several kinds of available cube-based OLAP products, users may still encounter challenges on effectiveness and efficiency in the exploration of large data cubes due to the huge computation space as well as the huge observation space in a data cube. CubeExplorer is an integrated environment for online exploration of data cubes. It integrates our newly developed techniques on iceberg cube computation, cube-based feature extraction, and gradient analysis, and makes cube exploration effective and efficient. In this demo, we will show the features of CubeExplorer, especially its power and flexibility at exploring and mining of large databases."
Content placement algorithm: An ACDN must decide which applications to deploy where and when. Content placement is solved trivially in traditional CDNs by cache replacement algorithms.
We propose a multi-resolution transmission mechanism that allows various organizational units of a web document to be transferred and browsed according to the amount of information captured. We define the notion of information content for each individual organizational unit of a web document as an indication of its captured information. The concept of information content is used as a foundation for defining the notion of relative information content which determines the transmission order of various units. Our mechanism allows a web client to explore the more content-bearing portion of a web document earlier so as to be able to terminate browsing a possibly irrelevant document sooner.
"DBCache also includes a cache initialization component that takes a backend database schema and SQL queries in the workload, and generates a middle-tier database schema for the cache."
"The workshop Towards Adaptive Workflow System was organized by the authors of this report as part of the 1998 Conference on Computer Supported Collaborative Work (CSCW-98), and was held at the Westin Seattle on Saturday, November 14, 1998. The workshop had about 30 attendees and included invited presentations, paPer presentations/discussions and a panel. This report summarizes on the Goals and topics of the workshop, presents the major activities and summarizes some of the issues discussed during the workshop."
"We demonstrate the COUGAR System, a new distributed data management infrastructure that scales with the growth of sensor interconnectivity and computational power on the sensors over the next decades. Our system resides directly on the sensor nodes and creates the abstraction of a single processing node without centralizing data or computation."
"This is my first issue as associate editor of software reviews for The American Statistician. In this column, I will introduce myself, comment on the types of software reviews that can be published in this section of The American Statistician, and encourage others in the profession to consider taking on the task of reviewing statistical software packages."
"As WWW becomes more and more popular and powerful, how to search information on the web in database way becomes an important research topic. COMMIX, which is developed in the DB group in Peking University (China), is a system towards building very large database using data from the Web for information extraction, integration and query answering. COMMIX has some innovative features, such as ontology-based wrapper generation, XML-based information integration, view-based query answering, and QBE-style XML query interface."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
"In ebXML, trading parties collaborate by agreeing on the same business process with complementary roles. Therefore there is a need for standardized business processes. In this respect, exploiting the already developed expertise through RosettaNet PIPs becomes indispensable. We show how to create and use ebXML ""Binary Collaborations"" based on RosettaNet PIPs and provide a GUI tool to allow users to graphically build their ebXML business processes by combining RosettaNet PIPs. In ebXML, trading parties reveal essential information about themselves through Collaboration Protocol Profiles (CPPs)."
"A database of ¡«250  active fault traces in the Caribbean and Central American regions has been assembled to characterize the seismic hazard and tectonics of the area, as part of the Global Earthquake Model (GEM) Foundation's Caribbean and Central American Risk Assessment (CCARA) project."
"In this paper we describe a Patricia tree-based B-tree variant suitable for OLTP. In this variant, each page of the B-tree contains a local Patricia tree instead of the usual sorted array of keys. It has been implemented in iAnywhere ASA Version 8.0. Preliminary experience has shown that these indexes can provide significant space and performance benefits over existing ASA indexes."
"Only a small fraction, probably less than 1%, of the $1.149 trillion spent annually on medical care is spent on health promotion. Despite the progress we h~.ve made on developing the science of health promotion, it is not recognized as a mature science by any respected scientific group."
"A star schema is very popular for modeling data warehouses and data marts. Therefore, it is important that a database system which is used for implementing such a data warehouse or data mart is able to efficiently handle operations on such a schema. In this paper we will describe how one of these operations, the join operation --- probably the most important operation --- is implemented in the IBM Informix Extended Parallel Server (XPS)."
"After the successful first International Workshop on Engineering Federated Database Systems (EFDBS'97) in Barcelona in June 1997 [CEH+ 97], the goal of this second workshop was to bring together researchers and practitioners interested in various issues in the development of federated information systems, whereby the scope has been extended to cover database and non-database information sources (the change from EFDBS to EFIS reflects this). This report provides details of the workshop content and the conclusions reached in the final discussion."
"Conceptual data modeling for complex applications, such as multimedia and spatiotemporal applications, often results in large, complicated and difficult-to-comprehend diagrams. One reason for this is that these diagrams frequently involve repetition of autonomous, semantically meaningful parts that capture similar situations and characteristics. By recognizing such parts and treating them as units, it is possible to simplify the diagrams, as well as the conceptual modeling process. We propose to capture autonomous and semantically meaningful excerpts of diagrams that occur frequently as modeling patterns."
"We present a comprehensive solution to the problem that has been tightly integrated with the optimizer of a commercial shared-nothing parallel database system. Our approach uses the query optimizer itself both to recommend candidate partitions for each table that will benefit each query in the workload, and to evaluate various combinations of these candidates. We compare a rank-based enumeration method with a random-based one. Our experimental results show that the former is more effective."
"In this paper we present a novel technique for cost estimation of user-defined methods in advanced database systems. This technique is based on multi-dimensional histograms. We explain how the system collects statistics on the method that a database user defines and adds to the system. From these statistics a multi-dimensional histogram is built. Afterwards, this histrogram can be used for estimating the cost of the target method whenever this method is referenced in a query."
"In this paper, we propose the novel idea of hierarchical subspace sampling in order to create a reduced representation of the data. The method is naturally able to estimate the local implicit dimensionalities of each point very effectively, and thereby create a variable dimensionality reduced representation of the data. Such a technique has the advantage that it is very adaptive about adjusting its representation depending upon the behavior of the immediate locality of a data point. An interesting property of the subspace sampling technique is that unlike all other data reduction techniques, the overall efficiency of compression improves with increasing database size."
"Much of the functionality required to support first class views can be generated semi-automatically, if the derivations between layers are declarative (e.g., SQL, rather than Java). We present a framework where propagation rules can be defined, allowing the flexible and incremental specification of view semantics, even by non-programmers. Finally, we describe research areas opened up by this approach."
"This paper describes the Dwarf structure and the Dwarf cube construction algorithm. Further optimizations are then introduced for improving clustering and query performance. Experiments with the current implementation include comparisons on detailed measurements with real and synthetic datasets against previously published techniques. The comparisons show that Dwarfs by far out-perform these techniques on all counts: storage space, creation time, query response time, and updates of cubes."
"In this article, we will discuss the effects of applying traditional transaction management techniques to multi-tier architectures in distributed environments. We will show the performance costs associated with distributed transactions and discuss ways by which enterprises really manage their distributed data to circumvent this performance hit. Our intent is to share our experience as an industrial customer with the database research and vendor community to create more usable and scalable designs."
"Recently several important relational database tasks such as index selection, histogram tuning, approximate query processing, and statistics selection have recognized the importance of leveraging workloads. Often these tasks are presented with large workloads, i.e., a set of SQL DML statements, as input. A key factor affecting the scalability of such tasks is the size of the workload. In this paper, we present the novel problem of workload compression which helps improve the scalability of such tasks. We present a principled solution to this challenging problem. Our solution is broadly applicable to a variety of workload-driven tasks, while allowing for incorporation of task specific knowledge. We have implemented this solution and our experiments illustrate its effectiveness in the context of two workload-driven tasks: index selection and approximate query processing."
"We have developed a web-based architecture and user interface for fast storage, searching and retrieval of large, distributed, files resulting from scientific simulations. We demonstrate that the new DATALINK type defined in the draft SQL Management of External Data Standard can help to overcome problems associated with limited bandwidth when trying to archive large files using the web. We also show that separating the user interface specification from the user interface processing can provide a number of advantages. We provide a tool to generate automatically a default user interface specification, in the form of an XML document, for a given database."
"In this paper we describe solutions for two potentially problematic aspects of such a data management system: backup/recovery and data consistency. We present algorithms for performing backup and recovery of the DBMS data in a coordinated fashion with the files on the file servers. Our algorithms for coordinated backup and recovery have been implemented in the IBM DB2/DataLinks product. We also propose an efficient solution to the problem of maintaining consistency between the content of a file and the associated meta-data stored in the DBMS from a reader's point of view without holding long duration locks on meta-data tables. In the model, an object is directly accessed and edited in-place through normal file system APIs using a reference obtained via an SQL Query on the database."
nvited Talk I.- Some Advances in Data-Mining Techniques.- Web Exploration.- Querying Semantically Tagged Documents on the World-Wide Web.- WWW Exploration Queries.- Strategies for Filtering E-mail Messages Combining Content-Based and Sociological Filtering with User-Stereotypes.- Interactive Query Expansion in a Meta-search Engine.- Database Technology.- On the Optimization of Queries containing Regular Path Expressions.
"Dual Match, recently proposed as a dual approach of FRM, improves performance significantly over FRM by exploiting point filtering effect. However, it has the problem of having a smaller allowable window size---half that of FRM---given the minimum query length. A smaller window increases false alarms due to window size effect. General Match offers advantages of both methods: it can reduce window size effect by using large windows like FRM and, at the same time, can exploit point-filtering effect like Dual Match. General Match divides data sequences into generalized sliding windows (J-sliding windows) and the query sequence into generalized disjoint windows (J-disjoint windows)."
"Clustering is the process of grouping a set of objects into classes of similar objects. Although definitions of similarity vary from one clustering model to another, in most of these models the concept of similarity is based on distances, e.g., Euclidean distance or cosine distance. In other words, similar objects are required to have close values on at least a set of dimensions. In this paper, we explore a more general type of similarity. Under the pCluster model we proposed, two objects are similar if they exhibit a coherent pattern on a subset of dimensions. For instance, in DNA microarray analysis, the expression levels of two genes may rise and fall synchronously in response to a set of environmental stimuli. Although the magnitude of their expression levels may not be close, the patterns they exhibit can be very much alike. Discovery of such clusters of genes is essential in revealing significant connections in gene regulatory networks."
This paper proposes a simple model for a timer-driven triggering and alerting system. Such a system can be used with relational and object-relational databases systems. Timer-driven trigger systems have a number of advantages over traditional trigger systems that test trigger conditions and run trigger actions in response to update events. They are relatively easy to implement since they can be built using a middleware program that simply runs SQL statements against a DBMS.
"We have developed new sort algorithms which eliminate almost all the compares, provide functional parallelism which can be exploited by multiple execution units, significantly reduce the number of passes through keys, and improve data locality. These new algorithms outperform traditional sort algorithms by a large factor.For the Datamation disk to disk sort benchmark (one million 100-byte records), at SIGMOD'94, Chris Nyberg et al presented several new performance records using DEC alpha processor based systems."
"For each algorithm, we investigate the performance effects of explicit duplicate removal and referential integrity enforcement, variants for inputs larger than memory, and parallel execution strategies. Analytical and experimental performance comparisons illustrate the substantial differences among the algorithms."
"Many societal applications, for example, in domains such as health care, land use, disaster management, and environmental monitoring, increasingly rely on geographical information for their decision making. With the emergence of the World WideWeb this information is typically located in multiple, distributed, diverse, and autonomously maintained systems."
"At present Web services are thought as the revolution of the next generation e-commerce and its technical architectures include UDDI, WSDL, SOAP, XML and so on. Web service discovery is one of the most important parts in the web service architectures."
"In this paper, we report our success in building efficient scalable classifiers in the form of decision tables by exploring capabilities of modern relational database management systems. In addition to high classification accuracy, the unique features of the approach include its high training speed, linear scalability, and simplicity in implementation.  The novel classification approach based on grouping and counting and its implementation on top of RDBMS is described. The results of experiments conducted for performance evaluation and analysis are presented."
"This paper introduces algorithms to recognize the invariant part of a data flow tree, and to restructure the evaluation plan to reuse the stored intermediate result. We also propose an efficient method to teach an existing join optimizer to understand the invariant feature and thus allow it to be able to generate better join plans in the new context. Some other related optimization techniques are also discussed. The proposed techniques were implemented within three months on an existing real commercial database system."
"This demonstration illustrates how a comprehensive database reconciliation tool can provide the ability to characterize data-quality and data-reconciliation issues in complex real-world applications. Telcordia¡¯s data reconciliation and data quality analysis tool includes rapid generation of appropriate pre-processing and matching rules applied to a training set created from samples of the data. Once tuned, the appropriate rules can be applied efficiently to the complete data sets. The tool uses a modular JavaBeans-based architecture that allows for customized matching functions and iterative runs that build upon previously learned information."
"In this paper, we define and examine a particular class of queries called group queries. Group queries are natural queries in many decisionsupport applications. The main characteristic of a group query is that it can be executed in a groupby-group fashion. In other words, the underlying relation(s) can be partitioned (based on some set of attributes) into disjoint groups, and each group can be processed separately. We give a syntactic criterion to identify these queries and prove its sufficiency."
"Several alternatives to manage large XML document collections exist, ranging from file systems over relational or other database systems to specifically tailored XML base management systems. In this paper we give a tour of Natix, a database management system designed from scratch for storing and processing XML data. Contrary to the common belief that management of XML data is just another application for traditional databases like relational systems, we illustrate how almost every component in a database system is affected in terms of adequacy and performance."
"The AQR-Toolkit divides the query routing task into two cooperating processes: query refinement and source selection. It is well known that a broadly defined query inevitably produces many false positives. Query refinement provides mechanisms to help the user formulate queries that will return more useful results and that can be processed efficiently. As a complimentary process, source selection reduces false negatives by identifying and locating a set of relevant information providers from a large collection of available sources. By pruning irrelevant information sources, source selection also reduces the overhead of contacting the information servers that do not contribute to the answer of the query. The system architecture of AQR-Toolkit consists of a hierarchical network (a directed acyclic graph) with external information providers at the leaves and query routers as mediating nodes. The end-point information providers support query-based access to their documents."
"We present the design of ObjectGlobe, a distributed and open query processor for Internet data sources. Today, data is published on the Internet via Web servers which have, if at all, very localized query processing capabilities. The goal of the ObjectGlobe project is to establish an open marketplace in which data and query processing capabilities can be distributed and used by any kind of Internet application. Furthermore, ObjectGlobe integrates cycle providers (i.e., machines) which carry out query processing operators. The overall picture is to make it possible to execute a query with ¨C in principle ¨C unrelated query operators, cycle providers, and data sources."
"We survey existing value-based approaches, develop a reference architecture that helps compare the approaches, and categorize the constituent algorithms. We explain the options for collecting value metadata, and for using that metadata to improve search, ranking of results, and the enhancement of information browsing. Based on our survey and analysis, we then point to several open problems."
"MENTOR (¡°Middleware for Enterprise-Wide Workflow Management¡±) is a joint project of the University of the Saarland, the Union Bank of Switzerland, and ETH Zurich [1, 2, 3]. The focus of the project is on enterprise-wide workflow management. Workflows in this category may span multiple organizational units each unit having its own workflow server, involve a variety of heterogeneous information systems, and require many thousands of clients to interact with the workflow management system (WFMS). The project aims to develop a scalable and highly available environment for the execution and monitoring of workflows, seamlessly integrated with a specification and verification environment. For the specification of workflows,"
"The popularity of on-line document databases has led to a new problem: finding which text databases (out of many candidate choices) are the most relevant to a user. Identifying the relevant databases for a given query is the text database discovery problem. The first part of this paper presents a practical solution based on estimating the result size of a query and a database. The method is termed GlOSS¡ªGlossary of Servers Server. The second part of this paper evaluates the effectiveness of GlOSS based on a trace of real user queries. In addition, we analyze the storage cost of our approach."
"Over the coming years, an increasingly ubiquitous and increasingly capacious Internet will introduce new opportunities for the creation of tightly integrated databases distributed across multiple institutions. These new capabilities, along with certain techniques arising from the emerging field of computational finance, could ultimately transform a substantial portion of the world¡¯s commercial and financial activity in fundamental ways. This talk will focus on some of the most significant changes such technologies may induce in the structure of the world financial system and the mechanisms of global commerce. Consideration will be given to such topics as algorithmic trading and portfolio optimization; electronic markets, automated marketmaking, and the historical inevitability of computational disintermediation; and the future of electronic commerce, including the potential use of shared knowledge bases incorporating standardized representations of enormous numbers of products and services available from multiple sources"
"We address the problem of ordering accesses to multiple information sources, in order to maximize the likelihood of obtaining answers as early as possible. We describe a declarative formalism for specifying these kinds of probabilistic information, and we propose algorithms for ordering the information sources. Finally, we discuss a preliminary experimental evaluation of these algorithms on the domain of bibliographic sources available on the WWW."
"Recently several important relational database tasks such as index selection, histogram tuning, approximate query processing, and statistics selection have recognized the importance of leveraging workloads. Often these tasks are presented with large workloads, i.e., a set of SQL DML statements, as input. A key factor affecting the scalability of such tasks is the size of the workload. In this paper, we present the novel problem of workload compression which helps improve the scalability of such tasks. We present a principled solution to this challenging problem. Our solution is broadly applicable to a variety of workload-driven tasks, while allowing for incorporation of task specific knowledge. We have implemented this solution and our experiments illustrate its effectiveness in the context of two workload-driven tasks: index selection and approximate query processing."
"Relational OLAP tools and other database applications generate sequences of SQL statements that are sent to the database server as result of a single information request provided by a user. Unfortunately, these sequences cannot be processed efficiently by current database systems because they typically optimize and process each statement in isolation. We propose a practical approach for this optimization problem, called ""coarse-grained optimization,"" complementing the conventional query optimization phase. This new approach exploits the fact that statements of a sequence are correlated since they belong to the same information request. A lightweight heuristic optimizer modifies a given statement sequence using a small set of rewrite rules."
"The parameters of the continuous-time Markov chain model, the probabilities of co-accessing certain documents and the interaction times between successive accesses, are dynamically estimated and adjusted to evolving workload patterns by keeping online statistics. The integrated policy for vertical data migration has been implemented in a prototype system. The system makes profitable use of the Markov chain model also for the scheduling of volume exchanges in the tertiary storage library. Detailed simulation experiments with Web-server-like synthetic workloads indicate significant gains in terms of client response time. The experiments also show that the overhead of the statistical bookkeeping and the computations for the access predictions is affordable."
"Over the last few years, there have been at least two dramatic changes in the way computers are used. The first has its origin in the fact that computers have become more and more connected to each other. The second was triggered by the increasing miniaturization and affordability of hardware components and power supplies, together with the development of wireless communication paths. These two trends combined have allowed the development of powerful, yet comparatively low-priced, portable computers. In spite of these changes, little attention has been given to reaching a common consensus and to the development of a strong infrastructure in this area."
There appears to be a discrepancy between the research topics being pursued by the database research community and the key problems facing information systems decisions makers such as Chief Information Officers (CIOs). Panelists will present their view of the key problems that would benefit from a research focus in the database research community and will discuss perceived discrepancies.
"Morgan Kaufmann Publishers is the exclusive worldwide distributor for the VLDB proceedings volumes listed below: ISBN 2000 Cairo, Egypt 1-55860-715-3 1999 Edinburgh, Scotland 1-55860-615-7 1998 New York, USA 1-55860-566-5 1997 Athens, Greece 1-55860-470-7 1996 Mumbai (Bombay), India 1-55860-382-4 1995 Zurich, Switzerland 1-55860-379-4 1994 Santiago, Chile 1-55860-153-8 1993 Dublin, Ireland 1-55860-152-X 1992 Vancouver, Canada 1-55860-151-1 1991 Barcelona, Spain 1-55860-150-3 1990 Brisbane, Australia 1-55860-149-X 1989 Amsterdam, The Netherlands 1-55860-101-5 1988 Los Angeles, USA 0-934613-75-3 1985 Stockholm, Sweden 0-934613-17-6 1984 Singapore 0-934613-16-8 1983 Florence, Italy 0-934613-15-X 1996 2000 5-year set 1-55860-719-6 ($198) 1991 2000 10-year set 1-55860-720-x ($378) 1988 2000 13-year set 1-55860-718-8 ($486)"
"We show that in this case there can be multiple maximal admissible subsets and that all maximal admissible subsets can be characterized as 3-valued stable models of PRA. We show that for a given set of user requests, in the presence of referential actions of the form ON UPDATE CASCADE, the admissibility check and the computation of the subsequent database state, and (for non-admissible updates) the derivation of debugging hints all are in ptime. Thus, full referential actions can be implemented efficiently."
"Unfortunately, there is very little money to support the health promotion initiatives in this plan. Health promotion receives very little of the $17 billion NIH research budget and few health promotion procedures are covered by the $400+ billion spent annually for Medicare and Medicaid. The Office of Health Promotion and Disease Prevention has a budget so small that very few health promotion professionals ever encounter this office directly during their careers."
"The paper discusses the LHAM concepts, including concurrency control and recovery, our full-fledged LHAM implementation, and experimental performance results based on this implementation. A detailed comparison with the TSB-tree, both analytically and based on experiments with real implementations, shows that LHAM is highly superior in terms of insert performance, while query performance is in almost all cases at least as good as for the TSB-tree; in many cases it is much better."
"We describe the TIGUKAT objectbase management system, which is under development at the Laboratory for Database Systems Research at the University of Alberta. TIGUKAT has a novel object model, whose identifying characteristics include a purely behavioral semantics and a uniform approach to objects. Everything in the system, including types, classes, collections, behaviors, and functions, as well as meta-information, is a first-class object with well-defined behavior. In this way, the model abstracts everything, including traditional structural notions such as instance variables, method implementation, and schema definition, into a uniform semantics of behaviors on objects."
"This paper describes the Onion technique, a special indexing structure for linear optimization queries. Linear optimization queries ask for top-N records subject to the maximization or minimization of linearly weighted sum of record attribute values. Such query appears in many applications employing linear models and is an effective way to summarize representative cases, such as the top-50 ranked colleges. The Onion indexing is based on a geometric property of convex hull, which guarantees that the optimal value can always be found at one or more of its vertices."
"WALRUS employs a novel similarity model in which each image is first decomposed into its regions and the similarity measure between a pair of images is then defined to be the fraction of the area of the two images covered by matching regions from the images. In order to extract regions for an image, WALRUS considers sliding windows of varying sizes and then clusters them based on the proximity of their signatures. An efficient dynamic programming algorithm is used to compute wavelet-based signatures for the sliding windows. Experimental results on real-life data sets corroborate the effectiveness of WALRUS'S similarity model."
"The education industry has a very poor record of productivity gains. In this brief article, I outline some of the ways the teaching of a college course in database systems could be made more efficient, and staff time used more productively. These ideas carry over to other programming-oriented courses, and many of them apply to any academic subject whatsoever. After proposing a number of things that could be done, I concentrate here on a system under development, called OTC (On-line Testing Center), and on its methodology of ""root questions."""
"From the standpoint of satisfying human's information needs, the current digital library (DL) systems suffer from the following two shortcomings: (i) inadequate high-level cognition support; (ii) inadequate knowledge sharing facilities. In this article, we introduce a two-layered digital library architecture to support different levels of human cognitive acts. The model moves beyond simple information searching and browsing across multiple repositories, to inquiry of knowledge about the contents of digital libraries."
"In this paper we propose a shift in the intuition behind outerjoin: Instead of computing the join while also preserving its arguments, outerjoin delivers tuples that come either from the join or from the arguments. Queries with joins and outerjoins deliver tuples that come from one out of several joins, where a single relation is a trivial join. An advantage of this view is that, in contrast to preservation, disjunction is commutative and associative, which is a significant property for intuition, formalisms, and generation of execution plans."
"This paper describes an incomplete data cube design. An incomplete data cube is modeled as a federation of cubettes. A cubette is a complete subcube within the incomplete data cube. The incomplete cube is built piecemeal by giving a concise, high-level specification of each cubette. An efficient algorithm to retrieve an aggregate value from the incomplete data cube is described. When a value cannot be retrieved because it is missing, alternatives at a lower precision that can be retrieved are identified."
"Complex database queries require the use of memory-intensive operators like sort and hash-join. Those operators need memory, also referred to as SQL memory, to process their input data. For example, a sort operator uses a work area to perform the in-memory sort of a set of rows. The amount of memory allocated by these operators greatly affects their performance. However, there is only a finite amount of memory available in the system, shared by all concurrent operators. The challenge for database systems is to design a fair and efficient strategy to manage this memory."
"The elapsed time for external mergesort is normally dominated by I/O time. This paper is focused on reducing I/O time during the merge phase. Three new buffering and readahead strategies are proposed, called equal buffering, extended forecasting and clustering. They exploit the fact that virtually all modern disks perform caching and sequential readahead. The latter two also collect information during run formation (the last key of each run block) which is then used to preplan reading. For random input data, extended forecasting and clustering were found to reduce merge time by 30% compared with traditional double buffering."
"We also describe an adaptive page sampling algorithm which achieves greater efficiency by using all values in a sampled page but adjusts the amount of sampling depending on clustering of values in pages. Next, we establish that the problem of estimating the number of distinct values is provably difficult, but propose a new error metric which has a reliable estimator and can still be exploited by query optimizers to influence the choice of execution plans."
"Various relation-based systems, concerned with the qualitative representation and processing of spatial knowledge, have been developed in numerous application domains. In this article, we identify the common concepts underlying qualitative spatial knowledge representation, we compare the representational properties of the different systems, and we outline the computational tasks involved in relation-based spatial information processing. We also describesymbolic spatial indexes, relation-based structures that combine several ideas in spatial knowledge representation. A symbolic spatial index is an array that preserves only a set of spatial relations among distinct objects in an image, called the modeling space; the index array discards information, such as shape and size of objects, and irrelevant spatial relations."
"A goal of the Biomedical Informatics Research Network (birn) project is to develop a multi-institution information management system for Neurosciences to gain a deeper understanding of several neurological disorders. Each institution specializes in a different subdiscipline and produces a database of its experimental or computationally derived data; a mediator module performs semantic integration over the databases to enable neuroscientists to perform analyses that could not be done from any single institution¡¯s data. The overall system architecture of the birn system is that of a wrapper-mediator system. The information sources are various relational sources including Oracle 9i having userdefined packages, Oracle 8i with the Spatial Data Cartridge, and databases made available over the web."
"E-business sites are increasingly utilizing dynamic web pages since they enable a much wider range of interaction than static HTML pages can provide. Dynamic page generation technologies allow a Web site to generate pages at run-time, based on various parameters. Delaying content decisions until run-time a ords a Web site signi cant exibility in customizing page content, thereby enriching users' Web experiences. At the same time, however, dynamic page generation technologies have resulted in serious performance problems due to the increased load placed on the server-side infrastructure. Consequently, end users experience increased response times."
"Data mining evolved as a collection of applicative problems and efficient solution algorithms relative to rather peculiar problems, all focused on the discovery of relevant information hidden in databases of huge dimensions. In particular, one of the most investigated topics is the discovery of association rules. This work proposes a unifying model that enables a uniform description of the problem of discovering association rules. The model provides SQL-like operator, named MINE RULE, which is capable of expressing all the problems presented so far in the literature concerning the mining of association rules. We demonstrate the expressive power of the new operator by means of several examples, some of which are classical, while some others are fully original and correspond to novel and unusual applications. We also present the operational semantics of the operator by means of an extended relational algebra."
"Application Servers (ASs), which have become very popular in the last few years, provide the platforms for the execution of transactional, server-side applications in the online world. ASs are the modern cousins of traditional transaction processing monitors (TPMs) like CICS. In this tutorial, I will provide an introduction to different ASs and their technologies. ASs play a central role in enabling electronic commerce in the web context. They are built on the basis of more standardized protocols and APIs than were the traditional TPMs. The emergence of Java, XML and OMG standards has played a significant role in this regard."
"This paper formalizes a rule-based policy framework that includes provisions and obligations, and investigates a reasoning mechanism within this framework. A policy decision may be supported by more than one derivation, each associated with a potentially different set of provisions and obligations (called a global PO set). The reasoning mechanism can derive all the global PO sets for each specific policy decision, and facilitates the selection of the best one based on numerical weights assigned to provisions and obligations as well as on semantic relationships among them."
"We highlight some of the pleasures of coding with Java, and some of the pains of coding around Java in order to obtain good performance in a data-intensive server. For those issues that were painful, we present concrete suggestions for evolving Java's interfaces to better suit serious software systems development. We believe these experiences can provide insight for other designers to avoid pitfalls we encountered and to decide if Java is a suitable platform for their system."
"We investigate the optimization and evaluation of queries with universal quantification in the context of the object-oriented and object-relational data models. The queries are classified into 16 categories depending on the variables referenced in the so-called range and quantifier predicates. For the three most important classes we enumerate the known query evaluation plans and devise some new ones. These alternative plans are primarily based on anti-semijoin, division, generalized grouping with count aggregation, and set difference. In order to evaluate the quality of the many different evaluation plans a thorough performance analysis on some sample database configurations was carried out."
"In this paper, we establish a number of optimality results for the existing encoding schemes; in particular, we prove that neither of the two known schemes is optimal for the class of two-sided range queries. We also propose a new encoding scheme and prove that it is optimal for that class. Finally, we present an experimental study comparing the performance of the new encoding scheme with that of the existing ones as well as four hybrid encoding schemes for both simple selection queries and the more general class of membership queries of the form"
"Thank you for downloading foundation for object relational databases the third manifesto. As you may know, people have search hundreds times for their chosen books like this foundation for object relational databases the third manifesto, but end up in malicious downloads. Rather than reading a good book with a cup of tea in the afternoon, instead they are facing with some harmful virus inside their laptop."
The results show that current hardware technology trends have significantly changed the performance tradeoffs considered in past studies. A simplistic data placement strategy based on the new results is developed and shown to perform well for a variety of workloads.
"BeSS is a high performance, memory-mapped object storage manager offering distributed transaction management facilities and extensible support for persistence. In this paper, we present an overview of the peer-to-peer architecture of BeSS, and we discuss issues related to space management, inter-object references, database corruption, operation modes, cache replacement, and transaction management."
"We present an update on the status of the Cougar Sensor Database Project, in which we are investigating a database approach to sensor networks: Clients ""program"" the sensors through queries in a high-level declarative language (such as a variant of SQL). In this paper, we give an overview of our activities on energy-efficient data dissemination and query processing. Due to space constraints, we cannot present a full menu of results; instead, we decided to only whet the reader's appetite with some problems in energy-efficient routing and in-network aggregation and some thoughts on how to approach them."
"We present the information mediator prototype called Kind, recently developed as part of an integrated Neuroscience workbench project at SDSC/UCSD within the NPACI project. The broad goal of the workbench is to serve as an environment where, among other tasks, the Neuroscientist can query a mediator to retrieve information from across a number of information sources, and use the results to perform her own analysis on the data. The Kind mediator is an instance of a novel model-centered mediator architecture that extends current XML-based mediator approaches by incorporating a semantic model of an information source as an integral part of the mediation process."
"An ¡Ê-approximate quantile summary of a sequence of N elements is a data structure that can answer quantile queries about the sequence to within a precision of N. We present a new online algorithm for computing¡Ê-approximate quantile summaries of very large data sequences. The algorithm has a worst-case space requirement of &Ogr;(1¡Â¡Ê log(¡ÊN)). This improves upon the previous best result of &Ogr;(1¡Â¡Ê log2(¡ÊN)). Moreover, in contrast to earlier deterministic algorithms, our algorithm does not require a priori knowledge of the length of the input sequence. Finally, the actual space bounds obtained on experimental data are significantly better than the worst case guarantees of our algorithm as well as the observed space requirements of earlier algorithms."
"The democratization of ubiquitous computing, the increasing connection of corporate databases to the Internet and the today's natural resort to Web hosting companies and Database Service Providers strongly emphasize the need for data confidentiality. The chapter proposes a solution called chip-secured data access (C-SDA), which allows querying encrypted data while controlling personal privileges. C-SDA is a client-based security component acting as an incorruptible mediator between a client and an encrypted database."
"PointCast Inc, the inventor and leader in broadcast news via the Internet and corporate intranets was founded in 1992 to deliver news as it happens from leading sources such as CNN, the New York Times, Wall Street Journal Interactive Edition and more, directly to a viewer's computer screen."
"In response to pressures to reduce product lead times,manufacturing companies are increasingly aware of the need for someform of integration along the whole product chain. Engineeringtasks must be coordinated and data exchanged between the variousspecialised tools. An enterprise has two main tracks of informationflow, namely technical and managerial, and product data managementspans both tracks. On the technical track, applications are highlyspecialised supporting tasks such as product design (CAD) and theprogramming of numerically controlled machines (CAM). Generally,the various application systems on the technical track are referredto as CAx systems. CAx systems may not only differ in terms offunctionality but also in terms of the amount and type of datamanaged, the run-time environment and performance characteristics.For complete support of Computer Integrated Manufacturing (CIM),we must be able to integrate existing technical and administrativecomponent application systems."
"A number of researchers have become interested in the design of global-scale networked systems and applications. Our thesis here is that the database community's principles and technologies have an important role to play in the design of these systems. The point of departure is at the roots of database research: we generalize Codd's notion of data independence to physical environments beyond storage systems. We note analogies between the development of database indexes and the new generation of structured peer-to-peer networks. We illustrate the emergence of data independence in networks by surveying a number of recent network facilities and applications, seen through a database lens."
"The CQ project at OGI, funded by DARPA, aims at developing a scalable toolkit and techniques for update monitoring and event-driven information delivery on the net. The main feature of the CQ project is a ¡°personalized update monitoring¡± toolkit based on continual queries [3]. Comparing with the pure pull (such as DBMSs, various web search engines) and pure push (such as Pointcast, Marimba, Broadcast disks) technology, the CQ project can be seen as a hybrid approach that combines the pull and push technology by supporting personalized update monitoring through a combined client-pull and server-push paradigm."
"Beginning in 1989 an ad-hoc collection of senior DBMS researchers has gathered periodically to perform a "" group grope "" ; i.e. an assessment of the state of the art in DBMS research as well as a prediction concerning what problems and problem areas deserve additional focus. The fifth ad-hoc meeting was held May 4-6, 2003 in Lowell, Ma. A report on the meeting is in preparation, and this panel discussion will summarize the upcoming document and discuss its conclusions."
"In this demo, we show how database-style declarative queries can be executed over data streaming from sensor networks. Our demo consists of two major components: a set of Berkeley TinyOS battery-powered, wireless sensor ""motes"" (see Figure 1) that produce and process data, and a desktop-based query processor which parses queries, distributes them over motes, and collects and displays answers. Specifically, we allow conference attendees standing at our query processing workstation to query a number of motes distributed throughout the demo space."
"This paper addresses the problem of finding the K closest pairs between two spatial data sets, where each set is stored in a structure belonging in the R-tree family. Five different algorithms (four recursive and one iterative) are presented for solving this problem. The case of 1 closest pair is treated as a special case. An extensive study, based on experiments performed with synthetic as well as with real point data sets, is presented. A wide range of values for the basic parameters affecting the performance of the algorithms, especially the effect of overlap between the two data sets, is explored."
"In this paper, we present an original and complete methodology for supervising relational query processing in shared nothing systems. A new control mechanism is introduced which allows the detection and the correction of optimizer estimation errors and load imbalance. We especially focus on the management of intraprocessor communication and on the overlapping of communication and computation. Performance evaluations on an hypercube and a grid interconnection machine show the efficiency and the robustness of the proposed methods."
"In this research, we represent our operational environment in two distinct ways. First, we characterize the underlying physical databases that serve as a foundation for the entire Westlaw search system. Second, we create a rearchitected set of logical document collections that corresponds to classes of high level organizational concepts such as jurisdiction, practice area, and document-type. Keeping the end-user in mind, we focus on performance issues relating to optimal database selection, where domain experts have provided complete pre-hoc relevance judgments for collections characterized under each of our physical and logical database models."
"In this paper, we investigate algorithms for generic schema matching, outside of any particular data model or application. We first present a taxonomy for past solutions, showing that a rich range of techniques is available. We then propose a new algorithm, Cupid, that discovers mappings between schema elements based on their names, data types, constraints, and schema structure, using a broader set of techniques than past approaches. Some of our innovations are the integrated use of linguistic and structural matching, context-dependent matching of shared types, and a bias toward leaf structure where much of the schema content resides. After describing our algorithm, we present experimental results that compare Cupid to two other schema matching systems."
"Here we propose a simple language UnQL for querying data organized as a rooted, edge-labeled graph. In this model, relational data may be represented as fixed-depth trees, and on such trees UnQL is equivalent to the relational algebra. The novelty of UnQL consists in its programming constructs for arbitrarily deep data and for cyclic structures. While strictly more powerful than query languages with path expressions like XSQL, UnQL can still be efficiently evaluated. We describe new optimization techniques for the deep or ""vertical"" dimension of UnQL queries. Furthermore, we show that known optimization techniques for operators on flat relations apply to the ""horizontal"" dimension of UnQL."
"Interactive computer graphics systems for visualization of realistic-looking, three-dimensional models are useful for evaluation, design and training in virtual environments, such as those found in architectural and mechanical CAD, ight simulation, and virtual reality. Interactive visualization systems display images of a threedimensional model on the screen of a computer workstation as seen from a simulated observer's viewpoint under control by a user. If images are rendered smoothly and quickly enough, an illusion of real-time exploration of a virtual environment can be achieved as the simulated observer moves through the model."
"This article concentrates on query unnesting (also known as query decorrelation), an optimization that, even though it improves performance considerably, is not treated properly (if at all) by most OODB systems. Our framework generalizes many unnesting techniques proposed recently in the literature, and is capable of removing any form of query nesting using a very simple and efficient algorithm. The simplicity of our method is due to the use of the monoid comprehension calculus as an intermediate form for OODB queries. The monoid comprehension calculus treats operations over multiple collection types, aggregates, and quantifiers in a similar way, resulting in a uniform method of unnesting queries, regardless of their type of nesting."
"XQuery is a query language for real and virtual XML documents and collections of these documents. Its development began in the second half of 1999. With roughly 3 years of work completed, it¡¯s high time that we provided an initial description of this language, and a sense of where it is in its development cycle. XQuery is being developed within W3C. Every consortium of this type has its own rules and its own ways of getting its work done. W3C provides visibility to the public by making available drafts of the specifications that it has under development at relatively frequent intervals. Mailing lists are established for each specification to allow the public to provide feedback on these drafts."
"In this paper we examine the problem of duplicates, in transformation-based enumeration. In general, different sequences of transformation rules may end up deriving the same element, and the optimizer must detect and discard these duplicate elements generated by multiple paths. We show that the usual commutativity/associativity rules for joins generate O(4^n) duplicate operators. We then propose a scheme ---within the generic transformation-based framework --- to avoid the generation of duplicates, which does achieve the O(3^n) lower bound on join enumeration. Our experiments show an improvement of up to a factor of 5 in the optimization of a query with 8 tables, when duplicates are avoided rather than detected."
"This chapter shows the basic functionality of the Gem-BASE system, using the Oracle database installed at the San Diego Supercomputer Center. The database has been extended with data types for representing surfaces, which also implement all the necessary operations. Surface objects are specialized in Spherical surface objects and in flat surface objects. Brain researchers, neurologists and neurosurgeons acquire 3-D brain images from normal and diseased subjects with the idea to study the properties of brains, make comparisons and to measure changes caused by factors like age and disease."
"Scientific data of importance to biologists in the Humitn Genome Project resides not only in conventional da.tabases, but in structured files maintained in a number of different formats (e.g. ASN.1 a.nd ACE) as well a.s sequence analysis packages (e.g. BLAST and FASTA). These formats and packages contain a number of data types not found in conventional databases, such as lists and variants, and may be deeply nested. We present in this paper techniques for querying and transforming such data, and illustrate their use in a prototype system developed in conjunction with the Human Genome Center for Chromosome 22. We also describe optimizations performed by the system, a crucial issue for bulk data."
"The nearestor near-neighbor query problems arise in a large variety of database applications, usually in the context of similarity searching. Of late, there has been increasing interest in building search/index structures for performing similarity search over high-dimensional data, e.g., image databases, document collections, time-series databases, and genome databases. Unfortunately, all known techniques for solving this problem fall prey to the \curse of dimensionality."" That is, the data structures scale poorly with data dimensionality; in fact, if the number of dimensions exceeds 10 to 20, searching in k-d trees and related structures involves the inspection of a large fraction of the database, thereby doing no better than brute-force linear search. It has been suggested that since the selection of features and the choice of a distance metric in typical applications is rather heuristic, determining an approximate nearest neighbor should su ce for most practical purposes. In this paper, we examine a novel scheme for approximate similarity search based on hashing."
"We address the development of a normalization theory for object-oriented data models that have common features to support objects. We first provide an extension of functional dependencies to cope with the richer semantics of relationships between objects, called path dependency, local dependency, and global dependency constraints. Using these dependency constraints, we provide normal forms for object-oriented data models based on the notions of user interpretation (user-specified dependency constraints) and object model. In constrast to conventional data models in which a normalized object has a unique interpretation, in object-oriented data models, an object may have many multiple interpretations that form the model for that object. An object will then be in a normal form if and only if the user's interpretation is derivable from the model of the object. Our normalization process is by nature iiterative, in which objects are restructured until their models reflect the user's interpretation."
"Wide-area database replication technologies and the avail-ability of data centers allow database copies to be dis-tributed across the network. This requires a complete e-commercewebsite suite (i.e. edgecaches, Web servers, ap-plication servers, and DBMS) to be distributed along withthe database replicas. A major advantage of this approachis, like the caches, the possibility of serving dynamic con-tent from a location close to the users, reducing networklatency. However, this is achieved at the expense of ad-ditional overhead, caused by the need of invalidating dy-namic content cached in the edge caches and synchroniza-tion of the database replicas in the data center."
"In this paper, we propose a new technique called structural function inlining which inlines recursive functions used in a query by making good use of available type information. Based on the technique, we develop a new approach to typing and optimizing structurally recursive queries. The new approach yields a more precise result type for a query. Furthermore, it produces an optimal algebraic expression for the query with respect to the type information. When a structurally recursive query is applied to non-recursive XML data, our approach translates the query into a finitely nested iterations."
"To bridge the gap between these two extremes, we propose a new class of replication systems called TRAPP (Tradeoff in Replication Precision and Performance). TRAPP systems give each user fine-grained control over the tradeoff between precision and performance: Caches store ranges that are guaranteed to bound the current data values, instead of storing stale exact values. Users supply a quantitative precision constraint along with each query. To answer a query, TRAPP systems automatically select a combination of locally cached bounds and exact master data stored remotely to deliver a bounded answer consisting of a range that is no wider than the specified precision constraint, that is guaranteed to contain the precise answer, and that is computed as quickly as possible. This paper defines the architecture of TRAPP replication systems and covers some mechanics of caching data ranges."
This paper proposes an effective key management scheme to harden embedded devices against side-channel attacks. This technique leverages the bandwidth limitation of side channels and employs an effective updating mechanism to prevent the keying materials from being exposed. This technique forces attackers to launch much more expensive and invasive attacks to tamper embedded devices and also has the potential of defeating unknown semi-invasive side-channel attacks.
"Clustering results validation is an important topic in the context of pattern recognition. We review approaches and systems in this context. In the first part of this paper we presented clustering validity checking approaches based on internal and external criteria. In the second, current part, we present a review of clustering validity approaches based on relative criteria. Also we discuss the results of an experimental study based on widely known validity indices. Finally the paper illustrates the issues that are under-addressed by the recent approaches and proposes the research directions in the field."
This is a beautifully simple paper that I feel encompasses many ideas that keep reappearing in different guises every decade or so! The paper proposes the replication of a dictionary (basically a set of key and value pairs) to all relevant sites in a distributed system. Updates and deletes are propagated in a lazy manner through the system as sites communicate with each other using a simple notion of a log. Queries are answered based on the local copy.
"We present a two-phase Web Query Optimizer (WQO). In a pre-optimization phase, the WQO selects one or more WSIs for a pre-plan; a pre-plan represents a space of query evaluation plans (plans) based on this choice of WSIs. The WQO uses cost-based heuristics to evaluate the choice of WSI assignment in the pre-plan and to choose a good pre-plan. The WQO uses the pre-plan to drive the extended relational optimizer to obtain the best plan for a pre-plan. A prototype of the WQO has been developed. We compare the effectiveness of the WQO, i.e., its ability to efficiently search a large space of plans and obtain a low cost plan, in comparison to a traditional optimizer."
"To facilitate queries over semi-structured data, various structural summaries have been proposed. Structural summaries are derived directly from the data and serve as indices for evaluating path expressions on semi-structured or XML data. We introduce the D(k) index, an adaptive structural summary for general graph structured documents. Building on previous work, 1-index and A(k) index, the D(k)-index is also based on the concept of bisimilarity. However, as a generalization of the 1-index and A(k)-index, the D(k) index possesses the adaptive ability to adjust its structure according to the current query load."
"In this article, we analyze several quorum types in order to better understand their behavior in practice. The results obtained challenge many of the assumptions behind quorum based replication. Our evaluation indicates that the conventional read-one/write-all-available approach is the best choice for a large range of applications requiring data replication. We believe this is an important result for anybody developing code for computing clusters as the read-one/write-all-available strategy is much simpler to implement and more flexible than quorum-based approaches. In this article, we show that, in addition, it is also the best choice using a number of other selection criteria."
"In this article, we first introduce the syntax of Temporal-Probabilistic (TP) relations and then show how they can be converted to an explicit, significantly more space-consuming form, called Annotated Relations. We then present a theoretical annotated temporal algebra (TATA). Being explicit, TATA is convenient for specifying how the algebraic operations should behave, but is impractical to use because annotated relations are overwhelmingly large. Next, we present a temporal probabilistic algebra (TPA). We show that our definition of the TP-algebra provides a correct implementation of TATA despite the fact that it operates on implicit, succinct TP-relations instead of overwhemingly large annotated relations. Finally, we report on timings for an implementation of the TP-Algebra built on top of ODBC."
"This paper describes the current INFORMIX IDS/UD release (9.2 or Centaur) and compares and contrasts its functionality with the features of the SQL-99 language standard. INFORMIX and Illustra have been shipping DBMSs implementing the spirit of the SQL-99 standard for five years. In this paper, we review our experience working with ORDBMS technology, and argue that while SQL-99 is a huge improvement over SQL-92, substantial further work is necessary to make object-relational DBMSs truly useful. Specifically, we describe several interesting pieces of functionality unique to IDS/UD, and several dilemmas our customers have encountered that the standard does not address."
"We define the problem of content integration for E-Business, and show how it differs in fundamental ways from traditional issues surrounding data integration, application integration, data warehousing and OLTP. Content integration includes catalog integration as a special case, but encompasses a broader set of applications and challenges. We explore the characteristics of content integration and required services for any solution. In addition, we explore architectural alternatives and discuss the use of XML in this arena."
"The archive will enable astronomers to explore the data interactively. Data access will be aided by multidimensional spatial and attribute indices. The data will be partitioned in many ways. Small tag objects consisting of the most popular attributes will accelerate frequent searches. Splitting the data among multiple servers will allow parallel, scalable I/O and parallel data analysis. Hashing techniques will allow efficient clustering, and pair-wise comparison algorithms that should parallelize nicely. Randomly sampled subsets will allow de-bugging otherwise large queries at the desktop. Central servers will operate a data pump to support sweep searches touching most of the data."
"In this paper, we claim that such approach is inadequate for rare classes, because of two problems: splintered false positives and error-prone small disjuncts. Motivated by the strengths of our two-phase design, we design various synthetic data models to identify and analyze the situations in which two state-of-the-art methods, RIPPER and C4.5 rules, either fail to learn a model or learn a very poor model. In all these situations, our two-phase approach learns a model with significantly better recall and precision levels. We also present a comparison of the three methods on a challenging real-life network intrusion detection dataset. Our method is significantly better or comparable to the best competitor in terms of achieving better balance between recall and precision."
"Clustering is one of the most important tasks performed in Data Mining applications. This paper presents an efficient SQL implementation of the EM algorithm to perform clustering in very large databases. Our version can effectively handle high dimensional data, a high number of clusters and more importantly, a very large number of data records. We present three strategies to implement EM in SQL: horizontal, vertical and a hybrid one. We expect this work to be useful for data mining programmers and users who want to cluster large data sets inside a relational DBMS."
"This chapter discusses the semantic Toronto publish/subscribe system. Middleware that can satisfy this requirement include event-based architectures such as publish-subscribe systems. The pub/sub paradigm has recently gained a significant interest in the database community for the support of information dissemination applications for which other models turned out to be inadequate. In pub/sub systems, clients are autonomous components that exchange information by publishing events and by subscribing to the classes of events, they are interested in. In these systems, publishers produce information, while subscribers consume it. A component usually generates a message when it wants the external world to know that a certain event has occurred."
"In this paper, we extend this initial proposal, which only dealt with behavioural aspects, to cope with the question of representing data aspects as well. In this context, we show how the expressive process algebra LOTOS (and its toolbox CADP) can be used to tackle this issue."
"The CONTROL project at U.C. Berkeley has developed technologies to provide online behavior for data-intensive applications. Using new query processing algorithms, these technologies continuously improve estimates and confidence statistics. In addition, they react to user feedback, thereby giving the user control over the behavior of long-running operations. This demonstration displays the modifications to a database system and the resulting impact on aggregation queries, data visualization, and GUI widgets. We then compare this interactive behavior to batch-processing alternatives."
This metadatabase system provides several functions for performing the semantic associative search for images by using the metadata representing the features of images. These functions are realized by using our proposed mathematical model of meaning. The mathematical model of meaning is extended to compute specific meanings of keywords which are used for retrieving images unambiguously and dynamically. The main feature of this model is that the semantic associative search is performed in the orthogonal semantic space. This space is created for dynamically computing semantic equivalence or similarity between the metadata items of the images and keywords.
The DataLinks technology developed at IBM Almaden Research Center and now available in DB2 UDB 5.2 introduces a new data type called DATALINK for a database to reference and manage files stored external to the database. An external file is put under a database control by ¡°linking¡± the file to the database. Control to a file can also be removed by ¡°unlinking¡± it. The technology provides transactional semantics with respect to linking or unlinking the file when DATALINK value is stored or updated.
"The volume of unstructured text and hypertext data far exceeds that of structured data. Text and hypertext are used for digital libraries, product catalogs, reviews, newsgroups, medical reports, customer service reports, and the like. Currently measured in billions of dollars, the worldwide internet activity is expected to reach a trillion dollars by 2002. Database researchers have kept some cautious distance from this action. The goal of this tutorial is to expose database researchers to text and hypertext information retrieval (IR) and mining systems, and to discuss emerging issues in the overlapping areas of databases, hypertext, and data mining."
"The amount of services and deployed software agents in the most famous o spring of the Internet, the World Wide Web, is exponentially increasing. In addition, the Internet is an open environment, where information sources, communication links and agents themselves may appear and disappear unpredictably. Thus, an e ective, automated search and selection of relevant services or agents is essential for human users and agents as well. We distinguish three general agent categories in the Cyberspace, service providers, service requester, and middle agents. Service providers provide some type of service, such as nding information, or performing some particular domain speci c problem solving. Requester agents need provider agents to perform some service for them."
We provide an overview of query processing in parallel database systems and discuss several open issues in the optimization of queries for parallel machines.
"Various types of computer systems are used behind the scenes in many parts of the telecommunications network to ensure its efficient and trouble-free operation. These systems are large, complex, and expensive real-time computer systems that are mission critical, and contains a database engine as a critical component. These systems share some of common database issues with conventional applications, but they also exhibit rather unique characteristics that present challenging database issues."
"MapInfo SpatialWare is an integrated spatial information management system implemented as a ¡°Spatial Extender¡± to the IBM Universal Database (GA to be determined), a ¡°Spatial DataBlade¡± on the Informix Dynamic Server with the Universal Data Option, or as a spatial server on Oracle. It provides on-line spatial data services and improves critical business processes and operational applications. It enables the storage of spatial data in the RDBMS and its rapid retrieval using a sophisticated RTree indexing. SpatialWare uses a robust data model, fully scaleable client/server architecture for the desktop (PC and UNIX) and an extended SQL-based spatial query language to provide a single source for creating custom spatial solutions."
"We present in this paper a fully automatic content-based approach to organizing and indexing video data. Our methodology involves three steps:<ul><li>Step 1: We segment each video into shots using a Camera-Tracking technique. This process also extracts the feature vector for each shot, which consists of two statistical variances. The above three inter-related techniques offer an integrated framework for modeling, browsing, and searching large video databases. Our experimental results indicate that they have many advantages over existing methods."
"One of the recently proposed techniques for the efficient evaluation of OLAP aggregate queries is the usage of clustering access methods. These methods store the fact table of a data warehouse clustered according to the dimension hierarchies using special attributes called hierarchical surrogate keys. In the presence of these access methods new processing and optimization techniques have been recently proposed. One important such optimization technique, called Hierarchical Pre-Grouping, uses the hierarchical surrogate keys in order to aggregate the fact table tuples as early as possible and to avoid redundant joins."
"MineSetTM is a highly integrated suite of client-server tools for the high-end mining and visualization of very large enterprise databases. MineSet represents the confluence of several important software and hardware technologies: data mining algorithms, fast multiprocessing database servers, novel techniques for interactive 3-D data visualization, and powerful graphics workstations. MineSet provides integrated facilities for the extraction of data from varied sources, algorithms for mining the extracted data, and tools for the 3-D visualization of results."
"Both databases and knowledge bases are used to represent the relevant parts of an application domain, and to allow convenient access to the stored information. Research in knowledge representation (KR) originally concentrated on expressive formalisms with sophisticated reasoning services, usually under the assumption that the size of the knowledge base (KB) was relatively small. In contrast, database (DB) research was concerned with e ciently storing, retrieving, and sharing large amounts of simple data, but the languages for describing schema informationwere rather simple, and reasoning about the schema played only a minor role."
Data Mining places specific requirements on DBMS query performance that cannot be evaluated satisfactorily using existing OLAP benchmarks. The DD Benchmark - defined here - provides a practical case and yardstick to explore how well a DBMS is able to support Data Mining applications. It was derived from real-life data mining tasks performed by our Data SurveyorTM tool running on a variety of DBMS backends. We describe initial results obtained using both the Monet system and a relational DBMS product as backend.
"We study the effectiveness of probabilistic selection of join-query evaluation plans, without reliance on tree transformation rules. Instead, each candidate plan is chosen uniformly at random from the space of valid evaluation orders. This leads to a transformation-free strategy where a sequence of random plans is generated and the plans are compared on their estimated costs. The success of this strategy depends on the ratio of ``good'' evaluation plans in the space of alternatives, the efficient generation of random candidates, and an accurate estimation of their cost. To avoid a biased exploration of the space, we solved the open problem of efficiently generating random, uniformly-distributed evaluation orders, for queries with acyclic graphs. This benefits any optimization or sampling scheme in which a random choice of (initial) query plans is required. A direct comparison with iterative improvement and simulated annealing, using a proven cost-evaluator, shows that our transformation-free strategy converges faster and yields solutions of comparable cost."
"This paper presents a Domain Specific Language (DSL) for expressing business rules in a business-friendly language and sufficiently formal in order to be machine-processed. The core feature of this DSL is that its semantic leverages the Semantics of Business Vocabulary and Business Rules (SBVR) standard which is a metamodel for specifying the semantic models of business using natural language. Our DSL provides business stakeholders with a custom editor with auto-completion, automatic highlighting, content assist, error handling and an outline view on the model. It is built on a parser generated from a grammar which defines the controlled and structured syntax to guide a non technical user to express declarative business rules in SBVR Structured English (SSE)."
"Two new algorithms, ¡°Jive join¡± and ¡°Slam join,¡± are proposed for computing the join of two relations using a join index. The algorithms are duals: Jive join range-partitions input relation tuple ids and then processes each partition, while Slam join forms ordered runs of input relation tuple ids and then merges the results. Both algorithms make a single sequential pass through each input relation, in addition to one pass through the join index and two passes through a temporary file, whose size is half that of the join index. Both algorithms require only that the number of blocks in main memory is of the order of the square root of the number of blocks in the smaller relation."
"We analyze this algorithm, and prove that is optimal when the maximally specific sentences are ""small"". We also point out its limitations.We then present a new algorithm, the Dualize and Advance algorithm, and prove worst-case complexity bounds that are favorable in the general case. Our results use the concept of hypergraph transversals. Our analysis shows that the a priori algorithm can solve the problem of enumerating the transversals of a hypergraph, improving on previously known results in a special case. On the other hand, using results for the general case of the hypergraph transversal enumeration problem, we can show that the Dualize and Advance algorithm has worst-case running time that is sub-exponential to the output size."
"A spatial distance join is a relatively new type of operation introduced for spatial and multimedia database applications. Additional requirements for ranking and stopping cardinality are often combined with the spatial distance join in on-line query processing or internet search environments. These requirements pose new challenges as well as opportunities for more efficient processing of spatial distance join queries. In this paper, we first present an efficient k-distance join algorithm that uses spatial indexes such as R-trees. Bi-directional node expansion and plane-sweeping techniques are used for fast pruning of distant pairs, and the plane-sweeping is further optimized by novel strategies for selecting a sweeping axis and direction."
"We propose a novel method that is designed to handle disjunctive queries within metric spaces. The user provides weights for positive examples; our system ""learns"" the implied concept and returns similar objects. Our method differs from existing relevance-feedback methods that base themselves upon Euclidean or Mahalanobis metrics, as it facilitates learning even disjunctive, concave models within vector spaces, as well as arbitrary metric spaces. Our main contributions are two-fold. Not only do we present a novel way to estimate the dissimilarity of an object to a set of desirable objects, but we support it with an algorithm that shows how to exploit metric indexing structures that support range queries to accelerate the search without incurring false dismissals."
"Traditionally, optimizers are ¡°programmed¡± to optimize queries following a set of buildin procedures. However, optimizers should be robust to its changing environment to generate the fittest query execution plans. To realize adaptiveness, we propose and design an adaptive optimizer with two features. First, the search space and search strategy of the optimizer can be tuned by parameters to allow the optimizer to pick the one that fits best during the optimization process. Second, the optimizer features a ¡°learning¡± capability for canned queries that allows existing plans to be incrementally replaced by ¡°fitter¡± ones. An experimental study on large multijoin queries based on an analytical model is used to demonstrate the effectiveness of such an approach."
"This paper describes issues and solutions related to the creation of a product information database in the enterprise, and using this database as a foundation for deploying an electronic catalog. Today, product information is typically managed in document composition systems and communicated on paper. In the new wired world, these processes are undertaking fundamental changes to cope with the time to market pressure and the need for accurate, complete, and structured presentation of product information."
"In this paper, we present the efficient content based image retrieval systems which employ the color, texture and shape information of images to facilitate the retrieval process. For efficient feature extraction, we extract the color, texture and shape feature of images automatically using edge detection which is widely used in signal processing and image compression. For facilitated the speedy retrieval we are implements the antipole-tree algorithm for indexing the images."
"In this paper, we consider a dynamic self-tuning approach to reorganization in a shared nothing system. We introduce a new index-based method that faciliates fast and efficient migration of data. Our solution incorporates a globally height-balanced structure and load tracking at different levels of granularity. We conducted an extensive performance study, and implemented the methods on the Fujitsu AP3000 machine. Both the simulation and empirical results demonstratic that our proposed method is indeed scalable and effective in correcting any deterioration in system throughput."
"This paper describes an efficient optimistic concurrency control scheme for use in distributed database systems in which objects are cached and manipulated at client machines while persistent storage and transactional support are provided by servers. The scheme provides both serializability and external consistency for committed transactions; it uses loosely synchronized clocks to achieve global serialization. It stores only a single version of each object, and avoids maintaining any concurrency control information on a per-object basis; instead, it tracks recent invalidations on a per-client basis, an approach that has low in-memory space overhead and no per-object disk overhead."
"Model management aims at reducing the amount of programming needed for the development of metadata-intensive applications. We present a first complete prototype of a generic model management system, in which high-level operators are used to manipulate models and mappings between models. We define the key conceptual structures: models, morphisms, and selectors, and describe their use and implementation. We specify the semantics of the known model-management operators applied to these structures, suggest new ones, and develop new algorithms for implementing the individual operators."
"In this article we carefully define a query cost framework that incorporates both selectivity and cost estimates for selections. We develop an algorithm called Predicate Migration, and prove that it produces optimal plans for queries with expensive methods. We then describe our implementation of Predicate Migration in the commercial object-relational database management system Illustra, and discuss practical issues that affect our earlier assumptions. We compare Predicate Migration to a variety of simplier optimization techniques, and demonstrate that Predicate Migration is the best general solution to date. The alternative techniques we present may be useful for constrained workloads."
"Active database systems are now in widespread use. The use of triggers in these systems, however, is difficult because of the complex interaction between triggers, transactions, and application programs. Repeated calculations of rules may incur costly redundant computations in rule conditions and actions. In this paper, we focus on active relational database systems supporting SQL triggers. In this context, we provide a powerful and complete solution to eliminate redundant computations of SQL triggers when they are costly. We define a model to describe programs, rules and their interactions. We provide algorithms to extract invariant subqueries from trigger's condition and action. We define heuristics to memorize the most ¡°profitable¡± invariants. Finally, we develop a rewriting technique that enables to generate and execute the optimized code of SQL triggers."
"The theme of the paper is to promote research on asynchronous transactions. We discuss our experience of executing synchronous transactions on a large distributed production system in The Boeing Company. Due to the poor performance of synchronous transactions in our environment, it motivated the exploration of asynchronous transactions as an alternate solution. This paper presents the requirements and benefits/limitations of asynchronous transactions. Open issues related to large scale deployments of asynchronous transactions are also discussed."
"Response time is one key point of di erentiation among electronic commerce (e-commerce) Web sites. Snafu and slow-downs at major Web sites during special events or peak times demonstrate the diAEculty of scaling up ecommerce sites. Such slow response times and down times can be devastating for e-commerce sites as indicated in a recent study by Zona Research on the relationship between Web page download time and user abandonment rate. The study shows that only 2% of users will leave a Web site (i.e. abandonment rate) if the download time is less than 7 seconds. However, The abandonment rate goes up to 70% when the download time is around 12 seconds. This study clearly establishes the importance of fast response times to an e-commerce Web site to retain its customers."
"Our paper addresses the problem by proposing the MV3R-tree, a structure that utilizes the concepts of multi-version B-trees and 3D-Rtrees. Extensive experimentation proves that MV3R-trees compare favorably with specialized structures aimed at timestamp and interval window queries, both in terms of time and space requirements."
"In this presentation, we will describe a collection of new object-relational features that have been added to IBM's DB2 Universal Database (UDB) system. The features to be described include support for structured types, object references, and hierarchies of typed tables and views. These features will be covered from the perspective of a database designer or end user. In addition to presenting the features presently available in DB2 UDB V5.2, which became available in Fall 1998, we will discuss the expected evolution and impact of this technology over time."
"¡°Peer-to-peer¡± systems like Napster and Gnutella have recently become popular for sharing information. In this paper, we study the relevant issues and tradeoffs in designing a scalable P2P system. We focus on a subset of P2P systems, known as ¡°hybrid¡± P2P, where some functionality is still centralized. (In Napster, for example, indexing is centralized, and file exchange is distributed.) We model a file-sharing application, developing a probabilistic model to describe query behavior and expected query result sizes. We also develop an analytic model to describe system performance. Using experimental data collected from a running, publicly available hybrid P2P system, we validate both models. We then present several hybrid P2P system architectures and evaluate them using our model."
"We describe DataSplash, a direct manipulation system for creating semantic zoom visualizations of tabular (relational) data. DataSplash makes contributions in three areas that are key to the construction of such visualizations. First, DataSplash helps users graphically specify the visual appearance of groups of objects. Second, the system helps users visually program the way the appearance of groups of objects changes as users browse the visualization. Third, DataSplash allows users to create groups of graphical links between canvases."
"In this article we present DynaMat, a system that manages dynamic collections of materialized aggregate views in a data warehouse. At query time, DynaMat utilizes a dedicated disk space for storing computed aggregates that are further engaged for answering new queries. Queries are executed independently or can be bundled within a multiquery expression. In the latter case, we present an execution mechanism that exploits dependencies among the queries and the materialized set to further optimize their execution. During updates, DynaMat reconciles the current materialized view selection and refreshes the most beneficial subset of it within a given maintenance window. We show how to derive an efficient update plan with respect to the available maintenance window, the different update policies for the views and the dependencies that exist among them."
"It handles semistructured data, schema languages for XML, and traditional database models. The system is based on a ""metamodel"" approach, in the sense that it knows a set of metaconstructs,and allows the definition of models by means of the involved metaconstructs. The system also has a library of basic translations, referring to the known metaconstructs, and builds actual translations by means of suitable combinations of the basic ones."
"In this paper, we describe an architecture for an open marketplace exploiting the workflow technology and the currently emerging data exchange and metadata representation standards on the Web. In this market architecture electronic commerce is realized through the adaptable workflow templates provided by the marketplace to its users. Having workflow templates for electronic commerce processes results in a component-based architecture where components can be agents (both buying and selling) as well as existing applications invoked by the workflows. Other advantages provided by the workflow technology are forward recovery, detailed logging of the processes through workflow history manager and being able to specify data and control flow among the workflow components."
"On the Semantic Web, data will inevitably come from many different ontologies, and information processing across ontologies is not possible without knowing the semantic mappings between them. Manually finding such mappings is tedious, error-prone, and clearly not possible on the Web scale. Hence the development of tools to assist in the ontology mapping process is crucial to the success of the Semantic Web. We describe GLUE, a system that employs machine learning techniques to find such mappings. Given two ontologies, for each concept in one ontology GLUE finds the most similar concept in the other ontology."
"Most SQL-based XML vendor support is through interoperation and not integration. One reason for this is that XML is inherently hierarchical and SQL is supposedly not. This paper demonstrates how ANSI SQL along with its relational Cartesian product model can naturally perform complete and flexible hierarchical query processing. With this ANSI SQL inherent hierarchical processing capability, native XML data can be fully and seamlessly integrated into SQL processing and operated on at a full hierarchical level. This paper will describe the basic stages involved in this hierarchical SQL processing: hierarchical data modeling, hierarchical working set creation, and hierarchical Cartesian product processing. These processes enable a complete relational, XML, and legacy data integration which maintains ANSI SQL compatibility even while performing the most complex multi-leg hierarchical processing, and includes the dynamic, direct, and controlled hierarchical joining of hierarchical structures."
"The buffer pool manager is a central component of ADABAS, a high performance scaleable database system for OLTP processing. High efficiency and scalability of the buffer pool manager is mandatory for ADABAS on all supported platforms. In order to allow a maximum of parallelism without facing the danger of deadlocks, a multi-version locking method is used. Partitioning of central data structures is another key to performance. Variable page sizes allow for flexible tuning, but make the buffer pool logic more sophisticated, in particular concerning parallelism."
"One option is to use TCPdump to monitor a network port and a user-level application program to process the data. While this approach is very flexible, it is not fast enough to handle gigabit speeds on inexpensive equipment. Another approach is to use network monitoring devices. While these devices are capable of high speed monitoring, they are inflexible as the set of monitoring tasks is pre-defined. Adding new functionality is expensive and has long lead times. A similar approach is to use monitoring tools built into routers, such as SNMP, RMON, or NetFlow. These tools have similar characteristics --- fast but inflexible.A further problem with all of these tools is their lack of a query interface. The data from the monitors are dumped to a file or piped through a file stream without an association to the semantics of the data."
"Graph databases have aroused a large interest in the last years due to their large scope of potential applications (e.g., social networks, biomedical networks, data stemming from the web). However, much published data suffer from quality problems, and graph data are no exception. In this paper, we investigate the issue of dealing with quality information in graph databases, at querying time. A framework is provided that makes it possible to introduce fuzzy quality preferences into graph pattern queries. This question is answered first from a theoretical point of view and then with an application to the Neo4j database management system by the extension of the cypher query language, for which implementation issues are discussed."
"Despite the importance of spatial networks in real-life applications, most of the spatial database literature focuses on Euclidean spaces. In this paper we propose an architecture that integrates network and Euclidean information, capturing pragmatic constraints. Based on this architecture, we develop a Euclidean restriction and a network expansion framework that take advantage of location and connectivity to efficiently prune the search space. These frameworks are successfully applied to the most popular spatial queries, namely nearest neighbors, range search, closest pairs and e-distance joins, in the context of spatial network databases."
"Ultrahigh storage densities of up to 1 Tb/in2. or more can be achieved by using local-probe techniques to write, read back, and erase data in very thin polymer films. The thermomechanical scanning-probe-based data-storage concept, internally dubbed ""millipede"", combines ultrahigh density, small form factor, and high data rates. High data rates are achieved by parallel operation of large 2D arrays with thousands micro/nanomechanical cantilevers/tips that can be batch-fabricated by silicon surface-micromachining techniques. The inherent parallelism, the ultrahigh areal densities and the small form factor may open up new perspectives and opportunities for application in areas beyond those envisaged today."
"We propose and evaluate two indexing schemes for improving the efficiency of data retrieval in high-dimensional databases that are incomplete. These schemes are novel in that the search keys may contain missing attribute values. The first is a multi-dimensional index structure, called the Bitstring-augmented R-tree (BR-tree), whereas the second comprises a family of multiple one-dimensional one-attribute (MOSAIC) indexes. Our results show that both schemes can be superior over exhaustive search."
"Multidimensional inter-transactional association rules extend the traditional association rules to describe more general associations among items with multiple properties across transactions. ¡°After McDonald and Burger King open branches, KFC will open a branch two months later and one mile away¡± is an example of such rules. Since the number of potential inter-transactional association rules tends to be extremely large, mining inter-transactional associations poses more challenges on efficient processing than mining traditional intra-transactional associations. In order to make such association rule mining truly practical and computationally tractable, in this study we present a template model to help users declare the interesting multidimensional inter-transactional associations to be mined."
"We introduce a new algorithm (BOAT) for decision tree construction that improves upon earlier algorithms in both performance and functionality. BOAT constructs several levels of the tree in only two scans over the training database, resulting in an average performance gain of 300% over previous work. The key to this performance improvement is a novel optimistic approach to tree construction in which we construct an initial tree using a small subset of the data and refine it to arrive at the final tree."
"We present a continuously adaptive, continuous query (CACQ) implementation based on the eddy query processing framework. We show that our design provides significant performance benefits over existing approaches to evaluating continuous queries, not only because of its adaptivity, but also because of the aggressive cross-query sharing of work and space that it enables. By breaking the abstraction of shared relational algebra expressions, our Telegraph CACQ implementation is able to share physical operators --- both selections and join state --- at a very fine grain."
Several DBMS vendors have implemented the ANSI standard SQL isolation levels for transaction processing. This has created a gap between database practice and textbook accounts of transaction processing which simply equate isolation with serializability. We extend the notion of conflict to cover lower isolation levels and we present improved characterisations of classes of schedules achieving these levels.
"In this paper, we present visualizations of parts of the network of documents comprising the World Wide Web. We describe how we are using the Hy+ visualization system to visualize the portion of the World Wide Web explored during a browsing session. As the user browses, the web browser communicates the URL and title of each document fetched as well as all the anchors contained in the document. Hy+ displays graphically the history of the navigation and multiple views of the structure of that portion of the web."
"We present a framework for publishing relational data in XML with respect to a fixed DTD. In data exchange on the Web, XML views of relational data are typically required to conform to a predefined DTD. The presence of recursion in a DTD as well as non-determinism makes it challenging to generate DTD-directed, efficient transformations. Our framework provides a language for defining views that are guaranteed to be DTD-conformant, as well as middleware for evaluating these views. It is based on a novel notion of attribute translation grammars (ATGs). An ATG extends a DTD by associating semantic rules via SQL queries."
"Workload information has proved to be a crucial component for database-administration tasks as well as for analysis of query logs to understand user behavior and system usage. These tasks require the ability to summarize large SQL workloads. In this paper, we identify primitives that are important to enable many important workload-summarization tasks. These primitives also appear to be useful in a variety of practical scenarios besides workload summarization. Today's SQL is inadequate to express these primitives conveniently. We discuss possible extensions to SQL and the relational engine to efficiently support such summarization primitives."
"With today¡¯s demands for continuous availability of mission-critical databases, on-line reorganization is a necessity. In this paper we present a new on-Iine reorganization algorithm which defers secondary index updates and piggybacks them with user transactions. In addition to the significant reduction of the total I/O cost, the algorithm also assures that almost all the database is available all of the time and that the reorganization is interruptible and restartable. We believe that the technique presented in this paper could be used for improving normal database update performance as well."
"This article focuses on object-oriented databases (ODBs), providing a method aimed at supporting the designer in the construction of correct ODB schemas. The first necessary condition for schema correctness is the absence of contradictions. A second cause of schema incorrectness is due to the presence of structurally recursive types that, when defined within certain hierarchical patterns, cause the nontermination of the inheritance process. In the article, after the formal definition of a correct schema, two graph-theoretic methods aimed at verifying ODB schema correctness are analyzed. Although the first method is intuitive but inefficient, the second allows schema correctness to be checked in polynomial time, in the size of the schema."
"In the relational model the order of fetching data does not affect query correctness. This flexibility is exploited in query optimization by statically reordering data accesses. However, once a query is optimized, it is executed in a fixed order in most systems, with the result that data requests are made in a fixed order. Only limited forms of runtime reordering can be provided by low-level device managers. More aggressive reordering strategies are essential in scenarios where the latency of access to data objects varies widely and dynamically, as in tertiary devices. This paper presents such a strategy. Our key innovation is to exploit dynamic reordering to match execution order to the optimal data fetch order, in all parts of the plan-tree."
"This work has already created big performance wins in many real-world applications. Future holds a big set of challenges for real systems: to understand and improve the performance on DSS, Web and other application workloads, to optimize for response time, to handle VLDB, main memory database and other extreme environments, to handle automatic parallelism based on available hardware, to handle NUMA, cluster and other new hardware architectures, and eventually to build a self-tuning high-performance server."
"Database systems have enjoyed a tremendous market because they have served many applications really well -- transaction processing in the beginning, and then decision support. Today, with over 200% cumulative growth rate in certain segments of E-Commerce, it is clear that this new class of applications will be a strong driver for databases to grow, commercially, as well as from a Research perspective. This paper outlines some of the issues that I have learnt in dealing with E-Commerce applications that may well be the focus of some of the research in database systems over the course of next few years."
"In this paper, we propose APEX, an adaptive path index for XML data. APEX does not keep all paths starting from the root and utilizes frequently used paths to improve the query performance. APEX also has a nice property that it can be updated incrementally according to the changes of query workloads. Experimental results with synthetic and real-life data sets clearly confirm that APEX improves query processing cost typically 2 to 54 times better than the existing indexes, with the performance gap increasing with the irregularity of XML data."
"In this article, we address the problem of index configuration for a given path. We first summarize some basic concepts, and introduce the concept of index configuration for a path. Then we present cost formulas to evaluate the costs of the various configurations. Finally, we present the algorithm that determines the optimal configuration, and show its correctness."
"In this paper we propose techniques that solve the problem by performing a single query for the whole input segment. As a result the cost, depending on the query and dataset characteristics, may drop by orders of magnitude. In addition, we propose analytical models for the expected size of the output, as well as, the cost of query processing, and extend out techniques to several variations of the problem."
I am very happy writing to you for the first time as the TCCN Chair in the Newsletter. I would like to take this opportunity to introduce to you the newly elected officers for 2016 ¨C 2018
"Since the Web was not originally designed to support such applications, Web application development efforts increasingly run into limitations of the basic Web infrastructure.If the Web is to be used as the basis of complex enterprise applications, it must provide generic capabilities similar to those provided by the OMA (although these may need to be adapted to the more open, flexible nature of the Web, and specific requirements of Web applications)."
"We present HOMER, a CASE tool for building and maintaining complex, data-intensive Web sites. In HOMER the processes of creation and maintenance of a Web site are completely based on the adoption of suitable models, to describe the various aspects of the site (content~ navigation structure, presentation). The development of a site does not require any code writing activity: based on the results of the design process, the system automatically creates programs to implement the site, statically and/or dynamically, as needed; also, the system does not depend on any specific tool or language: it has a modular architecture, which integrates external servers for specific tasks; finally, the system supports site administrators for several maintenance activities, which can involve changes over the site at different levels."
"The performance of data-parallel algorithms for spatial operations using data-parallel variants of the bucket PMR quadtree, R-tree, and R+-tree spatial data structures is compared. The studied operations are data structure build, polygonization, and spatial join in an application domain consisting of planar line segment data. The algorithms are implemented using the scan model of parallel computation on the hypercube architecture of the Connection Machine. The results of experiments reveal that the bucket PMR quadtree outperforms both the R-tree and R+-tree. This is primarily because the bucket PMR quadtree yields a regular disjoint decomposition of space while the Rtree and R+-tree do not."
"In this talk, we will describe the usability challenges facing large distributed corporations. As well, we will discuss what IBM's DB2 Universal Database is doing to address these complex issues."
"Multi-tier infrastructures have become common practice for implementing high volume web sites. Such infrastructures typically contain TCP load balancers, HTTP servers, application servers, transaction-processing monitors, and databases. Caching has been widely used at different layers of the infrastructure stack to improve scalability and response time of e-business applications. The majority of existing caching mechanisms target only static HTML pages or page fragments. However, as web applications become more dynamic through increased personalization, these caching techniques turn out to be less useful. Consequently, as more application requests result in increased querying and updating of backend database servers, scalability limits are often reached."
"Translators (wrappers) convert queries over information in the common del (OEM) into requests the source can execute. The data returned by the source is converted back into the common model. Mediators are programs that collect information from one or more sources, process and combine it, and export the resulting information to the end user or an application program. Users or applications can choose to interact either directly with the translators or indirectly via one or more mediators."
"The wonderfully clean and beautiful scheme put ""on its head"" the world of query optimization I had assumed was the only one possible. In fact, this paper is all about questioning implicit assumptions behind classic query optimization. Is it always true that query-evaluation performance does not fluctuate during query execution?"
"This assumption is correct, but only up to a point: dimensional structures of different data warehouses in different organizations may be (and should be) different. But at the same time developers should be knowledgeable about certain methodological principles of dimensional modeling that are universal and do not vary from project to project and from company to company. The development of a such methodology and the summarization of experience in this area are challenging tasks, and only few authors have attempted to cover this complicated subject."
"We have implemented our algorithm and tested it on synthetic and real-world data. A number of experimental results are reported, showing the effectiveness of our algorithm at maximizing performance, and also showing that in the special case of exact caching our algorithm performs as well as previous algorithms. In cases where bounded imprecision is acceptable, our algorithm easily outperforms previous algorithms for exact caching."
"In this paper, we consider a very general form of semistructured data based on labeled, directed graphs. We show that such data can be typed using the greatest fixpoint semantics of monadic datalog programs. We present an algorithm for approximate typing of semistructured data. We establish that the general problem of finding an optimal such typing is NP-hard, but present some heuristics and techniques based on clustering that allow efficient and near-optimal treatment of the problem. We also present some preliminary experimental results."
"In contrast, we consider the alternative of extending existing symmetric binary join operators to handle more than two inputs. Toward this end, we have completed a prototype implementation of a multi-way join operator, which we term the ""MJoin"" operator, and explored its performance. Our results show that in many instances the MJoin produces outputs sooner than any tree of binary operators. Additionally, since MJoins are completely symmetric with respect to their inputs, they can reduce the need for expensive runtime plan reorganization."
"Fibonacci is an object-oriented database programming language characterized by static and strong typing, and by new mechanisms for modeling data-bases in terms of objects with roles, classes, and associations. A brief introduction to the language is provided to present those features, which are particularly suited to modeling complex databases. Examples of the use of Fibonacci are given with reference to the prototype implementation of the language."
"Our goal is to understand redo recovery. We define an installation graph of operations in an execution, an ordering significantly weaker than conflict ordering from concurrency control. The installation graph explains recoverable system state in terms of which operations are considered installed. This explanation and the set of operations replayed during recovery form an invariant that is the contract between normal operation and recovery. It prescribes how to coordinate changes to system components such as the state, the log, and the cache. We also describe how widely used recovery techniques are modeled in our theory, and why they succeed in providing redo recovery."
The property management database system under development at the Northern Ireland Housing Executive (NIHE) is a large relational database system. The application system has a high expected transaction processing rate approximately 37000 transactions per day (most of them accessing mutliple tables) from about 250 on-line users. Performance is of critical importance in its success. In this paper we consider the effect of the Ingres Search Accelerator on the transaction processing efficiency of the system.
"In many database applications, one of the common queries is to find approximate matches to a given query item from a collection of data items. For example, given an image database, one may want to retrieve all images that are similar to a given query image. Distance based index structures are proposed for applications where the data domain is high dimensional, or the distance function used to compute distances between data objects is non-Euclidean. In this paper, we introduce a distance based index structure called multi-vantage point (mvp) tree for similarity queries on high-dimensional metric spaces."
"In this paper, we demonstrate that a rich set of marketplace-specific services such as automated discovery of the needed services, comparison shopping, and negotiation can be offered to market participants by introducing a marketplace as an eCo business. For this purpose, a previously developed marketplace, namely MOPPET, is made eCo-compliant. We demonstrate that introducing MOPPET as an eCo business increases the functionality of the eCo market in the sense that several market specific services become available to the market participants."
"The Annual SIGMOD and PODS Awards honor important contributors to the database field. The awards are presented at the annual SIGMOD/PODS Conference. For those of you who missed that presentation at the 2001 conference, this article reports on this year¡¯s winners. Congratulations to all of them for these significant achievements."
"Our initial studies of Broadcast Disks focused on the performance of the mechanism when the data being broadcast did not change. In this paper, we extend those results to incorporate the impact of updates. We first propose several alternative models for updates and examine the fundamental tradeoff that arises between the currency of data and performance. We then propose and analyze mechanisms for implementing these various models. The performance results show that, even in a model where updates must be transmitted immediately, the performance of the Broadcast Disks technique can be made quite mbust through the use of simple techniques for propagating and prefetching data items."
"We enunciate the need for watermarking database relations to deter data piracy, identify the characteristics of relational data that pose unique challenges for watermarking, and delineate desirable properties of a watermarking system for relational data. We then present an effective watermarking technique geared for relational data. This technique ensures that some bit positions of some of the attributes of some of the tuples contain specific values. The specific bit locations and values are algorithmically determined under the control of a secret key known only to the owner of the data. This bit pattern constitutes the watermark. Only if one has access to the secret key can the watermark be detected with high probability."
"The Journal is a quarterly publication of the VLDB Endowment. As a database systems journal it is dedicated to the international publication of scholarly contributions to the advancement of information system architectures, the impact of emerging technologies on information systems, and the development of novel applications. It presents significant advances in the design, implementation, and evaluation of systems for databases and for other information collections Its scope ranges from the development of special-purpose hardware, the design of innovative software approaches, integrated system architectures, the design analysis and performance evaluation of systems to new techniques for presenting and capturing information."
"The Laboratory of Database Applications Engineering (LIBD) is devoted to the development of models, techniques, methods and tools to support all the engineering activities related to databases and their applications. It also develops material and activities to transfer database knowledge towards industry. This report describes the main activities of the laboratory during the last ten years. It first discusses general resources and processes that form the baselines for the other research activities. The latter will be classified into reverse engineering, interoperability, advanced processes and CASE technology."
"The principal objective of this paper has been to suppress this drawback while conserving the strong correctness of 2LSR executions We propose defining precisely the notion of value dependencies, and managing them so as not to impose the LDP property."
"In this paper we present the Application Manifold system, aimed at simplifying the intricate task of integration and customization of e-commerce applications. The scope of the work in this paper is limited to web-enabled e-commerce applications. We do not support the integration/customization of proprietary/legacy applications. The wrapping of such applications as web services is complementary to our work. Based on the emerging Web data standard, XML, and application modeling standard, UML, the system offers a novel declarative specification language for describing the integration/customization task, supporting a modular approach where new applications can be added and integrated at will with minimal effort."
"We introduce a semantic data model to capture the hierarchical, spatial, temporal, and evolutionary semantics of images in pictorial databases. This model mimics the user's conceptual view of the image content, providing the framework and guidelines for preprocessing to extract image features. Based on the model constructs, a spatial evolutionary query language (SEQL), which provides direct image object manipulation capabilities, is presented. With semantic information captured in the model, spatial evolutionary queries are answered efficiently. Using an object-oriented platform, a prototype medical-image management system was implemented at UCLA to demonstrate the feasibility of the proposed approach."
"Wireless and mobile computing have advanced significantly in the last decade. In particular, we now face the challenge to spontaneously establish wireless self-organizing networks, such as ad hoc, disruption-tolerant, sensor, and wireless mesh networks. These spontaneous self-organizing networks have been the focus of intensive research activity in recent years. Spontaneous networks arise from the cooperation of mobile devices in an ad hoc fashion requiring no previous infrastructure in place. A key point to couple research and real-life applications in this context is to understand how mobility (of devices, users, and applications) impacts practical networking aspects"
"This contribution argues that electronic markets can serve as a powerful mechanism to entice providers to identify their customer base and to offer customer-oriented, high-quality and economical services and to induce customers to a more focused and price-conscious behavior. The paper claims that this should be particularly true for the provision and access to scientific literature where the tradition so far has been mostly free access by customers and non-transparent cost accounting and service procurement by university libraries. We report on a project for developing a technical network infrastructure that allows for a more cost-transparent access to scientific literature by campus users and attempts to add a competitive element to library services. Equally important, it provides added value to the users so that they can orient themselves in the vast expanses of scientific literature much faster and more economically. We cover three major elements of the infrastructure: user agents, traders and source wrappers."
"This paper builds on altruistic locking which is an extension of 2PL. It allows more relaxed rules as compared to 2PL. But altruistic locking too enforces some rules which disallow some valid schedules (present in VSR and CSR) to be passed by AL. This paper proposes a multiversion variant of AL which solves this problem. The report also discusses the relationship or comparison between different protocols such as MAL and MV2PL, MAL and AL, MAL and 2PL and so on. This paper also discusses the caveats involved in MAL and where it lies in the Venn diagram of multiversion serializable schedule protocols."
"We show how careful interspersing of queries and informed cache management can achieve rema.rkable reductions in access time compared 1x1 conventional methods. Our algoril(hms use a few model pa.rameters for each tertiary memory device and are thus designed to be portable across a wide variety of tert,ia.ry memory devices and da,tnhase t,ypes. We arc extending the PoS¡¯TGR.ES database system to implements the new query processing strategics. Jnit,ial mea.surements on the prototype yield impressive results."
"In this paper, we first discuss the current practices and trends in component-based electronic commerce based on the International Workshop on Component-based Electronic Commerce. Then, we investigate a number of research issues and future directions in component-based development for electronic commerce."
"In matching problems, given a pattern, a set of data objects and a distance metric, we find the distance between the pattern and one or more data objects. In discovery problems by contrast, given a set of objects, a metric, and a distance, we seek a pattern that matches many of those objects within the given distance. (So, discovery is a lot like data mining.) Our toolkit performs both matching and discovery with current targeted applications in molecular biology and document comparison."
"In the era of Internet of Things (IoT), a number of things are efficiently interconnected in order to combine, integrate the physical world to the information space. One of the application domains of urban IoT is smart grid where smart buildings, smart homes, vehicles, electrical grids, power plants, other components are interconnected to provide the services in an efficient way."
"This paper describes XDB-IPG, an open and extensible database architecture that supports efficient and flexible integration of heterogeneous and distributed information resources. XDB-IPG provides a novel ¡°schema-less¡± database approach using a document-centered object-relational XML database mapping. This enables structured, unstructured, and semi-structured information to be integrated without requiring document schemas or translation tables. XDB-IPG utilizes existing international protocol standards of the World Wide Web Consortium Architecture Domain and the Internet Engineering Task Force, primarily HTTP, XML and WebDAV ."
"Gifford¡¯s basic Quorum Consensus algorithm for data replication is generalized to accommodate nested transactions and transaction failures (aborts), A formal description of the generalized algorithm is presented using the new Lynch-Merritt inputoutput automaton model for nested transaction systems. This formal description is used to construct a complete (yet simple) proof of correctness that uses standard assertional techniques and is based on a natural correctness condition."
"In this article, we model and verify a data manager whose algorithm is based on ARIES. The work uses the I/O automata method as the formal model and the definition of correctness is defined on the interface between the scheduler and the data manager."
"Conventional spatial queries are usually meaningless in dynamic environments since their results may be invalidated as soon as the query or data objects move. In this paper we formulate two novel query types, time parameterized and continuous queries, applicable in such environments. A time-parameterized query retrieves the actual result at the time when the query is issued, the expiry time of the result given the current motion of the query and database objects, and the change that causes the expiration."
"The rapid growth of the Internet and support for interoperability protocols has increased the number of Web accessible sources, WebSources. Current wrapper mediator architectures need to be extended with a wrapper cost model (WCM) for WebSources that can estimate the response time (delays) to access sources as well as other relevant statistics. In this paper, we present a Web prediction tool (WebPT), a tool that is based on learning using query feedback from WebSources. The WebPT uses dimensions time of day, day, and quantity of data, to learn response times from a particular WebSource, and to predict the expected response time (delay) for some query."
"In this paper, our research objective is to develop a database virtualizat ion technique in order to let data analysts or other users who apply data mining methods to their jobs use all ubiquitous databases on the Internet as if they were recognized as a single database, thereby helping to reduce their workloads such as data collection from the Internet databases and data cleansing works. In this study, firstly we examine XML schema advantages and propose a database virtualizat ion method by which such ubiquitous databases as relational databases, object-oriented databases, and XML databases are accessed as if they all behave as a single database."
"In this article, we describe techniques for time management for new faculty members, covering a wide range of topics ranging from advice on scheduling meetings, email, to writing grant proposals and teaching."
"In a 'shared-nothing' parallel computer, each processor has its own memory and disks and processors communicate by passing messages through an interconnect. Many academic researchers, and some vendors, assert that shared-nothingness is the 'consensus' architecture for parallel DBMSs. This alleged consensus is used as a justification for simulation models, algorithms, research prototypes and even marketing campaigns. We argue that shared-nothingness is no longer the consensus hardware architecture and that hardware resource sharing is a poor basis for categorising parallel DBMS software architectures if one wishes to compare the performance characteristics of parallel DBMS products."
"Large web search engines have to answer thousands of queries per second with interactive response times. A major factor in the cost of executing a query is given by the lengths of the inverted lists for the query terms, which increase with the size of the document collection and are often in the range of many megabytes. To address this issue, IR and database researchers have proposed pruning techniques that compute or approximate term-based ranking functions without scanning over the full inverted lists."
"The abfity to optimize queries is considered one of the key enabling technologies for relational databases and is an active area in research and development. There continues to be work in discovering new transformations for SQL. The problem of building extensible query optimizers continues to draw a lot of attention, not only in academic research but also in commercial development."
"The goal of STRUDEL project is to extend and adapt these concepts to the problem of Web-site management. Consider several tasks required of a Web-site manager. Site managers often want to manage a single repository of site data, but present different browsable ¡°views¡± of the site based on criteria such as the type of user accessing the site, e.g., external or internal, expert or novice. Morever, a manager might want to modify the data repository by editing simple text files or by updating external databases, to reorganize the structure of the pages by manipulating graphs that represent the linked pages, or to design multiple presentations of a single page by editing HTML files or by using a WYSIWYG HTML generator."
Program Committee W. Anheier (DE) S. Aunet (NO) M. Bal¨¢? (SK) S. Bernard (FR) T. Borejko (PL) D. Borrione (FR) A. Bosio (FR) G. Carlsson (SE) M. Dan¨§k (CZ) A. D?browski (PL) M. Dietrich (DE) R. Drechsler (DE) M. Drutarovsky (SK) P. Ellervee (EE) G. Fey (DE) J. Figueras (ES) P. Fi?er (CZ) P. F?ldesy (HU) M. F¨¹gger (AT)
"In this paper, we explore some performance implications of both options using native implementations in two commercial relational database systems and in a special purpose inverted list engine. Our performance study shows that while RDBMSs are generally poorly suited for such queries, under conditions they can outperform an inverted list engine. Our analysis further identifies two significant causes that differentiate the performance of the IR and RDBMS implementations: the join algorithms employed and the hardware cache utilization. Our results suggest that contrary to most expectations, with some modifications, a native implementations in an RDBMS can support this class of query much more efficiently."
"In this paper, we introduce an approach that supports querying for Semantic Associations on the Semantic Web. Semantic Associations capture complex relationships between entities involving sequences of predicates, and sets of predicate sequences that interact in complex ways. Detecting such associations is at the heart of many research and analytical activities that are crucial to applications in national security and business intelligence. This in combination with the improving ability to identify entities in documents as part of automatic semantic annotation, gives a very powerful capability for semantic analysis of large amounts of heterogeneous content."
"A repository is a shared database of information about engineered artifacts. An object-oriented repository has many of the same features as an object-oriented database: properties, relationships, and versioning. However, the two technologies are different for two reasons. First, a repository system has built-in information models, which are database schemas or object models that cover both generic and tool-specific kinds of information. Second, the features of a repository are often more functional than similar features supported by object-oriented databases. This paper is primarily a survey of the latter features, drawing attention to capabilities that distinguish repositories from object-oriented databases."
"The Office of Health Promotion and Disease Prevention has a budget so small that very few health promotion professionals ever encounter this office directly during their careers. The Centers for Disease Control and Prevention (CDC) are charged with coordinating the government¡¯s health promotion efforts but with the exception of some well funded and very important programs in tobacco control, and despite the strong interests of many staff members, CDC does very little to advance health promotion."
The yellow pages service of GTE SuperPages enables Web users to flexibly search through liitings of 11 million businesses in over 17000 categories. To achieve the flexibility desired it uses an Information Retrieval (IR) engine to search through complex listing objects. The objects themselves are stored in an object database. The use of the IR engine enables us to create an index that spans all the components of a complex object.
"We consider spatio-temporal databases supporting spatial objects with continuously changing position and extent, termed moving objects databases. We formally define a data model for such databases that includes complex evolving spatial structures such as line networks or multi-component regions with holes. The data model is given as a collection of data types and operations which can be plugged as attribute types into any DBMS data model (e.g. relational, or object-oriented) to obtain a complete model and query language. A particular novel concept is the sliced representation which represents a temporal development as a set of units, where unit types for spatial and other data types represent certain ¡°simple¡± functions of time. We also show how the model can be mapped into concrete physical data structures in a DBMS environment."
"Middle East Technical University (METU) is the leading technical university in Turkey. The Software Research and Development Center was established by the Scientific and Technical Research Council of Turkey (TUBITAK) at the Department of Computer Engineering of METU in October 1991. The aim of this center is twofold: to lead large scale software research and development projects, and to foster international cooperation. SRDC is involved in a number of research and development projects supported by the government, industrial companies and international organizations. Although SRDC projects also cover other fields of computer science, the main emphasis is on database systems."
"In this paper, an indexing technique based on HMMs is proposed. The new index is a variation of the trie data structure that uses HMMs and a new search algorithm to provide approximate matching. Each node in the tree contains handwritten letters, where each letter is represented by an HMM. Branching in the trie is based on the ranking of matches given by the HMMs. The new search algorithm is parametrized so that it provides means for controlling the matching quality of the search process via a time-based budget. The index dramatically improves the search time in a database of handwritten words. Due to the variety of platforms for which this work is aimed, ranging from personal digital assistants to desktop computers, we implemented both main-memory and disk-based systems."
"In June 1997, an international workshop on engineering of federated database systems has been held in Barcelona in conjunction with the 9th Conference on Advanced Information Systems Engineering (CAiSE'97). This paper reports on the results of this workshop and summarises the identified open issues for future research in this area."
"In this paper, we present a formal study of dynamic multidimensional histogram structures over continuous data streams. At the heart of our proposal is the use of a dynamic summary data structure (vastly different from a histogram) maintaining a succinct approximation of the data distribution of the underlying continuous stream. On demand, an accurate histogram is derived from this dynamic data structure. We propose algorithms for extracting such an accurate histogram and we analyze their behavior and tradeoffs. The proposed algorithms are able to provide approximate guarantees about the quality of the estimation of the histograms they extract."
"Two well-known indexing methods are inverted files and signature files. We have undertaken a detailed comparison of these two approaches in the context of text indexing, paying particular attention to query evaluation speed and space requirements. We have examined their relative performance using both experimentation and a refined approach to modeling of signature files, and demonstrate that inverted files are distinctly superior to signature files. Not only can inverted files be used to evaluate typical queries in less time than can signature files, but inverted files require less space and provide greater functionality. Our results also show that a synthetic text database can provide a realistic indication of the behavior of an actual text database."
"This paper presents a set of aggregation algorithms on very large compressed data warehouses for multidimensional OLAP. These algorithms operate directly on compressed datasets without the need to first decompress them. They are applicable to data warehouses that are compressed using variety of data compression methods. The algorithms have different performance behavior as a function of dataset parameters, sizes of outputs and main memory availability. The analysis and experimental results show that the algorithms have better performance than the traditional aggregation algorithms."
"In this paper, we examine presentations in three different domains (heavyweight, middleweight, and lightweight) and provide buffer management and admission control algorithms for the three domains. We propose two improvements (flattening and dynamic-adjustments) on the schedules created for the heavyweight presentations. Results from a simulation environment are presented."
The Summary Schemas Model (SSM) is proposed as an extension to multidatabase systems to aid in semantic identification. The SSM uses a global data structure to abstract the information available in a multidatabase system. This abstracted form allows users to use their own terms (imprecise queries) when accessing data rather than being forced to use system-specified terms. The system uses the global data structure to match the user's terms to the semantically closest available system terms. A simulation of the SSM is presented to compare imprecise-query processing with corresponding query-processing costs in a standard multidatabase system.
"The chair of ACRP¡¯s Association Board of Trustees recounts how he left manufacturing and research and development a decade ago to take a position as a clinical research administrator. It was a move that place him into a role he knew little about, having not been engaged in clinical research beforehand. If this sounds like a familiar experience to others, the lessons shared in this column highlight the importance of the individual¡¯s ongoing will to learn, and of organizational support for that learning."
"In this column, we review these three books: 1. The Problem With Software: Why Smart Engineers Write Bad Code, by Adam Barr. Answers to a question many of us have probably asked; and what we can do about it. Review by Shoshana Marcus. 2. Elements of Parallel Computing, by Eric Aubanel. A textbook on the underpinnings of this important and fascinating area of computer science. Review by Michele Amoretti. 3. Theorems of the 21st Century: Volume I, by Bogdan Grechuk. The background, context, and statement of numerous important (accessible) mathematical theorems from the past 20 years. Review by William Gasarch."
"This paper studies five strategies for storing XML documents including one that leaves documents in the file system, three that use a relational database system, and one that uses an object manager. We implement and evaluate each approach using a number of XQuery queries. A number of interesting insights are gained from these experiments and a summary of the advantages and disadvantages of the approaches is presented."
"Conjwzctiue queries are queries over a relational database and are at the core of relational query languages such as SQL. Testing for containment (and equivalence) of such queries arises as part of many advanced features of query optimization, for example, using rnateriahzed views, processing correlated nested queries, semantic query optimization, and global query optimization. Earlier formal work on the topic has examined conjunctive queries over sets of tuples, where each query can be viewed as a function from sets to sets. Containment (and equivalence) of conjunctive queries has been naturally defined based on set mcluslon and has been shown to be an NP-complete problem. Even in SQL, however, queries over multzsets of tuples may be posed."
"Technology and education have wandered many separate but rarely intersecting paths throughout the 20th Century. In the 21st Century, the convergence of cost effective computing and networking products, methodologies, and services is finally enabling more researchers and practitioners than ever before to explore innovative ways to use computer technologies to manage and enhance the teaching and learning experience. Recognizing the importance of these trends, this Special Section solicited submissions belonging to one or all of the three mainstream learning domains, i.e., contents, methodologies, and technologies, addressing the above convergence in matters related, for example, to openness (e.g., source, access, and educational resources), online and hybrid or blended individualized and group instruction, collaborative methodologies, adaptive learning, Big Data and cloud computing applications in education, mobile learning, educational technology standards and social issues (e.g., privacy and security)."
"To solve this problem, we first present an aggregation computation model, called the Disjoint-Inclusive Partition (DIP) computation model, that is the formal basis of our approach. Based on this model, we then present the one-pass aggregation algorithm. This algorithm computes aggregations using the one-pass buffer size, which is the minimum buffer size required for guaranteeing one disk access per page. We prove that our aggregation algorithm is optimal with respect to the one-pass buffer size under our aggregation computation model. Using the DIP computation model allows us to correctly predict the order of accessing data pages in advance. Thus, our algorithm achieves the optimal one-pass buffer size by using a buffer replacement policy, such as Belady's B0 or Toss-Immediate policies, that exploits the page access order computed in advance."
"We present here a new vertical mining algorithm called VIPER, which is general-purpose, making no special requirements of the underlying database. VIPER stores data in compressed bit-vectors called ¡°snakes¡± and integrates a number of novel optimizations for efficient snake generation, intersection, counting and storage. We analyze the performance of VIPER for a range of synthetic database workloads. Our experimental results indicate significant performance gains, especially for large databases, over previously proposed vertical and horizontal mining algorithms. In fact, there are even workload regions where VIPER outperforms an optimal, but practically infeasible, horizontal mining algorithm."
"We are witnessing an explosion in the volume and complexity of digital information that people want to access and analyze. Much of this data is ¡°multi-media¡± like images, video, audio, and documents. Several other kinds of complex and semi-structured data are also important, including geographical objects, chemical and biological structures, mathematical entities like matrices and equations, and financial data like time-series. Databaae systems must efficiently support queries over such richly structured datw otherwise, they will fast become ¡°roadklll on the information super-highway¡±. PREDATOR is an object-relational DBMS being developed at Cornell University. It uses a novel ¡°Enhanced ADT¡± (E-ADT) technology to meet this challenge."
"The Real-Time Database Systems (RTDBSs) Project at Bilkent University is concerned with varIous aspects of transaction scheduling in RTDBSs. Within the REACH (REal-time, Active and Heterogeneous Systems) Project at Darmstadt we have been working on engineering real-time DBMSs on top of the Chorus RTOS with a special emphasis on ~eroviding predictability and the ability to map highvel RT-protocols to basic RTOS schedulers. We are also working on combining active and real-time functionality [2]. Recently, both groups started to cooperate. The work described in this paper is joint work that resulted from this cooperation. Predictability of transaction execution is a basic issue in RTDBSs."
"Exact answers NOT always required : DSS applications usually exploratory: early feedback to help identify ¡°interesting¡± regions Aggregate queries: precision to ¡°last decimal¡± not needed e.g., ¡°What are the total sales of product X in NJ?¡± Base data can be remote or unavailable: approximate processing using locally-cached data synopses is the only option"
"Mapping to one-dimensional values and then using a one-dimensional indexing method has been proposed as a way of indexing multi-dimensional data. Most previous related work uses the Z-Order Curve but more recently the Hilbert Curve has been considered since it has superior clustering properties. Any approach, however, can only be of practical value if there are effective methods for executing range and partial match queries. This paper describes such a method for the Hilbert Curve."
"The problem of answering queries using views is to find efficient methods of answering a query using a set of previously materialized views over the database, rather than accessing the database relations. The problem has recently received significant attention because of its relevance to a wide variety of data management problems, such as query optimization, the maintenance of physical data independence, data integration and data warehousing. This article surveys the theoretical issues concerning the problem of answering queries using views"
"The land use categories of the Global Land Cover 2000 (GLC2000; Global Land Cover 2000 database, 2003, European Commission, Joint Research Centre; resolution 1 km) are then calibrated with the Swiss dataset in order to derive a Europe-wide birch distribution dataset and aggregated onto the 7 km COSMO-ART grid. This procedure thus assumes that a certain GLC2000 land use category has the same birch density wherever it may occur in Europe. In order to reduce the strict application of this crucial assumption, the birch density distribution as obtained from the previous steps is weighted using the mean Seasonal Pollen Index (SPI; yearly sums of daily pollen concentrations). For future improvement, region-specific birch densities for the GLC2000 categories could be integrated into the mapping procedure."
"We propose a framework for enforcing access control policies on published XML documents using cryptography. In this framework the owner publishes a single data instance, which is partially encrypted, and which enforces all access control policies. Our contributions include a declarative language for access policies, and the resolution of these policies into a logical ""protection model"" which protects an XML tree with keys. The data owner enforces an access control policy by granting keys to users. The model is quite powerful, allowing the data owner to describe complex access scenarios, and is also quite elegant, allowing logical optimizations to be described as rewriting rules. Finally, we describe cryptographic techniques for enforcing the protection model on published data, and provide a performance analysis using real datasets."
"We develop novel query processing algorithms that operate directly on the wavelet-coefficient synopses of relational tables, allowing us to process arbitrarily complex queries entirely in the wavelet-coefficient domain. This guarantees extremely fast response times since our approximate query execution engine can do the bulk of its processing over compact sets of wavelet coefficients, essentially postponing the expansion into relational tuples until the end-result of the query. We also propose a novel wavelet decomposition algorithm that can build these synopses in an I/O-efficient manner. Finally, we conduct an extensive experimental study with synthetic as well as real-life data sets to determine the effectiveness of our wavelet-based approach compared to sampling and histograms."
"This paper addresses the problem of evaluating ranked top-k queries with expensive predicates. As major DBMSs now all support expensive user-defined predicates for Boolean queries, we believe such support for ranked queries will be even more important: First ranked queries often need to model user-specific concepts of preference, relevance, or similarity, which call for dynamic user-defined functions. Second, middleware systems must incorporate external predicates for integrating autonomous sources typically accessible only by per-object queries. Third, fuzzy joins are inherently expensive, as they are essentially user-defined operations that dynamically associate multiple relations."
"The increasing power of modern computers is steadily opening up new application domains for advanced data processing such as engineering and knowledge-based applications. To meet their requirements, concepts for advanced data management have been investigated during the last decade, especially in the field of object orientation. Over the last couple of years, the database group at the University of Kaiserslautern has been developing such an advanced database system, the KRISYS prototype. In this article, we report on the results and experiences obtained in the course of this project. The primary objective for the first version of KRISYS was to provide semantic features, such as an expressive data model, a set-oriented query language, deductive as well as active capabilities. The first KRISYS prototype became completely operational in 1989."
"On behalf of the computer department at the Faculty of Engineering, Alexandria University, EGYPT, I would like to take this opportunity to acknowledge, with great appreciation, the book donations during SIGMOD 2001, Santa Barbara and the help of the SIGMOD community at large. We especially acknowledge SIGMOD member's contribution, and the donations by publishers."
"In this issue we briefly touch on the continuing turmoil over NSF, ARPA, and HPCC, and the brighter news regarding the US National Information Infrastructure plan. We then describe funding opportunities from NSF, ARPA, the National Security Agency, the National Center for Automated Information Research, the Air Force, and NASA."
"In this work, we utilize the knowledge of scope relationship of relations in multidatabases to identify the sites that will return the same results. Then, we propose a novel way of optimizing queries which takes advantage of the conflicts of schemas in searching for the execution plan with the least execution cost. We achieve the goal by first classifying various schema conflicts into different types. The costs of executing the same relational operation on relations of conflicting schemas are evaluated and a weight is assigned to each of the cases to reflect the complexity of executing the operation. As this method only involves simple iterative computations of the weights and the saving of a query execution time can be dramatic, the method developed here can be regarded as an effective way of optimizing query processing in a multidatabase environment."
"However, in the context of in-memory searches, we find that the traditional notion of considering good trajectory splits by minimizing the volume of MBBs so as to reduce index overlap is not well-suited to improve the performance of in-memory distance threshold searches. Another finding is that computing good trajectory splits to achieve a trade-off between the time to search the index-tree and the time to process the candidate set of trajectory segments may not be beneficial when considering large datasets. The GPU is an attractive technology for distance threshold searches because of the inherent data parallelism involved in calculating moving distances between pairs of polylines; however, challenges arise from the SIMD programming model and limited GPU memory. We study the processing of distance threshold searches using GPU implementations that avoid the use of index-trees."
"What is English Query? Microsoft English Query (EQ) lets users pose database queries in plain English. To do this, a developer need only define the database semantics, in effect building a conceptual model of the database. EQ provides an Authoring Tool that allows the developer to define the set of the entities and relationships in the database along with the database objects that the entities are associated with. Once this model is defined, the English Query Engine converts any English question posed in terms of the defined entities and relationships into a SQL statement. The application developer may use this engine, specifically it¡¯s a COM automation server, inside her Web, C++, Java, or Visual Basic application."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
"Relational query optimizers have traditionally relied upon table cardinalities when estimating the cost of the query plans they consider. While this approach has been and continues to be successful, the advent of the Internet and the need to execute queries over streaming sources requires a different approach, since for streaming inputs the cardinality may not be known or may not even be knowable (as is the case for an unbounded stream.) In view of this, we propose shifting from a cardinality-based approach to a rate-based approach, and give an optimization framework that aims at maximizing the output rate of query evaluation plans. This approach can be applied to cases where the cardinality-based approach cannot be used. It may also be useful for cases where cardinalities are known, because by focusing on rates we are able not only to optimize the time at which the last result tuple appears, but also to optimize for the number of answers computed at any specified time after the query evaluation commences."
In this extended abstract we briefly describe EMC's information sharing technology that enables UNIX and NT systems to directly access MVS mainframe datasets and how this technology can be used to directly access an MVS DB2 database.
"The extensions support new data types such as point, circle, etc., and functions such as confains, interval, text-contains, etc. Let the tables Policies (policy-id, name, address, location, vehicle-type, . . .) and Claims (policy-id, claim-tag, accident-date, accident-location, accident-report, . . .) represent the partial schema containing both SQL¡¯92 and user defined data types (UDTs). Consider a scenario in a targeted marketing application that requires a mailing list of all customers within 5 miles of point L, who have insured a ¡®sports utility vehicle¡¯ and were involved in a ¡®rear-ended¡¯ accident in the past 3 years."
"Part I: Foundations: Concepts and Business Models Chapter 1: Background, Terminology, Opportunity, and Challenges Chapter 2: Business-to-Consumer Data Warehousing Chapter 3: Data Warehousing for Consumer-to-Consumer and Consumer-to-Business Models Chapter 4: Business-to-Business Data Warehousing Chapter 5: e-Government and Data Warehousing Chapter 6: Business-to-Employee Models and Data Warehousing Part II: Building Blocks, Challenges, and Solutions Chapter 7: Core Technologies and Building Blocks Chapter 8: Products for e-Commerce Intelligence Chapter 9: Data Quality and Integrity Issues Chapter 10: Information Privacy and Systems Security Issues for e-Commerce Environments Chapter 11: Solutions Architecture Case Study"
"In this paper, we show how probabilistic graphical models can be effectively used for this task as an accurate and compact approximation of the joint frequency distribution of multiple attributes across multiple relations. Probabilistic Relational Models (PRMs) are a recent development that extends graphical statistical models such as Bayesian Networks to relational domains. They represent the statistical dependencies between attributes within a table, and between attributes across foreign-key joins. We provide an efficient algorithm for constructing a PRM front a database, and show how a PRM can be used to compute selectivity estimates for a broad class of queries. One of the major contributions of this work is a unified framework for the estimation of queries involving both select and foreign-key join operations."
"The project MENTAS (Motor Development Assistant) -aims at realizing an interconnected, engineer-oriented development environment for a faster conception and comparative analysis of motors. In order to reach this goal, an integrated access to multi-vendor DBs is provided. In our exhibition we demonstrate how the interconnection of heterogeneous DBs in MENTAS works. After having analyzed the data models of each such DBs, we have brought the heterogeneous schemas into a global, virtual one, which contains just the data relevant for MENTAS. Finally, we apply a commercially available DB middleware solution to bridge the diverse ontologies and hence to cope with these heterogeneous schemas. Furthermore, we have designed a very friendly GUI in Java by means of which users are guided in the process of formulating SQL queries. We show how this interface allows users to issue SQL statements against any DBs incorporated in the federation, to navigate through heterogeneous DBs, and most importantly, to join and compare data in the DB federation."
"XML tries to bring to natural language documents (""texts"" for short), some of what databases have had for decades: explicit structure whose properties can be known; independence of data and structure from reporting (which we foreigners call ""formatting""); various kinds of isolation; and so on. But the data buried in those XML elements is weird stuff: deep hierarchies, arbitrary and unpredictable orderings and repetitions, a painful number of atomic types, and enough aggregates to make one's head hurt."
"Table of contentsI1 Proceedings of the 4th World Conference on Research IntegrityConcurrent Sessions:1. Countries' systems and policies to foster research integrityCS01.1 Second time around: Implementing and embedding a review of responsible conduct of research policy and practice in an Australian research-intensive universitySusan Patricia O'BrienCS01.2 Measures to promote research integrity in a university: the case of an Asian universityDanny Chan, Frederick Leung2. Examples of research integrity education programmes in different countriesCS02.1 Development of a state-run ¡°cyber education program of research ethics¡± in KoreaEun Jung Ko, Jin Sun Kwak, TaeHwan Gwon, Ji Min Lee, Min-Ho LeeCS02.3 Responsible conduct of research teachers¡¯ training courses in Germany: keeping on drilling through hard boards for more RCR teachersHelga Nolte, Michael Gommel, Gerlinde Sponholz3. The research environment and policies to encourage research integrity"
"Previous research has demonstrated that space can be saved in a MultiMedia DataBase Management System (MMDBMS) by storing some of the data items virtually, meaning they are stored as sequences of editing operations. The existing approaches for performing ContentBased Retrieval (CBR) in an MMDBMS, however, typically assume that the data items are stored as large, binary objects. The result is that an MMDBMS cannot use the existing approaches without losing the space savings gained by storing the data items virtually. In our demo, we present a prototype CBR system for virtual images that avoids this problem by using the semantic information in the editing operations during retrieval."
"Workflow management systems (WfMSs) are software platforms that allow the definition, execution, monitoring, and management of business processes. WfMSs log every event that occurs during process execution. Therefore, workflow logs include a significant amount of information that can be used to analyze process executions, understand the causes of high - and low-quality process executions, and rate the performance of interna l resources and business partners. In this paper we present a packaged data warehousing solution, coupled with HP Process Manager, for collecting and analyzing workflow execution data. We first present the main challenges involved in this effort, and then detail the proposed approach."
"We deal first with the case of perfectly declustered queries, i.e., queries which retrieve a fixed proportion of the answer from each disk. We show that the fraction of the dataset which must be allocated to each disk is affected by both the relative speed and capacity of the disk. Furthermore, the hierarchical structure of most distributed systems, where groups of disks are placed in servers, imposes further complications due to variations . in server and network bandwidths which may affect the actual achievable transfer rates. We propose an algorithm which determines the fraction of the dataset which must be loaded on each disk. The algorithm may be tailored to find disk loading for minimal response time for a given database size, or to compute a system profile showing the optimal loading of the disks for all possible ranges of database sizes."
"In this paper, we describe a novel Web query processing approach with learning capabilities. Under this approach, user queries are in the form of keywords and search engines are employed to find URLs of Web sites that might contain the required information. The first few URLs are presented to the user for browsing. Meanwhile, the query processor learns both the information required by the user and the way that the user navigates through hyperlinks to locate such information. With the learned knowledge, it processes the rest URLs and produces precise query results in the form of segments of Web pages without user involvement. The preliminary experimental results indicate that the approach can process a range of Web queries with satisfactory performance. The architecture of such a query processor, techniques of modeling HTML pages, and knowledge for query processing are discussed."
"In a digital library one of the most challenging problems is finding relevant information. Information finding is the research focus of the Stanford component of the ARPA-sponsored CS-TR Project, and the work has continued as one of the main thrusts in the Stanford Integrated Digital Library project [14]. In this paper we discuss some of the emerging issues in information finding, such as text-database discovery, efficient information dissemination, and copy detection and removal. We also outline our approaches to these issues."
"In this paper, we present an image retrieval system that employs both the color and spatial information of images to facilitate the retrieval process. The basic unit used in our technique is a single-colored cluster, which bounds a homogeneous region of that color in an image. Two clusters from two images are similar if they are of the same color and overlap in the image space. The number of clusters that can be extracted from an image can be very large, and it affects the accuracy of retrieval. We study the effect of the number of clusters on retrieval effectiveness to determine an appropriate value for ¡°optimal'' performance. To facilitate efficient retrieval, we also propose a multi-tier indexing mechanism called the Sequenced Multi-Attribute Tree (SMAT)."
"With the growing pervasiveness of Internet and e-commerce today, online search has been at the very heart of consumer information seeking and economic decision making process. However, due to the size and format of information that is approachable by a search engine, as well as the heterogeneous nature of humans, it becomes very hard to identify what information is used and how exactly it is used by a consumer via search engines to facilitate the decision making activities in an online market. In my dissertation, I plan to look into such issues from three perspectives:"
"The paper describes the ARANEUS Wel-Base Management System [l, 5, 4, 61, a system developed at Universitb di Roma Tre, which represents a proposal towards the definition of a new kind of data-repository, designed to manage Web data in the database style. We call a WebBase a collection of data of heterogeneous nature, and more specifically: (i) highly structured data, such as the ones typically stored in relational or objectoriented database systems; (G) semistructured data, in the Web style."
"Clustering, in data mining, is useful for discovering groups and identifying interesting distributions in the underlying data. Traditional clustering algorithms either favor clusters with spherical shapes and similar sizes, or are very fragile in the presence of outliers. We propose a new clustering algorithm called CURE that is more robust to outliers, and identifies clusters having non-spherical shapes and wide variances in size. CURE achieves this by representing each cluster by a certain fixed number of points that are generated by selecting well scattered points from the cluster and then shrinking them toward the center of the cluster by a specified fraction. Having more than one representative point per cluster allows CURE to adjust well to the geometry of non-spherical shapes and the shrinking helps to dampen the effects of outliers."
"Selecting views to materialize is one of the most important decisions in designing a data warehouse. In this paper, we present a framework for analyzing the issues in selecting views to materialize so as to achieve the best combination of good query performance and low view maintenance. We first develop a heuristic algorithm which can provide a feasible solution based on individual optimal query plans. We also map the ma"
"herefore, an accurate classifier is an essential component of a hypertext database. Hyperlinks pose new problems not addressed in the extensive text classification literature. Links clearly contain high-quality semantic clues that are lost upon a purely term-based classifier, but exploiting link information is non-trivial because it is noisy. Naive use of terms in the link neighborhood of a document can even degrade accuracy. Our contribution is to propose robust statistical models and a relaxation labeling technique for better classification by exploiting link information in a small neighborhood around documents. Our technique also adapts gracefully to the fraction of neighboring documents having known topics."
"We consider data to be semistructured when there is no schema fixed or known in advance and when the data may be incomplete or irregular. For example, HTML files on the World-Wide Web usually contain some structure, but often the data is irregular or In addition, data integrated from multiple, heterogeneous information sources often is semistructured. Storing and querying semistructured data poses considerably different problems and requirements than those for traditional databases, where data storage and query processing are dependent upon structured data. Relational, nested-relational, and object-oriented database systems, for example, all depend upon the data having a known and regular schema."
"The VQBD project addresses the following problem: What is the best way to explore an XML document of unknown structure and content? We focus on XML documents that are too large to browse in their entirety, even with the assistance of pretty-printing software (e.g., multi-megabyte or larger XML documents). In this context, we use the term data exploration to refer to the process by which a user gathers the information needed to use the data for a speci c purpose (e.g., generating a report, writing queries, building user interfaces, writing applications). In a relational or object database, the schema (e.g., table de nitions, class de nitions, integrity constraints, and stored procedures) provides some of the information necessary for writing queries and applications. However, the schema is rarely su cient for these tasks. Typically, one must probe and browse the database to discover data coverage, typical and exceptional values, and other information required to gain a better understanding of the database. In an XML environment, the need for such data exploration is much greater because it is quite likely that the XML data of interest is not accompanied by a schema."
"The Grid is an emerging platform to support on-demand ""virtual organisations"" for coordinated resource sharing and problem solving on a global scale. The application thrust is large-scale scientific endeavour, and the scale and complexity of scientific data presents challenges for databases. The Grid is beginning to exploit technologies developed for Web Services and to realise its potential it also stands to benefit from Semantic Web technologies; conversely, the Grid and its scientific users provide application pull which will benefit the Semantic Web."
"This chapter reveals that to date grid middleware has focused principally on the basic issues of storage, computation, and resource management needed to make a global scientific community's information and tools accessible. However, from an e-Science viewpoint, the purpose of the grid is to deliver a collaborative and supportive environment that allows geographically distributed scientists to achieve research goals more effectively. Such an environment is likely to hide many aspects of a grid middleware, and to exploit both generic and application-specific service discovery, invocation, and composition."
"The goal of the i3(eye cube) project is to enhance multidimensional database products with a suite of advanced operators to automate data analysis tasks that are currently handled through manual exploration. Most OLAP products are rather simplistic and rely heavily on the user's intuition to manually drive the discovery process. Such ad hoc user-driven exploration gets tedious and error-prone as data dimensionality and size increases. We first investigated how and why analysts currently explore the data cube and then automated them using advanced operators that can be invoked interactively like existing simple operators. Our proposed suite of extensions appear in the form of a toolkit attached with a OLAP product. At this demo we will present three such operators: DIFF, RELAX and INFORM with illustrations from real-life datasets."
"Many interesting examples in view maintenance involve semijoin and outerjoin queries. In this paper we develop algebraic change propagation algorithms for the following operators: semijoin, anti-semijoin, left outerjoin, right outerjoin, and full outerjoin."
"When authoring multimedia scenarios, and in particular scenarios with user interaction, where the sequence and time of occurrence of interactions is not predefined, it is difficult to guarantee the consistency of the resulting scenarios. As a consequence, the execution of the scenario may result in unexpected behavior or inconsistent use of media. The present paper proposes a methodology for checking the temporal integrity of interactive multimedia document (IMD) scenarios at authoring time at various levels. The IMD flow is mainly defined by the events occurring during the IMD session. Integrity checking consists of a set of discrete steps, during which we transform the scenario into temporal constraint networks representing the constraints linking the different possible events in the scenario."
"We propose a novel index structure, termed XTrie, that supports the efficient filtering of XML documents based on XPath expressions. Our XTrie index structure offers several novel features that make it especially attractive for large scale publish/subscribe systems. First, XTrie is designed to support effective filtering based on complex XPath expressions (as opposed to simple, single-path specifications). Second, our XTrie structure and algorithms are designed to support both ordered and unordered matching of XML data. Third, by indexing on sequences of element names organized in a trie structure and using a sophisticated matching algorithm, XTrie is able to both reduce the number of unnecessary index probes as well as avoid redundant matchings, thereby providing extremely efficient filtering."
"The World Wide Web is rapidly emerging as an important medium for transacting commerce as well as for the dissemination of information related to a wide range of topics (e.g., business, government, recreation). According to most predictions, the majority of human information will be available on the Web in ten years. These huge amounts of data raise a grand challenge for the database community, namely, how to turn the Web into a more useful information utility. This is exactly the subject that will be addressed by this panel."
"This paper reports on experience obtained during the design, implementation and use of a multi-paradigm query interface to an object-oriented database. The specific system which has been developed allows equivalent data retrieval tasks to be expressed using textual, form-based and graph-based notations, and supports automatic translation of queries between these three paradigms. The motivation behind the development of such an interface is presented, as is the software architecture which supports the multi-paradigm functionality."
"We present an efficient implementation method for temporal integrity constraints formulated in Past Temporal Logic. Although the constraints can refer to past states of the database, their checking does not require that the entire database history be stored. Instead, every database state is extended with auxiliary relations that contain the historical information necessary for checking constraints. Auxiliary relations can be implemented as materialized relational views."
"Nearest neighbor search in high dimensional spaces is an interesting and important problem which is relevant for a wide variety of novel database applications. As recent results show, however, the problem is a very di cult one, not only with regards to the performance issue but also to the quality issue. In this paper, we discuss the quality issue and identify a new generalized notion of nearest neighbor search as the relevant problem in high dimensional space. In contrast to previous approaches, our new notion of nearest neighbor search does not treat all dimensions equally but uses a quality criterion to select relevant dimensions (projections) with respect to the given query."
"DTL's DataSpot is an advanced, programming-free tool that lets Web designers and database developers automatically publish their databases for Web browser access. DataSpot enables non-technical end users to explore a database using free-form plain language queries combined with hypertext navigation, in a fashion similar to using search engines such as Alta Vista to search text files on the Internet."
"To overcome these problems we have invented five novel network views that generalize the traditional displays. Two of the views show the complete network, while the other three concentrate on a portion of a larger network defined by connectivity to a given node. Our new visual metaphors retain many of the well-known advantages of the traditional network maps, while exploiting three-dimensional graphics to address some of the fundamental problems limiting the scalability of two-dimensional displays."
"This dynamic, data-centered approach opens up opportunities for personalizations: each user can be mapped to an individual hypertextual view of the Web site (called site view), and business rules may be used to change site views, both statically and dynamically. We argue that personalization of Web access (also called oneto-one Web delivery) is naturally supported by the proposed data-driven approach, and is We acknowledge the support of ESPRIT Project 28771 W3I3, MURST Project Interdata, CNR-CESTIA, and the HP Internet Philanthropic Initiative."
"Star queries are the most prevalent kind of queries in data warehousing, OLAP and business intelligence applications. Thus, there is an imperative need for efficiently processing star queries. To this end, a new class of fact table organizations has emerged that exploits path-based surrogate keys in order to hierarchically cluster the fact table data of a star schema [DRSN98, MRB99, KS01]. In the context of these new organizations, star query processing changes radically. In this paper, we present a complete abstract processing plan that captures all the necessary steps in evaluating such queries over hierarchically clustered fact tables. Furthermore, we present optimizations for surrogate key processing and a novel early grouping transformation for grouping on the dimension hierarchies."
"Digital content is for copying: quotation, revision, plagiarism, and file sharing all create copies. Document fingerprinting is concerned with accurately identifying copying, including small partial copies, within large sets of documents.We introduce the class of local document fingerprinting algorithms, which seems to capture an essential property of any finger-printing technique guaranteed to detect copies. We prove a novel lower bound on the performance of any local algorithm. We also develop winnowing, an efficient local fingerprinting algorithm, and show that winnowing's performance is within 33% of the lower bound. Finally, we also give experimental results on Web data, and report experience with MOSS, a widely-used plagiarism detection service."
"The relational model of data incorporates fundamental assertions for entity integrity and referential integrity. Recently, these so-called relational invariants were more precisely specified by the new SQL2 standard. Accordingly, they have to be guaranteed by a relational DBMS to its users and, therefore, all issues of semantics and implementation became very important. The specification of referential integrity embodies quite a number of complications including the MATCH clause and a collection of referential actions."
"Multimedia databases usually deal with huge amounts of data and it is necessary to have an indexing structure such that efficient retrieval of data can be provided. R-Tree with its variations, is a commonly cited indexing method. In this paper we propose an improved nearest neighbor search algorithm on the R-tree and its variants. The improvement lies in the removal of two hueristics that have been used in previous R*-tree work, which we prove cannot improve on the pruning power during a search."
"EOS employs the multigranularity two version two phase locking protocol, that allows many readers and one writer to access the same item simultaneously. The option to switch to simple 2PL is also available. EOS uses a write-ahead redo-only logging scheme that offers short logs, fast recovery from system failures, and non-blocking checkpoints. Also, configuration files are provided that can be edited by users to customize and tune EOS performance. Finally, the EOS architecture has been designed to be extensible. Users may define hook functions to be executed when certain primitive events occur. This allows controlled access to a number of entry points in the system without compromising modularity."
"We develop a precise syntax and semantics of SchemaSQL in a manner that extends traditional SQL syntax and semantics, and demonstrate the following. (1) SchemaSQL retains the flavour of SQL while supporting querying of both data and meta-data. (2) It can be used to represent data in a database in a structure substantially different from original database, in which data and meta-data may be interchanged. (3) It also permits the creation of views whose schema is dynamically dependent on the contents of the input instance. (4) While aggregation in SQL is restricted to values occurring in one column at a time, SchemaSQL permits ¡°horizontal¡± aggregation and even aggregation over more general ¡°blocks¡± of information. (5) SchemaSQL provides a great facility for interoperability and data/meta-data management in relational multi-database systems. We provide many examples to illustrate our claims."
"A data-integration system provides access to a multitude of data sources through a single mediated schema. A key bottleneck in building such systems has been the laborious manual construction of semantic mappings between the source schemas and the mediated schema. We describe LSD, a system that employs and extends current machine-learning techniques to semi-automatically find such mappings."
"In this paper, we study how to find such optimal schedules. In particular, we consider two optimization criteria: (i) one based on maximizing the number of piggybacked clips, and (ii) the other based on maximizing the impact on buffer space. We show that the optimal schedule under the first criterion is equivalent to a maximum matching in a suitably defined bipartite graph, and that under the second criterion, the optimal schedule is equivalent to a maximum matching in a suitably defined weighted bipartite graph."
In this paper we discuss the benefits of workflow automation and we show why workflow is a key technology for building the foundation for ebusiness. We will demonstrate these concepts by presenting an example of a very successful ebusiness startup that has placed HP Changengine at the core of its e-business platform.
"The discussions during the panel stayed largely but not entirely focused on the question of active database research issues from the application perspective. There were nine panelists. Each panelist was asked to prepare brief answers to a set of questions. The sets of answers were discussed by all participants, and finally a number of more general issues were discussed."
"It is a clich?e that the Internet has revolutionized many aspects of life in the past decade. Scientific publishing is but one of the many enterprises that have been impacted by the connectivity and high bandwidth afforded by the World Wide Web. Most scientific journals now have a web presence. That said, it is still remarkable the degree to which ACM in general andTODSin particular have embraced the unique capabilities of the web to aid in the propagation of knowledge. Here I summarize the disparate and broad ways in which TODSutilizes the web, in all phases of publishing."
"Structural queries constitute a special form of content-based retrieval where the user specifies a set of spatial constraints among query variables and asks for all configurations of actual objects that (totally or partially) match these constraints. Processing such queries can be thought of as a general form of spatial joins, i.e., instead of pairs, the result consists of n-tuples of objects, where n is the number of query variables. In this paper we describe a flexible framework which permits the representation of configurations in different resolution levels and supports the automatic derivation of similarity measures. We subsequently propose three algorithms for structural query processing which integrate constraint satisfaction with spatial indexing (R-trees). For each algorithm we apply several optimization techniques and experimentally evaluate performance using real data."
"A central development in the database area concerns tools that allow non expert users to understand and easily extract information from a database. Fourth generation query languages, although non-procedural, are not friendly enough for a casual user who must know both the logical structure of the database and the syntax and semantics of the DBMS query language. Instead, recently proposed visual systems which allow a user to extract information by means of interactive graphical commands, have not yet been able to combine ease of use and high expressive power."
"Currently parallel object-relational database technology is setting the direction for the future of data management. A central enhancement of objectrelational database technology is the possibility to execute arbitrary user-defined functions within SQL statements. We show the limits of this approach and propose user-defined table operators as a new concept that allows the definition and implementation of arbitrary user-defined N-ary database operators, which can be programmed using SQL or Embedded SQL (with some extensions). Our approach leads to a new dimension of extensibility that allows to push more application code into the server with full support for efficient execution and parallel processing. Furthermore it allows performance enhancements of orders of magnitude for the evaluation of many queries with complex user-defined functions as we show for two concrete examples. Finally, our implementation perception guarantees that this approach fits well into the architectures of commercial object-relational database management systems."
Model-driven engineering technologies offer a promising approach to address the inability of third-generation languages to alleviate the complexity of platforms and express domain concepts effectively.
"We consider the problem of efficiently producing ranked results for keyword search queries over hyperlinked XML documents. Evaluating keyword search queries over hierarchical XML documents, as opposed to (conceptually) flat HTML documents, introduces many new challenges. First, XML keyword search queries do not always return entire documents, but can return deeply nested XML elements that contain the desired keywords. Second, the nested structure of XML implies that the notion of ranking is no longer at the granularity of a document, but at the granularity of an XML element. Finally, the notion of keyword proximity is more complex in the hierarchical XML data model. In this paper, we present the XRANK system that is designed to handle these novel features of XML keyword search. Our experimental results show that XRANK offers both space and performance benefits when compared with existing approaches."
"The chair of ACRP¡¯s Association Board of Trustees recounts how he left manufacturing and research and development a decade ago to take a position as a clinical research administrator. It was a move that place him into a role he knew little about, having not been engaged in clinical research beforehand. If this sounds like a familiar experience to others, the lessons shared in this column highlight the importance of the individual¡¯s ongoing will to learn, and of organizational support for that learning."
"When dealing with semistructured data such as that available on the Web, it becomes important to infer the inherent structure, both for the user (e.g., to facilitate querying) and for the system (e.g., to optimize access). In this paper, we consider the problem of identifying some underlying structure in large collections of semistructured data. Since we expect the data to be fairly irregular, this structure consists of an approximate classification of objects into a hierarchical collection of types. We propose a notion of a type hierarchy for such data, and outline a method for deriving the type hierarchy, and rules for assigning types to data elements."
"Data cube is the core operator in data warehousing and OLAP. Its efficient computation, maintenance, and utilization for query answering and advanced analysis have been the subjects of numerous studies. However, for many applications, the huge size of the data cube limits its applicability as a means for semantic exploration by the user."
"We report the performance of NOW-Sort, a collection of sorting implementations on a Network of Workstations (NOW). We find that parallel sorting on a NOW is competitive to sorting on the large-scale SMPs that have traditionally held the performance records. On a 64-node cluster, we sort 6.0 GB in just under one minute, while a 32-node cluster finishes the Datamation benchmark in 2.41 seconds. Our implementations can be applied to a variety of disk, memory, and processor configurations; we highlight salient issues for tuning each component of the system."
"Data analytics technologies and techniques are widely used in commercial industries to enable organizations to make more-informed business decisions and by scientists and researchers to verify or disprove scientific models, theories and hypotheses. Depending on the specific application, the information may be historical records or new data that has been processed in real-time or it may be the result of a mix data channels. To this end, this book provides an in-depth report of data-enabled methods for analyzing Intelligent Transportation Systems (ITS), including detailed coverage of the tools needed to implement these methods, using big data analytics and other computing techniques."
"In order to find a static type system that adequately supports database languages, we need to express the most general type of a program that involves database operations. This can be achieved through an extension to the type system of ML that captures the polymorphic nation of field selection, together with a techniques that generalizes relational operators to arbitrary data structures. The combination provides a statically typed language in which generalized relational databases may be cleanly represented as typed structures. As in ML types are inferred, which relieves the programmer of making the type assertions that may be required in a complex database environment. These extensions may also be used to provide static polymorphic typechecking in object-oriented languages and databases."
"This paper presents an approach to the development of a practical deductive objectoriented database (DOOD) system baaed upon the integration of a logic query language with an imperative programming language in the context of an object-oriented data model. The approach is novel, in that a formally defined data model has been used as the starting point for the development of the two languages. This has enabled a seamless integration of the two languages, which is the central theme of this paper. It is shown how the two languages have been developed from the underlying data model, and several alterna, tive approaches to their integration are presented, one of which has been chosen for implementation."
"We study indexing techniques for main memory, including hash indexes, binary search trees, T-trees, B+-trees, interpolation search, and binary search on arrays. In a decision-support context, our primary concerns are the lookup time, and the space occupied by the index structure. Our goal is to provide faster lookup times than binary search by paying attention to reference locality and cache behavior, without using substantial extra space. We propose a new indexing technique called Cache-Sensitive Search Trees (CSS-trees)."
"Traditional statistical methods deal with corroborating given hypotheses on a given body of data. However, generating the hypothesis itself is a matter of intuition and ingenuity. It is clearly impossible to test all hypotheses on a database with millions of records and hundreds of elds. There have been attempts to bridge this gap through data mining. Association generation is a method of creating such statistical hypotheses for binary data. For quantitative databases the situation is still not good. There are a number of known methods. One is a reduction to binary data by creating intervals and then generating associations."
"In the DBCache project, we are incorporating a database cache feature in DB2 UDB by modifying the engine code and leveraging existing federated database functionality. This allows us to take advantage of DB2's sophisticated distributed query processing power for database caching. As a result, the user queries can be executed at either the local database cache or the remote backend server, or more importantly, the query can be partitioned and then distributed to both databases for cost optimum execution.DBCache also includes a cache initialization component that takes a backend database schema and SQL queries in the workload, and generates a middle-tier database schema for the cache."
"In this paper, we present and thoroughly evaluate a new class of query optimization algorithms that are based on a principle that we call iterative dynamic programming, or IDP for short. IDP has several important advantages: First, IDP-algorithms produce the best plans of all known algorithms in situations in which dynamic programming is not viable because of its high complexity. Second, some IDP variants are adaptive and produce as good plans as dynamic programming if dynamic programming is viable and as good-as possible plans if dynamic programming turns out to be not viable. Three, all IDP-algorithms can very easily be integrated into an existing optimizer which is based on dynamic programming."
"In this paper we present a solution to the problem of concurrent operations in R-trees, a dynamic access structure capable of storing multidimensional and spatial data. We describe the R-link tree, a variant of the R-tree that adds sibling pointers to nodes, a technique first deployed in B-link tree, a variant of the R-tree that adds sibling pointers to nodes, a technique first deployed in B-link trees, to compensate for concurrent structure modifications. The main obstacle to the use of sibling pointers is the lack of linear ordering among the keys in an R-tree; we overcome this by assigning sequence numbers to nodes that let us reconstruct the ""lineage"" of a node at any point in time."
"As we embark on the information age the use of electronic information is spreading through all sectors of society, both nationally and internationally. As a result, commercial organizations, educational institutions and government agencies are finding it essential to be linked by world wide networks, and commercial Internet usage is growing at an accelerating pace."
"Providing content-based video query, retrieval and browsing is the most important goal of a video database management system (VDBMS). Video data is unique not only in terms of its spatial and temporal characteristics, but also in the semantic associations manifested by the entities present in the video. This paper introduces a novel video data model called Logical Hypervideo Data Model. In addition to multilevel video abstractions, the model is capable of representing video entities that users are interested in (defined as hot objects) and their semantic associations with other logical video abstractions, including hot objects themselves."
"This paper describes the architecture of OPERA, a generic platform for building distributed systems over stand alone applications. The main contribution of this research effort. is t,o propose a ¡°kernel¡± system providing the ¡°essentials¡± for distributed processing and to show the important role database technology may play in supporting such functionality. These include a powerful process management environment. created as a generalization of workflow ideas and incorporating transactional notions such as spheres of isolation, atomicit.y, and persistence and a transactional engine enforcing correctness based on the nested and multi-level models. It also includes a tool-kit providing externalized database functionality enabling physical database design over heterogeneous data repositories."
"In this paper we study how to refresh a local copy of an autonomous data source to maintain the copy up-to-date. As the size of the data grows, it becomes more difficult to maintain the copy \ fresh, ¡°making it crucial to synchronize the copy effectively. We define two freshness metrics, change models of the underlying data, and synchronization policies. We analytically study how effective the various policies are. We also experimentally verify our analysis, based on data collected from 270 web sites for more than 4 months, and we show that our new policy improves the \ freshness¡± very significantly compared to current policies in use."
"The transaction concept in computing goes back to the early days of computerized data processing. It has developed and evolved over the years both in terms of formal theory and practical application. This evolutionary process has been driven in large part by applications that require transactionlike properties. Newly emerging applications include several that involve people in a time-dependent role. The new forms of human involvement in transaction processing required by these applications are generating new systemslevel challenges. Likewise, these needs present challenges and opportunities from a theoretical standpoint. This talk reviews the history of synergy between theory and practice in the area of transaction processing, and considers currently emerging needs from that perspective."
A weighted sample is used to preserve the densities of the original data. Density biased sampling naturally includes uniform sampling as a special case. A memory efficient algorithm is proposed that approximates density biased sampling using only a single scan of the data. We empirically evaluate density biased sampling using synthetic data sets that exhibit varying cluster size distributions finding up to a factor of six improvement over uniform sampling.
"The TSQL2 language, which was created to Temporal Databases, has a limited concept of indeterminate information [14]. So, both formalisms and temporal query languages present partial solutions to representing and manipulating indeterminate temporal objects. The main objective of this paper is to show a formalism that gives definitions about representation and manipulation of indeterminate temporal objects in indeterminate temporal database (ITDB). More precisely, we herein introduce LITO (Logic of Indeterminate Temporal Objects), a formalism that allows for retrieval query, logical query, insertion, logical deletion, refinement and update of indeterminate temporal objects."
"In this paper, we focus on the retrieval of a set of interesting answers called the skyline from a database. Given a set of points, the skyline comprises the points that are not dominated by other points. A point dominates another point if it is as good or better in all dimensions and better in at least one dimension. We present two novel algorithms, Bitmap and Index, to compute the skyline of a set of points. Unlike most existing algorithms that require at least one pass over the dataset to return the rst interesting point, our algorithms progressively return interesting points as they are identi ed. Our performance study further shows that the proposed algorithms provide quick initial response time with Index being superior in most cases."
"The Multimedia Description Standard MPEG-7 is an International Standard since February 2002. It defines a huge set of description classes for multimedia content, for its creation and its communication. This article investigates what MPEG-7 means to Multimedia Database Systems (MMDBSs) and vice versa. We argue that MPEG-7 has to be considered complementary to, rather than competing with, data models employed in MMDBSs. Finally we show by an example scenario how these technologies can reasonably complement one another."
"New generation of e-commerce applications require data schemas that are constantly evolving and sparsely populated. The conventional horizontal row representation fails to meet these requirements. We represent objects in a vertical format storing an object as a set of tuples. Each tuple consists of an object identifier and attribute name-value pair. Schema evolution is now easy. However, writing queries against this format becomes cumbersome. We create a logical horizontal view of the vertical representation and transform queries on this view to the vertical table. We present alternative implementations and performance results that show the effectiveness of the vertical representation for sparse data. We also identify additional facilities needed in database systems to support these applications well."
"In this paper we present DynaMat, a system that dynamically materializes information at multiple levels of granularity in order to match the demand (workload) but also takes into account the maintenance restrictions for the warehouse, such as down time to update the views and space availability. DynaMat unifies the view selection and the view maintenance problems under a single framework using a novel ¡°goodness¡± measure for the materialized views. DynaMat constantly monitors incoming queries and materializes the best set of views subject to the space constraints. During updates, DynaMat reconciles the current materialized view selection and refreshes the most beneficial subset of it within a given maintenance window."
"We present a new algorithm for dynamically computing quantiles of a relation subject to insert as well as delete operations. The algorithm monitors the operations and maintains a simple, small-space representation (based on random subset sums or RSSs) of the underlying data distribution. Using these RSSs, we can quickly estimate, without having to access the data, all the quantiles, each guaranteed to be accurate to within user-specified precision. Previously-known one-pass quantile estimation algorithms that provide similar quality and performance guarantees can not handle deletions. Other algorithms that can handle delete operations cannot guarantee performance without rescanning the entire database."
"This short paper is a gentle introduction to the theory, focusing on the results most relevant for database theory. Interested readers are referred to Downey and Fellow¡¯s monograph [6] to learn more about parameterized complexity theory. The paper is organised as follows: In Section 2 we describe two simple fixed-parameter tractable algorithms in an informal way. Section 3 presents the formal framework of parameterized complexity theory. Section 4 is a brief survey of the parameterized complexity of database query evaluation."
"Almost all practicing scientists see the peer review process from two perspectives: that of the reviewer and that of the reviewee. My own views on these two aspects of scienti? c publishing have evolved signi? cantly in the eighteen years that I have been writing scienti? c papers. My introduction to the review process from the author¡¯s point of view was memorable and unpleasant. My research advisor received the reviews for a paper that I had written and passed them directly to me with instructions to prepare responses to the reviewers¡¯ criticisms. The longer of the two reviews was biting and sarcastic. I responded in kind and returned the responses to my advisor, thinking that he would ? lter them before returning them to the editor."
"This paper provides a formal, high-level operational semantics for a complex-value OQL-like query language that can create fresh database objects, and invoke external methods. We define a type system for our query language and prove an important soundness property.We define a simple effect typing discipline to delimit the computational effects within our queries. We prove that this effect system is correct and show how it can be used to detect cases of non-determinism and to define correct query optimizations."
"METU Object-Oriented DBMS1 includes the implementation of a database kernel, an object-oriented SQL-like language and a graphical user interface. Kernel functions are divided between a SQL Interpreter and a C++ compiler. Thus the interpretation of functions are avoided increasing the efficiency of the system. The compiled by C++ functions are used by the system through the Function Manager. The system is realized on Exodus Storage Manager (ESM), thus exploiting some of the kernel functions readily provided by ESM. The additional functions provided by the MOOD kernel are the optimization and interpretation of SQL statements, dynamic linking of functions, and catalog management."
"Persistent Application Systems (PASs) are of increasing social and economic importance. They have the potential to be long-lived, concurrently accessed, and consist of large bodies of data and programs. Typical examples of PASs are CAD/CAM systems, office automation, CASE tools, software engineering environments, and patient-care support systems in hospitals. Orthogonally persistent object systems are intended to provide improved support for the design, construction, maintenance, and operation of PASs. Persistence abstraction allows the creation and manipulation of data in a manner, that is independent of its lifetime, thereby integrating the database view of information with the programming language view. This yields a number of advantages in terms of orthogonal design and programmer productivity which are beneficial for PASs."
"Our GC uses a new synchronization mechanism (mechanism that allows the GC to operate concurrently with ordinary users of the database), called CC-consistent cuts. A GC-consistent cut is a set of virtual copies of database pages. The copies are taken at times such that an object may appear as garbage in the cut only if it is garbage in the system. Our GC examines the copies, instead of the real database, in order to determine which objects are garbage. More sophisticated GCs can execute concurrently with the applications."
"This tutorial deals with the construction of data-centric Web applications, focusing on the modelling of processes and on the integration with Web services. The tutorial describes the standards, methods, and tools that are commonly used for building these applications."
"The children of today grow up having information and communication technologies (ICTs) as essential and natural parts of their daily life. As they grow, they are expected to become active and self-directed members in their own local communities and also in the information society at large. Technology creates versatile possibilities for the acquisition and creation of information, for self-expression, and for communication and interaction with other people locally, nationally, and worldwide."
"DTL¡¯s DataSpot is a database publishing tool that enables non-technical end users to explore a database using free-form plain language queries combined with hypertext navigation. DataSpot is based on a novel representation of data in the form of a schema-less semi-structured graph called a hyperbase. The DataSpot Publisher takes one or more possibly heterogeneous databases, predefined knowledge banks such as a thesaurus, and userdefined associations, and creates the hyperbase. The DataSpot Search Server performs searches and navigation against the hyperbase, returning answers to the user either in HTML pages or through an object API. The DataSpot product has been successfilly deployed in diverse application areas including electronic catalogs, yellow pages, classified ads, help desks and finance."
"From this fortunate position we can concentrate on disseminating good science quickly and ef? ciently. To do that, however, we need the continued support of good reviewers. The next time one of those big brown envelopes shows up in your mail box, take a few minutes to think of what is being asked of you, not only from the perspective of an overworked professional who just got one more task to do, but also from the perspectives of the authors and editor who are depending on your expertise to see that the best interests of science are served. The authors and I will thank you."
"Our success in deploying the illusion of infinite stomge to applications rests in the use of database tebhnology. Tht3 paper presents the support for transactions in the ADSTAR Dhtributed Stomge Manager, (A DSiU) system. For a user, ADSM offers a backup and archive service in a heterogeneous cliint-server environment. It also operates as a file migratton mposito~ in some Unix environments. As a stomge manager, the ADSM server is a Mass Stomge System (MSS) that administers stomge hiemrchies of arbitrary depth in which all activities are done on behatf of transactions. Its systems goals include to epemte in many computing phz#omts, to pmvidG h@lyavaihtble metadata, to administer effective& a huge amount,of entities, to support continuous and unattended opemtion, and-to support a high degree of concutrent requests."
"This paper proposes a dynamic buffer allocation scheme that allocates to user requests buffers of the minimum size in a partially loaded state as well as in the fully loaded state. The inherent difficulty in determining the buffer size in the dynamic buffer allocation scheme is that the size of the buffer currently being allocated is dependent on the number of and the sizes of the buffers to be allocated in the next service period. We solve this problem by the predict-and-enforce strategy, where we predict the number and the sizes of future buffers based on inertia assumptions and enforce these assumptions at runtime. Any violation of these assumptions is resolved by deferring service to the violating new user request until the assumptions are satisfied. Since the size of the current buffer is dependent on the sizes of the future buffers, the size is represented by a recurrence equation. We provide a solution to this equation, which can be computed at the system initialization time for runtime efficiency."
"Finding all the occurrences of a twig pattern specified by a selection predicate on multiple elements in an XML document is a core operation for efficient evaluation of XML queries. Holistic twig join algorithms were proposed recently as an optimal solution when the twig pattern only involves ancestor-descendant relationships. In this paper, we address the problem of efficient processing of holistic twig joins on all/partly indexed XML documents. In particular, we propose an algorithm that utilizes available indices on element sets. While it can be shown analytically that the proposed algorithm is as efficient as the existing state-of-the-art algorithms in terms of worst case I/O and CPU cost, experimental results on various datasets indicate that the proposed index-based algorithm performs significantly better than the existing ones, especially when binary structural joins in the twig pattern have varying join selectivities."
"We consider the problem of answering queries from databases that may be incomplete. A database is incomplete if some tuples may be missing from some relations, and only a part of each relation is known to be complete. This problem arises in several contexts. For example, systems that provide access to multiple heterogeneous information sources often encounter incomplete sources. The question we address is to determine whether the answer to a specific given query is complete even when the database is incomplete. We present a novel sound and complete algorithm for the answer-completeness problem by relating it to the problem of independence of queries from updates. We also show an important case of the independence problem (and therefore ofthe answer-completeness problem) that can be decided in polynomial time, whereas the best known algorithm for this case is exponential."
"In this paper, we propose a monitoring service that could be offered by such database servers, and present algorithms for its implementation. In contrast to published view maintenance algorithms, we do not assume that the server has access to the original materialization when computing differential view changes to be notified. We also do not assume any database capabilities on the client side and therefore compute precisely the required differentials rather than just an approximation, as is done by cache coherence techniques in homogeneous clientserver databases."
"The problems of discussing Geographic Information Systems GIS, for short begin with defining this term. There are countless definitions for GIS, each based on the type of user and application domain. The more general definition would be ¡°a digital information system whose records are somehow geographically referenced¡±. For more precise definitions, one may emphasize their functional capabilities (e.g., that GIS capture and process spatial data) or the applications supported (linking the definition to the type of problem solved). Others stress the fact that GIS are ultimately tools to be used for decision support. Last but not least, a GIS is database-dependent (¡°a database system that supports management of spatial data¡±). In the database community, GIS are primarily associated with spatial databases, and therefore a large amount of the research effort in databases for GIS is related to spatial structures and access methods."
"We consider the problem of query optimization in the presence of limitations on access patterns to the data (i.e., when one must provide values for one of the attributes of a relation in order to obtain tuples). We show that in the presence of limited access patterns we must search a space of annotated query plans, where the annotations describe the inputs that must be given to the plan. We describe a theoretical and experimental analysis of the resulting search space and a novel query optimization algorithm that is designed to perform well under the different conditions that may arise. The algorithm searches the set of annotated query plans, pruning invalid and non-viable plans as early as possible in the search space, and it also uses a best-first search strategy in order to produce a first complete plan early in the search. We describe experiments to illustrate the performance of our algorithm."
"In this paper, we examine the issue of mining association rules among items in a large database of sales transactions. The mining of association rules can be mapped into the problem of discovering large itemsets where a large itemset is a group of items which appear in a sufficient number of transactions. The problem of discovering large itemsets can be solved by constructing a candidate set of itemsets first and then, identifying, within this candidate set, those itemsets that meet the large itemset requirement. Generally this is done iteratively for each large k-itemset in increasing order of k where a large k-itemset is a large itemset with k items. To determine large itemsets from a huge number of candidate large itemsets in early iterations is usually the dominating factor for the overall data mining performance. To address this issue, we propose an effective hash-based algorithm for the candidate set generation."
"This paper proposes a dependability benchmark for OLTP systems. This dependability benchmark uses the workload of the TPC-C performance benchmark and specifies the measures and all the steps required to evaluate both the performance and key dependability features of OLTP systems, with emphasis on availability. This dependability benchmark is presented through a concrete example of benchmarking the performance and dependability of several different transactional systems configurations. The effort required to run the dependability benchmark is also discussed in detail."
"We describe a ¡°full speed¡± backup, only loosely coupled to the cache manager, and hence similar to current online backups, but effective for general logical log operations. This requires additional logging of cached objects to guarantee media recoverability. We then show how logging can be greatly reduced when log operations have a constrained form which nonetheless provides very useful additional logging efficiency for database systems."
"Great efforts have been paid in the Intelligent Database Systems Research Lab for the research and development of efficient data mining methods and construction of on-line analytical data mining systems.Our work has been focused on the integration of data mining and OLAP technologies and the development of scalable, integrated, and multiple data mining functions. A data mining system, DBMiner, has been developed for interactive mining of multiple-level knowledge in large relational databases and data warehouses. The system implements a wide spectrum of data mining functions, including characterization, comparison, association, classification, prediction, and clustering."
"Since multimedia retrieval is based on similarity calculations of semantics and media-based search, exact matches are not expected. We view querying multimedia database as a combination of IR, image matching, and traditional database query processing and it should be conducted in a way of perpetual query reformulation for honing target results. In this paper we present a hybrid multimedia database system, which employs a hierarchical database statistics structure for both query optimization and reformulation analysis without adding additional query processing cost."
We describe the design and implementation of the Glue-Nail deductive database system. Nail is a purely declarative query language; Glue is a procedural language used for non-query activities. The two languages combined are sufficient to write a complete application. Nail and Glue code are both compiled into the target language IGlue. The Nail compiler uses variants of the magic sets algorithm and supports well-founded models. The Glue compiler's static optimizer uses peephole techniques and data flow analysis to improve code.
"n this paper we propose a new ""transcurrent execution model"" (TEM) for concurrent user queries against tree indexes. Our model exploits intra-parallelism of the index scan and dynamically decomposes each query into a set of disjoint ""query patches"". TEM integrates the ideas of prefetching and shared scans in a new framework, suitable for dynamic multi-user environments. It supports time constraints in the scheduling of these patches and introduces the notion of data flow for achieving a steady progress of all queries."
"The use of asynchronous video interviews (AVIs) and artificial intelligence (AI)-based decision agents enables more efficient employment screening compared with traditional synchronous video interviews (SVIs). However, the social impacts of using synchrony and AI decision agents in video interviews have not been investigated. Drawing on media richness theory and social interface theory, this study employed a novel experimental design to compare human ratings and job applicants' response behaviours between the SVI and AVI settings and compare job applicants¡¯ fairness perception between the AVI setting and the AVI setting using an AI decision agent (AVI-AI)."
"At the University of Illinois at Urbana-Champaign, the computer engineering curriculum is offered by the large, research-oriented Department of Electrical and Computer Engineering. The curriculum features a strong foundation in electrical engineering, an appropriate balance of computer hardware and software topics, a sequence of increasingly sophisticated design experiences, and a wide variety of electives."
"We describe the open, extensible architecture of SQL for accessing data stored in external data sources not managed by the SQL engine. In this scenario, SQL engines act as middleware servers providing access to external data using SQL DML statements and joining external data with SQL tables in heterogeneous queries. We describe the state-of-the art in object-relational systems and their companion products, and provide an outlook on future directions."
"The annual series of the British National Conference on Databases has been a forum for UK database practitioners and a focus for database research since 1981. In recent years, interest in this conference series has extended well beyond the UK.BNCOD 2001, the 18th conference in the series, was held at the CLRC Rutherford Appleton Laboratory (RAL) from 9th -11th July 2001. RAL hosts national large-scale facilities for advanced scientific research."
"This dissertation describes techniques for speeding up Online Analytical Processing or OLAP queries. OLAP systems allow users to quickly obtain the answers to complex business queries. Quickly answering these queries which aggregate large amounts of data, calls for various specialized techniques. One technique used by OLAP systems to speed up multidimensional data analysis is to precompute aggregates on some subsets of dimensions and their corresponding hierarchies."
"In this paper, we propose HMAP (The term is the transliteration of an ancient Greek poetical word meaning ¡°day¡±.), a temporal data model extending the capability of defining valid times with different granularity and/or with indeterminacy. In HMAP, absolute intervals are explicitly represented by their start,end, and duration: in this way, we can represent valid times as ¡°in December 1998 for five hours¡±, ¡°from July 1995, for 15 days¡±, ¡°from March 1997 to October 15, 1997, between 6 and 6:30 p.m.¡±. HMAP is based on a three-valued logic, for managing uncertainty in temporal relationships. Formulas involving different temporal relationships between intervals, instants, and durations can be defined, allowing one to query the database with different granularities, not necessarily related to that of data."
"We propose a generic approach to parallelization, called TOPAZ. Different forms of parallelism are exploited to obtain maximum speedup combined with lowest resource consumption. The necessary abstractions w.r.t. operator characteristics and system architecture are provided by rules that are used by a cost-based, top-down search engine. A multi-phase pruning based on a global analysis of the plan efficiently guides the search process, thus considerably reducing complexity and achieving optimization performance."
"With the huge development of internet, the information retrieval became tough and unreliable. Users interest and need is differs at every time. In order to improve the searching experience, several personalized search techniques are proposed. Using the information about the user, their history and query behavior the results will be reproduced. This kind of query reproduction is known as personalized search technique. Nowadays the information on the server is in a semi structured way. XML (eXtended Markup Language) search helps to improve the retrieval effectiveness in the semi structured data. The system proposed a novel personalized search in the XML framework. The system contributes a highly effective XML based personalized technique."
"Database support for data mining has become an important research topic. Especially for large high-dimensional data volumes, comprehensive support from the database side is necessary. In this paper we identify the data intensive subproblem of aggregating high-dimensional data in all possible low-dimensional projections (for instance estimating low-dimensional histograms), which occurs in several established data mining techniques. Second, we show that existing OLAP SQL-extensions are insufficient for high-dimensional data and propose a new SQL-operator, which seamlessly fits into the set of existing OLAP Group By operators."
"The Semantic Web is a vision the idea of having data on the Web defined and linked in such a way that it can be used by machines not just for display purposes but for automation, integration and reuse of data across various applications. Technically, however, there is a widespread misconception that the Semantic Web is primarily a rehash of existing AI and database work focused on encoding knowledge representation formalisms in markup languages such as RDF(S), DAML+OIL or OWL. Kashyap, Bussler, and Moran seek to dispel this notion by presenting the broad dimensions of this emerging Semantic Web and the multi-disciplinary technological underpinnings like machine learning, information retrieval, service-oriented architectures, and grid computing, thus combining the informational and computational aspects needed to realize the full potential of the Semantic Web vision."
"We believe that the support of video on mobile systems will indeed make possible many new interesting applications. However, providing mobile video is a non-trivial task, and much work needs to be done before practical systems are widely available. In this short note we address the issue of mobile multimedia from a practitioner's perspective. We note what software and hardware are currently available in the market in support of mobile multimedia, and point out some of their deficiencies. We also discuss some of the communication and data management research issues that need to be tackled in order to address said deficiencies. Exploring these research issues is the focus of our project."
"Scheduling query execution plans is a particularly complex problem in hierarchical parallel systems, where each site consists of a collection of local time-shared (e.g., CPU(s) or disk(s)) and space-shared (e.g., memory) resources and communicates with remote sites by messagepassing. We develop a general approach to the problem, capturing the full complexity of scheduling distributed multi-dimensional resource units for all kinds of parallelism within and across queries and operators. We present heuristic algorithms for various forms of the problem, some of which are provably near-optimal. Preliminary experimental results confirm the effectiveness of our approach."
"We present a generic solution to a problem which lies at the heart of the unpredictable worst-case performance characteristics of a wide class of multi-dimensional index designs: those which employ a recursive partitioning of the data space. We then show how this solution can produce modified designs with fully predictable and controllable worst-case characteristics. In particular, we show how the recursive partitioning of an n-dimensional dataspace can be represented in such a way that the characteristics of the one-dimensional B-tree are preserved in n dimensions, as far as is topologically possible i.e. a representation guaranteeing logarithmic access and update time, while also guaranteeing a one-third minimum occupancy of both data and index nodes."
"The commoditization of high-performance networking has sparked research interest in the RDMA capability of this hardware. One-sided RDMA primitives, in particular, have generated substantial excitement due to the ability to directly access remote memory from within an application without involving the TCP/IP stack or the remote CPU. This article considers how to leverage RDMA to improve the analytical performance of parallel database systems. To shuffle data efficiently using RDMA, one needs to consider a complex design space"
"Many real-time database applications arise in electronic financial services, safety-critical installations and military systems where enforcing security is crucial to the success of the enterprise. We investigate here the performance implications, in terms of killed transactions, of guaranteeing multi-level secrecy in a real-time database system supporting applications with firm deadlines. In particular, we focus on the buffer management aspects of this issue.Our main contributions are the following. First, we identify the importance and difficulties of providing secure buffer management in the real-time database environment. Second, we present SABRE, a novel buffer management algorithm that provides covert-channel-free security. SABRE employs a fully dynamic one-copy allocation policy for efficient usage of buffer resources."
"A workflow history manager maintains the information essential for workflow monitoring and data mining as well as for recovery and authorization purposes.Certain characteristics of workflow systems like the necessity to run these systems on heterogeneous, autonomous and distributed environments and the nature of data, prevent history management in workflows to be handled by the classical data management techniques like distributed DBMSs. We further demonstrate that multi-database query processing techniques are also not appropriate for the problem at hand.In this paper, we describe history management, i.e., the structure of the history and querying of the history, in a fully distributed workflow architecture realized in conformance with Object Management Architecture (OMA) of OMG."
"This paper proposes the use of repetitive broadcast as a way of augmenting the memory hierarchy of clients in an asymmetric communication environment. We describe a new technique called ""Broadcast Disks"" for structuring the broadcast in a way that provides improved performance for non-uniformly accessed data. The Broadcast Disk superimposes multiple disks spinning at different speeds on a single broadcast channel--in effect creating an arbitrarily fine-grained memory hierarchy. In addition to proposing and defining the mechanism, a main result of this work is that exploiting the potential of the broadcast structure requires a re-evaluation of basic cache management policies."
"The chapter proposes computation of the Hamming norm as a basic operation of interest. The Hamming norm formalizes ideas that are used throughout data processing. When applied to a single stream, the Hamming norm gives the number of distinct items that are present in that data stream, which is a statistic of great interest in databases. When applied to a pair of streams, the Hamming norm gives an important measure of (dis)similarity: the number of unequal item counts in the two streams. Hamming norms have many uses in comparing data streams. For many applications that produce data streams, it is useful to visualize the underlying data seen so far or underlying state of the system as a very high dimensional vector."
"We propose a novel index structure, A-tree (Approximation tree), for similarity search of high-dimensional data. The basic idea of the A-tree is the introduction of Virtual Bounding Rectangles (VBRs), which contain and approximate MBRs and data objects. VBRs can be represented rather compactly, and thus affect the tree configuration both quantitatively and qualitatively. Firstly, since tree nodes can install large number of entries of VBRs, fanout of nodes becomes large, thus leads to fast search. More importantly, we have a free hand in arranging MBRs and VBRs in tree nodes. In the A-trees, nodes contain entries of an MBR and its children VBRs."
"The paper proposes two extended R -trees that permit the indexing of data regions that grow continuously over time, by also letting the internal bounding regions grow. Internal bounding regions may be triangular as well as rectangular. New heuristics for the algorithms that govern the index structure are provided. As a result, dead space and overlap, now also functions of time, are reduced. Performance studies indicate that the best extended index is typically 3©\5 times faster than the existing R-tree based indices."
"Joins are among the most frequently executed operations. Several fast join algorithms have been developed and extensively studied; these can be categorized as sort-merge, hash-based, and index-based algorithms. While all three types of algorithms exhibit excellent performance over most data, ameliorating the performance degradation in the presence of skew has been investigated only for hash-based algorithms. However, for sort-merge join, even a small amount of skew present in realistic data can result in a significant performance hit on a commercial DBMS. This paper examines the negative ramifications of skew in sort-merge join and proposes several refinements that deal effectively with data skew."
"In this paper we present an efficient method to do online rebuild of a B+-tree index. This method has been implemented in Sybase Adaptive Server Enterprise (ASE) Version 12.0. It provides high concurrency, does minimal amount of logging, has good performance and does not deadlock with other index operations. It copies the index rows to newly allocated pages in the key order so that good space utilization and clustering are achieved. The old pages are deallocated during the process. Our algorithm differs from the previously published online index rebuild algorithms in two ways. It rebuilds multiple leaf pages and then propagates the changes to higher levels. Also, while propagating the leaf level changes to higher levels, level 11 pages are reorganized, eliminating the need for a separate pass."
"Several organizations have developed very large market basket databases for the maintenance of customer transactions. New applications, e.g., Web recommendation systems, present the requirement for processing similarity queries in market basket databases. In this paper, we propose a novel scheme for similarity search queries in basket data. We develop a new representation method, which, in contrast to existing approaches, is proven to provide correct results. New algorithms are proposed for the processing of similarity queries. Extensive experimental results, for a variety of factors, illustrate the superiority of the proposed scheme over the state-of-the-art method."
"XML is widely regarded as a promising means for data representation integration, and exchange. As companies transact business over the Internet, the sensitive nature of the information mandates that access must be provided selectively, using sophisticated access control specifications. Using the specification directly to determine if a user has access to a specific XML data item can hence be extremely inefficient. The alternative of fully materializing, for each data item, the users authorized to access it can be space-inefficient. In this paper, we propose a space- and time-efficient solution to the access control problem for XML data. Our solution is based on a novel notion of a compressed accessibility map (CAM), which compactly identifies the XML data items to which a user has access, by exploiting structural locality of accessibility in tree-structured data."
"Synthetic collections of XML documents can be useful in many applications, such as benchmarking (e.g., Xmark, XOO7) and algorithm testing and evaluation. We present ToXgene, a template-based tool for facilitating the generation of large, consistent collections of synthetic XML documents. ToXgene was designed with the following requirements in mind: it should be declarative, to speed the data generation up; it should be general enough to generate fairly complex XML content and it should be powerful enough to capture the most common kinds of constraints in popular benchmarks. Preliminary experimental results show that our tool can closely reproduce the data sets for the Xmark and the TPC-H benchmarks. The ToXgene Template Specification Language (TSL) is a subset of the XML Schema notation augmented with annotations for specifying certain properties of the intended data, such as probability distributions, the vocabulary for CDATA content, etc."
"Data cube computation is one of the most essential but expensive operations in data warehousing. The latter, represented by two algorithms: BUC and H-Cubing, computes the iceberg cube bottom-up and facilitates Apriori pruning. BUC explores fast sorting and partitioning techniques; whereas H-Cubing explores a data structure, H-Tree, for shared computation. However, none of them fully explores multi-dimensional simultaneous aggregation."
"Prior studies have documented how deindustrialization poses a bleak outlook for both individuals and their communities: longterm unemployment, elevated poverty, and the erosion of once vital areas. What can people do to mitigate the effects of declining industries that once employed several generations of workers? More importantly, how can collective action help transform society into realizing diverse interests, rather than just a few, narrowly defined interests? Jeremy Brecher¡¯s Banded Together: Economic Democratization in the Brass Valley shares a much-needed account of how such efforts unfold in Western Connecticut¡¯s Naugatuck Valley, a community known for its brass manufacturing since the 1800s."
"Here is an old joke: what is black and white and red all over? A newspaper. Why though? As we assume that nothing could really be black and white and red all over, we infer that ¡®red¡¯ should be heard as ¡®read.¡¯ In the grand philosophical tradition of making even humour unfunny, I want to take issue with this assumption. My thesis is that it is possible to see two objects in black and white, while at the same time seeing one of them as redder than the other. More generally, I argue that it is possible to perceptually represent colour relations between two objects, without perceptually representing their colours. I call this primitive relational colour representation (PRCR). This goes against the orthodox view that we represent colour relations by virtue of representing colours. This orthodoxy has been challenged by several authors in the recent literature, and I here add my name to the chorus."
"In this article, we explore new correctness criteria and scheduling methods that capture temporal transaction dependencies and belong to, the broad area between these two extreme approaches. We introduce the concepts ofsuccession dependency andchronological dependency and define correctness criteria under which temporal dependencies between transactions are preserved even if the dependent transactions execute concurrently. We also propose achronological scheduler that can guarantee that transaction executions satisfy their chronological constraints."
"This paper presents an approach to object view management for relational databases. Such a view mechanism makes it possible for users to transparently work with data in a relational database as if it was stored in an object-oriented (OO) database. A query against the object view is translated to one or several queries against the relational database. The results of these queries are then processed to form an answer to the initial query. The approach is not restricted to a ¡®pure¡¯ object view mechanism for the relational data, since the object view can also store its own data and methods. Therefore it must be possible to process queries that combine local data residing in the object view with data retrieved from the relational database."
"In this work, we study the problem of semantic caching of Web queries and develop a caching mechanism for conjunctive Web queries based on signature files. Our algorithms cope with both relations of semantic containment and intersection between a query and the corresponding cache items. We also develop the cache replacement strategy to treat situations when cached items differ in size and contribution when providing partial query answers. We report results of experiments and show how the caching mechanism is realized in the Knowledge Broker system."
"This paper proposes an extensible framework for capturing and querying meta-data properties in a semistructured data model. Properties such as temporal aspects of data, prices associated with data access, quality ratings associated with the data, and access restrictions on the data are considered. Specifically, the paper defines an extensible data model and an accompanying query language that provides new facilities for matching, slicing, collapsing, and coalescing properties. It also briefly introduces an implemented, SQLlike query language for the extended data model that includes additional constructs for the effective querying of graphs with properties."
In this paper we investigate the problem of incremental maintenance of materialized views in data warehouses. We consider views defined by relational algebraic operators and aggregate functions. We show that a materialized view can be maintained without accessing the view itself by materializing and maintaining additional relations. These relations are derived from the intermediate results of the view computation. We first give an algorithm for determining what additional relations need to be materialized in order to maintain a materialized view incrementally.
"The rapidly evolving managed healthcare industry requires efficient coordination of human and automated tasks as well as information-flow across multiple enterprises. One of the most critical applications in managed care is state-wide immunization tracking, which if supported by appropriate workflow technology can achieve substantial near term impact. In this paper, we discuss a comprehensive and real-world application to support child immunization tracking for the state of Connecticut in close collaboration with CHREFl. The application system uses UGA-LSDIS¡¯s2 multi-paradigm transactional workflow management system METEOR:!. It utilizes the World Wide Web either exclusively, or in conjunction with CORBA-based infrastructures."
"Query optimization generates plans to retrieve data requested by queries. Query rewriting, which is the first step of this process, rewrites a query expression into an equivalent form to prepare it for plan generation. COKO-KOLA introduced a new approach to query rewriting that enables query rewrites to be formally verified using an automated theorem prover. KOLA is a language for expressing term rewriting rules that can be ""fired"" on query expressions. COKO is a language for expressing query rewriting transformations that are too complex to express with simple KOLA rules. COKO is a programming language designed for query optimizer development. Programming languages require debuggers, and in this demonstration, we illustrate our COKO debugger: Visual COKO. Visual COKO enables a query optimization developer to visually trace the execution of a COKO transformation. At every step of the transformation, the developer can view a tree-display that illustrates how the original query expression has evolved."
"The Oracle RDBMS recently introduced an innovative compression technique for reducing the size of relational tables. By using a compression algorithm specifically designed for relational data, Oracle is able to compress data much more effectively than standard compression techniques. More significantly, unlike other compression techniques, Oracle incurs virtually no performance penalty for SQL queries accessing compressed tables. In fact, Oracle's compression may provide performance gains for queries accessing large amounts of data, as well as for certain data management operations like backup and recovery. Oracle's compression algorithm is particularly well-suited for data warehouses: environments, which contains large volumes of historical data, with heavy query workloads."
"We have built a multidatabase system to support a financial application that stores historical data used by traders to identify trends in the market. The application has an update rate (append-only) of 500 inserts per second and also has sub-second response requirements for queries. A typical query requests between 100-1000 records. In this paper we define the characteristics of the application, the multidatabase system we used to support the applications and the extensions we made in t.he application to achieve the required functionality and performance."
"Warehouse views need to be updated when source data changes. Due to the constantly increasing size of warehouses and the rapid rates of change, there is increasing pressure to reduce the time taken for updating the warehouse views. In this paper we focus on reducing this ¡°update window¡± by minimizing the work required to compute and install a batch of updates. Various strategies have been proposed in the literature for updating a single warehouse view. These algorithms typically cannot be extended to come up with good strategies for updating an entire set of views. We develop an efficient algorithm that selects an optimal update strategy for any single warehouse view."
"In this paper we present an efficient algorithm for mining association rules that is fundamentally different from known algorithms. Compared to previous algorithms, our algorithm not only reduces the I/O overhead significantly but also has lower CPU overhead for most cases. We have performed extensive experiments and compared the performance of our algorithm with one of the best existing algorithms. It was found that for large databases, the CPU overhead was reduced by as much as a factor of four and I/O was reduced by almost an order of magnitude. Hence this algorithm is especially suitable for very large size databases."
"In this paper, we propose two update propagation strategies that improve freshness. Both of them use immediate propagation: updates to a primary copy are propagated towards a slave node as soon as they are detected at the master node without waiting for the commitment of the update transaction. Our performance study shows that our strategies can improve data freshness by up to five times compared with the deferred approach."
"This paper is a retrospective of the Stanford Information Filtering Service (SIFT), a system that as of April 1996 was processing over 40,000 worldwide subscriptions and over 80,000 daily documents. The paper describes some of the indexing mechanisms that were developed for SIFT, as well as the evaluations that were conducted to select a scheme to implement. It also describes the implementation of SIFT, and experimental results for the actual system. Finally, it also discusses and experimentally evaluates techniques for distributing a service such as SIFT for added performance and availability."
"As our dependency on hlformation systems grows, the threat of having those disrupted by cyber attacks becomes a very pressing reality. We have witnesses nmltiple occurrences of attacks in the recent past that have seriously disrupted businesses and organizations. And, unfortunately, this trend is only increasing. For some time now, some research groups have been doing research oil data mining techniques that can potentially help in meeting the challenges posed by the attacks. This special issue is an attempt to bring some of these people together and disseminate some of the results among the SIGMOD audience, and perhaps spark the interest of the community for this emerging field. In this issue we have six papers."
"Knowledge based applications require linguistic, terminological and ontological resources. These applications are used to fulfill a set of tasks such as semantic indexing, knowledge extraction from text, information retrieval, etc. Using these resources and combining them for the same application is a tedious task with different levels of complexity. This requires their representation in a common language, extracting the required knowledge and designing effective large scale storage structures offering operators for resources management. For instance, ontology repositories were created to address these issues by collecting heterogeneous ontologies. They generally offer a more effective indexing of these resources than general search engines by generating alignments and annotations to ensure their interoperability."
"Query optimization is a computationally intensive process, especially for the complex queries that are typical in current data warehousing and mining applications. The inherent overheads of query optimization are compounded by the fact that a new query is typically optimized afresh, providing no opportunity to amortize these overheads over prior optimizations. While current commercial query optimizers do provide facilities for reusing execution plans generated for earlier queries (e.g. ""stored outlines"" in Oracle 9i), the query matching is extremely restrictive-only if the incoming query has a close textual resemblance with one of the stored queries is the associated plan re-used to execute the new query."
"In this paper, we introduce Probabilistic Wavelet Synopses, the first wavelet-based data reduction technique with guarantees on the accuracy of individual approximate answers. Whereas earlier approaches rely on deterministic thresholding for selecting a set of ""good"" wavelet coefficients, our technique is based on a novel, probabilistic thresholding scheme that assigns each coefficient a probability of being retained based on its importance to the reconstruction of individual data values, and then flips coins to select the synopsis. We show how our scheme avoids the above pitfalls of deterministic thresholding, providing highly-accurate answers for individual data values in a data vector."
"We first consider a cost model that counts the number of subgoals in a physical plan, and show a search space that is guaranteed to include an optimal rewriting, if the query has a rewriting in terms of the views. We also develop an efficient algorithm for finding rewritings with the minimum number of subgoals. We then consider a cost model that counts the sizes of intermediate relations of a physical plan, without dropping any attributes, and give a search space for finding optimal rewritings. Our final cost model allows attributes to be dropped in intermediate relations. We show that, by careful variable renaming, it is possible to do better than the standard ¡°supplementary relation¡± approach, by dropping attributes that the latter approach would retain."
"Recently, a technique called quotient cube was proposed as a summary structure for a data cube that preserves its semantics, with applications for online exploration and visualization. The authors showed that a quotient cube can be constructed very efficiently and it leads to a significant reduction in the cube size. While it is an interesting proposal, that paper leaves many issues unaddressed. Firstly, a direct representation of a quotient cube is not as compact as possible and thus still wastes space. Secondly, while a quotient cube can in principle be used for answering queries, no specific algorithms were given in the paper. Thirdly, maintaining any summary structure incrementally against updates is an important task, a topic not addressed there. In this paper, we propose an efficient data structure called QC-tree and an efficient algorithm for directly constructing it from a base table, solving the first problem."
"Bioinformatics, the discipline concerned with biological information management is essential in the post-genome era, where the complexity of data processing allows for contemporaneous multi level research including that at the genome level, transcriptome level, proteome level, the metabolome level, and the integration of these -omic studies towards gaining an understanding of biology at the systems level. This research is also having a major impact on disease research and drug discovery, particularly through pharmacogenomics studies."
"Information Dissemination applications are gaining increasing popularity due to dramatic improvements in communications bandwidth and ubiquity. The sheer volume of data available necessitates the use of selective approaches to dissemination in order to avoid overwhelming users with unnecessaryinformation. Existing mechanisms for selective dissemination typically rely on simple keyword matching or ¡°bag of words¡± information retrieval techniques. The advent of XML as a standard for information exchangeand the development of query languages for XML data enables the development of more sophisticated filtering mechanisms that take structure information into account. We have developed several index organizations and search algorithms for performing efficient filtering of XML documents for large-scale information dissemination systems. In this paper we describe these techniques and examine their performance across a range of document, workload, and scale scenarios."
"Databases are replicated to improve performance and availability. The notion of correctness that has commonly been adopted for concurrent access by transactions to shared, possibly replicated, data is serializability. However, serializability may be impractical in high-performance applications since it imposes too stringent a restriction on concurrency. When serializability is relaxed, the integrity constraints describing the data may be violated. By allowing bounded violations of the integrity constraints, however, we are able to increase the concurrency of transactions that execute in a replicated environment. In this article, we introduce the notion of an N-ignorant transaction, which is a transaction that may be ignorant of the results of at most N prior transactions, which is a transaction that may be ignorant of the results of at most N prior transactions."
"insects. Can. Dep. Agric., Sci. Serv., Entomol. Div., Publ. No. 932. DANKS. H. V. (Editor). 1979. Canada and its insect fauna. Mem. Entomol. Soc. Can. 108. FAIN, A., N. J. KOK, F. S. LUKOSCHUS, and F. W. CLULOW. 197 1. Notes on the hypopial nymphs phoretic on mammals in Canada with description of a new species (Acarina: Sarcoptiformes). Can. J. Zool. 49: 1518. GLENNY, F. H. 1951. Occurrence of two species of fleas on Peromyscus maniculatus gracilis (LeConte) in western Quebec. Can. Field Nat. 65: 210. GREGSON, J. D. 1956. The Ixodoidea of Canada. Can. Dep. Agric., Sci. Serv., Entomol. Div., Publ. No. 930. HILTON, D. F. J. 1970. A technique for collecting ectoparasites from small birds and mammals. Can. J. Zool. 48: 1445-1446. HOLLAND, G. P. 1949."
"In addition to research on the chemical properties of natural aroma compounds (NACs) that cause the perception of flavour and aroma, several studies have reported their potential applications for human health due to their antioxidant, anti-inflammatory, anti-cancer and anti-obesity properties. Furthermore, consumer demand shows a tendency towards natural products; most research in the industry and academic fields has focused on the bio-generation of commercially relevant NACs, particularly microbial production via de novo synthesis or biotransformation using enzymes or whole cells in conventional aqueous media."
"Here we survey the compactness and geometric stability conjectures formulated by the participants at the 2018 IAS Emerging Topics Workshop on Scalar Curvature and Convergence. We have tried to survey all the progress towards these conjectures as well as related examples, although it is impossible to cover everything. We focus primarily on sequences of compact Riemannian manifolds with nonnegative scalar curvature and their limit spaces."
"This paper describes the new architecture for supporting the Teradata commercial VLDB on several new operating environments. We start with an overview of the Teradata database software architecture, specifically the Parallel Database Extensions (PDE) that serve as a layer between the NCR Unix OS and the database software. We then describe the challenges of implementing an Open PDE for several new platforms, (Microsoft Windows 2000, Linux, HP-UX, and Microsoft Windows XP)."
"In this paper, we present an efficient algorithm called FastXMiner, to discover frequent XML query patterns. We develop theorems to prove that only a small subset of the generated candidate patterns needs to undergo expensive tree containment tests. In addition, we demonstrate how the frequent query patterns can be used to improve caching performance. Experiments results show that FastXMiner is efficient and scalable, and caching the results of frequent patterns significantly improves the query response time."
"We abstract a GUI application as a set of event handlers. Each event handler can be conceptualized as a transition from the old screen/program state to a new screen/program state. We use a data centric view of the screen/program state (i.e., every entity on the screen corresponds to proxy datum in the program) and express each event handler as a query dependent update, albeit a complicated one. To express such complicated updates we use Logic++. The proxy data are expressed as derived views that are materialized on the screen. Therefore, the system must be active in maintaining these materialized views. Consequently, each event handler is conceptually an update followed by a fixpoint computation of the proxy data."
"The XEWA-00 workshop, held in December 2000 and sponsored by the IEEE Computer Society, was organized to bring together members of the bioinformatics community to determine if XML could simplify accessing large, heterogeneous, distributed collections of web-based data sources. The starting point for a series of breakout and group discussions was a proposed strawman of a grammar that described how to query a data source through its web interface. As a result of these discussions, the approach was validated, the strawman was refined, and several reference implementations are being generated as part of an ongoing effort. This article contains an overview of the workshop, including the proposed approach and a description of the strawman."
"Recovery Oriented Computing (ROC) is a joint research effort between Stanford University and the University of California, Berkeley. ROC takes the perspective that hardware faults, software bugs, and operator errors are facts to be coped with, not problems to be solved. This perspective is supported both by historical evidence and by recent studies on the main sources of outages in production systems. By concentrating on reducing Mean Time to Repair (MTTR) rather than increasing Mean Time to Failure (MTTF), ROC reduces recovery time and thus offers higher availability. We describe the principles and philosophy behind the joint Stanford/Berkeley ROC effort and outline some of its research areas and current projects."
"In this paper a robust technique is proposed to incorporate non-relevant information to efficiently discover the feasible search region. A decision surface is determined to split the attribute space into relevant and nonrelevant regions. The decision surface is composed of hyperplanes, each of which is normal to the minimum distance vector from a nonrelevant point to the convex hull of the relevant points. A similarity metric, estimated using the relevant objects is used to rank and retrieve database objects in the relevant region. Experiments on simulated and benchmark datasets demonstrate robustness and superior performance of the proposed technique over existing adaptive similarity search techniques."
"There are high expectations in all sectors of society for immediate access to biological knowledge of all kinds. To fully exploit and manage the value of biological resources, society must have the intellectual tools to store, retrieve, collate, analyze, and synthesize organism-level and ecological scale information. However, it currently is difficult to discover, access, and use biodiversity data because of the long history of ¡°bottom-up¡± evolution of scientific biodiversity information, the mismatch between the distribution of biodiversity itself and the distribution of the data about it, and, most importantly, the inherent complexity of biodiversity and ecological data. This stems from, among many factors, numerous data types, the nonexistence of a common underlying (binary) language, and the multiple perceptions of different researchers/data recorders across spatial or temporal distance or both."
"This is the seventh bibliography concerning temporal databases. In this bibliography, we collect 331 new temporal databases papers. Most of these papers were published in 1996-1997, some in 1995 and some will appear in 1997 or 1998."
"The language Java is enjoying a rapid rise in popularity as an application programming language. For many applications an effective provision of database facilities is required. Here we report on a particular approach to providing such facilities, called ¡°orthogonal persistence¡±. Persistence allows data to have lifetimes that vary from transient to (the best approximation we can achieve to) indefinite. It is orthogonal persistence if the available lifetimes are the same for all kinds of data. We aim to show that the programmer productivity gains and possible performance gains make orthogonal persistence a valuable augmentation of Java."
"The computation of multi-dimension cube in data warehouse is of much importance.Dwarf is a highly compressed structure for computing,storing data cubes which can be materialized completely.During the constructing process,each closed node is stored in disk,while the computing of unit ALL needs access the closed nodes in the disk frequently."
"We have been developing a mobile passenger guide system for public transports. Passengers can make their travel plans and purchase necessary electronic tickets using mobile terminals via Internet. During the travel, the mobile terminal, which also works as an electronic ticket, compares the stored travel plan with the passenger's actual activities and offers appropriate guide messages. To execute this task, the mobile terminal collects various kinds of information about the travel fields (routes, fares, area maps, station maps, operation schedule, timetables, facilities of stations and vehicles etc.) using multi-channel data communications. The mobile terminal contains a personal database for the passenger by selecting and integrating necessary data according to the user's situation and characteristics."
"We consider an optimization technique for deductive and relational databases. The optimization technique is an extension of the magic templates rewriting, and it can improve the performance of query evaluation by not materializing the extension of intermediate views. Standard relational techniques, such as unfolding embedded view definitions, do not apply to recursively defined views, and so alternative techniques are necessary. We demonstrate the correctness of our rewriting. We define a class of ¡°nonrepeating¡± view definitions, and show that for certain queries our rewriting performs at least as well as magic templates on nonrepeating views, and often much better. A syntactically recognizable property, called ¡°weak right-linearity¡±, is proposed."
"In this paper we propose a distributed case-based approach to the problem of rewriting queries. According to this approach we use a case memory instead of static views, i.e. views that are deened a priori. As a consequence, the mediated schema is dynamically updated, strongly innuenced by the queries submitted by a consumer. This approach allows a mediator to face systems where consumers may change their customization needs and information sources may become unavailable, may be added, or may modify their schemas."
"In this article, we will discuss the effects of applying traditional transaction management techniques to multi-tier architectures in distributed environments. We will show the performance costs associated with distributed transactions and discuss ways by which enterprises really manage their distributed data to circumvent this performance hit. Our intent is to share our experience as an industrial customer with the database research and vendor community to create more usable and scalable designs."
This paper gives an overview of the IRO-DB architecture and describes in detail the cost evaluator currently under elaboration for the next version of the distributed query optimizer. The cost model is composed of a set of mathematical formulas with coefficients to estimate the cost of the search operators. The coefficients are deduced from a calibrating objectoriented database composed of linked collections of objects. A tuning application is run on each local site to adjust the cost formulas and fix the coefficients. We report on the tuning of O2 and ObjectStore. We show that the estimation is quite accurate for path traversals with the OO7 benchmark on top of ObjectStore.
"There is currently considerable interest in developing multimedia digital libraries. However, it has become clear that existing architectures for management systems do not support the particular requirements of continuous media types. This is particularly the case in the important area of quality of service support. In this correspondence, we discuss quality of service issues within digital libraries and present a reference architecture able to support some quality aspects."
"The exponential growth of resources on the web, and the wide deployment of devices for multimodal access to the Internet, lead to new problems in information management. In this context, and as part of the European project Vision, we have built an interactive telematic handbook of the culture and the territory of Sardinia. A team of cultural experts browsed the web to get a large collection of Internet resources.The system built for the management of this data uses emerging Internet technologies such as the XML language suite and its applications."
"In large data warehousing environments, it is often advantageous to provide fast, approximate answers to complex aggregate queries based on statistical summaries of the full data. In this paper, we demonstrate the difficulty of providing good approximate answers for join-queries using only statistics (in particular, samples) from the base relations. We propose join synopses as an effective solution for this problem and show how precomputing just one join synopsis for each relation suffices to significantly improve the quality of approximate answers for arbitrary queries with foreign key joins. We present optimal strategies for allocating the available space among the various join synopses when the query work load is known and identify heuristics for the common case when the work load is not known."
"We describe the architecture of a hypertext resource discovery system using a relational database. Such a system can answer questions that combine page contents, metadata, and hyperlink structure in powerful ways, such as ¡°find the number of links from an environmental protection page to a page about oil and natural gas over the last year.¡± A key problem in populating the database in such a system is to discover web resources related to the topics involved in such queries. We argue that that a keywordbased ¡°find similar¡± search based on a giant all-purpose crawler is neither necessary nor adequate for resource discovery. Instead we exploit the properties that pages tend to cite pages with related topics, and given that a page u cites a page about a desired topic, it is very likely that u cites additional desirable pages."
"This paper abstracts from the underlying platforms and instead considers the requirements to CRM solutions for the various communication channels, in order to devise a uniform and corporate-wide data architecture for an omni-channel customer view to maximize the business clients' value in customer retention and customer centric analytics. Especially, online customer segmentation integrating channel usage and preferences is presented as a very promising means for constructing a self-energising information loop which will lead to highly improved customer service along the whole customer journey."
"In the last few months, we have spent the majority of this column reviewing the meaning of the word ""standard"", updating you on the status of the longawaited third-generation of the SQL standard (formerly known as SQL3 and now known as SQL: 1999), and introducing you to two of the three parts of the SQLJ specifications. This month, we're going to look a bit further into the future by surveying some of the new components of the SQL standard that are currently under development. Before we do that, however, one last word on SQL:1999's availability: In March, 1999, we told you (see reference) the titles of the parts of the SQL standard that would be published in 1999 and gave you the addresses of organizations from which you could purchase the documents. Sadly, there was a minor, but possibly important, typographical error in each of the titles, so we correct that error in references through."
"DEVise is a data exploration system that allows users to easily develop, browse, and share visual presentation of large tabular datasets (possibly containing or referencing multimedia objects) from several sources. The DEVise framework is being implemented in a tool that has been already successfully applied to a variety of real applications by a number of user groups."
"To speed up multidimensional data analysis, database systems frequently precompute aggregates on some subsets of dimensions and their corresponding hierarchies. This improves query response time. However, the decision of what and how much to precompute is a difficult one. It is further complicated by the fact that precomputation in the presence of hierarchies can result in an unintuitively large increase in the amount of storage required by the database. Hence, it is interesting and useful to estimate the storage blowup that will result from a proposed set of precomputations without actually computing them. We propose three strategies for this problem: one based on sampling, one based on mathematical approximation, and one based on probabilistic counting. We investigate the accuracy of these algorithms in estimating the blowup for different data distributions and database schemas. The algorithm based upon probabilistic counting is particularly attractive, since it estimates the storage blowup to within provable error bounds while performing only a single scan of the data."
"In this paper we develop BBS (branch-and-bound skyline), a progressive algorithm also based on nearest neighbor search, which is IO optimal, i.e., it performs a single access only to those R-tree nodes that may contain skyline points. Furthermore, it does not retrieve duplicates and its space overhead is significantly smaller than that of NN. Finally, BBS is simple to implement and can be efficiently applied to a variety of alternative skyline queries. An analytical and experimental comparison shows that BBS outperforms NN (usually by orders of magnitude) under all problem instances."
"In this article we illustrate a methodology for introducing and maintaining ontology based knowledge management applications into enterprises with a focus on Knowledge Processes and Knowledge Meta Processes. While the former process circles around the usage of ontologies, the latter process guides their initial set up. We illustrate our methodology by an example from a case study on skills management."
"Our method relies on randomizing techniques that compute small ""sketch"" summaries of the streams that can then be used to provide approximate answers to aggregate queries with provable guarantees on the approximation error. We also demonstrate how existing statistical information on the base data (e.g., histograms) can be used in the proposed framework to improve the quality of the approximation provided by our algorithms. The key idea is to intelligently partition the domain of the underlying attribute(s) and, thus, decompose the sketching problem in a way that provably tightens our guarantees. Results of our experimental study with real-life as well as synthetic data streams indicate that sketches provide significantly more accurate answers compared to histograms for aggregate queries. This is especially true when our domain partitioning methods are employed to further boast the accuracy of the final estimates."
"Web services have become a mainstream developmemt in the industry. Their emergence is based on the mechanisms that made Web Browsing popular: the existence of a pervasive networking infrastructure, the widely deployed availability of communication protocols such as IP, TCP, UDP and HTTP, the standardization of XML documents and their display by browsers, and the emergence of higher level transports such as SOAP. In additiom standard services such as UDDI and description languages such as WSDL established a base on which services could be specified, described, and published. Thus, the begning of the inter Web Service communication was founded."
"Association-rule mining has proved a highly successful technique for extracting useful information from very large databases. This success is attributed not only to the appropriateness of the objectives, but to the fact that a number of new query-optimization ideas, such as the ¡°a-priori¡± trick, make association-rule mining run much faster than might be expected. In this paper we see that the same tricks can be extended to a much more general context, allowing efficient mining of very large databases for many different kinds of patterns. The general idea, called ¡°query flocks,¡± is a generate-and-test model for data-mining problems. We show how the idea can be used either in a general-purpose mining system or in a next generation of conventional query optimizers."
"We present a general technique for efficiently carrying out large sets of simple transformation or querying operations over external-memory data tables. It greatly reduces the number of performed disk accesses and seeks by maximizing the temporal locality of data access and organizing most of the necessary disk accesses into long sequential reads or writes of data that is reused many times while in memory. This technique is based on our experience from building a functionally complete and fully operational web search engine called Yuntis. As such, it is in particular well suited for most data manipulation tasks in a modern web search engine and is employed throughout Yuntis. The key idea of this technique is co-ordinated partitioning of related data tables and corresponding partitioning and delayed batched execution of the transformation and querying operations that work with the data. This data and processing partitioning is naturally compatible with distributed data storage and parallel execution on a cluster of workstations."
"Opening a series of concrete works to follow, this vision paper identifies, motivates, and abstracts the problem of model management. It proposes to support ¡°models¡± and their ¡°mapping¡± as first-class constructs, with high-level algebraic operations to manipulate. In the winter of 2000, I was a starting faculty at UIUC, and this paper inspired me immensely at the time when I had to create a research agenda of my own. I have always been interested in information integration, on various topics like query translation and data mapping. The area was exciting to me, as it was full of ¡°real-world¡± problems. However, it was also not hard to see that these problems seemed inherently messy and their solutions inherently heuristic."
"The system is aimed at these three questions: Is my protein sequence already patented? What are the prior arts? How to broaden my patent claims? The system provides the following information in response to these questions: It can find patented sequences that are similar to yours, it can try to determine the superfamily of your sequence and can find patented sequences that are similar to some sequences in the same superfamily, it can also find sequences that are similar to unpatented members in the same superfamily."
The field of database systems research and development has been enormously successful over its 30 year history. It has led to a $10 billion industry with an installed base that touches virtually every major company in the world. It would be unthinkable to manage the large volume of valuable information that keeps corporations running without support from commercial database management systems (DBMS).
"Developments in high-throughput sequencing (HTS) result in an exponential increase in the amount of data generated by sequencing experiments, an increase in the complexity of bioinformatics analysis reporting and an increase in the types of data generated. These increases in volume, diversity and complexity of the data generated and their analysis expose the necessity of a structured and standardized reporting template. BioCompute Objects (BCOs) provide the requisite support for communication of HTS data analysis that includes support for workflow, as well as data, curation, accessibility and reproducibility of communication. BCOs standardize how researchers report provenance and the established verification and validation protocols used in workflows while also being robust enough to convey content integration or curation in knowledge bases."
"ACTA is a comprehensive transaction framework that facilitates the formal description of properties of extended transaction models. Specifically, using ACTA, one can specify and reason about (1) the effects of transactions on objects and (2) the interactions between transactions. This article presents ACTA as a tool for the synthesis of extended transaction models, one which supports the development and analysis of new extended transaction models in a systematic manner. Here, this is demonstrated by deriving new transaction definitions (1) by modifying the specifications of existing transaction models, (2) by combining the specifications of existing models, and (3) by starting from first principles."
"To address these issues, we developed amdb, a visual AM ¡°debugging¡± tool to support the AM design and implementation process. It is based on the GiST (Generalized Search Tree, [HNP95]) framework for AM construction, which offers the designer an abstracted view of a tree-structured AM and factors out the mechanical aspects of an AM implementation, such as tree traversal, concurrency control and recovery. Amdb is a visual analysis, debugging and profiling tool for AMs that are written as extensions of libgist, a public-domain stand-alone C++ implementation of GiSTs."
"Checkpointing is an important mechanism for limiting crash recovery times. This paper describes a new checkpointing algorithm that was implemented in Oracle 8.0. This algorithm efJiciently JWS buffers which need to be written for checkpointing and easily scales to very large buffer cache sizes: it has been tested with buffer caches as large as six million buffers. Based on this algorithm, we have implemented a new checkpointing mechanism which we refer to as the incremental checkpointing mechanism. Incremental checkpoints are continuous, low overhead checkpoints that wn¡¯te buffers as a background activity. Incremental checkpointing is able to continuously advance the database checkpoint, i.e., the starting position in the redo log for crash recovery, resulting in dramatic improvements in recovery time while imposing minimal overhead during normal processing."
"The Joumal is a quarterly puUication of the VLDB Endowment. As a database systems journal it is dedicated to the intemational publication of scholarly contributions to the advancement of information system architectures, the impact of emerging technologies on information systems, and the development of novel applications. It presents significant advances in the design, implementation, and evaluation of systems for databases and for other information collections Its scope ranges from the development of special-purpose hardware, the design of innovative software approaches, integrated system architectures, the design analysis and performance evaluation of systems to new techniques for presenting and capturing information."
"The idea of building data warehouses as central data collections made available for decision support applications in a company is widely accepted. The concrete design and management of a data warehouse from a technical as well as from an organizational point of view, however, turns out to be far from trivial but requires sophisticated and time consuming efforts. The DMDW workshop was held at the CAiSE¡¯99 conference in Heidelberg on June 14-15, 1999. It had the intention to bring together practitioners and researchers to discuss the design and management of data warehouses. The various presentations gave a broad view on the data warehouse life cycle covering aspects relevant at design time, at build time and at run time."
"Literature on information integration across databases tacitly assumes that the data in each database can be revealed to the other databases. However, there is an increasing need for sharing information across autonomous entities in such a way that no information apart from the answer to the query is revealed. We formalize the notion of minimal information sharing across private databases, and develop protocols for intersection, equijoin, intersection size, and equijoin size. We also show how new applications can be built using the proposed protocols."
"Aggregation and duplicate removal are common in SQL queries. However, in the parallel query processing literature, aggregate processing has received surprisingly little attention; furthermore, for each of the traditional parallel aggregation algorithms, there is a range of grouping selectivities where the algorithm performs poorly. In this work, we propose new algorithms that dynamically adapt, at query evaluation time, in response to observed grouping selectivities. Performance analysis via analytical modeling and an implementation on a workstation-cluster shows that the proposed algorithms are able to perform well for all grouping selectivities. Finally, we study the effect of data skew and show that for certain data sets the proposed algorithms can even outperform the best of traditional approaches."
"With the advent of GIS, multi-media, and warehousing technologies, database systems have started focusing on storage and access of multi-dimensional data such as spatial, OLAP, image, audio, and video attributes. As a step in this direction, Oracle% launched the interMedia product to support spatial and image data, and Materialized Views (MV) to support warehousing applications. Although 2-dimensional spatial data is efficiently indexed using OracleBi Spatial, and highdimensional image data using a combination of bitmap indexing and the Visual Information Retrieval (VIR) product, there is still a need for efficient indexing mechanisms for medium-dimensionality data such as OLAP, and CAD/CAM applications. In this paper, we describe the implementation of a new indextype, called the R-tree, to support medium-dimensionality data (i.e., data whose dimensionality is in the range of 310) using the extensible indexing framework of OracleSi."
"A warehouse is a repository of integrated information drawn from remote data sources. Since a warehouse effectively implements materialized views, we must maintain the views as the data sources are updated. This view maintenance problem differs from the traditional one in that the view definition and the base data are now decoupled. We show that this decoupling can result in anomalies if traditional algorithms are applied. We introduce a new algorithm, ECA (for ""Eager Compensating Algorithm""), that eliminates the anomalies. ECA is based on previous incremental view maintenance algorithms, but extra ""compensating"" queries are used to eliminate anomalies. We also introduce two streamlined versions of ECA for special cases of views and updates, and we present an initial performance study that compares ECA to a view recomputation algorithm in terms of messages transmitted, data transferred, and I/O costs."
"The chair of ACRP¡¯s Association Board of Trustees recounts how he left manufacturing and research and development a decade ago to take a position as a clinical research administrator. It was a move that place him into a role he knew little about, having not been engaged in clinical research beforehand. If this sounds like a familiar experience to others, the lessons shared in this column highlight the importance of the individual¡¯s ongoing will to learn, and of organizational support for that learning."
DISIMA (Distributed Image Database Management System) is a research project under development at the University of Alberta. DISIMA implements a database approach to developing an image database system. Image contents are modeled using objectoriented paradigms while a declarative query language and a corresponding visual query language allow queries over syntactic and semantic features of images. The distributed and interoperable architecture is designed using common facilities as defined in the Object Management Architecture (OMA).
"We present a change-centric method to manage versions in a Web WareHouse of XML data. The starting points is a sequence of snapshots of XML documents we obtain from the web. By running a di algorithm, we compute the changes between two consecutive versions. We then represent the sequence using a novel representation of changes based on completed deltas and persistent identi ers. We present the foundations of the logical representation and some aspects of the physical storage policy. The work presented here was developed in the context of the Xyleme project of massive XML warehouse for XML data from the Web. It has been implemented and tested. We brie y discuss the implementation."
"An infrared generator wherein an ellipsoidal reflector has a source rich in infra red at one focus thereof. The end of the reflector at the other focus merges with a paraboloidal reflector positioned so that the focus of the latter reflector coincides with the said other focus of the former. A second ellipsoidal reflector may be inserted between the former said reflectors with one of its foci coinciding with the said other focus of the former said ellipsoidal reflector, and its other focus coinciding with the focus of the paraboloidal reflector. The axes of the reflectors are coincident, and a lens and plug or equivalent may be provided to recover radiation that might otherwise be lost."
"In this paper we present a tool for enhanced exploration of OLAP data that is adaptive to a user¡¯s prior knowledge of the data. The tool continuously keeps track of the parts of the cube that a user has visited. The information in these scattered visited parts of the cube is pieced together to form a model of the user¡¯s expected values in the unvisited parts. The mathematical foundation for this modeling is provided by the classical Maximum Entropy principle. At any time, the user can query for the most surprising unvisited parts of the cube. The most surprising values are dened as those which if known to the user would bring the new expected values closest to the actual values. This process of updating the user¡¯s context based on visited parts and querying for regions to explore further continues in a loop until the user¡¯s mental model perfectly matches the actual cube."
"Database systems for real-time applications must satisfy timing constraints associated with transactions, while maintaining data consistency. In addition to real-time requirements, security is usually required in many applications. Multilevel security requirements introduce a new dimension to transaction processing in real-time database systems. In this paper, we argue that because of the complexities involved, trade-offs need to be made between security and timeliness. We briefly present the secure two-phase locking protocol and discuss an adaptive method to support trading off security for timeliness, depending on the current state of the system. The performance of the adaptive secure two-phase locking protocol shows improved timeliness. We also discuss future research direction to improve timeliness of secure database systems."
"We have implemented a compressor (XMilI) and decompressor (XDemill) for XML data, to be used in data exchange and archiving, which can be downloaded from http://www.research.att.com/sw/tools/xmill. XMill compresses about twice as good as gzip, at about the same speed. It does not need a DTD in order to compress, and preserves the input XML file faithfully, including element order, attributes order, PI 's, comments, the DTD, etc. A novelty in XMill is that it allows users to combine existing compressors in order to compress heterogeneous XML data: by default it uses zlib , a library function implementing gz ip ' s functionality, and includes some standard compression techniques for simple data types."
"Traditional protocols for distributed database management have high message overhead, lock or restrain access to resources during protocol execution, and may become impractical for some scenarios like real-time systems and very large distributed databases. In this paper we present the demarcation protocol; it overcomes these problems through the use of explicit linear arithmetic consistency constraints as the correctness criteria. The method establishes safe limits as ¡°lines drawn in the sand¡± for updates and gives a way of changing these limits dynamically, enforcing the constraints at all times."
"This paper introduces monitoring applications, which we will show differ substantially from conventional business data processing. The fact that a software system must process and react to continual inputs from many sources (e.g., sensors) rather than from human operators requires one to rethink the fundamental architecture of a DBMS for this application area. In this paper, we present Aurora, a new DBMS that is currently under construction at Brandeis University, Brown University, and M.I.T. We describe the basic system architecture, a stream-oriented set of operators, optimization tactics, and support for real-time operation."
"This paper describes the design and implementation of Paradise, a database system designed for handling GIS type of applications. The current version of Paradise, uses a client-server architecture and provides an extended-relational data model for modeling GIS applications. Paradise supports~an extended version of SQL and provides a graphical user interface for querying and browsing the database. We also describe the results of benchmarking Paradise using the Sequoia 2000 storage benchmark."
"It is today widely accepted that ¡°Business Rules Independence¡± is required for information systems to better and more rapidly adjust to changes in the business environment, This paper¡¯ attempts to articulate how logic based database systems provide adequate technology for better ¡°Business Rules Independence¡±. These systems do so by going beyond ¡°Data Independence¡± and by providing ¡°Knowledge Independence¡±. This paper benefits from the experience gained in developing and marketing the VALIDITY deductive and object-oriented database system during the last few years. Current applications and specific data management techniques to be used are discussed."
This paper describes the use of Object-Database Management Systems (ODBMS)for the storage of High-Energy Physics (HEP) data.
"We address the problem of query rewriting for TSL, a language for querying semistructured data. We develop and present an algorithm that, given a semistructured query q and a set of semistructured views V, finds rewriting queries, i.e., queries that access the views and produce the same result as q. Our algorithm is based on appropriately generalizing ontainment mappings, the chase, and query composition ¡ª techniques that were developed for structured, relational data. We also develop an algorithm for equivalence checking of TSL queries. We show that the algorithm is sound and complete for TSL, i.e., it always finds every non-trivial TSL rewriting query of q, and we discuss its complexity. We extend the rewriting algorithm to use some forms of structural constraints (such as DTDs) and find more opportunities for query rewriting."
"In this paper, we present the theory and algorithms needed to generate alternative evaluation orders for the optimization of queries containing outerjoins. Our results include both a complete set of transformation rules, suitable for new-generation, transformation-based optimizers, and a bottom-up join enumeration algorithm compatible with those used by traditional optimizers."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
"The abstraction approach describes each object in the symbolic image by using a vector consisting of the values of some of its features (e.g., shape, genus, etc.). The approaches differ in the way in which responses to queries are computed. In the classification approach, images are retrieved on the basis of whether or not they contain objects that have the same classification as the objects in the query. On the other hand, in the abstraction approach, retrieval is on the basis of similarity of feature vector values of these objects. Methods of integrating these two approaches into a relational multimedia database management system so that symbolic images can be stored and retrieved based on their content are described. Schema definitions and indices that support query specifications involving spatial as well as contextual constraints are presented. Spatial constraints may be based on both locational information (e.g., distance) and relational information (e.g., north of). Different strategies for image retrieval for a number of typical queries using these approaches are described."
"Therefore, index structures can easily be used in queries. A typical example is a join cursor which consumes the outputs of two underlying cursors. Most of our work is however not dedicated to the area of relational databases, but mainly refers to spatial and temporal data. For spatial databases, for example, we provide several implementations of spatial join algorithms. The cursor-based processing is however the major advantage of XXL in contrast to approaches like LEDA and TPIE. For more information on XXL see http://www.mathematik.uni-marburg.de/DBS/xxl."
"The current state of internal database technology today is a "" One Size Fits All "" approach, Whether the database is being used to solve an OLTP problem or a DSS problem. all of the leading database manufacturers believe they have the right solution. This would be correct if the needs of an OLTP application resembled those of a DSS application. But in fact. their needs are very different, The physical database internal architecture designed to optimize for OLTP is very different from one designed to optimize for DSS, Not only would these two architectures be different, they would also be opposing. An architecture that optimized for DSS will degrade OLTP. and vice versa. We can say that OLTP and DSS have "" Opposing Laws of Database Physics "" There is also a relationship between the volume of data and the ability of a gwen optimized approach to work well."
"In a New York Times article from May 21, 2020, poet and essayist Cathy Park Hong lamented the ""nine productions of works by playwrights of Asian descent that were cut short or canceled in New York City because of Covid-19 ""1 Of course, the pandemic resulted in cancelations or postponements of productions all over the world, including two major theatre conferences and festivals that would have centered Asian Canadian and Asian American performance: one to be hosted in Toronto and the other in Hawaii, respectively, during May and August 2020."
"Decision-support applications generate queries with complex predicates. We show how the factorization of complex query expressions exposes significant opportunities for exploiting available indexes. We also present a novel idea of relaxing predicates in a complex condition to create possibilities for factoring. Our algorithms are designed for easy integration with existing query optimizers and support multiple optimization levels, providing different trade-offs between plan complexity and optimization time."
"Whereas serializability captures database consistency requirements and transaction correctness properties via a single notion, recent research has attempted to come up with correctness criteria that view these two types of requirements independently. The search for more flexible correctness criteria is partily motivated by the introduction of new transaction models that extend the traditional atomic transaction model. These extensions came about because the atomic transaction model in conjunction with serializability is found to be very constraining when used in advanced applications (e.g., design databases) that function in distributed, cooperative, and heterogeneous environments. In this article we develop a taxonomy of various correctness criteria that focus on database consistency requirements and transaction correctness properties from the viewpoint of what the different dimensions of these two are. This taxonomy allows us to categorize correctness criteria that have been proposed in the literature. To help in this categorization, we have applied a uniform specification technique, based on ACTA, to express the various criteria. Such a categorization helps shed light on the similarities and differences between different criteria and places them in perspective."
"This issue presents you with three workshop reports organized by Brian Cooper, the new associate editor for the workshop reports and technical notes. The first report summarized the events and discussions at the EDBT summer school on XML and Databases, contributed by Riccardo Torlone and Paolo Atzeni. The second report by Ioana Manolescu and Tannis Papakonstantinou, gives an overview of the workshop on the XQuery implementation, Experience, and Perspectives, which was held this year in Paris, France, incorporation with the ACM SIGMOD conference."
"In this column, we review these three books: 1. The Problem With Software: Why Smart Engineers Write Bad Code, by Adam Barr. Answers to a question many of us have probably asked; and what we can do about it. Review by Shoshana Marcus. 2. Elements of Parallel Computing, by Eric Aubanel. A textbook on the underpinnings of this important and fascinating area of computer science. Review by Michele Amoretti. 3. Theorems of the 21st Century: Volume I, by Bogdan Grechuk. The background, context, and statement of numerous important (accessible) mathematical theorems from the past 20 years. Review by William Gasarch."
"Better knowledge of natural enemy communities and their relative contribution to biological control is needed to design ecology-based pest management in agro-ecosystems. Here, we investigated the arthropod communities of pearl millet-based agro-ecosystems in sub-Saharan Africa (Senegal), with a focus on natural enemies of the millet head miner (MHM), Heliocheilus albipunctella (de Joannis)."
"Tree pattern is at the core of XML queries. The tree patterns in XML queries typically contain redundancies, especially when broad integrity constraints (ICs) are present and considered. Apparently, tree pattern minimization has great significance for efficient XML query processing. Although various minimization schemes/algorithms have been proposed, none of them can exploit broad ICs for thoroughly minimizing the tree patterns in XML queries. The purpose of this research is to develop an innovative minimization scheme and provide a novel implementation algorithm.Design/methodology/approach ¨C Query augmentation/expansion was taken as a necessary first©\step by most prior approaches to acquire XML query pattern minimization under the presence of certain ICs."
"This paper provides an introduction to the major research directions in biodiversity informatics. The biodiversity enterprise is a vast and complex information domain. I describe the need to build infrastructure for this domain, major research thrusts needed to improve its work practices, and areas of research that could contribute to the advancement of the field. I emphasize that the science of biodiversity is fundamentally an information science, worthy of special attention from the computer and information science communities because of its distinctive attributes of scale and socio-technical complexity."
"Due to organizational or operational constraints, the diverse data sources that an enterprise uses do not generally lend themselves to being fully replicated or completely consolidated under a single database, hence the increased demand for data interchange and for federated access to distributed sources. IBM has ongoing work in information integration technology that enables integrated, real-time access to traditional and emerging data sources, transforms information to meet the needs of business analysts, and manages data placement for performance, currency, and availability leading to fast, constant, and easy access for customer e-business solutions. IBM's Information Integration infrastructure today supports SQL¡ªa mature, powerful query language¡ªplus a number of SQL extensions in support of XML."
"The North Carolina Department of Health and Human Services, through the Division of Public Health and the Division of Aging and Adult Services, has adopted an evidence-based self-management curriculum called Living Healthy in NC that uses peer-to-peer learning to improve the ability of persons to manage their diseases, including diabetes, and to prevent or slow the progression of chronic conditions. The program is based on Stanford University¡¯s Chronic Disease Self-Management Program (CDSMP) and is being implemented in North Carolina through broad and diverse partnerships within and between multiple systems. Kate Lorig and colleagues at the Stanford Patient Education Research Center created and evaluated the CDSMP in the early 1990s, recognizing that physician care is only part of the disease-management process and that persons with chronic conditions must be good self-managers 24 hours a day, 7 days a week."
"Text models focus on the manipulation of textual data. They describe texts by their structure, operations on the texts, and constraints on both structure and operations. In this article common characteristics of machine readable texts in general are outlined. Subsequently, ten text models are introduced. They are described in terms of the datatypes that they support, and the operations defined by these datatypes. Finally, the models are compared."
"The focus of our work is to design and build a dynamic data distribution system that is coherence-preserving, i.e. the delivered data must preserve associated coherence requirements (the user-specified bound on tolerable imprecision) and resilient to failures. To this end, we consider a system in which a set of repositories cooperate with each other and the sources, forming a peer-to-peer network. In this system, necessary changes are pushed to the users so that they are automatically informed, about changes of interest. We present techniques 1) to determine when to push an update from one repository to another for coherence maintenance, 2) to construct an efficient dissemination tree for propagating changes from sources to cooperating repositories, and 3) to make the system resilient to failures."
"Users expect high and constant rendering frame rates when they interactively navigate in a Virtual Environment (VE). However, when the VE is too large to t into the main memory, the frame rates can become unacceptable. In this paper, we combine walkthrough semantics and database techniques, such as indexing, caching and prefetching, to improve the performance of walkthrough of a very large VE. We implemented a prototype walkthrough system called REVIEW (REaltime VIrtual Environment Walkthrough) and evaluated its performance on a 1 GB synthetic data-set generated to simulate a large cityscape."
"In this paper we focus on a critical issue in business process quality: that of analyzing, predicting and preventing the occurrence of exceptions, i.e., of deviations from the desired or acceptable behavior. We characterize the problem and propose a solution, based on data warehousing and mining t We then describe the architecture and implementation of a tool suite that enables exception analysis, prediction, and prevention. Finally, we show experimental results obtained by using the tool suite to analyze internal HP processes."
"In these environments, the best retrieval performance can be achieved only if the data is clustered on the tertiary storage by all searchable attributes of the events. Since the number of these attributes is high, the underlying data-management facility must be able to cope with extremely large volumes and very high dimensionalities of data at the same time. The proposed indexing technique is designed to facilitate both clustering and efficient retrieval of high-dimensional data on tertiary storage. The structure uses an original space-partitioning scheme, which has numerous advantages over other space-partitioning techniques. While the main objective of the design is to support high-energy physics experiments, the proposed solution is appropriate for many other scientific applications."
"With the growing popularity of the internet and the World Wide Web (Web), there is a fast growing demand for access to database management systems (DBMS) from the Web. We describe here techniques that we invented to bridge the gap between HTML, the standard markup language of the Web, and SQL, the standard query language used to access relational DBMS. We propose a flexible general purpose variable substitution mechanism that provides cross-language variable substitution between HTML input and SQL query strings as well as between SQL result rows and HTML output thus enabling the application developer to use the full capabilities of HTML for creation of query forms and reports, and SQL for queries and updates. The cross-language variable substitution mechanism has been used in the design and implementation of a system called DB2 WWW Connection that enables quick and easy construction of applications that access relational DBMS data from the Web."
"TimesTen Performance Software's Front-Tier product is an application-tier data cache that inter-operates with disk-based relational database management systems (RDBMSs) to achieve breakthrough response time and throughput, scalability in transaction load, high availability, and ease of administration and deployment. Front-Tier caches frequently used subsets of the corporate database on multiple servers in the application tier and supports SQL queries and updates to the caches. The caches may or may not be overlapping, are kept synchronized with the corporate database and with each other, and may be dynamically reconfigured to contain different subsets of the corporate database."
"Decision support applications are growing in popularity as more business data is kept on-line. Such applications typically include complex SQL queries that can test a query optimizer's ability to produce an efficient access plan. Many access plan strategies exploit the physical ordering of data provided by indexes or sorting. Sorting is an expensive operation, however. Therefore, it is imperative that sorting is optimized in some way or avoided all together. Toward that goal, this paper describes novel optimization techniques for pushing down sorts in joins, minimizing the number of sorting columns, and detecting when sorting can be avoided because of predicates, keys, or indexes."
"This paper describes a system, WebSemantics, that accomplishes the above tasks. We describe an architecture for the publication and discovery of scientific data sources, which is an extension of the World Wide Web architecture and protocols. We support catalogs containing metadata about data sources for some application domain. We define a language for discovering sources and querying their metadata. We then describe the WebSemantics prototype."
"Gestures and speech interact. They are linked in language production and perception, with their interaction contributing to felicitous communication. The multifaceted nature of these interactions has attracted considerable attention from the speech and gesture community. This article provides an overview of our current understanding of manual and head gesture form and function, of the principle functional interactions between gesture and speech aiding communication, transporting meaning and producing speech. Furthermore, we present an overview of research on temporal speech-gesture synchrony, including the special role of prosody in speech-gesture alignment."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
"This paper presents DEDALE, a spatial database system intended to overcome some limitations of current systems by providing an abstract and non-specialized data model and query language for the representation and manipulation of spatial objects. DEDALE relies on a logical model based on linear constraints, which generalizes the constraint database model of [KKR90]. While in the classical constraint model, spatial data is always decomposed into its convex components, in DEDALE holes are allowed to fit the need of practical applications. The logical representation of spatial data although slightly more costly in memory, has the advantage of simplifying the algorithms. DEDALE relies on nested relations, in which all sorts of data (thematic, spatial, etc.) are stored in a uniform fashion. This new data model supports declarative query languages, which allow an intuitive and efficient manipulation of spatial objects. Their formal foundation constitutes a basis for practical query optimization."
"We propose a semantic model for client-side caching and replacement in a client-server database system and compare this approach to page caching and tuple caching strategies. Our caching model is based on, and derives its advantages from, three key ideas. First, the client maintains a semantic description of the data in its cache,which allows for a compact specification, as a remainder query, of the tuples needed to answer a query that are not available in the cache. Second, usage information for replacement policies is maintained in an adaptive fashion for semantic regions, which are associated with collections of tuples. This avoids the high overheads of tuple caching and, unlike page caching, is insensitive to bad clustering. Third, maintaining a semantic description of cached data enables the use of sophisticated value functions that incorporate semantic notions of locality, not just LRU or MRU, for cache replacement."
"The goal of the COKO-KOLA project is to express rules of rule-based optimizers in a manner permitting verification with a theorem prover. In this paper, we consider the complementary issue of expressing query transformations that are too specifc for rewrite rules. Such transformations require rewrite rules to be supplemented with semantic conditions to guard rule firing. This work considers the expression of such transformations using conditional rewrite rules, and the expression of inference rules to guide the optimizer in deciding if semantic conditions hold. This work differs from existing work in semantic query optimization in that semantic transformations in our framework are verifiable with a theorem prover."
"An under-appreciated facet of index search structures is the importance of high performance search within B-tree internal nodes. Much attention has been focused on improving node fanout, and hence minimizing the tree height [BU77, LL86]. [GG97, Lo98] have discussed the importance of B-tree page size. A recent article [GL2001] discusses internal node architecture, but the subject is buried in a single section of the paper.In this short note, I want to describe the long evolution of good internal node architecture and techniques, including an understanding of what problem was being solved during each of the incremental steps that have led to much improved node organizations."
"Testing the reliability of high performance tlansaetion processing systams poses many difficult challenges that are not adequately answered by conventional testing techniques. We discuss a new test paradigm, which is dynamic and exploratory in nature, and discuss its ability to meet these challenges. We describe an implementation of thii paradigm in products that aid in efficiently testing reliable, high performance transaction processing systems at T~adem Computers Inc."
"The cost functions are parameterized to accommodate various hardware characteristics appropriately. Combining the basic patterns, we can describe the memory access patterns of database operations. The cost functions of database operations can automatically be derived by combining the basic patterns' cost functions accordingly. To validate our approach, we performed experiments using our DBMS prototype Monet. The results presented here confirm the accuracy of our cost models for different operations. Aside from being useful for query optimization, our models provide insight to tune algorithms not only in a main-memory DBMS, but also in a disk-based DBMS with a large main-memory buffer cache."
"A special-purpose extension of the Entity-Relationship model for the needs of conceptual modeling of geographic applications, called the Geo-ER Model, is presented. Handling properties associated to objects not because of the objects' nature but because of the objects' position, calls for dealing -at the semantic modeling level-with space, location and dimensionality of objects, spatial relationships, space-depending attributes, and scale and generalization of representations. In order to accomplish this in the framework of ER and its derivatives, we introduce special entity sets, relationships, and add new constructs. The rationale as well as examples of usage of the Geo-ER model from actual projects are presented."
"We study the process in which search engines with segmented indices serve queries. In particular, we investigate the number of result pages that search engines should prepare during the query processing phase.Search engine users have been observed to browse through very few pages of results for queries that they submit. This behavior of users suggests that prefetching many results upon processing an initial query is not efficient, since most of the prefetched results will not be requested by the user who initiated the search. However, a policy that abandons result prefetching in favor of retrieving just the first page of search results might not make optimal use of system resources either."
"Should digital libraries be based on image or text display? Which will serve users better? Experience and experiments show that users can employ either, and that there are technical advantages to each format. Often, material in both formats can be used together, and the long-run trend is probably towards Ascii material, even if reached by a circuitous path via images and OCR during a transition."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
"We develop a simple yet powerful classification of MDBSs based on the nature of integrity constraints and transaction programs. For each of the identified models we show how consistency can be preserved by ensuring that executions are two-level serializable (2LSR). 2LSR is a correctness criterion for MDBS environments weaker than serializability. What makes our approach interesting is that unlike global serializability, ensuring 2LSR in MDBS environments is relatively simple and protocols to ensure 2LSR permit a high degree of concurrency. Furthermore, we believe the range of models we consider cover many practical MDBS environments to which the results of this article can be applied to preserve database consistency."
"Object-relational database systems, a.k.a. ¡°universal servers,¡± are emerging as the next major generation of commercial database system technology. Products from relational DBMS vendors including IBM, Informix, Oracle, UniSQL, and others, include object-relational features today, and all of the major vendors appear to be on course to delivering full object-relational support in their products over the next few years. In addition, the SQL3 standard is rapidly solidifying in this area. The goal of this tutorial is to explain what the key features are of object-relational database systems, review what today's products provide, and then look ahead to where these systems are heading. The presentation will be aimed at general SIGMOD audience, and should therefore be appropriate for users, practitioners, and/or researchers who want to learn about object-relational database systems."
"Client-server object-oriented database management systems differ significantly from traditional centralized systems in terms of their architecture and the applications they target. In this paper, we present the client-server architecture of the EOS storage manager and we describe the concurrency control and recovery mechanisms it employs. EOS offers a semi-optimistic locking scheme based on the multi-granularity two-version two-phase locking protocol. Under this scheme, multiple concurrent readers are allowed to access a data item while it is being updated by a single writer. Recovery is based on write-ahead redo-only logging."
"Many papers have examined how to efficiently export a materialized view but to our knowledge none have studied how to efficiently import one. To import a view, i.e., to install a stream of updates, a real-time database system must process new updates in a timely fashion to keep the database ""fresh,"" but at the same time must process transactions and ensure they meet their time constraints. In this paper, we discuss the various properties of updates and views (including staleness) that affect this tradeoff. We also examine, through simulation, four algorithms for scheduling transactions and installing updates in a soft real-time database."
"Constraints provide a flexible and uniform way to represent diverse data capturing spatio-temporal behavior, complex modeling requirements, partial and incomplete information etc, and have been used in a wide variety of application domains. Constraint databases have recently emerged to deeply integrate data captured by constraints in databases. This paper reports on the development of the first constraint object-oriented database system, CCUBE, and describes its specification, design and implementation. The CCUBE system is designed to be used for the implementation and optimization of high-level constraint object-oriented query languages as well as for directly building software systems requiring extensible use of constraint database features. The CCUBE data manipulation language, Constraint Comprehension Calculus, is an integration of a constraint calculus for extensible constraint domains within monoid comprehensions, which serve as an optimization-level language for object-oriented queries."
"Indexes and access methods have been a staple of database research ¨C and indeed of computer science in general ¨C for decades. A glance at the contents of this year¡¯s SIGMOD and PODS proceedings shows another bumper crop of indexing papers. Given the hundreds of indexing papers published in the database literature, a pause for reflection seems in order. From a scientific perspective, it is natural to ask why definitive indexing solutions have eluded us for so many years. What is the grand challenge in indexing? What basic complexities or intricacies underlie this large body of work? What would constitute a successful completion of this research agenda, and what steps will best move us in that direction? Or is it the case that the problem space branches in so many ways that we should expect to continuously need to solve variants of the indexing problem? From the practitioner¡¯s perspective, the proliferation of indexing solutions in the literature may be more confusing than helpful. Comprehensively evaluating the research to date is a near-impossible task."
"They can reduce the need to scan large tables in joins. Results from the customer benchmark demonstrate their usefulness. We also describe hashed groupings, which eliminate sorts to form groups for subsequent aggregation, Hashed groupings allow execution of queries in the benchmark that were previously impossible. Maintenance of the decision support database (updates, addition of indexes, changes in its physical layout) must be performed regularly, and it is increasingly desirable that the database be available during these operations. To this end, Tandem is introducing a host of new on-line data management operations, including data partition adds, drops, splits and moves, as well as on-line index creation. We describe the implementation of partition moves as an example. The basic idea is to move a ¡°dirty¡± copy of the data, and then to bring the new copy up to date by applying log records describing the effects of transactions that took place during the move. Other on-line data management operations are similar"
"Arrays are a common and important class of data. At present, database systems do not provide adequate array support: arrays can neither be easily defined nor conveniently manipulated. Further, array manipulations are not optimized. This paper describes a language called the Array Manipulation Language (AML), for expressing array manipulations, and a collection of optimization techniques for AML expressions.In the AML framework for array manipulation, arbitrary externally-defined functions can be applied to arrays in a structured manner. AML can be adapted to different application domains by choosing appropriate external function definitions. This paper concentrates on arrays occurring in databases of digital images such as satellite or medical images.AML queries can be treated declaratively and subjected to rewrite optimizations. Rewriting minimizes the number of applications of potentially costly external functions required to compute a query result. AML queries can also be optimized for space. Query results are generated a piece at a time by pipelined execution plans, and the amount of memory required by a plan depends on the order in which pieces are generated. An optimizer can consider generating the pieces of the query result in a variety of orders, and can efficiently choose orders that require less space."
"A very large number of data sources on environment, energy, and natural resources are available worldwide. Unfortunately, users usually face several problems when they want to search and use relevant information. In the Ecobase project, we address these problems in the context of several environmental applications in Brazil and Europe. We propose a distributed architecture for environmental information systems (EIS) based on the Le Select middleware developed at INRIA. In this paper, we present this architecture and its capabilities, and discuss the lessons learned and open issues."
"This diploma thesis covers information system SAP R3 which dates in year 1972. During decades it has been improved and spread almost in all areas of data handling in companies. By help of different modules the system covers human resources, production planning, material management, plant maintenance, project system, etc. The basic navigations in SAP R3 run by help of shortcuts of programs, called transaction. The business applications of system are divided in standard and customer applications. Standard applications are complex, extensive and general thus for easier application usually customer programs are developed covering only smaller area of company¡¯s needs. Thus, customer applications are easier to use for end-users."
"The 1998 Nagano Olympic games had more intensive demands on data management than any previous Olympics in history. This talk will take you behind the scenes to talk about the technical challenges and the architectures that made it possible to handle 4.5 Terabytes of data and sustain a total of almost 650 million web requests, reaching a peak of over 103K per minute. We will discuss the overall structure of the most comprehensive and heavily used Internet technology application in history. Many products were involved, both hardware and software, but this talk will focus in on the database and web challenges, the technology that made it possible to support this tremendous workload. High availability, data integrity, high performance, support of both SMPs and clustered architectures were among the features and functions that were critical."
"The system Mosaico has been conceived to support the design, conceptual modeling, and rapid prototyping of data intensive applications based on Object-Oriented Databases (OODBS). The application is modeled through a graphical user interface and the produced model is encoded in TQL++, the design language on which Mosaico is based."
"XML filtering solutions developed to date have focused on the matching of documents to large numbers of queries but have not addressed the customization of output needed for emerging distributed information infrastructures. Support for such customization can significantly increase the complexity of the filtering process. In this paper, we show how to leverage an efficient, shared path matching engine to extract the specific XML elements needed to generate customized output in an XML Message Broker."
"Karen Marschke-Tobier, chair of our Extension Committee, is looking into this possibility and her group will be aided in this project by the Program Committee. They will also be arranging the workshop for mental health professionals to take place in Boston. After reviewing the grant proposals that we received, one from the New York Psychoanalytic Institute and one from the Chicago Institute for Psychoanalysis, the Executive Council voted to approve both applications."
Newsletter Editor Ramin Rahmani In this Issue Chair¡¯s Message 1 Report on ASME Journal of Fluids Engineering 3 FED Technical Committee Reports Fluid Applications and Systems Technical Committee 4 Microand Nano-Scale Fluid Dynamics Technical Committee 5 Multiphase Flow Technical Committee 6 Computational Fluid Dynamics Technical Committee 7 Fluid Measurement and Instrumentation Technical Committee 8 Fluid Mechanics Technical Committee 9 FED Awards Honors and Awards 10 Fluids Engineering Awards 10 Fluids Machinery Design Award 10 Robert T. Knapp Award 11 Lewis F. Moody Award 11 S. Gopalakrishnan¡ªFlowserve Pump Technology Award 12 Freeman Scholar Awards 12 Technical Articles Furnace Wall
"Disk-based database systems benefit from concurrency among transactions - usually with marginal overhead. For main-memory database systems, however, locking overhead can have a serious impact on performance. This paper proposes SP, a serial protocol for the execution of transactions in main-memory systems, and evaluates its performance against that of strict two-phase locking. The novelty of SP lies in the use of timestamps and mutexes to allow one transaction to begin before its predecessors' commit records have been written to disk, while also ensuring that no committed transactions read uncommitted data. We demonstrate seven-fold and two-fold increases in maximum throughput for read-and update-intensive workloads, respectively. At fixed loads, we demonstrate ten-fold and two-fold improvements in response time for the same transaction mixes."
"Interesting patterns often occur at varied levels of support. The classic association mining based on a uniform minimum support, such as Apriori, either misses interesting patterns of low support or suuers from the bottleneck of itemset generation. A better solution is to exploit support constraints, which specify what minimum support is required for what itemsets, so that only necessary itemsets are generated. In this paper, we present a framework of frequent itemset mining in the presence of support constraints. Our approach is to \push"" support constraints into the Apriori itemset generation so that the \best"" minimum support is used for each itemset at run time to preserve the essence of Apriori."
"Connectivity products are finally available to provide the ¡°highways¡± between computers containing data. IBM has provided strong validation of the concept with their ¡°Information Warehouse.¡± DBMS vendors are providing gateways into their products, and SQL is being retrofitted on many older DBMSs to make it easier to access data from standard 4GL products and application development systems. The next step needed for data integration is to provide (1) a common data dictionary with a conceptual schema across the data to mask the many differences that occur when databases are developed independently and (2) a server that can access and integrate the databases using information from the data dictionary. In this article, we discuss InterViso, one of the first commercial federated database products."
"Active object oriented database management systems (AODBMS) are finding increasing application in different application domains and especially for cooperative and long duration activity management. In this paper, we propose a concurrency control mechanism for open nested transactions in an AODBMS. It exploits the semantics of the transactions to achieve controlled cooperation and concurrency among the transactions. Atomic AODBMS transactions are treated as base transactions. A complex transaction type is formed from a collection of base and complex transactions, a set of detached mode ECA rules and a state transition model. The cooperation semantics of a complex transaction type with other complex transaction types is specified by associating with each state of a complex transaction, a set of cooperating complex transaction types."
"A multidimensional database is a data repository that supports the efficient execution of complex business decision queries. Query response can be significantly improved by storing an appropriate set of materialized views. These views are selected from the multidimensional lattice whose elements represent the solution space of the problem. Several techniques have been proposed in the past to perform the selection of materialized views for databases with a reduced number of dimensions. When the number and complexity of dimensions increase, the proposed techniques do not scale well. The technique we are proposing reduces the soluticn space by considering only the relevant elements of the multidimensional lattice. An additional statistical analysis allows a further reduction of the solution space."
"In this paper, we study a simple SQL extension that enables query writers to explicitly limit the cardinality of a query result. We examine its impact on the query optimization and run-time execution components of a relational DBMS, presenting two approaches¡ªa Conservative approach and an Aggressive approach¡ªto exploiting cardinality limits in relational query plans. Results obtained from an empirical study conducted using DB2 demonstrate the benefits of the SQL extension and illustrate the tradeoffs between our two approaches to implementing it."
"SHORE (Scalable Heterogeneous Object REpository) is a persistent object system under development at the University of Wisconsin. SHORE represents a merger of object-oriented database and file system technologies. In this paper we give the goals and motivation for SHORE, and describe how SHORE provides features of both technologies. We also describe some novel aspects of the SHORE architecture, including a symmetric peer-to-peer server architecture, server customization through an extensible value-added server facility, and support for scalability on multiprocessor systems."
"This paper examines a technique for dynamically inserting and removing drop operators into query plans as required by the current load. We examine two types of drops: the first drops a fraction of the tuples in a randomized fashion, and the second drops tuples based on the importance of their content. We address the problems of determining when load shedding is needed, where in the query plan to insert drops, and how much of the load should be shed at that point in the plan. We describe efficient solutions and present experimental evidence that they can bring the system back into the useful operating range with minimal degradation in answer quality."
"We present a framework which allows the user to access and manipulate data uniformly, regardless of whether it resides in a database or in the file system (or in both). A key issue is the performance of the system. We show that text indexing, combined with newly developed optimization techniques, can be used to provide an efficient high level interface to information stored in files. Furthermore, using these techniques, some queries can be evaluated significantly faster than in standard database implementations. We also study the tradeoff between efficiency and the amount of indexing."
"In this paper, we present a unifying framework called Rain Forest for classification tree construction that separates the scalability aspects of algorithms for constructing a tree from the central features that determine the quality of the tree. The generic algorithm is easy to instantiate with specific split selection methods from the literature (including C4.5, CART, CHAID, FACT, ID3 and extensions, SLIQ, SPRINT and QUEST).In addition to its generality, in that it yields scalable versions of a wide range of classification algorithms, our approach also offers performance improvements of over a factor of three over the SPRINT algorithm, the fastest scalable classification algorithm proposed previously. In contrast to SPRINT, however, our generic algorithm requires a certain minimum amount of main memory, proportional to the set of distinct values in a column of the input relation."
"We describe a system that supports arbitrarily complex SQL queries with ¡±uncertain¡± predicates. The query semantics is based on a probabilistic model and the results are ranked, much like in Information Retrieval. Our main focus is query evaluation. We describe an optimization algorithm that can compute eciently most queries. We show, however, that the data complexity of some queries is #P-complete, which implies that these queries do not admit any ecient evaluation methods. For these queries we describe both an approximation algorithm and a Monte-Carlo simulation algorithm."
"In this paper we present a prototype system for the management of earth science data which is novel in that it takes a DBMS centric view of the the task. Our prototype -called ""BigSur"" -is shown in the context of its use by two geographically distributed scientific groups with demanding data storage and processing requirements. BigSur currently stores 1 Terabyte of data, about one thousandth of the volume EOSDIS must store. We claim that the design principles embodied in BigSur provide sufficient flexibility to achieve the difficult scientific and technical objectives of Mission to Planet Earth."
"The MITRE Corporation provides technical assistance, system engineering, and acquisition support to large organizations, especially U.S. Government agencies. We help our customers to plan complex systems based on emerging technologies, and to implement systems based on commercial-off-the-shelf products. In MITRE's research program, instead of emphasizing concerns of DBMS or CASE vendors, our research emphasizes the issues of organizations who need to use such products. For example, we favor areas where we can build over commercial products, rather than changing their internals.Data management at MITRE goes beyond research, to include technology transition, system engineering, product evaluation, prototypes, tutorials, advice on customers' strategic directions, and participation in standards efforts. We use prototyping to illustrate potential improvements in customer systems, to understand vendors' capabilities, or both. There are close connections with efforts in object management, real-time systems, reengineering, artificial intelligence, and security."
"In this paper, we propose a novel constraint definition called XFDs that capture structural as well as semantic information. We present a set of rewriting rules for XFDs, and use them to design a polynomial time algorithm which, given an input set of XFDs, computes a reduced set of XFDs. Based on this algorithm, we present a redundancy removing storage mapping from XML to relations called RRXS. The effectiveness of the mapping is demonstrated by experiments on three data sets."
"Recent work on querying data streams has focused on systems where newly arriving data is processed and continuously streamed to the user in real time. In many emerging applications, however, ad hoc queries and/or intermittent connectivity also require the processing of data that arrives prior to query submission or during a period of disconnection. For such applications, we have developed PSoup, a system that combines the processing of ad hoc and continuous queries by treating data and queries symmetrically, allowing new queries to be applied to old data and new data to be applied to old queries. PSoup also supports intermittent connectivity by separating the computation of query results from the delivery of those results. PSoup builds on adaptive query-processing techniques developed in the Telegraph project at UC Berkeley. In this paper, we describe PSoup and present experiments that demonstrate the effectiveness of our approach."
In this paper we describe an application of the lexical resource JurWordNet and of the Core Legal Ontology as a descriptive vocabulary for modeling legal domains. It can be viewed as the semantic component of a global standardisation framework for digital governments. A content description model provides a repository of structured knowledge aimed at supporting the semantic interoperability between sectors of Public Administration and the communication processes towards citizen. Specific conceptual models built from this base will act as a cognitive interface able to cope with specific digital government issues and to improve the interaction between citizen and Public Bodies.
"Xyleme is a dynamic warehouse for XML data of the Web supporting query evaluation, change control and data integration. We briefly present our motivations, the general architecture and some aspects of Xyleme. The project we describe here was completed at the end of 2000. A prototype has been implemented. This prototype is now being turned into a product by a start-up company also called Xyleme [14]. Xyleme: a complex tissue of wood cells, functions in conduction and storage ..."
"Text is a pervasive information type, and many applications require querying over text sources in addition to structured data. This paper studies the problem of query processing in a system that loosely integrates an extensible database system and a text retrieval system. We focus on a class of conjunctive queries that include joins between text and structured data, in addition to selections over these two types of data. We adapt techniques from distributed query processing and introduce a novel class of join methods based on probing that is especially useful for joins with text systems, and we present a cost model for the various alternative query processing methods. Experimental results confirm the utility of these methods. The space of query plans is extended due to the additional techniques, and we describe an optimization algorithm for searching this extended space. The techniques we describe in this paper are applicable to other types of external data managers loosely integrated with a database system."
"Classification, which involves finding rules that partition a given da.ta set into disjoint groups, is one class of data mining problems. Approaches proposed so far for mining classification rules for large databases are mainly decision tree based symbolic learning methods. The connectionist approach based on neura.l networks has been thought not well suited for data mining. One of the major reasons cited is that knowledge generated by neural networks is not explicitly represented in the form of rules suitable for verification or interpretation by humans. This paper examines this issue. With our newly developed algorithms, rules which are similar to, or more concise than those generated by the symbolic methods can be extracted from the neural networks. The data mining process using neural networks with the emphasis on rule extraction is described. ExperimenM results and comparison with previously published works are presented."
"Many database applications in the real world are no longer built on top of a stand-alone database system. Rather, generic (standard) application systems are employed in which the database system is one integrated component. SAP is the market leader for integrated business administration systems, and its SAP R/3 product is a comprehensive software system which integrates modules for finance, material management, sales and distribution, etc. From an architectural point of view, SAP R/3 is a client/server application system with a relational database system as back-end. SAP supports a choice between a variety of commercial relational database products."
"s [41, 42]. academia [1932, 1926, 2267, 2275]. academic [1908, 2441]. acceleration [1869]. Access [2370, 13, 38, 1530, 1620, 1555, 2106, 1643, 1410, 602, 1672, 1033, 531, 601, 803, 1532, 1531, 949, 2204, 1455, 657, 598, 1263, 1086, 749, 409, 1969, 319, 2119, 450, 872, 1808, 171, 1559, 238, 821, 812, 1209, 1198, 694, 126, 1357, 883, 2139]. accesses [406]. Accessing [1295, 127, 515]. Accommodating [626]. account [1889]. accounting [679]. accrued [2385]. Accurate [276, 855]. achieve [858]. Achievements [1238, 619, 627]. ACID [1688]. ACM [38, 2139, 2216, 14, 2106, 2290, 2291, 42, 2239, 2445, 13, 2472, 2475, 2476, 2477, 2479, 2480, 1580, 1099, 2478, 2130, 2474, 1946, 1697, 2213, 2029, 2143, 2319, 2397, 2262]. ACM-SIGFIDET [38, 14]. Acquisition [288]. Across [1645, 2393, 1936]. ACT [1322]. ACT-NET [1322]. ACTA [586]. action [761]. Actions [1329]. activation [851]. Active [1322, 1239, 970, 833, 1471, 272, 1574, 1407, 1071, 1321, 1236, 1174, 420, 1171, 546, 1914, 1178, 1470, 766, 1098, 521, 1228, 1444, 1126, 1065]. Activities [136, 984, 216, 156, 1965, 587, 67, 748, 820]. activity [1311, 196]. Actual [211]. Ad [1394, 2001, 2056, 3]. ad-hoc [2001]. Ada [249, 458]. ADAM [1897]. adapt [2406]. Adaptable [1807]. adaptation [2113, 2328, 1209]. Adapting [1121, 254]. Adaptive [1730, 1675, 1002, 1642, 1024, 1826, 1112, 1737, 304, 1282, 307, 1809, 567]. ADBIS¡¯2001 [1931]. ADBMS [1321, 1322]. adding [463]. Addison [2043, 66]. Addison-Wesley [66]. Address [1148, 749, 1147, 642]. Addressing [1199]. ADEPT [1588]. Administering [221, 1303]. Administration [1478, 53]. Ado [1317]. ADO.NET [2236]. ADS [1071]. Advanced [1881, 952, 740, 1765, 2405, 1062, 678, 924, 1177]. Advancements [2105]. Advances [1227, 1931]. advantage [1163]. adventure [2310]. adversarial [2337]. Affiliation [2402]. after [1121]. again [1875]. against [471, 1939]. Agenda [1040]. Agent [1386, 1607, 2047, 1588, 1919, 1198, 2065]. Agent-Based [1386, 1607, 1588, 1198]."
"Performance of object-oriented database systems (OODBs) is still an issue to both designers and users nowadays. The aim of this paper is to propose a generic discrete-event random simulation model, called VOODB, in order to evaluate the performances of OODBs in general, and the performances of optimization methods like clustering in particular. Such optimization methods undoubtedly improve the performances of OODBs. Yet, they also always induce some kind of overhead for the system. Therefore, it is important to evaluate their exact impact on the overall performances. VOODB has been designed as a generic discrete-event random simulation model by putting to use a modelling approach, and has been validated by simulating the behavior of the O2 OODB and the Texas persistent object store. Since our final objective is to compare object clustering algorithms, some experiments have also been conducted on the DSTC clustering technique, which is implemented in Texas. To validate VOODB, performance results obtained by simulation for a given experiment have been compared to the results obtained by benchmarking the real systems in the same conditions. Benchmarking and simulation performance evaluations have been observed to be consistent, so it appears that simulation can be a reliable approach to evaluate the performances of OODBs."
The SkyServer provides Internet access to the public Sloan Digital Sky Survey (SDSS) data for both astronomers and for science education. This paper describes the SkyServer goals and architecture. It also describes our experience operating the SkyServer on the Internet. The SDSS data is public and well-documented so it makes a good test platform for research on database algorithms and performance.
"Conduct of scientific and engineering research is becoming critically dependent on effective management of scientific and engineering data and technical information. The rapid advances in scientific instrumentation, computer and communication technologies enable the scientists to collect, generate, process, and share unprecedented volumes of data. For example, the Earth Observing System Data and Information System (EOSDIS) has the task to manage the data from NASA¡¯s Earth science research satellites and field measurement programs, and other data essential for the interpretation of these measurements in support of global change research. Apart from being able to handle a stream of 1 terabyte of data daily by the year 2000, EOSDIS will also need to provide transparent access to heterogeneous data held in the archives of several US government agencies, organizations and countries. A single graphical user interface employing the Global Change Master Directory needs to help users locate data sets of interest among massive and diverse data sets, or find the appropriate data analysis tools, regardless of their location. Another major international effort in the area of human genome research faces some similar, as well as unique issues due to the complexity of the genome data, special querying requirements and much more heterogeneous collections of data. Scientific databases can be viewed as critical repositories of knowledge, both existing and yet to be dis-"
"One of the key problems in developing and integrating expert systems for medical research is the problem of data aggregation. Most of the times, general information about the patient and data about undergone research procedures exist as part of several disconnected information systems, each using its own schema for presenting and storing information. The paper proposes a solution to aggregate research and patient data in medical establishments using formal projections mechanism, which allows to unify data extraction from separate data sources. Graph-based patient and research record representation is introduced, which allows to support and optimize complex queries for single patient and for a set of historical data from single research."
"This paper deals with finding outliers (exceptions) in large, multidimensional datasets. The identification of outliers can lead to the discovery of truly unexpected knowledge in areas such as electronic commerce, credit card fraud, and even the analysis of performance statistics of professional athletes. Existing methods that we have seen for finding outliers in large datasets can only deal efficiently with two dimensions/attributes of a dataset. Here, we study the notion of DB- (DistanceBased) outliers. While we provide formal and empirical evidence showing the usefulness of DB-outliers, we focus on the development of algorithms for computing such outliers. First, we present two simple algorithms, both having a complexity of O(k N¡¯), k being the dimensionality and N being the number of objects in the dataset. These algorithms readily support datasets with many more than two attributes. Second, we present an optimized cell-based algorithm that has a complexity that is linear wrt N, but exponential wrt k. Third, for datasets that are mainly disk-resident, we present another version of the cell-based algorithm that guarantees at most 3 passes over a dataset. We provide"
In this paper we examine the issues involved in developing information visualisation systems and present a framework for their construction. The framework addresses the components which must be considered in providing effective visualisations. The framework is specified using a declarative object oriented language; the resulting object model may be mapped to a variety of graphical user interface development platforms. This provides general support to developers of visualisation systems. A prototype system exists which allows the investigation of alternative visualisations for a range of data sources. 
"Integrated access to information that is spread over multiple, distributed, and heterogeneous sources is an important problem in many scienti c and commercial domains. While much work has been done on query processing and choosing plans under cost criteria, very little is known about the important problem of incorporating the information quality aspect into query planning. In this paper we describe a framework for multidatabase query processing that fully includes the quality of information in many facets, such as completeness, timeliness, accuracy, etc. We seamlessly include information quality into a multidatabase query processor based on a view-rewriting mechanism. We model information quality at di erent levels to ultimately nd a set of high-quality queryanswering plans."
"Within 10 years people will have hundreds of interconnected computing devices around them. Many connections will be wireless and many devices will store data in them. With a billion or more mobile users having a hundred devices we face a ubiquitous (IP) network with a very large (100B) small and hidden or embedded databases as well as \always-on"" connection to all kind of databases in the network. How to solve, e.g., the challenges of security, replication and resilience? Some of the answers are visible already in today's mobile telephone and Internet networks. But many answers and even possible problems are not known yet. "
"We discovered a surprising law governing the spatial join selectivity across two sets of points. An example of such a spatial join is ¡°find the libraries that are within 10 miles of schools¡±. Our law dictates that the number of such qualifying pairs follows a power law, whose exponent we call ¡°pair-count exponent¡± (PC). We show that this law also holds for self-spatial-joins (¡°find schools within 5 miles of other schools¡±) in addition to the general case that the two point-sets are distinct. Our law holds for many real datasets, including diverse environments (geographic datasets, feature vectors from biology data, galaxy data from astronomy). In addition, we introduce the concept of the Box-Occupancy-Product-Sum (BOPS) plot, and we show that it can compute the pair-count exponent in a timely manner, reducing the run time by orders of magnitude, from quadratic to linear. Due to the pair-count exponent and our analysis (Law 1), we can achieve accurate selectivity estimates in constant time (O(1)) without the need for sampling or other expensive operations. The relative error in selectivity is about 30% with our fast BOPS method, and even better (about 10%), if we use the slower, quadratic method."
"The Red Brick WarehouseTMis a commercial Relational Database Management System designed specifically for query, decision support, and data warehouse applications. Red Brick Warehouse is a software-only system providing ANSI SQL support in an open cliendserver environment. Red Brick Warehouse is distinguished from traditional RDBMS products by an architecture optimized to deliver high performance in read-mostly, high-intensity query applications. In these applications, the workload is heavily biased toward complex SQL SELECT operations that read but do not update the database. The average unit of work is very large, and typically involves multi-table joins, aggregation, duplicate elimination, and sorting. Multi-user concurrency is moderate, with typical systems supporting 50 to 500 concurrent user sessions. Query databases are often very large, with tables ranging from 100 million to many billion rows and occupying 50 Gigabytes to 2 Terabytes, Databases are populated by massive bulk-load operations on an hourly, daily, or weekly cycle. Time-series and historical data are maintained for months or years. Red Brick Warehouse makes use of parallel processing as well as other specialized algorithms to achieve outstanding performance and scalability on cost-effective hardware platforms."
"This paper provides an overview of the 1995 International Workshop on Temporal Databases. It summarizes the technical papers and related discussions, and three panels: ¡°Wither TSQL3?¡±, ¡°Temporal Data Management in Financial Applications,¡± and ¡°Temporal Data Management Infrastructure & Beyond.¡±"
"This paper describes the design and implementation of an OODBMS, namely the METU Object-Oriented DBMS (MOOD). MOOD [Dog 94b] is developed on the Exodus Storage Manager (ESM) [ESM 92] and therefore some of the kernel functions like storage management, concurrency control, backup and recovery of data were readily available through ESM. In addition ESM has a client-server architecture and each MOOD process is a client application in ESM. The kernel functions provided by MOOD are the optimization and interpretation of SQL statements, dynamic linking of functions, and catalog management. SQL statements are interpreted whereas functions (which have been previously compiled with C++) within SQL statements are dynamically linked and executed. A query optimizer is implemented by using the Volcano Query Optimizer Generator. A graphical user interface, namely Mood-View [Arp 93a, Arp 93b], is developed using Motif. MoodView displays both the schema information and the query results graphically. Additionally it is possible to update the database schema and to traverse the references in query results graphically.The system is coded in GNU C++ on Sun Sparc 2 workstations. MOOD has a SQL-like object-oriented query language, namely MOODSQL [Ozk 93b, Dog 94c]. MOOD type system is derived from C++, thus eliminating the impedance mismatch between MOOD and C++. The users can also access the MOOD Kernel from their application programs written in C++. For this purpose MOOD Kernel defines a class named UserRequest that contains a method for the execution of MOODSQL statements. The MOOD source code is available both for anonymous ftp users from ftp.cs.wisc.edu and for the WWW users from the site http://www.srdc.metu.edu.tr along with its related documents.In MOOD, each object is given a unique Object Identifier (OID) at object creation time by the ESM which is the disk start address of the object returned by the ESM. Object encapsulation is considered in two parts, method encapsulation and attribute encapsulation. These encapsulation properties are similar to the public and private declarations of C++.Methods can be defined in C++ by users to manipulate user defined classes and after compilation, they are dynamically linked and executed during the interpretation of SQL statements. This late binding facility is essential since database environments enforce run-time modification of schema and objects. With our approach, the interpretation of functions are avoided thus increasing the efficiency of the system. Dynamic linking primitives are implemented by the use of the shared object facility of SunOS [Sun 90]. Overloading is realized by making use of the signature concept of C++."
"Thor is an object-oriented database system designed for use in a heterogeneous distributed environment. It provides highly-reliable and highly-available persistent storage for objects, and supports safe sharing of these objects by applications written in different programming languages.Safe heterogeneous sharing of long-lived objects requires encapsulation: the system must guarantee that applications interact with objects only by invoking methods. Although safety concerns are important, most object-oriented databases forgo safety to avoid paying the associated performance costs.This paper gives an overview of Thor's design and implementation. We focus on two areas that set Thor apart from other object-oriented databases. First, we discuss safe sharing and techniques for ensuring it; we also discuss ways of improving application performance without sacrificing safety. Second, we describe our approach to cache management at client machines, including a novel adaptive prefetching strategy.The paper presents performance results for Thor, on several OO7 benchmark traversals. The results show that adaptive prefetching is very effective, improving both the elapsed time of traversals and the amount of space used in the client cache. The results also show that the cost of safe sharing can be negligible; thus it is possible to have both safety and high performance."
"Due to the recent growth of the World Wide Web, numerous spatio-temporal applications can obtain their required information from web sources. In this demonstration we show The WorldInfo Assistant, an application that extracts and integrates spatial, temporal and other information about dierent regions of the world from dierent web sources and databases. This application also provides integration of dierent vector data with the satellite images of dierent regions of the world. Finally, We demonstrate several approaches for ecient querying moving objects with predefined paths and schedules."
"Reusable ontologies are becoming increasingly important for tasks such as information integration, knowledge-level interoperation and knowledge-base development. We have developed a set of tools and services to support the process of achieving consensus on commonly shared ontologies by geographically distributed groups. These tools make use of the World Wide Web to enable wide access and provide users with the ability to publish, browse, create and edit ontologies stored on anontology server. Users can quickly assemble a new ontology from a library of modules. We discuss how our system was constructed, how it exploits existing protocols and browsing tools, and our experience supporting hundreds of users. We describe applications using our tools to achieve consensus on ontologies and to integrate information.The Ontolingua Server may be accessed through the URLhttp://ontolingua.stanford.edu"
"This paper provides an overview of the current database research activities within the Intelligent Information Systems Group in the Department of Computer Science and Engineering at Arizona State University. The focus of our research is on the integration of data and knowledge management issues, with specific emphasis on multimedia systems, object-oriented databases, active databases, deductive databases, and heterogeneous, distributed database environments."
"We discuss the design and implementation of the O 2 Views object-oriented database view mechanism, which allows the redeenition of both the structure and the behavior of objects stored in a database. The data model extended with views is rst given and then the functionalities of the prototype implementing it are presented. The paper focuses on the requirements for the implementation of an object-oriented view mechanism, ranging from the conception of a view deenition language to optimization strategies for querying and updating through a view such as view materialization and consistency maintenance."
"Expectations for change are ubiquitous in education. Teachers who complete education programs and enter classrooms are encouraged to embrace change as new professionals. Instructional change is expected as a result of professional development when teachers examine their instructional practices and reflect on student learning. Two scholars whose work is foundational in teacher education, Lortie (2002) and Britzman (2003) challenged researchers and educators to consider how teachers and teacher education changes and resists change. Lortie (2002), in his sociological study of the profession, speculated on changes and resistance in teaching and argued that the two would ¡°interact contrapuntally¡± (p. 219). In other words, these two forces exist in tension so that sustained change would often be thwarted. In a similar vein, Britzman¡¯s (2003) critical analysis of learning to teach examined discourses and discursive structures of teacher preparation and noted contradictions and struggles in the lived experiences of teacher candidates. Near the conclusion of her analysis, she wrote, we should ¡°attend to the possible and acknowledge the uncertainty of our educational lives¡± (p. 241). Possibilities and uncertainties continue to inform the work of educating teacher candidates and supporting inservice teachers as agents of innovation in schools. To be sure, schools and teaching have changed in terms of student demographics, accountability, standardization, and testing since these two studies were published. And yet, the articles in this issue suggest that exploring sources, motivation, and possible outcomes of change, as well as the nature of resistance, remain paramount. In this issue, one pedagogical innovations article and four empirical studies articles explore change and consider how resistance informs teacher education. In an argument for including data literacy in teacher preparation, Reeves describes six hours of classroom-based training with four cohorts of preservice elementary teachers that he claims will help them more deeply understand how data literacy can inform pedagogy. Reeves¡¯ study is grounded in current research indicating that there is an increased expectation for teachers to use data to make instructional decisions. He contends that teacher preparation programs should include instruction about data literacy. This change could help preservice teachers enter classrooms with detailed knowledge about how data can productively inform their instruction. Reeves recognizes that such a change will require thoughtful consideration about when such instruction should be part of curricula; that these shifts will demand new resources; and, resistance to adding another facet to teacher education programs is possible. Reinhardt investigates how six cooperating teachers understand their roles within contexts of clinical experiences using Vygotskian theory. Her qualitative study focused on four female and two male teacher mentors in a diverse school district and examined how the cooperating teachers understand their role in a clinical experience as contrasted with the reality of teachers¡¯ everyday work. "
"The proliferation of data in RDF format has resulted in the emergence of a plethora of specialized management systems. While the ability to adapt to the complexity of a SPARQL query -- given their inherent diversity -- is crucial, current approaches do not scale well when faced with substantially complex, non-selective joins, resulting in exponential growth of execution times. In this demonstration we present H2 RDF+, an RDF store that efficiently performs distributed Merge and Sort-Merge joins using a multiple-index scheme over HBase indexes. Through a greedy planner that incorporates our cost-model, it adaptively commands for either single or multi-machine query execution based on join complexity. In this paper, we present its key scientific contributions and allow participants to interact with an H2RDF+ deployment over a Cloud infrastructure. Using a web-based GUI we allow users to load different datasets (both real and synthetic), apply any query (custom or predefined) and monitor its execution. By allowing real-time inspection of cluster status, response times and committed resources the audience will evaluate the validity of H2RDF+'s claims and perform direct comparisons to two other state-of-the-art RDF stores."
"Today's industrial control systems store large amounts of monitored sensor data in order to optimize industrial processes. In the last decades, architects have designed such systems mainly under the assumption that they operate in closed, plant-side IT infrastructures without horizontal scalability. Cloud technologies could be used in this context to save local IT costs and enable higher scalability, but their maturity for industrial applications with high requirements for responsiveness and robustness is not yet well understood. We propose a conceptual architecture as a basis to designing cloud-native monitoring systems. As a first step we benchmarked three open source time-series databases (OpenTSDB, KairosDB and Databus) on cloud infrastructures with up to 36 nodes with workloads from realistic industrial applications. We found that at least KairosDB fulfills our initial hypotheses concerning scalability and reliability."
"Majority of current Business Intelligence Data (BID) is spread out between incompatible tools like RDBMSs, OLAP engines, and spreadsheets. Bridges between them allow interchange of data and metadata thus providing a small degree of BID sharing, but due to lack of metadata standards, this sharing is limited to speci c installations. This creates an unacceptable situation where an analyst cannot get a complete picture of a business. A solution is needed, the Collaborative Analytical Processing (CAP) solution, which imposes a very tight integration between the tools so (meta) data interchange, change management, scalability and data availability is as good as in RDBMSs, and performance of OLAP queries is as good as in the specialized OLAP engines. Any CAP solution must assist business tools through simpli cation and integration so they can focus on business models, relationship management, fact discovery and presentation than on availability, performance and scalability. This panel will discuss feasibility of such solution and its place in the spectrum between RDBMS and specialized OLAP engines. "
"In this paper, we address the need to automatically classify text documents into topic hierarchies like those in ACM Digital Library and Yahoo!. The existing local approach constructs a classi er at each split of the topic hierarchy. However, the local approach does not address the closeness of classi cation in hierarchical classi cation where the concern often is how close a classi cation is, rather than simply correct or wrong. Also, the local approach puts its bet on classi cation at higher levels where the classi cation structure often diminishes. To address these issues, we propose the notion of class proximity and cast the hierarchical classi cation as a at classi cation with the class proximity modeling the closeness of classes. Our approach is global in that it constructs a single classi er based on the global informationabout all classes and class proximity. We leverage generalized association rules as the rule/feature space to address several other issues in hierarchical classi cation."
"This demo combines active DB technology in open, heterogeneous environments with the Web presence requirements of nomadic users. It illustrates these through profiling of users and Internet-enabled vehicles. A scenario is developed in which useful functionality is provided, such as instrument adjustments, maintenance and diagnostic information handling with the corresponding workflows, and convenience features, such as position-dependent language translation support and traffic information. The customization mechanism relies on an active functionality service."
"In outsourced database (ODB)systems the database owner publishes its data through a number of remote servers, with the goal of enabling clients at the edge of the network to access and query the data more efficiently. As servers might be untrusted or can be compromised, query authentication becomes an essential component of ODB systems. Existing solutions for this problem concentrate mostly on static scenarios and are based on idealistic properties for certain cryptographic primitives. In this work, first we define a variety of essential and practical cost metrics associated with ODB systems. Then, we analytically evaluate a number of different approaches, in search for a solution that best leverages all metrics. Most importantly, we look at solutions that can handle dynamic scenarios, where owners periodically update the data residing at the servers. Finally, we discuss query freshness, a new dimension in data authentication that has not been explored before. A comprehensive experimental evaluation of the proposed and existing approaches is used to validate the analytical models and verify our claims. Our findings exhibit that the proposed solutions improve performance substantially over existing approaches, both for static and dynamic environments."
"A Bayesian network is an appropriate tool to deal with the uncertainty that is typical of real-life applications. Bayesian network arcs represent statistical dependence between different variables. In the data mining field, association and correlation rules can be interpreted as well as expressing statistical dependence relations. K2 is a well-known algorithm which is able to learn Bayesian networks. In this paper we present two extensions of K2 called K2-Lift and K2-X2 that exploit two parameters normally defined in relation to association and correlation rules. The experiments performed show that K2-Lift and K2-X2 improve K2 with respect to both the quality of the learned network and the execution time."
"Caching has been proposed (and implemented) by OLAP systems in order to reduce response times for multidimensional queries. Previous work on such caching has considered table level caching and query level caching. Table level caching is more suitable for static schemes. On the other hand, query level caching can be used in dynamic schemes, but is too coarse for ¡°large¡± query results. Query level caching has the further drawback for small query results in that it is only effective when a new query is subsumed by a previously cached query. In this paper, we propose caching small regions of the multidimensional space called ¡°chunks¡±. Chunk-based caching allows fine granularity caching, and allows queries to partially reuse the results of previous queries with which they overlap. To facilitate the computation of chunks required by a query but missing from the cache, we propose a new organization for relational tables, which we call a ¡°chunked file.¡± Our experiments show that for workloads that exhibit query locality, chunked caching combined with the chunked file organization performs better than query level caching. An unexpected benefit of the chunked file organization is that, due to its multidimensional clustering properties, it can significantly improve the performance of queries that ¡°miss¡± the cache entirely as compared to traditional file organizations."
"In a digital library system, documents are available in digital form and therefore are more easily copied and their copyrights are more easily violated. This is a very serious problem, as it discourages owners of valuable information from sharing it with authorized users. There are two main philosophies for addressing this problem: prevention and detection. The former actually makes unauthorized use of documents difficult or impossible while the latter makes it easier to discover such activity.In this paper we propose a system for registering documents and then detecting copies, either complete copies or partial copies. We describe algorithms for such detection, and metrics required for evaluating detection mechanisms (covering accuracy, efficiency, and security). We also describe a working prototype, called COPS, describe implementation issues, and present experimental results that suggest the proper settings for copy detection parameters."
"Association Rule Mining algorithms operate on a data matrix (e.g., customers products) to derive association rules [2, 23]. We propose a new paradigm, namely, Ratio Rules, which are quanti able in that we can measure the \goodness"" of a set of discovered rules. We propose to use the \guessing error"" as a measure of the \goodness"", that is, the rootmean-square error of the reconstructed values of the cells of the given matrix, when we pretend that they are unknown. Another contribution is a novel method to guess missing/hidden values from the Ratio Rules that our method derives. For example, if somebody bought $10 of milk and $3 of bread, our rules can \guess"" the amount spent on, say, butter. Thus, we can perform a variety of important tasks such as forecasting, answering \what-if"" scenarios, detecting outliers, and visualizing the data. Moreover, we show how to compute Ratio Rules in a single pass over the dataset with small memory requirements (a few small matrices), in contrast to traditional association rule mining methods that require multiple passes and/or large memory. ExperWork performed while at the University of Maryland. This research was partially funded by the Institute for Systems Research (ISR), and by the National Science Foundation under Grants No. EEC-94-02384, IRI-9205273 and IRI-9625428. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the VLDB copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Very Large Data Base Endowment. To copy otherwise, or to republish, requires a fee and/or special permission from the Endowment. Proceedings of the 24th VLDB Conference New York, USA, 1998 iments on several real datasets (e.g., basketball and baseball statistics, biological data) demonstrate that the proposed method consistently achieves a \guessing error"" of up to 5 times less than the straightforward competitor."
"Abstract. Relational database systems have traditionally optimized for I/O performance and organized records sequentially on disk pages using the N-ary Storage Model (NSM) (a.k.a., slotted pages). Recent research, however, indicates that cache utilization and performance is becoming increasingly important on modern platforms. In this paper, we first demonstrate that in-page data placement is the key to high cache performance and that NSM exhibits low cache utilization on modern platforms. Next, we propose a new data organization model called PAX (Partition Attributes Across), that significantly improves cache performance by grouping together all values of each attribute within each page. Because PAX only affects layout inside the pages, it incurs no storage penalty and does not affect I/O behavior. According to our experimental results (which were obtained without using any indices on the participating relations), when compared to NSM: (a) PAX exhibits superior cache and memory bandwidth utilization, saving at least 75% of NSM's stall time due to data cache accesses; (b) range selection queries and updates on memory-resident relations execute 17¨C25% faster; and (c) TPC-H queries involving I/O execute 11¨C48% faster. Finally, we show that PAX performs well across different memory system designs."
"In digital libraries image retrieval queries can be based on the similarity of objects, using several feature attributes like shape, texture, color or text. Such multi-feature queries return a ranked result set instead of exact matches. Besides, the user wants to see only the k top-ranked objects. We present a new algorithm called Quick-Combine (European patent pending, nr. EP 00102651.7) for combining multi-feature result lists, guaranteeing the correct retrieval of the k top-ranked results. For score aggregation virtually any combining function can be used, including weighted queries. Compared to Fagin¡¯s algorithm we have developed an improved termination condition in tuned combination with a heuristic control flow adopting itself narrowly to the particular score distribution. Top-ranked results can be computed and output incrementally. We show that we can dramatically improve performance, in particular for non-uniform score distributions. Benchmarks on practical data indicate efficiency gains by a factor of 30. For very skewed data observed speed-up factors are even larger. These performance results scale through different database sizes and numbers of result sets to combine."
"The date of 31 January 2018 marked the adoption in Hong Kong of a three-phased law banning trading in elephant ivory that will come into full effect on 31 December 2021. This follows the decision of mainland China outlawing this practice from 31 December 2017. These new ordinances, which derive from an international convention (CITES), are particularly adapted to these places as they represent (with Japan) the world¡¯s principal destination of ivory, both legal and illegal, and have done so since the 1950s. This trade, and especially its illegal strand, threatens the survival of Africa¡¯s elephants, whose ivory is regarded as precious."
"In this article we present an approach to integrity maintenance, consisting of automatically generating production rules for integrity enforcement. Constraints are expressed as particular formulas of Domain Relational Calculus; they are automatically translated into a set of repair actions, encoded as production rules of an active database system. Production rules may be redundant (they enforce the same constraint in different ways) and conflicting (because repairing one constraint may cause the violation of another constraint). Thus, it is necessary to develop techniques for analyzing the properties of the set of active rules and for ensuring that any computation of production rules after any incorrect transaction terminates and produces a consistent database state. Along these guidelines, we describe a specific architecture for constraint definition and enforcement. The components of the architecture include a Rule Generator, for producing all possible repair actions, and a Rule Analyzer and Selector, for producing a collection of production rules such that their execution after an incorrect transaction always terminates in a consistent state (possibly by rolling back the transaction); moreover, the needs of applications are modeled, so that integrity-enforcing rules reach the final state that better represents the original intentions of the transaction's supplier. Specific input from the designer can also drive the process and integrate or modify the rules generated automatically by the method. Experimental results of a prototype implementation of the proposed architecture are also described."
"Data warehouses support the analysis of historical data. This often involves aggregation over a period of time. Furthermore, data is typically incorporated in the warehouse in the increasing order of a time attribute, e.g., date of sale or time of a temperature measurement. In this paper we propose a framework to take advantage of this append only nature of updates due to a time attribute. The framework allows us to integrate large amounts of new data into the warehouse and generate historical summaries efficiently. Query and update costs are virtually independent from the extent of the data set in the time dimension, making our framework an attractive aggregation approach for append-only data streams. "
"Client-server database systems based on a data shipping model can exploit client memory resources by caching copies of data items across transaction boundaries. Caching reduces the need to obtain data from servers or other sites on the network. In order to ensure that such caching does not result in the violation of transaction semantics, a transactional cache consistency maintenance algorithm is required. Many such algorithms have been proposed in the literature and, as all provide the same functionality, performance is a primary concern in choosing among them. In this article we present a taxonomy that describes the design space for transactional cache consistency maintenance algorithms and show how proposed algorithms relate to one another. We then investigate the performance of six of these algorithms, and use these results to examine the tradeoffs inherent in the design choices identified in the taxonomy. The results show that the interactions among dimensions of the design space impact performance in many ways, and that classifications of algorithms as simply ¡°pessimistic¡± or ¡°optimistic¡± do not accurately characterize the similarities and differences among the many possible cache consistency algorithms."
"Benchmarks belong to the very standard repertory of tools deployed in database development. Assessing the capabilities of a system, analyzing actual and potential bottlenecks, and, naturally, comparing the pros and cons of different systems architectures have become indispensable tasks as databases management systems grow in complexity and capacity. In the course of the development of XML databases the need for a benchmark framework has become more and more evident: a great many different ways to store XML data have been suggested in the past, each with its genuine advantages, disadvantages and consequences that propagate through the layers of a complex database system and need to be carefully considered. The different storage schemes render the query characteristics of the data variably different. However, no conclusive methodology for assessing these differences is available to date.In this paper, we outline desiderata for a benchmark for XML databases drawing from our own experience of developing an XML repository, involvement in the definition of the standard query language, and experience with standard benchmarks for relational databases."
"In this paper we describe the support for data feed ingestion in AsterixDB, an open-source Big Data Management System (BDMS) that provides a platform for storage and analysis of large volumes of semi-structured data. Data feeds are a mechanism for having continuous data arrive into a BDMS from external sources and incrementally populate a persisted dataset and associated indexes. The need to persist and index ""fast-flowing"" high-velocity data (and support ad hoc analytical queries) is ubiquitous. However, the state of the art today involves 'gluing' together different systems. AsterixDB is different in being a unified system with ""native support"" for data feed ingestion.  We discuss the challenges and present the design and implementation of the concepts involved in modeling and managing data feeds in AsterixDB. AsterixDB allows the runtime behavior, allocation of resources and the offered degree of robustness to be customized to suit the high-level application(s) that wish to consume the ingested data. Initial experiments that evaluate scalability and fault-tolerance of AsterixDB data feeds facility are reported."
"We introduce a new algorithm to compute the spatial join of two or more spatial data sets, when indexes are not available on them. Size Separation Spatial Join (S<3J<) imposes a hierarchical decomposition of the data space and, in contrast with previous approaches, requires no replication of entities from the input data sets. Thus its execution time depends only on the sizes of the joined data sets. We describe S<3J< and present an analytical evaluation of its I/O and processor requirements comparing them with those of previously proposed algorithms for the same problem. We show that S<3J< has relatively simple cost estimation formulas that can be exploited by a query optimizer. S<3J< can be efficiently implemented using software already present in many relational systems. In addition, we introduce Dynamic Spatial Bitmaps< (DSB), a new technique that enables S<3J< to dynamically or statically exploit bitmap query processing techniques. Finally, we present experimental results for a prototype implementation of S<3J< involving real and synthetic data sets for a variety of data distributions. Our experimental results are consistent with our analytical observations and demonstrate the performance benefits of S<3J< over alternative approaches that have been proposed recently."
"Hash-based scalable distributed data structures (SDDSs), like LH* and DDH, for networks of interconnected computers (multicomputers) were shown to open new perspectives for file management. We propose a family of ordered SDDSs, called RP*, providing for ordered and dynamic files on multicomputers, and thus for more efficient processing of range queries and of ordered traversals of files. The basic algorithm termed RP*N, builds the file with the same key space partitioning as a B-tree, but avoids indexes through the use of multicast. The algorithms, RP*C and RP*S enhance throughput for faster networks, adding the indexes on clients, or on clients and servers, while either decreasing or avoiding multicast. RP* files are shown highly efficient with access performance exceeding traditional files by an order of magnitude or two, and, for non-range queries, very close to LH*."
"We introduce the problem of mining association rules in large relational tables containing both quantitative and categorical attributes. An example of such an association might be ""10% of married people between age 50 and 60 have at least 2 cars"". We deal with quantitative attributes by fine-partitioning the values of the attribute and then combining adjacent partitions as necessary. We introduce measures of partial completeness which quantify the information lost due to partitioning. A direct application of this technique can generate too many similar rules. We tackle this problem by using a ""greater-than-expected-value"" interest measure to identify the interesting rules in the output. We give an algorithm for mining such quantitative association rules. Finally, we describe the results of using this approach on a real-life dataset."
"Mining for associations between items in large transactional databases is a central problem in the field of knowledge discovery. When the database is partitioned among several share-nothing machines, the problem can be addressed using distributed data mining algorithms. One such algorithm, called CD, was proposed by Agrawal and Shafer in [1] and was later enhanced by the FDM algorithm of Cheung, Han et al. [5]. The main problem with these algorithms is that they do not scale well with the number of partitions. They are thus impractical for use in modern distributed environments such as peer-to-peer systems, in which hundreds or thousands of computers may interact. In this paper we present a set of new algorithms that solve the Distributed Association Rule Mining problem using far less communication. In addition to being very efficient, the new algorithms are also extremely robust. Unlike existing algorithms, they continue to be efficient even when the data is skewed or the partition sizes are imbalanced. We present both experimental and theoretical results concerning the behavior of these algorithms and explain how they can be implemented in different settings."
"Automated database design systems embody knowledge about the database design process. However, their lack of knowledge about the domains for which databases are being developed significantly limits their usefulness. A methodology for acquiring and using general world knowledge about business for database design has been developed and implemented in a system called the Common Sense Business Reasoner, which acquires facts about application domains and organizes them into a a hierarchical, context-dependent knowledge base. This knowledge is used to make intelligent suggestions to a user about the entities, attributes, and relationships to include in a database design. A distance function approach is employed for integrating specific facts, obtained from individual design sessions, into the knowledge base (learning) and for applying the knowledge to subsequent design problems (reasoning)."
"The tutorial is structured as follows: First, we give a brief motivation for clustering from modern data mining applications. We discuss important design decisions and explain the interdependencies with the properties of data. In the second section, we introduce a large variety of clustering methods and classify them into three groups ¡ª modeland optimization-based methods, linkageand densitybased methods, and hybrid methods. A detailed comparison shows the strength and weaknesses of the existing techniques and reveals potentials for further improvements. In the next two section, we discuss database techniques which have been proposed to improve the effectiveness and efficiency of the cluster discover process. The four main categories of techniques which can be used for this purpose are hierarchical and incremental approaches, multidimensional indexing, sampling, and condensationbased approaches. The tutorial concludes with a discussion of open problems and future research issues. "
"The rate of increase in database size and response-time requirements has outpaced advancements in processor and mass storage technology. One way to satisfy the increasing demand for processing power and input/output bandwidth in database applications is to have a number of processors, loosely or tightly coupled, serving database requests concurrently. Technologies developed during the last decade have made commercial parallel database systems a reality, and these systems have made an inroad into the stronghold of traditionally mainframe-based large database applications. This paper describes the DB2? Parallel Edition product that evolved from a prototype developed at IBM Research in Hawthorne, New York, and now is being jointly developed with the IBM Toronto laboratory."
"Semi-structured documents (e.g. journal art,icles, electronic mail, television programs, mail order catalogs, . ..) a.re often not explicitly typed; the only available t,ype information is the implicit structure. An explicit t,ype, however, is needed in order to a.pply objectoriented technology, like type-specific methods. In this paper, we present a.n experimental vector space cla.ssifier for determining the type of semi-structured documents. Our goal was to design a. high-performa.nce classifier in t,erms of accuracy (recall and precision), speed, and extensibility."
"The authors' perspective of database mining as the confluence of machine learning techniques and the performance emphasis of database technology is presented. Three classes of database mining problems involving classification, associations, and sequences are described. It is argued that these problems can be uniformly viewed as requiring discovery of rules embedded in massive amounts of data. A model and some basic operations for the process of rule discovery are described. It is shown how the database mining problems considered map to this model, and how they can be solved by using the basic operations proposed. An example is given of an algorithm for classification obtained by combining the basic rule discovery operations. This algorithm is efficient in discovering classification rules and has accuracy comparable to ID3, one of the best current classifiers. >"
"XML has emerged as the standard data exchange format for Internet-based business applications. This has created the need to publish existing business data, stored in relational databases, as XML. A general way to publish relational data as XML is to provide XML views over relational data, and allow business partners to query these views using an XML query language. In this paper, we address the problem of evaluating XML queries over XML views of relational data. This paper makes two main contributions. The first is a general framework for processing arbitrarily complex queries specified using the XQuery query language. The second is a technique for efficiently evaluating XML queries by pushing most of the query computation down to the relational engine."
"Abstract. We describe a novel approach for clustering collections of sets, and its application to the analysis and mining of categorical data. By ¡°categorical data,¡± we mean tables with fields that cannot be naturally ordered by a metric ¨C e.g., the names of producers of automobiles, or the names of products offered by a manufacturer. Our approach is based on an iterative method for assigning and propagating weights on the categorical values in a table; this facilitates a type of similarity measure arising from the co-occurrence of values in the dataset. Our techniques can be studied analytically in terms of certain types of non-linear dynamical systems."
"This paper introduces a new efficient join algorithm to increase the speed of the join relational operation. Using a divide and conquer strategy, stack oriented filter technique in the new join algorithm filters unwanted tuples as early as possible while none of the currently existing join algorithms takes advantage of any filtering concept. Other join algorithms may carry the unnecessary tuples up to the last moment of join attribute comparisons.Four join algorithms are described and discussed in this paper: the nested-loop join algorithm, the sort-merge join algorithm, the hash join algorithm, and the new join algorithm."
"Next generation decision support applications, besides being capable of processing huge amounts of data, require the ability to integrate and reason over data from multiple, heterogeneous data sources. Often, these data sources differ in a variety of aspects such as their data models, the query languages they support, and their network protocols. Also, typically they are spread over a wide geographical area. The cost of processing decision support queries in such a setting is quite high. However, processing these queries often involves redundancies such as repeated access of same data source and multiple execution of similar processing sequences. Minimizing these redundancies would significantly reduce the query processing cost. In this paper, we (1) propose an architecture for processing complex decision support queries involving multiple, heterogeneous data sources; (2) introduce the notion of transient-views ¡ª materialized views that exist only in the context of execution of a query ¡ª that is useful for minimizing the redundancies involved in the execution of these queries; (3) develop a cost-based algorithm that takes a query plan as input and generates an optimal ¡°covering plan¡±, by minimizing redundancies in the original plan; (4) validate our approach by means of an implementation of the algorithms and a detailed performance study based on TPC-D benchmark queries on a commercial database system; and finally, (5) compare and contrast our approach with work in related areas, in particular, the areas of answering queries using views and optimization using common sub-expressions. Our experiments demonstrate the practicality and usefulness of transient-views in significantly improving the performance of decision support queries."
"Three designs of hierarchical locking suitable for B-tree indexes are explored in detail and their advantages and disadvantages compared. Traditional hierarchies include index, leaf page, and key range or key value. Alternatively, locks on separator keys in interior B-tree pages can protect key ranges of different sizes. Finally, for keys consisting of multiple columns, key prefixes of different sizes permit a third form of hierarchical locking. Each of these approaches requires appropriate implementation techniques. The techniques explored here include node splitting and merging, lock escalation and lock de-escalation, and online changes in the granularity of locking. Those techniques are the first designs permitting introduction and removal of levels in a lock hierarchy on demand and without disrupting transaction or query processing. In addition, a simplification of traditional key range locking is introduced that applies principled hierarchical locking to keys in B-tree leaves. This new method of key range locking avoids counter-intuitive lock modes used in today¡¯s highperformance database systems. Nonetheless, it increases concurrency among operations on individual keys and records beyond that enabled by traditional lock modes."
"An important requirement for multimedia presentations is the ability to compose new multimedia objects from the existing ones using temporal relationships. When compositions of continuous media objects are specified dynamically, the task of displaying these objects poses new challenges. These challenges are addressed in this paper. We show that in the case of a single composite object retrieval, a prefetching technique, simple sliding, provides an approach to reduce latency and buffering requirements. We extend this prefetching technique to the problem of retrieving multiple composite objects simultaneously. This new technique is termed buffered sliding. We consider several variants of the buffered sliding algorithm. A simulationbased study is used to compare their usage pattern of available memory and in determining their relative merits in reducing latency and increasing disk bandwidth utilization. *Research supported in part by the National Science Foundation under grants IRI-9203389, IRI-9258362 (NY1 award), and CDA-9216321, and a Hewlett-Packard unrestricted cash/equipment gift. Permission to copy without fee all OT part of this material is granted provided that the copies are not made OT distributed for direct commercial advantage, the VLDB copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Very Large Data Base Endowment. To copy otherwise, OT to republish, Tequires a fee and/or special permission from the Endowment. Proceedings of the 21st VLDB Conference Zurich, Swizerland, 1995 An important requirement for multimedia information systems is the ability to compose new multimedia objects from the existing multimedia objects [LG91]. Temporal primitives (e.g., before, after, overlaps [All83]) p rovide one of the most powerful and natural ways of authoring composition. Such composition is necessary in the domain of electronic publishing, computer music, news editing and many other applications. In this paper, we investigate how a multimedia storage system can display a composite object. We focus on composite objects that are authored dynamically. To illustrate an example environment, consider a TVnews editor preparing to present new footage on unrest in Bosnia. He requires background material to provide the audience with a context. He considers playing a sequence of clips one after another from different footage taken at different times to author a thirty second presentation. He may decide to accompany a footage with appropriate music in parts (i.e., music overlaps video). He may conclude his presentatiod with split windows that concurrently display short clips that leave us with the images of diverse scenes in Bosnia. During editing of such a presentation, he would try several possible composition, possibly picking different sets of clips or music from the repository. Surely, the editor would like to display his composition during the authoring process to evaluate his choice.¡¯ Thus, the process of editing a news story consisted of specifying composite objects using temporal relationships and then displaying those. Note that displaying atomic objects of highbandwidth continuous media objects, such as video (requiring no composition) is a challenging task in itself. Video clips require a continuous bandwidth for their display. For example, the bandwidth re-"
"We extend the relational data model to incorporate partial orderings into data domains, which we call the ordered relational model. Within the extended model, we define the partially ordered relational algebra (the PORA) by allowing the ordering predicate ? to be used in formulae of the selection operator (¦Ò). The PORA expresses exactly the set of all possible relations that are invariant under order-preserving automorphism of databases. This result characterizes the expressiveness of the PORA and justifies the development of Ordered SQL (OSQL) as a query language for ordered databases. "
"A new sort algorithm, called AlphaSort, demonstrates that commodity processors and disks can handle commercial batch workloads. Using commodity processors, memory, and arrays of SCSI disks, AlphaSort runs the industrystandard sort benchmark in seven seconds. This beats the best published record on a 32-CPU 32-disk Hypercube by 8:1. On another benchmark, AlphaSort sorted more than a gigabyte in one minute. AlphaSort is a cache-sensitive, memoryintensive sort algorithm. We argue that modern architectures require algorithm designers to re-examine their use of the memory hierarchy. AlphaSort uses clustered data structures to get good cache locality, file striping to get high disk bandwidth, QuickSort to generate runs, and replacement-selection to merge the runs. It uses shared memory multiprocessors to break the sort into subsort chores. Because startup times are becoming a significant part of the total time, we propose two new benchmarks: (1) MinuteSort: how much can you sort in one minute, and (2) PennySort: how much can you sort for one penny."
"Disk-based database systems use buffer managers in order to transparently manage data sets larger than main memory. This traditional approach is effective at minimizing the number of I/O operations, but is also the major source of overhead in comparison with in-memory systems. To avoid this overhead, in-memory database systems therefore abandon buffer management altogether, which makes handling data sets larger than main memory very difficult. In this work, we revisit this fundamental dichotomy and design a novel storage manager that is optimized for modern hardware. Our evaluation, which is based on TPC-C and micro benchmarks, shows that our approach has little overhead in comparison with a pure in-memory system when all data resides in main memory. At the same time, like a traditional buffer manager, it is fully transparent and can manage very large data sets effectively. Furthermore, due to low-overhead synchronization, our implementation is also highly scalable on multi-core CPUs."
"The Daytona#8482; data management system is used by AT&T to solve a wide spectrum of data management problems. For example, Daytona is managing a 4 terabyte data warehouse whose largest table contains over 10 billion rows. Daytona's architecture is based on translating its high-level query language Cymbal (which includes SQL as a subset) completely into C and then compiling that C into object code. The system resulting from this architecture is fast, powerful, easy to use and administer, reliable and open to UNIX#8482; tools. In particular, two forms of data compression plus robust horizontal partitioning enable Daytona to handle terabytes with ease."
"Abstract. Association Rule Mining algorithms operate on a data matrix (e.g., customers  $times$ products) to derive association rules [AIS93b, SA96]. We propose a new paradigm, namely, Ratio Rules, which are quantifiable in that we can measure the ¡°goodness¡± of a set of discovered rules. We also propose the ¡°guessing error¡± as a measure of the ¡°goodness¡±, that is, the root-mean-square error of the reconstructed values of the cells of the given matrix, when we pretend that they are unknown. Another contribution is a novel method to guess missing/hidden values from the Ratio Rules that our method derives. For example, if somebody bought $10 of milk and $3 of bread, our rules can ¡°guess¡± the amount spent on butter. Thus, unlike association rules, Ratio Rules can perform a variety of important tasks such as forecasting, answering ¡°what-if¡± scenarios, detecting outliers, and visualizing the data. Moreover, we show that we can compute Ratio Rules in a single pass over the data set with small memory requirements (a few small matrices), in contrast to association rule mining methods which require multiple passes and/or large memory. Experiments on several real data sets (e.g., basketball and baseball statistics, biological data) demonstrate that the proposed method: (a) leads to rules that make sense; (b) can find large itemsets in binary matrices, even in the presence of noise; and (c) consistently achieves a ¡°guessing error¡± of up to 5 times less than using straightforward column averages."
"? "" ¡­ make a computer so imbedded, so fitting, so natural, that we use it without even thinking about it. "" ? "" Ubiquitous (pervasive) computing is roughly the opposite of virtual reality. Where virtual reality puts people inside a computer-generated world, ubiquitous computing forces the computer to live out here in the world with people. "" ¨C Mark Weiser, Xerox PARC"
"There has been an abundance of research within the last couple of decades in the area of multilevel secure (MLS) databases. Recent work in this field deals with the processing of multilevel transactions, expanding the logic of MLS query languages, and utilizing MLS principles within the realm of E-Business. However, there is a basic flaw within the MLS logic, which obstructs the handling of clearance-invariant aggregate queries and physical-entity related queries where some of the information in the database may be gleaned from the outside world. This flaw stands in the way of a more pervasive adoption of MLS models by the developers of practical applications. This paper clearly identifies the cause of this impediment -- the cover story dependence on the value of a user-defined key -- and proposes a practical solution."
"The dramatic growth of the Internet has created a new problem for users: location of the relevant sources of documents. This article presents a framework for (and experimentally analyzes a solution to) this problem, which we call the text-source discovery problem. Our approach consists of two phases. First, each text source exports its contents to a centralized service. Second, users present queries to the service, which returns an ordered list of promising text sources. This article describes GlOSS, Glossary of Servers Server, with two versions: bGlOSS, which provides a Boolean query retrieval model, and vGlOSS, which provides a vector-space retrieval model. We also present hGlOSS, which provides a decentralized version of the system. We extensively describe the methodology for measuring the retrieval effectiveness of these systems and provide experimental evidence, based on actual data, that all three systems are highly effective in determining promising text sources for a given query."
"Answering aggregate queries like SUM, COUNT, MIN, MAX, AVG in an approximate manner is often desirable when the exact answer is not needed or too costly to compute. We present an algorithm for answering such queries in multi-dimensional databases, using selective traversal of a Multi-Resolution Aggregate (MRA) tree structure storing point data. Our approach provides 100% intervals of confidence on the value of the aggregate and works iteratively, coming up with improving quality answers, until some error requirement is satisfied or time constraint as reached. Using the same technique we can also answer aggregate queries exactly and our experiments indicate that even for exact answering the proposed data structure and algorithm are very fast."
"Relational queries on continuous streams of data are the subject of many recent database research projects. In 1998 a small group of people started a similar project with the goal to transform our product, NonStop SQL/MX, into an active RDBMS. This project tried to integrate functionality of transactional queuing systems with relational tables and with SQL, using simple extensions to the SQL syntax and guaranteeing clearly defined query and transactional semantics. The result is the first commercially available RDBMS that incorporates streams. All data flowing through the system is contained in relational tables and is protected by ACID transactions. Insert and update operations on any NonStop SQL table can be considered publishing of data and can therefore be transparent to the (legacy) applications performing them. "
"Data Warehousing embraces technology and industrial practice to systematically integrate data from multiple distributed data sources and to use that data in annotated and aggregated form to support business decision-making and enterprise management. Although many database techniques have been revisited or newly developed in the context of data warehouses, such as view maintenance and OLAP, little attention has been paid to the design, management and high quality service of the management of a given enterprise. Little attention is also paid to aspects that are intrinsic to the functionality and usage of data warehouses, either in the back-stage (like data cleansing or data extraction and loading) or in the front-end (like similar and uncertain queries, or what-if analysis). The DMDW workshop is intended as a forum to fill this gap."
"We generalize the method of constructing windows in subsequence matching. By this generalization, we can explain earlier subsequence matching methods as special cases of a common framework. Based on the generalization, we propose a new subsequence matching method, General Match. The earlier work by Faloutsos et al. (called FRM for convenience) causes a lot of false alarms due to lack of point-filtering effect. Dual Match, recently proposed as a dual approach of FRM, improves performance significantly over FRM by exploiting point filtering effect. However, it has the problem of having a smaller allowable window size---half that of FRM---given the minimum query length. A smaller window increases false alarms due to window size effect. General Match offers advantages of both methods: it can reduce window size effect by using large windows like FRM and, at the same time, can exploit point-filtering effect like Dual Match. General Match divides data sequences into generalized sliding windows (J-sliding windows) and the query sequence into generalized disjoint windows (J-disjoint windows). We formally prove that General Match is correct, i.e., it incurs no false dismissal. We then propose a method of estimating the optimal value of the sliding factor J that minimizes the number of page accesses. Experimental results for real stock data show that, for low selectivities (10-6¡«10-4), General Match improves average performance by 117% over Dual Match and by 998% over FRM; for high selectivities (10-3¡«10-1), by 45% over Dual Match and by 64% over FRM. The proposed generalization provides an excellent theoretical basis for understanding the underlying mechanisms of subsequence matching."
"XML is popular for data exchange and data publishing on the Web, but it comes with errors and inconsistencies inherent to real-world data. Hence, there is a need for XML data cleansing, which requires solutions for fuzzy duplicate detection in XML. The hierarchical and semi-structured nature of XML strongly difiers from the ¡Þat and structured relational model, which has received the main attention in duplicate detection so far. We consider four major challenges of XML duplicate detection to develop efiective, e©\cient, and scalable solutions to the problem."
"This second editionsystematically introduces the notion of ontologies to the non-expert reader and demonstrates in detail how to apply this conceptual framework for improved intranet retrieval of corporate information and knowledge and for enhanced Internet-based electronic commerce. He also describes ontology languages (XML, RDF, and OWL) and ontology tools, and the application of ontologies. In addition to structural improvements, the second edition covers recent developments relating to the Semantic Web, and emerging web-based standard languages."
"With the immense popularity of the Web, the world is witnessing an unprecedented demand for data services. At the same time, theInternet is evolving towards an information super-highway that incorporates a wide mixture of existing and emerging communication technologies, including wireless, mobile, and hybrid networking. Taking advantage of these new technologies, we are proposing a hybrid scheme which effectively combines broadcast for massive data dissemination and unicast for individual data delivery. In this paper;we describe a technique that uses the broadcast medium for storage of frequently requested data, and an algorithm that continuously adapts the broadcast content to match the hot-spot of the database. We show that the hot-spot can be accurately obtained by monitoring the ¡°broadcast misses¡± observed through direct requests. This is a departure from other broadcast-based systems which rely on efficient scheduling based on precompiled ¡®user profiles. We also show that the proposed scheme performs effectively even under very dynamic and rapidly changing workloads. Extensive simulation results demonstrate both the scalability and versatility of the technique."
"Two new spatial join operations, distance join and distance semi-join, are introduced where the join output is ordered by the distance between the spatial attribute values of the joined tuples. Incremental algorithms are presented for computing these operations, which can be used in a pipelined fashion, thereby obviating the need to wait for their completion when only a few tuples are needed. The algorithms can be used with a large class of hierarchical spatial data structures and arbitrary spatial data types in any dimensions. In addition, any distance metric may be employed. A performance study using R-trees shows that the incremental algorithms outperform non-incremental approaches by an order of magnitude if only a small part of the result is needed, while the penalty, if any, for the incremental processing is modest if the entire join result is required."
"This paper presents a region splitting strategy for physical database design of multidimensional file organizations. Physical database design is the process of determining the optimal configuration of physical files for a given set of queries. Recently, many multidimensional file organizations for supporting multiattribute access have been proposed in the literature. However, there has been no effort for their physical database design. We first show that the performance of query processing is highly affected by the similarity between the shapes of query regions and page regions in the domain space, and then propose a new region splitting strategy that finds the optimal configuration of the multidimensional file by controlling the interval ratio of different axes to achieve the similarity. We also present the results of extensive experiments using the multilevel grid file (MLGF), a multidimensional file organization, and various types of *Currently with Korea Telecom, Seoul, Korea Pwmission to copy without fee all or part of this material is granted provided that the copies are not made OT distributed for direct commercial advantage, the VLDB copyright notice and the title oj the publication and its date appear, and notice is given that copying is by permission of the Very Large Data Base Endowment. To copy otherwise, OT to republish, requkes a fee and/or special permission from the Endowment. Proceedings of the 23rd VLDB Conference Athens, Greece, 1997 queries and record distributions. The results indicate that our proposed strategy builds optimal MLGFs regardless of query types and record distributions. When the interval ratio of a two-dimensional query region is 1:1024, the performance of the proposed strategy is enhanced by as much as 7.5 times over that of the conventional cyclic splitting strategy. The performance is further enhanced for the query types having higher interval ratios. The result is significant since interval ratios can be far from 1:l for many practical applications, especially when different axes have different domains."
"For many years now, the SQL standard has been maintained and enhanced by NCITS Technical Committee H2 on Database in the US and by the ISO/IEC JTC 1/SC32/WG3 Database Languages Working Group internationally. After the publication of SQL:1992, the groups began to publish SQL as a base document (SQL/Foundation) and a number of independent parts. These parts began with SQL/CLI (Call-Level Interface) and SQL/PSM (Persistent Stored Modules) in 1995 and 1996, respectively. Interest in XML has been growing in the last several years among software vendors, user companies of all sizes, and within the standards community. NCITS H2 and SC32 both approved a project for a new part of SQL, part 14, XML-Related Specifications (SQL/XML), in the second half of 2000. After this new project was approved, a small number of companies began to meet in order to explore the technology and develop proposals to begin fleshing out this new part of SQL. This informal group of companies has come to be known as The SQLX Group. In roughly a year¡¯s time, several pieces of what might be termed ¡°infrastructure¡± have been progressed and are included in the initial working draft of SQL/XML [2]."
"Publisher Summary Electronic commerce applications have posed new challenges for database systems. Electronic commerce applications such as portals, marketplaces, and online stores (Amazon.com, eBay.com), are often faced with the problem of quickly integrating new catalogs from different sources into their existing catalog (the ¡°master¡± catalog). Electronic commerce applications have made it imperative for databases to support direct querying of database content from the web. However, the most popular Web interface is the Google-style search box, and queries submitted from such an interface may include neither attribute names nor units."
"HTTPHypertext Transfer Protocolrequests, Java virtual machines embedded in Web browsers to run applets, or remote procedure call protocols), researchers and practitioners alike are coming to realize that any technology for information services should tackle head-on the problem of semantic interoperability, i.e. the capability of an application to exchange data and activate data manipulation functions by utilizing its domain model. Therefore, architecture for information services should first and foremost handle the semantic issues in providing information services. Within this architecture, tools for semantic understanding of heterogeneous, distributed, and autonomously evolving data sources should be developed in order to provide a transparent representation of the domain regardless of the underlying data sources."
"Remote sensing provides the basic data to undertake inventory of land, as well as the temporal information required to monitor sustainable land management practices. In this paper, the current use of remote sensing for sustainable land management is reviewed, and the potential of future (new) satellite systems to contribute to sustainable development is explored. Other elements for successful sustainable development (ie, good policy and participatory approaches) are then compared and contrasted with information requirements. Sustainable land management refers to the activities of humans and implies that activity will continue in perpetuity. It is a term which attempts to balance the often conflicting ideals of economic growth and maintaining environmental quality and viability. Economic activities may range from intensive agriculture to the management of natural areas. It is argued that in order to effectively ¡°manage¡± resources, three elements must be present. These are information about natural resources, clear policies on how the resource may be managed (eg, Acts of Government, policy papers, administrative procedures), and participation of everyone (including local people) with an interest or ¡°stake¡± in the land. In this paper, we concentrate on methods to generate information about the resources, with an emphasis on how recent innovations in remote sensing fit with sustainable land management methods. In particular, we assess how resources may be inventoried by remote sensing, and techniques and data which may ascertain whether the activity is indeed sustainable. A concluding section discusses how the information (generated from remote sensing) is linked to policy and local participation. Thus, three specific questions are addressed. First, what cover is present? This question requires that remote sensing provides information on land cover as well as terrain attributes such as slope, aspect and terrain position. The second question addresses whether the use (management) of the cover is sustainable. This question requires temporal data collection to monitor whether the environment is degrading or otherwise changing. The third question is: How can remote sensing and GIS contribute to the policy tools of generating policy, providing information and ensuring participation by all stakeholders?"
"LeSelect is a mediator system which allows scientists to publish their resources (data and programs) so they can be transparently accessed. The scientists can typically issue queries which access distributed published data and involve the execution of expensive functions (corresponding to programs). Furthermore, the queries can involve large objects, such as images (e.g. archived meteorological satellite data). In this context, the costs of transmitting large objects and invoking expensive functions are the dominant factors of execution time. In this paper, we first propose three query execution techniques which minimize these costs by taking full advantage of the distributed architecture of mediator systems like LeSelect. Then we devise parallel processing strategies for queries including expensive functions. Based on experimentation, we show that it is hard to predict the optimal execution order when dealing with several functions. We propose a new hybrid parallel technique to solve this problem and give some experimental results."
"The ubiquitous usage of databases for managing structured data, compounded with the expanded reach of the Internet to end users, has brought forward new scenarios of data retrieval. Users often want to express non-traditional fuzzy queries with soft criteria, in contrast to Boolean queries, and to explore what choices are available in databases and how they match the query criteria. Conventional database management systems (DBMS s) have become increasingly inadequate for such new scenarios.  Towards enabling data retrieval, this thesis first studies how to fundamentally integrate ranking into databases. We built RankSQL, a DBMS that provides systematic and principled support of ranking queries. With a new ranking algebra and an extended query optimizer for the algebra, RankSQL captures ranking as a first-class construct in databases, together with traditional Boolean constructs. We invented efficient techniques for answering ad-hoc ranking aggregate queries. RankSQL provides significant performance improvement over current DBMSs in processing ranking queries and ranking aggregate queries.  This thesis further studies how to enable retrieval mechanisms beyond just ranking. Our explorative study in this direction is exemplified by two novel proposals¡ªOne is to integrate clustering and ranking of database query results; the other is to support inverse ranking queries that provide ranks of objects in query context. Injecting such non-traditional facilities into databases presents non-trivial challenges in both defining query semantics and designing query processing methods. We extended SQL language to express such queries and invented partition- and summary-driven approaches to process them."
"Web repositories, such as the Stanford WebBase repository, manage large heterogeneous collections of Web pages and associated indexes. For effective analysis and mining, these repositories must provide a declarative query interface that supports complex expressive Web queries. Such queries have two key characteristics: (i) They view a Web repository simultaneously as a collection of text documents, as a navigable directed graph, and as a set of relational tables storing properties of Web pages (length, URL, title, etc.). (ii) The queries employ application-specific ranking and ordering relationships over pages and links to filter out and retrieve only the ""best"" query results. In this paper, we model a Web repository in terms of ""Web relations"" and describe an algebra for expressing complex Web queries. Our algebra extends traditional relational operators as well as graph navigation operators to uniformly handle plain, ranked, and ordered Web relations. In addition, we present an overview of the cost-based optimizer and execution engine that we have developed, to efficiently execute Web queries over large repositories."
"The Indian Institute of Technology, Bombay is one of the leading universities in India. Located in Powai, a suburb of the vibrant city of Bombay (which is soon to revert to its original name, Mumbai), it is a scenic campus extending over 500 acres on the shores of Lake Powai. The institute has a faculty strength of about 400, and has about 2500 students. The Department of Computer Science has a faculty strength of 25, and around 150 undergraduate and 70 postgraduate students. The Database Group in the Department of Computer Science and Engineering is the largest database group in India. The group currently has four faculty members, D. B. Phatak, N. L. Sarda, S. Seshadri and S. Sudarshan. The group also currently has three research scholars, ten Masters students, ten undergraduate students and nine project engineers."
"Traditional methods of allocating resources for a DataBase Management System (DBMS) include the manual determination and allocation of each resource. Database resources are commonly tuned to achieve peak performance for a workload that is well-known and predictable. As databases become more commonly used in embedded systems and on the Internet, it is impossible to predict the workload that the DBMS will have to handle. From On-Line Transaction Processing (OLTP) to OnLine Analytical Processing (OLAP), DBMSs must be able to provide peak performance for not only different types of workloads, but multiple workloads on a single system. There is a clear need for a system that can determine what resource is causing poor performance and how to fix the problem."
"In the last few years, many active database models have been proposed. Some of them have been implemented as research prototypes. The use and study of these prototypes shows that it is difficult to get a clear idea of the proposed approaches and to compare them. More generally there are some unquestionable difficulties in understanding, reasoning about and teaching behavior of active database systems. We think there is a need for formal descriptions of the semantics of such systems in order to describe and to understand them with less ambiguities, to compare them and to come up with some progress in defining standard concepts and functionalities for active databases."
"Many societal applications, for example, in domains such as health care, land use, disaster management, and environmental monitoring, increasingly rely on geographical information for their decision making. With the emergence of the World WideWeb this information is typically located in multiple, distributed, diverse, and autonomously maintained systems. Therefore, strategic decision making in these societal applications relies on the ability to enrich the semantics associated to geographical information in order to support a wide variety of tasks including data integration, interoperability, knowledge reuse, knowledge acquisition, knowledge management, spatial reasoning, and many others. While all research realized in the area of the Semantic Web provides a foundation for annotating information resources with machine-readable meaning, much work must still be done to elicit semantics of geographical information. "
"To ensure high data quality, data warehouses must validate and cleanse incoming data tuples from external sources. In many situations, clean tuples must match acceptable tuples in reference tables. For example, product name and description fields in a sales record from a distributor must match the pre-recorded name and description fields in a product reference relation.A significant challenge in such a scenario is to implement an efficient and accurate fuzzy match operation that can effectively clean an incoming tuple if it fails to match exactly with any tuple in the reference relation. In this paper, we propose a new similarity function which overcomes limitations of commonly used similarity functions, and develop an efficient fuzzy match algorithm. We demonstrate the effectiveness of our techniques by evaluating them on real datasets."
"For the past few decades, there has been a significant interest in data integration, and lots of work has been introduced in this field. Herein we discussed a way to handle the problem of integrating heterogeneous data model, namely relational and XML. Since the relational model is the most data model used to manage data for years. Similarly, XML is rapidly becoming more and more popular as a standard format for exchanging information. In such way, building a sort of connection bridging these two models is clearly a need. To this point, we aim to define a system to extract data regardless of the nature of their model and make one query enough to retrieve data from different models, which are XML and relational in our case."
"This second Long Range Planning special issue on PLS-SEMin strategic management research and practice seeks to further progress towards this goal. The journal received 41 articles for its special issue on PLS-SEM, twelve of which completed a thorough review process successfully. Based on the number of high quality manuscripts, a decision was made to split the special issue. "
"Customer retention¡± is an important real-world problem in many sales and services related industries today. This work illustrates how we can integrate the various techniques of data-mining, such as decision-tree induction, deviation analysis and multiple concept-level association rules to form an intuitive and novel approach to gauging customer's loyalty and predicting their likelihood of defection. Immediate action taken against these ¡°early-warnings¡± is often the key to the eventual retention or loss of the customers involved."
"Automatically selecting an appropriate set of materialized views and indexes for SQL databases is a non-trivial task. A judicious choice must be cost-driven and influenced by the workload experienced by the system. Although there has been work in materialized view selection in the context of multidimensional (OLAP) databases, no past work has looked at the problem of building an industry-strength tool for automated selection of materialized views and indexes for SQL workloads. In this paper, we present an end-to-end solution to the problem of selecting materialized views and indexes. We describe results of extensive experimental evaluation that demonstrate the effectiveness of our techniques. Our solution is implemented as part of a tuning wizard that ships with Microsoft SQL Server 2000."
"Relational databases provide the ability to store user-defined functions and predicates which can be invoked in SQL queries. When evaluation of a user-defined predicate is relatively expensive, the traditional method of evaluating predicates as early as possible is no longer a sound heuristic. There are two previous approaches for optimizing such queries. However, neither is able to guarantee the optimal plan over the desired execution space. We present efficient techniques that are able to guarantee the choice of an optimal plan over the desired execution space. The optimization algorithm with complete rank-ordering improves upon the naive optimization algorithm by exploiting the nature of the cost formulas for join methods and is polynomial in the number of user-defined predicates (for a given number of relations.) We also propose pruning rules that significantly reduce the cost of searching the execution space for both the naive algorithm as well as for the optimization algorithm with complete rank-ordering, without compromising optimality. We also propose a conservative local heuristic that is simpler and has low optimization overhead. Although it is not always guaranteed to find the optimal plans, it produces close to optimal plans in most cases. "
"In this article metadata for mulimedia documents are classified in conformity with their nature, and the different kinds of metadata are brought into relation with the different purposes intended. We describe how metadata may be organized in accordance with the ISO standards SGML, which facilitates the handling of structured documents, and DFR, which supports the storage of collections of documents. Finally, we outline the impact of our observations on future developments."
"A multimedia database is a controlled collection of multimedia data items such as text, images, graphic objects, video and audio. A multimedia database management system (DBMS) provides support for the creation, storage, access, querying and control of a multimedia database. The requirements of a multimedia DBMS are: multimedia data modeling; multimedia object storage; multimedia indexing, retrieval and browsing; and multimedia query support. This paper discusses a general framework for multimedia database systems and describes the requirements and architecture for these systems."
"Conventional data warehouses employ the query-at-a-time model, which maps each query to a distinct physical plan. When several queries execute concurrently, this model introduces contention, because the physical plans---unaware of each other---compete for access to the underlying I/O and computation resources. As a result, while modern systems can efficiently optimize and evaluate a single complex data analysis query, their performance suffers significantly when multiple complex queries run at the same time.    We describe an augmentation of traditional query engines that improves join throughput in large-scale concurrent data warehouses. In contrast to the conventional query-at-a-time model, our approach employs a single physical plan that can share I/O, computation, and tuple storage across all in-flight join queries. We use an ""always-on"" pipeline of non-blocking operators, coupled with a controller that continuously examines the current query mix and performs run-time optimizations. Our design allows the query engine to scale gracefully to large data sets, provide predictable execution times, and reduce contention. In our empirical evaluation, we found that our prototype outperforms conventional commercial systems by an order of magnitude for tens to hundreds of concurrent queries."
"Editor's note: For this issue's ""From the Editors,"" I invited Robert Gephart of the University of Al-berta to reflect on his observations as a long-serving , award-winning reviewer of qualitative research for A!vII Over the past two and a half years, I have developed a tremendous respect for Bob's keen eye for evaluating qualitative research submissions , and great admiration for the painstaking advice he provides authors about how to improve their work. As a world-renowned qualitative author himself, Bob is in an excellent position to provide observations about how authors might increase the chances of having their qualitative research accepted for publication at AMI In a three-way electronic mail conversation about the challenges and opportunities of qualitative research , Bob, Tom Lee, and I all concluded that many authors with potentially very interesting data sets don't seem to know how to analyze them to their full potential. This is perhaps not surprising, gi ven the clear predominance of quantitative methods and statistics courses over qualitative ones, particularly in North America, as well as the inherently greater subjectivity involved in designing and analyzing qualitative research. As such, we encouraged Bob to provide a bit of a minitutorial-complete with reference citations and examples of high-quality papers that use particular qualitative approaches-in addition to his observations about qualitative research submitted to AMI The result is a longer-than-usual ""From the Edi-tors"" column. but one that we believe is well worth the extra reading time for anyone interested in producing , reviewing, or attempting to coax greater insights from qualitative research. We are fortunate to have someone with Bob's expertise share his observations, and we hope that his thoughts will prove useful to researchers for many years to come. "
"Resume. Un extranet permet a une organisation de partager une partie de son systeme d'information (documents, services, ordinateurs, etc.) de maniere securisee sur l'Internet. La securite est cruciale mais ne doit en rien gener l'etablissement de relations commerciales. Cet article examine comment concevoir un tel extranet. Il presente une solution automatisant la definition et la mise en oeuvre du controle d'acces ainsi que l'administration a grande echelle des utilisateurs en utilisant un modele a base de capacites. L'article decrit un prototype utilisant une infrastructure SPKI et offrant une authentification forte grace aux cartes a puce."
"We consider wireless broadcasting of data as a way of disseminating information to a massive number of users. Organizing and accessing information on wireless communication channels is different from the problem of organizing and accessing data on the disk. We describe two methods, (1,m) Indexing and Distributed Indexing, for organizing and accessing broadcast data. We demonstrate that the proposed algorithms lead to significant improvement of battery life, while retaining a low access time. "
"The key issue in performing spatial joins is finding the pairs of intersecting rectangles. For unindexed data sets, this is usually resolved by partitioning the data and then performing a plane sweep on the individual partitions. The resulting join can be viewed as a two-step process where the partition corresponds to a hash-based join while the plane-sweep corresponds to a sort-merge join. In this article, we look at extending the idea of the sort-merge join for one-dimensional data to multiple dimensions and introduce the Iterative Spatial Join. As with the sort-merge join, the Iterative Spatial Join is best suited to cases where the data is already sorted. However, as we show in the experiments, the Iterative Spatial Join performs well when internal memory is limited, compared to the partitioning methods. This suggests that the Iterative Spatial Join would be useful for very large data sets or in situations where internal memory is a shared resource and is therefore limited, such as with today's database engines which share internal memory amongst several queries. Furthermore, the performance of the Iterative Spatial Join is predictable and has no parameters which need to be tuned, unlike other algorithms. The Iterative Spatial Join is based on a plane sweep algorithm, which requires the entire data set to fit in internal memory. When internal memory overflows, the Iterative Spatial Join simply makes additional passes on the data, thereby exhibiting only a gradual performance degradation. "
"As teachers, if we believe content knowledge matters the most for successful instruction, we may not understand that getting to know students and discovering their strengths as learners are equally important. Teachers are instructional islands with a lot of content to share but perhaps unconnected to the learners that make up the classroom. If as teachers, we describe students by saying, ¡°she is a math wizard,¡± ¡°she is a science ace,¡± or ¡°he is a sponge for historical facts,¡± we can communicate a lot about students with minimal language. These metaphors help us make comparisons that evoke multiple layers of meaning, and yet thinking metaphorically is also an aspect of everyday life. Cognitive scientists Lakoff and Johnson (2008) argued that our conceptualizations of the world around us are metaphorical and provided examples of metaphors such as ¡°time is money¡± and suggested that the way we construe argument is conceived in metaphors of war when we ¡°attack a position,¡± for example, to support a philosophical claim. From an educational philosophy perspective, Greene contended learning is a landscape (1973) and teachers are philosophers working to help learners resist the forces that limit and oppress them (1988) to attain freedom to think for themselves. These theorists recognized the epistemological power of metaphor and challenged us to see its educational potential. Comparisons through metaphoric thinking afford different perspectives and open imaginative possibilities, challenging us to see familiar relationships in new ways. Metaphors can push us to think about teacher education differently as well and move beyond familiar views of clinical experiences, teacher interns, teacher preparation programs, and who we are as educators to see these concepts more complexly. The pedagogical innovation study and six empirical studies in this issue evoke metaphors of exploration, dialogue, windows, building, partnering, and innovating to inform and complicate our understanding teacher education. "
"XML is quickly becoming the de facto standard for data exchange over the Internet. This is creating a new set of data management requirements involving XML, such as the need to store and query XML documents. Researchers have proposed using relational database systems to satisfy these requirements by devising ways to ""shred"" XML documents into relations, and translate XML queries into SQL queries over these relations. However, a key issue with such an approach, which has largely been ignored in the research literature, is how (and whether) the ordered XML data model can be efficiently supported by the unordered relational data model. This paper shows that XML's ordered data model can indeed be efficiently supported by a relational database system. This is accomplished by encoding order as a data value. We propose three order encoding methods that can be used to represent XML order in the relational data model, and also propose algorithms for translating ordered XPath expressions into SQL using these encoding methods. Finally, we report the results of an experimental study that investigates the performance of the proposed order encoding methods on a workload of ordered XML queries and updates."
"SHORE (Scalable Heterogeneous Object REpository) is a persistent object system under development at the University of Wisconsin. SHORE represents a merger of object-oriented database and file system technologies. In this paper we give the goals and motivation for SHORE, and describe how SHORE provides features of both technologies. We also describe some novel aspects of the SHORE architecture, including a symmetric peer-to-peer server architecture, server customization through an extensible value-added server facility, and support for scalability on multiprocessor systems. An initial version of SHORE is already operational, and we expect a release of Version 1 in mid-1994."
"In this White Paper, produced as a result of discussions at the OOPSLA 2002 Workshop on Agent-Oriented Methodologies, we outline the current state of play of agent-oriented methodologies, how they might be integrated into an underlying, metamodel-based framework, and what the research community needs to do to make their products acceptable to industry. We conclude with an invitation to the community."
"Research in data stream algorithms has blossomed since late 90s. The talk will trace the history of the Approximate Frequency Counts paper, how it was conceptualized and how it influenced data stream research. The talk will also touch upon a recent development: analysis of personal data streams for improving our quality of lives."
"Extended transaction models have drawn much interest recently in academia and industry [2]. Such models seek to address the limitations of traditional ACID transactions for supporting multisystem applications that operate in heterogeneous environments. Such applications are increasingly proving to be of strategic importance to a number of businesses and governmental agencies. Different transaction models, however, tend to be closed in that they cannot be easily combined with other such models, thus limiting their applicability to situations which exactly match one of them. We do not propose yet another transaction model. Instead, we have developed a general specification facility that enables the formalization of any transaction model that can be stated in terms of dependencies amongst significant events in different subtransactions. Such significant events include start, commit, and abort. We make no assumptions that these are the only kinds of events. Our approach is viable because most extended transaction models can be naturally formalized in terms of dependencies among different subtransactions."
"This report is a summary of the First International Workshop on Active and Real-Time Database Systems (ARTDB-95), held at the University of Skovde in June 1995. "
"Traditionally, a record projection is compiled when all fields of the record are known in advance. The need to know all fields in advance leads to very clumsy programs, especially for querying external data sources. In a paper that had not been widely circulated in the database community, Remy presented in programming language context a constant-time implementation of the record projection operation that does not have such a requirement. This paper introduces his technique and suggests an improvement to his technique in the context of database queries. "
"Water has an outstanding importance for the life on earth. From this results the necessity for the monitoring and interpretation of mari ne data. For that, the visual analysis is a suitable and effective tool, whereby special demands arise from the heterogeneity of data (different data type s, different data sources), the quality of data (missing values, incorrect values ), and the large quantity of data. The visualization of marine data is particularly import ant within both their geographic context and their temporal course. First, this paper introduces a classification for the visualization of spatial and ti me related data, which is not only appropriate for marine data. Following special visual ization and interaction techniques for marine data are discussed. Thereby we do not raise the claim, to create new visualization paradigms. Rather we want to show solution concepts and special methods using well known paradigms for a special and complex application area, but also to address limits of the visualization paradigms in these applications."
"A set containment join is a join between set-valued attributes of two relations, whose join condition is specified using the subset (?) operator. Set containment joins are deployed in many database applications, even those that do not support set-valued attributes. In this article, we propose two novel partitioning algorithms, called the Adaptive Pick-and-Sweep Join (APSJ) and the Adaptive Divide-and-Conquer Join (ADCJ), which allow computing set containment joins efficiently. We show that APSJ outperforms previously suggested algorithms for many data sets, often by an order of magnitude. We present a detailed analysis of the algorithms and study their performance on real and synthetic data using an implemented testbed."
"Research and development of multidatabase systems was triggered by the need to integrate data from heterogeneous and physically distributed information sources Issues on multidatabase architectures and semantic heterogeneity have been explored. This paper presents the multidatabase systems done and currently being done at De La Salle University. These research projects focus on multidatabase architectures, and on identifying methods in resolving various forms of schema conflicts."
"In this paper, we present our research on defining a correct semantics for a class of update rule (UR) programs, and discuss implemanting these programs in a DBMS environment. Update rules execute by updating relations in a database which may cause the further execution of rules. A correct semantics must guarantee that the execution of the rules will terminate and that it will produce a minimal updated database. The class of UR programs is syntactically identified, based upon a concept that is similar to stratification. We extend that strict definition of stratification and allow a relaxed criterion for partitioning of the rules in the UR program. This relaxation allows a limited degree of nondeterminism in rule execution. We define an execution semantics based upon a monotonic fixpoint operator TUR, resulting in a set of fixpoints for UR. The monotionicity of the operator is maintained nby explicitly representing the effect of asserting and retracting tuples in the database. A declarative semantics for the update rule program is obtained by associating a normal logic program UR to represent the UR program. We use the stable model semantics which characterize a normal logic program by a set of minimal models which are called stable models. We show the equivalence between the set of fixpoints for UR and the set of stable models for UR. We briefly discuss implementing the fixpoint semantics of the UR program in a DBMS environment. Relations that can be updated by the rules are updatable relations and they are extended with two flags. An update rule is represented by a database query, which queries the updatable relations as well as database relaions, i.e., those relations which are not update by rules. We describe an algorithm to process the queries and compute a fixpoint in the DBMS environment and obtain a final database."
"Data warehouses collect large quantities of data from distributed sources into a single repository. A typical load to create or maintain a warehouse processes GBs of data, takes hours or even days to execute, and involves many complex and user-defined transformations of the data (e.g., find duplicates, resolve data inconsistencies, and add unique keys). If the load fails, a possible approach is to ¡°redo¡± the entire load. A better approach is to resume the incomplete load from where it was interrupted. Unfortunately, traditional algorithms for resuming the load either impose unacceptable overhead during normal operation, or rely on the specifics of transformations. We develop a resumption algorithm called DR that imposes no overhead and relies only on the high-level properties of the transformations. We show that DR can lead to a ten-fold reduction in resumption time by performing experiments using commercial software."
"s [41, 42]. academia [1932, 1926, 2267, 2275]. academic [1908, 2441]. acceleration [1869]. Access [2370, 13, 38, 1530, 1620, 1555, 2106, 1643, 1410, 602, 1672, 1033, 531, 601, 803, 1532, 1531, 949, 2204, 1455, 657, 598, 1263, 1086, 749, 409, 1969, 319, 2119, 450, 872, 1808, 171, 1559, 238, 821, 812, 1209, 1198, 694, 126, 1357, 883, 2139]. accesses [406]. Accessing [1295, 127, 515]. Accommodating [626]. account [1889]. accounting [679]. accrued [2385]. Accurate [276, 855]. achieve [858]. Achievements [1238, 619, 627]. ACID [1688]. ACM [38, 2139, 2216, 14, 2106, 2290, 2291, 42, 2239, 2445, 13, 2472, 2475, 2476, 2477, 2479, 2480, 1580, 1099, 2478, 2130, 2474, 1946, 1697, 2213, 2029, 2143, 2319, 2397, 2262]. ACM-SIGFIDET [38, 14]. Acquisition [288]. Across [1645, 2393, 1936]. ACT [1322]. ACT-NET [1322]. ACTA [586]. action [761]. Actions [1329]. activation [851]. Active [1322, 1239, 970, 833, 1471, 272, 1574, 1407, 1071, 1321, 1236, 1174, 420, 1171, 546, 1914, 1178, 1470, 766, 1098, 521, 1228, 1444, 1126, 1065]. Activities [136, 984, 216, 156, 1965, 587, 67, 748, 820]. activity [1311, 196]. Actual [211]. Ad [1394, 2001, 2056, 3]. ad-hoc [2001]. Ada [249, 458]. ADAM [1897]. adapt [2406]. Adaptable [1807]. adaptation [2113, 2328, 1209]. Adapting [1121, 254]. Adaptive [1730, 1675, 1002, 1642, 1024, 1826, 1112, 1737, 304, 1282, 307, 1809, 567]. ADBIS¡¯2001 [1931]. ADBMS [1321, 1322]. adding [463]. Addison [2043, 66]. Addison-Wesley [66]. Address [1148, 749, 1147, 642]. Addressing [1199]. ADEPT [1588]. Administering [221, 1303]. Administration [1478, 53]. Ado [1317]. ADO.NET [2236]. ADS [1071]. Advanced [1881, 952, 740, 1765, 2405, 1062, 678, 924, 1177]. Advancements [2105]. Advances [1227, 1931]. advantage [1163]. adventure [2310]. adversarial [2337]. Affiliation [2402]. after [1121]. again [1875]. against [471, 1939]. Agenda [1040]. Agent [1386, 1607, 2047, 1588, 1919, 1198, 2065]. Agent-Based [1386, 1607, 1588, 1198]."
"This paper presents, QuickStore, a memory-mapped storage system for persistent C++ built on top of the EXODUS Storage Manager. QuickStore provides fast access to in-memory objects by allowing application programs to access objects via normal virtual memory pointers. The paper also presents the results of a detailed performance study using the OO7 benchmark. The study compares the performance of QuickStore with the latest implementation of the E programming language. These systems exemplify the two basic approaches (hardware and software) that have been used to implement persistence in object-oriented database systems. Both systems use the same underlying storage manager and compiler allowing us to make a truly apples-to-apples comparison of the hardware and software techniques."
"Large organizations need to exchange information among many separately developed systems. In order for this exchange to be useful, the individual systems must agree on the meaning of their exchanged data. That is, the organization must ensure semantic interoperability. This paper provides a theory of semantic values as a unit of exchange that facilitates semantic interoperability betweeen heterogeneous information systems. We show how semantic values can either be stored explicitly or be defined by environments. A system architecture is presented that allows autonomous components to share semantic values. The key component in this architecture is called the context mediator, whose job is to identify and construct the semantic values being sent, to determine when the exchange is meaningful, and to convert the semantic values to the form required by the receiver. Our theory is then applied to the relational model. We provide an interpretation of standard SQL queries in which context conversions and manipulations are transparent to the user. We also introduce an extension of SQL, called Context-SQL (C-SQL), in which the context of a semantic value can be explicitly accessed and updated. Finally, we describe the implementation of a prototype context mediator for a relational C-SQL system."
"Tree Pattern Queries (TPQ), Branching Path Queries (BPQ), and Core XPath (CXPath) are subclasses of the XML query language XPath, TPQ ? BPQ ? CX Path ? X Path. Let TPQ = TPQ+ ? BPQ+ ? CX Path+ ? X Path+ denote the corresponding subclasses, consisting of queries that do not involve the boolean negation operator not in their predicates. Simulation and bisimulation are two different binary relations on graph vertices that have previously been studied in connection with some of these classes. For instance, TPQ queries can be minimized using simulation. Most relevantly, for an XML document, its bisimulation quotient is the smallest index that covers (i.e., can be used to answer) all BPQ queries. Our results are as follows: ? A CXPath+ query can be evaluated on an XML document by computing the simulation of the query tree by the document graph. ? For an XML document, its simulation quotient is the smallest covering index for BPQ+. This, together with the previously-known result stated above, leads to the following: For BPQ covering indexes of XML documents, Bisimulation - Simulation = Negation. ? For an XML document, its simulation quotient, with the idref edges ignored throughout, is the smallest covering index for TPQ.    For any XML document, its simulation quotient is never larger than its bisimulation quotient; in some instances, it is exponentially smaller. Our last two results show that disallowing negation in the queries could substantially reduce the size of the smallest covering index."
"This paper introduces a new approach to database disk buffering, called the LRU-K method. The basic idea of LRU-K is to keep track of the times of the last K references to popular database pages, using this information to statistically estimate the interarrival times of references on a page by page basis. Although the LRU-K approach performs optimal statistical inference under relatively standard assumptions, it is fairly simple and incurs little bookkeeping overhead. As we demonstrate with simulation experiments, the LRU-K algorithm surpasses conventional buffering algorithms in discriminating between frequently and infrequently referenced pages. In fact, LRU-K can approach the behavior of buffering algorithms in which page sets with known access frequencies are manually assigned to different buffer pools of specifically tuned sizes. Unlike such customized buffering algorithms however, the LRU-K method is self-tuning, and does not rely on external hints about workload characteristics. Furthermore, the LRU-K algorithm adapts in real time to changing patterns of access."
"In this paper we explore the problem of automatically adjusting DBMS multiprogramming levels and memory allocations in order to achieve a set of per-class msponse time goals for a complex multiclass wotkload. We start by describing the phenomena that make this a very challenging problem, the foremost of which is the interdependence between classes that results from their competition for shared tesources. We then describe M&M, a feedback-based algorithm for determining the MPL and memory settings for each class independently, and we evaluate the algorithm¡¯s effectiveness using a detailed simulation model. We show that our algorithm can successfully achieve response times that are within a few percent of the goals for mixed workloads consisting of shott transactions and longer-running ad hoc join queries."
"We describe the integration of a structured-text retrieval system (TextMachine) into an object-oriented database system (OpOur approach is a light-weight one, using the external function capability of the database system to encapsulate the text retrieval system as an external information source. Yet, we are able to provide a tight integration in the query language and processing; the user can access the text retrieval system using a standard database query language. The effcient and effective retrieval of structured text performed by the text retrieval system is seamlessly combined with the rich modeling and general-purpose querying capabilities of the database system, resulting in an integrated system with querying power beyond those of the underlying systems. The integrated system also provides uniform access to textual data in the text retrieval system and structured data in the database system, thereby achieving information fusion. We discuss the design and implementation of our prototype system, and address issues such as the proper framework for external integration, the modeling of complex categorization and structure hierarchies of documents (under automatic document schema impand techniques to reduce the performance overhead of accessing an external source."
"Efficient user-adaptable similarity search more and more increases in its importance for multimedia and spatial database systems. As a general similarity model for multi-dimensional vectors that is adaptable to application requirements and user preferences, we use quadratic form distance functions which have been successfully applied to color histograms in image databases [Fal+ 94]. The components aij of the matrix A denote similarity of the components i and j of the vectors. Beyond the Euclidean distance which produces spherical query ranges, the similarity distance defines a new query type, the ellipsoid query. We present new algorithms to efficiently support ellipsoid query processing for various user-defined similarity matrices on existing precomputed indexes. By adapting techniques for reducing the dimensionality and employing a multi-step query processing architecture, the method is extended to high-dimensional data spaces. In particular, from our algorithm to reduce the similarity matrix, we obtain the greatest lowerbounding similarity function thus guaranteeing no false drops. We implemented our algorithms in C++ and tested them on an image database containing 12,000 color histograms. The experiments demonstrate the flexibility of our method in conjunction with a high selectivity and efficiency."
"Abstract. With respect to the specific requirements of advanced OODB applications, index data structures for type hierarchies in OODBMS have to provide efficient support for multiattribute queries and have to allow index optimization for a particular query profile. We describe the multikey type index and an efficient implementation of this indexing scheme. It meets both requirements: in addition to its multiattribute query capabilities it is designed as a mediator between two standard design alternatives, key-grouping and type-grouping. A prerequisite for the multikey type index is a linearization algorithm which maps type hierarchies to linearly ordered attribute domains in such a way that each subhierarchy is represented by an interval of this domain. The algorithm extends previous results with respect to multiple inheritance. The subsequent evaluation of our proposal focuses on storage space overhead as well as on the number of disk I/O operations needed for query execution. The analytical results for the multikey type index are compared to previously published figures for well-known single-key search structures. The comparison clearly shows the superiority of the multikey type index for a large class of query profiles."
"This is a bibliography on active databases and active database systems which reflects the various research activities in this field. We compiled this bibliography for our own use, but hopefully it might be useful to other people as well. All papers that appear in the following list, are generally accessible.We do not claim that the bibliography is exhaustive and covers the complete range of literature that deals with activities. We decided to focus on central approaches, concepts, methods, and systems in the area of active databases. It does not contain entries in the area of ""pure"" real-time, object-oriented, temporal, and deductive databases. But we did include publications related to those approaches, as long as they discuss active databases.We divided the material into various sections following our own personal perception of the field. The sections provide an overview on different projects in the area of active databases, followed by sections on relevant research topics. Each section contains a few remarks followed by a list of cross references into the annotated bibliography. Papers might appear in more than one section in case they discuss different topics relevant to different sections.Additionally, when relevant we also included unpublished, but publicly available material. For those papers we included information how to obtain them from the authors or from the organizations where the were produced.The beauty of our work is the individual annotation to almost all publications. Due to space limitations we are forced to leave out those annotations in the version published here. For a complete annotated bibliography we refer to the entry in our WWW server.The effort to build up such a bibliography is an endless task. Since we believe it now provides a comprehensive overview on the existing literature in the field, we decided to publish it. However, we invite all readers to add remarks, corrections, updates, additions (including further annotations).Part of this work was done while we were associated with the FORWISS Institute of the Technical University of Munich. We would like to thank our student, Markus Blaschka, who compiled many references during his master's thesis."
"Deep pretrained transformer networks are effective at various ranking tasks, such as question answering and ad-hoc document ranking. However, their computational expenses deem them cost-prohibitive in practice. Our proposed approach, called PreTTR (Precomputing Transformer Term Representations), considerably reduces the query-time latency of deep transformer networks (up to a 42x speedup on web document ranking) making these networks more practical to use in a real-time ranking scenario. Specifically, we precompute part of the document term representations at indexing time (without a query), and merge them with the query representation at query time to compute the final ranking score. Due to the large size of the token representations, we also propose an effective approach to reduce the storage requirement by training a compression layer to match attention scores. Our compression technique reduces the storage required up to 95% and it can be applied without a substantial degradation in ranking performance."
"In recent years, the effect of the curse of high dimensionality has been studied in great detail on several problems such as clustering, nearest neighbor search, and indexing. In high dimensional space the data becomes sparse, and traditional indexing and algorithmic techniques fail from a efficiency and/or effectiveness perspective. Recent research results show that in high dimensional space, the concept of proximity, distance or nearest neighbor may not even be qualitatively meaningful. In this paper, we view the dimensionality curse from the point of view of the distance metrics which are used to measure the similarity between objects. We specifically examine the behavior of the commonly used L k norm and show that the problem of meaningfulness in high dimensionality is sensitive to the value of k. For example, this means that the Manhattan distance metric (L 1 norm) is consistently more preferable than the Euclidean distance metric (L 2 norm) for high dimensional data mining applications. Using the intuition derived from our analysis, we introduce and examine a natural extension of the L k norm to fractional distance metrics. We show that the fractional distance metric provides more meaningful results both from the theoretical and empirical perspective. The results show that fractional distance metrics can significantly improve the effectiveness of standard clustering algorithms such as the k-means algorithm."
"This document is a report on the workshop on Information Integration on the Web (IIWeb-03), held in Acapulco, Mexico, on August 9-10, as part of the 2003 International Joint Conference on Artificial Intelligence. The full proceedings of the workshop are available online [1]. A small sample of the papers presented at the workshop were also included in a special issue of IEEE Intelligent Systems [2]. Effective integration of heterogeneous databases and information sources has been cited as the most pressing challenge in spheres as diverse as corporate data management, homeland security, counter-terrorism and the human genome project. "
"Although the relational model for databases provides a great range of advantages over other data models, it lacks a comprehensive way to handle incomplete and uncertain data. Uncertainty in data values, however, is pervasive in all real-world environments and has received much attention in the literature. Several methods have been proposed for incorporating uncertain data into relational databases. However, the current approaches have many shortcomings and have not established an acceptable extension of the relational model. In this paper, we propose a consistent extension of the relational model. We present a revised relational structure and extend the relational algebra. The extended algebra is shown to be closed, a consistent extension of the conventional relational algebra, and reducible to the latter."
"Supporting independent ISs and integrating them in distributed data warehouses (materialized views) is becoming more important with the growth of the WWW. However, views defined over autonomous ISs are susceptible to schema changes. In the EVE project we are developing techniques to support the maintenance of data warehouses defined over distributed dynamic ISs. The EVE system is the first to allow views to survive schema changes of their underlying ISs while also adapting to changing data in those sources. EVE achieves this is two steps: applying view query rewriting algorithms that exploit information about alternative ISs and the information they contain, and incrementally adapting the view extent to the view definition changes. Those processes are referred to as view synchronization and view adaption, respectively. They increase the survivability of materialized views in changing environments and reduce the necessity of human interaction in system maintenance."
"Access methods based on signature files can largely benefit from possibilities offered by parallel environments. To this end, an effective declustering strategy that would distribute signatures over a set of parallel independent disks has to be combined with a synergic clustering which is employed to avoid searching the whole signature file while executing a query. This article proposes two parallel signature file organizations, Hamming Filter (HF+) and Hamming + Filter, whose common declustering strategy is based on error correcting codes, and where clustering is achieved by organizing signatures into fixed-size buckets, each containing signatures sharing the same key< value.  HF< allocates signatures on disks in a static way and works well if a correct relationship holds between the parameters of the code and the size of the file. H+F is a generalization of HF suitable to manage highly dynamic files. It uses a dynamic declustering, obtained through a sequence of codes, and organizes a smooth migration of signatures between disks so that high performance levels are retained regardless of current file size. Theoretical analysis characterizes the best-case, expected, and worst-case behaviors of these organizations. Analytical results are verified by experiments on prototype systems."
"We present a pipelining, dynamically user-controllable reorder operator, for use in data-intensive applications. Allowing the user to reorder the data delivery on the fly increases the interactivity in several contexts such as online aggregation and large-scale spreadsheets; it allows the user to control the processing of data by dynamically specifying preferences for different data items based on prior feedback, so that data of interest is prioritized for early processing. In this paper we describe an efficient, non-blocking mechanism for reordering, which can be used over arbitrary data streams from files, indexes, and continuous data feeds. We also investigate several policies for the reordering based on the performance goals of various typical applications. We present results from an implementation used in Online Aggregation in the Informix Dynamic Server with Universal Data Option, and in sorting and scrolling in a large-scale spreadsheet. Our experiments demonstrate that for a variety of data distributions and applications, reordering is responsive to dynamic preference changes, imposes minimal overheads in overall completion time, and provides dramatic improvements in the quality of the feedback over time. Surprisingly, preliminary experiments indicate that online reordering can also be useful in traditional batch query processing, because it can serve as a form of pipelined, approximate sorting."
"This paper examines the effect on product development of project scope: the extent to which a new product is based on unique parts developed in-house. Using data from a larger study of product development in the world auto industry, the paper presents evidence on the impact of scope on lead time and engineering productivity. Studies of the automotive supplier industry suggest that very different structures and relationships exist in Japan, the U.S., and Europe. Yet there has been little study of the impact of these differences on development performance. Further, little is known about the effects of different parts strategies (i.e. unique versus common or carryover parts) on development. The evidence presented here suggests that project scope differs significantly in the industry, even for comparable products. These differences in strategy, in turn, explain an important part of differences in performance. In particular, it appears that a distinctive approach to scope among Japanese firms---high levels of unique parts, intensive supplier involvement in engineering---accounts for a significant fraction of their advantage in lead time and cost."
"One of the features that distinguishes digital libraries from traditional databases is new cost models for client access to intellectual property. Clients will pay for accessing data items in digital libraries, and we believe that optimizing these costs will be as important as optimizing performance in traditional databases. In this article we discuss cost models and protocols for accessing digital libraries, with the objective of determining the minimum cost protocol for each model. We expect that in the future information appliances will come equipped with a cost optimizer, in the same way that computers today come with a built-in operating system. This article makes the initial steps towards a thery and practice of intellectual property cost management."
"Querying large numbers of data sources is gaining importance due to increasing numbers of independent data providers. One of the key challenges is executing queries on all relevant information sources in a scalable fashion and retrieving fresh results. The key to scalability is to send queries only to the relevant servers and avoid wasting resources on data sources which will not provide any results. Thus, a catalog service, which would determine the relevant data sources given a query, is an essential component in efficiently processing queries in a distributed environment. This paper proposes a catalog framework which is distributed across the data sources themselves and does not require any central infrastructure. As new data sources become available, they automatically become part of the catalog service infrastructure, which allows scalability to large numbers of nodes. Furthermore, we propose techniques for workload adaptability. Using simulation and real-world data we show that our approach is valid and can scale to thousands of data sources."
"Smartcard is the most secure and cheap portable computing device today. It has been used successfully around the world in various applications involving payment and identification, making it the world¡¯s highest-volume market for semiconductors in the year 2K. As smartcards become multi-application (by hosting a dedicated Java Virtual Machine) and more and more powerful (32 bit processor, more than 1MB of stable storage), the need for database management arises. Embedding database management (query processing, access rights, transaction control) in the card indeed simplifies and makes application code smaller and safer.The paper is organized as follows. Section 2 introduces the health card application which we will use for the demonstration. Section 3 presents the PicoDBMS design and implementation choices which are needed to understand the value of the demonstration. Section 4 presents the demonstration platform and discusses the way we validate our techniques."
"Mining frequent patterns in transaction databases, time-series databases, and many other kinds of databases has been studied popularly in data mining research. Most of the previous studies adopt an Apriori-like candidate set generation-and-test approach. However, candidate set generation is still costly, especially when there exist prolific patterns and/or long patterns. In this study, we propose a novel frequent pattern tree (FP-tree) structure, which is an extended prefix-tree structure for storing compressed, crucial information about frequent patterns, and develop an efficient FP-tree-based mining method, FP-growth, for mining the complete set of frequent patterns by pattern fragment growth. Efficiency of mining is achieved with three techniques: (1) a large database is compressed into a highly condensed, much smaller data structure, which avoids costly, repeated database scans, (2) our FP-tree-based mining adopts a pattern fragment growth method to avoid the costly generation of a large number of candidate sets, and (3) a partitioning-based, divide-and-conquer method is used to decompose the mining task into a set of smaller tasks for mining confined patterns in conditional databases, which dramatically reduces the search space. Our performance study shows that the FP-growth method is efficient and scalable for mining both long and short frequent patterns, and is about an order of magnitude faster than the Apriori algorithm and also faster than some recently reported new frequent pattern mining methods."
"In the late '70s, while second generation DBMS products and technologies were entering the market, there was significant research activity whose aim was to make greater use of semantic information in database systems. The focus of that research was primarily on semantic data models and data modelling, including semantic query processing and integrity checking. However, few if any of the results of these efforts found their way in database technologies of the day, or database management practices. Instead, semantic issues were delegated to early phases of information system development (including requirements analysis and design), as well as application development. Today's database system technologies perform admirably well with semantically trivial operations and representations. At the same time, these technologies are being challenged in virtually every area of data management, with new applications which demand ways of dealing more explicitly with the meaning of the data being managed. "
"A semistructured information space consists of multiple collections of textual documents containing fielded or tagged sections. The space can be highly heterogeneous, because each collection has its own schema, and there are no enforced keys or formats for data items across collections. Thus, structured methods like SQL cannot be easily employed, and users often must make do with only full-text search. In this paper, we describe an approach that provides structured querying for particular types of entities, such as companies and people. Entity-based retrieval is enabled by normalizing entity references in a heuristic, type-dependent manner. The approach can be used to retrieve documents and can also be used to construct entity profiles ¡ª summaries of commonly sought information about an entity based on the documents' content. The approach requires only a modest amount of meta-information about the source collections, much of which is derived automatically. "
"Data quality is a serious concern in any data-driven enterprise, often creating misleading findings during data mining, and causing process disruptions in operational databases. The manifestations of data quality problems can be very expensive- ""losing"" customers, ""misplacing"" billions of dollars worth of equipment, misallocated resources due to glitched forecasts, and so on. Solving data quality problems typically requires a very large investment of time and energy -- often 80% to 90% of a data analysis project is spent in making the data reliable enough that the results can be trusted.In this tutorial, we present a multi disciplinary approach to data quality problems. We start by discussing the meaning of data quality and the sources of data quality problems. We show how these problems can be addressed by a multidisciplinary approach, combining techniques from management science, statistics, database research, and metadata management. Next, we present an updated definition of data quality metrics, and illustrate their application with a case study. We conclude with a survey of recent database research that is relevant to data quality problems, and suggest directions for future research."
"Everyone knows the small-world phenomenon: soon after meeting a stranger, we are surprised to discover that we have a mutual friend, or we are connected through a short chain of acquaintances. In his book, Duncan Watts uses this intriguing phenomenon--colloquially called ""six degrees of separation""--as a prelude to a more general exploration: under what conditions can a small world arise in any kind of network?The networks of this story are everywhere: the brain is a network of neurons; organisations are people networks; the global economy is a network of national economies, which are networks of markets, which are in turn networks of interacting producers and consumers. Food webs, ecosystems, and the Internet can all be represented as networks, as can strategies for solving a problem, topics in a conversation, and even words in a language."
"EROC (Extensible, Reusable Optimization Components) is a toolkit for building query optimizers. EROC¡¯s components are C++ classes based on abstractions we have identified as central to query optimization, not only in relational DBMSs, but in extended relational and object-oriented DBMSs as well. I EROC¡¯s use of C++ classes clarifies the mapping from application domain (optimization) abstractions to solution domain (EROC) abstractions, and these classes provide: (1) complex predicate definition and manipulation; (2) representations for common operators, such as join and groupby, and associated property derivation functions, including key derivation; (3) management of catalog and type information; (4) implementations of common algebraic equivalence rules, and (5) System Rand Volcano-style search strategies. The classes are designed to provide optimizer implementors reusability and extensibility through layering and inheritance. EROC provides much more functionality than previous optimization tools because at1 of Pemnission to copy without fee all 01 part of this material is granted provided thaf the copies are not made OT distributed fOT¡¯ direct commercial advantage, EROC¡¯s optimization classes are extensible and reusable, not just the search components. In addition to describing EROC¡¯s architecture and software engineering, we also show how EROC¡¯s classes were extended to build NEAT0 (New EROC-based Advanced Teradata Optimizer), a join optimizer for a massively parallel environment. Based on the extensions required we give an indication of the savings EROC, provided us. To show NEATO¡¯s efficiency and effectiveness, we present results of optimizing complex TPC/D benchmark queries and show that NEAT0 easily searches the entire space of query execution plans. We outline plans for extensions to NEAT0 and overview how the flexibility of EROC will enable these extensions."
"Semantic mappings between data sources play a key role in several data sharing architectures. Mappings provide the relationships between data stored in different sources, and therefore enable answering queries that require data from other nodes in a data sharing network. Composing mappings is one of the core problems that lies at the heart of several optimization methods in data sharing networks, such as caching frequently traversed paths and redundancy analysis.    This paper investigates the theoretical underpinnings of mapping composition. We study the problem for a rich mapping language, GLAV, that combines the advantages of the known mapping formalisms globalas-view and local-as-view. We first show that even when composing two simple GLAV mappings, the full composition may be an infinite set of GLAV formulas. Second, we show that if we restrict the set of queries to be in CQk (a common restriction in practice), then we can always encode the infinite set of GLAV formulas using a finite representation. Furthermore, we describe an algorithm that given a query and a finite encoding of an infinite set of GLAV formulas, finds all the certain answers to the query. Consequently, we show that for a commonly occuring class of queries it is possible to pre-compose mappings, thereby potentially offering significant savings in query processing."
"An information retrieval (IR) engine can rank documents based on textual proximity of keywords within each document. In this paper we apply this notion to search across an entire database for objects that are ""near"" other relevant objects. Proximity search enables simple ""focusing"" queries based on general relationships among objects, helpful for interactive query sessions. We view the database as a graph, with data in vertices (objects) and relationships indicated by edges. Proximity is defined based on shortest paths between objects. We have implemented a prototype search engine that uses this model to enable keyword searches over databases, and we have found it very effective for quickly finding relevant information. Computing the distance between objects in a graph stored on disk can be very expensive. Hence, we show how to build compact indexes that allow us to quickly find the distance between objects at search time. Experiments show that our algorithms are effcient and scale well."
"Columbia University has a number of projects that touch on database systems issues. In this report, we describe the Columbia Fast Query Project (Section 2), the JAM project (Section 3), the CARDGIS project (Section 4), the Columbia Internet Information Searching Project (Section 5), the Columbia Content-Based Visual Query project (Section 6), and projects associated with Columbia¡¯s Programming Systems Laboratory (Section 7)."
"A fundamental serwce prowded by the products offered by various software vendors ESthat of managmg the persistent storage of apphcatlon data The characteristics and usage patterns of the data stored by various different applications varies widely: a storage service designed and tuned for one class of application may not serve another apphcatlon well ¡®fo a first approximation, two extremes in tlus spectrum of storage services required by apphcatlons are today prowded by relational databases and file systems."
"Most databases contain ¡°name constants¡± like course numbers, personal names, and place names that correspond to entities in the real world. Previous work in integration of heterogeneous databases has assumed that local name constants can be mapped into an appropriate global domain by normalization. Here we assume instead that the names are given in natural language text. We then propose a logic for database integration called WHIRL which reasons explicitly about the similarity of local names, as measured using the vector-space model commonly adopted in statistical information retrieval. An implemented data integration system based on WHIRL has been used to successfully integrate information from several dozen Web sites in two domains."
"Data warehouses store materialized views over base data from external sources. Clients typically perform complex read-only queries on the views. The views are refreshed periodically by maintenance transactions, which propagate large batch updates from the base tables. In current warehousing systems, maintenance transactions usually are isolated from client read activity, limiting availability and/or size of the warehouse. We describe an algorithm called 2VNL that allows warehouse maintenance transactions to run concurrently with readers. By logically maintaining two versions of the database, no locking is required and serializability is guaranteed. We present our algorithm, explain its relationship to other multi-version concurrency control algorithms, and describe how it can be implemented on top of a conventional relational DBMS using a query rewrite approach."
"Classification is an important data mining problem. Although classification is a wellstudied problem, most of the current classification algorithms require that all or a portion of the the entire dataset remain permanently in memory. This limits their suitability for mining over large databases. We present a new decision-tree-based classification algorithm, called SPRINT that removes all of the memory restrictions, and is fast and scalable. The algorithm has also been designed to be easily parallelized, allowing many processors to work together to build a single consistent model. This parallelization, also presented here, exhibits excellent scalability as well. The combination of these characteristics makes the proposed algorithm an ideal tool for data mining."
"Advances in hardware-related technologies promise to enable new data management applications that monitor continuous processes. In these applications, enormous amounts of state samples are obtained via sensors and are streamed to a database. Further, updates are very frequent and may exhibit locality. While the R-tree is the index of choice for multi-dimensional data with low dimensionality, and is thus relevant to these applications, R-tree updates are also relatively inefficient. We present a bottom-up update strategy for R-trees that generalizes existing update techniques and aims to improve update performance. It has different levels of reorganization--ranging from global to local--during updates, avoiding expensive top-down updates. A compact main-memory summary structure that allows direct access to the R-tree index nodes is used together with efficient bottom-up algorithms. Empirical studies indicate that the bottom-up strategy outperforms the traditional top-down technique, leads to indices with better query performance, achieves higher throughput, and is scalable."
"The information security strategic plan is necessarily comprehensive, including business processes, people, and physical infrastructure, as well as the information system. The Security risk evaluation needs the calculating asset value to predict the impact and consequence of security incidents. The return on security investment (ROSI) is defining the value for all invested in terms of security by determining the cost of assets that may disturb in security breaches and the cost of its impact. Knowledge is the source of many competitive advantages for businesses and it should protect against theft, misuse and disasters by adequate security controls. All elements that involved in the knowledge creation process are knowledge assets. An IPO model with a combination of Skandia and Balanced scorecard methods needs to develop a measurement system for knowledge asset value assessment. This model recognizes the role of customers and employees as the natures of knowledge and concentrates on a wide range of factors involved in organization such as processes, structures and development elements that has not been tried before. The model in addition includes structure capital variables that emphasized ICT factors those are investing knowledge into the company's competitive advantage."
"The Cornell Jaguar Project is exploring a variety of issues related to mobility and query processing. One broad theme is to break down the traditional client and server boundaries, leading to ubiquitous query processing. Another theme is to extend database and query processing techniques to small-scale and mobile devices. The project builds on and extends the Cornell PREDATOR database engine."
"Data management in a networked world presents us with some of the same challenges that we¡¯ve seen in the past, but emphasizes our ability to deal with scale, in that there are several orders of magnitude more database users, and database sizes are rising more quickly than Moore¡¯s law. We have considerably less control over the structure of the data than in the past and must efficiently operate over poorly or weakly specified schema."
"Temporal databases assume a single line of time evolution. In other words, they support timeevolving data. However there are applications which require the support of temporal data with branched time evolution. With new branches created as time proceeds, branched and temporal data tends to increase in size rapidly, making the need for e cient indexing crucial. We propose a new (paginated) access method for branched and temporal data: the BT-tree. The BT-tree is both storage e cient and access e cient. We have implemented the BT-tree and performance results con rm these properties."
"Enterprise-class databases require database administrators who are responsible for performance tuning. With large-scale deployment of databases, minimizing database administration function becomes important. One important task of a database administrator is selecting indexes that are appropriate for the workload on the system. In data intensive applications such as decision support and data warehousing picking the right set of indexes becomes crucial for performance. Moreover, the indexes chosen should track changes in the workload. While automating the process of index selection can greatly reduce administration cost, enterprise databases are simply too complex for the administrator to hit the ¡°accept¡± button on the recommendations of an index selection tool without doing a quantitative impact analysis of the recommendations."
"When we, humans, talk to each other we have no trouble disambiguating what another person means, although our statements are almost never meticulously specified down to very last detail. We ¡°fill in the gaps¡± using our common-sense knowledge about the world. We present a powerful mechanism that allows users of object-oriented database systems to specify certain types of ad-hoc queries in a manner closer to the way we pose questions to each other. Specifically, the system accepts as input queries with incomplete, and therefore ambiguous, path expressions. From them, it generates queries with fully-specified path expressions that are consistent with those given as input and capture what the user most likely meant by them. This is achieved by mapping the problem of path expression disambiguation to an optimal path computation (in the transitive closure sense) over a directed graph that represents the schema. Our method works by exploiting the semantics of the kinds of relationships in the schema and requires no special knowledge about the contents of the underlying database, i.e., it is domain independent. In a limited set of experiments with human subjects, the proposed mechanism was very successful in disambiguating incomplete path expressions."
"The National Technical University of Athens (NTUA) is the leading Technical University in Greece. The Computer Science Division of the Electrical and Computer Engineering Department covers several fields of practical, theoretical and technical computer science and is involved in several research projects supported by the EEC, the government and industrial companies. The Knowledge and Data Base Systems (KDBS) Laboratory was established in 1992 at the National Technical University of Athens. It is recognised internationally, evidenced by its participation as a central node in the Esprit Network of Excellence IDOMENEUS. The Information and Data on Open MEdia for NEtworks of USers, project aims to coordinate and improve European efforts in the development of next-generation information environments which will be capable of maintaining and communicating a largely extended class of information in an open set of media. The KDBS Laboratory employs one full-time research engineer and several graduate students. Its infrastructure includes a LAN with several DECstation 5000/200 and 5000/240 workstations, an HP Multimedia Workstation, several PCs and software for database and multimedia applications. The basic research interests of our Laboratory include: Spatial Database Systems, Multimedia Database Systems and Active Database Systems. Apart from the above database areas, interests of the KDBS Laboratory span several areas of Information Systems, such as Software Engineering Databases, Transactional Systems, Image Databases, Conceptual Modeling, Information System Development, Temporal Databases, Advanced Query Processing and Optimization Techniques.  The group's efforts on Spatial Database Systems, include the study of new data structures, storage techniques, retrieval mechanisms and user interfaces for large geographic data bases. In particular, we look at specialized, spatial data structures (R-Trees and their variations) which allow for the direct access of the data based on their spatial properties, and not some sort of encoded representation of the objects' coordinates. We study implementation and optimization techniques of spatial data structures and develop models that make performance estimation. Finally, we are investigating techniques for the efficient representation of relationships and reasoning in space. The activities on Multimedia Database Systems, include the study of advanced data models, storage techniques, retrieval mechanisms and user interfaces for large multimedia data bases. The data models under study include the object-oriented model and the relational model with appropriate extensions to support multimedia data. We are also investigating content-based search techniques for image data bases. In a different direction, we are studying issues involved in the development of multimedia front-ends for conventional, relational data base systems. In the area of Active Database Systems, we are developing new mechanisms for implementing triggers in relational databases. Among the issues involved, we address the problem of efficiently finding qualifying rules against updates in large sets of triggers. This problem is especially critical in database system implementations of triggers, where large amounts of data may have to be searched in order to find out if a particular trigger may qualify to run or not.  Continuing work that started at the Foundation for Research and Technology (FORTH), Institute of Computer Science, the group is investigating reuse-oriented approaches to information systems application development. "
"Publisher Summary  Traditional databases allow for the storage and retrieval of large amounts of data, but do not make any concessions for uncertainty in the data. In many domains, it is difficult, if not impossible, to state all information with 100% certainty. Scientific research, for example, is subject to a great deal of uncertainty and error that cannot be modeled by traditional database systems. Error-prone experimental machinery, polluted samples, and simple human error are a few of the many possible sources of this uncertainty. With the recent importance of the web, and the many textual (and HTML encoded) sources of information that it makes available, information extraction has become a hot area. The idea is to use natural language analysis tools to create structured representations of free-form text documents. This information extraction is an error-prone endeavor: even the best systems can only hope to be right part of the time."
"In the past decade, advances in speed of commodity CPUs have far out-paced advances in memory latency. Main-memory access is therefore increasingly a performance bottleneck for many computer applications, including database systems. In this article, we use a simple scan test to show the severe impact of this bottleneck. The insights gained are translated into guidelines for database architecture; in terms of both data structures and algorithms. We discuss how vertically fragmented data structures optimize cache performance on sequential data access. We then focus on equi-join, typically a random-access operation, and introduce radix algorithms for partitioned hash-join. The performance of these algorithms is quantied using a detailed analytical model that incorporates memory access cost. Experiments that validate this model were performed on the Monet database system. We obtained exact statistics on events like TLB misses, L1 and L2 cache misses, by using hardware performance counters found in modern CPUs. Using our cost model, we show how the carefully tuned memory access pattern of our radix algorithms make them perform well, which is conrmed by experimental results."
"Complex queries are becoming commonplace, with the growing use of decision support systems. These complex queries often have a lot of common sub-expressions, either within a single query, or across multiple such queries run as a batch. Multiquery optimization aims at exploiting common sub-expressions to reduce evaluation cost. Multi-query optimization has hither-to been viewed as impractical, since earlier algorithms were exhaustive, and explore a doubly exponential search space. In this paper we demonstrate that multi-query optimization using heuristics is practical, and provides significant benefits. We propose three cost-based heuristic algorithms: Volcano-SH and Volcano-RU, which are based on simple modifications to the Volcano search strategy, and a greedy heuristic. Our greedy heuristic incorporates novel optimizations that improve efficiency greatly. Our algorithms are designed to be easily added to existing optimizers. We present a performance study comparing the algorithms, using workloads consisting of queries from the TPC-D benchmark. The study shows that our algorithms provide significant benefits over traditional optimization, at a very acceptable overhead in optimization time."
"s [41, 42]. academia [1932, 1926, 2267, 2275]. academic [1908, 2441]. acceleration [1869]. Access [2370, 13, 38, 1530, 1620, 1555, 2106, 1643, 1410, 602, 1672, 1033, 531, 601, 803, 1532, 1531, 949, 2204, 1455, 657, 598, 1263, 1086, 749, 409, 1969, 319, 2119, 450, 872, 1808, 171, 1559, 238, 821, 812, 1209, 1198, 694, 126, 1357, 883, 2139]. accesses [406]. Accessing [1295, 127, 515]. Accommodating [626]. account [1889]. accounting [679]. accrued [2385]. Accurate [276, 855]. achieve [858]. Achievements [1238, 619, 627]. ACID [1688]. ACM [38, 2139, 2216, 14, 2106, 2290, 2291, 42, 2239, 2445, 13, 2472, 2475, 2476, 2477, 2479, 2480, 1580, 1099, 2478, 2130, 2474, 1946, 1697, 2213, 2029, 2143, 2319, 2397, 2262]. ACM-SIGFIDET [38, 14]. Acquisition [288]. Across [1645, 2393, 1936]. ACT [1322]. ACT-NET [1322]. ACTA [586]. action [761]. Actions [1329]. activation [851]. Active [1322, 1239, 970, 833, 1471, 272, 1574, 1407, 1071, 1321, 1236, 1174, 420, 1171, 546, 1914, 1178, 1470, 766, 1098, 521, 1228, 1444, 1126, 1065]. Activities [136, 984, 216, 156, 1965, 587, 67, 748, 820]. activity [1311, 196]. Actual [211]. Ad [1394, 2001, 2056, 3]. ad-hoc [2001]. Ada [249, 458]. ADAM [1897]. adapt [2406]. Adaptable [1807]. adaptation [2113, 2328, 1209]. Adapting [1121, 254]. Adaptive [1730, 1675, 1002, 1642, 1024, 1826, 1112, 1737, 304, 1282, 307, 1809, 567]. ADBIS¡¯2001 [1931]. ADBMS [1321, 1322]. adding [463]. Addison [2043, 66]. Addison-Wesley [66]. Address [1148, 749, 1147, 642]. Addressing [1199]. ADEPT [1588]. Administering [221, 1303]. Administration [1478, 53]. Ado [1317]. ADO.NET [2236]. ADS [1071]. Advanced [1881, 952, 740, 1765, 2405, 1062, 678, 924, 1177]. Advancements [2105]. Advances [1227, 1931]. advantage [1163]. adventure [2310]. adversarial [2337]. Affiliation [2402]. after [1121]. again [1875]. against [471, 1939]. Agenda [1040]. Agent [1386, 1607, 2047, 1588, 1919, 1198, 2065]. Agent-Based [1386, 1607, 1588, 1198]."
"This paper presents a distributed file organization for record-structured, disk-resident files with key-based exact-match access. The file is organized into buckets that are spread across multiple servers, where a server may hold multiple buckets. Client requests are serviced by mapping keys onto buckets and looking up the corresponding server in an address table. Dynamic growth in terms of file size and access load is supported by bucket splits and migration onto other existing or newly acquired servers. The significant and challenging problem addressed here is how to achieve scalability so that both the file size and the client throughput can be scaled up by linearly increasing the number of servers and dynamically redistributing data. Unlike previous work with similar objectives, our data redistribution considers explicitly the cost/performance ratio of the system by aiming to minimize the number of servers that are acquired to provide the required performance. A new server is acquired only if the overall server utilization in the system does not drop below a specified threshold. Preliminary simulation results show that the goal of scalability with controlled cost/performance is indeed achieved to a large extent."
"A major problem in today's information-driven world is that sharing heterogeneous, semantically rich data is incredibly difficult. Piazza is a peer data management system that enables sharing heterogeneous data in a distributed and scalable way. Piazza assumes the participants to be interested in sharing data, and willing to define pairwise mappings between their schemas. Then, users formulate queries over their preferred schema, and a query answering system expands recursively any mappings relevant to the query, retrieving data from other peers. In this paper, we provide a brief overview of the Piazza project including our work on developing mapping languages and query reformulation algorithms, assisting the users in defining mappings, indexing, and enforcing access control over shared data."
Microsoft Universal Data Access defines a platform for developing multi-tier enterprise applications that require efficient access to diverse relational or non-relational data sources across intranets or the Internet. Universal Data Access consists of a collection of software components that interact with each other using system-level interfaces defined by OLE DB and providing an application-level data access model called ActiveX Data Objects (ADO). This talk provides an overview of the platform.
"One way to overcome those problems is to move towards less restricted scenarios. In this context we present a large-scale real-world dataset designed to evaluate learning techniques for human action recognition beyond hand-crafted datasets. To this end we put the process of collecting data on its feet again and start with the annotation of a test set of 250 cooking videos. The training data is then gathered by searching for the respective annotated classes within the subtitles of freely available videos. The uniqueness of the dataset is attributed to the fact that the whole process of collecting the data and training does not involve any human intervention. To address the problem of semantic inconsistencies that arise with this kind of training data, we further propose a semantical hierarchical structure for the mined classes. "
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
"LH* RS is a new high-availability Scalable Distributed Data Structure (SDDS). The data storage scheme and the search performance of LH* RS are basically these of LH*. LH* RS manages in addition the parity information to tolerate the unavailability of k g 1 server sites. The value of k scales with the file, to prevent the reliability decline. The parity calculus uses the Reed -Solomon Codes. The storage and access performance overheads to provide the high-availability are about the smallest possible. The scheme should prove attractive to data-intensive applications."
"Garlic is a middleware system that provides an integrated view of a variety of legacy data sources, without changing how or where data is stored. In this paper, we describe our architecture for wrappers, key components of Garlic that encapsulate data sources and mediate between them and the middleware. Garlic wrappers model legacy data as objects, participate in query planning, and provide standard interfaces for method invocation and query execution. To date, we have built wrappers for 10 data sources. Our experience shows that Garlic wrappers can be written quickly and that our architecture is flexible enough to accommodate data sources with a variety of data models and a broad range of traditional and non-traditional query processing capabilities."
"The growing acceptance of XML as a standard for semi-structured documents on the Web opens up challenging opportunities for Web query languages. In this paper we introduce XML-GL, a graphical query language for XML documents. The use of a visual formalism for representing both the content of XML documents (and of their DTDs) and the syntax and semantics of queries enables an intuitive expression of queries, even when they are rather complex. XML-GL is inspired by G-log, a general purpose, logic-based language for querying structured and semi-structured data. The paper presents the basic capabilities of XML-GL through a sequence of examples of increasing complexity."
"In system monitoring, one is often interested in checking properties of aggregated data. Current policy monitoring approaches are limited in the kinds of aggregations they handle. To rectify this, we extend an expressive language, metric first-order temporal logic, with aggregation operators. Our extension is inspired by the aggregation operators common in database query languages like SQL. We provide a monitoring algorithm for this enriched policy specification language. We show that, in comparison to related data processing approaches, our language is better suited for expressing policies, and our monitoring algorithm has competitive performance."
This paper covers what we at NCR have learned about the TPC-D benchmark as we executed and published our first set of volume points for the Teradata Database. Areas where customers should read the Full Disclosure Report carefully are pointed out as well as the weaknesses in the benchmark relative to real customer applications. The key execution and optimization elements of the Teradata Database and the 5100 WorldMark platform that contribute to our published results are discussed.
"A very promising idea for fast searching in traditional and multimedia databases is to map objects into points in k-d space, using k feature-extraction functions, provided by a domain expert [25]. Thus, we can subsequently use highly fine-tuned spatial access methods (SAMs), to answer several types of queries, including the 'Query By Example' type (which translates to a range query); the 'all pairs' query (which translates to a spatial join [8]); the nearest-neighbor or best-match query, etc.However, designing feature extraction functions can be hard. It is relatively easier for a domain expert to assess the similarity/distance of two objects. Given only the distance information though, it is not obvious how to map objects into points.This is exactly the topic of this paper. We describe a fast algorithm to map objects into points in some k-dimensional space (k is user-defined), such that the dis-similarities are preserved. There are two benefits from this mapping: (a) efficient retrieval, in conjunction with a SAM, as discussed before and (b) visualization and data-mining: the objects can now be plotted as points in 2-d or 3-d space, revealing potential clusters, correlations among attributes and other regularities that data-mining is looking for.We introduce an older method from pattern recognition, namely, Multi-Dimensional Scaling (MDS) [51]; although unsuitable for indexing, we use it as yardstick for our method. Then, we propose a much faster algorithm to solve the problem in hand, while in addition it allows for indexing. Experiments on real and synthetic data indeed show that the proposed algorithm is significantly faster than MDS, (being linear, as opposed to quadratic, on the database size N), while it manages to preserve distances and the overall structure of the data-set."
"Many commercial organizations routinely gather large numbers of databases for various marketing and business analysis functions. The task is to correlate information from different databases by identifying distinct individuals that appear in a number of different databases typically in an inconsistent and often incorrect fashion. The problem we study here is the task of merging data from multiple sources in as efficient manner as possible, while maximizing the accuracy of the result. We call this the merge/purge problem. In this paper we detail the sorted neighborhood method that is used by some to solve merge/purge and present experimental results that demonstrates this approach may work well in practice but at great expense. An alternative method based upon clustering is also presented with a comparative evaluation to the sorted neighborhood method. We show a means of improving the accuracy of the results based upon a multi-pass approach that succeeds by computing the Transitive Closure over the results of independent runs considering alternative primary key attributes in each pass."
"Magic sets rewriting is a well-known optimization heuristic for complex decision-support queries. There can be many variants of this rewriting even for a single query, which differ greatly in execution performance. We propose cost-based techniques for selecting an efficient variant from the many choices.Our first contribution is a practical scheme that models magic sets rewriting as a special join method that can be added to any cost-based query optimizer. We derive cost formulas that allow an optimizer to choose the best variant of the rewriting and to decide whether it is beneficial. The order of complexity of the optimization process is preserved by limiting the search space in a reasonable manner. We have implemented this technique in IBM's DB2 C/S V2 database system. Our performance measurements demonstrate that the cost-based magic optimization technique performs well, and that without it, several poor decisions could be made.Our second contribution is a formal algebraic model of magic sets rewriting, based on an extension of the multiset relational algebra, which cleanly defines the search space and can be used in a rule-based optimizer. We introduce the multiset &theta;-semijoin operator, and derive equivalence rules involving this operator. We demonstrate that magic sets rewriting for non-recursive SQL queries can be modeled as a sequential composition of these equivalence rules."
"Abstract.This paper contains an overview of the technology used in the query processing and optimization component of Oracle Rdb, a relational database management system originally developed by Digital Equipment Corporation and now under development by Oracle Corporation. Oracle Rdb is a production system that supports the most demanding database applications, runs on multiple platforms and in a variety of environments."
"Data extraction from HTML pages is performed by software modules, usually called wrappers. Roughly speaking, a wrapper identifies and extracts relevant pieces of text inside a web page, and reorganizes them in a more structured format. In the literature there is a number of systems to (semi-)automatically generate wrappers for HTML pages. We have recently investigated for original approaches that aims at pushing further the level of automation of the wrapper generation process. Our main intuition is that, in a dataintensive web site, pages can be classified in a small number of classes, such that pages belonging to the same class share a rather tight structure. Based on this observation, we have studied an novel technique, we call the matching technique, that automatically generates a common wrapper by exploiting similarities and differences among pages of the same class. "
"In this paper we present C 2 P, a new clustering algorithm for large spatial databases, which exploits spatial access methods for the determination of closest pairs. Several extensions are presented for scalable clustering in large databases that contain clusters of various shapes and outliers. Due to its characteristics, the proposed algorithm attains the advantages of hierarchical clustering and graphtheoretic algorithms providing both efficiency and quality of clustering result. The superiority of C 2 P is verified both with analytical and experimental results."
"As object technology is adopted by software systems for analysis and design, language, GUI, and frameworks, the database community also is working to support objects, and to develop standards for that support. A key benefit of object technology is the ability for different objects and object tools to interoperate, so it's critical that such DBMS object standards interoperate with those of the rest of the object world. Starting with a discussion of the new issues objects bring to query standards, we present the efforts of various groups relevant to this, including ODMG, OMG, ANSI X3H2 (SQL3), and recent merger efforts feeding into SQL3. What's different with Objects? "
"The naive solution would be to do an exhaustive search across all possible subsets of items and count how many satisfy the predicate conditions we are looking for. This approach, although it would be efficient space-wise (only store the combinations we need) would waste a lot of time (creating all possible combinations). This paper presents a few algorithms that start with a seed itemset (one that already satisfies the boolean predicates we wish to evaluate) and grow them into itemsets of maximal size."
"For a number of reasons, even the best query optimizers can very often produce sub-optimal query execution plans, leading to a significant degradation of performance. This is especially true in databases used for complex decision support queries and/or object-relational databases. In this paper, we describe an algorithm that detects sub-optimality of a query execution plan during query execution and attempts to correct the problem. The basic idea is to collect statistics at key points during the execution of a complex query. These statistics are then used to optimize the execution of the query, either by improving the resource allocation for that query, or by changing the execution plan for the remainder of the query. To ensure that this does not significantly slow down the normal execution of a query, the Query Optimizer carefully chooses what statistics to collect, when to collect them, and the circumstances under which to re-optimize the query. We describe an implementation of this algorithm in the Paradise Database System, and we report on performance studies, which indicate that this can result in significant improvements in the performance of complex queries."
"In this paper a new colour space for content based image retrieval is presented, which is based upon psychophysical research into human perception. It provides both the ability to measure similarity and determine dissimilarity, using fuzzy logic and psychologically based set theoretic similarity measurement. These properties are shown to be equal or superior to conventional colour spaces. Example applications are also demonstrated."
"Tremendous amount of access log data is accumulated at many web sites. Several efforts to mine the data and apply the results to support end-users or to re-design the Web site's structure have been proposed. This paper describes our trial on access logs utilization from commercial yellow page service called ""iTOWNPAGE"". Our initial statistical analysis reveals that many users search various categories-even non-sibling ones in the provided hierarchy - together, or finish their search without any results that match their queries. To solve these problems, we first cluster user requests from the access logs using enhanced K-means clustering algorithm and then apply them for query expansion. Our method includes two-steps expansion that 1) recommends similar categories to the request, and 2) suggests related categories although they are nonsimilar in existing category hierarchy. We also report some evaluations that show the effectiveness of the prototype system."
"We illustrate basic features of the Lixto wrapper generator such as the user and system interaction, the capacious visual interface, the marking and selecting procedures, and the extraction tasks by describing the construction of a simple example program in the current Lixto prototype."
"Sorting is one of the most fundamental algorithms in Computer Science and a common operation in databases not just for sorting query results but also as part of joins (i.e., sort-merge-join) or indexing. In this work, we introduce a new type of distribution sort that leverages a learned model of the empirical CDF of the data. Our algorithm uses a model to efficiently get an approximation of the scaled empirical CDF for each record key and map it to the corresponding position in the output array. We then apply a deterministic sorting algorithm that works well on nearly-sorted arrays (e.g., Insertion Sort) to establish a totally sorted order. We compared this algorithm against common sorting approaches and measured its performance for up to 1 billion normally-distributed double-precision keys. The results show that our approach yields an average 3.38x performance improvement over C++ STL sort, which is an optimized Quicksort hybrid, 1.49x improvement over sequential Radix Sort, and 5.54x improvement over a C++ implementation of Timsort, which is the default sorting function for Java and Python."
"A methodology of reengineering existing extended Entity-Relationship(EER) model to Object Modeling Technique(OMT) model is described. A set of translation rules from EER model to a generic Object-Oriented(OO) model of OMT methodology is devised. Such reengineering practices not only can provide us with significant insight to the ""interoperability"" between the OO and the traditional semantic modelling techniques, but also can lead us to the development of a practical design methodology for object-oriented databases(OODB)."
"E-commerce is not a static field, but is constantly evolving to discover new and more effective ways of supporting businesses. Data management is an integral part of this effort, This special issue aims to report on some of the recent developments and identify some research directions in this area. Initially, e-commeree involved the use of ED] and intranets. Today we see the dominance of XML. Almost all recent elecn'onic commerce standards are based on X1VD... As a consequence, the amount of XML data being stored is large, and it is increasing. This naturally leads to the question of how to store and query the XML documents. The paper by Tian, DeWitt, Chen and Zhang describes the design and performance evaluation of alternative XM]., storage strategies. The results of this performance study provide valuable hints on how to store the XM1., files depending on the application. Personalization in e-commerce is about building customer loyalty by understanding and thus addressing the needs of each individual. E-commerce systems need customers' profiles to provide better services, "
"We present novel algorithms for the problem of using materialized views to compute answers to SQL queries with grouping and aggregation, in the presence of multiset tables. ln addition to its obvious potential in query optimization, this problem is important in many applications, such as data warehousing, very large transaction recording systems, global information systems and mobile computing, where access to local or cached materialized views may be cheaper than access to the underlying database. Our contributions are the following: First, we show that in the case where the query has grouping and aggregation but the views do not, a view is usable in answering a query only if there is an isomorphism between the view and a portion of the query. Second, when the views also have grouping and aggregation we identify conditions under which the aggregation information present in a view is sufficient to perform the aggregation computations requited in the query. The algorithms we describe for rewriting a query also consider the case in which the rewritten query may be a union of single-block queries. Our approach is a semantic one, in that it detects when the information existing in a view is sufficient to answer a query. In contrast, previous work performed syntactic transformations on the query such that the definition of the view would be a sub-part of the definition of the query. Consequently, these methods can only detect usages of views in limited cases."
"Fast indexing in time sequence databases for similarity searching has attracted a lot of research recently. Most of the proposals, however, typically centered around the Euclidean distance and its derivatives. We examine the problem of multimodal similarity search in which users can choose the best one from multiple similarity models for their needs. In this paper, we present a novel and fast indexing scheme for time sequences, when the distance function is any of arbitrary Lp norms (p = 1; 2; : : : ;1). One feature of the proposed method is that only one index structure is needed for all Lp norms including the popular Euclidean distance (L2 norm). Our scheme achieves significant speedups over the state of the art: extensive experiments on real and synthetic time sequences show that the proposed method is comparable to the best competitor forL2 andL1 norms, but significantly (up to 10 times) faster for L1 norm."
"In recent years, new developments in genetics have generated a lot of interest in genomic and proteomic data, investing international significance (and competition) in the fledgling discipline of bioinformatics. Researchers in pharmaceutical and biotech companies have found that database products can bring a wide range of relevant technologies to bear on their problems. Benefiting from a number of new technology enhancements, Oracle has emerged as a popular platform for pharmaceutical knowledge management and bioinformatics. We look at four powerful technologies that show promise for solving hitherto intractable problems in bioinformatics: the extensibility architecture to store gene sequence data natively and perform high-dimensional structure-searches in the database; warehousing technologies and data mining on genetic patterns; data integration technologies to enable heterogeneous queries across distributed biological sources, and internet portal technologies that allow life sciences information to be published and managed across intranets and the internet."
"Users of the Web are overloaded with information. This medium is ¡°polluted¡± with redundant, erroneous and low quality information. A WWW survey of 11,700 users conducted from April 10 to May 10, 1996[1] indicates that 30.31% of the users report ¡°finding known info¡± is their problem and 27.80% of the users report organizing collected information as their problem. An empirical study[2] on users¡¯ revisitation patterns to WWW pages found that 58% of an individual¡¯s pages are revisits. With these study results, we believe the Web users would like to build and organize a larger collection of bookmarks for future references than they can reasonably maintain now."
"We present a scalable distributed data structure called LH*. LH* generalizes Linear Hashing (LH) to distributed RAM and disk files. An LH* file can be created from records with primary keys, or objects with OIDs, provided by any number of distributed and autonomous clients. It does not require a central directory, and grows gracefully, through splits of one bucket at a time, to virtually any number of servers. The number of messages per random insertion is one in general, and three in the worst case, regardless of the file size. The number of messages per key search is two in general, and four in the worst case. The file supports parallel operations, e.g., hash joins and scans. Performing a parallel operation on a file of M buckets costs at most 2M + 1 messages, and between 1 and O(log2 Mrounds of messages. We first describle the basic LH* scheme where a coordinator site manages abucket splits, and splits a bucket every time a collision occurs. We show that the average load factor of an LH* file is 65%¨C70% regardless of file size, and bucket capacity. We then enhance the scheme with load control, performed at no additional message cost. The average load factor then increases to 80¨C95%. These values are about that of LH, but the load factor for LH* varies more. We nest define LH* schemes without a coordinator. We show that insert and search costs are the same as for the basic scheme. The splitting cost decreases on the average, but becomes more variable, as cascading splits are needed to prevent file overload. Next, we briefly describe two variants of splitting policy, using parallel splits and presplitting that should enhance performance for high-performance applications. All together, we show that LH* files can efficiently scale to files that are orders of magnitude larger in size than single-site files. LH* files that reside in main memory may also be much faster than single-site disk files. Finally, LH* files can be more efficient than any distributed file with a centralized directory, or a static parallel or distributed hash file."
"Multimedia applications demand specific support from database management systems due to the characteristics of multimedia data and their interactive usage. This includes integrated support for high-volume and time-dependent (continuous) data types like audio and video. One critical issue is to provide handling of continuous data streams including buffer management as needed for multimedia presentations. Buffer management strategies for continuous data have to consider specific requirements like providing for continuity of presentations, for immediate continuation of presentations after frequent user interactions by appropriate buffer resource consumption. Existing buffer management strategies do not sufficiently support the handling of continuous data streams in highly interactive multimedia presentations. In this paper we present the ¡°least/most relevant for presentation¡± (LJMRP) buffer management strategy whichconsiderspresentationspecificinformationin order to provide an optimized behavior with respect to the requirements mentioned above. WMRP is a framework to formulate specific interaction models and is therefore adaptable to individual multimedia applications. We present a simulation study showing that an instantiated L/MRP outperforms existing approachesforgiventypesofinteractivemultimedia applications. It is shown that UMRP is especially suitable to support highly interactive multimedia presentations. "
"XML is fast emerging as the dominant standard for representing data in the World Wide Web. Sophisticated query engines that allow users to effectively tap the data stored in XML documents will be crucial to exploiting the full power of XML. While there has been a great deal of activity recently proposing new semistructured data models and query languages for this purpose, this paper explores the more conservative approach of using traditional relational database engines for processing XML documents conforming to Document Type Descriptors (DTDs). To this end, we have developed algorithms and implemented a prototype system that converts XML documents to relational tuples, translates semi-structured queries over XML documents to SQL queries over tables, and converts the results to XML. We have qualitatively evaluated this approach using several real DTDs drawn from diverse domains. It turns out that the relational approach can handle most (but not all) of the semantics of semi-structured queries over XML data, but is likely to be effective only in some cases. We identify the causes for these limitations and propose certain extensions to the relational model that would make it more appropriate for processing queries over XML documents."
"In a database to which data is continually added, users may wish to issue a permanent query and be notified whenever data matches the query. If such continuous queries examine only single records, this can be implemented by examining each record as it arrives. This is very efficient because only the incoming record needs to be scanned. This simple approach does not work for queries involving joins or time. The Tapestry system allows users to issue such queries over a database of mail and bulletin board messages. The user issues a static query, such as ¡°show me all messages that have been replied to by Jones,¡± as though the database were fixed and unchanging. Tapestry converts the query into an incremental query that efficiently finds new matches to the original query as new messages are added to the database. This paper describes the techniques used in Tapestry, which do not depend on triggers and thus be implemented on any commercial database that supports SQL. Although Tapestry is designed for filtering mail and news messages, its techniques are applicable to any append-only database."
"Scientific experiments and large-scale simulations produce massive amounts of data. Many of these scientific datasets are arrays, and are stored in file formats such as HDF5 and NetCDF. Although scientific data management systems, such as SciDB, are designed to manipulate arrays, there are challenges in integrating these systems into existing analysis workflows. Major barriers include the expensive task of preparing and loading data before querying, and converting the final results to a format that is understood by the existing post-processing and visualization tools. As a consequence, integrating a data management system into an existing scientific data analysis workflow is time-consuming and requires extensive user involvement. In this paper, we present the design of a new scientific data analysis system that efficiently processes queries directly over data stored in the HDF5 file format. This design choice eliminates the tedious and error-prone data loading process, and makes the query results readily available to the next processing steps of the analysis workflow. Our design leverages the increasing main memory capacities found in supercomputers through bitmap indexing and in-memory query execution. In addition, query processing over the HDF5 data format can be effortlessly parallelized to utilize the ample concurrency available in large-scale supercomputers and modern parallel file systems. We evaluate the performance of our system on a large supercomputing system and experiment with both a synthetic dataset and a real cosmology observation dataset. Our system frequently outperforms the relational database system that the cosmology team currently uses, and is more than 10X faster than Hive when processing data in parallel. Overall, by eliminating the data loading step, our query processing system is more effective in supporting in situ scientific analysis workflows."
"In this paper, we consider various spatial relationships that are of general interest in pictorial database systems. We present a set of rules that allow us to deduce new relationships from a given set of relationships. A deductive mechanism using these rules can be used in query processing systems that retrieve pictures by content. The given set of rules are shown to be sound, i.e. the deductions are logically correct. The rules are also shown to be complete for three dimensional systems, i.e. every relationship which is implied by a given consistent set of relationships F is deducible from F using the given rules. In addition, we show that the given set of rules is incomplete for two dimensional systems."
"In this paper, we take a retrospective look at the problem of querying and updating location dependent data in massively distributed mobile environments. Looking forward, we paint our vision of the future dataspace - physical space enhanced with embedded digital information. Finally we describe a few of the applications enabled by dataspace due to the availability of large scale ad-hoc sensor networks, short-range wireless communications, and fine-grain location information."
"Interacting with a multimedia information system is different from interacting with a standard text-based information system. In this paper, we present the design of a system called Content-Based Hypermedia (CBH), which allows a user to utilize metadata to intelligently browse through a collection of media objects. We describe the approach we use to model data in order to make it browsable, explore our approach to browsing, which we call metadata mediated browsing, indicate how metadata is used in the concept of similarity, present the architecture of our system, and discuss indexing techniques for similarity browsing using content-based metadata and approaches to clustering which generate higher-level metadata to help the user browse more effectively."
"We propose an approach for indexing fuzzy data based on inverted files that speeds up retrieval considerably by stopping the traversal of postings lists early. This is possible because the entries in the postings lists are organized in a way that guarantees that there are no matching items beyond a certain point in a list. Consequently, we can reduce the number of false positives significantly, leading to an increase in retrieval performance. We have implemented our approach and evaluated it experimentally, including a test on skewed and real-world data, comparing it to an approach that has previously been shown to be superior to other methods."
"This paper reports on the managerial experience, technical approach, and lessons learned from reengineering eight departmental large-scale information systems. The driving strategic objective of each project was to migrate these systems into a set of enterprise-wide systems, which incorporate current and future requirements, drastically reduce operational and maintenance cost, and facilitate common understandings among stakeholders (i.e., policy maker, high-level management, IS developer/maintainer/ end-users). A logical data model , which contains requirements, rules, physical data representation as well as logical data object, clearly documents the baseline data requirements implemented by the legacy system and is crucial to achieve this strategic goal. Re-engineering products are captured in the dictionaries of a CASE tool (i.e., in the form of a business process decomposition hierarchy, as-is data model, normalized logical data model, and linkages among data objects) and are supplemented with traceability matrices in spreadsheets. The re-engineered data products are used as follows: (1) migration of the legacy databases to relational database management systems, (2) automatically generation of databases and applications for migration from mainframes to client-server, (3) enterprise data standardization, (4) integration of disparate information systems, (5) re-documentation, (6) data quality assessment and assurance, and (7) baseline specifications for future systems. "
"As teachers, if we believe content knowledge matters the most for successful instruction, we may not understand that getting to know students and discovering their strengths as learners are equally important. Teachers are instructional islands with a lot of content to share but perhaps unconnected to the learners that make up the classroom. If as teachers, we describe students by saying, ¡°she is a math wizard,¡± ¡°she is a science ace,¡± or ¡°he is a sponge for historical facts,¡± we can communicate a lot about students with minimal language. These metaphors help us make comparisons that evoke multiple layers of meaning, and yet thinking metaphorically is also an aspect of everyday life. Cognitive scientists Lakoff and Johnson (2008) argued that our conceptualizations of the world around us are metaphorical and provided examples of metaphors such as ¡°time is money¡± and suggested that the way we construe argument is conceived in metaphors of war when we ¡°attack a position,¡± for example, to support a philosophical claim. From an educational philosophy perspective, Greene contended learning is a landscape (1973) and teachers are philosophers working to help learners resist the forces that limit and oppress them (1988) to attain freedom to think for themselves. These theorists recognized the epistemological power of metaphor and challenged us to see its educational potential. Comparisons through metaphoric thinking afford different perspectives and open imaginative possibilities, challenging us to see familiar relationships in new ways. Metaphors can push us to think about teacher education differently as well and move beyond familiar views of clinical experiences, teacher interns, teacher preparation programs, and who we are as educators to see these concepts more complexly. "
"Abstract. Recent results in the Rio project at the University of Michigan show that it is possible to create an area of main memory that is as safe as disk from operating system crashes. This paper explores how to integrate the reliable memory provided by the Rio file cache into a database system. Prior studies have analyzed the performance benefits of reliable memory; we focus instead on how different designs affect reliability. We propose three designs for integrating reliable memory into databases: non-persistent database buffer cache, persistent database buffer cache, and persistent database buffer cache with protection. Non-persistent buffer caches use an I/O interface to reliable memory and require the fewest modifications to existing databases. However, they waste memory capacity and bandwidth due to double buffering. Persistent buffer caches use a memory interface to reliable memory by mapping it into the database address space. This places reliable memory under complete database control and eliminates double buffering, but it may expose the buffer cache to database errors. Our third design reduces this exposure by write protecting the buffer pages. Extensive fault tests show that mapping reliable memory into the database address space does not significantly hurt reliability. This is because wild stores rarely touch dirty, committed pages written by previous transactions. As a result, we believe that databases should use a memory interface to reliable memory."
"Large multimedia document archives hold most of their data in near-line tertiary storage libraries for cost reasons. This paper develops an integrated approach to the vertical data migration hetween the tertiary and secondary storage in that it reconciles speculative preloading, to mask the high latency of the tertiary storage, with the replacement policy of the secondary storage. In addition, it considers the interaction of these policies with the tertiary storage scheduling and controls preloading aggressiveness by taking contention for tertiary storage drives into account. The integrated migration policy is based on a continuous-time Markov-chain (CTMC) model,fijr predicting the expected number of accesses to a document within a specified time horizon. The parameters of the CTMC model, the probabilities of co-accessing certain documents and the interaction times between successive accesses, are dynamically estimated and adjusted to evolving workload patterns by keeping online statistics. The integrated policy for vertical data migration has been implemented in a prototype system. Detailed simulation studies with Web-server-like synthetic workloads indicate sign$cant gains in terms of client response time. The studies also show that the overhead of the statistical bookkeeping and the computations for the access predictions is affordable."
"Most previous solutions to the schema matching problem rely in some fashion upon identifying ""similar"" column names in the schemas to be matched, or by recognizing common domains in the data stored in the schemas. While each of these approaches is valuable in many cases, they are not infallible, and there exist instances of the schema matching problem for which they do not even apply. Such problem instances typically arise when the column names in the schemas and the data in the columns are ""opaque"" or very difficult to interpret. In this paper we propose a two-step technique that works even in the presence of opaque column names and data values. In the first step, we measure the pair-wise attribute correlations in the tables to be matched and construct a dependency graph using mutual information as a measure of the dependency between attributes. In the second stage, we find matching node pairs in the dependency graphs by running a graph matching algorithm. We validate our approach with an experimental study, the results of which suggest that such an approach can be a useful addition to a set of (semi) automatic schema matching techniques."
"Financial mathematicians think they can predict the future by looking at time series of trades and quotes (called ticks) from the past. The main evidence for this hypothesis is that prices fluctuate only by a small amount in a given day and more or less obey the mathematics of a random walk. The hypothesis allows traders to price options and to speculate on stocks. This demonstration presents a query language and a parallel database (50-way parallelism) to support traders who want to analyze every tick, not just end-of-day ticks, using temporal statistical queries such as time-delayed correlations and tick trends. This is the first attempt that we know of to store and analyze hundreds of gigabytes of time series data and to query that data using a declarative time series extension to SQL."
"In the last years, the exponential growth of computer networks has created an incredibly large offer of products and services in the net. Such a huge amount of information makes it impossible for a single person to analyze all existing offers of a product on the net and decide which of them fits better her requirements. This problem is solved with the intelligent trade agents (ITA), which are programs that have the ability to roam a network, collect business-related data and use them to make decisions to buy goods on their owners' behalf. Known ITA systems do not provide anonymity in transactions, require an on-line trusted third party and implicitly assume that the user trusts the ITA. We present a new scheme for an intelligent untrusted trade agent system allowing anonymous electronic transactions with an off-line trusted third party."
Documents stored in a database system can have complex internal structure described by a language such as SGML. How to take advantage of this structure presents challenges for database system implementors. We provide a classi cation of the types of queries that need to be supported by SGML conformant database systems. We then describe several data models that have been proposed for representing documents in a database system and the degree to which these models provide support for SGML. Finally we turn to the issue of evaluating queries considering the classic solutions for indexing text for Boolean and ranked retrieval. We describe techniques for improving the space and time e ciency of both.
"s [41, 42]. academia [1932, 1926, 2267, 2275]. academic [1908, 2441]. acceleration [1869]. Access [2370, 13, 38, 1530, 1620, 1555, 2106, 1643, 1410, 602, 1672, 1033, 531, 601, 803, 1532, 1531, 949, 2204, 1455, 657, 598, 1263, 1086, 749, 409, 1969, 319, 2119, 450, 872, 1808, 171, 1559, 238, 821, 812, 1209, 1198, 694, 126, 1357, 883, 2139]. accesses [406]. Accessing [1295, 127, 515]. Accommodating [626]. account [1889]. accounting [679]. accrued [2385]. Accurate [276, 855]. achieve [858]. Achievements [1238, 619, 627]. ACID [1688]. ACM [38, 2139, 2216, 14, 2106, 2290, 2291, 42, 2239, 2445, 13, 2472, 2475, 2476, 2477, 2479, 2480, 1580, 1099, 2478, 2130, 2474, 1946, 1697, 2213, 2029, 2143, 2319, 2397, 2262]. ACM-SIGFIDET [38, 14]. Acquisition [288]. Across [1645, 2393, 1936]. ACT [1322]. ACT-NET [1322]. ACTA [586]. action [761]. Actions [1329]. activation [851]. Active [1322, 1239, 970, 833, 1471, 272, 1574, 1407, 1071, 1321, 1236, 1174, 420, 1171, 546, 1914, 1178, 1470, 766, 1098, 521, 1228, 1444, 1126, 1065]. Activities [136, 984, 216, 156, 1965, 587, 67, 748, 820]. activity [1311, 196]. Actual [211]. Ad [1394, 2001, 2056, 3]. ad-hoc [2001]. Ada [249, 458]. ADAM [1897]. adapt [2406]. Adaptable [1807]. adaptation [2113, 2328, 1209]. Adapting [1121, 254]. Adaptive [1730, 1675, 1002, 1642, 1024, 1826, 1112, 1737, 304, 1282, 307, 1809, 567]. ADBIS¡¯2001 [1931]. ADBMS [1321, 1322]. adding [463]. Addison [2043, 66]. Addison-Wesley [66]. Address [1148, 749, 1147, 642]. Addressing [1199]. ADEPT [1588]. Administering [221, 1303]. Administration [1478, 53]. Ado [1317]. ADO.NET [2236]. ADS [1071]. Advanced [1881, 952, 740, 1765, 2405, 1062, 678, 924, 1177]. Advancements [2105]. Advances [1227, 1931]. advantage [1163]. adventure [2310]. adversarial [2337]. Affiliation [2402]. after [1121]. again [1875]. against [471, 1939]. Agenda [1040]. Agent [1386, 1607, 2047, 1588, 1919, 1198, 2065]. Agent-Based [1386, 1607, 1588, 1198]."
"Micro-level Planning is gaining momentum in developing countries. The Planning steps, the data needs, the institutional requirements, the macro-micro linkages and the information flows are necessary to make the planning process effective. Indian planning and development process is aheading for a change from the centralised to more of decentralised approach in order to give due recognition to the micro-level needs and potentials in decision making. The committee on Study Group on Information Gap, constituted by the Planning Commission, Government of India, in 1989 has recommended for the creation of data bases on (i) Plan Information, (ii) Plan Monitoring, and (iii) Plan Evaluation, in districts. This committee has also recommended to develop databases with respect to (i) Socio-economic, (ii) Agro-economic, (iii) Infrastructure, (iv) Demographic, and (v) Natural resources."
"Abstract. In a multidatabase system, schematic conflicts between two objects are usually of interest only when the objects have some semantic similarity. We use the concept of semantic proximity, which is essentially an abstraction/mapping between the domains of the two objects associated with the context of comparison. An explicit though partial context representation is proposed and the specificity relationship between contexts is defined. The contexts are organized as a meet semi-lattice and associated operations like the greatest lower bound are defined. The context of comparison and the type of abstractions used to relate the two objects form the basis of a semantic taxonomy. At the semantic level, the intensional description of database objects provided by the context is expressed using description logics. The terms used to construct the contexts are obtained from {\em domain-specific ontologies}. Schema correspondences are used to store mappings from the semantic level to the data level and are associated with the respective contexts. "
"Grids can span locations, machine architectures, and software applications to provide unlimited power, seamless collaboration, and wider information access. With the changing demands of the markets and the developments of the technology itself, grid computing is beginning to spill out over the boundaries of individual organizations. These partner grids create a collaboration environment to share computing resources, data and applications. OPGSA is a grid-based implementation of ebusiness solutions built upon commercial enterprise grid systems, and it makes use of Globus Toolkits 4 and DRAMA open standards. With this architecture, it is possible for the firms participating in a corporate supply chain to incorporate greater management capabilities and gain greater control over complex business processes. "
"Video is composed of audio-visual information. Providing content based access to video data is essential for the sucessful integration of video into computers. Organizing video for content based access requires the use of video metadata. This paper explores the nature video metadata. A data model for video databases is presented based on a study of the applications of video, the nature of video retrieval requests, and the features of video. The data model is used in the architectural framework of a video database. The current state of technology in video databases is summarized and research issues are highlighted."
"The continuous growth in scale and diversity of computer networks and network components has made network management one of the most challenging issues facing network administrators. It has become impossible to carry out network management functions without the support of automated tools and applications. In this chapter, the major network management issues, including network management requirements, functions, techniques, security, some wellknown network management protocols and tools, will be discussed. Location management for the wireless cellular networks will also be briefly described. Finally, policy-based network management, which is a promising direction for the next generation of network management, will be briefly described."
"Personalization, which will be a key success factor for forthcoming XML-based Web standards like ebXML or MPEG-7, needs a powerful framework for preferences. The research program ¡±It¡¯s a Preference World¡± at the University of Augsburg treats preferences as first class citizens in personalized e-services. Based on a rich theory of preferences modeled as partial orders we are developing enabling technologies for personalized client and middleware components. In this positional paper we sketch an architecture for content syndication in such a Preference World."
"SchemaSQL is a recently proposed extension to SQL for enabling multi-database interoperability. Several recently identi ed applications for SchemaSQL, however, mainly rely on its ability to treat data and schema labels in a uniform manner, and call for an e cient implementation of it on a single RDBMS. We rst develop a logical algebra for SchemaSQL by combining classical relational algebra with four restructuring operators { unfold, fold, split, and unite { originally introduced in the context of the tabular data model by Gyssens et al. [GLS96], and suitably adapted to t the needs of SchemaSQL. We give an algorithm for translating SchemaSQL queries/views involving restructuring, into the logical algebra above. We also provide physical algebraic operators which are useful for query optimization. Using the various operators as a vehicle, we give several alternate implementation strategies for SchemaSQL queries/views. All the proposed strategies can be implemented non-intrusively on top of existing relational DBMS, in that they do not require any additions to the existing set of plan operators. We conducted a series of performance experiments based on TPC-D benchmark data, using the IBM DB2 DBMS running on Windows/NT. In addition to showing the relative tradeo s between various alternate strategies, our experiments show the feasibility of implementing SchemaSQL on top of traditional "
"Various models and languages for describing and manipulating hierarchically structured data have been proposed. Algebraic, calculus-based, and logic-programming oriented languages have all been considered. This article presents a general model for complex values (i.e., values with hierarchical structures), and languages for it based on the three paradigms. The algebraic language generalizes those presented in the literature; it is shown to be related to the functional, style of programming advocated by Backus (1978). The notion of domain independence (from relational databases) is defined, and syntactic restrictions (referred to as safety conditions) on calculus queries are formulated to guarantee domain independence. The main results are: The domain-independent calculus, the safe calculus, the algebra, and the logic-programming oriented language have equivalent expressive power. In particular, recursive queries, such as the transitive closure, can be expressed in each of the languages. For this result, the algebra needs the powerset operation. A more restricted version of safety is presented, such that the restricted safe calculus is equivalent to the algebra without the powerset. The results are extended to the case where arbitrary functions and predicates are used in the languages."
"We consider the problem of evaluating large numbers of XPath filters, each with many predicates, on a stream of XML documents. The solution we propose is to lazily construct a single deterministic pushdown automata, called the XPush Machine from the given XPath fllters. We describe a number of optimization techniques to make the lazy XPush machine more efficient, both in terms of space and time. The combination of these optimizations results in high, sustained throughput. For example, if the total number of atomic predicates in the filters is up to 200000, then the throughput is at least 0.5 MB/sec: it increases to 4.5 MB/sec when each fllter contains a single predicate."
"Workflow management systems (WfMSs) have been used to support various types of business processes for more than a decade now. In workflows or Web processes for e-commerce and Web service applications, suppliers and customers define a binding agreement or contract between the two parties, specifying Quality of Service (QoS) items such as products or services to be delivered, deadlines, quality of products, and cost of services. The management of QoS metrics directly impacts the success of organizations participating in e-commerce. Therefore, when services or products are created or managed using workflows or Web processes, the underlying workflow engine must accept the specifications and be able to estimate, monitor, and control the QoS rendered to customers. In this paper, we present a predictive QoS model that makes it possible to compute the quality of service for workflows automatically based on atomic task QoS attributes. We also present the implementation of our QoS model for the METEOR workflow system. We describe the components that have been changed or added, and discuss how they interact to enable the management of QoS."
"Int#ra-operator (or partitioned) parallelism is a well-established mechanism for achieving high performance in parallel database systems. However, the problem of how to exploit intra-operator parallelism in a multi-query environment is not well underst,ood. This paper presents a detailed performance evaluation of several algorithms for managing intra-operator parallelism in a parallel database system. A dynamic scheme based on the concept of matching the ra.te of flow of tuples between operat,ors is shown to perform well on a variety of workloads and configurations."
"The emerging new generation of the SQL Standard, called SQL3, have been under development by ANSI X3H2 and ISO/lEC JTC 1/SC2 1 over the last d years. SQL3 is a muhl-volume, upward-compatible extension to SQL-92 contammg a large number of extensions over its predecessor, These new capabilities are specified in separate, independent volumes that are expected to start emerging as new SQL standards this year."
"In this paper, we first focus our attention on the question of how much space remains for performance improvement over current association rule mining algorithms. Our strategy is to compare their performance against an ¡°Oracle algorithm¡± that knows in advance the identities of all frequent itemsets in the database and only needs to gather their actual supports to complete the mining process. Our experimental results show that current mining algorithms do not perform uniformly well with respect to the Oracle for all database characteristics and support thresholds. In many cases there is a substantial gap between the Oracle¡¯s performance and that of the current mining algorithms. Second, we present a new mining algorithm, called ARMOR, that is constructed by making minimal changes to the Oracle algorithm. ARMOR consistently performs within a factor of two of the Oracle on both real and synthetic datasets over practical ranges of support specifications."
"An important challenge to web technologies such as proxy caching, web portals, and application servers is keeping cached data up-to-date. Clients may have different preferences for the latency and recency of their data. Some prefer the most recent data, others will accept stale cached data that can be delivered quickly. Existing approaches to maintaining cache consistency do not consider this diversity and may increase the latency of requests, consume excessive bandwidth, or both. Further, this overhead may be unnecessary in cases where clients will tolerate stale data that can be delivered quickly. This paper introduces latency-recency profiles, a set of parameters that allow clients to express preferences for their different applications. A cache or portal uses profiles to determine whether to deliver a cached object to the client or to download a fresh object from a remote server. We present an architecture for profiles that is both scalable and straightforward to implement at a cache. Experimental results using both synthetic and trace data show that profiles can reduce latency and bandwidth consumption compared to existing approaches, while still delivering fresh data in many cases. When there is insufficient bandwidth to answer all requests at once, profiles significantly reduce latencies for all clients."
"Introduction and Main Contributions Providing mechanisms that allow the user to retrieve desired multimedia information by their semantic content is now an important issue in multimedia databases. However, current prototypes (e.g. Oracle 8i interMedia and Informix Datablade Modules) index mostly only low-level features of multimedia objects. Therefore special techniques are needed for semantic indexing and retrieval of multimedia objects. In this context we present the SMOOTH system, a prototype of a distributed multimedia database system. It implements an integrated querying, annotating, and navigating framework relying on a generic video indexing model. The framework allows the structuring of videos into logical and physical units, and the annotation of these units by typed semantic objects. An index-database stores these structural and semantic information. We provide further a clear concept for capturing and querying the semantic content of multimedia objects, their correlation with low-level objects, as well as their spatio-temporal relationships."
"Abstract. We describe a novel approach for clustering collections of sets, and its application to the analysis and mining of categorical data. By ¡°categorical data,¡± we mean tables with fields that cannot be naturally ordered by a metric ¨C e.g., the names of producers of automobiles, or the names of products offered by a manufacturer. Our approach is based on an iterative method for assigning and propagating weights on the categorical values in a table; this facilitates a type of similarity measure arising from the co-occurrence of values in the dataset. Our techniques can be studied analytically in terms of certain types of non-linear dynamical systems."
"Like any other data, biological data is a very vast one. Due to emergence of system biology it is necessary to develop various platforms and techniques to analyze and organize the biological data in meaning full manner for which it to be mined and processed carefully. As the complexity associated with biological data is high ,it has to be studied considering various criteria¡¯s and also it is mandatory to study all available databases and then has to undergo several processing mining techniques to finally put in a format which is easy to assess and produce the information of interest. There are various techniques and method for mining biological data. Here we will put forth all possible techniques and operations involved in data mining and will compare them in order to find the advantages and disadvantages of different methods"
"Database researchers have made significant progress on several research issues related to multidimensional data analysis, including the development of fast cubing algorithms, efficient schemes for creating and maintaining precomputed group-bys, and the design of efficient storage structures for multidimensional data. However, to date there has been little or no work on multidimensional query optimization. Recently, Microsoft has proposed ¡°OLE DB for OLAP¡± as a standard multidimensional interface for databases. OLE DB for OLAP defines Multi-Dimensional Expressions (MDX), which have the interesting and challenging feature of allowing clients to ask several related dimensional queries in a single MDX expression. In this paper, we present three algorithms to optimize multiple related dimensional queries. Two of the algorithms focus on how to generate a global plan from several related local plans. The third algorithm focuses on generating a good global plan without first generating local plans. We also present three new query evaluation primitives that allow related query plans to share portions of their evaluation. Our initial performance results suggest that the exploitation of common subtask evaluation and global optimization can yield substantial performance improvements when relational database systems are used as data sources for multidimensional analysis. "
"Abstract: Technological advances in and convergence of the World Wide Web with Electronic Data Interchange and standard middleware such as CORBA have given rise to a new computing paradigm based on a loosely coupled service-oriented architecture called Web Services. Direct machine to machine interactions that were hitherto deemed infeasible are now possible due to the rapid technological advances in XML and SOAP technologies. There is, however, an unprecedented hype surrounding this new paradigm. In reality, the Web services paradigm lacks a precise definition. Furthermore, the usecase scenarios for Web services and its pros and cons compared to existing, well-defined middleware technologies such as CORBA are not well understood."
"Design of software architecture is seen as abstraction over the software domain, and describing architecture is considered to be a modeling process. A general view of a modeling process is presented and illustrated in the context of application domain modeling and of software domain modeling. The implications of this perspective are investigated in order to capture objectives and concrete forms of architectural descriptions. The consequences of this perspective on architecture are characterized."
"Database design commonly assumes, explicitly or implicitly, that instances must belong to classes. This can be termed the assumption of inherent classification. We argue that the extent and complexity of problems in schema integration, schema evolution, and interoperability are, to a large degree, consequences of inherent classification. Furthermore, we make the case that the assumption of inherent classification violates philosophical and cognitive guidelines on classification and is, therefore, inappropriate in view of the role of data modeling in representing knowledge about application domains. As an alternative, we propose a layered approach to modeling in which information about instances is separated from any particular classification. Two data modeling layers are proposed: (1) an instance model consisting of an instance base (i.e., information about instances and properties) and operations to populate, use, and maintain it; and (2) a class model consisting of a class base (i.e., information about classes defined in terms of properties) and operations to populate, use, and maintain it. The two-layered model provides class independence. This is analogous to the arguments of data independence offered by the relational model in comparison to hierarchical and network models."
"XQuery is the de facto standard XML query language, and it is important to have efficient query evaluation techniques available for it. A core operation in the evaluation of XQuery is the finding of matches for specified tree patterns, and there has been much work towards algorithms for finding such matches efficiently. Multiple XPath expressions can be evaluated by computing one or more tree pattern matches.    However, relatively little has been done on efficient evaluation of XQuery queries as a whole. In this paper, we argue that there is much more to XQuery evaluation than a tree pattern match. We propose a structure called generalized tree pattern (GTP) for concise representation of a whole XQuery expression. Evaluating the query reduces to finding matches for its GTP. Using this idea we develop efficient evaluation plans for XQuery expressions, possibly involving join, quantifiers, grouping, aggregation, and nesting.    XML data often conforms to a schema. We show that using relevant constraints from the schema, one can optimize queries significantly, and give algorithms for automatically inferring GTP simplifications given a schema. Finally, we show, through a detailed set of experiments using the TIMBER XML database system, that plans via GTPs (with or without schema knowledge) significantly outperform plans based on navigation and straightforward plans obtained directly from the query."
"There has been tremendous interest in information integration systems that automatically gather, manipulate, and integrate data from multiple information sources on a user's behalf. Unfortunately, web sites are primarily designed for human browsing rather than for use by a computer program. Mechanically extracting their content is in general a rather di cult job if not impossible [4]. Software systems using such web information sources typically use hand-coded wrappers to extract information content of interest from web sources and translate query responses to a more structured format (e.g., relational form) before unifying them into an integrated answer to a user's query. The most recent generation of information mediator systems (e.g., Ariadne [3], CQ [5, 7], Internet Softbots [4], TSIMMIS [2]) addresses this problem by enabling a pre-wrapped set of web sources to be accessed via database-like queries. However, hand-coding a wrapper is time consuming and error-prone. We have also observed that, by using a good design methodology, only a relatively small part of the code deals with the source-speci c access details, the rest of the code is either common among wrappers or can be expressed in a high level, more structured fashion. As the Web grows, maintaining a reasonable number of wrappers becomes impractical. First, the number of information sources of interest to a user query can be quite large, even within a particular domain. Second, new information sources are constantly added on the Web. Thirdly, the content and presentation format of the existing information sources may change frequently and autonomously. With these observations in mind, we have developed a wrapper generation system, called XWrap, for semi-automatic construction of wrappers for Web information sources. The system contains a library of commonly used functions, such as receiving queries from applications, handling of lter queries, and packaging results. It also contains some source-speci c facilities that are in charge of mapping a mediator query to a remote connection call to fetch the relevant pages and translating the retrieved page(s) into a more structured format (such as XML documents or relational tables)."
"Phrase matching is a common IR technique to search text and identify relevant documents in a document collection. Phrase matching in XML presents new challenges as text may be interleaved with arbitrary markup, thwarting search techniques that require strict contiguity or close proximity of keywords. We present a technique for phrase matching in XML that permits dynamic specification of both the phrase to be matched and the markup to be ignored. We develop an effective algorithm for our technique that utilizes inverted indices on phrase words and XML tags. We describe experimental results comparing our algorithm to an indexed-nested loop algorithm that illustrate our algorithm's efficiency."
"Despite the success of the Oracle8i Extensibility Framework to index data from diverse domains (including text, images, spatial objects, chemical compounds, molecular structures, and genomic sequences), developing an indexing scheme is perceived as a difficult task, to be embarked upon only by experts, that too, for building support for complex domains. The goal of this demonstration is to show that: 1) the task of building and integrating an indexing scheme with the Oracle8i Extensibility Framework is quite simple and 2) the applicability of the framework is not limited to complex domains. We chose to develop an indexing scheme for XML document collections, since XML is becoming widely popular. Using the Oracle8i Extensibility Framework we will demonstrate 1) the ability to define domain operators with user-defined cost and selectivity functions, 2) the ability to define domain-specific indexing schemes, 3) the ability to specify user-defined index cost and statistics collection functions, 4) the ability to optimize queries involving domain operators via userdefined optimizer functions and 5) the ability to execute queries via domain indexes."
"As XML seems to become the preferred candidate language for the interchange of data on the Internet, the integration of distributed, heterogeneous, and autonomous XML data sources in a mediation architecture is becoming a critical issue. In this paper, we present a novel and original query rewriting algorithm for the answering of queries to XML disparate sources in the presence of XML keys. The algorithm combines features of the MiniCon (Mini-Con descriptions) and the Styx algorithms (prefix and suffix queries) into an algorithm that returns more rewritings."
"To overcome current bottlenecks in business-to-business (B2B) electronic commerce, we need intelligent solutions for mechanizing the process of structuring, standardizing, aligning and personalizing data. This article surveys the overall content management process and discusses requirements for its scalable support."
"LOPiX is an implementation of XPathLog [May01b], an XML/XPath-native, rule-based programming language for manipulation and integration of XML documents. The main syntactical constructs are XPath expressions, extended with variables. Due to the close relationship with XPath, the semantics of rules is easy to grasp. In contrast to other approaches, the XPath syntax and semantics is also used for a declarative specification how the database should be updated: when used in rule heads, XPath filters are interpreted as specifications of elements and properties which should be added to the database. The LoPiX system provides an implementation of XPathLog tailored to data integration, using a suitable graph-based data model. It extends the pure XPathLog language with schema information obtained from DTDs, a class concept, data-driven Web access and export functionality and data integration functionality [May01c] such as element fusion, synonyms, and tree view projections of the internal database. Binaries of LOPiX together with a detailed paper on XPathLog can be found at [LoP]."
"As improvements in processor performance continue to far outpace improvements in storage performance, I/O is increasingly the bottleneck in computer systems, especially in large database systems that manage huge amoungs of data. The key to achieving good I/O performance is to thoroughly understand its characteristics. In this article we present a comprehensive analysis of the logical I/O reference behavior of the peak productiondatabase workloads from ten of the world's largest corporations. In particular, we focus on how these workloads respond to different techniques for caching, prefetching, and write buffering. Our findings include several broadly applicable rules of thumb that describe how effective the various I/O optimization techniques are for the production workloads. For instance, our results indicate that the buffer pool miss ratio tends to be related to the ratio of buffer pool size to data size by an inverse square root rule. A similar fourth root rule relates the write miss ratio and the ration of buffer pool size to data size. In addition, we characterize the reference characteristics of workloads similar to the Transaction Processing Performance Council (TPC) benchmarks C (TPC-C) and D(TPC-D), which are de facto standard performance measures for online transaction processing (OLTP) systems and decision support systems (DSS), respectively. Since benchmarks such as TPC-C and TPC-D can only be used effectively if their strengths and limitations are understood, a major focus of our analysis is to identify aspects of the benchmarks that stress the system differently than the production workloads. We discover that for the most part, the reference behavior of TPC-C and TPC-D fall within the range of behavior exhibited by the production workloads. However, there are some noteworthy exceptions that affect well-known I/O optimization techniques such as caching (LRU is further from the optimal for TPC-C, while there is little sharing of pages between transactions for TPC-D), prefetching (TPC-C exhibits no significant sequentiality), and write buffering (write buffering is lees effective for the TPC benchmarks). While the two TPC benchmarks generally complement one another in reflecting the characteristics of the production workloads, there remain aspects of the real workloads that are not represented by either of the benchmarks."
"Relational database systems have traditionally optimzed for I/O performance and organized records sequentially on disk pages using the N-ary Storage Model (NSM) (a.k.a., slotted pages). Recent research, however, indicates that cache utilization and performance is becoming increasingly important on modern platforms. In this paper, we first demonstrate that in-page data placement is the key to high cache performance and that NSM exhibits low cache utilization on modern platforms. Next, we propose a new data organization model called PAX (Partition Attributes Across), that significantly improves cache performance by grouping together all values of each attribute within each page. Because PAX only affects layout inside the pages, it incurs no storage penalty and does not affect I/O behavior. According to our experimental results, when compared to NSM (a) PAX exhibits superior cache and memory bandwidth utilization, saving at least 75% of NSM¡¯s stall time due to data cache accesses, (b) range selection queries and updates on memoryresident relations execute 17-25% faster, and (c) TPC-H queries involving I/O execute 11-48% faster."
"Publisher Summary  This chapter presents the first XPath query evaluation algorithm that runs in polynomial time with respect to the size of both the data and of the query. XPath has been proposed by the W3C as a practical language for selecting nodes from XML document trees. XPath is important because of its potential application as an XML query language per se, it being at the core of several other XML-related technologies, such as XSLT, XPointer, and XQuery, and the great and well-deserved interest such technologies receive. Since XPath and related technologies will be tested in ever-growing deployment scenarios, its implementations need to scale well both with respect to the size of the XML data and the growing size and intricacy of the queries (usually referred to as combined complexity)."
"This paper describes the XSB system, and its use as an in-memory deductive database engine. XSB began from a Prolog foundation, and traditional Prolog systems are known to have serious deficiencies when used as database systems. Accordingly, XSB has a fundamental bottom-up extension, introduced through tabling (or memoing)[4], which makes it appropriate as an underlying query engine for deductive database systems. Because it eliminates redundant computation, the tabling extension makes XSB able to compute all modularly stratified datalog programs finitely and with polynomial data complexity. For non-stratified programs, a meta-interpreter with the same properties is provided. In addition XSB significantly extends and improves the indexing capabilities over those of standard Prolog. Finally, its syntactic basis in HiLog [2], lends it flexibility for data modelling. The implementation of XSB derives from the WAM [25], the most common Prolog engine. XSB inherits the WAM's efficiency and can take advantage of extensive compiler technology developed for Prolog. As a result, performance comparisons indicate that XSB is significantly faster than other deductive database systems for a wide range of queries and stratified rule sets. XSB is under continuous development, and version 1.3 is available through anonymous ftp."
"The goal of the InfoSleuth project at MCC is to exploit and synthesize new technologies into a unified system that retrieves and processes information in an ever-changing network of information sources. InfoSleuth has its roots in the Carnot project at MCC, which specialized in integrating heterogeneous information bases. However, recent emerging technologies such as internetworking and the World Wide Web have significantly expanded the types, availability, and volume of data available to an information management system. Furthermore, in these new environments, there is no formal control over the registration of new information sources, and applications tend to be developed without complete knowledge of the resources that will be available when they are run. Federated database projects such as Carnot that do static data integration do not scale up and do not cope well with this ever-changing environment. On the other hand, recent Web technologies, based on keyword search engines, are scalable but, unlike federated databases, are incapable of accessing information based on concepts. In this experience paper, we describe the architecture, design, and implementation of a working version of InfoSleuth. We show how InfoSleuth integrates new technological developments such as agent technology, domain ontologies, brokerage, and internet computing, in support of mediated interoperation of data and services in a dynamic and open environment. We demonstrate the use of information brokering and domain ontologies as key elements for scalability."
"When an XML document conforms to a given type (e.g. a DTD or an XML Schema type) it is called a valid document. Checking if a given XML document is valid is called the validation problem, and is ty..."
"We discuss the main methodological and technological issues arosen in the last years in the development of the enterprise integrated database of Telecom Italia and, subsequently in the management of the primary data store for Telecom Italia data warehouse applications. The two efforts, although driven by different needs and requirements can be regarded as a continous development of an integrated view of the enterprise data. We review the experience accumulated in the integration of over 50 internal databases, highlighting the benefits and drawbacks of this scenario for data warehousing and discuss the development of a large dedicated data store to support the analysis of data about customers and phone traffic."
"B+-Trees have been traditionally optimized for I/O performance with disk pages as tree nodes. Recently, researchers have proposed new types of B+-Trees optimized for CPU cache performance in main memory environments, where the tree node sizes are one or a few cache lines. Unfortunately, due primarily to this large discrepancy in optimal node sizes, existing disk-optimized B+-Trees suffer from poor cache performance while cache-optimized B+-Trees exhibit poor disk performance. In this paper, we propose fractal prefetching B+-Trees (fpB+-Trees), which embed ""cache-optimized"" trees within ""disk-optimized"" trees, in order to optimize both cache and I/O performance. We design and evaluate two approaches to breaking disk pages into cache-optimized nodes: disk-first and cache-first. These approaches are somewhat biased in favor of maximizing disk and cache performance, respectively, as demonstrated by our results. Both implementations of fpB+-Trees achieve dramatically better cache performance than disk-optimized B+-Trees: a factor of 1.1-1.8 improvement for search, up to a factor of 4.2 improvement for range scans, and up to a 20-fold improvement for updates, all without significant degradation of I/O performance. In addition, fpB+-Trees accelerate I/O performance for range scans by using jump-pointer arrays to prefetch leaf pages, thereby achieving a speed-up of 2.5-5 on IBM's DB2 Universal Database."
"We present new techniques for efficient garbage collection in a large persistent object store. The store is divided into partitions that are collected independently using information about inter-partition references. This information is maintained on disk so that it can be recovered after a crash. We use new techniques to organize and update this information while avoiding disk accesses. We also present a new global marking scheme to collect cyclic garbage across partitions. Global marking is piggybacked on partitioned collection; the result is an efficient scheme that preserves the localized nature of partitioned collection, yet is able to collect all garbage. We have implemented the part of garbage collection responsible for maintaining information about inter-partition references. We present a performance study to evaluate this work; the results show that our techniques result in substantial savings in the usage of disk and memory."
"In this article we present an approach to integrity maintenance, consisting of automatically generating production rules for integrity enforcement. Constraints are expressed as particular formulas of Domain Relational Calculus; they are automatically translated into a set of repair actions, encoded as production rules of an active database system. Production rules may be redundant (they enforce the same constraint in different ways) and conflicting (because repairing one constraint may cause the violation of another constraint). Thus, it is necessary to develop techniques for analyzing the properties of the set of active rules and for ensuring that any computation of production rules after any incorrect transaction terminates and produces a consistent database state. Along these guidelines, we describe a specific architecture for constraint definition and enforcement. "
"With about 8.000 researchers and 40.000 students, RWTH Aachen is the largest technical university in Europe. The science and engineering departments and their industrial collaborators offer a lot of challenges for database research.The chair Informatik V (Information Systems) focuses on the theoretical analysis, prototypical development, and practical evaluation of meta information systems. Meta information systems, also called repositories, document and coordinate the distributed processes of producing, integrating, operating, and evolving database-intensive applications.Our research approaches these problems from a technological and from an application perspective.On the one hand, we pursue theory and system aspects of the integration of deductive and object-oriented technologies. One outcome of this work is a deductive object manager called ConceptBase which has been developed over the past eight years and is currently used by many research groups and industrial teams throughout the world.On the other hand, a wide range of application-driven projects aims at building a sound basis of empirical knowledge about the demands on meta information systems, and about the quality of proposed solutions. "
"There is considerable overlap between strategies proposed for subquery evaluation, and those for grouping and aggregation. In this paper we show how a number of small, independent primitives generate a rich set of efficient execution strategies ¡ªcovering standard proposals for subquery evaluation suggested in earlier literature. These small primitives fall into two main, orthogonal areas: Correlation removal, and efficient processing of outerjoins and GroupBy. An optimization approach based on these pieces provides syntax-independence of query processing with respect to subqueries, i. e. equivalent queries written with or without subquery produce the same efficient plan. We describe techniques implemented in Microsoft SQL Server (releases 7.0 and 8.0) for queries containing sub-queries and/or aggregations, based on a number of orthogonal optimizations. We concentrate separately on removing correlated subqueries, also called ¡°query flattening,¡± and on efficient execution of queries with aggregations. The end result is a modular, flexible implementation, which produces very efficient execution plans. To demonstrate the validity of our approach, we present results for some queries from the TPC-H benchmark. From all published TPC-H results in the 300GB scale, at the time of writing (November 2000), SQL Server has the fastest results on those queries, even on a fraction of the processors used by other systems."
"Abstract. Data warehousing systems integrate information from operational data sources into a central repository to enable analysis and mining of the integrated information. During the integration process, source data typically undergoes a series of transformations, which may vary from simple algebraic operations or aggregations to complex ¡°data cleansing¡± procedures. In a warehousing environment, the data lineage problem is that of tracing warehouse data items back to the original source items from which they were derived. We formally define the lineage tracing problem in the presence of general data warehouse transformations, and we present algorithms for lineage tracing in this environment. Our tracing procedures take advantage of known structure or properties of transformations when present, but also work in the absence of such information. Our results can be used as the basis for a lineage tracing tool in a general warehousing setting, and also can guide  the design of data warehouses that enable efficient lineage tracing."
"Electronic commerce systems for business-to-business commerce on the Internet are still in their infancy. The realization of Internet electronic markets for business-to-business following a n-suppliers: m-customers scenario is still unattainable with todays solutions. Comprehensive Internet electronic commerce systems should provide for easy access to and handling of the system, help to overcome differences in time of business, location, language between suppliers and customers, and at the same time should support the entire process of trading for business-to-business commerce. In this paper, we present a DBMS-based electronic commerce architecture and its prototypical implementation for business-to-business commerce according to a n-suppliers: m-customers scenario. Business transactions within the electronic market are realized by a set of modular market services. Multiple physically distributed markets can be interconnected transparently to the users and form one virtually central market place. The modeling and management of all market data in a DBMS gives the system a solid basis for reliable, consistent, and secure trading on the market. The generic and modular system architecture can be applied to arbitrary application domains. The system is scalable and can cope with an increasing number of single markets, participants, and market data due to the possibility to replicate and distribute services and data and herewith to distribute data, system, and network load."
As video data is penetrating many information systems the need for database support for video data evolves. In this paper we present a generic data model that captures the structure of a video document and that provides a means for indexing a video stream. We also discuss query language features that can take advantage of the proposed model. We have identified basic operators that should be implemented in the query language to support content based queries. The paper also analyses how these operators can be used to provide video data queries. The model has been used as a basis for a television news archive prototype and some experimental results are presented.
"Conduct of scientific and engineering research is becoming critically dependent on effective management of scientific and engineering data and technical information. The rapid advances in scientific instrumentation, computer and communication technologies enable the scientists to collect, generate, process, and share unprecedented volumes of data. For example, the Earth Observing System Data and Information System (EOSDIS) has the task to manage the data from NASA¡¯s Earth science research satellites and field measurement programs, and other data essential for the interpretation of these measurements in support of global change research. Apart from being able to handle a stream of 1 terabyte of data daily by the year 2000, EOSDIS will also need to provide transparent access to heterogeneous data held in the archives of several US government agencies, organizations and countries. A single graphical user interface employing the Global Change Master Directory needs to help users locate data sets of interest among massive and diverse data sets, or find the appropriate data analysis tools, regardless of their location. Another major international effort in the area of human genome research faces some similar, as well as unique issues due to the complexity of the genome data, special querying requirements and much more heterogeneous collections of data. Scientific databases can be viewed as critical repositories of knowledge, both existing and yet to be dis-"
"Parallel database systems have to support the effective parallelization of complex queries in multi-user mode, i.e. in combination with inter-query~mter-transaction parallelism. For this purpose, dynamic scheduling and load balancing strategies¡¯ are necessary that umsider the current system state for dekrminhg the degree of intra-query parallelism and for selecting the processors for executing subqueries. We study these issues for parallel hash joinprocessing and show that the two subproblems should be addressed in au integrated way. Even more importantly, however, is the use of a multimannce load balancing approach that considers all potential bottleneck resources. in particular memory, disk and CPU. We discuss basic performance tradeoffs to consider and evalGate the performauce of several oad balancing strategies by means of a detailed simulation model. Simulation results will be analyzed for multiuser configurations with both homogeneous andheterogeneous (query/OLTP) workloads."
"Replication is often used in many distributed systems to provide a higher level of performance, reliability and availability. Lazy replica update protocols, which propagate updates to replicas through independent transactions after the original transaction commits, have become popular with database vendors due to their superior performance characteristics. However, if lazy protocols are used indiscriminately, they can result in non-serializable executions. In this paper, we propose two new lazy update protocols that guarantee serializability but impose a much weaker requirement on data placement than earlier protocols. Further, many naturally occurring distributed systems, like distributed data warehouses, satisfy this requirement. We also extend our lazy update protocols to eliminate all requirements on data placement. The extension is a hybrid protocol that propagates as many updates as possible in a lazy fashion. We implemented our protocols on the Datablitz database system product developed at Bell Labs. We also conducted an extensive performance study which shows that our protocols outperform existing protocols over a wide range of workloads."
"A unifying model for the study of database performance is proposed. Applications of the model are shown to relate and extend important work concerning batched searching, transposed files, index selection, dynamic hash-based files, generalized access path structures, differential files, network databases, and multifile query processing."
"Intrusion detection has become a critical component of network administration due to the vast number of attacks persistently threaten our computers. Traditional intrusion detection systems are limited and do not provide a complete solution for the problem. They search for potential malicious activities on network traffics; they sometimes succeed to find true security attacks and anomalies. However, in many cases, they fail to detect malicious behaviours (false negative) or they fire alarms when nothing wrong in the network (false positive). In addition, they require exhaustive manual processing and human expert interference. Applying Data Mining (DM) techniques on network traffic data is a promising solution that helps develop better intrusion detection systems. Moreover, Network Behaviour Analysis (NBA) is also an effective approach for intrusion detection. In this paper, we discuss DM and NBA approaches for network intrusion detection and suggest that a combination of both approaches has the potential to detect intrusions in networks more effectively."
"We present MOCHA, a new self-extensible database middleware system designed to interconnect distributed data sources. MOCHA is designed to scale to large environments and is based on the idea that some of the user-defined functionality in the system should be deployed by the middleware system itself. This is realized by shipping Java code implementing either advanced data types or tailored query operators to remote data sources and have it executed remotely. Optimized query plans push the evaluation of powerful data-reducing operators to the data source sites while executing data-inflating operators near the client's site. The Volume Reduction Factor is a new and more explicit metric introduced in this paper to select the best site to execute query operators and is shown to be more accurate than the standard selectivity factor alone. MOCHA has been implemented in Java and runs on top of Informix and Oracle. We present the architecture of MOCHA, the ideas behind it, and a performance study using scientific data and queries. The results of this study demonstrate that MOCHA provides a more flexible, scalable and efficient framework for distributed query processing compared to those in existing middleware solutions."
"Probability theory is mathematically the best understood paradigm for modeling and manipulating uncertain information. Probabilities of complex events can be computed from those of basic events on which they depend, using any of a number of strategies. Which strategy is appropriate depends very much on the known interdependencies among the events involved. Previous work on probabilistic databases has assumed a fixed and restrictivecombination strategy (e.g., assuming all events are pairwise independent). In this article, we characterize, using postulates, whole classes of strategies for conjunction, disjunction, and negation, meaningful from the viewpoint of probability theory. (1) We propose a probabilistic relational data model and a genericprobabilistic relational algebra that neatly captures various strategiessatisfying the postulates, within a single unified framework. (2) We show that as long as the chosen strategies can be computed in polynomial time, queries in the positive fragment of the probabilistic relational algebra have essentially the same data complexity as classical relational algebra. (3) We establish various containments and equivalences between algebraic expressions, similar in spirit to those in classical algebra. (4) We develop algorithms for maintaining materialized probabilistic views. (5) Based on these ideas, we have developed a prototype probabilistic database system called ProbView on top of Dbase V.0. We validate our complexity results with experiments and show that rewriting certain types of queries to other equivalent forms often yields substantial savings."
"As Internet traffic continues to grow and web sites become increasingly complex, performance and scalability are major issues for web sites. Web sites are increasingly relying on dynamic content generation applications to provide web site visitors with dynamic, interactive, and personalized experiences. However, dynamic content generation comes at a cost --- each request requires computation as well as communication across multiple components.To address these issues, various dynamic content caching approaches have been proposed. Proxy-based caching approaches store content at various locations outside the site infrastructure and can improve Web site performance by reducing content generation delays, firewall processing delays, and bandwidth requirements. However, existing proxy-based caching approaches either (a) cache at the page level, which does not guarantee that correct pages are served and provides very limited reusability, or (b) cache at the fragment level, which requires the use of pre-defined page layouts. To address these issues, several back end caching approaches have been proposed, including query result caching and fragment level caching. While back end approaches guarantee the correctness of results and offer the advantages of fine-grained caching, they neither address firewall delays nor reduce bandwidth requirements.In this paper, we present an approach and an implementation of a dynamic proxy caching technique which combines the benefits of both proxy-based and back end caching approaches, yet does not suffer from their above-mentioned limitations. Our dynamic proxy caching technique allows granular, proxy-based caching where both the content and layout can be dynamic. Our analysis of the performance of our approach indicates that it is capable of providing significant reductions in bandwidth. We have also deployed our proposed dynamic proxy caching technique at a major financial institution. The results of this implementation indicate that our technique is capable of providing order-of-magnitude reductions in bandwidth and response times in real-world dynamic Web applications."
"Data warehouses are repositories that integrate and relational and non-relational data stores. Because summarize historical and reference data from numerous the warehouse integrates¡¯ gateways and distributed sources. Warehoused data can be analyzed along several SQL processing, the warehoe cq load data from dimensions such as time, product, and geography to ari ¡®opeiational system with an SQL imerf...seZecf identify trends and gain competitive advantage. statement."
"Relational databases supported applications in a centralized environment in the 1960's and 1970's. They progressed to a client/server environment in the 1980's. The 1990's saw application servers with a multi-tiered architecture, in most cases supported by an RDBMS. Most recently we have seen the emergence of XML, XML storage in DBMS's, navigation within an XML document via XPath, and the XQuery query language for XML. In this article, Susan provides an introduction to the Grid and describes how databases will be used in this new environment. The Global Grid Forum (GGF) is producing technical specification to enable both Relational and XML databases to be located, accessed, and replicated in this environment. They make use of a variety of existing an emerging database, file, networking, and web services standards. "
"In this paper, we first introduce the database aspects of the groupware product Lotus Domino/Notes and then describe, in some more detail, many of the logging and recovery enhancements that were introduced in R5. We discuss briefly some of the changes that had to be made to the ARIES recovery method to accommodate the unique storage management characteristics of Notes. We also outline some of the on-going logging and locking work in the Dominotes project at the IBM Almaden Research Center."
"Similarity search is a very important operation in multimedia databases and other database applications involving complex objects, and involves finding objects in a data set S similar to a query object q, based on some similarity measure. In this article, we focus on methods for similarity search that make the general assumption that similarity is represented with a distance metric d. Existing methods for handling similarity search in this setting typically fall into one of two classes. The first directly indexes the objects based on distances (distance-based indexing), while the second is based on mapping to a vector space (mapping-based approach). The main part of this article is dedicated to a survey of distance-based indexing methods, but we also briefly outline how search occurs in mapping-based methods. We also present a general framework for performing search based on distances, and present algorithms for common types of queries that operate on an arbitrary ""search hierarchy."" These algorithms can be applied on each of the methods presented, provided a suitable search hierarchy is defined."
This article describes a novel way of combining data mining techniques on Internet data in order to discover actionable marketing intelligence in electronic commerce scenarios. The data that is con...
"Compensation-based query processing has been proposed in order to avoid lock contention between updating transactions and ad-hoc queries. This paper presents an algorithm based on undo /no-redo compensation. A query will read an inconsistent version of the database, but updates made by concurrent transactions are later undone to make the query result transaction-consistent. By processing the database internal log to obtain information on concurrent updates, queries impose no extra work on updating transactions. A simulation study shows that response times for query execution is significantly improved compared to the earlier compensation-based algorithms. Compared to executing queries with no consistency requirements, the algorithm gives only a small increase in query response times, while the effects on transaction response times are negligible. "
"Editor's note: For this issue's ""From the Editors,"" I invited Robert Gephart of the University of Al-berta to reflect on his observations as a long-serving , award-winning reviewer of qualitative research for A!vII Over the past two and a half years, I have developed a tremendous respect for Bob's keen eye for evaluating qualitative research submissions , and great admiration for the painstaking advice he provides authors about how to improve their work. As a world-renowned qualitative author himself, Bob is in an excellent position to provide observations about how authors might increase the chances of having their qualitative research accepted for publication at AMI In a three-way electronic mail conversation about the challenges and opportunities of qualitative research , Bob, Tom Lee, and I all concluded that many authors with potentially very interesting data sets don't seem to know how to analyze them to their full potential. This is perhaps not surprising, gi ven the clear predominance of quantitative methods and statistics courses over qualitative ones, particularly in North America, as well as the inherently greater subjectivity involved in designing and analyzing qualitative research. As such, we encouraged Bob to provide a bit of a minitutorial-complete with reference citations and examples of high-quality papers that use particular qualitative approaches-in addition to his observations about qualitative research submitted to AMI The result is a longer-than-usual ""From the Edi-tors"" column. but one that we believe is well worth the extra reading time for anyone interested in producing , reviewing, or attempting to coax greater insights from qualitative research. We are fortunate to have someone with Bob's expertise share his observations, and we hope that his thoughts will prove useful to researchers for many years to come. "
"The information available on the internet is growing at very high rate. Especially, news articles are added and updated round-the-clock. News retrieval systems which are in use today, are not very much capable of handling such huge amounts of news articles effectively and accurately. Due to the need for frequent and intensive processing, a news retrieval system needs to be scalable, robust and fault tolerant. By the use of Cloud technology, this can achieved. A news retrieval system on the cloud can be used to fetch, process, organize and also be used for faster and accurate retrieval. It can be made to operate with less supervision or none at all. Cloud Press, a next generation news retrieval system presented here, is designed and implemented, to overcome most of the pit falls of the news retrieval systems, which are in place today. It uses MapReduce paradigm for fetching, processing and organizing all the news articles in a distributed fashion. MapReduce approach allows it to split the tasks into sub-tasks and then allows them to be assigned to various nodes present in the cloud, which are then finished and consolidated to give one final output. "
"We present the BHUNT scheme for automatically discovering algebraic constraints between pairs of columns in relational data. The constraints may be ""fuzzy"" in that they hold for most, but not all, of the records, and the columns may be in the same table or different tables. Such constraints are of interest in the context of both data mining and query optimization, and the BHUNT methodology can potentially be adapted to discover fuzzy functional dependencies and other useful relationships. BHUNT first identifies candidate sets of column value pairs that are likely to satisfy an algebraic constraint. This discovery process exploits both system catalog information and data samples, and employs pruning heuristics to control processing costs. For each candidate, BHUNT constructs algebraic constraints by applying statistical histogramming, segmentation, or clustering techniques to samples of column values. Using results from the theory of tolerance intervals, the sample sizes can be chosen to control the number of ""exception"" records that fail to satisfy the discovered constraints. In query-optimization mode, BHUNT can automatically partition the data into normal and exception records. During subsequent query processing, queries can be modified to incorporate the constraints; the optimizer uses the constraints to identify new, more efficient access paths. The results are then combined with the results of executing the original query against the (small) set of exception records. Experiments on a very large database using a prototype implementation of BHUNT show reductions in table accesses of up to two orders of magnitude, leading to speedups in query processing by up to a factor of 6.8."
"Data in relational databases is frequently stored and retrieved using B-Trees. In &cis,ion isugprt applications the key of the B-Tree frequently involves the concatenation of several fields of the relationdl¡¯ table. During retrieval, it is desirable to be able to access a small subset of the table based¡¯ on partial key information, where some fields of the key may either not be present, involve ranges, or lists ¡®of values. It is also advantageous to altow. this type, of access-with gen&il expressions involving any combination of disjuncts on key columns. This paper &scribes a method whereby BTrees can be eficiently used to retrieve small subsets, thus avoiding large scans of potentially huge tables. Another benefit is the ability of this method to reduce the need for additional secondary indexes, thus saving space, maintenance cost, and random accesses."
"This paper describes security issues for federated database management systems set up for managing distributed, heterogeneous and autonomous multilevel databases. It builds on our previous work in multilevel secure distributed database management systems and on the results of others' work in federated database systems. In particular, we define a multilevel secure federated database system and discuss issues on heterogeneity, autonomy, security policy and architecture."
"We describe the use of parallel execution techniques and measure the price of parallel execution in NonStop SQL/MP, a commercial parallel database system from Tandem Computers. Non-Stop SQL uses intra-operator parallelism to parallelize joins, groupings and scans. Parallel execution consists of starting up several processes and communicating data between them. Our measurements show (a) Startup costs are negligible when processes are reused rather than created afresh (b) Communication costs are significant ¡ª they may exceed the costs of operators such as scan, grouping or join. We also show two counter-examples to the common intuition that parallel execution reduces response time at the expense of increased work ¡ª parallel execution may reduce work or may increase response time depending on communication costs."
"As the telecommunications industry endeavours to reinvent itself, the effective management and exploitation of information, data delivered in context, is now the key weapon in gaining and retaining customers. The data management challenges in an environment of massively growing data volumes and complexity introduced by distributed processing are outlined. A framework and methodology for the management of information is presented and the term Context Data is introduced."
"In a mobile computing system, caching data items at the mobile clients is important to reduce the data access delay in an unreliable and low bandwidth mobile network. However, efficient methods must be used to ensure the coherence between the cached items and the data items at the database server. By exploring the real time properties of the data items, we propose a cache invalidation scheme called: Invalidation by Absolute Validity Interval (IAVI). We define an absolute validate interval (AVI) for each data item based on its real time property, e.g. update interval. A mobile client can verify the validity of a cached item by comparing the last update time and its AVI. A cached item is invalidated if the current time is greater than the last update time by its AVI. With this self-invalidation mechanism, the IAVI scheme uses the invalidation report to inform the mobile clients about the change of AVI rather than the update event of the data item. As a result, the size of invalidation report can be reduced significantly. Performance studies show that the IAVI scheme can significantly reduce the mean response time and invalidation report size under various system parameters."
"New types of data processing applications are no longer satisfied with the capabilities offered by the relational data model. One example of this phenomenon is the growing use of the Internet as a source of data. The data on the Internet is inherently non-relational. As a result, demand developed for database management systems natively built on advanced data models. The semantic binary data model (Rishe, 1992), satisfies the criteria for the models required for today¡¯s applications by providing the ability to build rich schemas with arbitrarily flexible relationships between objects. In this paper, we discuss a new design for a semantic database management system which is based on the semantic binary data model. Our challenge was to design and implement a database engine which, while being native to the model, is reasonably efficient on a wide variety of industrial applications, and which surpasses relational systems in performance and flexibility on those applications that require non-relational modelling. Special attention is given to multi-platform support by the semantic database engine."
"The traditional approach to relational database design is based on the logical organization of data into a number of related normalized tables. One assumption is that the nature and structure of the data is known at the design stage. In the case of designing a relational database to store historical dental epidemiological data from individual clinical surveys, the structure of the data is not known until the data is presented for inclusion into the database. This paper addresses the issues concerned with the theoretical design of a clinical dynamic database capable of adapting the internal table structure to accommodate clinical survey data, and presents a prototype database application capable of processing, displaying, and querying the dental data."
"In outsourced database (ODB)systems the database owner publishes its data through a number of remote servers, with the goal of enabling clients at the edge of the network to access and query the data more efficiently. As servers might be untrusted or can be compromised, query authentication becomes an essential component of ODB systems. Existing solutions for this problem concentrate mostly on static scenarios and are based on idealistic properties for certain cryptographic primitives. In this work, first we define a variety of essential and practical cost metrics associated with ODB systems. Then, we analytically evaluate a number of different approaches, in search for a solution that best leverages all metrics. Most importantly, we look at solutions that can handle dynamic scenarios, where owners periodically update the data residing at the servers. Finally, we discuss query freshness, a new dimension in data authentication that has not been explored before. A comprehensive experimental evaluation of the proposed and existing approaches is used to validate the analytical models and verify our claims. Our findings exhibit that the proposed solutions improve performance substantially over existing approaches, both for static and dynamic environments."
"Publisher Summary  The Hippocratic Oath has guided the conduct of physicians for centuries. Inspired by its tenet of preserving privacy, it has been argued that future database systems must include responsibility for the privacy of data that they manage as a founding tenet. The explosive progress in networking, storage, and processor technologies is resulting in an unprecedented amount of digitization of information. It is estimated that the amount of information in the world is doubling every 20 months, and the size and number of databases are increasing even faster. In concert with this dramatic and escalating increase in digital data, concerns about the privacy of personal information have emerged globally. Privacy issues have been further exacerbated, now that the Internet makes it easy for new data to be automatically collected and added to databases. Privacy is the fight of individuals to determine for themselves when, how, and to what extent information about them is communicated to others. Privacy concerns are being fueled by an ever-increasing list of privacy violations, ranging from privacy accidents to illegal actions. Lax security for sensitive data is of equal concern."
"Database replication is traditionally seen as a way to increase the availability and performance of distributed databases. Although a large number of protocols providing data consistency and fault-tolerance have been proposed, few of these ideas have ever been used in commercial products due to their complexity and performance implications. Instead, current products allow inconsistencies and often resort to centralized approaches which eliminates some of the advantages of replication. As an alternative, we propose a suite of replication protocols that addresses the main problems related to database replication. On the one hand, our protocols maintain data consistency and the same transactional semantics found in centralized systems. On the other hand, they provide flexibility and reasonable performance. To do so, our protocols take advantage of the rich semantics of group communication primitives and the relaxed isolation guarantees provided by most databases. This allows us to eliminate the possibility of deadlocks, reduce the message overhead and increase performance. A detailed simulation study shows the feasibility of the approach and the flexibility with which different types of bottlenecks can be circumvented."
"We map an object model to a commercial relational multi-processor database system using replication and view materialisation to provide fast retrieval. To speed up complex update operations, we exploit intra-transaction parallelism by breaking such an operation down into shorter relational operations which are executed as parallel subtransactions of the update transaction. To ensure the correctness and recoverability of the operation¡¯s execution, we use multi-level transactions. In addition, we minimise the resulting overhead for the logging of the compensating inverse operation required by the multi-level concept by logging the compensation for non-derived data only. In particular, we concentrate on the novel application of multi-level transaction management to efficiently maintain the replicated data and materialised views. We present a prototype implementation and give a performance evaluation of an exemplary set-oriented update statement."
"Traditionally, databases have stored textual data and have been used to store administrative information. The computers used. and more specifically the storage available, have been neither large enough nor fast enough to allow databases to be used for more technical applications. In recent years these two bottlenecks have started to di sappear and there is an increasing interest in using databases to store non-textual data like sensor measurements or other types of process-related data. In a database a sequence of sensor measurements can be represented as a time series. The database can then be queried to find, for instance, subsequences, extrema points, or the points in time at which the time series had a specific value. To make this search efficient, indexing methods are required. Finding appropriate indexing methods is the focus of this thesis.There are two major problems with existing time series indexing strategies: the size of the index structures and the lack of general indexing strategies that are application independent. These problems have been thoroughly researched and solved in the case of text indexing files. We have examined the extent to which text indexing methods can be used for indexing time series.A method for transforming time series into text sequences has been investigated. An investigation was then made on how text indexing methods can be applied on these text sequences. We have examined two well known text indexing methods: the signature files and the B-tree. "
Semantic B2B Integration architectures must enable enterprises to communicate standards-based B2B events like purchase orders with any potential trading partner. This requires not only back end app...
"Environmental Management Information Systems (EMIS) are socio-technological systems used as business applications to gather, process, and provide environmental information, inside companies and in exchange with other actors in industry. They help to identify environmental impacts and support measures avoiding these impacts or reducing them. EMIS provide the necessary information support for decision making in companies. Hence, EMIS can be viewed as certain Information Systems (IS) usually implemented in companies as a part of their Environmental Management Systems (EMS). In order to give a tangible example with practical implications, the developments that EMIS have passed the last years are described along the field of ¡°online communication and sustainability reporting¡± and illustrated by a case study. This area represents an emerging digital and fully ICT (information and communication technologies) supported approach within EMIS, using current internet technologies and services. It makes clear the array of capabilities of latest EMIS to be exploited for the improvement of advanced environmental and sustainability management, finally to the benefit for companies and their various stakeholders. The case study describes the concept and implementation of a software tool with shopping cart functionality providing sustainability reports a la carte so that stakeholders (i.e. users, readers) can create their own report on the fly, exactly meeting their detailed information needs and preferred media out from a single publishing database. This software tool which represents a module of a comprehensive EMIS is implemented as a web-based ICT application. Its performance goes beyond the leadingedge approach of O2 who provides a personalized reporting feature on its website that could be regarded as best practice and pioneering effort in sustainability online reporting, so far."
"SQL Server 7.0 offers three different styles of replication that we call Transactional Replication, Snapshot Replication, and Merge Replication. Merge Replication means that data changes can be performed at any replica, and that the changes performed at multiple replicas are later merged together. Because Merge Replication allows updates to disconnected replicas, it is particularly well suited to applications that require a lot of autonomy. A special process called the Merge Agent propagates changes between replicas, filters data as appropriate, and detects and handles conflicts according to user-specified rules."
"QURSED enables the development of web-based query forms and reports (QFRs) that query and report semistructured XML data, i.e., data that are characterized by nesting, irregularities and structural variance. The query aspects of a QFR are captured by its query set specification, which formally encodes multiple parameterized condition fragments and can describe large numbers of queries. The run-time component of QURSED produces XQuery-compliant queries by synthesizing fragments from the query set specification that have been activated during the interaction of the end-user with the QFR. The design-time component of QURSED, called QURSED Editor, semi-automates the development of the query set specification and its association with the visual components of the QFR by translating visual actions into appropriate query set specifications. We describe QURSED and illustrate how it accommodates the intricacies that the semistructured nature of the underlying database introduces. We specifically focus on the formal model of the query set specification, its generation via the QURSED Editor and its coupling with the visual aspects of the web-based form and report."
"Global E-Commerce and E-Governance programs have brought into sharp focus for the need of database systems to store and manipulate data efficiently in a suite of multiple languages. While existing database systems provide some means of storing and querying multilingual data, they suffer from redundancy proportional to the number of language support. In this paper, we propose a system for multilingual data management in distributed environment that stores data in information theoretic way in encoded form with minimum redundancy. Query operation can be performed from the encoded data only and the result is obtained by decompressing it using the corresponding language dictionaries for text data or without dictionary for other data. The system has been evaluated by both syntactic data and real data obtained from a real life schema. We have compared the performance of our system with existing systems. Our system outperformed the existing systems in terms of both space and time."
"With the current explosion of information on the World Wide Web (WWW) a wealth of information on many different subjects has become available on-line. Numerous sources contain information that can be classified as semi-structured. At present, however, the only way to access the information is by browsing individual pages. We cannot query web documents in a database-like fashion based on their underlying structure. However, we can provide database-like querying for semi-structured WWW sources by building wrappers around these sources. We present an approach for semi-automatically generating such wrappers. The key idea is to exploit the formatting information in pages from the source to hypothesize the underlying structure of a page. From this structure the system generates a wrapper that facilitates querying of a source and possibly integrating it with other sources. We demonstrate the ease with which we are able to build wrappers for a number of internet sources in different domains using our implemented wrapper generation toolkit."
"This paper introduces a shape-based similarity measure, called the angular metric for shape similarity (AMSS), for time series data. Unlike most similarity or dissimilarity measures, AMSS is based not on individual data points of a time series but on vectors equivalently representing it. AMSS treats a time series as a vector sequence to focus on the shape of the data and compares data shapes by employing a variant of cosine similarity. AMSS is, by design, expected to be robust to time and amplitude shifting and scaling, but sensitive to short-term oscillations. To deal with the potential drawback, ensemble learning is adopted, which integrates data smoothing when AMSS is used for classification. Evaluative experiments reveal distinct properties of AMSS and its effectiveness when applied in the ensemble framework as compared to existing measures."
"The chair of ACRP¡¯s Association Board of Trustees recounts how he left manufacturing and research and development a decade ago to take a position as a clinical research administrator. It was a move that place him into a role he knew little about, having not been engaged in clinical research beforehand. If this sounds like a familiar experience to others, the lessons shared in this column highlight the importance of the individual¡¯s ongoing will to learn, and of organizational support for that learning."
"A data mining system, DBMiner, has been developed for interactive mining of multiple-level knowledge in large relational databases. The system implements a wide spectrum of data mining functions, including generalization, characterization, association, classification, and prediction. By incorporating several interesting data mining techniques, including attribute-oriented induction, statistical analysis, progressive deepening for mining multiple-level knowledge, and meta-rule guided mining, the system provides a user-friendly, interactive data mining environment with good performance."
"We investigate the problem of using materialized views to answer SQL queries. We focus on modern decision-support queries, which involve joins, arithmetic operations and other (possibly user-defined) functions, aggregation (often along multiple dimensions), and nested subqueries. Given the complexity of such queries, the vast amounts of data upon which they operate, and the requirement for interactive response times, the use of materialized views (MVs) of similar complexity is often mandatory for acceptable performance. We present a novel algorithm that is able to rewrite a user query so that it will access one or more of the available MVs instead of the base tables. The algorithm extends prior work by addressing the new sources of complexity mentioned above, that is, complex expressions, multidimensional aggregation, and nested subqueries. It does so by relying on a graphical representation of queries and a bottom-up, pair-wise matching of nodes from the query and MV graphs. This approach offers great modularity and extensibility, allowing for the rewriting of a large class of queries."
"We briefly outline the main characteristics of an efficient server-based algorithm for garbage collecting object-oriented databases in a client-server environment. The algorithm is incremental and runs concurrently with client transactions. Unlike previous algorithms, it does not hold any locks on data and does not require callbacks to clients. It is fault tolerant, but performs very little logging. The algorithm has been designed to be integrated into existing OODB systems, and therefore it works with standard implementation techniques such as two-phase locking and write-ahead-logging. In addition, it supports client-server performance optimizations such as client caching and flexible management of client buffers. The algorithm has been implemented in the EXODUS storage manager before being evaluated. "
"Web caching is a technology to improve network tra-c on the Internet. It is a temporary storage of Web objects for later retrieval. Three signiflcant ad- vantages of Web caching include reduction in bandwidth consumption, server load, and latency. These advantages make the Web to be less expensive yet it provides better performance. This research aims to introduce an advanced machine learning method for a classiflcation problem in Web caching that requires a decision to cache or not to cache Web objects in a proxy cache server. The challenges in this clas- siflcation problem include the issues in identifying attributes ranking and improve the classiflcation accuracy signiflcantly. This research includes four methods that are Classiflcation and Regression Trees (CART), Multivariate Adaptive Regression Splines (MARS), Random Forest (RF) and TreeNet (TN) for classiflcation on Web caching. The experimental results reveal that CART performed extremely well in classifying Web objects from the existing log data with a size of Web objects as a signiflcant attribute for Web cache performance enhancement."
"Data mining services require accurate input data for their results to be meaningful, but privacy concerns may influence users to provide spurious information. We investigate here, with respect to mining association rules, whether users can be encouraged to provide correct information by ensuring that the mining process cannot, with any reasonable degree of certainty, violate their privacy. We present a scheme, based on probabilistic distortion of user data, that can simultaneously provide a high degree of privacy to the user and retain a high level of accuracy in the mining results. The performance of the scheme is validated against representative real and synthetic datasets."
"A model is a formal description of a complex application artifact, such as a database schema, an application interface, a UML model, an ontology, or a message format. The problem of merging such models lies at the core of many meta data applications, such as view integration, mediated schema creation for data integration, and ontology merging. This paper examines the problem of merging two models given correspondences between them. It presents requirements for conducting a merge and a specific algorithm that subsumes previous work."
"This book presents methods for spatial data modeling, algorithms, access methods, and query processing. The main focus is on extending DBMS technology to accommodate spatial data. The book also includes spatial methods used in Geographic Information Systems (GISs). Historically, GISs developed separately from Database systems. GISs are specialized in all aspects of spatial data handling including spatial editing, re-projecting coordinate systems, and map display. However, their query abilities generally are limited or require low-level programming. Contrary to GIS software is the approach to include spatial data in DBMSs using ADTs and extensibility. "
"We consider the problem of substring searching in large databases. Typical applications of this problem are genetic data, web data, and event sequences. Since the size of such databases grows exponentially, it becomes impractical to use inmemory algorithms for these problems. In this paper, we propose to map the substrings of the data into an integer space with the help of wavelet coefficients. Later, we index these coefficients using MBRs (Minimum Bounding Rectangles). We define a distance function which is a lower bound to the actual edit distance between strings. We experiment with both nearest neighbor queries and range queries. The results show that our technique prunes significant amount of the database (typically 50-95%), thus reducing both the disk I/O cost and the CPU cost significantly ."
"The problem of answering queries using views is to find efficient methods of answering a query using a set of previously defined materialized views over the database, rather than accessing the database relations. The problem has recently received significant attention because of its relevance to a wide variety of data management problems. In query optimization, finding a rewriting of a query using a set of materialized views can yield a more efficient query execution plan. To support the separation of the logical and physical views of data, a storage schema can be described using views over the logical schema. As a result, finding a query execution plan that accesses the storage amounts to solving the problem of answering queries using views. Finally, the problem arises in data integration systems, where data sources can be described as precomputed views over a mediated schema. This article surveys the state of the art on the problem of answering queries using views, and synthesizes the disparate works into a coherent framework. We describe the different applications of the problem, the algorithms proposed to solve it and the relevant theoretical results."
"SEMCOG Approach We argue that image retrieval based on either approach alone is not sufficient in terms of modeling and query specification flexibility y. We also argue that a visual query interface which is capability of visualizing target images is essential. SEMCOG[l] (SEMantics and COGnitionbased image retrieval) aims at integrating semautics and cognition-based approaches to give users a greater flexibility to pose queries. SEMCOG¡¯S image matching is based on objects in the images rather than the whole images. In SEMCOG, a query ¡°Retrieve all images in which there is a man to the right of a car and the man looks like this image¡± can be posed using combinations of semantics and visual expressions. The queries are posed in the way of specifying image objects and their layouts using a visual query interface, IFQ (In Frame Query), rather than complicated multimedia database query languages. The user¡¯s query can be simplified as a mental model shown at the top of Figure 1. "
"Aggregation along hierarchies is a critical summary technique in a large variety of on-line applications including decision support and network management (e.g., IP clustering, denial-of-service attack monitoring). Despite the amount of recent study that has been dedicated to online aggregation on sets (e.g., quantiles, hot items), surprisingly little attention has been paid to summarizing hierarchical structure in stream data.    The problem we study in this paper is that of finding Hierarchical Heavy Hitters (HHH): given a hierarchy and a fraction ¦Õ, we want to find all HHH nodes that have a total number of descendants in the data stream no smaller than ¦Õ of the total number of elements in the data stream, after discounting the descendant nodes that are HHH nodes. The resulting summary gives a topological ""cartogram"" of the hierarchical data. We present deterministic and randomized algorithms for finding HHHs, which builds upon existing techniques by incorporating the hierarchy into the algorithms. Our experiments demonstrate several factors of improvement in accuracy over the straightforward approach, which is due to making algorithms hierarchy-aware."
"High speed computer and telephone networks carry large amounts of data and signalling traffic. The engineers who build and maintain these networks use a combination of hardware and software tools to monitor the stream of network traffic. Some of these tools operate directly on the live network; others record data on magnetic tape for later offline analysis by software. Most analysis tasks require tens to hundreds of gigabytes of data. Traffic analysis applications include protocol performance analysis, conformance testing, error monitoring and fraud detection."
"Abstract. Various temporal extensions to the relational model have been proposed. All of these, however, deviate significantly from the original relational model. This paper presents a temporal extension of the relational algebra that is not significantly different from the original relational model, yet is at least as expressive as any of the previous approaches. This algebra employs multidimensional tuple time-stamping to capture the complete temporal behavior of data. The basic relational operations are redefined as consistent extensions of the existing operations in a manner that preserves the basic algebraic equivalences of the snapshot (i.e., conventional static) algebra. A new operation, namely temporal projection, is introduced. The complete update semantics are formally specified and aggregate functions are defined. The algebra is closed, and reduces to the snapshot algebra. It is also shown to be at least as expressive as the calculus-based temporal query language TQuel. In order to assess the algebra, it is evaluated using a set of twenty-six criteria proposed in the literature, and compared to existing temporal relational algebras. The proposed algebra appears to satisfy more criteria than any other existing algebra. "
"Ontologies in current computer science parlance are computer based resources that represent agreed domain semantics. Unlike data models, the fundamental asset of ontologies is their relative indepe..."
"Existing and past generations of Prolog compilers have left deduction to run-time and this may account for the poor run-time performance of existing Prolog systems. Our work tries to minimize run-time deduction by shifting the deductive process to compile-time. In addition, we offer an alternative inferencing procedure based on translating logic to mixed integer programming. This makes available for research and implementation in deductive databases, all the theorems, algorithms, and software packages developed by the operations research community over the past 50 years. The method keeps the same query language as for disjunctive deductive databases, only the inferencing procedure changes. The language is purely declarative, independent of the order of rules in the program, and independent of the order in which literals occur in clause bodies. The technique avoids Prolog's problem of infinite looping. It saves run-time by doing primary inferencing at compile-time. Furthermore, it is incremental in nature. The first half of this article translates disjunctive clauses, integrity constraints, and database facts into Boolean equations, and develops procedures to use mixed integer programming methods to compute equations, and develops procedures to use mixed integer programming methods to compute equations, and develops procedures to use mixed integer programming methods to compute equations, and develops procedures to use mixed integer programming methods to compute ¡ªleast models of definite deductive databases, and ¡ªminimal models and the Generalized Closed World Assumption of disjunctive databases."
"Current data models like the NF2 model and object-oriented models support set-valued attributes. Hence, it becomes possible to have join predicates based on set comparison. This paper introduces and evaluates several main memory algorithms to evaluate efficiently this kind of join. More specifically, we concentrate on the set equality and the subset predicates."
"Abstract. XML is rapidly emerging as a standard for exchanging business data on the World Wide Web. For the foreseeable future, however, most business data will continue to be stored in relational database systems. Consequently, if XML is to fulfill its potential, some mechanism is needed to publish relational data as XML documents. Towards that goal, one of the major challenges is finding a way to efficiently structure and tag data from one or more tables as a hierarchical XML document. Different alternatives are possible depending on when this processing takes place and how much of it is done inside the relational engine. In this paper, we characterize and study the performance of these alternatives. Among other things, we explore the use of new scalar and aggregate functions in SQL for constructing complex XML documents directly in the relational engine. We also explore different execution plans for generating the content of an XML document. The results of an experimental study show that constructing XML documents inside the relational engine can have a significant performance benefit. Our results also show the superiority of having the relational engine use what we call an ¡°outer union plan¡± to generate the content of an XML document."
"Existing methods for spatial joins assume the existence of indices for the participating data sets. This assumption is not realistic for applications involving multiple map layer overlays or for queries involving non-spatial selections. In this paper, we explore a spatial join method that dynamically constructs index trees called seeded trees at join time. This methods uses knowledge of the data sets involved in the join process. Seeded trees are R-tree like structures, and are divided into the seed levels and the grown levels. The nodes in the seed levels are used to guide tree growth during tree construction. The seed levels can also be used to filter out some input data during construction, thereby reducing tree size. We develop a technique that uses intermediate linked lists during tree construction and significantly speeds up the tree construction process. The technique allows a large number of random disk accesses during tree construction to be replaced by smaller numbers of sequential accesses. Our performance studies show that spatial joins using seeded trees outperform those using other methods significantly in terms of disk I/O. The CPU penalties incurred are also lower except when seed-level filtering is used."
"With the rapid development of the Internet and the World Wide Web (WWW), very large amount of information is available and ready for downloading, most of which are free of charge. At the same time, hard disks with large capacity are available at affordable prices. Most of us nowadays often dump a large number of various types of documents into our computers without much thinking. On the other hand, file systems have not changed too much during the past decades. Most of them organize files in directories that form a tree structure, and a file is identified by its name and pathname in the directory tree. Remembering name of files created sometime ago and digging them out from a disk with dozen gigabytes of data in hundred thousands of files becomes never an easy task. Tools available for helping such a search are still far from satisfactory.Xbase (XML-based document BASE) is a prototype system aiming at addressing the above problem. By XML-based, we meant that XML is used to define the metadata. The current version of XBase stores text-based files, including semi-structured data such as XML, HTML, plain text documents (e.g., tex files, computer programs) and those files that can be converted into text (e.g., postscript files, PDF files). In XBase, file name is optional. Users can just load a file into XBase without giving a name and the directory where it should be stored. "
"This paper describes the POESIA approach to systematic composition of Web services. This pragmatic approach is strongly centered in the use of domain-specific multidimensional ontologies. Inspired by applications needs and founded on ontologies, workflows, and activity models, POESIA provides well-defined operations (aggregation, specialization, and instantiation) to support the composition of Web services. POESIA complements current proposals for Web services definition and composition by providing a higher degree of abstraction with verifiable consistency properties. We illustrate the POESIA approach using a concrete application scenario in agroenvironmental planning."
"Advanced technical applications like routing systems or electrical network management systems introduce the need for complex manipulations of large size graphs. Efficiently supporting this requirement is now regarded as a key feature of future database systems. This paper proposes an abstraction mechanism, called Database Graph View, to define and manipulate various kinds of graphs stored in either relational, object oriented or file systems. A database graph view provides a functional definition of a graph which allows its manipulation independently of its physical organization. Derivation operators are proposed to define new graph views upon existing ones. These operators permit the composition, in a single graph view, of graphs having different node and edge types and different implementations. The graph view mechanism comes with an execution model where both set-oriented and pipelined execution of graph operators can be expressed. The graph view operators form a library which can be integrated in database systems or applications managing persistent data with no repercussion on the data organization."
"When implementing persistent objects on a relational database, a major performance issue is prefetching data to minimize the number of roundtrips to the database. This is especially hard with navigational applications, since future accesses are unpredictable. We propose using the context in which an object is loaded as a predictor of future accesses, where context can be a stored collection of relationships, a query result, or a complex object. When an object O¡¯s state is loaded, similar state for other objects in O¡¯s context is prefetched. We present a design for maintaining context and using it to guide prefetch. We give performance measurements of its implementation in Microsoft Repository, showing up to a 70% reduction in running time. We describe variations that selectively apply the technique, exploit asynchronous access, and use application-supplied performance hints."
"The Large Scale Distributed Information Systems Lab (LSDIS) at the University of Georgia was established in the Fall of 1994 to perform research and technology development on two complementary themes in distributed information systems: Enabling Infocosm and Processes for Networked Organizations. Enabling Infocosm Theme. The merging of computers and communications with significant advances in networking infrastructure has made millions of information sources with wide varieties of information accessible. This capability gives us a vision of an information rich society ""infocosm"", where we expect to have any information any where we want in (m)any form(s) for effective decision making and knowledge-centric activities, improved productivity, and fun. "
"Though physical sensing instruments have long been used in astronomy, biology, and civil engineering, the recent emergence of wireless sensor networks and RFID has spurred a renaissance in sensor interest in both academia and industry. In this paper, we examine the spectrum of sensing platforms, from billion dollar satellites to tiny RF tags, and discuss the technological differences between them. We show that battery powered sensor networks, with low-power multihop radios and low-cost processors, occupy a sweet spot in this spectrum that is rife with opportunity for novel database research. We briefly summarize some of our research work in this space and present a number of examples of interesting sensor network-related problems that the database community is uniquely equipped to address."
"We present new techniques for supervised wrapper generation and automated web information extraction, and a system called Lixto implementing these techniques. Our system can generate wrappers which translate relevant pieces of HTML pages into XML. Lixto, of which a working prototype has been implemented, assists the user to semi-automatically create wrapper programs by providing a fully visual and interactive user interface. In this convenient user-interface very expressive extraction programs can be created. Internally, this functionality is reected by the new logicbased declarative language Elog. Users never have to deal with Elog and even familiarity with HTML is not required. Lixto can be used to create an \XML-Companion"" for an HTML web page with changing content, containing the continually updated XML translation of the relevant information."
Numerous proposals for extending the relational data model to incorporate the temporal dimension of data have appeared in the past several years. These proposals have differed considerably in the w...
"We present novel algorithms for the problem of using materialized views to compute answers to SQL queries with grouping and aggregation, in the presence of multiset tables. ln addition to its obvious potential in query optimization, this problem is important in many applications, such as data warehousing, very large transaction recording systems, global information systems and mobile computing, where access to local or cached materialized views may be cheaper than access to the underlying database. Our contributions are the following: First, we show that in the case where the query has grouping and aggregation but the views do not, a view is usable in answering a query only if there is an isomorphism between the view and a portion of the query. Second, when the views also have grouping and aggregation we identify conditions under which the aggregation information present in a view is sufficient to perform the aggregation computations requited in the query. The algorithms we describe for rewriting a query also consider the case in which the rewritten query may be a union of single-block queries. Our approach is a semantic one, in that it detects when the information existing in a view is sufficient to answer a query. In contrast, previous work performed syntactic transformations on the query such that the definition of the view would be a sub-part of the definition of the query. Consequently, these methods can only detect usages of views in limited cases."
"We introduce a rich language of descriptions for semistructured tree-like data, and we explain how such descriptions relate to the data they describe. Various query languages and data schemas can b..."
"In this paper we present a process management technology for the coordination of creative and large scale distributed processes. Our approach is the result of usage analysis in domains like Software Development, Architecture/Engineering/Construction, and e-Learning processes. The basic conclusions of these experiments are the following: (1) cooperative processes are described in the same way as production processes, but these descriptions are interpreted in a different way depending on the nature of the process, (2) the interpretation of process description depends mainly on the required flexibility of control flow and of data flow, and on the relationship between them, (3) the management of intermediate results is a central feature for supporting the cooperation inherent to these processes. COO-flow is a process technology that results from these studies. It is based on two complementing contributions: anticipation that allows succeeding activities to cooperate, and COO-transactions that allows parallel activities to cooperate. This paper introduces COO-flow characteristics, gives a (partial) formalization and briefly discusses its Web implementation."
"Introduction Modern Database Management Systems have numerous mechanisms for allowing administrators to man usage of system resources such as disk space and memory, yet they have typically not included mechanism trolling the usage of the all-important system resource of CPU-time. Traditionally, this functionality has been the host Operating System scheduler. Because of this, the only recourse for Oracle to control users¡¯ CPU usag impose hard limits on CPU consumption. If a user session exceeded its CPU limit, it was terminated. In Orac i we introduced the Oracle Database Resource Manager, a novel DBMS CPU management mechanism that allow base administrator to delineate logically distinct units of a workload and to partition CPU resources between units. Performance investigations show that running with the Database Resource Manager imposes no meas overheads on a workload, and the use of the Resource Manager actually improves performance with large u lations. Several commercial Operating Systems now support CPU resource management via a fair-share schedu mechanism. We believe that for large, complex applications such as Oracle, CPU resource management is be dled within the application itself. Since the scheduling is done within the Oracle application and the applicatio portable across numerous platforms, the Oracle Resource Manager is able to consistently enforce its schedu cies, independent of OS platform."
"In this short article we present a list of challenging issues in supporting effective querying over bioinformatics data sources and illustrate them through a selection of representative search scenarios provided by biologists. We end the article with a discussion on how the state-of-art research and technological development in Semantic Web, Ontology, Internet Data Management, and Internet Computing Systems can help addressing these issues."
"Small Materialized Aggregates (SMAs for short) are considered a highly flexible and versatile alternative for materialized data cubes. The basic idea is to compute many aggregate values for small to medium-sized buckets of tuples. These aggregates are then used to speed up query processing. We present the general idea and present an application of SMAs to the TPC-D benchmark. We show that application of SMAs to TPC-D Query 1 results in a speed up of two orders of magnitude. Then, we elaborate on the problem of query processing in the presence of SMAs. Last, we briefly discuss some further tuning possibilities for SMAs."
"A Problem Solving Agent (PSA) is either an hardware or software system or a human, with an ability to execute a finite set of tasks in an application domain. An activity consists of one or more tasks which can be executed by one or more PSAS. Activity management consists of decomposition of activities into tasks, coordination and data sharing among multiple PSAS executing the activity, and monitoring, scheduling and controlling the execution of multiple tasks of an activity. The CapBased-AMS [KYH95] (based on cooperative problem solving paradigm [CKNT93]) is composed of an activity specification and decomposition module and an activity execution and monitoring module. Capability-based activity specification and decomposition [Hun95]: Each PSA has its competence defined by a set of capabilities it has to execute tasks, and a task requires a certain competence (i.e. has needs) from the PSAS for its execution. Each activity is decomposed into a set of tasks by using the property that each task must be executed by exactly one PSA. Further, each task is matched to a PSA by selecting a PSA that has the capabilities to meet the needs of the task. Tokens are used to model the capability/need of a PSA/task, respectively. The specification of activities, sub-activities, tasks and PSAS are all user-driven."
"The size of The Boeing Company posts some stringent requirements on data warehouse design and implementation. We summarize four interesting and challenging issues in developing very large scale data warehouses, namely failure recovery, incremental update maintenance, cost model for schema design and query optimization, and metadata definition and management. For each issue, we give the reasons we think it is important but not well-addressed in research literature and commercial products, and our current research to solve it."
"In this paper, we propose a novel formulation for distance-based outliers that is based on the distance of a point from its kth nearest neighbor. We rank each point on the basis of its distance to its kth nearest neighbor and declare the top n points in this ranking to be outliers. In addition to developing relatively straightforward solutions to finding such outliers based on the classical nested-loop join and index join algorithms, we develop a highly efficient partition-based algorithm for mining outliers. This algorithm first partitions the input data set into disjoint subsets, and then prunes entire partitions as soon as it is determined that they cannot contain outliers. This results in substantial savings in computation. We present the results of an extensive experimental study on real-life and synthetic data sets. The results from a real-life NBA database highlight and reveal several expected and unexpected aspects of the database. The results from a study on synthetic data sets demonstrate that the partition-based algorithm scales well with respect to both data set size and data set dimensionality."
"Data warehouses contain large amounts of information, often collected from a variety of independent sources. Decision-support functions in a warehouse, such as on-line analytical processing (OLAP), involve hundreds of complex aggregate queries over large volumes of data. It is not feasible to compute these queries by scanning the data sets each time. Warehouse applications therefore build a large number of summary tables, or materialized aggregate views, to help them increase the system performance. As changes, most notably new transactional data, are collected at the data sources, all summary tables at the warehouse that depend upon this data need to be updated. Usually, source changes are loaded into the warehouse at regular intervals, usually once a day, in a batch window, and the warehouse is made unavailable for querying while it is updated. Since the number of summary tables that need to be maintained is often large, a critical issue for data warehousing is how to maintain the summary tables efficiently. In this paper we propose a method of maintaining aggregate views (the summary-delta table method), and use it to solve two problems in maintaining summary tables in a warehouse: (1) how to efficiently maintain a summary table while minimizing the batch window needed for maintenance, and (2) how to maintain a large set of summary tables defined over the same base tables. While several papers have addressed the issues relating to choosing and materializing a set of summary tables, this is the first paper to address maintaining summary tables efficiently."
"Traditional approaches to addressing historical queries assume asingle line of time evolution; that is, a system (database, relation) evolves over time through a sequence of transactions. Each transaction always applies to the unique, current state of the system, resulting in a new current state. There are, however, complex applications where the system's state evolves intomultiple lines of evolution. In general, this creates a tree (hierarchy) of evolution lines, where each tree node represents the time evolution of a particular subsystem. Multiple lines create novel historical queries, such asvertical orhorizontal historical queries. The key characteristic of these problems is that portions of the history are shared; answering historical queries should not necessitate duplication of shared histories as this could increase the storage requirements dramatically. Both the vertical and horizontal historical queries have two parts: a ¡°search¡± part, where the time of interest is located together with the appropriate subsystem, and a reconstruction part, where the subsystem's state is reconstructed for that time. This article focuses on the search part; several reconstruction methods, designed for single evolution lines can be applied once the appropriate time of interest is located. For both the vertical and the horizontal historical queries, we present algorithms that work without duplicating shared histories. Combinations of the vertical and horizontal queries are possible, and enable searching in both dimensions of the tree of evolutions."
"Approximately every five years, a group of database researchers meet to do a self-assessment of our community, including reflections on our impact on the industry as well as challenges facing our research community. This report summarizes the discussion and conclusions of the 9th such meeting, held during October 9-10, 2018 in Seattle."
"XQuery is the XML query language currently under development in the World Wide Web Consortium (W3C). XQuery specifications have been published in a series of W3C working drafts, and several reference implementations of the language are already available on the Web. If successful, XQuery has the potential to be one of the most important new computer languages to be introduced in several years. This tutorial will provide an overview of the syntax and semantics of XQuery, as well as insight into the principles that guided the design of the language."
"New telecommunication services and mobility networks have introduced databases in telecommunication networks. Compared with traditional use of databases, telecom databases must fulfill very tough requirements on response time, throughput, and availability. ClustRa is a telecom database prototype developed to run on standard workstations interconnected by an ATM switch. To meet the throughput and real-time response requirements, ClustRa is a main memory database with neighbor main, memory logging. Transactions are executed in parallel. To meet the availability requirements, we use a 2-safe replication scheme over two sites with independent failure modes, a novel declustering strategy, early detection of failures with fast takeover, and by on-line self-repair and maintenance. This paper gives an overview of ClustRa and includes a set of performance measurements."
"Object-oriented and object-relational DBMS support set valued attributes, which are a natural and concise way to model complex information. However, there has been limited research to-date on the evaluation of query operators that apply on sets. In this paper we study the join of two relations on their set-valued attributes. Various join types are considered, namely the set containment, set equality, and set overlap joins. We show that the inverted file, a powerful index for selection queries, can also facilitate the efficient evaluation of most join predicates. We propose join algorithms that utilize inverted files and compare them with signature-based methods for several set-comparison predicates."
"We develop a new schema for unstructured data. Traditional schemas resemble the type systems of programming languages. For unstructured data, however, the underlying type may be much less constrained and hence an alternative way of expressing constraints on the data is needed. Here, we propose that both data and schema be represented as edge-labeled graphs. We develop notions of conformance between a graph database and a graph schema and show that there is a natural and efficiently computable ordering on graph schemas. We then examine certain subclasses of schemas and show that schemas are closed under query applications. Finally, we discuss how they may be used in query decomposition and optimization."
"Specifically, an initial glossary of temporal database concepts and a. test suite of temporal queries were distributed before the workshop. Both of these document*s were amended based on the analysis and critique of the workshop. A language design committee was constituted after the workshop to develop a consensus temporal query la,nguage extension to SQL-92; this design also benefited from the discussion at the workshop. This report documents the discussions and consensus reached at the workshop. The report. reflects the conclusions rea.ched at the workshop in June, 1993 and further discussions amongst the group participants through electronic mail."
"1 Self-organizing Structured P2P Systems In the P2P community a fundamental distinction is made among unstructured and structured P2P systems for resource location. In unstructured P2P systems in principle peers are unaware of the resources that neighboring peers in the overlay networks maintain. Typically they resolve search requests by flooding techniques. Gnutella [9] is the most prominent example of this class. In contrast, in structured P2P systems peers maintain information about what resources neighboring peers offer. Thus queries can be directed and in consequence substantially fewer messages are needed. This comes at the cost of increased maintenance efforts during changes in the overlay network as a result of peers joining or leaving. The most prominent class of approaches to structured P2P systems are distributed hash tables (DHT), for example Chord [17]. Unstructured P2P systems have generated substantial interest because of emergent globalscale phenomena. For example, the Gnutella overlay network exhibits the following characteristics [15]: 1. The network has a small diameter, which ensures that a message flooding approach for search works with a relatively low timeto-life (approximately 7). 2. The node degrees of the overlay network follow a power-law distribution. Thus few peers have a large number of incoming links whereas most peers have a very low number of such links. These properties result from the way Gnutella performs network maintenance: each peer maintains a fixed number of active links. Using the network maintenance protocol a peer discovers new peers in the network by flooding discovery"
"The widespread distribution and availability of small-scale sensors, actuators, and embedded processors is transforming the physical world into a computing platform. One such example is a sensor network consisting of a large number of sensor nodes that combine physical sensing capabilities such as temperature, light, or seismic sensors with networking and computation capabilities. Applications range from environmental control, warehouse inventory, and health care to military environments. Existing sensor networks assume that the sensors are preprogrammed and send data to a central frontend where the data is aggregated and stored for offline querying and analysis. This approach has two major drawbacks. First, the user cannot change the behavior of the system on the fly. Second, conservation of battery power is a major design factor, but a central system cannot make use of in-network programming, which trades costly communication for cheap local computation.In this paper, we introduce the Cougar approach to tasking sensor networks through declarative queries. Given a user query, a query optimizer generates an efficient query plan for in-network query processing, which can vastly reduce resource usage and thus extend the lifetime of a sensor network. In addition, since queries are asked in a declarative language, the user is shielded from the physical characteristics of the network. We give a short overview of sensor networks, propose a natural architecture for a data management system for sensor networks, and describe open research problems in this area."
"s [41, 42]. academia [1932, 1926, 2267, 2275]. academic [1908, 2441]. acceleration [1869]. Access [2370, 13, 38, 1530, 1620, 1555, 2106, 1643, 1410, 602, 1672, 1033, 531, 601, 803, 1532, 1531, 949, 2204, 1455, 657, 598, 1263, 1086, 749, 409, 1969, 319, 2119, 450, 872, 1808, 171, 1559, 238, 821, 812, 1209, 1198, 694, 126, 1357, 883, 2139]. accesses [406]. Accessing [1295, 127, 515]. Accommodating [626]. account [1889]. accounting [679]. accrued [2385]. Accurate [276, 855]. achieve [858]. Achievements [1238, 619, 627]. ACID [1688]. ACM [38, 2139, 2216, 14, 2106, 2290, 2291, 42, 2239, 2445, 13, 2472, 2475, 2476, 2477, 2479, 2480, 1580, 1099, 2478, 2130, 2474, 1946, 1697, 2213, 2029, 2143, 2319, 2397, 2262]. ACM-SIGFIDET [38, 14]. Acquisition [288]. Across [1645, 2393, 1936]. ACT [1322]. ACT-NET [1322]. ACTA [586]. action [761]. Actions [1329]. activation [851]. Active [1322, 1239, 970, 833, 1471, 272, 1574, 1407, 1071, 1321, 1236, 1174, 420, 1171, 546, 1914, 1178, 1470, 766, 1098, 521, 1228, 1444, 1126, 1065]. Activities [136, 984, 216, 156, 1965, 587, 67, 748, 820]. activity [1311, 196]. Actual [211]. Ad [1394, 2001, 2056, 3]. ad-hoc [2001]. Ada [249, 458]. ADAM [1897]. adapt [2406]. Adaptable [1807]. adaptation [2113, 2328, 1209]. Adapting [1121, 254]. Adaptive [1730, 1675, 1002, 1642, 1024, 1826, 1112, 1737, 304, 1282, 307, 1809, 567]. ADBIS¡¯2001 [1931]. ADBMS [1321, 1322]. adding [463]. Addison [2043, 66]. Addison-Wesley [66]. Address [1148, 749, 1147, 642]. Addressing [1199]. ADEPT [1588]. Administering [221, 1303]. Administration [1478, 53]. Ado [1317]. ADO.NET [2236]. ADS [1071]. Advanced [1881, 952, 740, 1765, 2405, 1062, 678, 924, 1177]. Advancements [2105]. Advances [1227, 1931]. advantage [1163]. adventure [2310]. adversarial [2337]. Affiliation [2402]. after [1121]. again [1875]. against [471, 1939]. Agenda [1040]. Agent [1386, 1607, 2047, 1588, 1919, 1198, 2065]. Agent-Based [1386, 1607, 1588, 1198]."
"Active database systems have been a hot research topic for quite some years now. However, while ¡°active functionality¡± has been claimed for many systems, and notions such as ¡°active objects¡± or ¡°events¡± are used in many research areas (even beyond database technology), it is not yet clear which functionality a database management system must support in order to be legitimately considered as an active system. In this paper, we attempt to clarify the notion of ¡°active database management system¡± as well as the functionality it has to support. We thereby distinguish mandatory features that are needed to qualify as an active database system, and desired features which are nice to have. Finally, we perform a classification of applications of active database systems and identify the requirements for an active database management system in order to be applicable in these application areas."
"In many application fields, such as production lines or stock analysis, it is substantial to create and process high amounts of data at high rates. Such continuous data flows with unknown size and end are also called data streams. The processing and analysis of data streams are a challenge for common data management systems as they have to operate and deliver results in real time. Data Stream Management Systems (DSMS), as an advancement of database management systems, have been implemented to deal with these issues. DSMS have to adapt to the notion of data streams on various levels, such as query languages, processing or optimization. In this chapter we give an overview of the basics of data streams, architecture principles of DSMS and the used query languages. Furthermore, we specifically detail data quality aspects in DSMS as these play an important role for various applications based on data streams. Finally, the chapter also includes a list of research and commercial DSMS and their key properties."
"This docuinent specifies a temporal extension to the SQL-92 language standard. The language is designated TSQLZ. The document is organized as follows. The next section indicates the starting point of the design, the SQL92 language. Section 4 lists the desired features on which the TSQL2 Language Design Committee reached consensus. Section 5 presents the major concepts underlying TSQL2. Compatibility with SQL-92 is the topic of Section 6. Section 7 briefly discusses how the language can be implemented. Subsequent sections specify the syntax of the language extensions."
"MDM is a tool that enables the users to define schemes of different data models and to perform translations of schemes from one model to another. These functionalities can be at the basis of a customizable and integrated CASE environment supporting the analysis and design of information systems. MDM has two main components: the Model Manager and the Schema Manager. The Model Manager supports a specialized user, the model engineer, in the definition of a variety of models, on the basis of a limited set of metaconstructs covering almost all known conceptual models. The Schema Manager allows designers to create and modify schemes over the defined models, and to generate at each time a translation of a scheme into any of the data models currently available. Translations between models are automatically derived, at definition time, by combining a predefined set of elementary transformations, which implement the standard translations between simple combinations of constructs."
"The design of external index structures for one- and multidimensional extended objects is a long and well studied subject in basic database research. Today, more and more commercial applications rely on spatial datatypes and require a robust and seamless integration of appropriate access methods into reliable database servers. This paper proposes an efficient, dynamic and scalable approach to manage one-dimensional interval sequences within off-the-shelf object-relational database systems. The presented technique perfectly fits to the concept of space-filling curves and, thus, generalizes to spatially extended objects in multidimensional data spaces. Based on the Relational Interval Tree, the method is easily embedded in modern extensible indexing frameworks and significantly outmatches Linear Quadtrees and Relational R-trees with respect to usability, concurrency, and performance. As demonstrated by our experimental evaluation on an Oracle server with real GIS and CAD data, the competing methods are outperformed by factors of up to 4.6 (Linear Quadtree) and 58.3 (Relational R-tree) for query response time."
"Query optimizers rely on accurate cardinality estimates to produce good execution plans. Despite decades of research, existing cardinality estimators are inaccurate for complex queries, due to making lossy modeling assumptions and not capturing inter-table correlations. In this work, we show that it is possible to learn the correlations across all tables in a database without any independence assumptions. We present NeuroCard, a join cardinality estimator that builds a single neural density estimator over an entire database. Leveraging join sampling and modern deep autoregressive models, NeuroCard makes no inter-table or inter-column independence assumptions in its probabilistic modeling. NeuroCard achieves orders of magnitude higher accuracy than the best prior methods (a new state-of-the-art result of 8.5$times$ maximum error on JOB-light), scales to dozens of tables, while being compact in space (several MBs) and efficient to construct or update (seconds to minutes)."
"Publisher Summary Web Services are widely heralded as a step to the next generation of computing and a basis for resolving integration, one of the largest IT challenges. Web Services have much to learn from the development of database management systems (DBMSs) and the DBMS community has much to contribute to realizing Web Services. Web Services have much to learn from the failures of previous Service-Oriented Architectures (SOAs). In the 1980s, several distributed computing proposals emerged including the open software foundation's distributed computing environment (DCE), the object management group's (OMG's) common object request broker architecture (CORBA), Microsoft's distributed component object model (DCOM), as well as several distributed DBMS prototypes and products. These distributed computing proposals where part of the widely accepted notion of an SOA based on modularization, encapsulation, and re-use in which services could be invoked remotely and transparently across a distributed computing environment."
"The current main memory (DRAM) access speeds lag far behind CPU speeds. Cache memory, made of static RAM, is being used in today¡¯s architectures to bridge this gap. It provides access latencies of 2-4 processor cycles, in contrast to main memory which requires 15-25 cycles. Therefore, the performance of the CPU depends upon how well the cache can be utilized. We show that there are significant benefits in redesigning our traditional query processing algorithms so that they can make better use of the cache. The new algorithms run 8%-200% faster than the traditional ones."
"Data warehouses have been successfully employed for assisting decision making by offering a global view of the enterprise data and providing mechanisms for On-Line Analytical processing. Traditionally, data warehouses are utilized within the limits of an enterprise or organization. The growth of Internet and WWW however, has created new opportunities for data sharing among ad-hoc, geographically spanned and possibly mobile users. Since it is impractical for each enterprise to set up a worldwide infrastructure, currently such applications are handled by the central warehouse. This often yields poor performance, due to overloading of the central server and low transfer rate of the network. In this paper we propose an architecture for OLAP cache servers (OCS). An OCS is the equivalent of a proxy-server for web documents, but it is designed to accommodate data from warehouses and support OLAP operations. We allow numerous OCSs to be connected via an arbitrary network, and present a centralized, a semi-centralized and an autonomous control policy. We experimentally evaluate these policies and compare the performance gain against the existing systems where caching is performed only at the client side. Our architecture offers increased autonomy at remote clients, substantial network traffic savings, better scalability, lower response time and is complementary both to existing OLAP cache systems and distributed OLAP approaches."
"The purpose of good database logical design is to eliminate data redundancy and isertion and deletion anomalies. In order to achieve this objective for temporal databases, the notions of temporal types<, which formalize time granularities, and temporal functional dependencies< (TFDs) are intrduced. A temporal type is a monotonic mapping from ticks of time (represented by positive integers) to time sets (represented by subsets of reals) and is used to capture various standard and user-defined calendars. A TFD is a proper extension of the traditional functional dependency and takes the form X<<inline-equation> <f> ¡ú<hsp sp=""0.167""><inf><g>m</g></inf></f></inline-equation> Y,< meaning that there is a unique value for Y< during one tick of the temporal type ¦Ì for one particular X<  value. An axiomatization for TFDs is given. Because a finite set TFDs usually implies an infinite number of TFDs, we introduce the notion of and give an axiomatization for a finite closure< to effectively capture a finite set of implied TFDs that  are essential of the logical design. Temporal normalization procedures with respect to TFDs are given. Specifically, temporal Boyce-Codd normal form (TBCNF) that avoids all data redundancies due to TFDs, and temporal third normal form (T3NF) that allows dependency preservation, are defined. Both normal forms are proper extensions of their traditional counterparts, BCNF and 3NF. Decompositition algorithms are presented that give lossless TBCNF decompositions and lossless, dependency-preserving, T3NF decompositions."
"Publisher Summary eXtensible Markup Language (XML) is becoming the predominant data exchange format in a variety of application domains (supply-chain, scientific data processing, telecommunication infrastructure, etc.). Not only is an increasing amount of XML data now being processed, but XML is also increasingly being used in business-critical applications. Efficient and reliable storage is an important requirement for these applications. By relying on relational engines for this purpose, XML developers can benefit from a complete set of data management services (including concurrency control, crash recovery, and scalability) and from the highly optimized relational query processors. Strategies that automate the process of generating XML to relational mappings have been proposed in the literature. Due to the flexibility of the XML infrastructure, different XML applications exhibit widely different characteristics (for example, permissive vs. strict schemas, different access patterns)."
"We consider the problem of evaluating a large number of XPath expressions on an XML stream. Our main contribution consists in showing that Deterministic Finite Automata (DFA) can be used effectively for this problem: in our experiments we achieve a throughput of about 5.4MB/s, independent of the number of XPath expressions (up to 1,000,000 in our tests). The major problem we face is that of the size of the DFA. Since the number of states grows exponentially with the number of XPath expressions, it was previously believed that DFAs cannot be used to process large sets of expressions. We make a theoretical analysis of the number of states in the DFA resulting from XPath expressions, and consider both the case when it is constructed eagerly, and when it is constructed lazily. Our analysis indicates that, when the automaton is constructed lazily, and under certain assumptions about the structure of the input XML data, the number of states in the lazy DFA is manageable. We also validate experimentally our findings, on both synthetic and real XML data sets."
"This paper introduces a new data structure, called V-trees, designed to store long sequences of points in 2D space and yet allow efficient access to their fragments. They also optimire access to a sequence of points when the query involves changes to a smaller scale. V-trees operate in much the same way as positional B-Trees do in the context of long fields and they can be viewed as a variant of Rtrees. The design of V-trees was motivated by the problem of storing and retrieving geographic objects that are fairly long, such as river margins or political boundaries, and the fact that geographic queries typically access just fragments of such objects, frequently using a smaller scale."
"Web application servers (WASs) are middleware platforms for deployment and execution of component-based Web applications. To cater for an increasingly diverse range of QoS demands, WAS must be capable of adaptation during execution to modify itself and to respond to changing conditions in its external environment. To accommodate such changes, WAS should provide both deployment-time configurability and run-time reconfigurability. Unfortunately, most of the mainstream Web application servers adopt a monolithic architecture and ""black box"" philosophy to their design, and fail to properly address such requirements. In our point of view, adaptation and reconfigurability of WASs should be available at any time of the whole lifecycle. In this paper, a middleware architecture (WebFrame) that supports multi-phase adaptation using computational reflection, microkernel, and component techniques is proposed for Web application servers. The architecture is structured into five layers. Both deployment-time configuration and run-time reconfiguration at multiple layers is supported in this architecture. The key insight to this work is the MService reconfiguration design pattern, which provides dynamic adaptation at run time by swapping in/out the optional middleware components. The comparative evaluation of the performance impact of reflection and multi-phase reconfigurability on systems are given."
"Recent high-performance processors employ sophisticated techniques to overlap and simultaneously execute multiple computation and memory operations. Intuitively, these techniques should help database applications, which are becoming increasingly compute and memory bound. Unfortunately, recent studies report that faster processors do not improve database system performance to the same extent as scientific workloads. Recent work on database systems focusing on minimizing memory latencies, such as cache-conscious algorithms for sorting and data placement, is one step toward addressing this problem. However, to best design high performance DBMSs we must carefully evaluate and understand the processor and memory behavior of commercial DBMSs on today¡¯s hardware platforms. In this paper we answer the question ¡°Where does time go when a database system is executed on a modern computer platform?¡± We examine four commercial DBMSs running on an Intel Xeon and NT 4.0. We introduce a framework for analyzing query execution time on a DBMS running on a server with a modern processor and memory architecture. To focus on processor and memory interactions and exclude effects from the I/O subsystem, we use a memory resident database. Using simple queries we find that database developers should (a) optimize data placement for the second level of data cache, and not the first, (b) optimize instruction placement to reduce first-level instruction cache stalls, but (c) not expect the overall execution time to decrease significantly without addressing stalls related to subtle implementation issues (e.g., branch prediction)."
"Today¡¯s object-relational DBMSs (ORDBMSs) are designed to support novel application domains by providing an extensible architecture, supplemented by domain-specific database extensions supplied by external vendors. An important aspect of ORDBMSs is support for extensible indexing, which allows the core database server to be extended with external access methods (AMs). This paper describes a new approach to extensible indexing implemented in Informix Dynamic Server with Universal Data Option (IDS/UDO). The approach is is based on the generalized search tree, or GiST, which is a template index structure for abstract data types that supports an extensible set of queries. GiST encapsulates core database indexing functionality including search, update, concurrency control and recovery, and thereby relieves the external access method (AM) of the burden of dealing with these issues. The IDS/UDO implementation employs a newly designed GiST API that reduces the number of user defined function calls, which are typically expensive to execute, and at the same time makes GiST a more flexible data structure. Experiments show that GiST-based AM extensibility can offer substantially better performance than built-in AMs when indexing userdefined data types."
"Dear ACM TODS Community, I hope you are all well and safe during these extraordinarily challenging times. I am honored to serve as the next Editor-in-Chief of the ACM Transactions on Database Systems. There is no doubt that ours is a foundational community in computer science and beyond, developing methodologies that play an important role in and contribute to insight and innovation across numerous areas. ACM TODS provides a venue for some of the best work in the field, and I am grateful to our research community for their impactful contributions and support. Part of my job is to nurture continued excellence and value of ACM TODS, with the goal of having it serve as a venue for the latest compelling results that influence research directions and progress."
"The data management plan of the Community Earth System Model (CESM)[1] from the National Center for Atmospheric Research (NCAR) is given historical context and its policies, definitions, and features are detailed. The drivers of CESM data management are discussed, including the upcoming Coupled Model Intercomparison Project 5 (CMIP5), the ongoing Earth System Grid (ESG) project, and the strategies to address these drivers are mentioned. Future plans and strategies to address CESM data management needs and requirements are noted. The significant challenges resulting from the use of CESM output in the areas of metadata, preservation, curation, provenance, and other aspects of data management are considered."
"In semistructured databases there is no schema fixed in advance. To provide the benefits of a schema in such environments, we introduce DataGuides: concise and accurate structural summaries of semistructured databases. DataGuides serve as dynamic schemas, generated from the database; they are useful for browsing database structure, formulating queries, storing information such as statistics and sample values, and enabling query optimization. This paper presents the theoretical foundations of DataGuides along with an algorithm for their creation and an overview of incremental maintenance. We provide performance results based on our implementation of DataGuides in the Lore DBMS for semistructured data. We also describe the use of DataGuides in Lore, both in the user interface to enable structure browsing and query formulation, and as a means of guiding the query processor and optimizing query execution."
"We present new algorithms for computing approximate quantiles of large datasets in a single pass. The approximation guarantees are explicit, and apply for arbitrary value distributions and arrival distributions of the dataset. The main memory requirements are smaller than those reported earlier by an order of magnitude. We also discuss methods that couple the approximation algorithms with random sampling to further reduce memory requirements. With sampling, the approximation guarantees are explicit but probabilistic, i.e. they apply with respect to a (user controlled) confidence parameter. We present the algorithms, their theoretical analysis and simulation results on different datasets."
"Given the present cost of memories and the very large storage and bandwidth requirements of large-scale multimedia databases, hierarchical storage servers (which consist of RAM, disk storage, and robot-based tertiary libraries) are becoming increasingly popular. However, related research is scarce and employs tertiary storage for storage augmentation purposes only. This work, exploiting the ever-increasing performance offered by (par. titularly) modern tape library products, aims to utilize tertiary storage in order to augment the system¡¯s performance. We consider the issue of elevating continuous data from its permanent place in tertiary for display purposes. Our primary goals are to save on the secondary storage bandwidth that traditional techniques require for the display of continuous objects, while requiring no additional . RAM buffer space. To this end we develop algorithms for sharing the responsibility for * Research supported by the European Community under the ESPRIT Long Term Research Project HERMES no. 9141. t Research supported by the Canadian government under NSERC grant number 0155218, and by the 1996-97 Going Global STEP program. "
"Hash-based scalable distributed data structures (SDDSs), like LH* and DDH, for networks of interconnected computers (multicomputers) were shown to open new perspectives for file management. We propose a family of ordered SDDSs, called RP*, providing for ordered and dynamic files on multicomputers, and thus for more efficient processing of range queries and of ordered traversals of files. The basic algorithm termed RP*N, builds the file with the same key space partitioning as a B-tree, but avoids indexes through the use of multicast. The algorithms, RP*C and RP*S enhance throughput for faster networks, adding the indexes on clients, or on clients and servers, while either decreasing or avoiding multicast. RP* files are shown highly efficient with access performance exceeding traditional files by an order of magnitude or two, and, for non-range queries, very close to LH*."
"An overview of selected papers related to bone published in 2017 is provided.PurposeThis paper accompanies a lecture at the 2018 Belgian Bone Club annual Clinical Update Symposium held in Brussels on January 20th, discussing the best papers (in the opinion of the author) published in the previous year.MethodsA PubMed search using the keyword ¡°bone¡± and articles published in 2017."
"There are a number of database systems available free of charge for the research community, with complete access to the source code. Some of these systems result from completed research projects, others have been developed outside the research community. How can the database community best take advantage of these publically available systems? The most widely used open-source database is MySQL. Their objective is to become the 'best and most used database in the world'."
"Conceptual data modeling for complex applications, such as multimedia and spatiotemporal applications, often results in large, complicated and difficult-to-comprehend diagrams. One reason for this is that these diagrams frequently involve repetition of autonomous, semantically meaningful parts that capture similar situations and characteristics. By recognizing such parts and treating them as units, it is possible to simplify the diagrams, as well as the conceptual modeling process. We propose to capture autonomous and semantically meaningful excerpts of diagrams that occur frequently as modeling patterns. Specifically, the paper concerns modeling patterns for conceptual design of spatiotemporal databases. Based on requirements drawn from real applications, it presents a set of modeling patterns that capture spatial, temporal, and spatiotemporal aspects. To facilitate the conceptual design process, these patterns are abbreviated by corresponding spatial, temporal, and spatiotemporal pattern abstractions, termed components. The result is more elegant and less-detailed diagrams that are easier to comprehend, but yet semantically rich. The Entity-Relationship model serves as the context for this study. An extensive example from a real cadastral application illustrates the benefits of using a component-based conceptual model."
"Information extraction systems are traditionally implemented as a pipeline of special-purpose processing modules targeting the extraction of a particular kind of information. A major drawback of such approach is that whenever a new extraction goal emerges or a module is improved, extraction has to be re-applied from scratch to the entire text corpus even though only a small part of the corpus might be affected. In this paper, we describe a novel approach for information extraction so that extraction needs are expressed in the form of database queries, which are evaluated and optimized by databases. Using database queries for information extraction enables generic extraction and minimizes reprocessing of data. In addition, our approach provides two different query generation components that can automatically form database queries for extraction from training datasets, as well as from unlabeled data through a mechanism inspired by the pseudo-relevance feedback approach found in protein-protein interactions and drug-protein-metabolic relations from two sets of corpus. Experiments show that our approach achieves a precision of 83.6% and recall of 58.6% (F-measure of 64.2%) for the extraction of protein-protein interactions from the BioCreative 2 corpus, while achieving a precision of 85.0% and recall of 26.0% (F-measure of 39.8%) for drug-protein-metabolic relations."
"George Mason University began as an independent state university in 1972. Its development has been marked by rapid growth and innovative planning, resulting in an enrollment of more than 24,000 students in 1997. It is located in Fairfax, Virginia¡ªabout fifteen miles southwest of Washington, DC¡ªnear many governmental agencies and industrial firms specializing in information-intensive products and services. Information and Software Systems Engineering (ISSE) is one of six departments in GMU's School of Information Technology and Engineering (SITE). Established in 1985, SITE has approximately 90 faculty and ISSE has 13 full time faculty. ISSE is a rapidly growing department with wide-ranging teaching and research interests."
"In information-integration systems, sources may have diverse and limited query capabilities. To obtain maximum information from these restrictive sources to answer a query, one can access sources that are not specified in the query (i.e., off-query sources). In this article, we propose a query-planning framework to answer queries in the presence of limited access patterns. In the framework, a query and source descriptions are translated to a recursive datalog program. We then solve optimization problems in this framework, including how to decide whether accessing off-query sources is necessary, how to choose useful sources for a query, and how to test query containment. We develop algorithms to solve these problems, and thus construct an efficient program to answer a query."
"Traditional database systems provide a user with the ability to query and manipulate one database state, namely the current database state. However, in several emerging applications, the ability to analyze ¡°what-if¡± scenarios in order to reason about the impact of an update (before committing that update) is of paramount importance. Example applications include hypothetical database access, active database management systems, and version management, to name a few. The central thesis of the Heraclitus paradigm is to provide flexible support for applications such as these by elevating deltas, which represent updates proposed against the current database state, to be first-class citizens. Heraclitus[Alg,C] is a database programming language that extends C to incorporate the relational algebra and deltas. Operators are provided that enable the programmer to explicitly construct, combine, and access deltas. Most interesting is the when operator, that supports hypothetical access to a delta: the expression E when &sgr; yields the value that side effect free expression E would have if the value of delta expression &sgr; were applied to the current database state. This article presents a broad overview of the philosophy underlying the Heraclitus paradigm, and describes the design and prototype implementation of Heraclitus[Alg, C]. A model-independent formalism for the Heraclitus paradigm is also presented. To illustrate the utility of Heraclitus, the article presents an in-depth discussion of how Heraclitus[Alg, C] can be used to specify, and thereby implement, a wide range of execution models for rule application in active databases; this includes both prominent execution models presented in the literature, and more recent ¡°customized¡± execution models with novel features."
"The naive solution would be to do an exhaustive search across all possible subsets of items and count how many satisfy the predicate conditions we are looking for. This approach, although it would be efficient space-wise (only store the combinations we need) would waste a lot of time (creating all possible combinations). This paper presents a few algorithms that start with a seed itemset (one that already satisfies the boolean predicates we wish to evaluate) and grow them into itemsets of maximal size."
"An Object-Oriented database can utilize the benefits of both the design and implementation of any application. Due to the increased popularity of database systems many new database systems based on varying data model and implementation have entered in the market. Database systems have complex architecture but they are the key factors behind the business transformations. Choosing the best one in any category is an important task based on performance analysis. This chapter deals with the database estimation methodology which integrates the database analysis task and performance analysis task. There are three major techniques for the performance estimation which are analytical modeling, simulation modeling and benchmarking."
"This paper describes the design and implementation of PEST0 (Portable Explorer of Snuctured Objects), a user interface that supports browsing and querying of object databases. PEST0 allows users to navigate the relationships that exist among objects. In addition, users can formulate complex object queries through an integrated query paradigm (¡°query-in-place¡±) that presents querying as a natural extension of browsing. PEST0 is designed to be portable to any object database system that supports a high-level query language; in addition, PEST0 is extensible, providing hooks for specialized predicate formation and object display tools for new data types (e.g., images or text). uniformly and manipulated using an object-oriented dialect of SQL. One component of this project, which is joint work between IBM Almaden and the University of Wisconsin, is the development of a graphical user interface called PEST0 (Portable Explorer of STructured Objects). We refer to the PEST0 interface as a query/browser, as it marries navigational object browsing¡¯ with declarative querying; it integrates browsing and querying via a ¡°query-in-place¡± paradigm that provides a powerful yet natural user interface for exploring the contents of object databases."
Higher education institutions (HEIs) are increasingly addressing their environmental impact and to do this need to improve access to environmental information in order to improve decision making and sustainability efforts. Educational institutions have a different focus to other more industrial organisations and therefore frameworks for these organisations are not necessarily suited to educational environments. Whilst several environmental management information systems (EMIS) have been proposed there is a lack of understanding of the components which should be included in such a system due to the existing broad definitions. In addition there are not many best practice guidelines to support the design and development of these systems. This paper proposes a framework for EMISs in higher education. The framework is derived from several literature studies and includes guidelines which can assist with the design of an EMIS. These guidelines are classified according to the components of EMIS.
"Abstract. This paper describes the overall design and architecture of the Timber XML database system currently being implemented at the University of Michigan. The system is based upon a bulk algebra for manipulating trees, and natively stores XML. New access methods have been developed to evaluate queries in the XML context, and new cost estimation and query optimization techniques have also been developed. We present performance numbers to support some of our design decisions. We believe that the key intellectual contribution of this system is a comprehensive set-at-a-time query processing ability in a native XML store, with all the standard components of relational query processing, including algebraic rewriting and a cost-based optimizer."
"A radar transmitter apparatus comprising a radar transmitter equipped with a modulator arranged in an oil-filled housing, the modulator being held in spaced relationship with respect to the inner walls of the housing in order to form an intermediate space for the convection flow of the oil. The housing is substantially trough or vat-shaped and covered by a trough or vat-shaped cover member. In the internal chamber or space between the cover member and the modulator, which internal space is wetted by the oil, there is arranged, on the one hand, a magnetron attached at the cover member and, on the other hand, a thyratron which is mounted directly below an opening at the cover member. This opening is closable by means of oil sealed throughpassage means."
"Estimating the number of distinct values is a wellstudied problem, due to its frequent occurrence in queries and its importance in selecting good query plans. Previous work has shown powerful negative results on the quality of distinct-values estimates based on sampling (or other techniques that examine only part of the input data). We present an approach, called distinct sampling, that collects a specially tailored sample over the distinct values in the input, in a single scan of the data. In contrast to the previous negative results, our small Distinct Samples are guaranteed to accurately estimate the number of distinct values. The samples can be incrementally maintained up-to-date in the presence of data insertions and deletions, with minimal time and memory overheads, so that the full scan may be performed only once. Moreover, a stored Distinct Sample can be used to accurately estimate the number of distinct values within any range specified by the query, or within any other subset of the data satisfying a query predicate. We present an extensive experimental study of distinct sampling. Using synthetic and real-world data sets, we show that distinct sampling gives distinct-values estimates to within 0%©\10% relative error, whereas previous methods typically incur 50%©\250% relative error. Next, we show how distinct sampling can provide fast, highlyaccurate approximate answers for ¡°report¡± queries in high-volume, session-based event recording environments, such as IP networks, customer service call centers, etc. For a commercial call center environment, we show that a 1% Distinct Sample"
"On March 7 and 8, 1996, the First International Workshop on Real-Time Databases (RTDB'96) was held in Newport Beach, California. There were about 50 workshop participants from 12 countries. Twenty two papers were presented and actively discussed in the 2-day single-track 6-session technical program. There were also two panel sessions to assess the state of RTDB research. In this report, we provide highlights of the workshop."
"Abstract A Real-Time DataBase System (RTDBS) can be viewed as an amalgamation of a conventional DataBase Management System (DBMS) and a real-time system. Like a DBMS, it has to process transactions and guarantee ACID database properties. Furthermore, it has to operate in real-time, satisfying time constraints imposed on transaction commitments. A RTDBS may exist as a stand-alone system or as an embedded component in a larger multidatabase system. The publication in 1988 of a special issue of ACM SIGMOD Record on Real-Time DataBases signaled the birth of the RTDBS research area---an area that brings together researchers from both the database and real-time systems communities. Today, almost eight years later, I am pleased to present in this special section of ACM SIGMOD Record a review of recent advances in RTDBS research. There were 18 submissions to this special section, of which eight papers were selected for inclusion to provide the readers of ACM SIGMOD Record with an overview of current and future research directions within the RTDBS community. In this paper, I will summarize these directions and provide the reader with pointers to other publications for further information."
"Ad hoc querying is difficult on very large datasets, since it is usually not possible to have the entire dataset on disk. While compression can be used to decrease the size of the dataset, compressed data is notoriously difficult to index or access. In this paper we consider a very large dataset comprising multiple distinct time sequences. Each point in the sequence is a numerical value. We show how to compress such a dataset into a format that supports ad hoc querying, provided that a small error can be tolerated when the data is uncompressed. Experiments on large, real world datasets (AT&T customer calling patterns) show that the proposed method achieves an average of less than 5% error in any data value after compressing to a mere 2.5% of the original space (i.e., a 40:1 compression ratio), with these numbers not very sensitive to dataset size. Experiments on aggregate queries achieved a 0.5% reconstruction error with a space requirement under 2%."
"On-Line Analytical Processing (OLAP) based on a dimensional view of data is being used increasingly for the purpose of analyzing very large amounts of data. To improve query performance, modern OLAP systems use a technique known as practical pre-aggregation, where select combinations of aggregate queries are materialized and re-used to compute other aggregates; full preaggregation, where all combinations of aggregates are materialized, is infeasible. However, this reuse of aggregates is contingent on the dimension hierarchies and the relationships between facts and dimensions satisfying stringent constraints, which severely limits the scope of practical preaggregation. This paper significantly extends the scope of practical pre-aggregation to cover a much wider range of realistic situations. Specifically, algorithms are given that transform ¡°irregular¡± dimension hierarchies and fact-dimension relationships, which often occur in real-world OLAP applications, into well-behaved structures that, when used by existing OLAP systems, enable practical pre-aggregation. The algorithms have low computational complexity and may be applied incrementally to reduce the cost of updating OLAP structures."
"SIGMOD Record encourages readers to join the conversation by writing reviews on recent publications in the field. For more information, please contact the Contributing Editor Paul King at paul.h.king@vanderbilt.edu"
"In this paper, we propose a new method for indexing large amounts of point and spatial data in high-dimensional space. An analysis shows that index structures such as the R*-tree are not adequate for indexing high-dimensional data sets. The major problem of R-tree-based index structures is the overlap of the bounding boxes in the directory, which increases with growing dimension. To avoid this problem, we introduce a new organization of the directory which uses a split algorithm minimizing overlap and additionally utilizes the concept of supernodes. The basic idea of overlap-minimizing split and supernodes is to keep the directory as hierarchical as possible, and at the same time to avoid splits in the directory that would result in high overlap. Our experiments show that for high-dimensional data, the X-tree outperforms the well-known R*-tree and the TV-tree by up to two orders of magnitude."
"Due to the development of the World Wide Web, the integration of heterogeneous data sources has become a major concern of the database community. Appropriate architectures and query languages have been proposed. Yet, the problem of data conversion which is essential for the development of mediators/wrappers architectures has remained largely unexplored. In this paper, we present the YAT system for data conversion. This system provides tools for the specification and the implementation of data conversions among heterogeneous data sources. It relies on a middleware model, a declarative language, a customization mechanism and a graphical interface. The model is based on named trees with ordered and labeled nodes. Like semistructured data models, it is simple enough to facilitate the representation of any data. Its main originality is that it allows to reason at various levels of representation. The YAT conversion language (called YATL) is declarative, rule-based and features enhanced pattern matching facilities and powerful restructuring primitives. It allows to preserve or reconstruct the order of collections. The customization mechanism relies on program instantiations: an existing program may be instantiated into a more specific one, and then easily modified. We also present the architecture, implementation and practical use of the YAT prototype, currently under evaluation within the OPAL* project."
"Efficient storage, indexing and retrieval of time-evolving spatial data are some of the tasks that a Spatiotemporal Database Management System (STDBMS) must support. Aiming at designers of indexing methods and access structures, in this article we review the GSTD algorithm for generating spatiotemporal datasets according to several user-defined parameters, and introduce a WWW-based environment for generating and visualizing such datasets. "
"Computational grids provide access to distributed compute resources and distributed data resources, creating unique opportunities for improved access to information. When data repositories are accessible from any platform, applications can be developed that support nontraditional uses of computing resources. Environments thus enabled include knowledge networks, in which researchers collaborate on common problems by publishing results in digital libraries, and digital government, in which policy decisions are based on knowledge gleaned from teams of experts accessing distributed data repositories. In both cases, users access data that has been turned into information through the addition of metadata that describes its origin and quality. Information-based computing within computational grids will enable collective advances in knowledge [396]. In this view of the applications that will dominate in the future, application development will be driven by the need to process and analyze information , rather than the need to simulate a physical process. In addition to accessing specific data sets, applications will need to use information discovery interfaces [138] and dynamically determine which data sets to process. In Section 5.1, we discuss how these applications will evolve, and we illustrate their new capabilities by presenting projects now under way that use some concepts implicit within grid environments. Data-intensive applications that will require the manipulation of terabytes of data aggregated across hundreds of files range from comparisons of numerical simulation output, to analyses of satellite observation data streams, to searches for homologous structures"
"The Context Interchange strategy presents a novel approach for mediated data access in which semantic conflicts among heterogeneous systems are not identified a priori, but are detected and reconciled by a <italic>context mediator</italic> through comparison of contexts. This paper reports on the implementation of a Context Interchange Prototype which provides a concrete demonstration of the features and benefits of this integration strategy. "
"In order to provide database availability in the presence of node and site failures, traditional l-safe algorithms disallow primary and hot standby replicas to be located at the same site. This means that the failure of a single primary node must be handled like a failure of the entire primary site. Furthermore, this excludes symmetric site configurations, where the primary replicas are located at the site closest to the accessing clients. In this paper, we present three novel l-safe algorithms that allow the above restrictions to be removed. The relative performance of these and the traditional algorithms are evaluated by means of simulation studies. Our main conclusion is that the restrictions of the traditional algorithms can be removed without significantly increasing the processing overhead, during normal operation. From an evaluation based on performance, availability, and transaction durability, the novel dependency tracking algorithm provides the best overall solution."
"In the discussion of research issues in spatial databases (SIGMOD Record vol. 19, no. 4, Dec 1990) we stated the need for a robust framework for analytical comparison of a broad range of spatial access methods. The utility of such a comparison, even of very closely related access methods, was shown in [FALO87]. A necessary precondition for a meaningful analytical comparison is the existence of strong analytical results for individual access methods. In the following paper, Salzberg and Lomet take the worst case analytical results on fan-out and average storage utilization they obtained for their hB-tree [LOME89,LOME90] and extend the analysis to another robust method, Z-order encoding [OREN84]. We think this paper is a start on the comparative assessment of access methods based on analytical results. We hope to see future work extend the framework beyond worst case analysis, and to other access methods as well."
"Introduction to Constraint Databases comprehensively covers both constraint-database theory and several sample systems. The book reveals how constraint databases bring together techniques from a variety of fields, such as logic and model thoery, algebraic and computational geometry, and symbolic computation, to the design and analysis of data models and query languages. Constraint databases are shown to be powerful and simple tools for data modeling and querying in application areas---such as environmental modeling, bioinformatics, and computer vision---that are not suitable for relational databases. Specific applications are examined in geographic information systems, spatiotemporal data management, linear programming, genome databases, model checking of automata, and other areas."
"Mobile computing has the potential for managing information globally. Data management issues in mobile computing have received some attention in recent times, and the design of adaptive braodcast protocols has been posed as an important probllem. Such protocols are employed by database servers to decide on the content of bbroadcasts dynamically, in response to client mobility and demand patterns. In this paper we design such protocols and also propose efficient retrieval strategies that may be employed by clients to download information from broadcasts. The goal is to design cooperative strategies between server and client to provide access to information in such a way as to minimize energy expenditure by clients. We evaluate the performance of our protocols both analytically and through simulation."
"Bitmap indexing has been touted as a promising approach for processing complex adhoc queries in read-mostly environments, like those of decision support systems. Nevertheless, only few possible bitmap schemes have been proposed in the past and very little is known about the space-time tradeoff that they offer. In this paper, we present a general framework to study the design space of bitmap indexes for selection queries and examine the disk-space and time characteristics that the various alternative index choices offer. In particular, we draw a parallel between bitmap indexing and number representation in different number systems, and define a space of two orthogonal dimensions that captures a wide array of bitmap indexes, both old and new. Within that space, we identify (analytically or experimentally) the following interesting points: (1) the time-optimal bitmap index; (2) the space-optimal bitmap index; (3) the bitmap index with the optimal space-time tradeoff (knee); and (4) the time-optimal bitmap index under a given disk-space constraint. Finally, we examine the impact of bitmap compression and bitmap buffering on the space-time tradeoffs among those indexes. As part of this work, we also describe a bitmap-index-based evaluation algorithm for selection queries that represents an improvement over earlier proposals. We believe that this study offers a useful first set of guidelines for physical database design using bitmap indexes."
"Approximately every five years, a group of database researchers meet to do a self-assessment of our community, including reflections on our impact on the industry as well as challenges facing our research community. This report summarizes the discussion and conclusions of the 9th such meeting, held during October 9-10, 2018 in Seattle."
"Whereas physical database tuning has received a lot of attention over the last decade, logical database tuning seems to be under-studied. We have developed a project called DBA Companion devoted to the understanding of logical database constraints from which logical database tuning can be achieved.In this setting, two main data mining issues need to be addressed: the first one is the design of efficient algorithms for functional dependencies and inclusion dependencies inference and the second one is about the interestingness of the discovered knowledge. In this paper, we point out some relationships between database analysis and data mining. In this setting, we sketch the underlying themes of our approach. Some database applications that could benefit from our project are also described, including logical database tuning."
"Information Integration is one of the core problems in distributed databases, cooperative information systems, and data warehousing, which are key areas in the software development industry. Two critical factors for the design and maintenance of applications requiring Information Integration are conceptual modeling of the domain, and reasoning support over the conceptual representation. We demonstrate that Knowledge Representation and Reasoning techniques can play an important role for both of these factors, by proposing a Description Logic based framework for Information Integration. We show that the development of successful Information Integration solutions requires not only to resort to very expressive Description Logics, but also to significantly extend them. We present a novel approach to conceptual modeling for Information Integration, which allows for suitably modeling the global concepts of the application, the individual information sources, and the constraints among different sources. Moreover, we devise inference procedures for the fundamental reasoning services, namely relation and concept subsumption, and query containment. Finally, we present a methodological framework for Information Integration, which can be applied in several contexts, and highlights the role of reasoning services within the design process."
"Internet websites increasingly rely on database management systems. There are several reasons for this trend: As sites grow larger, managing the content becomes impossible without the use of a DBMS to keep track of the nature, origin, authorship, and modification history of each article. As sites become more interactive, tracking and logging user activity and user contributions creates valuable new data, which again is best managed using a DBMS. The emerging paradigm of Customer-Centric e-Business places a premium on engaging users, building a relationship with them across visits, and leveraging their expertise and feed-back. Supporting this paradigm means that we not only have to track what users visit on a site, we also have to enable them to offer opinions and contribute to the content of the website in various ways; naturally, this requires us to use a DBMS. In order to personalize a user's experience, a site must dynamically construct (or at least fine-tune) each page as it is delivered, taking into account information about the user's past activity and the nature of the content on the current page. In other words, personalization is made possible by utilizing the information (about content and user activity) that we already indicated is best managed using a DBMS."
"When SQL and the relational data model were introduced 25 years ago as a general data management concept, enterprise software migrated quickly to this new technology. It is fair to say that SQL and the various implementations of RDBMSs became the backbone of enterprise systems. In those days. we believed that business planning, transaction processing and analytics should reside in one single system. Despite the incredible improvements in computer hardware, high-speed networks, display devices and the associated software, speed and flexibility remained an issue. The nature of RDBMSs, being organized along rows, prohibited us from providing instant analytical insight and finally led to the introduction of so-called data warehouses. This paper will question some of the fundamentals of the OLAP and OLTP separation. Based on the analysis of real customer environments and experience in some prototype implementations, a new proposal for an enterprise data management concept will be presented. In our proposal, the participants in enterprise applications, customers, orders, accounting documents, products, employees etc. will be modeled as objects and also stored and maintained as such. Despite that, the vast majority of business functions will operate on an in memory representation of their objects. Using the relational algebra and a column-based organization of data storage will allow us to revolutionize transactional applications while providing an optimal platform for analytical data processing. The unification of OLTP and OLAP workloads on a shared architecture and the reintegration of planning activities promise significant gains in application development while simplifying enterprise systems drastically. The latest trends in computer technology -- e.g. blade architecture, multiple CPUs per blade with multiple cores per CPU allow for a significant parallelization of application processes. The organization of data in columns supports the parallel use of cores for filtering and aggregation. Elements of application logic can be implemented as highly efficient stored procedures operating on columns. The vast increase in main memory combined with improvements in L1--, L2--, L3--caching, together with the high data compression rate column storage will allow us to support substantial data volumes on one single blade. Distributing data across multiple blades using a shared nothing approach provides further scalability."
"Providing an integrated access to multiple heterogeneous sources is a challenging issue in global information systems for cooperation and interoperability. In this context, two fundamental problems arise. First, how to determine if the sources contain semantically related information, that is, information related to the same or similar real-world concept(s). Second, how to handle semantic heterogeneity to support integration and uniform query interfaces. Complicating factors with respect to conventional view integration techniques are related to the fact that the sources to be integrated already exist and that semantic heterogeneity occurs on the large-scale, involving terminology, structure, and context of the involved sources, with respect to geographical, organizational, and functional aspects related to information use. Moreover, to meet the requirements of global, Internet-based information systems, it is important that tools developed for supporting these activities are semi-automatic and scalable as much as possible. The goal of this paper is to describe the MOMIS [4, 5] (Mediator envirOnment for Multiple Information Sources) approach to the integration and query of multiple, heterogeneous information sources, containing structured and semistructured data. MOMIS has been conceived as a joint collaboration between University of Milano and Modena in the framework of the INTERDATA national research project, aiming at providing methods and tools for data management in Internet-based information systems. The knowledge in the Common Thesaurus is then exploited for the identification of semantically related information in ODL<subscrpt>I<3</subscrpt> descriptions of different sources and for their integration at the global level. Mapping rules and integrity constraints are defined at the global level to express the relationships holding between the integrated description and the sources descriptions.  ODB-Tools, supporting OLCD and description logic inference techniques, allows the analysis of sources descriptions for generating a consistent Common Thesaurus and provides support for semantic optimization of queries at the global level, based on defined mapping rules and integrity constraints."
"ions in RBE and the WYSIWIG process of programming starting from an example. Rendering By Example Rendering By Example (RBE) was proposed in [KZ95] as a declarative language to express a rendering of data, where a rendering is defined as a presentation of data with subsequent browsing and interaction semantics. A rendering of data consists of a set of screen widgets populated with data. Such rendering applications allow the browsing and interaction with the data in ways specific to that application. These application-specific rendering applications facilitate the user to find and assimilate the data. Rendering of data is widely used in most applications that have a GUI interface and therefore is not a new concept. But the novelty here is the process of constructing such rendering applications. Traditional programming using a state of the art GUI builder would require the following steps. "
"@ that permits users to determine the source and processing of data for debugging purposes. We will present the AJAX system applied to two real world problems: the consolidation of a telecommunication database, and the conversion of a dirty database of bibliographic references into a set of clean, normalized, and redundancy free relational tables maintaining the same data."
"This paper introduces a new approach to database disk buffering, called the LRU-K method. The basic idea of LRU-K is to keep track of the times of the last K references to popular database pages, using this information to statistically estimate the interarrival times of references on a page by page basis. Although the LRU-K approach performs optimal statistical inference under relatively standard assumptions, it is fairly simple and incurs little bookkeeping overhead. As we demonstrate with simulation experiments, the LRU-K algorithm surpasses conventional buffering algorithms in discriminating between frequently and infrequently referenced pages. In fact, LRU-K can approach the behavior of buffering algorithms in which page sets with known access frequencies are manually assigned to different buffer pools of specifically tuned sizes. Unlike such customized buffering algorithms however, the LRU-K method is self-tuning, and does not rely on external hints about workload characteristics. Furthermore, the LRU-K algorithm adapts in real time to changing patterns of access."
"Many applications that consist of streams of data are inherently distributed. Since input stream rates and other system parameters such as the amount of available computing resources can fluctuate significantly, a stream query plan must be able to adapt to these changes. Routing tuples between operators of a distributed stream query plan is used in several data stream management systems as an adaptive query optimization technique. The routing policy used can have a significant impact on system performance. In this paper, we use a queuing network to model a distributed stream query plan and define performance metrics for response time and system throughput. We also propose and evaluate several practical routing policies for a distributed stream management system. The performance results of these policies are compared using a discrete event simulator. Finally, we study the impact of the routing policy on system throughput and resource allocation when computing resources can be shared between operators."
"There has been much research on various aspects of Approximate Query Processing (AQP), such as different sampling strategies, error estimation mechanisms, and various types of data synopses. However, many subtle challenges arise when building an actual AQP engine that can be deployed and used by real world applications. These subtleties are often ignored (or at least not elaborated) by the theoretical literature and academic prototypes alike. For the first time to the best of our knowledge, in this article, we focus on these subtle challenges that one must address when designing an AQP system. Our intention for this article is to serve as a handbook listing critical design choices that database practitioners must be aware of when building or using an AQP system, not to prescribe a specific solution to each challenge."
"Today, data plays an important role in people¡¯s daily activities. With the help of some database applications such as decision support systems and customer relationship management systems (CRM), useful information or knowledge could be derived from large quantities of data. However, investigations show that many such applications fail to work successfully. There are many reasons to cause the failure, such as poor system infrastructure design or query performance. But nothing is more certain to yield failure than lack of concern for the issue of data quality. High quality of data is a key to today¡¯s business success. The quality of any large real world data set depends on a number of factors among which the source of the data is often the crucial factor. It has now been recognized that an inordinate proportion of data in most data sources is dirty. Obviously, a database application with a high proportion of dirty data is not reliable for the purpose of data mining or deriving business intelligence and the quality of decisions made on the basis of such business intelligence is also unreliable. In order to ensure high quality of data, enterprises need to have a process, methodologies and resources to monitor and analyze the quality of data, methodologies for preventing and/or detecting and repairing dirty data. This thesis is focusing on the improvement of data quality in database applications with the help of current data cleaning methods. It provides a systematic and comparative description of the research issues related to the improvement of the quality of data, and has addressed a number of research issues related to data cleaning. In the first part of the thesis, related literature of data cleaning and data quality are reviewed and discussed. "
"We present a platform for Web services. Web services are implemented in a special XML programming language called XL [1, 2]. A Web service receives an XML message as input and returns an XML message as output. The platform supports a number of features that are particularly useful to implement Web services; e.g., logging, timetables, conversations, workflow management, automatic transactions, security. Our platform is going to be compliant with all W3C standards and emerging proposals. The programming language is very abstract and can be optimized automatically (like SQL). Furthermore, the platform allows to integrate Web services that are written in XL and other programming languages."
"The Prospector Multimedia Object Manager prototype is a general-purpose content analysis multimedia server designed for massively parallel processor environments. Prospector defines and manipulates user defined functions which are invoked in parallel to analyze/manipulate the contents of multimedia objects. Several computationally intensive applications of this technology based on large persistent datasets include: fingerprint matching, signature verification, face recognition, and speech recognition/translation [OIS96]."
"A data warehouse is an integrated database whose data is collected from several data sources, and supports on-line analytical processing (OLAP). Typically, a query to the data warehouse tends to be complex and involves a large volume of data. To keep the data at the warehouse consistent with the source data, changes to the data sources should be propagated to the data warehouse periodically. Because the propagation of the changes (maintenance) is batch processing, it takes long time. Since both query transactions and maintenance transactions are long and involve large volumes of data, traditional concurrency control mechanisms such as two-phase locking are not adequate for a data warehouse environment. We propose a multi-version concurrency control mechanism suited for data warehouses which use multi-dimensional OLAP (MOLAP) servers. We call the mechanism multiversion concurrency control for data warehouses (MVCCDW). To our knowledge, our work is the first attempt to exploit versions for online data warehouse maintenance in a MOLAP environment. MVCC-DW guarantees the serializability of concurrent transactions. Transactions running under the mechanism do not block each other and do not need to place locks."
"It is striking that the optimization of disjunctive queries-i.e. those which contain at least one OR-connective in the query predicate-has been vastly neglected in the literature, as well as in commercial systems. In this paper, we propose a novel technique, called bypass processing, for evaluating such disjunctive queries. The bypass processing technique is based on new selection and join operators that produce two output streams: the TRUE-stream with tuples satisfying the selection (join) predicate and the FALSE-stream with tuples not satisfying the corresponding predicate. Splitting the tuple streams in this way enables us to ""bypass"" costly predicates whenever the ""fate"" of the corresponding tuple (stream) can be determined without evaluating this predicate. In the paper, we show how to systematically generate bypass evaluation plans utilizing a bottom-up building-block approach. We show that our evaluation technique allows us to incorporate the standard SQL semantics of null values. For this, we devise two different approaches: one is based on explicitly incorporating three-valued logic into the evaluation plans; the other one relies on two-valued logic by ""moving"" all negations to atomic conditions of the selection predicate. We describe how to extend an iterator-based query engine to support bypass evaluation with little extra overhead. This query engine was used to quantitatively evaluate the bypass evaluation plans against the traditional evaluation techniques utilizing a CNFor DNF-based query predicate."
"In current warehouse systems, the warehouse administrator is given complete authority to grant user permissions. She is trusted to grant only permissions that respect the security needs of the underlying data sources, but has no tools to ascertain what those needs might be, or to detect changes. We believe that such trust is rarely a good idea, and often is not possible. In earlier papers, we proposed a different strategy, in which source permissions are used to automatically derive corresponding warehouse permissions. In this paper we pull the techniques together, identify concepts missing from standard SQL permissions, and show how to extend the syntax of SQL grant commands to include them."
"The paper shows how modern architectures can be used to speed up ranking algorithms. In the paper ¡°On optimality-ratio and coverage in ranking of joined search results¡±, the authors study a novel ranking problem. Instead of ranking individual items, they consider ranking of combinations of items, e.g., a combination of a hotel and two restaurants. They study the semantics and query processing algorithms in this context. The paper shows the kind of new ranking problems that emerge in these new-age applications. The paper titled ¡°Distributed top-k query processing by exploiting skyline summaries¡± studies top-k processing in distributed environments. With increasing volumes of data, the data is typically distributed over multiple servers. "
"Descriptions of new indexing techniques are a common outcome of database research, but these descriptions are sometimes marred by poor methodology and a lack of comparison to other schemes. In this paper we describe a framework for presentation and comparison of indexing schemes that we believe sets a minimum standard for development and dissemination of research results in this area."
"In this paper a formal model for the domain of Internet search is presented that makes it possible to quantify the relations between important parameters of a distributed search architecture. Among these are physical network parameters, query frequency, required currency of search results, change rate of the data to be searched, logical network topology, and total bandwidth consumption for answering one query. The model is then used to compute many important relations between the various parameters. The results can be used to quantitatively assess, streamline, and optimize distributed Internet search architectures.    The results back the general perception that a centralized approach to Internet-scale search will no longer be able to provide the desired coverage and currency, especially given that the Internet's content keeps growing much faster than the bandwidth available to index it. Using a hierarchical distribution approach and using change-based update notications instead of polling for changes allows to address sets of objects that are several orders of magnitude larger than what is possible with a centralized approach. Yet, using such an approach does not signicantly increase the total bandwidth required for a single query per object reached by the search."
"Digital watermarking for relational databases emerged as a candidate solution to provide copyright protection, tamper detection, traitor tracing, maintaining integrity of relational data. Many watermarking techniques have been proposed in the literature to address these purposes. In this paper, we survey the current state-of-theart and we classify them according to their intent, the way they express the watermark, the cover type, the granularity level, and their verifiability."
"Constrained gradient analysis (similar to the ¡°cubegrade¡± problem posed by Imielinski, et al. [9]) is to extract pairs of similar cell characteristics associated with big changes in measure in a data cube. Cells are considered similar if they are related by roll-up, drill-down, or 1-dimensional mutation operation. Constrained gradient queries are expressive, capable of capturing trends in data and answering ¡°what-if¡± questions. To facilitate our discussion, we call one cell in a gradient pair probe cell and the other gradient cell. An efficient algorithm is developed, which pushes constraints deep into the computation process, finding all gradient-probe cell pairs in one pass. It explores bi-directional pruning between probe cells and gradient cells, utilizing transformed measures and dimensions. Moreover, it adopts a hyper-tree structure and an H-cubing method to compress data and maximize sharing of computation. Our performance study shows that this algorithm is efficient and scalable."
"The W3C XQuery language recommendation, based on a hierarchical and ordered document model, supports a wide variety of constructs and use cases. There is a diversity of approaches and strategies for evaluating XQuery expressions, in many cases only dealing with limited subsets of the language. In this paper we describe an implementation approach that handles XQuery with arbitrarily-nested FLWR expressions, element constructors and built-in functions (including structural comparisons). Our proposal maps an XQuery expression to a single equivalent SQL query using a novel dynamic interval encoding of a collection of XML documents as relations, augmented with information tied to the query evaluation environment. The dynamic interval technique enables (suitably enhanced) relational engines to produce predictably good query plans that do not preclude the use of sort-merge join query operators. The benefits are realized despite the challenges presented by intermediate results that create arbitrary documents and the need to preserve document order as prescribed by semantics of XQuery. Finally, our experimental results demonstrate that (native or relational) XML systems can benefit from the above technique to avoid a quadratic scale up penalty that effectively prevents the evaluation of nested FLWR expressions for large documents."
"XML has established itself over-the recent years as THE standard for representing data in scientific and business applications. Starting out as a standard data exchange format for the Web, it has become instrumental in the development of electronic commerce applications and online information services, and draws in its tailwind a multitude of standardization efforts for all kinds of applications. Documents are not only used for representing multimedia information content but also for many other purposes, like the representation of meta-information and the specification of component interfaces, protocols, and processes. As a consequence, the amount of XML data being stored and processed is large and will be increasing at an astonishing rate. This has caused XML data management to become a focus of research efforts in the database conmmnity. "
"Abstract.In a variety of applications, we need to keep track of the development of a data set over time. For maintaining and querying these multiversion data efficiently, external storage structures are an absolute necessity. We propose a multiversion B-tree that supports insertions and deletions of data items at the current version and range queries and exact match queries for any version, current or past. Our multiversion B-tree is asymptotically optimal in the sense that the time and space bounds are asymptotically the same as those of the (single-version) B-tree in the worst case. The technique we present for transforming a (single-version) B-tree into a multiversion B-tree is quite general: it applies to a number of hierarchical external access structures with certain properties directly, and it can be modified for others."
"Blood transfusions form a crucial and irreplaceable part in the medical management of many diseases. The collection of blood from voluntary, non-remunerated blood donors from low risk populations is an important measure for ensuring the availability and safety of blood transfusion. In a state like Uttarakhand which is visited by lakhs of visitors during pilgrimage season and where natural calamities and accidents are very common, the availability of blood is of utmost importance. Aim: To find out knowledge, attitude and practices of people towards voluntary blood donation to comprehend the situation and find ways to enhance voluntary blood donation in the state of Uttarakhand. Materials and Methods: Multi stage methodology was designed to target population including general population, influencers (doctors) and supporting organizations (camp organizers, State AIDS Control Society Officials) who were subjected to in-depth interview using pre-structured questionnaires to assess knowledge/awareness about voluntary blood donation, factors preventing and source of knowledge about voluntary blood donation. "
"Materialized views in data warehouses are maintained incrementally, for reasons of efficiency, to present the latest updates to the users. These views are used by many warehouse readers (users) to execute OLAP queries by running several reader sessions and these views are maintained periodically by maintenance transactions. Therefore, there is an inherent problem of maintaining these views while the reader sessions continue to receive consistent data from these views. In this paper, we discuss a method that allows warehouse maintenance transactions to run concurrently with the reader sessions. Concurrency allows the readers to read the data from the views while the maintenance transaction updates these views. In our proposed method we create additional versions of views dynamically that contain only the modified tuples of the views and provide a mechanism to collapse these versions into the views periodically when there are no reader sessions accessing the views. These versions allow the reader sessions to access the old and the new information. The collapsing of the views is done by a low-priority process executing periodically."
"The Distributed Systems Technology Centre (DSTC) framework for workflow specification, verification and management captures workflows transaction-like behavior for long lasting processes. FlowBack is an advanced prototype functionally enhancing an existing workflow management system by providing process backward recovery. It is based on extensive theoretical research, and its architecture and construction assumptions are product independent. FlowBack clearly demonstrates the extent to which generic backward recovery can be automated and system supported. The provision of a solution for handling exceptional business process behavior requiring backward recovery makes workflow solutions more suitable for a large class of applications, therefore opening up new dimensions within the market. For the demonstration purpose, FlowBack operates with IBM FlowMark, one of the leading workflow products."
"This paper is devoted to the dynamic aspect of the IF02 conceptual model, an extension of the semantic IF0 model defined by S. Abite boul and R. Hull. Its original aspects are a ¡°whole-event¡± approach, the use of constructors to express combinations of events, and the modularity and m-usability of specifiecltions in order to optimize the designer¡¯s work. Furthermore, it offers an overview of the rep resented behaviour. To complement the modelling part, IF02 includes a derivation component which performs the implementation of specifications by using an active DBMS."
"In large data warehousing environments, it is often advantageous to provide fast, approximate answers to complex decision support queries using precomputed summary statistics, such as samples. Decision support queries routinely segment the data into groups and then aggregate the information in each group (group-by queries). Depending on the data, there can be a wide disparity between the number of data items in each group. As a result, approximate answers based on uniform random samples of the data can result in poor accuracy for groups with very few data items, since such groups will be represented in the sample by very few (often zero) tuples. In this paper, we propose a general class of techniques for obtaining fast, highly-accurate answers for group-by queries. These techniques rely on precomputed non-uniform (biased) samples of the data. In particular, we propose congressional samples, a hybrid union of uniform and biased samples. Given a fixed amount of space, congressional samples seek to maximize the accuracy for all possible group-by queries on a set of columns. We present a one pass algorithm for constructing a congressional sample and use this technique to also incrementally maintain the sample up-to-date without accessing the base relation. We also evaluate query rewriting strategies for providing approximate answers from congressional samples. Finally, we conduct an extensive set of experiments on the TPC-D database, which demonstrates the efficacy of the techniques proposed."
"Abstract. With respect to the specific requirements of advanced OODB applications, index data structures for type hierarchies in OODBMS have to provide efficient support for multiattribute queries and have to allow index optimization for a particular query profile. We describe the multikey type index and an efficient implementation of this indexing scheme. It meets both requirements: in addition to its multiattribute query capabilities it is designed as a mediator between two standard design alternatives, key-grouping and type-grouping. A prerequisite for the multikey type index is a linearization algorithm which maps type hierarchies to linearly ordered attribute domains in such a way that each subhierarchy is represented by an interval of this domain. The algorithm extends previous results with respect to multiple inheritance. The subsequent evaluation of our proposal focuses on storage space overhead as well as on the number of disk I/O operations needed for query execution. The analytical results for the multikey type index are compared to previously published figures for well-known single-key search structures. The comparison clearly shows the superiority of the multikey type index for a large class of query profiles."
"Abstract. Inter-object references are one of the key concepts of object-relational and object-oriented database systems. In this work, we investigate alternative techniques to implement inter-object references and make the best use of them in query processing, i.e., in evaluating functional joins. We will give a comprehensive overview and performance evaluation of all known techniques for simple (single-valued) as well as multi-valued functional joins. Furthermore, we will describe special order-preserving\/ functional-join techniques that are particularly attractive for decision support queries that require ordered results. While most of the presentation of this paper is focused on object-relational and object-oriented database systems, some of the results can also be applied to plain relational databases because index nested-loop joins\/ along key/foreign-key relationships, as they are frequently found in relational databases, are just one particular way to execute a functional join."
"As databases get widely deployed, it becomes increasingly important to reduce the overhead of database administration. An important aspect of data administration that critically influences performance is the ability to select indexes for a database. In order to decide the right indexes for a database, it is crucial for the database administrator (DBA) to be able to perform a quantitative analysis of the existing indexes. Furthermore, the DBA should have the ability to propose hypothetical (¡°what-if¡±) indexes and quantitatively analyze their impact on performance of the system. Such impact analysis may consist of analyzing workloads over the database, estimating changes in the cost of a workload, and studying index usage while taking into account projected changes in the sizes of the database tables. In this paper we describe a novel index analysis utility that we have prototyped for Microsoft SQL Server 7.0. We describe the interfaces exposed by this utility that can be leveraged by a variety of front-end tools and sketch important aspects of the user interfaces enabled by the utility. We also discuss the implementation techniques for efficiently supporting ¡°what-if¡± indexes. Our framework can be extended to incorporate analysis of other aspects of physical database design."
"Applications like multimedia retrieval require efficient support for similarity search on large data collections. Yet, nearest neighbor search is a difficult problem in high dimensional spaces, rendering efficient applications hard to realize: index structures degrade rapidly with increasing dimensionality, while sequential search is not an attractive solution for repositories with millions of objects. This paper approaches the problem from a different angle. A solution is sought in an unconventional storage scheme, that opens up a new range of techniques for processing k-NN queries, especially suited for high dimensional spaces. The suggested (physical) database design accommodates well a novel variant of branch-and-bound search, that reduces the high dimensional space quickly to a small candidate set. The paper provides insight in applying this idea to k-NN search using two similarity metrics commonly encountered in image database applications, and discusses techniques for its implementation in relational database systems. The effectiveness of the proposed method is evaluated empirically on both real and synthetic data sets, reporting the significant improvements in response time yielded."
"Summary: The requeening process was investigated under emergency conditions in honey bee colonies (Apis mellifera L.). The progression of queen cell construction was closely monitored after removal of the mother queen, and the newly-emerged queens were measured for several physical traits to quantify their reproductive potential (= quality). The results suggest that workers regulate the queen rearing process by differentially constructing cells. Workers built different numbers of queens cells from different ages of brood and non-randomly destroyed over half (53%) of the initiated cells before their emergence. For those queens whose cells were not torn down, the variation in reproductive quality was limited, varying only slightly among age groups for queen size. Several hypotheses are discussed which might explain the adaptive benefit of worker regulation during queen rearing."
"Global clustering has rarely been investigated in the area of spatial database systems although dramatic performance improvements can be achieved by using suitable techniques. In this paper, we propose a simple approach to global clustering called cluster organization. We will demonstrate that this cluster organization leads to considerable performance improvements without any algorithmic overhead. Based on real geographic data, we perform a detailed empirical performance evaluation and compare the cluster organization to other organization models not using global clustering. We will show that global clustering speeds up the processing of window queries as well as spatial joins without decreasing the performance of the insertion of new objects and of selective queries such as point queries. The spatial join is sped up by a factor of about 4, whereas non-selective window queries are accelerated by even higher speed up factors."
"Object oriented databases provide rich structuring capabilities to organize the objects being relevant for a given application. Due to the possible complexity of object structures, path expressions have become accepted as a concise syntactical means to reference objects. Even though known approaches to path expressions provide quite elegant access to objects, there seems to be still a need to extend the applicability of path expressions. The rule-language PathLog proposed in the current paper generalizes path expressions in several ways. PathLog adds a second dimension to path expressions which makes it possible to use only one path in situations where known one-dimensional path expressions require a conjunction of several paths. In addition, a path expression can also be used to reference virtual objects. "
"This paper introduces MICP, a novel multiversion integrated cache replacement and prefetching algorithm designed for efficient cache and transaction management in hybrid data delivery networks. MICP takes into account the dynamically and sporadically changing cost/benefit ratios of cached and/or disseminated object versions by making cache replacement and prefetching decisions sensitive to the objects' access probabilities, their position in the broadcast cycle, and their update frequency. Additionally, to eliminate the issue of a newly created or outdated, but re-cacheable, object version replacing a version that may not be reacquired from the server, MICP logically divides the client cache into two variable-sized partitions, namely the REC and the NON-REC partitions for maintaining re-cacheable and nonre-cacheable object versions, respectively. Besides judiciously selecting replacement victims, MICP selectively prefetches popular object versions from the broadcast channel in order to further improve transaction response time. A simulation study compares MICP with one offline and two online cache replacement and prefetching algorithms. Performance results for the workloads and system settings considered demonstrate that MICP improves transaction throughput rates by about 18.9% compared to the best performing online algorithm and it performs only 40.8% worse than an adapted version of the offline algorithm P."
"In this paper, we explore the execution of pipelined hash joins in a multiprocessor-based database system. To improve the query execution, an innovative approach on query execution tree selection is proposed to exploit segmented right-deep trees, which are bushy trees of right-deep subtrees. We first derive an analytical model for the execution of a pipeline segment, and then, in light of the model, develop heuristic schemes to determine the query execution plan based on a segmented right-deep tree so that the query can be efficiently executed. As shown by our simulation, the proposed approach, without incurring additional overhead on plan execution, possesses more flexibility in query plan generation, and leads to query plans of significantly better performance than those achievable by the previous schemes using right-deep trees."
"The handling of user preferences is becoming an increasingly important issue in present-day information systems. Among others, preferences are used for information filtering and extraction to reduce the volume of data presented to the user. They are also used to keep track of user profiles and formulate policies to improve and automate decision making.We propose here a simple, logical framework for formulating preferences as preference formulas. The framework does not impose any restrictions on the preference relations, and allows arbitrary operation and predicate signatures in preference formulas. It also makes the composition of preference relations straightforward. We propose a simple, natural embedding of preference formulas into relational algebra (and SQL) through a single  winnow operator parameterized by a preference formula. The embedding makes possible the formulation of complex preference queries, for example, involving aggregation, by piggybacking on existing SQL constructs. It also leads in a natural way to the definition of further, preference-related concepts like ranking. Finally, we present general algebraic laws governing the winnow operator and its interactions with other relational algebra operators. The preconditions on the applicability of the laws are captured by logical formulas. The laws provide a formal foundation for the algebraic optimization of preference queries. We demonstrate the usefulness of our approach through numerous examples."
"Common to all manufacturing companies is the need to control the flow of material from suppliers, through the value adding processes and distribution channels, to customers. The supply chain is the connected series of activities which is concerned with planning, co©\ordinating and controlling material, parts and finished goods from supplier to customer. Traditionally, the flow of material has been considered only at an operational level. No longer, however, can the potential of integrating the supply chain be ignored. Companies that manage the supply chain as a single entity and ensure the appropriate use of tools and techniques in order to meet the needs of the market, will not get left behind in the fight for survival."
"A number of large-scale high energy physics experiments loom on the horizon, several of which will generate many petabytes of scientific data annually. A variety of exploratory projects are underway within the physics computing community to investigate approaches to managing the data. There are conflicting views of this massive data problem: (1) there is far too much data to manage effectively within a genuine database; (2) there is far too much data to manage effectively without a genuine database; and many people hold both views. The purpose of this paper is to begin a dialog between the computational physics and very large database community on such problems, and to simulate research in directions that will be of benefit to both groups. This paper will attempt to outline the nature and scope of these massive data problems, survey several of the approaches being explored by the physics community, and suggest areas in which high energy physicists hope to look to the database community for assistance."
"We are living in an exciting time in the field of clinical research. There are changes occurring that will alter how medical care is provided, and it is the work of clinical research professionals that will lead these changes. In this column, the Chair of ACRP¡¯s Association Board of Trustees considers the impact of genetics in medicine and their application through precision medicine."
"While the XML Stylesheet Language for Transformations (XSLT) was not designed as a query language, it is well-suited for many query-like operations on XML documents including selecting and restructuring data. Further, it actively fulfills the role of an XML query language in modern applications and is widely supported by application platform software. However, the use of database techniques to optimize and execute XSLT has only recently received attention in the research community. In this paper, we focus on the case where XSL transformations are to be run on XML documents defined as views of relational databases. For a subset of XSLT, we present an algorithm to compose a transformation with an XML view, eliminating the need for the XSLT execution. We then describe how to extend this algorithm to handle several additional features of XSLT, including a proposed approach for handling recursion."
"Since multi-dimensional arrays are a natural data structure for supporting multi-dimensional queries, and object-relational (O/R) database systems support multi-dimensional array ADTs (abstract data types), it is natural to ask if a multi-dimensional array-based ADT can be used to improve O/R DBMS performance on multi-dimensional queries. As an initial step toward answering this question, we have implemented a multi-dimensional array in the Paradise O/R DBMS. In this paper, we describe the implementation of this compressed-array ADT and explore its performance for queries including star-join consolidations and selections. We show that, in many cases, the array ADT can provide significantly higher performance than can be obtained by applying techniques such as bitmap indices and star-join algorithms to relational tables."
"Given a set of objects S, a spatio-temporal window query q retrieves the objects of S that will intersect the window during the (future) interval qT. A nearest neighbor query q retrieves the objects of S closest to q during qT. Given a threshold d, a spatio-temporal join retrieves the pairs of objects from two datasets that will come within distance d from each other during qT. In this article, we present probabilistic cost models that estimate the selectivity of spatio-temporal window queries and joins, and the expected distance between a query and its nearest neighbor(s). Our models capture any query/object mobility combination (moving queries, moving objects or both) and any data type (points and rectangles) in arbitrary dimensionality. In addition, we develop specialized spatio-temporal histograms, which take into account both location and velocity information, and can be incrementally maintained. Extensive performance evaluation verifies that the proposed techniques produce highly accurate estimation on both uniform and non-uniform data."
"Evaluating database system performance often requires generating synthetic databases¡ªones having certain statistical properties but filled with dummy information. When evaluating different database designs, it is often necessary to generate several databases and evaluate each design. As database sizes grow to terabytes, generation often takes longer than evaluation. This paper presents several database generation techniques. In particular it discusses: (1) Parallelism to get generation speedup and scaleup. (2) Congruential generators to get dense unique uniform distributions. (3) Special-case discrete logarithms to generate indices concurrent to the base table generation. (4) Modification of (2) to get exponential, normal, and self-similar distributions. The discussion is in terms of generating billion-record SQL databases using C programs running on a shared-nothing computer system consisting of a hundred processors, with a thousand discs. The ideas apply to smaller databases, but large databases present the more difficult problems."
"XQuery is not only useful to query XML in databases, but also to applications that must process XML documents as files or streams. These applications suffer from the limitations of current main-memory XQuery processors which break for rather small documents. In this paper we propose techniques, based on a notion of projection for XML, which can be used to drastically reduce memory requirements in XQuery processors. The main contribution of the paper is a static analysis technique that can identify at compile time which parts of the input document are needed to answer an arbitrary XQuery. We present a loading algorithm that takes the resulting information to build a projected document, which is smaller than the original document, and on which the query yields the same result. We implemented projection in the Galax XQuery processor. Our experiments show that projection reduces memory requirements by a factor of 20 on average, and is effective for a wide variety of queries. In addition, projection results in some speedup during query evaluation."
"Discovery of association rules .is an important database mining problem. Current algorithms for finding association rules require several passes over the analyzed database, and obviously the role of I/O overhead is very significant for very large databases. We present new algorithms that reduce the database activity considerably. The idea is to pick a Random sample, to find using this sample all association rules that probably hold in the whole database, and then to verify the results with the rest of the database. The algorithms thus produce exact association rules, not approximations based on a sample. The approach is, however, probabilistic, and in those rare cases where our sampling method does not produce all association rules, the missing rules can be found in a second pass. Our experiments show that the proposed algorithms can find association rules very efficiently in only one database"
"This article addresses the performance of distributed database systems. Specifically, we present an algorithm for dynamic replication of an object in distributed systems. The algorithm is adaptive in the sence that it changes the replication scheme of the object i.e., the set of processors at which the object inreplicated) as changes occur in the read-write patern of the object (i.e., the number of reads and writes issued by each processor). The algorithm continuously moves the replication scheme towards an optimal one. We show that the algorithm can be combined with the concurrency control and recovery mechanisms of ta distributed database management system. The performance of the algorithm is analyzed theoretically and experimentally. On the way we provide a lower bound on the performance of any dynamic replication algorith."
"Non-conventional database management systems are used to achieve a better performance when dealing with complex data. One fundamental concept of these systems is object identity (OID), because each object in the database has a unique identifier that is used to access and reference it in relationships to other objects. Two approaches can be used for the implementation of OIDs: physical or logical OIDs. In order to manage complex data, was proposed the Multimedia Data Manager Kernel (NuGeM) that uses a logical technique, named Indirect Mapping. This paper proposes an improvement to the technique used by NuGeM, whose original contribution is management of OIDs with a fewer number of disc accesses and less processing, thus reducing management time from the pages and eliminating the problem with exhaustion of OIDs. Also, the technique presented here can be applied to others OODBMSs."
"Welcome to the first article in a new SIGMOD Record column: Distinguished Database Profiles, featuring interviews with pillars of the database community. I am not much of a traveler, but I plan to leave my nest in east central Illinois to bring you a new interview in each issue. In June I traveled to California to join in the festivities associated with Professor Gio Wiederhold¡¯s retirement from Stanford University. While there, I interviewed Gio and his fellow professors Jeff Ullman and Hector Garcia-Molina, so you will find conversations with all three of these Stanford faculty members in upcoming issues of the Record."
"Approximately every five years, a group of database researchers meet to do a self-assessment of our community, including reflections on our impact on the industry as well as challenges facing our research community. This report summarizes the discussion and conclusions of the 9th such meeting, held during October 9-10, 2018 in Seattle."
"Database technology is one of the cornerstones for the new millennium¡¯s IT landscape. However, database systems as a unit of code packaging and deployment are at a crossroad: commercial systems have been adding features for a long time and have now reached complexity that makes them a difficult choice, in terms of their ""gain/pain ratio"", as a central platform for value-added information services such as ERP or e-commerce. It is critical that database systems be easy to manage, predictable in their performance characteristics, and ultimately self-tuning. For this elusive goal, RISC-style simplification of server functionality and interfaces is absolutely crucial. We suggest a radical architectural departure in which database technology is packaged into much smaller RISC-style data managers with lean, specialized APIs, and with built-in self-assessment and auto-tuning capabilities 1. The Need for a New Departure Database technology has an extremely successful track record as a backbone of information technology (IT) throughout the last three decades. High-level declarative query languages like SQL and atomic transactions are key assets in the cost-effective development and maintenance of information systems. Furthermore, database technology continues to play a major role in the trends of our modern cyberspace society with applications ranging from webbased applications/services, and digital libraries to information mining on business as well as scientific data. Thus, database technology has impressively proven its benefits and seems to remain crucially relevant in the new millennium as well. Success is a lousy teacher (to paraphrase Bill Gates), and therefore we should not conclude that the database system, as the unit of engineering, deploying, and operating packaged database technology, is in good shape. A closer look at some important application areas and major trends in the software industry strongly indicates that database systems have an overly low ¡°gain/pain ratio¡±. First, with the dramatic drop of hardware and software prices, the expenses due to human administration and tuning staff dominate the cost of ownership for a database system. The complexity and cost of these feed-and-care tasks is likely to prohibit database systems from further playing their traditionally prominent role in the future IT infrastructure. Next, database technology is more likely to be adopted in unbundled and dispersed form within higher-level application services. "
"Cleaning data of errors in structure and content is important for data warehousing and integration. Current solutions for data cleaning involve many iterations of data ¡°auditing¡± to find errors, and long-running transformations to fix them. Users need to endure long waits, and often write complex transformation scripts. We present Potter¡¯s Wheel, an interactive data cleaning system that tightly integrates transformation and discrepancy detection. Users gradually build transformations to clean the data by adding or undoing transforms on a spreadsheet-like interface; the effect of a transform is shown at once on records visible on screen. These transforms are specified either through simple graphical operations, or by showing the desired effects on example data values. In the background, Potter¡¯s Wheel automatically infers structures for data values in terms of user-defined domains, and accordingly checks for constraint violations. Thus users can gradually build a transformation as discrepancies are found, and clean the data without writing complex programs or enduring long delays."
"The application of the traditional data base models in the important areas of document retrieval and office information systems has not yet yielded great evidence of success. Here we present an alternative model based on array theory. This model appears to be better suited toward other types of information system,while at the same time, it is still applicable to conventional data base operations. An outline of the model is presented, a description of a suitable query language is given and some implementation issues are discussed."
"Decision support systems (DSS) and data warehousing workloads comprise an increasing fraction of the database market today. I/O capacity and associated processing requirements for DSS workloads are increasing at a rapid rate, doubling roughly every nine to twelve months [38]. In response to this increasing storage and computational demand, we present a computer architecture for decision support database servers that utilizes ¡°intelligent¡± disks (IDISKs). IDISKs utilize low-cost embedded general-purpose processing, main memory, and high-speed serial communication links on each disk. IDISKs are connected to each other via these serial links and high-speed crossbar switches, overcoming the I/O bus bottleneck of conventional systems. By off-loading computation from expensive desktop processors, IDISK systems may improve cost-performance. More importantly, the IDISK architecture allows the processing of the system to scale with increasing storage demand."
"LEO is a comprehensive way to repair incorrect statistics and cardinality estimates of a query execution plan. LEO introduces a feedback loop to query optimization that enhances the available information on the database where the most queries have occurred, allowing the optimizer to actually learn from its past mistakes. We demonstrate how LEO learns outdated table access statistics on a TPC-H like database schema and show that LEO improves the estimates for table cardinalities as well as filter factors for single predicates. Thus LEO enables the query optimizer to choose a better query execution plan, resulting in more efficient query processing. We not only demonstrate learning by repetitive execution of a single query, but also illustrate how similar, but not identical queries benefit from learned knowledge. In addition, we show the effect of both learning cardinalities and adjusting related statistics."
"This paper describes algorithms for key deletion in B+-trees. There are published algorithms and pseudocode for searching and inserting keys, but deletion, due to its greater complexity and perceived lesser importance, is glossed over completely or left as an exercise to the reader. To remedy this situation, we provide a well documented flowchart, algorithm, and pseudo-code for deletion, their relation to search and insertion algorithms, and a reference to a freely available, complete B+-tree library written in the C programming language."
"In the early 1980's, researchers recognized that semantic information stored in databases as integrity constraints could be used for query optimization. A new set of techniques called semantic query optimization (SQO) was developed. Some of the ideas developed for SQO have been used commercially, but to the best of our knowledge, no extensive implementations of SQO exist today. In this paper, we describe an implementation of two SQO techniques, Predicate Introduction and Join Elimination, in DB2 Universal Database. We present the implemented algorithms and performance results using the TPCD and APB-1 OLAP benchmarks. Our experiments show that SQO can lead to dramatic query performance improvements. A crucial aspect of our implementation of SQO is the fact that it does not rely on complex integrity constraints (as many previous SQO techniques did); we use only referential integrity constraints and check constraints.  "
"A data warehouse materializes views derived from data that may not reside at the warehouse. Maintaining these views effciently in response to base updates is diffcult, since it may involve querying external sources where the base data reside. This paper considers the problem of view self-maintenance, where the views are maintained without using all the base data. Without full use of the base data, however, maintaining a view unambiguously is not always possible. Thus, the two critical questions that must be addressed are to determine, in a given situation, whether a view is maintainable, and how to maintain it. W e provide algorithms that answer these questions for a general class of views, and for an important subclass, generate SQL queries that test whether a view is self-maintainable and update the view if it is. We improve significantly on previous work by solving the view self-maintenance problem in the presence of multiple views, with optional access to a subset of the base data, and under arbitrary mixes of insertions and deletions. We provide better insight into the problem by showing that view self-maintainability can be reduced to the problem of deciding query containment. "
"Currently, most data accessed on large servers is structured data stored in traditional databases. Networks are LAN based and clients range from simple terminals to powerful workstations. The user is corporate and the application developer is an MIS professional. With the introduction of broadband communications to the home and better than 100-to-1 compression techniques, a new form of network-based computing is emerging. Structured data is still important, but the bulk of data becomes unstructured: audio, video, news feeds, etc. The predominant user becomes the consumer. The predominant client device becomes the television set. The application developer becomes the storyboard developer, director, or the video production engineer. The Oracle Media Server supports access to all types of conventional data stored in Oracle relational and text databases. In addition, we have developed a real-time stream server that supports storage and playback of real-time audio and video data. The Media Server also provides access to data stored in file systems or as binary large objects (images, executables, etc.) The Oracle Media Server provides a platform for distributed client-server computing and access to data over asymmetric real-time networks. A service mechanism allows applications to be split such that client devices (set-top boxes, personal digital assistants, etc.) can focus on presentation, while backend services running in a distributed server complex, provide access to data via messaging or lightweight RPC (Remote Procedure Call)."
"We demonstrate the design and an early prototype of IrisNet (Internet-scale Resource-Intensive Sensor Network services), a common, scalable networked infrastructure for deploying wide area sensing services. IrisNet is a potentially global network of smart sensing nodes, with webcams or other monitoring devices, and organizing nodes that provide the means to query recent and historical sensor-based data. IrisNet exploits the fact that high-volume sensor feeds are typically attached to devices with significant computing power and storage, and running a standard operating system. It uses aggressive filtering, smart query routing, and semantic caching to dramatically reduce network bandwidth utilization and improve query response times, as we demonstrate.    Our demo will present two services built on Iris-Net, from two very different application domains. The first one, a parking space finder, utilizes webcams that monitor parking spaces to answer queries such as the availability of parking spaces near a user's destination. The second one, a distributed infrastructure monitor, uses measurement tools installed in individual nodes of a large distributed infrastructure to answer queries such as average network bandwidth usage of a set of nodes."
"The advent of the World Wide Web has created an explosion in the available on-line information. As the range of potential choices expand, the time and effort required to sort through them also expands. We propose a formal framework for expressing and combining user preferences to address this problem. Preferences can be used to focus search queries and to order the search results. A preference is expressed by the user for an entity which is described by a set of named fields; each field can take on values from a certain type. The * symbol may be used to match any element of that type. A set of preferences can be combined using a generic combine operator which is instantiated with a value function, thus providing a great deal of flexibility. Same preferences can be combined in more than one way and a combination of preferences yields another preference thus providing the closure property. We demonstrate the power of our framework by illustrating how a currently popular personalization system and a real-life application can be realized as special cases of our framework. We also discuss implementation of the framework in a relational setting."
"This paper describes security issues for federated database management systems set up for managing distributed, heterogeneous and autonomous multilevel databases. It builds on our previous work in multilevel secure distributed database management systems and on the results of others' work in federated database systems. In particular, we define a multilevel secure federated database system and discuss issues on heterogeneity, autonomy, security policy and architecture."
"Xmas is an extensible main-memory storage system for high-performance embedded database applications. Xmas not only provides the core functionality of DBMS, such as data persistence, crash recovery, and concurrency control, but also pursues an extensible architecture to meet the requirements from various application areas. One crucial aspect of such extensibility is that an application developer can compose application-specific, high-level operations with a basic set of operations provided by the system. Called composite actions in Xmas, these operations are processed by a customized Xmas server with minimum interaction with application processes, thus improving the overall performance. This paper first presents the architecture and functionality of Xmas, and then demonstrates a simulation of mobile communication service."
"For a large-scale data-intensive environment, such as the World-Wide Web or data warehousing, we often make local copies of remote data sources. Due to limited network and computational resources, however, it is often difficult to monitor the sources constantly to check for changes and to download changed data items to the copies. In this scenario, our goal is to detect as many changes as we can using the fixed download resources that we have. In this paper we propose three sampling-based download policies that can identify more changed data items effectively. In our sampling-based approach, we first sample a small number of data items from each data source and download more data items from the sources with more changed samples. We analyze the effectiveness of the sampling-based policies and compare our proposed policies to existing ones, including the state-of-the-art frequency-based policy in [8, 11]. Our experiments on synthetic and real-world data will show the relative merits of various policies and the great potential of our sampling-based policy. In certain cases, our sampling-based policy could download twice as many changed items as the best existing policy."
"Personalization of e-services poses new challenges to database technology, demanding a powerful and flexible modeling technique for complex preferences. Preference queries have to be answered cooperatively by treating preferences as soft constraints, attempting a best possible match-making. We propose a strict partial order semantics for preferences, which closely matches people's intuition. A variety of natural and of sophisticated preferences are covered by this model. We show how to inductively construct complex preferences by means of various preference constructors. This model is the key to a new discipline called preference engineering and to a preference algebra. Given the Best-Matches-Only (BMO) query model we investigate how complex preference queries can be decomposed into simpler ones, preparing the ground for divide & conquer algorithms. Standard SQL and XPATH can be extended seamlessly by such preferences (presented in detail in the companion paper [15]). We believe that this model is appropriate to extend database technology towards effective support of personalization."
"The constraint theory developed for traditional structured databases no longer applies to XML data. Thus, many efforts focus on the key constraints for XML. In the paper, motivated by the problem encountered in the evaluation of change detection for XML documents, we present the notion of multi-instance-based key, which can be fundamental to a highly efficient change detection algorithm."
"s [41, 42]. academia [1932, 1926, 2267, 2275]. academic [1908, 2441]. acceleration [1869]. Access [2370, 13, 38, 1530, 1620, 1555, 2106, 1643, 1410, 602, 1672, 1033, 531, 601, 803, 1532, 1531, 949, 2204, 1455, 657, 598, 1263, 1086, 749, 409, 1969, 319, 2119, 450, 872, 1808, 171, 1559, 238, 821, 812, 1209, 1198, 694, 126, 1357, 883, 2139]. accesses [406]. Accessing [1295, 127, 515]. Accommodating [626]. account [1889]. accounting [679]. accrued [2385]. Accurate [276, 855]. achieve [858]. Achievements [1238, 619, 627]. ACID [1688]. ACM [38, 2139, 2216, 14, 2106, 2290, 2291, 42, 2239, 2445, 13, 2472, 2475, 2476, 2477, 2479, 2480, 1580, 1099, 2478, 2130, 2474, 1946, 1697, 2213, 2029, 2143, 2319, 2397, 2262]. ACM-SIGFIDET [38, 14]. Acquisition [288]. Across [1645, 2393, 1936]. ACT [1322]. ACT-NET [1322]. ACTA [586]. action [761]. Actions [1329]. activation [851]. Active [1322, 1239, 970, 833, 1471, 272, 1574, 1407, 1071, 1321, 1236, 1174, 420, 1171, 546, 1914, 1178, 1470, 766, 1098, 521, 1228, 1444, 1126, 1065]. Activities [136, 984, 216, 156, 1965, 587, 67, 748, 820]. activity [1311, 196]. Actual [211]. Ad [1394, 2001, 2056, 3]. ad-hoc [2001]. Ada [249, 458]. ADAM [1897]. adapt [2406]. Adaptable [1807]. adaptation [2113, 2328, 1209]. Adapting [1121, 254]. Adaptive [1730, 1675, 1002, 1642, 1024, 1826, 1112, 1737, 304, 1282, 307, 1809, 567]. ADBIS¡¯2001 [1931]. ADBMS [1321, 1322]. adding [463]. Addison [2043, 66]. Addison-Wesley [66]. Address [1148, 749, 1147, 642]. Addressing [1199]. ADEPT [1588]. Administering [221, 1303]. Administration [1478, 53]. Ado [1317]. ADO.NET [2236]. ADS [1071]. Advanced [1881, 952, 740, 1765, 2405, 1062, 678, 924, 1177]. Advancements [2105]. Advances [1227, 1931]. advantage [1163]. adventure [2310]. adversarial [2337]. Affiliation [2402]. after [1121]. again [1875]. against [471, 1939]. Agenda [1040]. Agent [1386, 1607, 2047, 1588, 1919, 1198, 2065]. Agent-Based [1386, 1607, 1588, 1198]."
"This paper describes the ACM Multimedia '94 Conference Workshop on Multimedia Database Management Systems held on 21 October 1994 in San Francisco, California. The workshop consisted of four sessions: designing multimedia database management systems, video and continuous media service, multimedia storage and retrieval management, and miscellaneous topics in multimedia data management. The workshop concluded with a discussion session on directions for multimedia database management. Twenty-eight participants from U.S.A., U.K., Germany, Norway, and Egypt attended the workshop."
"This paper describes our ongoing work developing the Stanford Stream Data Manager (STREAM), a system for executing continuous queries over multiple continuous data streams. The STREAM system supports a declarative query language, and it copes with high data rates and query workloads by providing approximate answers when resources are limited. This paper describes specific contributions made so far and enumerates our next steps in developing a general-purpose Data Stream Management System."
"A book title cannot be more timely or accurate. Information rules society and it always has. The key difference is, that in our generation, the manner in which information is managed is more apparent to the everyday person and as more information becomes readily available the curse is that information can overload and intimidate us with little or no effort. Prior to the personal computer the everyday person could more easily manage the flow¡ªsuch is not the case today. Throw into this fray the fact that information is a force in economics and the everyday person may become bewildered and perplexed. Many of these concerns are addressed in this excellent new book that focuses on the information economy and its effect on society and culture. In ten engaging chapters, key concepts such as pricing, versioning, rights management, recognizing and managing lock-in, networks, cooperation and compatibility, standards, and information policy are dissected, discussed, and explained. Most chapters end with lessons that reflect key points made in the chapter. The first chapter presents the foundation of the thesis of the book¡ªthe material is relatively general in nature¡ªand sets the stage for the following nine interesting chapters. In discussing pricing, the authors cite the case of Encyclopedia Britannica and its inability to compete with the more popular and less expensive Microsoft product, Encarta. An associated concept, ¡°versioning¡± is discussed and the authors show how a business can offer information products in different versions for differing markets to the benefit of the bottom line. The heady and confusion issue of copyright management, especially as related to internet economy is examined in chapter four of the book. Another issue of concern, lock-in, which results from switching from one technology to another, is discussed in chapters five and six. In chapter seven the authors discuss how the old industrial economy was driven by economies of scale whereas the information economy is driven by economics of networks. The last three chapters push the envelope and advise the reader how to affect real changes in their relationship with the information economy. The last chapter is key in that it discusses current government information policies in light of advice provided earlier in the book. This book may be one of the best to examine the theory and implications of the information economy. Although written by heavyweights in the field of economics and information management, the authors present a well written and thoughtful treatment of a subject that non-academics and academics alike should enjoy and refer to often. More importantly, this book offers direct advice that could well affect the bottom line of many entrepreneurs and existing companies."
"Approximating the joint data distribution of a multi-dimensional data set through a compact and accurate histogram synopsis is a fundamental problem arising in numerous practical scenarios, including query optimization and approximate query answering. Existing solutions either rely on simplistic independence assumptions or try to directly approximate the full joint data distribution over the complete set of attributes. Unfortunately, both approaches are doomed to fail for high-dimensional data sets with complex correlation patterns between attributes. In this paper, we propose a novel approach to histogram-based synopses that employs the solid foundation of statistical interaction models to explicitly identify and exploit the statistical characteristics of the data. Abstractly, our key idea is to break the synopsis into (1) a statistical interaction model that accurately captures significant correlation and independence patterns in data, and (2) a collection of histograms on low-dimensional marginals that, based on the model, can provide accurate approximations of the overall joint data distribution. Extensive experimental results with several real-life data sets verify the effectiveness of our approach. An important aspect of our general, model-based methodology is that it can be used to enhance the performance of other synopsis techniques that are based on data-space partitioning (e.g., wavelets) by providing an effective tool to deal with the ¡°dimensionality curse¡±."
"While standardization efforts for XML query languages have been progressing, researchers and users increasingly focus on the database technology that has to deliver on the new challenges that the abundance of XML documents poses to data management: validation, performance evaluation and optimization of XML query processors are the upcoming issues. Following a long tradition in database research, we provide a framework to assess the abilities of an XML database to cope with a broad range of different query types typically encountered in real-world scenarios. The benchmark can help both implementors and users to compare XML databases in a standardized application scenario. To this end, we offer a set of queries where each query is intended to challenge a particular aspect of the query processor. The overall workload we propose consists of a scalable document database and a concise, yet comprehensive set of queries which covers the major aspects of XML query processing ranging from textual features to data analysis queries and ad hoc queries. We complement our research with results we obtained from running the benchmark on several XML database platforms. These results are intended to give a first baseline and illustrate the state of the art."
"s [41, 42]. academia [1932, 1926, 2267, 2275]. academic [1908, 2441]. acceleration [1869]. Access [2370, 13, 38, 1530, 1620, 1555, 2106, 1643, 1410, 602, 1672, 1033, 531, 601, 803, 1532, 1531, 949, 2204, 1455, 657, 598, 1263, 1086, 749, 409, 1969, 319, 2119, 450, 872, 1808, 171, 1559, 238, 821, 812, 1209, 1198, 694, 126, 1357, 883, 2139]. accesses [406]. Accessing [1295, 127, 515]. Accommodating [626]. account [1889]. accounting [679]. accrued [2385]. Accurate [276, 855]. achieve [858]. Achievements [1238, 619, 627]. ACID [1688]. ACM [38, 2139, 2216, 14, 2106, 2290, 2291, 42, 2239, 2445, 13, 2472, 2475, 2476, 2477, 2479, 2480, 1580, 1099, 2478, 2130, 2474, 1946, 1697, 2213, 2029, 2143, 2319, 2397, 2262]. ACM-SIGFIDET [38, 14]. Acquisition [288]. Across [1645, 2393, 1936]. ACT [1322]. ACT-NET [1322]. ACTA [586]. action [761]. Actions [1329]. activation [851]. Active [1322, 1239, 970, 833, 1471, 272, 1574, 1407, 1071, 1321, 1236, 1174, 420, 1171, 546, 1914, 1178, 1470, 766, 1098, 521, 1228, 1444, 1126, 1065]. Activities [136, 984, 216, 156, 1965, 587, 67, 748, 820]. activity [1311, 196]. Actual [211]. Ad [1394, 2001, 2056, 3]. ad-hoc [2001]. Ada [249, 458]. ADAM [1897]. adapt [2406]. Adaptable [1807]. adaptation [2113, 2328, 1209]. Adapting [1121, 254]. Adaptive [1730, 1675, 1002, 1642, 1024, 1826, 1112, 1737, 304, 1282, 307, 1809, 567]. ADBIS¡¯2001 [1931]. ADBMS [1321, 1322]. adding [463]. Addison [2043, 66]. Addison-Wesley [66]. Address [1148, 749, 1147, 642]. Addressing [1199]. ADEPT [1588]. Administering [221, 1303]. Administration [1478, 53]. Ado [1317]. ADO.NET [2236]. ADS [1071]. Advanced [1881, 952, 740, 1765, 2405, 1062, 678, 924, 1177]. Advancements [2105]. Advances [1227, 1931]. advantage [1163]. adventure [2310]. adversarial [2337]. Affiliation [2402]. after [1121]. again [1875]. against [471, 1939]. Agenda [1040]. Agent [1386, 1607, 2047, 1588, 1919, 1198, 2065]. Agent-Based [1386, 1607, 1588, 1198]."
"In modern database applications the similarity or dissimilarity of complex objects is examined by performing distance-based queries (DBQs) on data of high dimensionality. The R-tree and its variations are commonly cited multidimensional access methods that can beused for answering such queries. Although the related algorithms work well for low-dimensional data spaces, their performance degrades as the number of dimensions increases (dimensionality curse). In order to obtain acceptable response time in high-dimensional data spaces, algorithms that obtain approximate solutions can be used. Approximation techniques, like N-consider (based on the tree structure), ¦Á-allowance and e-approximate (based on distance), or Time-consider (based on time) can be applied in branch-and-bound algorithms for DBQs inorder to control the trade-off between cost and accuracy of the result. In this paper, we improve previous approximate DBQ algorithms by applying a combination of the approximation techniques in the same query algorithm (hybrid approximation scheme). We investigate the performance of these improvements for one of the most representative DBQs (the K-closest pairs query, K-CPQ) in high-dimensional data spaces, as well as the influence of the algorithmic parameters on the control of the trade-off between the response time and the accuracy of the result. The outcome of the experimental evaluation, using synthetic and real datasets, is the derivation of the outperforming DBQ approximate algorithm for large high-dimensional point datasets."
"Existing studies on outliers focus only on the identiication aspect; none provides any inten-sional knowledge of the outliers|by which we mean a description or an explanation of why an identiied outlier is exceptional. For many applications, a description or explanation is at least as vital to the user as the identii-cation aspect. Speciically, intensional knowledge helps the user to: (i) evaluate the validity of the identiied outliers, and (ii) improve one's understanding of the data. The two main issues addressed in this paper are: what kinds of intensional knowledge to provide, and how to optimize the computation of such knowledge. With respect to the rst issue, we propose nding strongest and weak outliers and their corresponding structural intensional knowledge. With respect to the second issue, we rst present a naive and a semi-naive algorithm. "
"In this paper, we present four approaches to providing highly concurrent B+-tree indices in the context of a data-shipping, client-server OODBMS architecture. The first performs all index operations at the server, while the other approaches support varying degrees of client caching and usage of index pages. We have implemented the four approaches, as well as the 2PL approach, in the context of the SHORE OODB system at Wisconsin, and we present experimental results from a performance study based on running SHORE on an IBM SP2 multicomputer. Our results emphasize the need for non-2PL approaches and demonstrate the tradeoffs between 2PL, no-caching, and the three caching alternatives."
"The integration of object-oriented programming concepts with databases is one of the most significant advances in the evolution of database systems. Many aspects of such a combination have been studied, but there are few models to provide security for this richly structured information. We develop an authorization model for object-oriented databases. This model consists of a set of policies, a structure for authorization rules, and algorithms to evaluate access requests against the authorization rules. User access policies are based on the concept of inherited authorization applied along the class structure hierarchy. We propose also a set of administrative policies that allow the control of user access and its decentralization. Finally, we study the effect of class structuring changes on authorization. >"
"XML is rapidly emerging as the new standard for data representation and exchange on the Web. An XML document can be accompanied by a Document Type Descriptor (DTD) which plays the role of a schema for an XML data collection. DTDs contain valuable information on the structure of documents and thus have a crucial role in the efficient storage of XML data, as well as the effective formulation and optimization of XML queries. In this paper, we propose XTRACT, a novel system for inferring a DTD schema for a database of XML documents. Since the DTD syntax incorporates the full expressive power of regular expressions, naive approaches typically fail to produce concise and intuitive DTDs. Instead, the XTRACT inference algorithms employ a sequence of sophisticated steps that involve: (1) finding patterns in the input sequences and replacing them with regular expressions to generate ¡°general¡± candidate DTDs, (2) factoring candidate DTDs using adaptations of algorithms from the logic optimization literature, and (3) applying the Minimum Description Length (MDL) principle to find the best DTD among the candidates. The results of our experiments with real-life and synthetic DTDs demonstrate the effectiveness of XTRACT's approach in inferring concise and semantically meaningful DTD schemas for XML databases."
"Publisher Summary This chapter implements ATLAS, a powerful database language and system that enables users to develop complete data-intensive applications in structured query language (SQL)¡ªby writing new aggregates and table functions in SQL, rather than in procedural languages as in current Object- Relational systems. As a result, ATLAS' SQL is Turing-complete, and is very suitable for advanced data intensive applications, such as data mining and stream queries. The ATLAS system is now available for download along with a suite of applications including various data mining functions that have been coded in ATLAS' SQL, and execute with a modest performance overhead with respect to the same applications written in C/C++. The demonstration reveals ATLAS' internal architecture by focusing on several of its key components, such as the query rewrite module, the query-plan generation module, and the stream-data management engine."
"Publish/Subscribe is the paradigm in which users express long-term interests (¡°subscriptions¡±) and some agent ¡°publishes¡± events (e.g., offers). The job of Publish/Subscribe software is to send events to the owners of subscriptions satisfied by those events. For example, a user subscription may consist of an interest in an airplane of a certain type, not to exceed a certain price. A published event may consist of an offer of an airplane with certain properties including price. Each subscription consists of a conjunction of (attribute, comparison operator, value) predicates. A subscription closely resembles a trigger in that it is a long-lived conditional query associated with an action (usually, informing the subscriber). However, it is less general than a trigger so novel data structures and implementations may enable the creation of more scalable, high performance publish/subscribe systems. This paper describes an attempt at the construction of such algorithms and its implementation. Using a combination of data structures, application-specific caching policies, and application-specific query processing our system can handle 600 events per second for a typical workload containing 6 million subscriptions."
"We define a standard of effectiveness for a database calculus relative to a query language. Effectiveness judges suitability to serve as a processing framework for the query language, and comprises aspects of coverage, manipulability and efficient evaluation. We present the monoid calculus, and argue its effectiveness for object-oriented query languages, exemplified by OQL of ODMG-93. The monoid calculus readily captures such features as multiple collection types, aggregations, arbitrary composition of type constructors and nested query expressions. We also show how to extend the monoid calculus to deal with vectors and arrays in more expressive ways than current query languages do, and illustrate how it can handle identity and updates."
"Continuous data streams arise naturally, for example, in the installations of large telecom and Internet service providers where detailed usage information (Call-Detail-Records, SNMP/RMON packet-flow data, etc.) from different parts of the underlying network needs to be continuously collected and analyzed for interesting trends. Such environments raise a critical need for effective stream-processing algorithms that can provide (typically, approximate) answers to data-analysis queries while utilizing only small space (to maintain concise stream synopses) and small processing time per stream item. In this talk, I will discuss the basic pseudo-random sketching mechanism for building stream synopses and our ongoing work that exploits sketch synopses to build an approximate SQL (multi) query processor. I will also describe our recent results on extending sketching to handle more complex forms of queries and streaming data (e.g., similarity joins over streams of XML trees), and try to identify some challenging open problems in the data-streaming area. DMKD03: 8th ACM SIGMOD Workshop on Research Issues in Data Mining and Knowledge Discovery, 2003 page 1 DMKD03: 8th ACM SIGMOD Workshop on Research Issues in Data Mining and Knowledge Discovery, 2003 page 2 A Symbolic Representation of Time Series, with Implications for Streaming Algorithms Jessica Lin Eamonn Keogh Stefano Lonardi Bill Chiu University of California Riverside Computer Science & Engineering Department Riverside, CA 92521, USA {jessica, eamonn, stelo, bill}@cs.ucr.edu"
"In recent years, there has been an exponential growth in the number of complex documents and texts that require a deeper understanding of machine learning methods to be able to accurately classify texts in many applications. Many machine learning approaches have achieved surpassing results in natural language processing. The success of these learning algorithms relies on their capacity to understand complex models and non-linear relationships within data. However, finding suitable structures, architectures, and techniques for text classification is a challenge for researchers. In this paper, a brief overview of text classification algorithms is discussed. This overview covers different text feature extractions, dimensionality reduction methods, existing algorithms and techniques, and evaluations methods. Finally, the limitations of each technique and their application in real-world problems are discussed."
"1. Document Acquisition There is a broad spectrum of techniques how to acquire documents in such a way, that they are in computerreadable form and can be stored in a document base. This spectrum ranges from fully automatic at low cost via semiautomatic using tools like scanners and optical character recognition (OCR) to manual acquisition according to elaborate rules and regulations. The purpose of high quality document acquisition is to capture the structure and the semantic content of a document not as far as possible but as far as affordable. Presently the state of the art of semiautomatic acquisition of paper documents is scanning followed by OCR. This yields a facsimile image and the text content, but no structure and no real semantics. In many cases the text produced by OCR is low quality and must be corrected to be useful for effective retrieval. Various projects are under way to capture structure and semantics automatically [1,12], but they have not reached sufficient maturity to be used in production environments like libraries or businesses."
"Cost-based XML query optimization calls for accurate estimation of the selectivity of path expressions. Some other interactive and internet applications can also benefit from such estimations. While there are a number of estimation techniques proposed in the literature, almost none of them has any guarantee on the estimation accuracy within a given space limit. In addition, most of them assume that the XML data are more or less static, i.e., with few updates. In this paper, we present a framework for XML path selectivity estimation in a dynamic context. Specifically, we propose a novel data structure, bloom histogram, to approximate XML path frequency distribution within a small space budget and to estimate the path selectivity accurately with the bloom histogram. We obtain the upper bound of its estimation error and discuss the trade-offs between the accuracy and the space limit. To support updates of bloom histograms efficiently when underlying XML data change, a dynamic summary layer is used to keep exact or more detailed XML path information. We demonstrate through our extensive experiments that the new solution can achieve significantly higher accuracy with an even smaller space than the previous methods in both static and dynamic environments."
"Tree patterns forms a natural basis to query tree-structured data such as XML and LDAP. Since the efficiency of tree pattern matching against a tree-structured database depends on the size of the pattern, it is essential to identify and eliminate redundant nodes in the pattern and do so as quickly as possible. In this paper, we study tree pattern minimization both in the absence and in the presence of integrity constraints (ICs) on the underlying tree-structured database. When no ICs are considered, we call the process of minimizing a tree pattern, constraint-independent minimization. We develop a polynomial time algorithm called CIM for this purpose. CIM's efficiency stems from two key properties: (i) a node cannot be redundant unless its children are, and (ii) the order of elimination of redundant nodes is immaterial. When ICs are considered for minimization, we refer to it as constraint-dependent minimization. For tree-structured databases, required child/descendant and type co-occurrence ICs are very natural. Under such ICs, we show that the minimal equivalent query is unique. We show the surprising result that the algorithm obtained by first augmenting the tree pattern using ICS, and then applying CIM, always finds the unique minimal equivalent query; we refer to this algorithm as ACIM. While ACIM is also polynomial time, it can be expensive in practice because of its inherent non-locality. We then present a fast algorithm, CDM, that identifies and eliminates local redundancies due to ICs, based on propagating ¡°information labels¡± up the tree pattern. CDM can be applied prior to ACIM for improving the minimization efficiency. We complement our analytical results with an experimental study that shows the effectiveness of our tree pattern minimization techniques."
"The fourth International Conference on Flexible Query Answering Systems (FQAS'2000) was held at the Academy of Sciences in Warsaw, Poland on October, 25-27, 2000. This series of conferences was launched in 1994 by Troels Andreasen, Henning Christiansen and Henrik Larsen from Roskilde University in Denmark, who have been the main driving force behind this series ever since. The previous FQAS events were held in Denmark in 1994, 1996, mad 1998. The next conference in this series will return to Denmark in 2002."
"We present a structured, iterative methodology for user-centered design and evaluation of VE user interaction. We recommend performing (1) user task analysis followed by (2) expert guidelines-based evaluation, (3) formative user-centered evaluation, and finally (4) comparative evaluation. In this article we first give the motivation and background for our methodology, then we describe each technique in some detail. We applied these techniques to a real-world battlefield visualization VE. Finally, we evaluate why this approach provides a cost-effective strategy for assessing and iteratively improving user interaction in VEs."
"Previous work on functional joins was constrained in two ways: (1) all approaches we know assume references being implemented as physical object identifiers (OIDs) and (2) most approaches are, in addition, limited to single-valued reference attributes. Both are severe limitations since most object-relational and all object-oriented database systems do support nested reference sets and many object systems do implement references as location-independent (logical) OIDs. In this work, we develop a new functional join algorithm that can be used for any realization form for OIDs (physical or logical) and is particularly geared towards supporting functional joins along nested reference sets. The algorithm can be applied to evaluate joins along arbitrarily long path expressions which may include one or more reference sets. The new algorithm generalizes previously proposed partition-based pointer joins by repeatedly applying partitioning with interleaved re-merging before evaluating the next functional join. Consequently, the algorithm is termed P(PM)*M where P stands for partitioning and M denotes merging. Our prototype implementation as well as an analytical assessment based on a cost model prove that this new algorithm performs superior in almost all database configurations. *This work was supported in part by the German National Research Foundation DFG under contracts Ke 401/6-2 and Ke 40117-I."
A brief overview of Nonstop SQL product will be followed by a description of what is different in ServerWare SQL. The current Nonstop SQL optimizer uses a traditional bottom-up dynamic programming optimizer. This is the same type of optimization algorithm used in System R and many commercial products. The optimizer in the new product is a top-down branch and bound ruledriven cost based optimizer similar to work done on the Volcano optimizer.
"Recently the notion of self-similarity has been shown to apply to wide-area and local-area network traffic. In this paper we examine the mechanisms that give rise to the self-similarity of network traffic. We present a hypothesized explanation for the possible self-similarity of traffic by using a particular subset of wide area traffic: traffic due to the World Wide Web (WWW). Using an extensive set of traces of actual user executions of NCSA Mosaic, reflecting over half a million requests for WWW documents, we examine the dependence structure of WWW traffic. While our measurements are not conclusive, we show evidence that WWW traffic exhibits behavior that is consistent with self-similar traffic models. "
"The March 2005 issue of TODS has eight papers invited from the SIGMOD and PODS'2003 conferences. These papers are significantly extended versions of the conference papers, allowing the authors to refine and elaborate without the strictures of a twelve-page limit."
"The SIT-IN (acronym for Integrated Territorial Information System, in Italian) system integrates a historical database, providing information about the temporal evolution of territorial administrative partitions; the Institute's GIS, providing the cartography of the Italian territory down to the census tract level of detail; a statistical data warehouse, providing spatiotemporal data from a number of di erent surveys; and nally an address normalizing/geo-matching system, providing information about the limits of census tracts (e.g. portions of streets or the sides of town squares)."
"The problem of analyzing and classifying conceptual schemas is becomig increasingly important due to the availability of a large number of schemas related to existing applications. The purposes of schema analysis and classification activities can be different: to extract information on intensional properties of legacy systems in order to restructure or migrate to new architectures; to build libraries of reference conceptual components to be used in building new applications in a given domain; and to identify information flows and possible replication of data in an organization. This article proposes a set of techniques for schema analysis and classification to be used separately or in combination. The techniques allow the analyst to derive significant properties from schemas, with human intervention limited as far as possible. In particular, techniques for associating descriptors with schemas, for abstracting reference conceptual schemas based on schema clustering, and for determining schema similarity are presented. A methodology for systematic schema analysis is illustrated, with the purpose of identifying and abstracting into reference components the similar and potentially reusable parts of a set of schemas. Experiences deriving from the application of the proposed techniques and methodology on a large set of Entity-Relationship conceptual schemas of information systems in the Italian Public Administration domain are described"
"Many decision support systems, which utilize association rules for discovering interesting patterns, require the discovery of association rules that vary over time. Such rules describe complicated temporal patterns such as events that occur on the ¡°first working day of every month.¡± In this paper, we study the problem of discovering how association rules vary over time. In particular, we introduce the idea of using a calendar algebra to describe complicated temporal phenomena of interest to the user. We then present algorithms for discovering calendric association rules, which are association rules that follow the patterns set forth in the user supplied calendar expressions. We devise various optimizations that speed up the discovery of calendric association rules. We show, through an extensive series of experiments, that these optimization techniques provide performance benefits ranging from to over a less sophisticated algorithm."
"The DB2 Design Advisor in IBM? DB2? Universal DatabaseTM (DB2 UDB) Version 8.2 for Linux?, UNIX? and Windows? is a tool that, for a given workload, automatically recommends physical design features that are any subset of indexes, materialized query tables (also called materialized views), shared-nothing database partitionings, and multidimensional clustering of tables. Our work is the very first industrial-strength tool that covers the design of as many as four different features, a significant advance to existing tools, which support no more than just indexes and materialized views. Building such a tool is challenging, because of not only the large search space introduced by the interactions among features, but also the extensibility needed by the tool to support additional features in the future. We adopt a novel ""hybrid"" approach in the Design Advisor that allows us to take important interdependencies into account as well as to encapsulate design features as separate components to lower the reengineering cost. The Design Advisor also features a built-in module that automatically reduces the given workload, and therefore provides great scalability for the tool. Our experimental results demonstrate that our tool can quickly provide good physical design recommendations that satisfy users' requirements."
"E-services are business functions made available via the Internet by service providers, and accessible by clients that could be human users or software applications. The main benefit of the e-services environment is that clients are able to dynamically discover the available e-service that best meets their needs, to examine its properties and capabilities, and to determine if and how to access it. However, in order to deliver e-services to clients, service providers are faced with several challenges. In particular, they need to describe e-services in a way that is accessible and understandable by the clients and to advertise them in web directories, so that they can be discovered by brokers as well as by end-users. In this tutorial we discuss the main requirements for models and languages for service description and discovery, and we present relevant approaches proposed by standardization consortia."
"Semistructured data is modeled as a rooted, labeled graph. The simplest kinds of queries on such data are those which traverse paths described by regular path expressions. More complex queries combine several regular path expressions, with complex data restructuring, and with sub-queries. This article addresses the problem of efficient query evaluation on distributed, semistructured databases. In our setting, the nodes of the database are distributed over a fixed number of sites, and the edges are classified into local (with both ends in the same site) and cross edges (with ends in two distinct sites). Efficient evaluation in this context means that the number of communication steps is fixed (independent on the data or the query), and that the total amount of data sent depends only on the number of cross links and of the size of the query's result. We give such algorithms in three different settings. First, for the simple case of queries consisting of a single regular expression; second, for all queries in a calculus for graphs based on structural recursion which in addition to regular path expressions can perform nontrivial restructuring of the graph; and third, for a class of queries we call select-where queries that combine pattern matching and regular path expressions with data restructuring and subqueries. This article also includes a discussion on how these methods can be used to derive efficient view maintenance algorithms."
"Abstract This article discusses the challenges for Database Management in the Internet of Things. We provide scenarios to illustrate the new world that will be produced by the Internet of Things, where physical objects are fully integrated into the information highway. We discuss the different types of data that will be part of the Internet of Things. These include identification, positional, environmental, historical, and descriptive data. We consider the challenges brought by the need to manage vast quantities of data across heterogeneous systems. In particular, we consider the areas of querying, indexing, process modeling, transaction handling, and integration of heterogeneous systems. We refer to the earlier work that might provide solutions for these challenges. Finally we discuss a road map for the Internet of Things and respective technical priorities."
"Data on the Internet is increasingly presented in XML format. This enables novel applications that pose queries over ¡°all the XML data on the Internet.¡± Queries over XML data use path expressions to navigate through the structure of the data, and optimizing these queries requires estimating the selectivity of these path expressions. In this paper, we propose two techniques for estimating the selectivity of simple XML path expressions over complex large-scale XML data as would be handled by Internet-scale applications: path trees and Markov tables. Both techniques work by summarizing the structure of the XML data in a small amount of memory and using this summary for selectivity estimation. We experimentally demonstrate the accuracy of our proposed techniques, and explore the different situations that would favor one technique over the other. We also demonstrate that our proposed techniques are more accurate than the best previously known alternative."
"Publisher Summary The content of an Active eXtensible Markup Language (AXML) document is dynamic, because it is possible to specify when a service call should be activated (for example, when needed, every hour, etc.), and for how long its result should be considered valid. Thus, this simple mechanism allows capturing and combining different styles of data integration, such as warehousing and mediation. To fully take advantage of the use of services, AXML also allows calling continuous services (that provide streams of answers) and services supporting intentional data (AXML document including service calls) as parameters and/or result. The latter feature leads to powerful, recursive integration schemes. The AXML framework is centered on AXML documents , which are XML documents that may contain calls to Web services. When calls included in an AXML document are fired, the latter is enriched by the corresponding results."
"A 20/20 vision in ophthalmology implies a perfect view of things that are in front of you. The term is also used to mean a perfect sight of the things to come. Here we focus on a speculative vision of the VLDB in the year 2020. This panel is the follow-up of the one I organised (with S. Navathe) at the Kyoto VLDB in 1986, with the title: ""Anyone for a VLDB in the Year 2000?"". In that panel, the members discussed the major advances made in the database area and conjectured on its future, following a concern of many researchers that the database area was running out of interesting research topics and therefore it might disappear into other research topics, such as software engineering, operating systems and distributed systems. That did not happen."
"In the last few years, several works in the literature have addressed the problem of data extraction from Web pages. The importance of this problem derives from the fact that, once extracted, the d..."
"Editor's note: For this issue's ""From the Editors,"" I invited Robert Gephart of the University of Al-berta to reflect on his observations as a long-serving , award-winning reviewer of qualitative research for A!vII Over the past two and a half years, I have developed a tremendous respect for Bob's keen eye for evaluating qualitative research submissions , and great admiration for the painstaking advice he provides authors about how to improve their work. As a world-renowned qualitative author himself, Bob is in an excellent position to provide observations about how authors might increase the chances of having their qualitative research accepted for publication at AMI In a three-way electronic mail conversation about the challenges and opportunities of qualitative research , Bob, Tom Lee, and I all concluded that many authors with potentially very interesting data sets don't seem to know how to analyze them to their full potential. This is perhaps not surprising, gi ven the clear predominance of quantitative methods and statistics courses over qualitative ones, particularly in North America, as well as the inherently greater subjectivity involved in designing and analyzing qualitative research. As such, we encouraged Bob to provide a bit of a minitutorial-complete with reference citations and examples of high-quality papers that use particular qualitative approaches-in addition to his observations about qualitative research submitted to AMI The result is a longer-than-usual ""From the Edi-tors"" column. but one that we believe is well worth the extra reading time for anyone interested in producing , reviewing, or attempting to coax greater insights from qualitative research. We are fortunate to have someone with Bob's expertise share his observations, and we hope that his thoughts will prove useful to researchers for many years to come. Sara Rynes Incoming Editor I am thankful to Sara for inviting me to write this editorial column encouraging scholars to submit their qualitative research to the Academy of Man-I wish to thank Torn Lee and Sara Rynes for their helpful comments and encouragement in preparing this editorial. 454 agement Journal. Qualitative research is important to AMI Qualitative research is actively sought and supported by the Journal, its editors, and its editorial review board. Alv1Jhas published many qualitative papers. The coveted A/'v1jBest Article Award has been won by three qualitative papers-Gersick (1989), Isabella (1990), and Dutton and Duckerich (1991)-and by one paper that combined qualitative and quantitative methods: Sutton and Rafuclli, (1988). Despite these successes, most ¡­"
"PM3 is an orthogonally persistent extension of the Modula-3 systems programming language, supporting persistence by reachability from named persistent roots. We describe the design and implementation of the PM3 prototype, and show that its performance is competitive with its nonorthogonal counterparts by direct comparison with the SHORE/C++ language binding to the SHORE object store. Experimental results, using the traversal portions of the OO7 benchmark, reveal that the overheads of orthogonal persistence are not inherently more expensive than for nonorthogonal persistence, and justify our claim that orthogonal persistence deserves a level of acceptance similar to that now emerging for automatic memory management (i.e., ¡°garbage collection¡±), even in performance-conscious settings. The consequence will be safer and more flexible persistent systems that do not compromise performance."
"LeSelect is a mediator system which allows scientists to publish their resources (data and programs) so they can be transparently accessed. The scientists can typically issue queries which access distributed published data and involve the execution of expensive functions (corresponding to programs). Furthermore, the queries can involve large objects, such as images (e.g. archived meteorological satellite data). In this context, the costs of transmitting large objects and invoking expensive functions are the dominant factors of execution time. In this paper, we first propose three query execution techniques which minimize these costs by taking full advantage of the distributed architecture of mediator systems like LeSelect. Then we devise parallel processing strategies for queries including expensive functions. Based on experimentation, we show that it is hard to predict the optimal execution order when dealing with several functions. We propose a new hybrid parallel technique to solve this problem and give some experimental results."
"We propose to extend database systems by a Skyline operation. This operation filters out a set of interesting points from a potentially large set of data points. A point is interesting if it is not dominated by any other point. For example, a hotel might be interesting for somebody traveling to Nassau if no other hotel is both cheaper and closer to the beach. We show how SSL can be extended to pose Skyline queries, present and evaluate alternative algorithms to implement the Skyline operation, and show how this operation can be combined with other database operations, e.g., join."
"Consider a setting in whichDatabase speed and reliability can make the difference between prosperity and ruin. Money for information systems is no object. Data must be accessible from many points on the globe with subsecond response.  The financial industry is exactly such an environment. This tutorial presents case studies in configuration, tuning, and distribution drawn from financial applications. The cases suggest both research and product issues and so should be of interest to the entire Sigmod community."
"This article presents a declarative language, called update calculus, of relational database updates. A formula in update calculus involves conditions for the current database, as well as assertions about a new database. Logical connectives and quantifiers become constructors of complex updates, offering flexible specifications of database transformations. Update calculus can express all nondeterministic database transformations that are polynomial time. For set-at-a-time evaluation of updates, we present a corresponding update algebra. Existing techniques of query processing can be incorporated into update evaluation. We show that updates in update calculus can be translated into expressions in update algebra and vice versa."
"Publisher Summary  The decomposition storage model (DSM) has not found acceptance by the database vendors. Given technology trends and the need for storage architectures that are more aware of disk-arm and cache effects during query processing, DSM is likely to play an important role in the future. A number of the fundamental assumptions upon which the current generation of database systems is based have changed dramatically over the past decade. CPU speeds are improving rapidly and the amount of main memory that is affordable is increasing. While disk capacities have also shown similar improvements, disk times and effective transfer rates (transfer rate/capacity) have improved at a much slower rate (almost a factor of 10 slower). In addition, since it appears that disk capacities are growing faster than database sizes, even the benefits of using parallelism are likely to diminish."
"Research and development in the area of database technology during the past decade is characterised by the striving for better support for applications beyond the traditional world, where primarily high volumes of simply structured data had to be processed efficiently. As a result, future DBMS will include more functionality, and explicitly cover more real world semantics (in various forms) that otherwise would have to be included in applications themselves. Advanced database technology, however, is in a sense ambivalent. While it provides new and much-needed solutions in many important areas, these same solutions often require thorough consideration in order to avoid the introduction of new problems. One such area is database security. In this paper, we consider three prominent areas of nonstandard database technology: object-oriented, active and federated database management systems. In particular, we show which typical security problems (with the focus on access control) have to be solved for these systems. We also give some examples how, on the other hand, these kinds of DBMS and their underlying mechanisms, respectively, can beneficially be used to solve security problems. Further, we discuss the issue of secure design and construction of (special purpose) database management systems in this context. Keyword Codes: K.6.5; H.2.7; H.2.5"
"This paper studies the Candy model, a marked point process introduced by Stoica et al. (2000). We prove Ruelle and local stability, investigate its Markov properties, and discuss how the model may be sampled. Finally, we consider estimation of the model parameters and present some examples."
"The emergence of persistent memory (PM) spurs on redesigns of database system components to gain full exploitation of the persistence and speed of the hardware. One crucial component studied by researchers is persistent indices. However, such studies to date are unsatisfactory in terms of the number of expensive PM writes required for crashconsistency. In this paper, we propose a new persistent index called DPTree (Differential Persistent Tree) to address this. DPTree¡¯s core idea is to batch multiple writes in DRAM persistently and later merge them into a PM component to amortize persistence overhead. DPTree includes several techniques and algorithms to achieve crash-consistency, reduce PM writes significantly, and maintain excellent read performance. To embrace multi-core processors, we present the design of concurrent DPTree. Our experiments on Intel¡¯s Optane DIMMs show that DPTree reduces PM writes by a factor of 1.7x-3x compare to state-of-the-art counterparts. Besides, DPTree has a competitive or better read performance and scales well in multi-core environment. PVLDB Reference Format: Xinjing Zhou, Lidan Shou, Ke Chen, Wei Hu, Gang Chen. DPTree: Differential Indexing for Persistent Memory. PVLDB, 13(4): 421-434, 2019. DOI: https://doi.org/10.14778/3372716.3372717"
"Managing the transactions in real time distributed computing system is not easy, as it has heterogeneously networked computers to solve a single problem. If a transaction runs across some different sites, it may commit at some sites and may failure at another site, leading to an inconsistent transaction. The complexity is increase in real time applications by placing deadlines on the response time of the database system and transactions processing. Such a system needs to process transactions before these deadlines expired. A series of simulation study have been performed to analyze the performance under different transaction management under conditions such as different workloads, distribution methods, execution mode-distribution and parallel etc. The scheduling of data accesses are done in order to meet their deadlines and to minimize the number of transactions that missed deadlines. A new concept is introduced to manage the transactions in database size for originating site and remote site rather than database size computing parameters. With this approach, the system gives a significant improvement in performance."
"The relational model is accepted for its simplicity and eIegance. At the other side the simplicity causes the problem, that most semantic type constructs are not representable as a simple relation. Variant and heterogeneous structures belong to those constructs not adequatly supported by the simple relational model. In this paper we give an overview of the model of flexible relations that allows to model and process arbitrary heterogeneous structures, while preserving the relational philosophy of operating with a single constructor. As flexible relations support both the modeling and the operational aspect of variant structures seamlessly, our model truly helps to further bridge the gap between semantic and operational data models. We discuss the structural part of the moQ.el and introduce an algebra for flexible relations. Further we examine a subdass of flexible relations, that can be processed as efficiently as the simple relational model, and show that this subdass possesses desirable structural normal form properties. In addition, we point out that our approach exceeds the objectoriented paradigm in modeling power, typing precision, and query optimization potential."
"Abstract. The requirements of wide-area distributed database systems differ dramatically from those of local-area network systems. In a wide-area network (WAN) configuration, individual sites usually report to different system administrators, have different access and charging algorithms, install site-specific data type extensions, and have different constraints on servicing remote requests. Typical of the last point are production transaction environments, which are fully engaged during normal business hours, and cannot take on additional load. Finally, there may be many sites participating in a WAN distributed DBMS.  In this world, a single program performing global query optimization using a cost-based optimizer will not work well. Cost-based optimization does not respond well to site-specific type extension, access constraints, charging algorithms, and time-of-day constraints. Furthermore, traditional cost-based distributed optimizers do not scale well to a large number of possible processing sites. Since traditional distributed DBMSs have all used cost-based optimizers, they are not appropriate in a WAN environment, and a new architecture is required.  We have proposed and implemented an economic paradigm as the solution to these issues in a new distributed DBMS called Mariposa. In this paper, we present the architecture and implementation of Mariposa and discuss early feedback on its operating characteristics. "
"The second international workshop on semantic Web technologies for health data management aimed at putting together an interdisciplinary audience that is interested in the fields of semantic web, data management and health informatics to discuss the challenges in health-care data management and to propose new solutions for the next generation data-driven health-care systems. In this article, we summarize the outcomes of the workshop, and we present a number of key observations and research directions that emerge. "
"More and more individuals, companies and organizations are relying on the cloud to store and manage their data, which translates into increasing pressure on the cloud infrastructure. Cloud data can be very diverse, including a wide variety of personal data collections, very large multimedia content repositories and very large datasets. Users and application developers can be in very high numbers, with little DBMS expertise. Data-intensive applications can be very diverse too, with requirements ranging from basic database capabilities to complex analytics over big data. In particular, the pay-as-you-go model makes the cloud attractive for supporting novel large-scale elastic applications. "
"Central to any XML query language is a path language such as XPath which operates on the tree structure of the XML document. We demonstrate in this paper that the tree structure can be effectively compressed and manipulated using techniques derived from symbolic model checking. Specifically, we show first that succinct representations of document tree structures based on sharing subtrees are highly effective. Second, we show that compressed structures can be queried directly and efficiently through a process of manipulating selections of nodes and partial decompression. We study both the theoretical and experimental properties of this technique and provide algorithms for querying our compressed instances using node-selecting path query languages such as XPath.    We believe the ability to store and manipulate large portions of the structure of very large XML documents in main memory is crucial to the development of efficient, scalable native XML databases and query engines."
"In this paper, we present a comparison of nonparametric estimation methods for computing approximations of the selectivities of queries, in particular range queries. In contrast to previous studies, the focus of our comparison is on metric attributes with large domains which occur for example in spatial and temporal databases. We also assume that only small sample sets of the required relations are available for estimating the selectivity. In addition to the popular histogram estimators, our comparison includes so-called kernel estimation methods. Although these methods have been proven to be among the most accurate estimators known in statistics, they have not been considered for selectivity estimation of database queries, so far. We first show how to generate kernel estimators that deliver accurate approximate selectivities of queries. Thereafter, we reveal that two parameters, the number of samples and the so-called smoothing parameter, are important for the accuracy of both kernel estimators and histogram estimators. For histogram estimators, the smoothing parameter determines the number of bins (histogram classes). We first present the optimal smoothing parameter as a function of the number of samples and show how to compute approximations of the optimal parameter. Moreover, we propose a new selectivity estimator that can be viewed as an hybrid of histogram and kernel estimators. Experimental results show the performance of different estimators in practice. We found in our experiments that kernel estimators are most efficient for continuously distributed data sets, whereas for our real data sets the hybrid technique is most promising."
Update anywhere-anytime-anyway transactional replication has unstable behavior as the workload scales up: a ten-fold increase in nodes and traffic gives a thousand fold increase in deadlocks or reconciliations. Master copy replication (primary copy) schemes reduce this problem. A simple analytic model demonstrates these results. A new two-tier replication algorithm is proposed that allows mobile (disconnected) applications to propose tentative update transactions that are later applied to a master copy. Commutative update transactions avoid the instability of other replication schemes.
"QBIC (Query By Image Content) is a prototype software system for image retrieval developed at the IBM Almaden Research Center. It allows a user to query an image collection using features of image content ¨C colors, textures, shapes, locations, and layout of images and image objects. For example, a user can query for images with a green background that contain a round red object in the upper left. The queries are formed graphically a query for red objects can be specified by selecting the color red from a color wheel, a texture query can be specified by selecting from a palette of textures, a query for a shape can be specified by drawing the shape on a¡± blackboard¡±, and so on. Retrievals are based on similarity, not exact match, computed from nuHarry Road, San Jose, CA 95120"
"Anomaly detection is an important challenge for tasks such as fault diagnosis and intrusion detection in energy constrained wireless sensor networks. A key problem is how to minimise the communication overhead in the network while performing in-network computation when detecting anomalies. Our approach to this problem is based on a formulation that uses distributed, one-class quarter-sphere support vector machines to identify anomalous measurements in the data. We demonstrate using sensor data from the Great Duck Island Project that our distributed approach is energy efficient in terms of communication overhead while achieving comparable accuracy to a centralised scheme."
"The IFO data model was proposed by Abiteboul and Hull [Abiteboul 87] as a formalized semantic database model. It has been claimed by the authors that the model subsumes the Relational model [Codd 70], the Entity-Relationship model [Chen 76], the Functional Data Model [Kerschberg 76] and virtually all of the structured aspects of the Semantic Data Model [Hammer 81], the INSYDE Model [King 85], and the Extended Semantic Hierarchy Model [Brodie 84].This paper examines the IFO data model as presented in [Abiteboul 87], compares it to other models, and thus concludes that the IFO data model is actually a subset of the Semantic Data Model proposed by Hammer in [Hammer 81]. The paper also shows that the IFO data model has failed to support concepts that are essential to both the E-R model and the Semantic Data Model which are claimed to be subsumed by the IFO model.Section 2 discusses the three IFO constructs, objects, fragments, and relationships. The mapping of these constructs to constructs in the Semantic Data Model is established as an informal proof of the result that the IFO model is subsumed by the SDM.Section 3 lists constructs supported by the Entity-Relationship model [Chen 76, Teorey 86] as will as constructs supported by SDM [Hammer 81]that the IFO data model fails to support."
"Recently, several query languages have been proposed for querying information sources whose data is not constrained by a schema, or whose schema is unknown. Examples include: LOREL (for querying data combined from several heterogeneous sources), W3QS (for querying the World Wide Web); and UnQL (for querying unstructured data). The natural data model for such languages is that of a rooted, labeled graph. Their main novelty is the ability to express queries which traverse arbitrarily long paths in the graph, typically described by a regular expression. Such queries however may prove difficult to evaluate in the case when the data is distributed on severalsites, with many edges going between sites. A typical case is that of a collection of WWW sites, with links pointing freely from one site to another (even forming cycles). A naive query shipping strategy may force the query to migrate back and forth between the various sites, leading to poor performance (or even non-termination). We present a technique for query decomposition, under which the query is shipped exactly once to every site, computed locally, then the local results are shipped to the client, and assembled here into the final result. This technique is efficient, in that (a) only data which is part of the final result is shipped from the data sites to the client site, and (b) the total work done locally at all sites does not exceed that needed for computing the (unoptimized) query on a centralized version of the database. "
"This paper introduces Crescando: a scalable, distributed relational table implementation designed to perform large numbers of queries and updates with guaranteed access latency and data freshness. To this end, Crescando leverages a number of modern query processing techniques and hardware trends. Specifically, Crescando is based on parallel, collaborative scans in main memory and so-called ""query-data"" joins known from data-stream processing. While the proposed approach is not always optimal for a given workload, it provides latency and freshness guarantees for all workloads. Thus, Crescando is particularly attractive if the workload is unknown, changing, or involves many different queries. This paper describes the design, algorithms, and implementation of a Crescando storage node, and assesses its performance on modern multi-core hardware."
"In this paper, we consider the filter step of the spatial join problem, for the case where neither of the inputs are indexed. We present a new algorithm, Scalable Sweeping-Based Spatial Join (SSSJ), that achieves both efficiency on real-life data and robustness against highly skewed and worst-case data sets. The algorithm combines a method with theoretically optimal bounds on I/O transfers based on the recently proposed distribution-sweeping technique with a highly optimized implementation of internal-memory plane-sweeping. We present experimental results based on an efficient implementation of the SSSJ algorithm, and compare it to the state-ofthe-art Partition-Based Spatial-Merge (PBSM) algorithm of Patel and DeWitt."
"We consider the problem of finding association rules that make nearly optimal binary segmentations of huge categorical databases. The optimality of segmentation is defined by an objective function suitable for the user¡¯s objective. An objective function is usually defined in terms of the distribution of a given target attribute. Our goal is to find association rules that split databases into two subsets, optimizing the value of an objective function. The problem is intractable for general objective functions, because letting N be the number of records of a given database, there are 2N possible binary segmentations, and we may have to exhaustively examine all of them. However, when the objective function is convex, there are feasible algorithms for finding nearly optimal binary segmentations, and we prove that typical criteria, such as ¡°entropy (mutual information),¡± ¡°x2 (correlation) ,¡± and ¡°gini index (mean squared error) ,¡± are actually convex. We propose practical algorithms that use computational geometry techniques to handle."
"A query optimizer requires selectivity estimation of a query to choose the most efficient access plan. An effective method of selectivity estimation for the future locations of moving objects has not yet been proposed. Existing methods for spatial selectivity estimation do not accurately estimate the selectivity of a query to moving objects, because they do not consider the future locations of moving objects, which change continuously as time passes.In this paper, we propose an effective method for spatio-temporal selectivity estimation to solve this problem. We present analytical formulas which accurately calculate the selectivity of a spatio-temporal query as a function of spatio-temporal information. Extensive experimental results show that our proposed method accurately estimates the selectivity over various queries to spatio-temporal data combining real-life spatial data and synthetic temporal data. When Tiger/lines is used as real-life spatial data, the application of an existing method for spatial selectivity estimation to the estimation of the selectivity of a query to moving objects has the average error ratio from 14% to 85%, whereas our method for spatio-temporal selectivity estimation has the average error ratio from 9% to 23%."
"We present techniques for computing small space representations of massive data streams. These are inspired by traditional wavelet-based approximations that consist of specific linear projections of the underlying data. We present general ¡°sketch¡± based methods for capturing various linear projections of the data and use them to provide pointwise and rangesum estimation of data streams. These methods use small amounts of space and per-item time while streaming through the data, and provide accurate representation as our experiments with real data streams show."
"A dynamic query interface (DQI) is a database access mechanism that provides continuous real-time feedback to the user during query formulation. Previous work shows that DQIs are elegant and powerful interfaces to small databases. Unfortunately, when applied to large databases, previous DQI algorithms slow to a crawl. We present a new incremental approach to DQI algorithms and display updates that work well with large databases, both in theory and in practice."
"Recently, similarity queries on feature vectors have been widely used to perform content-based retrieval of images. To apply this technique to large databases, it is required to develop multidimensional index structures supporting nearest neighbor queries efficiently. The SS-tree had been proposed for this purpose and is known to outperform other index structures such as the R*-tree and the K-D-B-tree. One of its most important features is that it employs bounding spheres rather than bounding rectangles for the shape of regions. However, we demonstrate in this paper that bounding spheres occupy much larger volume than bounding rectangles with high-dimensional data and that this reduces search efficiency. To overcome this drawback, we propose a new index structure called the SR-tree (Sphere/Rectangle-tree) which integrates bounding spheres and bounding rectangles. A region of the SR-tree is specified by the intersection of a bounding sphere and a bounding rectangle. Incorporating bounding rectangles permits neighborhoods to be partitioned into smaller regions than the SS-tree and improves the disjointness among regions. This enhances the performance on nearest neighbor queries especially for high-dimensional and non-uniform data which can be practical in actual image/video similarity indexing. We include the performance test results the verify this advantage of the SR-tree and show that the SR-tree outperforms both the SS-tree and the R*-tree."
"Sequoia 2000 schema development is based on emerging geospatial standards to accelerate development and facilitate data exchange. This paper focuses on the metadata schema for digital satellite images. We examine how satellite metadata are defined, used, and maintained. We discuss the geospatial standards we are using, and describe a SQL prototype that is based on the Spatial Archive and Interchange Format (SAIF) standard and implemented in the Illustra object-relational database."
"Like experiments performed at a laboratory bench, the results of an e-science in silico experiment are of limited value if other scientists are not able to identify the origin, or provenance, of those results. For e-Science, we need more systematic provenance logs across a range of eScience activities and disciplines as well as a more informed understanding of the information in these provenance data. Semantic Web technology, which enables data to be linked and defined in a way for more effective discovery, integration and cooperation across computers and people, provides an appropriate solution for our current requirement. In this paper we show how we used the COHSE conceptual open hypermedia system to build a dynamically generated hypertext of web of provenance documents arising from the Grid project based on associated concepts and reasoning over the ontology."
"Many web sites contain large sets of pages generated using a common template or layout. For example, Amazon lays out the author, title, comments, etc. in the same way in all its book pages. The values used to generate the pages (e.g., the author, title,...) typically come from a database. In this paper, we study the problem of automatically extracting the database values from such template-generated web pages without any learning examples or other similar human input. We formally define a template, and propose a model that describes how values are encoded into pages using a template. We present an algorithm that takes, as input, a set of template-generated pages, deduces the unknown template used to generate the pages, and extracts, as output, the values encoded in the pages. Experimental evaluation on a large number of real input page collections indicates that our algorithm correctly extracts data in most cases."
"The present study focuses on the phenomenon of using foreign language, or a language mix in advertising messages on the Swedish consumer market. The purpose established for the research was to see ..."
"Deciding the most suitable architecture is the most crucial activity in the Data warehouse life cycle. Architecture is the key factor in setting up the abilities and the limitations of a data warehouse.This articles was conducted to (1) better understand the factors that influence the selection of data warehouse architecture and (2) the success of the various architectures. The academic and data warehousing literature and industry experts were used to identify architecture selection factors and success measures and then to create questions for a Web-based survey that was used to collect data from many companies about the respondents, their companies, their data warehouses, the architectures they use, and the success of their architectures. The study findings provide interesting and useful thing about topics of long-standing importance to the datawarehousing field. Datawarehouse, Architecture, Data Mining"
"QBI is an icon-based query processing and exploration facility for large distributed databases [3]. As opposed to other interactive query interfaces, it combines (1) a pure iconic specification, i.e., no diagrams of any form, only icon manipulation, with (2) intensional browsing or metaquery tools that assist in the formulation of complete queries without involving path specification or access to the actual data in the database.Path expressions are automatically generated by QBI and irrespective of their length, represented by a single icon, allowing for better use of the screen. It requires no special knowledge of the content of the underlying database nor understanding of the details of the database schema. Hence, QBI is domain independent and equally useful to both unsophisticated and expert users."
"Current-day crawlers retrieve content only from the publicly indexable Web, i.e., the set of Web pages reachable purely by following hypertext links, ignoring search forms and pages that require authorization or prior registration. In particular, they ignore the tremendous amount of high quality content ¡°hidden¡± behind search forms, in large searchable electronic databases. In this paper, we address the problem of designing a crawler capable of extracting content from this hidden Web. We introduce a generic operational model of a hidden Web crawler and describe how this model is realized in HiWE (Hidden Web Exposer), a prototype crawler built at Stanford. We introduce a new Layout-based Information Extraction Technique (LITE) and demonstrate its use in automatically extracting semantic information from search forms and response pages. We also present results from experiments conducted to test and validate our techniques."
"From the Publisher: Upstart software projects Napster, Gnutella, and Freenet have dominated newspaper headlines, challenging traditional approaches to content distribution with their revolutionary use of peer-to-peer file-sharing technologies. Reporters try to sort out the ramifications of seemingly ungoverned peer-to-peer networks. Lawyers, business leaders, and social commentators debate the virtues and evils of these bold new distributed systems. But what's really behind such disruptive technologies -- the breakthrough innovations that have rocked the music and media worlds? And what lies ahead? In this book, key peer-to-peer pioneers take us beyond the headlines and hype and show how the technology is changing the way we communicate and exchange information. Those working to advance peer-to-peer as a technology, a business opportunity, and an investment offer their insights into how the technology has evolved and where it's going. They explore the problems they've faced, the solutions they've discovered, the lessons they've learned, and their goals for the future of computer networking. "
"Although many query tree optimization strategies have been proposed in the literature, there still is a lack of a formal and complete representation of all possible permutations of query operations (i.e., execution plans) in a uniform manner. A graph-theoretic approach presented in the paper provides a sound mathematical basis for representing a query and searching for an execution plan. In this graph model, a node represents an operation and a directed edge between two nodes indicates the older of executing these two operations in an execution plan. Each node is associated with a weight and so is an edge. The weight is an expression containing optimization required parameters, such as relation size, tuple size, join selectivity factors. All possible execution plans are representable in this graph and each spanning tree of the graph becomes an execution plan. It is a general model which can be used in the optimizer of a DBMS for internal query representation. On the basis of this model, we devise an algorithm that finds a near optimal execution plan using only polynomial time. The algorithm is compared with a few other popular optimization methods. Experiments show that the proposed algorithm is superior to the others under most circumstances."
"This tutorial presents the primary constructs of the consensus temporal query language TSQL2 via a media planning scenario. Media planning is a series of decisions involved in the delivery of a promotional message via mass media. We will follow the planning of a particular advertising campaign. We introduce the scenario by identifying the marketing objective. The media plan involves placing commercials, and is recorded in a temporal database. The media plan must then be evaluated; we show how TSQL2 can be used to derive information from the stored data. We then give examples that illustrate storing and querying indeterminate information, comparing multiple versions of the media plan, accommodating changes to the schema, and vacuuming a temporal database of old data."
"We consider the problem of analyzing market-basket data and present several important contributions. First, we present a new algorithm for finding large itemsets which uses fewer passes over the data than classic algorithms, and yet uses fewer candidate itemsets than methods based on sampling. We investigate the idea of item reordering, which can improve the low-level efficiency of the algorithm. Second, we present a new way of generating ¡°implication rules,¡± which are normalized based on both the antecedent and the consequent and are truly implications (not simply a measure of co-occurrence), and we show how they produce more intuitive results than other methods. Finally, we show how different characteristics of real data, as opposed by synthetic data, can dramatically affect the performance of the system and the form of the results."
"The HiPAC (High Performance ACtive database system) project addresses two critical problems in time-constrained data management: the handling of timing constraints in databases, and the avoidance of wasteful polling through the use of situation-action rules that are an integral part of the database and are monitored by DBMS's condition monitor. A rich knowledge model provides the necessary primitives for definition of timing constraints, situation-action rules, and precipitating events. The execution model allows various coupling modes between transactions, situation evaluations and actions, and provides the framework for correct concurrent execution of transactions and triggered actions. Different approaches to scheduling of time-constrained tasks and transactions are explored and an architecture is being designed with special emphasis on the interaction of the time-constrained, active DBMS and the operating system. Performance models are developed to evaluate the various design alternatives."
"Internet Service Providers (ISPs) use real-time data feeds of aggregated traffic in their network to support technical as well as business decisions. A fundamental difficulty with building decision support tools based on aggregated traffic data feeds is one of data quality. Data quality problems stem from network-specific issues (irregular polling caused by UDP packet drops and delays, topological mislabelings, etc.) and make it difficult to distinguish between artifacts and actual phenomena, rendering data analysis based on such data feeds ineffective.    In principle, traditional integrity constraints and triggers may be used to enforce data quality. In practice, data cleaning is done outside the database and is ad-hoc. Unfortunately, these approaches are too rigid and limited for the subtle data quality problems arising from network data where existing problems morph with network dynamics, new problems emerge over time, and poor quality data in a local region may itself indicate an important phenomenon in the underlying network. We need a new approach - both in principle and in practice - to face data quality problems in network traffic databases.    We propose a continuous data quality monitoring approach based on probabilistic, approximate constraints (PACs). These are simple, user-specified rule templates with open parameters for tolerance and likelihood. We use statistical techniques to instantiate suitable parameter values from the data, and show how to apply them for monitoring data quality.In principle, our PAC-based approach can be applied to data quality problems in any data feed. We present PAC-Man, which is the system that manages PACs for the entire aggregate network traffic database in a large ISP, and show that it is very effective in monitoring data quality problems."
"The Relational On-Line Analytical Processing (ROLAP) is emerging as the dominant approach in data warehousing. In order to enhance query performance, the ROLAP approach relies on selecting and materializing in summary tables appropriate subsets of aggregate views which are then engaged in speeding up OLAP queries. However, a straight forward relational storage implementation of materialized ROLAP views is immensely wasteful on storage and incredibly inadequate on query performance and incremental update speed."
"The conditions of when to apply fine and coarse granularity to different kinds of transaction are well understood. However, it is not very clear how multiple job classes using different lock granularities affect each other. This study aims at exploring the impact of multigranularity locking on the performance of multiple job classes transaction processing system which is common in multiuser database system. There are two key findings in the study. Firstly, lock granularity adopted by identical job classes should not differ from each other by a factor of more than 20; otherwise, serious data contention may result. Secondly, short job class transactions are generally benefited when its level of granularity is similar to that of the long job class since this will reduce the additional lock overhead and data contention which are induced by multigranularity locking."
"Electronic commerce systems (retail, auction, etc.) are good examples of data-based systems that operate under correctness and resilience requirements of a transactional nature but go beyond conventional databases, as they are formed by the aggregation of heterogeneous, autonomous components. We introduce a framework to specify, analyze and reason about the behavior of such systems, focusing on how they are designed to make consistent progress in spite of failures. The contributions are: (a) the introduction of the Guarantee abstraction to deal with transactional applications; (b) a framework based on guarantees and protocols to specify the behaviors of systems and their components and reason about the properties of systems and their components; and (c) application of the framework to a common e-commerce scenario. The framework allows the hierarchical composition of transactional systems and their properties, as well as the proofs of these properties: we specify a system's behavior at its most abstract level, and proceed to decompose the specification mirroring the structure of the system's components, considering the role of guarantee-preserving component systems and recovery in each case. In particular we show how the lower-level properties are supported by the component systems, which we also characterize within the same framework."
"The rapid emergence of XML as a standard for data exchange over the Web has led to considerable interest in the problem of securing XML documents. In this context, query evaluation engines need to ensure that user queries only use and return XML data the user is allowed to access. These added access control checks can considerably increase query evaluation time. In this paper, we consider the problem of optimizing the secure evaluation of XML twig queries.    We focus on the simple, but useful, multi-level access control model, where a security level can be either specified at an XML element, or inherited from its parent. For this model, secure query evaluation is possible by rewriting the query to use a recursive function that computes an element's security level. Based on security information in the DTD, we devise efficient algorithms that optimally determine when the recursive check can be eliminated, and when it can be simplified to just a local check on the element's attributes, without violating the access control policy. Finally, we experimentally evaluate the performance benefits of our techniques using a variety of XML data and queries."
"Illustra's Web DataBlade module is a comprehensive toolset for creating Web-enabled database applications that dynamically retrieve and update Illustra database content. You can construct simple query front ends in a matter of minutes and powerful Web applications in just a f ew hours with the Web DataBlade module. The Illustra Web DataBlade makes it easy for you to take full advantage of the Illustra sera,er's many important features, including extensible data types, an underlying rules system, and Time Travel capabilities, all o f which make Illustra the database of choice for managing all types o f content on the Worm Wide Web. "
"We present an efficient indexing method to locate 1-dimensional subsequences within a collection of sequences, such that the subsequences match a given (query) pattern within a specified tolerance. The idea is to map each data sequences into a small set of multidimensional rectangles in feature space. Then, these rectangles can be readily indexed using traditional spatial access methods, like the R*-tree [9]. In more detail, we use a sliding window over the data sequence and extract its features; the result is a trail in feature space. We propose an efficient and effective algorithm to divide such trails into sub-trails, which are subsequently represented by their Minimum Bounding Rectangles (MBRs). We also examine queries of varying lengths, and we show how to handle each case efficiently. We implemented our method and carried out experiments on synthetic and real data (stock price movements). We compared the method to sequential scanning, which is the only obvious competitor. The results were excellent: our method accelerated the search time from 3 times up to 100 times."
"Vendors of commercial database management system face many challenges in incorporating into their products innovative technologies developed in academia. Pragmatic considerat,ions and operational requirements can limit the viability of applying promising research. Technology leadership in commercial products is often the result of taking unconventional approaches rather than following ¡°conventional wisdom¡±, as illustrated with several examples of technologies in Oracle8 and its predecessors. The challenge shared by researchers and practitioners alike: ¡°making what we do matter.¡±"
"Indexing a class hierarchy, in order to efficiently search or update the objects of a class according to a (range of) value(s) of an attribute, impacts OODB performance heavily. For this indexing problem, most systems use the class hierarchy index (CH) technique of [15] implemented using B+-trees. Other techniques, such as those of [14, 18,31], can lead to improved average-case performance but involve the implementation of new data-structures. As a special form of external dynamic two-dimensional range searching, this OODB indexing problem is solvable within reasonable worst-case bounds [12]. Based on this insight, we have developed a technique, called indexing by class-division (CD), which we believe can be used as a practical alternative to CH. We present an optimized implementation and experimental validation of CD's average-case performance. The main advantages of the CD technique are: (1) CD is an extension of CH that provides a significant speed-up over CH for a wide spectrum of range queries--this speed-up is at least linear in the number of classes queried for uniform data and larger otherwise; and (2) CD queries, updates and concurrent use are implementable using existing B+-tree technology. The basic idea of class-division involves a time-space tradeoff and CD requires some space and update overhead in comparison to CH. In practice, this overhead is a small factor (2 to 3) and, in worst-case, is bounded by the depth of the hierarchy and the logarithm of its size."
"Formation and evolution of galaxies have been a central driving force in the studies of galaxies and cosmology. Recent studies provided a global picture of cosmic star formation history. However, what drives the evolution of star formation activities in galaxies has long been a matter of debate. The key factor of the star formation is the transition of hydrogen from atomic to molecular state, since the star formation is associated with the molecular phase. This transition is also strongly coupled with chemical evolution, because dust grains, i.e., tiny solid particles of heavy elements, play a critical role in molecular formation. Therefore, a comprehensive understanding of neutral-molecular gas transition, star formation and chemical enrichment is necessary to clarify the galaxy formation and evolution."
"Queries in temporal databases often employ the coalesce operator, either to coalesce results of projections, or data which are not coalesced upon storage. Therefore, the performance and the optimisation schemes utilised for this operator is of major importance for the performance of temporal DBMSs. Insofar, performance studies for various algorithms that implement this operator have been conducted, however, the joint optimisation of the coalesce operator with other algebraic operators that appear in the query execution plan has only received minimal attention. In this paper, we propose a scheme for combining the coalesce operator with selection operators which are applied to the valid time of the tuples produced from a coalescing operation. The proposed scheme aims at reducing the number of tuples that a coalescing operator must process, while at the same time allows the optimiser to exploit temporal indices on the valid time of the data."
"Automatically selecting an appropriate set of materialized views and indexes for SQL databases is a non-trivial task. A judicious choice must be cost-driven and influenced by the workload experienced by the system. Although there has been work in materialized view selection in the context of multidimensional (OLAP) databases, no past work has looked at the problem of building an industry-strength tool for automated selection of materialized views and indexes for SQL workloads. In this paper, we present an end-to-end solution to the problem of selecting materialized views and indexes. We describe results of extensive experimental evaluation that demonstrate the effectiveness of our techniques. Our solution is implemented as part of a tuning wizard that ships with Microsoft SQL Server 2000."
"Traditional approaches to versioning documents are edit-based, and represent successive versions using edit scripts. This paper proposes a reference-based version-ing scheme that preserves the rich logical structure of the evolving document via object references. This approach produces better support for queries, and reconciles the storage-level and transport-level representations of multiversioned XML documents. In particular , we present eecient algorithms for supporting projection and selection queries, and for querying the document evolution history. Then, we show that our representation is also eecient at the transport level, where XML documents are exchanged between remote parties. In fact, with the reference-based scheme, an XML document's history can also be viewed and processed as yet another XML document. Finally, we demonstrate the eeectiveness of the new scheme at the storage level, for which we deene a usefulness-based page management policy, adapted from transaction-time databases, to ensure eecient temporal clustering between versions. The experimental evaluation of the new scheme against previous representations used in temporal databases and persistent-object managers shows the performance advantages of the new approach."
"We consider the problem of substring searching in large databases. Typical applications of this problem are genetic data, web data, and event sequences. Since the size of such databases grows exponentially, it becomes impractical to use inmemory algorithms for these problems. In this paper, we propose to map the substrings of the data into an integer space with the help of wavelet coefficients. Later, we index these coefficients using MBRs (Minimum Bounding Rectangles). We define a distance function which is a lower bound to the actual edit distance between strings. We experiment with both nearest neighbor queries and range queries. The results show that our technique prunes significant amount of the database (typically 50-95%), thus reducing both the disk I/O cost and the CPU cost significantly ."
"Data mining, or knowledge discovery in databases, has been popularly recognized as an important research issue with broad applications. We provide a comprehensive survey, in database perspective, on the data mining techniques developed recently. Several major kinds of data mining methods, including generalization, characterization, classification, clustering, association, evolution, pattern matching, data visualization, and meta-rule guided mining, will be reviewed. Techniques for mining knowledge in different kinds of databases, including relational, transaction, object-oriented, spatial, and active databases, as well as global information systems, will be examined. Potential data mining applications and some research issues will also be discussed."
"Due to the wide use of object-oriented technology in software development and the existence of many relational databases, reverse engineering of relational schemas to object-oriented schemas is gaining in interest. One of the major problems with existing approaches for this schema mapping is that they fail to take into consideration many modern relational database design alternatives (e.g., use of binary data to store multiple-valued attributes). This paper presents a schema mapping procedure that can be applied on existing relational databases without changing their schema. The procedure maps a relational schema that is at least in 2NF into an object-oriented schema by taking into consideration various types of relational database design optimizations. "
"Real-time production systems and other dynamic environments often generate tremendous (potentially infinite) amount of stream data; the volume of data is too huge to be stored on disks or scanned multiple times. Can we perform on-line, multi-dimensional analysis and data mining of such data to alert people about dramatic changes of situations and to initiate timely, high-quality responses? This is a challenging task.    In this paper, we investigate methods for on-line, multi-dimensional regression analysis of time-series stream data, with the following contributions: (1) our analysis shows that only a small number of compressed regression measures instead of the complete stream of data need to be registered for multi-dimensional linear regression analysis, (2) to facilitate on-line stream data analysis, a partially materialized data cube model, with regression as measure, and a tilt time frame as its time dimension, is proposed to minimize the amount of data to be retained in memory or stored on disks, and (3) an exception-guided drilling approach is developed for on-line, multi-dimensional exception-based regression analysis. Based on this design, algorithms are proposed for efficient analysis of time-series data streams. Our performance study compares the proposed algorithms and identifies the most memory- and time- efficient one for multi-dimensional stream data analysis."
"Welcome to SIGMOD 2000! We think you will find both the conference and the setting to be invigorating. The natural timeless beauty of British Columbia will provide a fitting counterpoint to the dynamism of our field in which large scale, high performance, and ever more intelligent database systems are being conceived and deployed. This dynamism is reflected in our (extreme) keynote presentations, tutorials, research papers, demonstrations, industrial papers, and product presentations."
"Visualizations embody design choices about data access, data transformation, visual representation, and interaction. To interpret a static visualization, a person must identify the correspondences between the visual representation and the underlying data. These correspondences become moving targets when a visualization is dynamic. Dynamics may be introduced in a visualization at any point in the analysis and visualization process. For example, the data itself may be streaming, shifting subsets may be selected, visual representations may be animated, and interaction may modify presentation. In this paper, we focus on the impact of dynamic data. We present a taxonomy and conceptual framework for understanding how data changes influence the interpretability of visual representations. Visualization techniques are organized into categories at various levels of abstraction. The salient characteristics of each category and task suitability are discussed through examples from the scientific literature and popular practices. Examining the implications of dynamically updating visualizations warrants attention because it directly impacts the interpretability (and thus utility) of visualizations. The taxonomy presented provides a reference point for further exploration of dynamic data visualization techniques."
"The Grid is an emerging infrastructure for providing coordinated and consistent access to distributed, heterogeneous computational and information storage resources amongst autonomous organizations.    Data grids are being built across the world as the next generation data handling systems for sharing access to data and storage systems within multiple administrative domains. A data grid provides logical name spaces for digital entities and storage resources to create global identifiers that are location independent. Data grid systems provide services on the logical name space for the manipulation, management, and organization of digital entities.    Databases are increasingly being used within Grid applications for data and metadata management, and several groups are now developing services for the access and integration of structured data on the Grid. The service-based approach to making data available on the Grid is being encouraged by the adoption of the Open Grid Services Architecture (OGSA), which is bringing about the integration of the Grid with Web Service technologies.    The tutorial will introduce the Grid, and examine the requirements, issues and possible solutions for integrating data into the Grid. It will take examples from current systems, in particular the SDSC Storage Resource Broker and the OGSA-Database Access and Integration project."
"As XML is emerging as the data format of the internet era, there is an substantial increase of the amount of data in XML format. To better describe such XML data structures and constraints, several XML schema languages have been proposed. In this paper, we present a comparative analysis of six noteworthy XML schema languages. "
"We propose a data model and query language that integrates an explicit modeling and querying of graphs smoothly into a standard database environment. For standard applications, some key features of object-oriented modeling are offered such as object classes organized into a hierarchy, object identity, and attributes referencing objects. Querying can be done in a familiar style with a derive statement that can be used like a select ... from ... where. On the other hand, the model allows for an explicit representation of graphs by partitioning object classes into simple classes, link classes, and path classes whose objects can be viewed as nodes, edges, and explicitly stored paths of a graph (which is the whole database instance). For querying graphs, the derive statement has an extended meaning in that it allows one to refer to subgraphs of the database graph. A powerful rewrite operation is offered for the manipulation of heterogeneous sequences of objects which often occur as a result of accessing the database graph. Additionally there are special graph operations like determining a shortest path or a subgraph and the model is extensible by such operations. Besides being attractive for standard applications, the model permits a natural representation and sophisticated querying of networks, in particular of spatially embedded networks like highways, public transport, etc. This work was supported by the ESPRIT Basic Research Project 6881 AMUSING"
Simple economic and performance arguments suggest appropriate lifetimes for main memory pages and suggest optimal page sizes. The fundamental tradeoffs are the prices and bandwidths of RAMs and dis...
"Cache FusionTM is a fundamental component of Oracle¡¯s Real Application Cluster configuration, a shared-cache clustered-database architecture that transparently extends database applications from single systems to multi-node shared-disk clusters. In classic shared-disk implementations, the disk is the medium for data sharing and data blocks are shipped between nodes through disk writes and reads under the arbitration of a distributed lock manager. Cache Fusion extends this capability of a shared-disk architecture by allowing nodes to share the contents of their volatile buffer caches through the cluster interconnect. Using Cache Fusion, data blocks are shipped directly from one node to another using interconnect messaging, eliminating the need for extra disk I/Os to facilitate data sharing. Cache Fusion thus greatly improves the performance and scalability characteristics of shared-disk clusters while continuing to preserve the availability benefits of shared-disk architectures."
"The longitudinal stability of personality is low in childhood but increases substantially into adulthood. Theoretical explanations for this trend differ in the emphasis placed on intrinsic maturation and socializing influences. To what extent does the increasing stability of personality result from the continuity and crystallization of genetically influenced individual differences, and to what extent does the increasing stability of life experiences explain increases in personality trait stability? Behavioral genetic studies, which decompose longitudinal stability into sources associated with genetic and environmental variation, can help to address this question. We aggregated effect sizes from 24 longitudinal behavioral genetic studies containing information on a total of 21,057 sibling pairs from 6 types that varied in terms of genetic relatedness and ranged in age from infancy to old age. A combination of linear and nonlinear meta-analytic regression models were used to evaluate age trends in levels of heritability and environmentality, stabilities of genetic and environmental effects, and the contributions of genetic and environmental effects to overall phenotypic stability. Both the genetic and environmental influences on personality increase in stability with age. The contribution of genetic effects to phenotypic stability is moderate in magnitude and relatively constant with age, in part because of small-to-moderate decreases in the heritability of personality over child development that offset increases in genetic stability. In contrast, the contribution of environmental effects to phenotypic stability increases from near zero in early childhood to moderate in adulthood. The life-span trend of increasing phenotypic stability, therefore, predominantly results from environmental mechanisms."
"Views as a means to describe parts of a given data collection play an important role in many database applications. In dynamic environments where data is updated, not only information provided by v..."
"Abstract. Our aim is to develop new database technologies for the approximate matching of unstructured string data using indexes. We explore the potential of the suffix tree data structure in this context. We present a new method of building suffix trees, allowing us to build trees in excess of RAM size, which has hitherto not been possible. We show that this method performs in practice as well as the O(n) method of Ukkonen [70]. Using this method we build indexes for 200 Mb of protein and 300 Mbp of DNA, whose disk-image exceeds the available RAM. We show experimentally that suffix trees can be effectively used in approximate string matching with biological data. For a range of query lengths and error bounds the suffix tree reduces the size of the unoptimised O(mn) dynamic programming calculation required in the evaluation of string similarity, and the gain from indexing increases with index size. In the indexes we built this reduction is significant, and less than 0.3% of the expected matrix is evaluated. We detail the requirements for further database and algorithmic research to support efficient use of large suffix indexes in biological applications."
"We present a system for publishing as XML data from mixed (relational+XML) proprietary storage, while supporting redundancy in storage for tuning purposes. The correspondence between public and proprietary schemas is given by a combination of LAV-and GAV-style views expressed in XQuery. XML and relational integrity constraints are also taken into consideration. Starting with client XQueries formulated against the public schema the system achieves the combined effect of rewriting-with-views, composition-with-views and query minimization under integrity constraints to obtain optimal reformulations against the proprietary schema. The paper focuses on the engineering and the experimental evaluation of the MARS system."
"Data warehouses and recording systems typically have a large continuous stream of incoming data, that must be stored in a manner suitable for future access. Access to stored records is usually based on a key. Organizing the data on disk as the data arrives using standard techniques would result in either (a) one or more I/OS to store each incoming record (to keep the data clustered by the key), which is too expensive when data arrival rates are very high, or (b) many I/OS to locate records for a particular customer (if data is stored clustered by arrival order). We study two techniques, inspired by external sorting algorithms, to store data incrementally as it arrives, simultaneously providing good performance for recording and querying. We present concurrency control and recovery schemes for both techniques. We show the benefits of our techniques both analytically and experimentally."
"Our system architecture to manage sensor data is described. Our data mining applications require past history of the sensor data. Therefore, unlike most present systems that focus on streaming data, and cache a small window of historic data, we store the entire historic data. Several interesting problems arise in these scenarios. We study two of them: (a) Given that a sensor can send data corresponding to its current configuration at any particular instant, how do we define the data that should be stored in the database? (b) Sensors try to minimize the amount of data transmitted. Also there could be data loss in the network. So the data stored will have lots of ""holes"". In this case, how can an application make sense of the stored data? In this paper, we describe our approach to solve these problems that enables an application to recreate the environment that generated the data as precisely as possible."
"Recent developments in processor, memory and radio technology have enabled wireless sensor networks which are deployed to collect useful information from an area of interest. The sensed data must be gathered and transmitted to a base station where it is further processed for end-user queries. Since the network consists of low-cost nodes with limited battery power, power efficient methods must be employed for data gathering and aggregation in order to achieve long network lifetimes.In an environment where in a round of communication each of the sensor nodes has data to send to a base station, it is important to minimize the total energy consumed by the system in a round so that the system lifetime is maximized. With the use of data fusion and aggregation techniques, while minimizing the total energy per round, if power consumption per node can be balanced as well, a near optimal data gathering and routing scheme can be achieved in terms of network lifetime.So far, besides the conventional protocol of direct transmission, two elegant protocols called LEACH and PEGASIS have been proposed to maximize the lifetime of a sensor network. In this paper, we propose two new algorithms under name PEDAP (Power Efficient Data gathering and Aggregation Protocol), which are near optimal minimum spanning tree based routing schemes, where one of them is the power-aware version of the other. Our simulation results show that our algorithms perform well both in systems where base station is far away from and where it is in the center of the field. PEDAP achieves between 4x to 20x improvement in network lifetime compared with LEACH, and about three times improvement compared with PEGASIS."
"Despite some early signs that our final FY 2002 fund balance could be considerably lower than the $142k we had originally projected for the end of FY 02 (see Tamer Ozsu's chair message in SIGMOD Record Vol. 31, No. 2), our financial situation remains sound. On June 30 at the end of FY02, our actual fund balance had risen to almost $160k, nearly $20K more than projected and $40k above the minimum fund balance required by ACM."
"Spatial joins are one of the most important operations for combining spatial objects of several relations. In this paper, spatial join processing is studied in detail for extended spatial objects in two-dimensional data space. We present an approach for spatial join processing that is based on three steps. First, a spatial join is performed on the minimum bounding rectangles of the objects returning a set of candidates. Various approaches for accelerating this step of join processing have been examined at the last year's conference [BKS 93a]. In this paper, we focus on the problem how to compute the answers from the set of candidate which is handled by the following two steps. First of all, sophisticated approximations are used to identify answers as well as to filter out false hits from the set of candidates. For this purpose, we investigate various types of conservative and progressive approximations. In the last step, the exact geometry of the remaining candidates has to be tested against the join predicate. The time required for computing spatial join predicates can essentially be reduced when objects are adequately organized in main memory. In our approach, objects are first decomposed into simple components which are exclusively organized by a main-memory resident spatial data structure. Overall, we present a complete approach of spatial join processing on complex spatial objects. The performance of the individual steps of our approach is evaluated with data sets from real cartographic applications. The results show that our approach reduces the total execution time of the spatial join by factors."
"While content-based image retrieval (CBIR) is an expanding field, and new approaches to ever more effective retrieval are frequently proposed, relatively little attention has so far been paid to the process of evaluating the effectiveness of CBIR methods. Most of the reported evaluations use standard IR evaluation methodologies, with little consideration of their statistical significance or appropriateness for CBIR, which makes it difficult to assess the precise impact of individual methods. In this paper, we present a new approach for evaluating CBIR systems which provides both efficient and statistically-sound performance evaluation. The approach is based on stratified sampling, and provides a significant improvement over existing evaluation approaches. Comprehensive experiments using our approach to evaluate a range of CBIR methods have shown that the approach reduces not only the estimation error, but also reduces the size of the test data set required to achieve specific estimation error levels."
"Conventional software systems, such as those based on the ¡°desktop metaphor,¡± are ill-equipped to manage the electronic information and events of the typical computer user. We introduce a new metaphor, Lifestreams, for dynamically organizing a user's personal workspace. Lifestreams uses a simple organizational metaphor, a time-ordered stream of documents, as an underlying storage system. Stream filters are used to organize, monitor and summarize information for the user. Combined, they provide a system that subsumes many separate desktop applications. This paper describes the Lifestreams model and our prototype system."
"A query Q is said to be effectively bounded if for all datasets D, there exists a subset DQ of D such that Q(D) = Q(DQ), and the size of DQ and time for fetching DQ are independent of the size of D. The need for studying such queries is evident, since it allows us to compute Q(D) by accessing a bounded dataset DQ, regardless of how big D is. This paper investigates effectively bounded conjunctive queries (SPC) under an access schema A, which specifies indices and cardinality constraints commonly used. We provide characterizations (sufficient and necessary conditions) for determining whether an SPC query Q is effectively bounded under A. We study several problems for deciding whether Q is bounded, and if not, for identifying a minimum set of parameters of Q to instantiate and make Q bounded. We show that these problems range from quadratic-time to NP-complete, and develop efficient (heuristic) algorithms for them. We also provide an algorithm that, given an effectively bounded SPC query Q and an access schema A, generates a query plan for evaluating Q by accessing a bounded amount of data in any (possibly big) dataset. We experimentally verify that our algorithms substantially reduce the cost of query evaluation."
"The web is highly dynamic in both the content and quantity of the information that it encompasses. In order to fully exploit its enormous potential as a global repository of information, we need to understand how its size, topology, and content are evolving. This then allows the development of new techniques for locating and retrieving information that are better able to adapt and scale to its change and growth. The web's users are highly diverse and can access the it from a variety of devices and interfaces, at different places and times, and for varying purposes. Thus, new techniques are being developed for personalising the presentation and content of web-based information depending on how it is being accessed and on the individual user's requirements and preferences. "
"A prototyped data mining system, DBLearn, has been developed, which efficiently and effectively extracts different kinds of knowledge rules from relational databases. It has the following features: high level learning interfaces, tightly integrated with commercial relational database systems, automatic refinement of concept hierarchies, efficient discovery algorithms and good performance. Substantial extensions of its knowledge discovery power towards knowledge mining in object-oriented, deductive and spatial databases are under research and development."
"The World Wide Web (WWW) is a fast growing global information resource. It contains an enormous amount of information and provides access to a variety of services. Since there is no central control and very few standards of information organization or service offering, searching for information and services is a widely recognized problem. To some degree this problem is solved by ¡°search services,¡± also known as ¡°indexers,¡± such as Lycos, AltaVista, Yahoo, and others. These sites employ search engines known as ¡°robots¡± or ¡°knowbots¡± that scan the network periodically and form text-based indices. These services are limited in certain important aspects. First, the structural information, namely, the organization of the document into parts pointing to each other, is usually lost. Second, one is limited by the kind of textual analysis provided by the ¡°search service.¡± Third, search services are incapable of navigating ¡°through¡± forms. Finally, one cannot prescribe a complex database-like search. We view the WWW as a huge database. We have designed a high-level SQL-like language called W3QL to support effective and flexible query processing, which addresses the structure and content of WWW nodes and their varied sorts of data. We have implemented a system called W3QS to execute W3QL queries. In W3QS, query results are declaratively specified and continuously maintained as views when desired. The current architecture of W3QS provides a server that enables users to pose queries as well as integrate their own data analysis tools. The system and its query language set a framework for the development of database-like tools over the WWW. A significant contribution of this article is in formalizing the WWW and query processing over it."
"With the increased emphasis on healthcare worldwide, the issue of being able to efficiently and effectively manage large amount of patient information in diverse medium becomes critical. In this work, we will demonstrate how advanced database technologies are used in RETINA, an integrated system for the screening and management of diabetic patients. RETINA captures the profile and retinal images of diabetic patients and automatically processes the retina fundus images to extract interesting features. Given the wealth of information acquired, we employ novel techniques to determine the risk profile of patients for better patient care management and to target significant subpopulations for more detailed studies. The results of such studies can be used to introduce effective preventive measures for the targeted sub-populations. "
"Testing an SQL database system by running large sets of deterministic or stochastic SQL statements is common practice in commercial database development. However, code defects often remain undetected as the query optimizer's choice of an execution plan is not only depending on the query but strongly influenced by a large number of parameters describing the database and the hardware environment. Modifying these parameters in order to steer the optimizer to select other plans is difficult since this means anticipating often complex search strategies implemented in the optimizer. In this paper we devise algorithms for counting, exhaustive generation, and uniform sampling of plans from the complete search space. Our techniques allow extensive validation of both generation of alternatives, and execution algorithms with plans other than the optimized one¡ªif two candidate plans fail to produce the same results, then either the optimizer considered an invalid plan, or the execution code is faulty. When the space of alternatives becomes too large for exhaustive testing, which can occur even with a handful of joins, uniform random sampling provides a mechanism for unbiased testing. The technique is implemented in Microsoft's SQL Server, where it is an integral part of the validation and testing process."
"A number of execution strategies for parallel evaluation of multi-join queries have been proposed in the literature; their performance was evaluated by simulation. In this paper we give a comparative performance evaluation of four execution strategies by implementing all of them on the same parallel database system, PRISMA/DB. Experiments have been done up to 80 processors. The basic strategy is to first determine an execution schedule with minimum total cost and then parallelize this schedule with one of the four execution strategies. These strategies, coming from the literature, are named: Sequential Parallel, Synchronous Execution, Segmented Right-Deep, and Full Parallel. Based on the experiments clear guidelines are given when to use which strategy."
"Decision support systems (DSS) and data warehousing workloads comprise an increasing fraction of the database market today. I/O capacity and associated processing requirements for DSS workloads are increasing at a rapid rate, doubling roughly every nine to twelve months [38]. In response to this increasing storage and computational demand, we present a computer architecture for decision support database servers that utilizes ¡°intelligent¡± disks (IDISKs). IDISKs utilize low-cost embedded general-purpose processing, main memory, and high-speed serial communication links on each disk. IDISKs are connected to each other via these serial links and high-speed crossbar switches, overcoming the I/O bus bottleneck of conventional systems. By off-loading computation from expensive desktop processors, IDISK systems may improve cost-performance. More importantly, the IDISK architecture allows the processing of the system to scale with increasing storage demand."
A platform called AnMol for supporting analytical applications over structural data of large biomolecules is described. The term "biomolecular structure" has various connotations and different representations. AnMol reduces these representations into graph structures. Each of these graphs are then stored as one or more vectors in a database. Vectors encapsulate structural features of these graphs. Structural queries like similarity and substructure are transformed into spatial constructs like distance and containment within regions. Query results are based on inexact matches. A refinement mechanism is supported for increasing accuracy of the results. Design and implementation issues of AnMol including schema structure and performance results are discussed in this paper.
"Multimedia technology, global information infrastructures and other developments allow users to access more and more information sources of various types. However, the ¡°technical¡± availability alone (by means of networks, WWW, mail systems, databases, etc.) is not sufficient for making meaningful and advanced use of all information available on-line. Therefore, the problem of effectively and efficiently accessing and querying heterogeneous and distributed data sources is an important research direction. This paper aims at classifying existing approaches which can be used to query heterogeneous data sources. We consider one of the approaches ¡ª the mediated query approach ¡ª in more detail and provide a classification framework for it as well."
"Many emerging application domains require database systems to support efficient access over highly multidimensional datasets. The current state-of-the-art technique to indexing high dimensional data is to first reduce the dimensionality of the data using Principal Component Analysis and then indexing the reduceddimensionality space using a multidimensional index structure. The above technique, referred to as global dimensionality reduction (GDR), works well when the data set is globally correlated, i.e. most of the variation in the data can be captured by a few dimensions. In practice, datasets are often not globally correlated. In such cases, reducing the data dimensionality using GDR causes significant loss of distance information resulting in a large number of false positives and hence a high query cost. Even when a global correlation does not exist, there may exist subsets of data that are locally correlated. In this paper, we propose a technique called Local Dimensionality Reduction (LDR) that tries to find local correlations in the data and performs dimensionality reduction on the locally correlated clusters of data individually. We develop an index structure that exploits the correlated clusters to efficiently support point, range and k-nearest neighbor queries over high dimensional datasets. Our experiments on synthetic as well as real-life datasets show that our technique (1) reduces the dimensionality of the data with significantly lower loss in distance information compared to GDR and (2) significantly outperforms the GDR, original space indexing and linear scan techniques in terms of the query cost for both synthetic and real-life datasets. "
"Personalization generally refers to making a Web site more responsive to the unique and individual needs of each user. We argue that for personalization to work effectively, detailed and interoperable user profiles should be globally available for authorized sites, and these profiles should dynamically reflect the changes in user interests.Creating user profiles from user click-stream data seems to be an effective way of generating detailed and dynamic user profiles. However a user profile generated in this way is available only on the computer where the user accesses his browser, and is inaccessable when the same user works on a different computer. On the other hand, the integration of Internet with telecommunication networks have made it possible for the users to connect to Web with a variety of mobile devices as well as desk tops. "
"The IBM Lotus Domino/Notes is excellent office electronic collaboration platform, and collaborative platforms, industry leading news IM solution integration with industry leading enterprises, to create a collaborative solution. This paper USES the ideas and methods of software engineering, based on Domino/Notes. First, the Domino/Notes platform architecture and composition; Then, the design by B/S and C/S combination of office automation system structure; Then, design a Domino database components, including access control list, logic and data; At last, the design structure of directory service, convenient storage, access, management and use of resources. In this paper, the research content, give full play to the advantages of the Domino/Notes platform, to improve the efficiency of software development and quality plays an important role."
"The Propel Distributed Services Platform (PDSP) is the core software product of Propel, a new Internet infrastructure software company. The PDSP product was created to enable Java developers to architect, implement, deploy, and maintain Internet applications and services much more quickly and easily than before while still providing all of the RAS (reliability, availability and scalability) that such applications require. In this presentation, we provide a brief overview of PDSP's key features, including its support for reliable and scalable data management, text indexing and searching, and persistent queuing. We also discuss its integrated Java APIs, built-in support for online-deployable data and schema changes, and system administration facilities."
"In this paper we present a novel technique for cost estimation of user-defined methods in advanced database systems. This technique is based on multi-dimensional histograms. We explain how the system collects statistics on the method that a database user defines and adds to the system. From these statistics a multi-dimensional histogram is built. Afterwards, this histrogram can be used for estimating the cost of the target method whenever this method is referenced in a query. This cost estimation is needed by the optimizer of the database system since this cost estimation needs to know the cost of a method in order to place it at its optimal position in the Query Execution Plan (QEP). We explain here how our technique works and we provide an example to better verify its functionality."
In the database framework of Kanellakis et al. [1990] it was argued that constraint query languages should take constraint databases as input and give other constraint databases that use the same type of atomic constraints as output. This closed-form requirement has been difficult to realize in constraint query languages that contain the negation symbol. This paper describes a general approach to restricting constraint query languages with negation to safe subsets that contain only programs that are evaluable in closed-form on any valid constraint database input.
"We have developed Gigascope, a stream database for network applications including traffic analysis, intrusion detection, router configuration analysis, network research, network monitoring, and performance monitoring and debugging. Gigascope is undergoing installation at many sites within the AT&T network, including at OC48 routers, for detailed monitoring. In this paper we describe our motivation for and constraints in developing Gigascope, the Gigascope architecture and query language, and performance issues. We conclude with a discussion of stream database research problems we have found in our application."
"Maintaining currency of search engine indices by exhaustive crawling is rapidly becoming impossible due to the increasing size and dynamic content of the web. Focused crawlers aim to search only the subset of the web related to a specific category, and offer a potential solution to the currency problem. The major problem in focused crawling is performing appropriate credit assignment to different documents along a crawl path, such that short-term gains are not pursued at the expense of less-obvious crawl paths that ultimately yield larger sets of valuable pages. To address this problem we present a focused crawling algorithm that builds a model for the context within which topically relevant pages occur on the web. This context model can capture typical link hierarchies within which valuable pages occur, as well as model content on documents that frequently cooccur with relevant pages. Our algorithm further leverages the existing capability of large search engines to provide partial reverse crawling capabilities. Our algorithm shows significant performance improvements in crawling efficiency over standard focused crawling."
"Since relational database management systems typically support only diadic join operators as primitive operations, a query optimizer must choose the ¡°best¡± scquence of two-way joins to achieve the N-way join of tables requested by a query. The computational complexity of this optimization process is dominated by the number of such possible sequences that must bc evaluated by the optimizer. This paper describes and measures the performance of the Starburst join enumerator, which can parameterically adjust for each query the space of join sequences that arc evaluated by the optimizer to allow or disallow (I) composite tables (i.e., tables that are themselves the result of a join) as the inner operand of a join and (2) joins between two tables having no join predicate linking them (i.e., Cartesian products). To limit the size of their optimizer¡¯s search space, most earlier systems excludcd both of these types of plans, which can exccutc significantly faster for some queries. Dy experimentally varying the parameters of the Starburst join enumerator, we have validated analytic formulas for the number of join sequcnccs under a variety of conditions, and have proven their dependence upon the ¡°shape¡± of the query. Specifically, ¡®linear¡± queries, in which tables arc connectcd by binary predicates in a straight lint, can hc optimized in polynomial time. llence the dynamic programming techniques of System R and R* can still be used to optimize linear queries of as many as 100 tables in a reasonable amount of time! A query optimizer in a relational DRMS translates non-procedural queries into a pr0cedura.l plan for execution, typically hy generating many alternative plans, estimating the execution cost of each, and choosing the plan having the lowest estimated cost. Increasing this set offeasilile plans that it evaluates improves the chances but dots not guarantee! that it will find a bcttct plan, while increasing the (compile-time) cost for it to optimize the query. A major challenge in the design of a query optimizer is to ensure that the set of feasible plans contains cflicient plans without making the :set too big to he gcncratcd practically."
"Remote data access from disparate sources across a wide-area network such as the Internet is problematic due to the unpredictable nature of the communications medium and the lack of knowledge about the load and potential delays at remote sites. Traditional, static, query processing approaches break down in this environment because they are unable to adapt in response to unexpected delays. Query scrambling has been proposed to address this problem. Scrambling modifies query execution plans on-the-fly when delays are encountered during runtime. In its original formulation, scrambling was based on simple heuristics, which although providing good performance in many cases, were also shown to be susceptible to problems resulting from bad scrambling decisions. In this paper we address these shortcomings by investigating ways to exploit query optimization technology to aid in making intelligent scrambling choices. We propose three different approaches to using query optimization for scrambling. These approaches vary, for example, in whether they optimize for total work or response-time, and whether they construct partial or complete alternative plans. Using a two-phase randomized query optimizer, a distributed query processing simulator, and a workload derived from queries of the TPCD benchmark, we evaluate these different approaches and compare their ability to cope with initial delays in accessing remote sources. The results show that cost-based scrambling can effectively hide initial delays, but that in the absence of good predictions of expected delay durations, there are fundamental tradeoffs between risk aversion and effectiveness."
"In spite of the rapid decrease in magnetic disk prices, tertiary storage (i.e., removable media in a robotic storage library) is becoming increasingly popular. The fact that so much data can be stored encourages applications that use ever more massive data sets. Application drivers include multimedia databases, data warehouses, scientific databases, and digital libraries and archives. The database research community has responded with investigations into systems integration, performance modeling, and performance optimization. Tertiary storage systems present special challenges because of their unusual performance characteristics. Access latencies can range into minutes even on unloaded systems, but transfer rates can be very high. Tertiary storage is implemented with a wide array of technologies, each with its own performance quirks. However, little detailed performance information about tertiary storage devices has been published. In this paper we present detailed measurements of several tape drives and robotic storage libraries. The tape drives we measure include the DLT 4000, DLT 7000, Ampex 310, IBM 3590, 4mm DAT, and the Sony DTF drive. This mixture of equipment includes high and low performance drives, serpentine and helical scan drives, and cartridge The detailed measurements of different aspects of tertiary storage system performance provides an understanding of the issues related to integrating tapebased tertiary storage with a DBMS."
"XKeyword provides efficient keyword proximity queries on large XML graph databases. A query is simply a list of keywords and does not require any schema or query language knowledge for its formulation. XKeyword is built on a relational database and, hence, can accommodate very large graphs. Query evaluation is optimized by using the graph's schema. In particular, XKeyword consists of two stages. In the preprocessing stage a set of keyword indices are built along with indexed path relations that describe particular patterns of paths in the graph. In the query processing stage plans are developed that use a near optimal set of path relations to efficiently locate the keyword query results. The results are presented graphically using the novel idea of interactive result graphs, which are populated on-demand according to the user's navigation and allow efficient information discovery. We provide theoretical and experimental points for the selection of the appropriate set of precomputed path relations. We also propose and experimentally evaluate algorithms to minimize the number of queries sent to the database to output the top-K results."
"The paper investigates techniques for extracting data from HTML sites through the use of automatically generated wrappers. To automate the wrapper generation and the data extraction process, the paper develops a novel technique to compare HTML pages and generate a wrapper based on their similarities and dierences. Experimental results on real-life data-intensive Web sites confirm the feasibility of the approach."
"Entity-Relationship (ER) modeling plays a major role in relational database design. The data requirements are conceptualized using an ER model and then transformed to relations. If the requirements are well understood by the designer and then if the ER model is modeled and transformed to relations, the resultant relations will be normalized. However the choice of modeling relationships between entities with appropriate degree and cardinality ratio has a very severe impact on database design. In this paper, we focus on the issues related to modeling binary relationships, ternary relationships, decomposing ternary relationships to binary equivalents and transforming the same to relations. The impact of applying higher normal forms to relations with composite keys is analyzed. We have also proposed a methodology which database designers must follow during each phase of database design."
"While a variety of lossy compression schemes have been developed for certain forms of digital data (e.g., images, audio, video), the area of lossy compression techniques for arbitrary data tables has been left relatively unexplored. Nevertheless, such techniques are clearly motivated by the everincreasing data collection rates of modern enterprises and the need for effective, guaranteed-quality approximate answers to queries over massive relational data sets. In this paper, we propose , a system that takes advantage of attribute semantics and data-mining models to perform lossy compression of massive data tables. is based on the novel idea of exploiting predictive data correlations and prescribed error tolerances for individual attributes to construct concise and accurate Classification and Regression Tree (CaRT) models for entire columns of a table. More precisely, selects a certain subset of attributes for which no values are explicitly stored in the compressed table; instead, concise CaRTs that predict these values (within the prescribed error bounds) are maintained. To restrict the huge search space and construction cost of possible CaRT predictors, employs sophisticated learning techniques and novel combinatorial optimization algorithms. Our experimentation with several real-life data sets offers convincing evidence of the effectiveness of ¡¯ s model-based approach ©\ is"
"Users of mobile computers will soon have online access to a large number of databases via wireless networks. Because of limited bandwidth, wireless communication is more expensive than wire communication. In this paper we present and analyze various static and dynamic data allocation methods. The objective is to optimize the communication cost between a mobile computer and the stationary computer that stores the online database. Analysis is performed in two cost models. One is connection (or time) based, as in cellular telephones, where the user is charged per minute of connection. The other is message based, as in packet radio networks, where the user is charged per message. Our analysis addresses both, the average case and the worst case for determining the best allocation method. "
"Evolutionary and systems biology increasingly rely on the construction of large phylogenetic trees which represent the relationships between species of interest. As the number and size of such trees increases, so does the need for efficient data storage and query capabilities. Although much attention has been focused on XML as a tree data model, phylogenetic trees differ from document-oriented applications in their size and depth, and their need for structure-based queries rather than path-based queries.This paper focuses on Crimson, a tree storage system for phylogenetic trees used to evaluate phylogenetic tree reconstruction algorithms within the context of the NSF CIPRes project."
"Workflow management systems (WFMS) that are geared for the orchestration of business processes across multiple organizations are complex distributed systems: they consist of multiple workflow engines, application servers, and communication middleware servers such as ORBs, where each of these server types can be replicated on multiple computers for scalability and availability.Finding an appropriate system configuration with guaranteed application-specific quality of service in terms of throughput, response time, and tolerable downtime is a major challenge for human system administrators. This paper presents a tool that largely automates the task of configuring a distributed WFMS. Based on a suite of mathematical models, the tool derives the necessary degrees of replication for the various server types in order to meet specified goals for performance and availability as well as ""performability"" when service is degraded due to outages of individual servers. The paper describes the configuration tool, with emphasis on how to capture the load behavior of workflows in a realistic manner. We also present extensive experiments that evaluate the accuracy of the tool's underlying models and demonstrate the practical feasibility of automating the task of configuring a distributed WFMS. The experiments use a detailed simulation which in turn has been validated through measurements with the Mentor-lite prototype system."
"This paper presents the InterPARES project, its goal, objectives and domains of inquiry, its fundamental concepts and assumptions, its methods and general outcomes. It then focuses on one of its products, the conceptual requirements for the authenticity of electronic records, and concludes with a glance at the second phase of the project."
"My purpose here at this conference is to provide a background, first for meetings like this on subjects dealing with computers, and second, for this particular meeting. My qualifications for keynoting are, I think, as good as those of anyone here: as far as this particular meeting is concerned, I am not now directly engaged in working on computers of the type that we are going to discuss; and the organization that I represent, the Bell Telephone Laboratories, is not in the business of making such computers. So I speak as a relatively innocent bystander."
"The popularity of distributed computing environments and the growth of the ¡°Information SuperHighway¡± have dramatically increased the number of data bases available for use. Unfortunately, there are significant challenges to be overcome. One particular problem is context interchange, whereby each source of information and potential receiver of that information may operate with a different context, leading to largescale semantic heterogeneity. A context is the collection of implicit assumptions about the context dejinition (i.e., meaning) and context characteristics (i.e., quality) of the information. This paper describes various forms of context challenges and examples of potential context mediation services, such as data semantics acquisition, data quality attributes, and evolving semantics and quality, that can mitigate the problem."
"At Berkeley, we are developing TelegraphCQ [1, 2], a dataflow system for processing continuous queries over data streams. TelegraphCQ is based on a novel, highly-adaptive architecture supporting dynamic query workloads in volatile data streaming environments. In this demonstration we show our current version of TelegraphCQ, which we implemented by leveraging the code base of the open source PostgreSQL database system. Although TelegraphCQ differs significantly from a traditional database system, we found that a significant portion of the PostgreSQL code was easily reusable. We also found the extensibility features of PostgreSQL very useful, particularly its rich data types and the ability to load user-developed functions. Challenges: As discussed in [1], sharing and adaptivity are our main techniques for implementing a continuous query system. Doing this in the codebase of a conventional database posed a number of challenges:"
"Small Materialized Aggregates (SMAs for short) are considered a highly flexible and versatile alternative for materialized data cubes. The basic idea is to compute many aggregate values for small to medium-sized buckets of tuples. These aggregates are then used to speed up query processing. We present the general idea and present an application of SMAs to the TPC-D benchmark. We show that application of SMAs to TPC-D Query 1 results in a speed up of two orders of magnitude. Then, we elaborate on the problem of query processing in the presence of SMAs. Last, we briefly discuss some further tuning possibilities for SMAs."
"As with relational data, XML data changes over time with the creation, modification, and deletion of XML documents. Expressing queries on time-varying (relational or XML) data is more difficult than writing queries on nontemporal data. In this paper, we present a temporal XML query language, ¦ÓXQuery, in which we add valid time support to XQuery by minimally extending the syntax and semantics of XQuery. We adopt a stratum approach which maps a ¦ÓXQuery query to a conventional XQuery. The paper focuses on how to perform this mapping, in particular, on mapping sequenced queries, which are by far the most challenging. The critical issue of supporting sequenced queries (in any query language) is time-slicing the input data while retaining period timestamping. Timestamps are distributed throughout an XML document, rather than uniformly in tuples, complicating the temporal slicing while also providing opportunities for optimization. We propose four optimizations of our initial maximally-fragmented time-slicing approach: selected node slicing, copy-based per-expression slicing, in-place per-expression slicing, and idiomatic slicing, each of which reduces the number of constant periods over which the query is evaluated. While performance tradeoffs clearly depend on the underlying XQuery engine, we argue that there are queries that favor each of the five approaches."
"The popularity of the World-Wide Web (WWW) has made it a prime vehicle for disseminating information. The relevance of database concepts to the problems of managing and querying this information has led to a signi cant body of recent research addressing these problems. Even though the underlying challenge is the one that has been traditionally addressed by the database community { how to manage large volumes of data { the novel context of the WWW forces us to signi cantly extend previous techniques. The primary goal of this survey is to classify the di erent tasks to which database concepts have been applied, and to emphasize the technical innovations that were required to do so."
"Maintaining currency of search engine indices by exhaustive crawling is rapidly becoming impossible due to the increasing size and dynamic content of the web. Focused crawlers aim to search only the subset of the web related to a specific category, and offer a potential solution to the currency problem. The major problem in focused crawling is performing appropriate credit assignment to different documents along a crawl path, such that short-term gains are not pursued at the expense of less-obvious crawl paths that ultimately yield larger sets of valuable pages. To address this problem we present a focused crawling algorithm that builds a model for the context within which topically relevant pages occur on the web. This context model can capture typical link hierarchies within which valuable pages occur, as well as model content on documents that frequently cooccur with relevant pages. Our algorithm further leverages the existing capability of large search engines to provide partial reverse crawling capabilities. Our algorithm shows significant performance improvements in crawling efficiency over standard focused crawling."
"Recent research addressed the importance of optimizing L2 cache utilization in the design of main memory indexes and proposed the so-called cache-conscious indexes such as the CSB+-tree. However, none of these indexes took account of concurrency control, which is crucial for running the real-world main memory database applications involving index updates and taking advantage of the off-the-shelf multiprocessor systems for scaling up the performance of such applications. Observing that latching index nodes for concurrency control (CC) incurs the so-called coherence cache misses on shared-memory multiprocessors thus limiting the scalability of the index performance, this paper presents an optimistic, latch-free index traversal (OLFIT) CC scheme based on a pair of consistent node read and update primitives. An experiment with various index CC implementations for the B+tree and CSB+-tree shows that the proposed scheme shows the superior scalability on the multiprocessor system as well as the performance comparable to that of the sequential execution without CC on the uniprocessor system."
"We report on the design and implementation of the Privacy Integrated Queries (PINQ) platform for privacy-preserving data analysis. PINQ provides analysts with a programming interface to unscrubbed data through a SQL-like language. At the same time, the design of PINQ's analysis language and its careful implementation provide formal guarantees of differential privacy for any and all uses of the platform. PINQ's unconditional structural guarantees require no trust placed in the expertise or diligence of the analysts, substantially broadening the scope for design and deployment of privacy-preserving data analysis, especially by non-experts."
"We have introduced a Multi-Dimensional Clustering (MDC) physical layout scheme in DB2 version 8.0 for relational tables. Multi-Dimensional Clustering is based on the definition of one or more orthogonal clustering attributes (or expressions) of a table. The table is organized physically by associating records with similar values for the dimension attributes in a cluster. Each clustering key is allocated one or more blocks of physical storage with the aim of storing the multiple records belonging to the cluster in almost contiguous fashion. Block oriented indexes are created to access these blocks. In this paper, we describe novel techniques for query processing operations that provide significant performance improvements for MDC tables. Current database systems employ a repertoire of access methods including table scans, index scans, index ANDing, and index ORing. We have extended these access methods for efficiently processing the block based MDC tables. One important concept at the core of processing MDC tables is the block oriented access technique. In addition, since MDC tables can include regular record oriented indexes, we employ novel techniques to combine block and record indexes. Block oriented processing is extended to nested loop joins and star joins as well. We show results from experiments using a star-schema database to validate our claims of performance with minimal overhead."
"The Web presents the database area with vast opportunities and commensurate challenges. Databases and the Web are organically connected at many lev els. Web sites are increasingly pow ered b y databases.Collections of linked Web pages distributed across the Internet are themselves tempting targets for a database. The emergence of XML as the lingua franc a of the Web brings some m uchneeded order and will greatly facilitate the use of database techniques to manage Web information. This paper will discuss some of the developments related to the Web from the viewpoint of database theory. As we shall see, the Web scenario requires revisiting some of the basic assumptions of the area. T o be sure, database theory remains as valid as ev er in the classical setting, and the database industry will continue to represent a multi-billion dollar target of applicability for the foreseeable future. "
"For many KDD applications, such as detecting criminal activities in E-commerce, finding the rare instances or the outliers, can be more interesting than finding the common patterns. Existing work in outlier detection regards being an outlier as a binary property. In this paper, we contend that for many scenarios, it is more meaningful to assign to each object a degree of being an outlier. This degree is called the local outlier factor (LOF) of an object. It is local in that the degree depends on how isolated the object is with respect to the surrounding neighborhood. We give a detailed formal analysis showing that LOF enjoys many desirable properties. Using real-world datasets, we demonstrate that LOF can be used to find outliers which appear to be meaningful, but can otherwise not be identified with existing approaches. Finally, a careful performance evaluation of our algorithm confirms we show that our approach of finding local outliers can be practical."
"In environments where exact synchronization between source data objects and cached copies is not achievable due to bandwidth or other resource constraints, stale (out-of-date) copies are permitted. It is desirable to minimize the overall divergence between source objects and cached copies by selectively refreshing modified objects. We call the online process of selecting which objects to refresh in order to minimize divergence best-effort synchronization. In most approaches to best-effort synchronization, the cache coordinates the process and selects objects to refresh. In this paper, we propose a best-effort synchronization scheduling policy that exploits cooperation between data sources and the cache. We also propose an implementation of our policy that incurs low communication overhead even in environments with very large numbers of sources. Our algorithm is adaptive to wide fluctuations in available resources and data update rates. Through experimental simulation over synthetic and real-world data, we demonstrate the effectiveness of our algorithm, and we quantify the significant decrease in divergence achievable with source cooperation."
"Expert Databases are environments that support the processing of rule programs against a disk resident database. They occupy a position intermediate between active and deductive databases, with respect to the level of abstraction of the underlying rule language. The operational semantics of the rule language influences the problem solving strategy, while the architecture of the processing environment determines efficiency and scalability. In this paper, we present elements of the PARADISER architecture and its kernel rule language, PARULEL. The PARADISER environment provides support for parallel and distributed evaluation of rule programs, as well as static and dynamic load balancing protocols that predictively balance a computation at runtime. This combination of features results in a scalable database rule and complex query processing architecture. We validate our claims by analyzing the performance of the system for two realistic test cases. In particular, we show how the performance of a parallel implementation of transitive closure is significantly improved by predictive dynamic load balancing."
"Due to the advances in semiconductor manufacturing, the gap between main memory and secondary storage is constantly increasing. This becomes a significant performance bottleneck for Database Management Systems, which rely on secondary storage heavily to store large datasets. Recent advances in nanotechnology have led to the invention of alternative means for persistent storage. In particular, MicroElectroMechanical Systems (MEMS) based storage technology has emerged as the leading candidate for next generation storage systems. In order to integrate MEMS-based storage into conventional computing platform, new techniques are needed for I/O scheduling and data placement.    In the context of relational data, it has been observed that access to relations needs to be enabled in both row-wise as well as in columnwise fashions. In this paper, we exploit the physical characteristics of MEMS-based storage devices to develop a data placement scheme for relational data that enables retrieval in both row-wise and column-wise manner. We demonstrate that this data layout not only improves I/O utilization, but results in better cache performance."
"We propose a new, highly scalable and efficient technique for evaluating node-selecting queries on XML trees which is based on recent advances in the theory of tree automata.    Our query processing techniques require only two linear passes over the XML data on disk, and their main memory requirements are in principle independent of the size of the data. The overall running time is O(m + n), where monly depends on the query and n is the size of the data. The query language supported is very expressive and captures exactly all node-selecting queries answerable with only a bounded amount of memory (thus, all queries that can be answered by any form of finite-state system on XML trees). Visiting each tree node only twice is optimal, and current automata-based approaches to answering path queries on XML streams, which work using one linear scan of the stream, are considerably less expressive.    These technical results - which give rise to expressive query engines that deal more efficiently with large amounts of data in secondary storage - are complemented with an experimental evaluation of our work."
"In a digital library one of the most challenging problems is finding relevant information. Information finding is the research focus of the Stanford component of the ARPA-sponsored CS-TR Project, and the work has continued as one of the main thrusts in the Stanford Integrated Digital Library project [14]. In this paper we discuss some of the emerging issues in information finding, such as text-database discovery, efficient information dissemination, and copy detection and removal. We also outline our approaches to these issues."
"Recent progress in technologies for data input have made it easier for finance and retail organizations to collect massive amounts of data and to store them on disk at a low cost. Such organizations are interested in extracting from these huge databases previously unnoticed information that inspires new marketing strategies. In this demonstration, we introduce SOAJAR, a system for mining optimized association rules from databases with numeric data as well as Boolean data. "
"Abstract. Business-to-Business (B2B) technologies pre-date the Web. They have existed for at least as long as the Internet. B2B applications were among the first to take advantage of advances in computer networking. The Electronic Data Interchange (EDI) business standard is an illustration of such an early adoption of the advances in computer networking. The ubiquity and the affordability of the Web has made it possible for the masses of businesses to automate their B2B interactions. However, several issues related to scale, content exchange, autonomy, heterogeneity, and other issues still need to be addressed. In this paper, we survey the main techniques, systems, products, and standards for B2B interactions. We propose a set of criteria for assessing the different B2B interaction techniques, standards, and products."
"DISCOVER operates on relational databases and facilitates information discovery on them by allowing its user to issue keyword queries without any knowledge of the database schema or of SQL. DISCOVER returns qualified joining networks of tuples, that is, sets of tuples that are associated because they join on their primary and foreign keys and collectively contain all the keywords of the query. DISCOVER proceeds in two steps. First the Candidate Network Generator generates all candidate networks of relations, that is, join expressions that generate the joining networks of tuples. Then the Plan Generator builds plans for the efficient evaluation of the set of candidate networks, exploiting the opportunities to reuse common subexpressions of the candidate networks.    We prove that DISCOVER finds without redundancy all relevant candidate networks, whose size can be data bound, by exploiting the structure of the schema. We prove that the selection of the optimal execution plan (way to reuse common subexpressions) is NP-complete. We provide a greedy algorithm and we show that it provides near-optimal plan execution time cost. Our experimentation also provides hints on tuning the greedy algorithm."
"In addition to satisfying data consistency requirements as in conventional database systems, concurrency control in real-time database systems must also satisfy timing constraints, such as deadlines associated with transactions. Concurrency control for a real-time database system can be studied from several different perspectives. This largely depends on how the system is specified in terms of data consistency requirements and timing constraints. The objective of this research is to investigate and propose concurrency control algorithms for real-time database systems, that not only satisfy consistency requirements but also meet transaction timing constraints as much as possible, minimizing the percentage and average lateness of deadline-missing transactions.  To fulfill the goals of this study, we conduct our research in three phases. First, we develop a model for a real-time database system and study the performance of various concurrency control protocol classes under a variety of operating conditions. Through this study, we understand the characteristics of each protocol and their impact on the performance, and ensure the validity of our real-time database system model by reconfirming the results from previous performance studies on concurrency control for real-time database systems. Second, we choose optimistic technique as the basic mechanism for our study on concurrency control for real-time database systems, and investigate its behavior in a firm-deadline environment where tardy transactions are discarded. We present a new optimistic concurrency control algorithm that outperforms previous ones over a wide range of operating conditions, and thus provides a promising candidate for the basic concurrency control mechanism for real-time database systems. Finally, we address the problem of incorporating deadline information into optimistic protocols to improve their real-time performance. We present a new priority-cognizant conflict resolution scheme that is shown to provide considerable performance improvement over priority-insensitive algorithms, and to outperform the previously proposed priority-based conflict resolution schemes over a wide operating range. In each step of our research, we report the performance evaluation results by using a detailed simulation model of real-time database system developed in the first phase.  In addition to the three phases, we investigate semantic-based concurrency control techniques for real-time database systems, in which the semantics of operations on data objects are used to increase the concurrency of transactions executing on the data objects and to meet the timing constraints imposed on the transactions. We propose an object-oriented data model for real-time database systems. We present a semantic-based concurrency control mechanism which can be implemented through the use of the concurrency control protocols for real-time database systems studied earlier along with a general-purpose method for determining compatibilities of operations."
"It is common to find graphs with millions of nodes and billions of edges in, e.g., social networks. Queries on such graphs are often prohibitively expensive. These motivate us to propose query preserving graph compression, to compress graphs relative to a class ¦« of queries of users' choice. We compute a small Gr from a graph G such that (a) for any query Q ¦¥ ¦« Q, Q(G) = Q'(Gr), where Q' ¦¥ ¦« can be efficiently computed from Q; and (b) any algorithm for computing Q(G) can be directly applied to evaluating Q' on Gr as is. That is, while we cannot lower the complexity of evaluating graph queries, we reduce data graphs while preserving the answers to all the queries in ¦«. To verify the effectiveness of this approach, (1) we develop compression strategies for two classes of queries: reachability and graph pattern queries via (bounded) simulation. We show that graphs can be efficiently compressed via a reachability equivalence relation and graph bisimulation, respectively, while reserving query answers. (2) We provide techniques for aintaining compressed graph Gr in response to changes ¦¤G to the original graph G. We show that the incremental maintenance problems are unbounded for the two lasses of queries, i.e., their costs are not a function of the size of ¦¤G and changes in Gr. Nevertheless, we develop incremental algorithms that depend only on ¦¤G and Gr, independent of G, i.e., we do not have to decompress Gr to propagate the changes. (3) Using real-life data, we experimentally verify that our compression techniques could reduce graphs in average by 95% for reachability and 57% for graph pattern matching, and that our incremental maintenance algorithms are efficient."
"Many applications today run in a multi-tier environment with browser-based clients, mid-tier (application) servers and a backend database server. Mid-tier database caching attempts to improve system throughput and scalability by offloading part of the database workload to intermediate database servers that partially replicate data from the backend server. The fact that some queries are offloaded to an intermediate server should be completely transparent to applications one of the key distinctions between caching and replication. MTCache is a prototype mid-tier database caching solution for SQL Server that achieves this transparency. It builds on SQL Server's support for materialized views, distributed queries and replication. This paper describes MTCache and reports experimental results on the TPC-W benchmark. The experiments show that a significant part of the query workload can be offloaded to cache servers, resulting in greatly improved scale-out on the read-dominated workloads of the benchmark. Replication overhead was small with an average replication delay of less than two seconds."
"Managing scientific data warehouses requires constant adaptations to cope with changes in processing algorithms, computing environments, database schemas, and usage patterns. We have faced this challenge in the RHESSI Experimental Data Center (HEDC), a datacenter for the RHESSI NASA spacecraft. In this paper we describe our experience in developing HEDC and discuss in detail the design choices made. To successfully accommodate typical adaptations encountered in scientific data management systems, HEDC (i) clearly separates generic from domain specific code in all tiers, (ii) uses a file system for the actual data in combination with a DBMS to manage the corresponding meta data, and (iii) revolves around a middle tier designed to scale if more browsing or processing power is required. These design choices are valuable contributions as they address common concerns in a wide range of scientific data management systems."
"With the spreading of the World Wide Web as a uniform and ubiquitous interface to computer applications and information, novel opportunities are offered for introducing significant changes in all organizations and their processes. This demo presents the IDEA Web Laboratory (Web Lab), a Web-based software design environment available on the Internet, which demonstrates a novel approach to the software production process on the Web."
"A very large number of data sources on environment, energy, and natural resources are available worldwide. Unfortunately, users usually face several problems when they want to search and use environmental information. In this paper, we analyze these problems. We describe a conceptual analysis of the four major tasks in the production of environmental data, from the technology point of view, and describe the organization of the data that results from these tasks. We then discuss the notion of metainformation and outline an architecture for environmental data systems that formally models metadata and addresses some of the major problems faced by users."
"VERSANT is the industry¡¯s leading object database management system (ODBMS) for developing applications in multi-user, dstribtrted environments. VERSANT ODBMS has an objectbased client-server architecture which is particularly suitable for such complex applications as telecommunications, trartsportations, and utilities network management systems. Because these applications are usually mission-critical and do not allow my dtia. base down time, one major requirement of our customers is 24x7 (24 hours a day, 7 days a week) high-availability of object databases, even in the presence of software, hardware, or network failures. While many VERSANT features, such as on-line backup and dynamic schema evohrtio~ have already supported part of this requiremen~ they do not address the failure cases. Traditional asynchronous replication (e.g., Sybase Replication Server, DEC Data Distributor, and Oracle Symmetric Replication) is not suitable for the following two reasons, Fhs~ data integrity maybe lost as a result of either delay during propagation or conflicting update requests from different replicates. Second, any failure in the local replica database or central primary database is not transparent to the applications. "
"This paper introduces techniques for reducing data dissemination costs of query subscriptions. The reduction is achieved by merging queries with overlapping, but not necessarily equal, answers. The paper formalizes the query-merging problem and introduces a general cost model for it. We prove that the problem is NP-hard and propose exhaustive algorithms and three heuristic algorithms: the Pair Merging Algorithm, the Directed Search Algorithm and the Clustering Algorithm. We develop a simulator for evaluating the different heuristics and show that the performance of our heuristics is close to optimal."
"This paper describes PREDATOR, a freely available object-relational database system that has been developed at Cornell University. A major motivation in developing PREDATOR was to create a modern code base that could act as a research vehicle for the database community. Pursuing this goal, this paper briefly describes several features of the system that should make it attractive for database research and education."
"RAID5 disk arrays provide high performance and high reliability for reasonable cost. However RAID5 suffers a performance penalty during block updates. In order to overcome this problem, the use of dynamic striping was proposed. This method buffers a number of updates, generates a new stripe composed of newly updated blocks, and then writes the new full stripe back to disks. In this paper, we examine the effect of access locality on the dynamic striping method. To further improve performance in such an environment, we introduce the dynamic clustering policy for hot blocks. Performance analysis with various access localities shows that this method has higher performance than ordinary methods. Performance is also examined for localities that change over time. The dynamic clustering of hot blocks follows locality transitions, showing that under dynamic conditions performance improves."
"Object-oriented and object-relational databases (OODB) need to be able to load the vast quantities of data that OODB users bring to them. Loading OODB data is significantly more complicated than loading relational data due to the presence of relationships, or references, in the data; the presence of these relationships means that naive loading algorithms are slow to the point of being unusable. In our previous work, we presented the late-invsort algorithm, which performed significantly better than naive algorithms on all the data sets we tested. Unfortunately , further experimentation with the late-invsort algorithm revealed that for large data sets (ones in which a critical data structure of the load algorithm does not fit in the performance of late-invsort rapidly degrades to where it, too, is unusable. In this paper we propose a new algorithm, the partitioned-list algorithm, whose performance almost matches that of late-invsort for smaller data sets but does not degrade for large data sets. W e present a performance study of an implementation within the Shore persistent object repository showing that the partitioned-list algorithm is at least an order of magnitude better than previous algorithms on large data sets. In addition, because loading gigabytes and terabytes of data can take hours, we describe how to checkpoint the partitioned-list algorithm and resume a long-running load after a system crash or other interruption"
"Databases have employed a schema-based approach to store and retrieve structured data for decades. For peer-to-peer (P2P) networks, similar approaches are just beginning to emerge. While quite a few database techniques can be re-used in this new context, a P2P data management infrastructure poses additional challenges which have to be solved before schema-based P2P networks become as common as schema-based databases. We will describe some of these challenges and discuss approaches to solve them. Our discussion will be based on the design decisions we have employed in our Edutella infrastructure, a schema-based P2P network based on RDF and RDF schemas, and will also point out additional work addressing the issues discussed."
"For some multimedia applications, it has been found that domain objects cannot be represented as feature vectors in a multidimensional space. Instead, pair-wise distances between data objects are the only input. To support content-based retrieval, one approach maps each object to a k-dimensional (k-d) point and tries to preserve the distances among the points. Then, existing spatial access index methods such as the R-trees and KD-trees can support fast searching on the resulting k-d points. However, information loss is inevitable with such an approach since the distances between data objects can only be preserved to a certain extent. Here we investigate the use of a distance-based indexing method. In particular, we apply the vantage point tree (vp-tree) method. There are two important problems for the vp-tree method that warrant further investigation, the n-nearest neighbors search and the updating mechanisms. We study an n-nearest neighbors search algorithm for the vp-tree, which is shown by experiments to scale up well with the size of the dataset and the desired number of nearest neighbors, n. Experiments also show that the searching in the vp-tree is more efficient than that for the $R^*$-tree and the M-tree. Next, we propose solutions for the update problem for the vp-tree, and show by experiments that the algorithms are efficient and effective. Finally, we investigate the problem of selecting vantage-point, propose a few alternative methods, and study their impact on the number of distance computation."
"MLPQ/GIS [4,6] is a constraint database [5] system like CCUBE [1] and DEDALE [3] but with a special emphases on spatio-temporal data. Features include data entry tools (first four icons in Fig. 1), icon-based queries such as @@@@ Intersection, @@@@ Union, @@@@ Area, @@@@ Buffer, @@@@ Max and @@@@ Min, which optimize linear objective functions, and @@@@ for Datalog queries. For example, in Fig. 1 we loaded and displayed a constraint database that represents the midwest United States and loaded two contraint relations describing the movements of two persons. The query icon opened a dialog box into which we entered the query which finds (t, i) pairs such that the two people are in the same state i at the same time t."
"There are many applications in OLAP and data analysis where we identify regions of interest. For example, in OLAP, an analysis query involving aggregate sales performance of various products in different locations and seasons could help identify interesting cells, such as cells of a data cube having an aggregate sales higher than a threshold. While a normal answer to such a quiry merely returns all interesting cells, it may be far more informative to the user if the system return summaries or descriptions of regions formed from the identified cells. The minimum Description Length (MDL) principle is a well-known strategy for finding such region descriptions."
"Wide-area database replication technologies and the availability of content delivery networks allow Web applications to be hosted and served from powerful data centers. This form of application support requires a complete Web application suite to be distributed along with the database replicas. A major advantage of this approach is that dynamic content is served from locations closer to users, leading into reduced network latency and fast response times. However, this is achieved at the expense of overheads due to (a) invalidation of cached dynamic content in the edge caches and (b) synchronization of database replicas in the data center. These have adverse effects on the freshness of delivered content. In this paper, we propose a freshness-driven adaptive dynamic content caching, which monitors the system status and adjusts caching policies to provide content freshness guarantees. The proposed technique has been intensively evaluated to validate its effectiveness. The experimental results show that the freshness-driven adaptive dynamic content caching technique consistently provides good content freshness. Furthermore, even a Web site that enables dynamic content caching can further benefit from our solution, which improves content freshness up to 7 times, especially under heavy user request traffic and long network latency conditions. Our approach also provides better scalability and significantly reduced response times up to 70% in the experiments."
"In this paper, we consider techniques for disseminating dynamic data--such as stock prices and real-time weather information--from sources to a set of repositories. We focus on the problem of maintaining coherency of dynamic data items in a network of cooperating repositories. We show that cooperation among repositories-- where each repository pushes updates of data items to other repositories--helps reduce system-wide communication and computation overheads for coherency maintenance. However, contrary to intuition, we also show that increasing the degree of cooperation beyond a certain point can, in fact, be detrimental to the goal of maintaining coherency at low communication and computational overheads. We present techniques (i) to derive the ""optimal"" degree of cooperation among repositories, (ii) to construct an efficient dissemination tree for propagating changes from sources to cooperating repositories, and (iii) to determine when to push an update from one repository to another for coherency maintenance. We evaluate the efficacy of our techniques using real-world traces of dynamically changing data items (specifically, stock prices) and show that careful dissemination of updates through a network of cooperating repositories can substantially lower the cost of coherency maintenance."
"Success of commercial query optimizers and database management systems (object-oriented or relational) depend on accurate cost estimation of various query reordering [BGI]. Estimating predicate selectivity, or the fraction of rows in a database that satisfy a selection predicate, is key to determining the optimal join order. Previous work has concentrated on estimating selectivity for numeric fields [ASW, HaSa, IoP, LNS, SAC, WVT]. With the popularity of textual data being stored in databases, it has become important to estimate selectivity accurately for alphanumeric fields. A particularly problematic predicate used against alphanumeric fields is the SQL  like  predicate [Dat]. Techniques used for estimating numeric selectivity are not suited for estimating alphanumeric selectivity.In this paper, we study for the first time the problem of estimating alphanumeric selectivity in the presence of wildcards. Based on the intuition that the model built by a data compressor on an input text encapsulates information about common substrings in the text, we develop a technique based on the suffix tree data structure to estimate alphanumeric selectivity. In a statistics generation pass over the database, we construct a compact suffix tree-based structure from the columns of the database. We then look at three families of methods that utilize this structure to estimate selectivity during query plan costing, when a query with predicates on alphanumeric attributes contains wildcards in the predicate.We evaluate our methods empirically in the context of the TPC-D benchmark. We study our methods experimentally against a variety of query patterns and identify five techniques that hold promise."
"Success of commercial query optimizers and database management systems (object-oriented or relational) depend on accurate cost estimation of various query reordering [BGI]. Estimating predicate selectivity, or the fraction of rows in a database that satisfy a selection predicate, is key to determining the optimal join order. Previous work has concentrated on estimating selectivity for numeric fields [ASW, HaSa, IoP, LNS, SAC, WVT]. With the popularity of textual data being stored in databases, it has become important to estimate selectivity accurately for alphanumeric fields. A particularly problematic predicate used against alphanumeric fields is the SQL like predicate [Dat]. Techniques used for estimating numeric selectivity are not suited for estimating alphanumeric selectivity.In this paper, we study for the first time the problem of estimating alphanumeric selectivity in the presence of wildcards. Based on the intuition that the model built by a data compressor on an input text encapsulates information about common substrings in the text, we develop a technique based on the suffix tree data structure to estimate alphanumeric selectivity. In a statistics generation pass over the database, we construct a compact suffix tree-based structure from the columns of the database. We then look at three families of methods that utilize this structure to estimate selectivity during query plan costing, when a query with predicates on alphanumeric attributes contains wildcards in the predicate.We evaluate our methods empirically in the context of the TPC-D benchmark. We study our methods experimentally against a variety of query patterns and identify five techniques that hold promise."
We visualize the world as a fully connected information space where each object communicates with all other objects without any temporal and geographical constraints. We can model this fully connected space using fine granularity processing which can be implemented using sensors technology. We regard sensors as atomic computing particles which can deployed to geographical locations for capturing and processing data of their surrounding. This report introduces a number of excellent research articles which present unique problems and their success in finding efficient solutions for them. It also peeks in to the future of ever changing information processing discipline.
"Relational databases provide the ability to store user-defined functions and predicates which can be invoked in SQL queries. When evaluation of a user-defined predicate is relatively expensive, the traditional method of evaluating predicates as early as possible is no longer a sound heuristic. There are two previous approaches for optimizing such queries. However, neither is able to guarantee the optimal plan over the desired execution space. We present efficient techniques that are able to guarantee the choice of an optimal plan over the desired execution space. The optimization algorithm with complete rank-ordering improves upon the naive optimization algorithm by exploiting the nature of the cost formulas for join methods and is polynomial in the number of  user-defined predicates (for a given number of relations.) We also  propose pruning rules that significantly reduce the cost of searching the execution space for both the naive algorithm as well as for the optimization algorithm with complete rank-ordering, without compromising optimality. We also propose a conservative local heuristic that is simpler and has low optimization overhead. Although it is not always guaranteed to find the optimal plans, it produces close to optimal plans in most cases. We discuss how, depending on application requirements, to determine the algorithm of choice. It should be emphasized that our optimization algorithms handle user-defined selections as well as user-defined join predicates uniformly. We present complexity analysis  and experimental comparison of the algorithms."
"Over the last decade, a dramatic increase has been observed in the ability of individual experimental scientists to generate and store data, which has not been matched by an equivalent development of adequate data management tools. In this paper, we present the results of our efforts to develop a Desktop Experiment Management Environment that many experimental scientists would like to have on their desk. The environment is called ZOO and is developed in collaboration with domain scientists from Soil Sciences and Biochemistry. We first describe the overall architecture of ZOO, and then focus on key features of its various components. We specifically emphasize aspects of the object-oriented database server that is at the core of the system, the experimentation manager that initiates the execution of experiments as a result of scientists¡¯ requests, and the mechanisms that the modules of the system use to communicate between them. Finally, we briefly discuss our experiences with the use of the current ZOO prototype in the context of plant-growth simulation experiments and NMR spectroscopy experiments."
"Many problems encountered when building applications of database systems involve the manipulation of models. By ""model,"" we mean a complex structure that represents a design artifact, such as a relational schema, object-oriented interface, UML model, XML DTD, web-site schema, semantic network, complex document, or software configuration. Many uses of models involve managing changes in models and transformations of data from one model into another. These uses require an explicit representation of ""mappings"" between models. We propose to make database systems easier to use for these applications by making ""model"" and ""model mapping"" first-class objects with special operations that simplify their use. We call this capability model management.In addition to making the case for model management, our main contribution is a sketch of a proposed data model. The data model consists of formal, object-oriented structures for representing models and model mappings, and of high-level algebraic operations on those structures, such as matching, differencing, merging, selection, inversion and instantiation. We focus on structure and semantics, not implementation."
"We study the problem of efficient maintenance of materialized views that may contain duplicates. This problem is particularly important when queries against such views involve aggregate functions, which need duplicates to produce correct results. Unlike most work on the view maintenance problem that is based on an algorithmic approach, our approach is algebraic and based on equational reasoning. This approach has a number of advantages: it is robust and easily extendible to new language constructs, it produces output that can be used by query optimizers, and it simplifies correctness proofs.We use a natural extension of the relational algebra operations to bags (multisets) as our basic language. We present an algorithm that propagates changes from base relations to materialized views. This algorithm is based on reasoning about equivalence of bag-valued expressions. We prove that it is correct and preserves a certain notion of minimality that ensures that no unnecessary tuples are computed. Although it is generally only a heuristic that computing changes to the view rather than recomputing the view from scratch is more efficient, we prove results saying that under normal circumstances one should expect, the change propagation algorithm to be significantly faster and more space efficient than complete recomputing of the view. We also show that our approach interacts nicely with aggregate functions, allowing their correct evaluation on views that change."
"In the 1980's, practical and applied computer science carried out extensive discussions about the problems of version and variant behavior in different contexts, the themes ""concur- rency control"" and ""development and management of tech- nical products"" were the center interests [DL 88], [Ka 90]. The latter theme lead to considerable confusion, because the terms ""version"" and ""variant"" are used differently, depend- ing on the perspective from which the changes to technical products are viewed. For instance, one perspective could be the release of a technical ¡­"
"Many problems encountered when building applications of database systems involve the manipulation of models. By ""model,"" we mean a complex structure that represents a design artifact, such as a relational schema, object-oriented interface, UML model, XML DTD, web-site schema, semantic network, complex document, or software configuration. Many uses of models involve managing changes in models and transformations of data from one model into another. These uses require an explicit representation of ""mappings"" between models. We propose to make database systems easier to use for these applications by making ""model"" and ""model mapping"" first-class objects with special operations that simplify their use. We call this capability model management.In addition to making the case for model management, our main contribution is a sketch of a proposed data model. The data model consists of formal, object-oriented structures for representing models and model mappings, and of high-level algebraic operations on those structures, such as matching, differencing, merging, selection, inversion and instantiation. We focus on structure and semantics, not implementation."
"Abstract.Most research on attribute identification in database integration has focused on integrating attributes using schema and summary information derived from the attribute values. No research has attempted to fully explore the use of attribute values to perform attribute identification. We propose an attribute identification method that employs schema and summary instance information as well as properties of attributes derived from their instances. Unlike other attribute identification methods that match only single attributes, our method matches attribute groups for integration. Because our attribute identification method fully explores data instances, it can identify corresponding attributes to be integrated even when schema information is misleading. Three experiments were performed to validate our attribute identification method. In the first experiment, the heuristic rules derived for attribute classification were evaluated on 119 attributes from nine public domain data sets. The second was a controlled experiment validating the robustness of the proposed attribute identification method by introducing erroneous data. The third experiment evaluated the proposed attribute identification method on five data sets extracted from online music stores. The results demonstrated the viability of the proposed method."
"A likely trend in the development of future CAD, CASE and office information systems will be the use of object-oriented database systems to manage their internal data stores. The entities that these applications will retrieve, such as electronic parts and their connections or customer service records, are typically large complex objects composed of many interconnected heterogeneous objects, not thousands of tuples. These applications may exhibit widely shifting usage patterns due to their interactive mode of operation. Such a class of applications would demand clustering methods that are appropriate for clustering large complex objects and that can adapt on-line to the shifting usage patterns. While most object-oriented clustering methods allow grouping of heterogeneous objects, they  are usually static and can only be changed off-line. We present one possible architecture for performing complex object reclustering in an on-line manner that is adaptive to changing usage patterns. Our architecture involves the decomposition of a clustering method into concurrently operating components that each handle one of the fundamental tasks involved in reclustering, namely statistics collection, cluster analysis, and reorganization. We present the results of an experiment performed to evaluate its behavior. These results show that the average miss rate for object accesses can be effectively reduced using a combination of rules that we have developed for deciding when cluster analyses and reorganizations should be performed."
"I first came across the AMS paper when I started getting interested in the data-streaming area, in the spring of 2001. Reading this paper was a real eye-opener for me. It was just amazing to see how simple randomization ideas and basic probabilistic tools (like the Chebyshev inequality and the Chernoff bound) can come together to provide elegant, space-efficient randomized approximation algorithms for estimation problems that, at first glance, would seem impossible to solve. The second-moment method described in the AMS paper is essentially the father of all ¡°sketch-based¡± techniques for data-stream management. Even though the idea of randomized linear projections (a.k.a., sketches) was known for some time in the domain of functional analysis (dating back to the famous Johnson-Lindenstrauss Lemma), Alon, Matias, and Szegedy were the first to exploit sketches for small-space data-stream computation, through the use of limited-independence random variates that can be constructed in small space and time. Of course, in addition to small-space sketching, the AMS paper also makes a number of other fundamental contributions in data streaming, including practical approximation algorithms for other frequency moments (e.g., the number of distinct values in a stream), as well as several inapproximability results (i.e., lower bounds) based on beautiful communication-complexity arguments."
"Each tuple in a valid-time relation includes an interval attribute T that represents the tuple's valid time. The overlap join between two valid-time relations determines all pairs of tuples with overlapping intervals. Although overlap joins are common, existing partitioning and indexing schemes are inefficient if the data includes long-lived tuples or if intervals intersect partition boundaries."
"There is mounting evidence [Man77, SchSI] that real datasets are statistically self-similar, and thus, ¡®fractal¡¯. This is an important insight since it permits a compact statistical description of spatial datasets; subsequently, as we show, it also forms the basis for the theoretical analysis of spatial access methods, without using the typical, but unrealistic, uniformity assumption. In this paper, we focus on the estimation of the number of quadtree blocks that a real, spatial dataset will require. Using the the wellknown Hausdorff fractal dimension, we derive some closed formulas which allow us to predict the number of quadtree blocks, given some few parameters. Using our formulas, it is possible to predict the space overhead and the response time of linear quadtrees/z-ordering [OM88], which are widely used in practice. In order to verify our analytical model, we performed an extensive experimental investigation using several real datasets coming from different domains. In these experiments, we found that our analytical model agrees well with our experiments as well as with older empirical observations on 2-d [Gae95b] and 3-d [ACF+94] data."
"QuickStore is a memory-mapped storage system for persistent C++, built on top of the EXODUS Storage Manager. QuickStore provides fast access to in-memory objects by allowing application programs to access objects via normal virtual memory pointers. This article presents the results of a detailed performance study using the OO7 benchmark. The study compares the performance of QuickStore with the latest implementation of the E programming language. The QuickStore and E systems exemplify the two basic approaches (hardware and software) that have been used to implement persistence in object-oriented database systems. In addition, both systems use the same underlying storage manager and compiler, allowing us to make a truly apples-to-apples comparison of the hardware and software techniques."
"We describe a tool for compressing XML data, with applications in data exchange and archiving, which usually achieves about twice the compression ratio of gzip at roughly the same speed. The compressor, called XMill, incorporates and combines existing compressors in order to apply them to heterogeneous XML data: it uses zlib, the library function for gzip, a collection of datatype specific compressors for simple data types, and, possibly, user defined compressors for application specific data types."
"In this paper, we show how compression can be integrated into a relational database system. Specifically, we describe how the storage manager, the query execution engine, and the query optimizer of a database system can be extended to deal with compressed data. Our main result is that compression can significantly improve the response time of queries if very light-weight compression techniques are used. We will present such light-weight compression techniques and give the results of running the TPC-D benchmark on a so compressed database and a non-compressed database using the AODB database system, an experimental database system that was developed at the Universities of Mannheim and Passau. Our benchmark results demonstrate that compression indeed offers high performance gains (up to 50%) for IO-intensive queries and moderate gains for CPU-intensive queries. Compression can, however, also increase the running time of certain update operations. In all, we recommend to extend today's database systems with light-weight compression techniques and to make extensive use of this feature."
"Statistics play an important role in influencing the plans produced by a query optimizer. Traditionally, optimizers use statistics built over base tables and assume independence between attributes while propagating statistical information through the query plan. This approach can introduce large estimation errors, which may result in the optimizer choosing inefficient execution plans. In this paper, we show how to extend a generic optimizer so that it also exploits statistics built on expressions corresponding to intermediate nodes of query plans. We show that in some cases, the quality of the resulting plans is significantly better than when only base-table statistics are available. Unfortunately, even moderately-sized schemas may have too many relevant candidate statistics. We introduce a workload-driven technique to identify a small subset of statistics that can provide significant benefits over just maintaining base-table statistics. Finally, we present experimental results on an implementation of our approach in Microsoft SQL Server 2000."
"Each tuple in a valid-time relation includes an interval attribute T that represents the tuple's valid time. The overlap join between two valid-time relations determines all pairs of tuples with overlapping intervals. Although overlap joins are common, existing partitioning and indexing schemes are inefficient if the data includes long-lived tuples or if intervals intersect partition boundaries."
"Oracle Symmetric Replication extends the asynchronous snapshot replication capabilities of 0racle7 to eliminate primary site or mw ownership restrictions imposed by the replication systam. Any row of any replicated table can be updated at any time by any database storing the row, Data replication configurations can be based on read-only or updatable snapshots of subsets of master tables, peer to peer replication of complete master tables, or a combination of these two configurations. Symmetic Replication is implemented as a Iayemd architecture that includes data trrmspo~ replication program generation, and distributed database administration components. The issues that Symmetric Replication raises for application design are being studied in the context of Oracle Applications products."
"QuickStore is a memory-mapped storage system for persistent C++, built on top of the EXODUS Storage Manager. QuickStore provides fast access to in-memory objects by allowing application programs to access objects via normal virtual memory pointers. This article presents the results of a detailed performance study using the OO7 benchmark. The study compares the performance of QuickStore with the latest implementation of the E programming language. The QuickStore and E systems exemplify the two basic approaches (hardware and software) that have been used to implement persistence in object-oriented database systems. In addition, both systems use the same underlying storage manager and compiler, allowing us to make a truly apples-to-apples comparison of the hardware and software techniques."
"We describe a tool for compressing XML data, with applications in data exchange and archiving, which usually achieves about twice the compression ratio of gzip at roughly the same speed. The compressor, called XMill, incorporates and combines existing compressors in order to apply them to heterogeneous XML data: it uses zlib, the library function for gzip, a collection of datatype specific compressors for simple data types, and, possibly, user defined compressors for application specific data types."
"This paper is a survey of work and issues on multidimensional search trees. We provide a classification of such methods, we describe the related algorithms, we present performance analysis efforts, and finally outline future research directions. Multi-dimensional search trees and Spatial Access Methods, in general, are designed to handle spatial objects, like points, line segments, polygons, polyhedra etc. The goal is to support spatial queries, such as nearest neighbors queries (find all cities within 10 miles from Washington D.C.), or range queries (find all the lakes on earth, within 30 and 40 degrees of latitude), and so on. The applications are numerous, including traditional database multi-attribute indexing, Geographic Information Systems and spatial database systems, and indexing multimedia databases by content. $¡®rom the spatial databases viewpoint we can dist,inguish between two major classes of access methods:"
"Statistics play an important role in influencing the plans produced by a query optimizer. Traditionally, optimizers use statistics built over base tables and assume independence between attributes while propagating statistical information through the query plan. This approach can introduce large estimation errors, which may result in the optimizer choosing inefficient execution plans. In this paper, we show how to extend a generic optimizer so that it also exploits statistics built on expressions corresponding to intermediate nodes of query plans. We show that in some cases, the quality of the resulting plans is significantly better than when only base-table statistics are available. Unfortunately, even moderately-sized schemas may have too many relevant candidate statistics. We introduce a workload-driven technique to identify a small subset of statistics that can provide significant benefits over just maintaining base-table statistics. Finally, we present experimental results on an implementation of our approach in Microsoft SQL Server 2000."
"In this paper we address the problem of devising a set of indexes for a nested object hierarchy in an object-oriented database to improve the overall system performance. It is noted that the effects of two indexes could be entangled in that the inclusion of one index might affect the benefit achievable by the other index. Such a phenomenon is termed index interaction. Clearly, the effect of index interaction needs to be taken into consideration when a set of indexes is being built. The index selection problem is first formulated and four index selection algorithms are evaluated via simulation. The effects of different objective functions, which guide the search in the index selection algorithms, are also investigated. It is shown by simulation results that the greedy algorithm which is devised in light of the phenomenon of index interaction performs fairly well in most cases. Sensitivity analysis for various database parameters is conducted. Index Terms: Object-oriented databases, indexing, nested object hierarchy, index interaction."
"Handling large collections of digitized multimedia data, usually referred to as multimedia digital libraries, is a major challenge for information technology. The Mirror DBMS is a research database system that is developed to better understand the kind of data management that is required in the context of multimedia digital libraries (see also URL http://www.cs.utwente.nl/~arjen/mmdb.html). Its main features are an integrated approach to both content management and (traditional) structured data management, and the implementation of an extensible object-oriented logical data model on a binary relational physical data model. The focus of this work is aimed at design for scalability."
"1 Aims and scope The Web is changing every aspect of our lives, but no area is undergoing as rapid and significant changes as the way businesses operate. Today, large and small companies are using the Web to communicate with their partners, to connect with their back-end systems, and to perform electronic commerce transactions. The next chapter of the Internet story is the evolution of today's e-business and e-commerce systems into ""e-services"", such as order procurement, on-line trading, customer relationship management, product promotion, or real-time car navigation and traffic information services. In order to make e-services available to customers, service providers need to address several issues, such as: ? e-service description: which are the attributes of an e-service that should be made visible to customers or applications, and how they should be described. ? e-service advertisement: how service providers can publish service description so that they can be discovered and accessed by customers and applications. ? e-service discovery and selection: how customers and applications can discover and select the e-service (or the combination of e-services) that best fulfill their requirements. ? e-service composition: how basic e-services (possibly offered by different companies) can be combined to form value-added, reliable services. Which architectures, models, and languages can achieve zero latency service integration and cross-organizational business process automation. ? e-service delivery: how e-services are delivered to businesses and to customers ? e-service monitoring and analysis: how service executions can be monitored and how service execution data can be analyzed in order to improve the service quality or efficiency ? e-service contracts: how to agree on and perform legal contracts between service providers and clients electronically. ? e-service ratings: how to validate service claims and evaluate the quality of the different service providers."
"Advanced applications in fields such as CAD, software engineering, real-time process control, corporate repositories and digital libraries require the construction, efficient access and management of large, shared knowledge bases. Such knowledge bases cannot be built using existing tools such as expert system shells, because these do not scale up, nor can they be built in terms of existing database technology, because such technology does not support the rich representational structure and inference mechanisms required for knowledge-based systems. This paper proposes a generic architecture for a knowledge base management system intended for such applications. The architecture assumes an object-oriented knowledge representation language with an assertional sublanguage used to express constraints and rules. It also provides for general-purpose deductive inference and special-purpose temporal reasoning. Results reported in the paper address several knowledge base management issues. For storage management, a new method is proposed for generating a logical schema for a given knowledge base. Query processing algorithms are offered for semantic and physical query optimization, along with an enhanced cost model for query cost estimation. On concurrency control, the paper describes a novel concurrency control policy which takes advantage of knowledge base structure and is shown to outperform two-phase locking for highly structured knowledge bases and update-intensive transactions. Finally, algorithms for compilation and efficient processing of constraints and rules during knowledge base operations are described. The paper describes original results, including novel data structures and algorithms, as well as preliminary performance evaluation data. Based on these results, we conclude that knowledge base management systems which can accommodate large knowledge bases are feasible."
"Intrusion detection is an essential component of computer security mechanisms. It requires accurate and efficient analysis of a large amount of system and network audit data. It can thus be an application area of data mining. There are several characteristics of audit data: abundant raw data, rich system and network semantics, and ever ""streaming"". Accordingly, when developing data mining approaches, we need to focus on: feature extraction and construction, customization of (general) algorithms according to semantic information, and optimization of execution efficiency of the output models. In this paper, we describe a data mining framework for mining audit data for intrusion detection models. We discuss its advantages and limitations, and outline the open research problems."
"Text data in the Internet can be partitioned into many databases naturally. Efficient retrieval of desired data can be achieved if we can accurately predict the usefulness of each database, because with such information, we only need to retrieve potentially useful documents from useful databases. In this paper, we propose two new methods for estimating the usefulness of text databases. For a given query, the usefulness of a text database in this paper is defined to be the number of documents in the database that are sufficiently similar to the query. Such a usefulness measure enables naive-users to make informed decision about which databases to search. We also consider the collection fusion problem. Because local databases may employ similarity functions that are different from that used by the global database, the threshold used by a local database to determine whether a document is potentially useful may be different from that used by the global database. We provide techniques that determine the best threshold for a given local database."
"Abstract.Due to their expressive power, regular expressions (REs) are quickly becoming an integral part of language specifications for several important application scenarios. Many of these applications have to manage huge databases of RE specifications and need to provide an effective matching mechanism that, given an input string, quickly identifies the REs in the database that match it. In this paper, we propose the RE-tree, a novel index structure for large databases of RE specifications. Given an input query string, the RE-tree speeds up the retrieval of matching REs by focusing the search and comparing the input string with only a small fraction of REs in the database. Even though the RE-tree is similar in spirit to other tree-based structures that have been proposed for indexing multidimensional data, RE indexing is significantly more challenging since REs typically represent infinite sets of strings with no well-defined notion of spatial locality. To address these new challenges, our RE-tree index structure relies on novel measures for comparing the relative sizes of infinite regular languages. We also propose innovative solutions for the various RE-tree operations including the effective splitting of RE-tree nodes and computing a ""tight"" bounding RE for a collection of REs. Finally, we demonstrate how sampling-based approximation algorithms can be used to significantly speed up the performance of RE-tree operations. Preliminary experimental results with moderately large synthetic data sets indicate that the RE-tree is effective in pruning the search space and easily outperforms naive sequential search approaches."
"speculated about the need and design of "" Information Refineries "" , machines capable of taking massive amounts of data and converting it into knowledge. In order to investigate the design of a database machine which would be capable of acting as the data storage engine of Gelemter's "" Information Refineries "" the authors initiated the MEDUSA Project as a joint undertaking between the Hardware Architecture The current MEDUSA prototype utilises a shared-nothing architecture based on the INMOS Transputer. Each of the three processing nodes used in the prototype consists of two T805 transputers with a T222 SCSI interface to a Maxtor 180 MByte disk unit as shown in figure 1. Principle Goals of the Project The principle goals of the MEDUSA Project are to develop a prototype database machine based on a shared-nothing architecture using low cost "" off the shelf "" components to SUpport research in the following areas: autonomous data management user data interfaces; backup and security systems. If the full potential of these machines is to be exploited they must exhibit a level of operational autonomy similar to the existing file server technology used on local area networks. That is, they should be capable of seamless integration into a network without requiring changes to existing software development practices or additional specialised staff to maintain their operational efficiency. Operational autonomy can be achieved by a self-organising or self-tuning database, In a self-organising database environment the database management system (DBMS) is responsible for the system tuning and data re-organisation, to achieve optimal performance. Human intervention in the system's maintenance task is reduced to no more than the changing of backup media or carrying out hardware maintenance. The traditional approach taken to performance tuning is normally heuristically bas~ with the DBMS providing the administrator with a number of tuning parameters which are adjusted based on the DBAs experience. The lack of an experienced DBA forces most sites to rely on intuition or guesswork the latter being more common. so L Interface An SQL interface, MedusaSQL, is available for data retrieval on MEDUSA. Currently, a reduced version of SQL92 standard is operational. This version allows retrieval of selected attribute values from tuples which meet criteria specified in the WHERE clause. Simple projections, joins and selections are possible using the features of the SELECT, FROM and WHERE clauses implemented thus far. Full implementation of SQL92 is planned to be completed by"
"Incremental refresh of a materialized join view is often less expensive than a full, non-incremental refresh. However, it is still a potentially costly atomic operation. This paper presents an algorithm that performs incremental view maintenance as a series of small, asynchronous steps. The size of each step can be controlled to limit contention between the refresh process and concurrent operations that access the materialized view or the underlying relations. The algorithm supports point-in-time refresh, which allows a materialized view to be refreshed to any time between the last refresh and the present."
"Active database systems can be used to establish and enforce data management policies. A large amount of the semantics that normally needs to be coded in application programs can be abstracted and assigned to active rules. This trend is sometimes called ¡°knowledge independence¡± a nice consequence of achieving full knowledge independence is that data management policies can then effectively evolve just by modifying rules instead of application programs. Active rules, however, may be quite complex to understand and manage: rules react to arbitrary event sequences, they trigger each other, and sometimes the outcome of rule processing may depend on the order in which events occur or rules are scheduled. Although reasoning on a large collection of rules is very difficult, the  task becomes more manageable when the rules are few. Therefore, we are convinced that modularization, similar to what happens in any software development process, is the key principle for designing active rules; however, this important notion has not been addressed so far. This article introduces a modularization technique for active rules called stratification; it presents a theory of stratification and indicates how stratification can be practically applied. The emphasis of this article is on providing a solution to a very concrete and practical problem; therefore, our approach is illustrated by several examples."
"When the schema of an object-oriented database system is modified, the database needs to be changed in such a way that the schema and the database remain consistent with each other. This paper describes the algorithm implemented in the new forthcoming release of the 02 object database for automatically bringing the database to a consistent state after a schema update has been performed. The algorithm, which uses a deferred strategy to update the database, is a revised and extended version of the screening algorithm first sketched in [7]."
"In this paper we propose a new framework for dynamic distributed query processing based on so-called HyperQueries which are essentially query evaluation sub-plans ¡°sitting behind¡± hyperlinks. We illustrate the flexibility of this distributed query processing architecture in the context of B2B electronic market places. Architecting an electronic market place as a data warehouse by integrating all the data fromall participating enterprises in one centralized repository incurs severe problems. Using HyperQueries, application integration is achieved via dynamic distributed query evaluation plans. The electronic market place serves as an intermediary between clients and providers executing their sub-queries referenced via hyperlinks. The hyperlinks are embedded within data objects of the intermediary¡¯s database. Retrieving such a virtual object will automatically initiate the execution of the referenced HyperQuery in order to materialize the entire object. Thus, sensitive data remains under the full control of the data providers."
"XML is an emerging standard for data representation and exchange on the World-Wide Web. Due to the nature of information on the Web and the inherent flexibility of XML, we expect that much of the data encoded in XML will be semistructured: the data may be irregular or incomplete, and its structure may change rapidly or unpredictably. This paper describes the query processor of Lore, a DBMS for XML-based data supporting an expressive query language. We focus primarily on Lore's cost-based query optimizer. While all of the usual problems associated with cost-based query optimization apply to XML-based query languages, a number of additional problems arise, such as new kinds of indexing, more complicated notions of database statistics, and vastly different query execution strategies for different databases. We define appropriate logical and physical query plans, database statistics, and a cost model, and we describe plan enumeration including heuristics for reducing the large search space. Our optimizer is fully implemented in Lore and preliminary performance results are reported. This is a short version of the paper Query Optimization for Semistructured Data which is available at: http://www-db.stanford.edu/~mchughj/publications/qo.ps"
"The multi-billion dollar market for SQL database management software is supported by ongoing national and international standardization efforts. Under the auspices of ANSI and ISO, committees of experts are actively working to add object extensions to SQL. There is no ¡­"
"The Internet of Things equips citizens with a phenomenal new means for online participation in sharing economies. When agents self-determine options from which they choose, for instance, their resource consumption and production, while these choices have a collective systemwide impact, optimal decision-making turns into a combinatorial optimization problem known as NP-hard. In such challenging computational problems, centrally managed (deep) learning systems often require personal data with implications on privacy and citizens¡¯ autonomy. This article envisions an alternative unsupervised and decentralized collective learning approach that preserves privacy, autonomy, and participation of multi-agent systems self-organized into a hierarchical tree structure. Remote interactions orchestrate a highly efficient process for decentralized collective learning. This disruptive concept is realized by I-EPOS, the Iterative Economic Planning and Optimized Selections, accompanied by a paradigmatic software artifact. Strikingly, I-EPOS outperforms related algorithms that involve non-local brute-force operations or exchange full information. This article contributes new experimental findings about the influence of network topology and planning on learning efficiency as well as findings on techno-socio-economic tradeoffs and global optimality. Experimental evaluation with real-world data from energy and bike sharing pilots demonstrates the grand potential of collective learning to design ethically and socially responsible participatory sharing economies."
"The proliferation of the Internet and intranets, advances in wireless and satellite networks, and the availability of asymmetric, high-bandwidth links to the home, have fueled the development of a wide range of new \dissemination-based"" applications. These applications involve the timely distribution of data to a large set of consumers, and include stock and sports tickers, tra c information systems, electronic personalized newspapers, and entertainment delivery. Dissemination-oriented applications have special characteristics that render traditional client-server data management approaches ine ective. These include: tremendous scale, signi cant overlap in user data needs, and asymmetric data ow from sources to consumers. The mismatch between the data access characteristics of these applications and the technology used to implement them on the WWW results in scalability problems [Fran98]. For example, WWW based applications employ the HTTP protocol which uses a request-response (or client-server), unicast method of data delivery. Using request-response, each user sends requests for data to the server. The large audience for a popular event can generate huge spikes in the load at servers, resulting in long delays and overloaded servers. Compounding the situation is that users must continually poll the server to obtain the most current data, resulting in multiple requests for the same data items from each user. In an application such as an election result server, where the interests of a large part of the population are known a priori, most of these requests are unnecessary. In order to address the needs of this new class of applications, we are developing a Dissemination-Based Information Systems (DBIS) toolkit. The toolkit serves as an adaptable middleware layer that incorporates several di erent data delivery mechanisms and provides an architecture for deploying them in a networked environment. The toolkit also includes facilities for performance monitoring, which can allow a system developer to examine the impact of using di erent data delivery mechanisms. We have implemented an initial version of this toolkit and have used it to develop a weather map dissemination application."
"Query size estimation is crucial for many database system components. In particular, query optimizers need efficient and accurate query size estimation when deciding among alternative query plans. In this paper we propose a novel sampling technique based on the golden rule of sampling, introduced by von Neumann in 1947, for estimating range queries. The proposed technique randomly samples the frequency domain using the cumulative frequency distribution and yields good estimates without any a priori knowledge of the actual underlying distribution of spatial objects. We show experimentally that the proposed sampling technique gives smaller approximation error than the Min-Skew histogram based and wavelet based approaches for both synthetic and real datasets. Moreover, the proposed technique can be easily extended for higher dimensional datasets."
"Panel Abstract This panel addresses a very important area that is often neglected or overlooked by database systems, database applications developers and data warehouse designers, namely storage. We propose to inform, discuss and debate the use of ¡°Active Storage Hierarchy¡± in database systems and applications. By active storage hierarchy we mean a database system that uses all storage media (i.e. optical, tape, and disk) to store and retrieve data and not just disk. We will examine, discuss and debate how active storage compares and/or complements what is known in the database research community as ¡°Active Disks¡± [RGF 98] and other emerging diskcentric storage paradigms. The presentations and analysis will span current real products, emerging technology to active (and visionary) research in several related areas, like storage technology, storage systems, federated databases and database system uses of storage. Panel Format ? Overview of Storage Technology, Current and Future Commercial Products. ? Overview of Database Research and Commercial Database Product Plans ? Overview and sample case studies of current and emerging applications that do and/or will in the future exploit costeffective storage hierarchy. ? Discussion and debate on feasibility and future (visionary) use of storage systems in database applications."
"The database query optimizer requires the estimation of the query selectivity to find the most efficient access plan. For queries referencing multiple attributes from the same relation, we need a multi-dimensional selectivity estimation technique when the attributes are dependent each other because the selectivity is determined by the joint data distribution of the attributes. Additionally, for multimedia databases, there are intrinsic requirements for the multi-dimensional selectivity estimation because feature vectors are stored in multi-dimensional indexing trees. In the 1-dimensional case, a histogram is practically the most preferable. In the multi-dimensional case, however, a histogram is not adequate because of high storage overhead and high error rates."
"Information spread in in databases cannot be found by current search engines. A database search engine is capable to access and advertise database on the WWW. Jungle is a database search engine prototype developed at Aalborg University. Operating through JDBC connections to remote databases, Jungle extracts and indexes database data and meta-data, building a data store of database information. This information is used to evaluate and optimize queries in the AQUA query language. AQUA is a natural and intuitive database query language that helps users to search for information without knowing how that information is structured. This paper gives an overview of AQUA and describes the implementation of Jungle."
"Providing concept level access to video data requires, video management systems tailored to the domain of the data. Effective indexing and retrieval for high-level access mandates the use of domain knowledge. This paper proposes an approach based on the use of knowledge models to building domain specific video information systems. The key issues in such systems are identified and discussed."
"The world today is characterised by the proliferation of information sources available through media such as the WWW, databases, semi-structured files (e.g. XML documents), etc. Nevertheless, this information is usually scattered, heterogeneous and weakly structured, so it is difficult to process it automatically. DENODO Corporation has developed a mediator system for the construction of semi-structured and structured data integration applications. This system has already been used in the construction of several applications on the Internet and in corporate environments, which are currently deployed at several important Internet audience sites and large sized business corporations. In this extended abstract, we present an overview of the system and we put forward some conclusions arising from our experience in building real-world data integration applications, focusing in some challenges we believe require more attention from the research community."
"XML - the eXtensible Markup Language has recently emerged as a new standard for data representation and exchange on the Interact. It is believed that it will become a universal format for data exchange on the Web and that in the near future we will find vast amounts of documents in XML format on the Web. As a result, it has become crucial to address the question of how large collections of XML documents can be sorted and retrieved efficiently and effectively.To date, most work on storing, indexing, querying, and searching documents in XML has stemmed from the database community's work on semi-structured data. An alternative approach, that has received less attention to date, is to view XML documents as a collection of text documents with additional tags and relations between these tags. IR techniques have traditionally been applied to search large sets of textual data and should thus be extended to encode the structure and semantics inherent in XML documents. Integrating IR and XML search techniques will enable more sophisticated search on the structure as well as the content of these documents, while leveraging the success of IR techniques in document similarity ranking and keyword search.The SIGIR workshop on XML and information retrieval was held July 28th, in Athens Greece. The goal of the workshop was to bring together researchers and practitioners interested in XML and IR to discuss and define the most relevant topics in the relation between these two technologies, present recent results, and propose future directions for research. The topics for discussion included:&bull; How to extend IR technologies to search XML documents&bull; How to integrate XML structure in IR indexing structures&bull; How to query XML documents both on content and structure&bull; How to introduce the semantics inherent in XML into the search process&bull; How to adopt database indexing techniques in an IR frameworkThe opening session of the workshop consisted of a survey of search engines for XML documents. This was followed by three technical sessions: query languages, retrieval algorithms, and IR systems for XML documents. The final talk of the day, ""Searching Annotated Language Resources in XML"", by Nancy Ide was given from the perspective of potential users of XML search systems and opened many topics for discussion. The workshop was concluded with a panel discussion where the panelists outlined their vision of the future of XML search."
"This paper attempts a comprehensive study of deadlock detection in distributed database systems. First, the two predominant deadlock models in these systems and the four different distributed deadlock detection approaches are discussed. Afterwards, a new deadlock detection algorithm is presented. The algorithm is based on dynamically creating deadlock detection agents (DDAs), each being responsible for detecting deadlocks in one connected component of the global wait-for-graph (WFG). The DDA scheme is a ¡°self-tuning¡± system: after an initial warm-up phase, dedicated DDAs will be formed for ¡°centers of locality¡±, i.e., parts of the system where many conflicts occur. A dynamic shift in locality of the distributed system will be responded to by automatically creating new DDAs while the obsolete ones terminate. In this paper, we also compare the most competitive representative of each class of algorithms suitable for distributed database systems based on a simulation model, and point out their relative strengths and weaknesses. The extensive experiments we carried out indicate that our newly proposed deadlock detection algorithm outperforms the other algorithms in the vast majority of configurations and workloads and, in contrast to all other algorithms, is very robust with respect to differing load and access profiles."
"Application Servers (ASs), which have become very popular in the last few years, provide the platforms for the execution of transactional, server-side applications in the online world. ASs are the modern cousins of traditional transaction processing monitors (TPMs) like CICS. In this tutorial, I will provide an introduction to different ASs and their technologies. ASs play a central role in enabling electronic commerce in the web context. They are built on the basis of more standardized protocols and APIs than were the traditional TPMs. The emergence of Java, XML and OMG standards has played a significant role in this regard. Consequently, I will also briefly introduce the related XML, Java and OMG technologies like SOAP, J2EE and CORBA. One of the most important features of ASs is their ability to integrate the modern application environments with legacy data sources like IMS, CICS, VSAM, etc. They provide a number of connectors for this purpose, typically using asynchronous transactional messaging technologies like MQSeries and JMS. Traditional TPM-style requirements for industrial strength features like scalability, availability, reliability and high performance are equally important for ASs also. Security and authentication issues are additional important requirements in the web context. ASs support DBMSs not only as storage engines for user data but also as repositories for tracking their own state. Recently, the ECPerf benchmark has been developed via the Java Community Process to evaluate in a standardized way the cost performance of J2EE-compliant ASs. Several caching technologies have been developed to improve performance of ASs.Soon after this conference is over, the slides of this tutorial will be available on the web at the following URL: http://www.almaden.ibm.com/u/mohan/AppServersTutorial_SIGMOD2002_Slides.pdf"
"Many information resources on the web are relevant primarily to limited geographical communities. For instance, web sites containing information on restaurants, theaters, and apartment rentals are relevant primarily to web users in geographical proximity to these locations. In contrast, other information resources are relevant to a broader geographical community. For instance, an on-line newspaper may be relevant to users across the United States. Unfortunately, current web search engines largely ignore the geographical scope of web resources. In this paper, we introduce techniques for automatically computing the geographical scope of web resources, based on the textual content of the resources, as well as on the geographical distribution of hyperlinks to them. We report an extensive experimental evaluation of our strategies using real web data. Finally, we describe a geographicallyaware search engine that we have built to showcase our techniques."
"In this paper, we describe some of the considerations for designing highly trafficked web sites with read-only or read mostly characteristics."
"Conventional mediators focus their attention on the contents of the sources and their relationship to the integrated views provided to the users. They do not take into account the capabilities of sources to answer queries. This may lead them to generate plans involving source queries that cannot be answered by the sources. In the TSIMMIS system, we have developed a source capability sensitive plan generation module that constructs feasible plans for user queries in the presence of limited source capabilities"
"Rule-based optimizers and optimizer generators use rules to specify query transformations. Rules act directly on query representations, which typically are based on query algebras. But most algebras complicate rule formulation, and rules over these algebras must often resort to calling to externally defined bodies of code. Code makes rules difficult to formulate, prove correct and reason about, and therefore compromises the effectiveness of rule-based systems.In this paper we present KOLA: a combinator-based algebra designed to simplify rule formulation. KOLA is not a user language, and KOLA's variable-free queries are difficult for humans to read. But KOLA is an effective internal algebra because its combinator-style makes queries manipulable and structurally revealing. As a result, rules over KOLA queries are easily expressed without the need for supplemental code. We illustrate this point, first by showing some transformations that despite their simplicity, require head and body routines when expressed over algebras that include variables. We show that these transformations are expressible without supplemental routines in KOLA. We then show complex transformations of a class of nested queries expressed over KOLA. Nested query optimization, while having been studied before, have seriously challenged the rule-based paradigm."
"Not very long ago, we discussed the creation of a new part of SQL, XML-Related Specifications (SQL/XML), in this column [1]. At the time, we referred to the work that had been done as ""infrastructure"". We are pleased to be able to say that significant progress has been made, and SQL/XML [2] is now going out for the first formal stage of processing, Final Committee Draft (FCD) ballot, in ISO/IEC JTC1.In our previous column, we described the mapping of SQL ¡´identifier¡µs to XML Names, SQL data types to XML Schema data types, and SQL values to XML values. There have been a few small corrections and enhancements in these areas, but for the most part the descriptions in our previous column are still accurate.Thc new work that we will discuss in this column comes in three parts. The first part provides a mapping from a single table, all tables in a schema, or all tables in a catalog to an XML document. The second of these parts includes the creation of an XML data type in SQL and adds functions that create values of this new type. These functions allow a user to produce XML from existing SQL data. Finally, the ""infrastructure"" work that we described in our previous article included the mapping of SQL's predefined data types to XML Schema data types. This mapping has been extended to include the mapping of domains, distinct types, row types, arrays, and multisets.The FCD ballot that we mentioned began in early April. This will allow the comments contained in the ballot responses to be discussed at the Editing Meeting in September or October of this year. We expect the Editing Meeting to recommend progression to Final Draft International Status (FDIS) ballot, which suggests that an International Standard will be published by the middle of 2003."
"With an explosion of data on the web, consistent data access to diverse data sources has become a challenging task. In this tutorial will present topics of interest to database researchers and developers building: interoperable middle-ware, gateways, distributed heterogeneous query processors, federated databases, data source wrappers, mediators, and DBMS extensions."
"Recently, several query languages have been proposed for querying information sources whose data is not constrained by a schema, or whose schema is unknown. Examples include: LOREL (for querying data combined from several heterogeneous sources), W3QS (for querying the World Wide Web); and UnQL (for querying unstructured data). The natural data model for such languages is that of a rooted, labeled graph. Their main novelty is the ability to express queries which traverse arbitrarily long paths in the graph, typically described by a regular expression. Such queries however may prove difficult to evaluate in the case when the data is distributed on severalsites, with many edges going between sites. A typical case is that of a collection of WWW sites, with links pointing freely from one site to another (even forming cycles). A naive query shipping strategy may force the query to migrate back and forth between the various sites, leading to poor performance (or even non-termination). We present a technique for query decomposition, under which the query is shipped exactly once to every site, computed locally, then the local results are shipped to the client, and assembled here into the final result. This technique is efficient, in that (a) only data which is part of the final result is shipped from the data sites to the client site, and (b) the total work done locally at all sites does not exceed that needed for computing the (unoptimized) query on a centralized version of the database. We also show that the query decomposition technique can be adapted to derive a simple view maintenance method, for two forms of updates which we introduce for the graph data model."
"The ability to store, access and disseminate large amounts of data has altered the social, educational, and governmental landscape throughout the world. The developments in technology, policy, and the economics of computing have been observed by some governments as providing a means to make government agencies more responsive to each others' as well as citizens' needs and also make government actions transparent and accountable to citizens. This panel brings together technocrats who are at the forefront of ¡­"
"Current object database management systems support user-defined conversion functions to update the database once the schema has been modified. Two main strategies are possible when implementing such database conversion functions: immediate or lasy database updates. In this paper, we concentrate our attention to the definition of implementation strategies for conversion functions implemented as lasy database updates."
"Abstract.This paper describes the basic processing model and architecture of Aurora, a new system to manage data streams for monitoring applications. Monitoring applications differ substantially from conventional business data processing. The fact that a software system must process and react to continual inputs from many sources (e.g., sensors) rather than from human operators requires one to rethink the fundamental architecture of a DBMS for this application area. In this paper, we present Aurora, a new DBMS currently under construction at Brandeis University, Brown University, and M.I.T. We first provide an overview of the basic Aurora model and architecture and then describe in detail a stream-oriented set of operators."
"Information integration provides a competitive advantage to businesses and is fundamental to on demand computing. It is strategic area of investment by software companies today whose goal is to provide a unified view of the data regardless of differences in data format, data location and access interfaces, dynamically manage data placement to match availability, currency and performance requirements, and provide autonomic features that reduce the burden on IT staffs for managing complex data architectures. This paper describes the motivation for integrating information for on demand computing, explains its requirements, and illustrates its value through usage scenarios. As shown in the paper, there is still a tremendous amount of research, engineering, and development work needed to make the full information integration vision a reality and it is expected that software companies will continue to heavily invest in aggressively pursing the information integration vision."
"Many problems encountered when building applications of database systems involve the manipulation of models. By ""model,"" we mean a complex structure that represents a design artifact, such as a relational schema, object-oriented interface, UML model, XML DTD, web-site schema, semantic network, complex document, or software configuration. Many uses of models involve managing changes in models and transformations of data from one model into another. These uses require an explicit representation of ""mappings"" between models. We propose to make database systems easier to use for these applications by making ""model"" and ""model mapping"" first-class objects with special operations that simplify their use. We call this capability model management.In addition to making the case for model management, our main contribution is a sketch of a proposed data model. The data model consists of formal, object-oriented structures for representing models and model mappings, and of high-level algebraic operations on those structures, such as matching, differencing, merging, selection, inversion and instantiation. We focus on structure and semantics, not implementation."
"The gains of parallel query execution can be limited because of high start-up time, interference between execution entities, and poor load balancing. In this paper, we present a solution which reduces these limitations in DBS3, a shared-memory parallel database system. This solution combines static data partitioning and dynamic processor allocation to adapt to the execution context. It makes DBS3 almost insensitive to data skew and allows decoupling the degree of parallelism from the degree of data partitioning. To address the problem of load balancing in the presence of data skew, we analyze three important factors that influence the behavior of our parallel execution model: skew factor, degree of parallelism and degree of partitioning. We report on experiments varying these three parameters with the DBS3 prototype on a 72-node KSR1 multiprocessor. The results demonstrate high performance gains, even with highly skewed data."
"Traditional query processors generate full, accurate query results, either in batch or in pipelined fashion. We argue that this strict model is too rigid for exploratory queries over diverse and distributed data sources, such as sources on the Internet. Instead, we propose a looser model of querying in which a user submits a broad initial query outline, and the system continually generates partial result tuples that may contain values for only some of the output fields. The user can watch these partial results accumulate at the user interface, and accordingly refine the query by specifying their interest in different kinds of partial results.After describing our querying model and user interface, we present a query processing architecture for this model which is implemented in the Telegraph dataflow system. Our architecture is designed to generate partial results quickly, and to adapt query execution to changing user interests. The crux of this architecture is a dataflow operator that supports two kinds of reorderings: reordering of intermediate tuples within a dataflow, and reordering of query plan operators through which tuples flow. We study reordering policies that optimize for the quality of partial results delivered over time, and experimentally demonstrate the benefits of our architecture in this context."
"In the context of object databases, we study the application of an update method to a collection of receivers rather than to a single one.  The obvious strategy of applying the update to the receivers one after the other, in some arbitrary order, brings up the problem of order independence.  On a very general level, we investigate how update behavior can be analyzed in terms of certain schema annotations, called colorings.  We are able to characterize those colorings that always describe order-independedent updates.  We also consider a more specific model of update methods implemented in the relational algebra.  Order-independence of such algebraic methods is undecidable in general, but decidable if the expressions used are positive.  Finally, we consider an alternative parallel strategy  for set-oriented applications of algebraic update methods and compare and relate it to the sequential strategy."
"We propose a novel data model and its language for querying object-oriented databases where objects may hold spatial, temporal or constraint data, conceptually represented by linear equality and inequality constraints. The proposed LyriC language is designed to provide a uniform and flexible framework for diverse application realms such as (1) constraint-based design in two-, three-, or higher-dimensional space, (2) large-scale optimization and analysis, based mostly on linear programming techniques, and (3) spatial and geographic databases. LyriC extends flat constraint query languages, especially those for linear constraint databases, to structurally complex objects. The extension is based on the object-oriented paradigm, where constraints are treated as first-class objects that are organized in classes. The query language is an extension of the language XSQL, and is built around the idea of extended path expressions. Path expressions in a query traverse nested structures in one sweep. Constraints are used in a query to filter stored constraints and to create new constraint objects."
"Access control models, such as the ones supported by commercial DBMSs,  are not yet able to fully meet many application needs. An important requirement derives from the temporal dimension that permissions have in many real-world situations. Permissions are often limited in time or may hold only for specific periods of time. In this article, we present an access control model in which periodic temporal intervals are associated with authorizations. An authorization is automatically granted in the specified intervals and revoked when such intervals expire. Deductive temporal rules with periodicity and order constraints are provided to derive new authorizations based on the presence or absence of other authorizations in specific periods of time. We provide a solution to the problem of  ensuring the uniqueness of the global set of valid authorizations derivable at each instant, and we propose an algorithm to compute this set. Moreover, we address issues related to the efficiency of access control by adopting a materialization approach. The resulting model provides a high degree of flexibility and supports the specification of several protection requirements that cannot be expressed in traditional access control models."
"The similarity join is an important database primitive which has been successfully applied to speed up applications such as similarity search, data analysis and data mining. The similarity join combines two point sets of a multidimensional vector space such that the result contains all point pairs where the distance does not exceed a parameter ¦Å. In this paper, we propose the Epsilon Grid Order, a new algorithm for determining the similarity join of very large data sets. Our solution is based on a particular sort order of the data points, which is obtained by laying an equi-distant grid with cell length ¦Å over the data space and comparing the grid cells lexicographically. A typical problem of grid-based approaches such as MSJ or the ¦Å-kdB-tree is that large portions of the data sets must be held simultaneously in main memory. Therefore, these approaches do not scale to large data sets. Our technique avoids this problem by an external sorting algorithm and a particular scheduling strategy during the join phase. In the experimental evaluation, a substantial improvement over competitive techniques is shown."
"This paper describes the version and workspace features of Microsoft Repository, a layer that implements fine-grained objects and relationships on top of Microsoft SQL Server. It supports branching and merging of versions, delta storage, checkout-checkin, and single-version views for version-unaware applications."
"We believe that the greatest growth potential for soft real-time databases is not as isolated monolithic databases but as components in open systems consisting of many heterogenous databases. In such environments, the flexibility to deal with unpredictable situations and the ability to cooperate with other databases (often non-real-time databases) is just as important as the guarantee of stringent timing constraints. In this paper, we describe a database designed explicitly for heterogeneous environments, the STanford Real-time Information Processor (STRIP). STRIP, which runs on standard Posix Unix, is a soft real-time main memory database with special facilities for importing and exporting data as well as handling derived data. We will describe the architecture of STRIP, its unique features, and its potential uses in overall system architectures."
"Most database management systems available today are systems designed for general use. Certainly, some compromises have been done to satisfy the the most common users and the largest markets. One application which has been mostly ignored until now is the network ¡­"
"The Cubetree Storage Organization (CSO)1 logically and physically clusters materialized-views data, multi-dimensional indices on them, and computed aggregate values all in one compact and tight storage structure that uses a fraction of the conventional table-based space. This is a breakthrough technology for storing and accessing multi-dimensional data in terms of storage reduction, query performance and incremental bulk update speed. CSO has been extended with an Active MultiSync controller for synchronizing multiple concurrent access and continuous asynchronous online updates for a non-stop data warehouse."
"At the heart of many data-intensive applications is the problem of quickly and accurately transforming data into a new form. Database researchers have long advocated the use of declarative queries for this process. Yet tools for creating, managing and understanding the complex queries necessary for data transformation are still too primitive to permit widespread adoption of this approach. We present a new framework that uses data examples as the basis for understanding and refining declarative schema mappings. We identify a small set of intuitive operators for manipulating examples. These operators permit a user to follow and refine an example by walking through a data source. We show that our operators are powerful enough both to identify a large class of schema mappings and to distinguish effectively between alternative schema mappings. These operators permit a user to quickly and intuitively build and refine complex data transformation queries that map one data source into another."
The demanding performance objectives that real-time database systems (RTDBS) face necessitate the use of priority resource scheduling. This paper introduces a Priority Memory Management (PMM) algorithm that is designed to schedule queries in RTDBS. PMM attempts to minimize the number of missed deadlines by adapting both its multiprogramming level and its memory allocation strategy to the characteristics of the offered workload. A series of simulation experiments confirms that PMM's admission control and memory allocation mechanisms are very effective for real-time query scheduling.
"Web services are increasingly gaining acceptance as a framework for facilitating application-to-application interactions within and across enterprises. It is commonly accepted that a service description should include not only the interface, but also the business protocol supported by the service. The present work focuses on the formalization of an important category of protocols that includes time-related constraints (called timed protocols), and the impact of time on compatibility and replaceability analysis. We formalized the following timing constraints: C-Invoke constraints define time windows within which a service operation can be invoked while M-Invoke constraints define expiration deadlines. We extended techniques for compatibility and replaceability analysis between timed protocols by using a semantic-preserving mapping between timed protocols and timed automata, leading to the identification of a novel class of timed automata, called protocol timed automata (PTA). PTA exhibit a particular kind of silent transition that strictly increase the expressiveness of the model, yet they are closed under complementation, making every type of compatibility or replaceability analysis decidable. Finally, we implemented our approach in the context of a larger project called ServiceMosaic, a model-driven framework for Web service life-cycle management."
"The clustering problem is well known in the database literature for its numerous applications in problems such as customer segmentation, classification and trend analysis. Unfortunately, all known algorithms tend to break down in high dimensional spaces because of the inherent sparsity of the points. In such high dimensional spaces not all dimensions may be relevant to a given cluster. One way of handling this is to pick the closely correlated dimensions and find clusters in the corresponding subspace. Traditional feature selection algorithms attempt to achieve this. The weakness of this approach is that in typical high dimensional data mining applications different sets of points may cluster better for different subsets of dimensions. The number of dimensions in each such cluster-specific subspace may also vary. Hence, it may be impossible to find a single small subset of dimensions for all the clusters. We therefore discuss a generalization of the clustering problem, referred to as the projected clustering problem, in which the subsets of dimensions selected are specific to the clusters themselves. We develop an algorithmic framework for solving the projected clustering problem, and test its performance on synthetic data."
"Spatial indexing has been one of the active focus areas in recent database research. Several variants of Quadtree and R-tree indexes have been proposed in database literature. In this paper, we first describe briefly our implementation of Quadtree and R-tree index structures and related optimizations in Oracle Spatial. We then examine the relative merits of two structures as implemented in Oracle Spatial and compare their performance for different types of queries and other operations. Finally, we summarize experiences with these different structures in indexing large GIS datasets in Oracle Spatial."
"Amongst the wide range of parking solutions that can contribute to reduce parking problems or regulate parking activities, e Parking looks at developing and applying an innovative e-business application for parking space optimization. The purpose of this paper is to present the innovative e-business platform that has been deve loped, from a technical point of view, by the University of Zurich. The ideas are coming from a transcross European consortium within the framework of the IST Information Society Technologies of the 5th framework program. E-Parking provides a database-centered Web application solution based on our proposed conceptual model CIA (Channel, Integration, Application) for Web applications. The WAP, WEB and Bluetooth communication channels enable drivers to obtain early information on available parking space, make a reservation, access the reserved place and pay for the service booked. In reaching this goal, the innovative solutions seek to benefit all social segments, to optimize existing parking resources, and to contribute to achieving a more sustainable urban transport, reducing congestion and pollution.t"
"Business-oriented workflows have been studied since the 70's under various names (office automation, workflow management, business process management) and by different communities, including the database community. Much basic and applied research has been conducted over the years, e.g. theoretical studies of workflow languages and models (based on Petri-nets or process calculi), their properties, transactional behavior, etc."
"The addition of stringent security specifications to the list of requirements for an application poses many new problems in DBMS design and implementation, as well as database design, use, and maintenance. Tight security requirements, such as those that result in silent masking of witholding of true information from a user or the introduction of false information into query answers, also raise fundamental questions about the meaning of the database and the semantics of accompanying query languages. In this paper, we propose a belief-based semantics for secure databases, which provides a semantics for databases that can ¡°lie¡± about the state of the world, or about their knowledge about the state of the world, in order to preserve security. This kind of semantics can be  used as a helpful retrofit for the proposals for a ¡°multilevel secure¡± database model (a particularly stringent form of security), and may be useful for less restrictive security policies as well. We also propose a family of query languages for multilevel secure relational database applications, and base the semantics of those languages on our semantics for secure databases. Our query languages are free of the semantic problems associated with use of ordinary SQL in a multilevel secure context, and should be easy for users to understand and employ."
"In a previous paper we proposed a novel method for generating alternative query plans that uses chasing (and back-chasing) with logical constraints. The method brings together use of indexes, use of materialized views, semantic optimization and join elimination (minimization). Each of these techniques is known separately to be beneficial to query optimization. The novelty of our approach is in allowing these techniques to interact systematically, eg. non-trivial use of indexes and materialized views may be enabled only by semantic constraints."
"Exploratory search requires the system to assist the user in comprehending the information space and expressing evolving search intents for iterative exploration and retrieval of information. We introduce interactive intent modeling, a technique that models a user¡¯s evolving search intents and visualizes them as keywords for interaction. The user can provide feedback on the keywords, from which the system learns and visualizes an improved intent estimate and retrieves information. We report experiments comparing variants of a system implementing interactive intent modeling to a control system. Data comprising search logs, interaction logs, essay answers, and questionnaires indicate significant improvements in task performance, information retrieval performance over the session, information comprehension performance, and user experience. The improvements in retrieval effectiveness can be attributed to the intent modeling and the effect on users¡¯ task performance, breadth of information comprehension, and user experience are shown to be dependent on a richer visualization. Our results demonstrate the utility of combining interactive modeling of search intentions with interactive visualization of the models that can benefit both directing the exploratory search process and making sense of the information space. Our findings can help design personalized systems that support exploratory information seeking and discovery of novel information."
"This session had three papers that exploit today's wide range of storage devices and the power of the Internet to deliver data transparently. The first described a product for managing a storage hierarchy for extremely large, multi-media databases (petabytes or even exabytes ¡­"
An efficient management of multiversion data with branched evolution is crucial for many applications. It requires database designers aware of tradeoffs among index structures and policies. This paper defines a framework and an analysis method for understanding the behavior of different indexing policies. Given data and query characteristics the analysis allows determining the most suitable index structure. The analysis is validated by an experimental study.
"Statistical databases often use random data perturbation (RDP) methods to protect against disclosure of confidential numerical attributes. One of the key requirements of RDP methods is that they provide the appropriate level of security against snoopers who attempt to obtain information on confidential attributes through statistical inference. In this study, we evaluate the security provided by three methods of perturbation. The results of this study allow the database administrator to select the most effective RDP method that assures adequate protection against disclosure of confidential information."
"The InfoSleuth Project at MCC [7, 9, 8, 1] is developing and deploying technologies for finding information in corp~ rate networks and in external networka, such as networks baaed on the emerging National Information Infrastructure. InfoSleuth is baaed on MCC¡¯S previously developed Carnot technology [2, 6, 10], which was successfully used to integrate heterogeneous information resources. The Carnot project developed semantic modeling techniques that enable description of the information resources and pioneered the use of agents to provide interoperation among autonomous systems. The InfoSleuth Project investigates the use of Carnot technologies in a dynamically changing environment, such as the Internet, where there is no formal control of the registration of new information sources and the identities of the resources to be used may be unknown at the time the application is developed. InfoSleuth deploys semantic agents [9, 5, 3] that carry out coordinated searches and cooperate with each other to merge the retrieved data into understandable information. The project is developing technologies to support mediated interoperation of data and services over information networks in a dynamically changing environment, including:"
"General-purpose commercial disk-based database systems, though widely employed in practice, have failed to meet the performance requirements of applications requiring short, predictable response times, and extremely high throughput rates. Main memory is the only technology capable of these characteristics. DataBlitz is a main-memory storage manager product that supports the development of high-performance and fault-resilient applications requiring concurrent access to shared data. In DataBlitz, core algorithms for concurrency, recovery, index management and space management are optimized for the case that data is memory resident."
"An order-dependent query is one whose result (interpreted as a multiset) changes if the order of the input records is changed. In a stock-quotes database, for instance, retrieving all quotes concerning a given stock for a given day does not depend on order, because the collection of quotes does not depend on order. By contrast, finding a stock's five-price moving-average in a trades table gives a result that depends on the order of the table. Query languages based on the relational data model can handle order-dependent queries only through add-ons. SQL:1999, for instance, has a new ""window"" mechanism which can sort data in limited parts of a query. Add-ons make order-dependent queries di_cult to write and to optimize. In this paper we show that order can be a natural property of the underlying data model and algebra. We introduce a new query language and algebra, called AQuery, that supports order from-the-ground-up. New order-related query transformations arise in this setting. We show by experiment that this framework - language plus optimization techniques - brings orders-of-magnitude improvement over SQL:1999 systems on many natural order-dependent queries."
"Abstract. The requirements of wide-area distributed database systems differ dramatically from those of local-area network systems. In a wide-area network (WAN) configuration, individual sites usually report to different system administrators, have different access and charging algorithms, install site-specific data type extensions, and have different constraints on servicing remote requests. Typical of the last point are production transaction environments, which are fully engaged during normal business hours, and cannot take on additional load. Finally, there may be many sites participating in a WAN distributed DBMS.  In this world, a single program performing global query optimization using a cost-based optimizer will not work well. Cost-based optimization does not respond well to site-specific type extension, access constraints, charging algorithms, and time-of-day constraints. Furthermore, traditional cost-based distributed optimizers do not scale well to a large number of possible processing sites. Since traditional distributed DBMSs have all used cost-based optimizers, they are not appropriate in a WAN environment, and a new architecture is required.  We have proposed and implemented an economic paradigm as the solution to these issues in a new distributed DBMS called Mariposa. In this paper, we present the architecture and implementation of Mariposa and discuss early feedback on its operating characteristics. "
"More and more databases are becoming Web accessible through form-based search interfaces, and many of these sources are E-commerce sites. Providing a unified access to multiple E-commerce search engines selling similar products is of great importance in allowing users to search and compare products from multiple sites with ease. One key task for providing such a capability is to integrate the Web interfaces of these E-commerce search engines so that user queries can be submitted against the integrated interface. Currently, integrating such search interfaces is carried out either manually or semi-automatically, which is inefficient and difficult to maintain. In this paper, we present WISE-Integrator - a tool that performs automatic integration of Web Interfaces of Search Engines. WISE-Integrator employs sophisticated techniques to identify matching attributes from different search interfaces for integration. It also resolves domain differences of matching attributes. Our experimental results based on 20 and 50 interfaces in two different domains indicate that WISE-Integrator can achieve high attribute matching accuracy and can produce high-quality integrated search interfaces without human interactions."
"An algorithm is presented for finding the k nearest neighbors in a spatial network in a best-first manner using network distance. The algorithm is based on precomputing the shortest paths between all possible vertices in the network and then making use of an encoding that takes advantage of the fact that the shortest paths from vertex u to all of the remaining vertices can be decomposed into subsets based on the first edges on the shortest paths to them from u. Thus, in the worst case, the amount of work depends on the number of objects that are examined and the number of links on the shortest paths to them from q, rather than depending on the number of vertices in the network. The amount of storage required to keep track of the subsets is reduced by taking advantage of their spatial coherence which is captured by the aid of a shortest path quadtree. In particular, experiments on a number of large road networks as well as a theoretical analysis have shown that the storage has been reduced from O(N3) to O(N1.5) (i.e., by an order of magnitude equal to the square root). The precomputation of the shortest paths along the network essentially decouples the process of computing shortest paths along the network from that of finding the neighbors, and thereby also decouples the domain S of the query objects and that of the objects from which the neighbors are drawn from the domain V of the vertices of the spatial network. This means that as long as the spatial network is unchanged, the algorithm and underlying representation of the shortest paths in the spatial network can be used with different sets of objects."
"The Object Database Management Group (ODMG) is a consortium of object-oriented DBMS vendors that have developed a standard interface for their products, ODMG-93. The standard includes a common architecture and deftition for an object-oriented DBMS, a common object model with an object deftition language, a common object query language, and standardized progr amming language bindings, cumently for C++ and Smalltalk. An object-oriented DBMS (by ODMG¡¯S defiition) provides programming language bindings with direct, transparent persistence for data structures, in contrast to the embedded language bindings used in most DBMSS. The common object model allows data to be shared across programming languages. This model incorporates object Ills, encapsulation, methods, frost-class types, multiple inheritance, relationships, lists, sets, bags, arrays, and many other features."
"Welcome to the second installment in the SIGMOD Record's series of interviews with pillars of the database community. In the last issue we heard from Jeff Ullman, and upcoming issues will include conversations with This issue's interview with Gio Wiederhold took place in June 2001, a few days before the festivities associated with Gio's retirement from Stanford University. Gio has been a member of the Stanford faculty for many years, active both in computer science and in medical informatics. In the late 1980s, Gio also spent several years as a program manager at DARPA, focusing on middleware and mediators. Gio is an ACM Fellow, an"
"As the cost of both hardware and software falls due to technological advancements and economies of scale, the cost of ownership for database applications is increasingly dominated by the cost of people to manage them. Databases are growing rapidly in scale and complexity, while skilled database administrators (DBAs) are becoming rarer and more expensive. This paper describes the self-managing or autonomic technology in IBM's DB2 Universal Database? for UNIX and Windows to illustrate how self-managing technology can reduce complexity, helping to reduce the total cost of ownership (TCO) of DBMSs and improve system performance."
"With the popularity of XML, it is increasingly common to nd data in the XML format. This highlights an important question: given an XML document S and a DTD D, how to extract data from S and construct another XML document T such that T conforms to the xed D? Let us refer to this as DTD-conforming XML to XML transformation. The need for this is evident in, e.g., data exchange: enterprises exchange their XML documents with respect to a certain prede ned DTD. Although a number of XML query languages (e.g., XQuery, XSLT) are currently being used to transform XML data, they cannot guarantee DTD conformance. Type inference and (static) checking for XML transformations are too expensive [1] to be used in practice; worse, they provide no guidance for how to specify a DTD-conforming XML to XML transformation. In response to the need we have developed TREX (TRansformation Engine for XML), a middleware system for DTDconforming XML to XML transformations. TREX is based on the novel notion of XTG (XML Transformation Grammar), which extends a DTD by incorporating semantic rules de ned with XML queries (expressed in Quilt [5]). This allows one to specify how to extract relevant data from a source XML document via the queries, and to construct a target XML document directed by the embedded DTD. TREX supports XTGs using Kweelt [6] as the underlying engine for XML queries (the reason for choosing Quilt rather than XQuery/XSL is that we could access the source code of Kweelt to incorporate our optimization algorithms). "
"A frequently encountered type of query in Geographic Information Systems is to find the k nearest neighbor objects to a given point in space. Processing such queries requires substantially different search algorithms than those for location or range queries. In this paper we present an efficient branch-and-bound R-tree traversal algorithm to find the nearest neighbor object to a point, and then generalize it to finding the k nearest neighbors. We also discuss metrics for an optimistic and a pessimistic search ordering strategy as well as for pruning. Finally, we present the results of several experiments obtained using the implementation of our algorithm and examine the behavior of the metrics and the scalability of the algorithm."
"Most modern DBMS optimizers rely upon a cost model to choose the best query execution plan (QEP) for any given query. Cost estimates are heavily dependent upon the optimizer¡¯s estimates for the number of rows that will result at each step of the QEP for complex queries involving many predicates and/or operations. These estimates rely upon statistics on the database and modeling assumptions that may or may not be true for a given database. In this paper we introduce LEO, DB2's LEarning Optimizer, as a comprehensive way to repair incorrect statistics and cardinality estimates of a query execution plan. By monitoring previously executed queries, LEO compares the optimizer¡¯s estimates with actuals at each step in a QEP, and computes adjustments to cost estimates and statistics that may be used during future query optimizations. This analysis can be done either on-line or off-line on a separate system, and either incrementally or in batches. In this way, LEO introduces a feedback loop to query optimization that enhances the available information on the database where the most queries have occurred, allowing the optimizer to actually learn from its past mistakes. Our technique is general and can be applied to any operation in a QEP, including joins, derived results after several predicates have been applied, and even to DISTINCT and GROUP-BY operators. As shown by performance measurements on a 10 GB TPCH data set, the runtime overhead of LEO¡¯s monitoring is insignificant, whereas the potential benefit to response time from more accurate cardinality and cost estimates can be orders of magnitude."
"Integrated access to heterogeneous information is an increasingly important topic as more and more sources that developed independently from each other become accessible over networks. The structure of the information and the abilities of the sources to answer queries may vary widely. Therefore, systems are needed that are able to use knowledge about the contents and the capabilities of sources to break down a global query into portions that can be processed locally and to reassemble the answers. Problems of this kind arise when one ¡­"
"In order to faithfully describe real-life applications, knowledge bases have to manage general integrity constraints. In this article, we analyse methods for an efficient verification of integrity constraints in updated knowledge bases. These methods rely on the satisfaction of the integrity constraints before the update for simplifying their evaluation in the updated knowledge base. During the last few years, an increasing amount of publications has been devoted to various aspects of this problem. Since they use distinct formalisms and different terminologies, they are difficult to compare. Moreover, it is often complex to recognize commonalities and to find out whether techniques described in different articles are in principle different. A first part of this report aims at giving a comprehensive state-of-the-art in integrity verification. It describes integrity constraint verification techniques in a common formalism. A second part of this report is devoted to comparing several proposals. The differences and similarities between various methods are investigated."
"Execution of multidatabase queries differs from that of traditional queries in that sort merge and hash joins are more often favored, as nested loop join requires repeated accesses to external data sources. As a consequence, left deep join trees obtained by traditional (e.g., System-R style) optimizers for multidatabase queries are often suboptimal, with respect to response time, due to the long delay for a sort merge (or hash) join node to produce its last result after the subordinate join node did. In this paper, we present an optimization strategy that first produces an optimal left deep join tree and then reduces the response time using simple tree transformations. This strategy has the advantages of guaranteed minimum total resource usage, improved response time, and low optimization overhead. We describe a class of basic transformations that is the cornerstone of our approach. Then we present algorithms that effectively apply basic transformations to balance a left deep join tree, and discuss how the technique can be incorporated into existing query optimizers."
"The Teradata Multimedia Object Manager is a general-purpose content analysis multimedia server designed for symmetric multiprocessing and massively parallel processing environments. The Multimedia Object Manager defines and manipulates user-defined functions (UDFs), which are invoked in parallel to analyze or manipulate the contents of multimedia objects. Several computationally intensive applications of this technology, which use large persistent datasets, include fingerprint matching, signature verification, face recognition, and speech recognition/translation."
"1 Introduction Histograms are commonly used to capture attribute value distribution statistics for query optimizers. More recently, histograms have also been considered as a way to produce quick approximate answers to decision support queries. This widespread interest in histograms motivates the problem of computing his-tograms that are good under a given error metric. In particular, we are interested in an efficient algorithm for choosing the bucket boundaries in a way that either minimizes the estimation error for a given amount of space (number of buckets) or, conversely, minimizes the space needed for a given upper bound on the error. Under the assumption that finding optimal bucket boundaries is computationally inefficient, previous research has focused on heuristics with no provable bounds on the quality of the solutions. In this paper, we present algorithms for computing optimal bucket boundaries in time proportional to the square of the number of distinct data values, for a broad class of optimality metrics. This class includes the V-Optimality constraint, which has been shown to result in the most accurate histograms for several selectivity estimation problems. Through experiments , we show that optimal histograms can achieve substantially lower estimation errors than histograms produced by popular heuristics. We also present new heuristics with provably good space-accuracy trade-offs that are significantly faster than the optimal algorithm. Finally, we present an enhancement to traditional histograms that allows us to provide quality guarantees on individual selectivity estimates. In our experiments, these quality guarantees were highly effective in isolating outliers in selectivity estimates. It is often the case that a data set cannot be stored or processed in its entirety; only a summarized form is stored. A typical way in which data is summarized is by means of a histogram. The summarized data can be used to answer various kinds of queries, in the same way the original data would have been used. The answer obtained is not exact but approximate, and contains an error due to the information lost when the data was summarized. This error can be measured according to some appropriate metric such as the maximum , average, or mean squared error of the estimate. This basic idea has long been used in a database context to estimate the result sizes of relational operators for the purpose of cost-based query optimization. The objective is to approximate the data distribution of the values in a column, and to use that ¡­"
"In order to process interval timestamped data, the sequenced semantics has been proposed. This paper presents a relational algebra solution that provides native support for the three properties of the sequenced semantics: snapshot reducibility, extended snapshot reducibility, and change preservation. We introduce two temporal primitives, temporal splitter and temporal aligner, and define rules that use these primitives to reduce the operators of a temporal algebra to their nontemporal counterparts. Our solution supports the three properties of the sequenced semantics through interval adjustment and timestamp propagation. We have implemented the temporal primitives and reduction rules in the kernel of PostgreSQL to get native database support for processing interval timestamped data. The support is comprehensive and includes outer joins, antijoins, and aggregations with predicates and functions over the time intervals of argument relations. The implementation and empirical evaluation confirms effectiveness and scalability of our solution that leverages existing database query optimization techniques."
"Continuous media servers that provide support for the storage and retrieval of continuous media data (e.g., video, audio) at guaranteed rates are becoming increasingly important. Such servers, typically, rely on several disks to service a large number of clients, and are thus highly susceptible to disk failures. We have developed two fault-tolerant approaches that rely on admission control in order to meet rate guarantees for continuous media requests. The schemes enable data to be retrieved from disks at the required rate even if a certain disk were to fail. For both approaches, we present data placement strategies and admission control algorithms. We also present design techniques for maximizing the number of clients that can be supported by a continuous media server. Finally, through extensive simulations, we demonstrate the effectiveness of our schemes."
"Techniques are presented for navigating between adjacent triangles of greater or equal size in a hierarchical triangle mesh where the triangles are obtained by a recursive quadtree-like subdivision of the underlying space into four equilateral triangles. These techniques are useful in a number of applications, including finite element analysis, ray tracing, and the modeling of spherical data. The operations are implemented in a manner analogous to that used in a quadtree representation of data on the two-dimensional plane where the underlying space is tessellated into a square mesh. A new technique is described for labeling the triangles, which is useful in implementing the quadtree triangle mesh as a linear quadtree (i.e., a pointer-less quadtree); the navigation can then take  place in this linear quadtree. When the neighbors are of equal size, the algorithms have a worst-case constant time complexity. The algorithms are very efficient, as they make use of just a few bit manipulation operations, and can be implemented in hardware using just a few machine language instructions. The use of these techniques when modeling spherical data by projecting it onto the faces of a regular solid whose faces are equilateral triangles, which are represented as quadtree triangle meshes, is discussed in detail. The methods are applicable to the icosahedron, octahedron, and tetrahedron. The difference lies in the way transitions are made between the faces of the polyhedron. However, regardless of the type of polyhedron, the computational complexity of the methods is the  same."
"This is my first issue as associate editor of software reviews for The American Statistician. In this column, I will introduce myself, comment on the types of software reviews that can be published in this section of The American Statistician, and encourage others in the profession to consider taking on the task of reviewing statistical software packages. I first began reading statistical software reviews in this journal when enrolled in my doctoral program in biostatistics. I read a number of excellent reviews and found the information they contained helpful in my own research, in class projects, and in collaborative work that I was doing at the time. I became interested in writing software reviews while completing my dissertation and contacted Dr. Richard Goldstein, at that time the journal?s software reviews editor. "
"Views are a central component of both traditional database systems and new applications such as data warehouses. Very often the desired views (e.g. the transitive closure) cannot be defined in the standard language of the underlying database system. Fortunately, it is often possible to incrementally maintain these views using the standard language. For example, transitive closure of acyclic graphs, and of undirected graphs, can be maintained in relational calculus after both single edge insertions and deletions. Many such results have been published in the theoretical database community. The purpose of this survey is to make these useful results known to the wider database research and development community."
"IBM's SMART (Self-Managing And Resource Tuning) project aims to make DB2 self-managing, i.e. autonomic, to decrease the total cost of ownership and penetrate new markets. Over several releases, increasingly sophisticated SMART features will ease administrative tasks such as initial deployment, database design, system maintenance, problem determination, and ensuring system availability and recovery."
"Current search engines can hardly cope adequately with fuzzy predicates defined by complex preferences. The biggest problem of search engines implemented with standard SQL is that SQL does not directly understand the notion of preferences. Preference SQL extends SQL by a preference model based on strict partial orders (presented in more detail in the companion paper [Kie02]), where preference queries behave like soft selection constraints. Several built-in base preference types and the powerful Pareto operator, combined with the adherence to declarative SQL programming style, guarantees great programming productivity. The Preference SQL optimizer does an efficient re-writing into standard SQL, including a high-level implementation of the skyline perator for Pareto-optimal sets. This pre-processor approach enables a seamless application integration, making Preference SQL available on all major SQL platforms. Several commercial B2C portals are powered by Preference SQL. Its benefits comprise cooperative query answering and smart customer advice, leading to higher e-customer satisfaction and shorter development times of personalized search engines. We report practical experiences ranging from m-commerce and comparison shopping to a large-scale performance test for a job portal."
"The field of fuzzy information systems has grown and is maturing. In this paper, some applications of fuzzy set theory to information retrieval are described, as well as the more recent outcomes of research in this field. Fuzzy set theory is applied to information retrieval with the main aim being to define flexible systems, i.e., systems that can represent and manage the vagueness and subjectivity which characterizes the process of information representation and retrieval, one of the main objectives of artificial intelligence."
"In this paper, we study the progressive evaluation of nested queries with aggregates (i.e., the inner query block is an aggregate query), where users are provided progressively with (approximate) answers as the inner query block is being evaluated. We propose an in-cremental evaluation strategy to present answers that are certainly in the nal answer space rst, before presenting those whose validity may be aaected as the inner query aggregates are reened. We also propose a multi-threaded model in evaluating such queries: the outer query is assigned to a thread, and the inner query is assigned to another thread. The time-sliced across the two subqueries is nonde-terministic in the sense that the user controls the relative rate at which these subqueries are being evaluated. We implemented a prototype system using JAVA, and evaluated our system. Our results show the eeectiveness of the proposed mechanisms in providing online feedback that reduces the initial waiting time of users signiicantly without sacriicing on the quality of the answers."
We demonstrate a visual based XML-Relational database system where XML data is managed by commercial RDBMS. A query interface enables users to form path expression based queries against stored data visually. Statistics about data and a special path directory are used to rewrite path expression based queries into efficient SQL statements involving less number of joins.
"Managing multiple versions of XML documents represents an important problem, because of many applications ranging from traditional ones, such as software configuration control, to new ones, such as link permanence of web documents. Research on managing multiversion XML documents seeks to provide efficient and robust techniques for (i) storing and retrieving, (ii) exchanging, and (iii) querying such documents. In this paper, we first show that traditional version control methods, such as RCS, and SCCS, fall short from satisfying these three requirements, and discuss alternative solutions. First, we enhance RCS with a temporal page clustering policy to achieve objective (i). Then, we discuss a reference-based versioning scheme that achieves both objectives (i) and (ii) and is also effective at supporting simple queries. The topic of supporting complex queries, including temporal ones, meshes with the burgeoning interest of database researchers in XML as a database description language, and in XML query languages. In this context, the XML versioning problems are akin to those of transaction time management for databases of objects and semistructured information. Nevertheless, the need to preserve the natural ordering of XML documents frequently requires different techniques."
"Internet-based communication defines two main types of services as Pull and Push services, depending on the side that sends the request for transmission of information. In contrast to Pull services, whose request for transmission is initiated by the client, Push service denotes a type of transmission where the request for a given exchange of information is initiated by the publisher or central server. The newly proposed Alert Notification Service (ANS) represents an important implementation of these Push services, for the sites that neither implement it or that think it is not worth to do it economically. In this paper we present details on system functionalities, architecture model, design, and integration of essential modules into a fully working system as a service. The main contribution is in design of a highly scalable solution for an elastic cloud architecture, by separating the static and dynamic parts, correspondingly assigned to different virtual machines."
"Reorganization of objects in an object databases is an important component of several operations like compaction, clustering, and schema evolution. The high availability requirements (24 ¡Á 7 operation) of certain application domains requires reorganization to be performed on-line with minimal interference to concurrently executing transactions."
"Spatial indexes play a major role in fast access to spatial and location data. Most commercial applications insert new data in bulk: in batches or arrays. In this paper, we propose a novel bulk insertion technique for R-Trees that is fast and does not compromise on the quality of the resulting index. We present our experiences with incorporating the proposed bulk insertion strategies into Oracle 10i. Experiments with real datasets show that our bulk insertion strategy improves performance of insert operations by 50%-90%."
"In recent years, many data mining methods have been proposed for finding useful and structured information from market basket data. The association rule model was recently proposed in order to discover useful patterns and dependencies in such data. This paper discusses a method for indexing market basket data efficiently for similarity search. The technique is likely to be very useful in applications which utilize the similarity in customer buying behavior in order to make peer recommendations. We propose an index called the signature table, which is very flexible in supporting a wide range of similarity functions. The construction of the index structure is independent of the similarity function, which can be specified at query time. The resulting similarity search algorithm shows excellent scalability with increasing memory availability and database size."
"Histograms are frequently used to represent the distribution of data values in an attribute of a relation. Most previous work has focused on identifying the optimal histogram (given a limited number of buckets) for a single attribute independent of other attributes/histograms. In this paper, we propose the idea of global optimization of histograms, i.e., single-attribute histograms for a set of attributes are optimized collectively so as to minimize the overall error in using the histograms. The idea is to allocate more buckets to histograms whose attributes are more frequently used and/or distributions are highly skewed. While the accuracy of some histograms is penalized (being assigned fewer buckets), we expect the global error to be low compared to the traditional method (of allocating equal number of buckets to each histogram)."
"Database systems offer efficient and reliable technology to query structured data. However, because of the explosion of the World Wide Web [11], an increasing amount of information is stored in repositories organized according to less rigid structures, usually as hypertextual documents, and data access is based on browsing and information retrieval techniques. Since browsing and search engines present important limitations [8], several query languages [19, 20, 23] for the Web have been recently proposed. These approaches are mainly based on a loose notion of structure, and tend to see the Web as a huge collection of unstructured objects, organized as a graph. Clearly, traditional database techniques are of little use in this field, and new techniques need to be developed. In this paper, we present the approach to the management of Web data as attacked in the ArtANEUS project carried out by the database group at Universith di l=toma Tre. Our approach is based on a generalization of the notion of view to the Web framework. In fact, in traditional databases, views represent an essential tool for restructuring and integrating da ta to be presented to the user. Since the Web is becoming a major computing platform and a uniform interface for sharing data, we believe that also in this field a sophisticate view mechanism is needed, with novel features due to the semi-structured nature of the Web. First, in this context, restructuring and presenting da ta under different perspectives requires the generation of derived Web hypertexts, in order to re-organize and re-use portions of the Web. To do this, da ta from existing Web sites must be extracted, and then queried and integrated in order to build new hypertexts, i.e., hypertextual views over the original sites; these manipulations can be better attained in a more structured framework, in which traditional database technology can be leveraged to analyze and correlate information. Therefore, there seem to be different view levels in this framework: (i) at the first level, da ta are extracted from the sites of interest and given a database structure, which represents a first structured view over the original semi-structured data; (ii) then, further database views can be built by means of reorganizations and integrations based on traditional database techniques; (iii) finally, a derived hypertext can be generated offering an alternative or integrated hypertextual view over the original sites. In the process, data go from a loosely structured organizat ion-the Web pages-to a very structured onethe database--and then again to Web structures."
"Our experience with the SIFT [YGM95] information dissemination system (in use by over 7,000 users daily) has identified an important and generic dissemination problem: duplicate information. In this paper we explain why duplicates arise, we quantify the problem, and we discuss why it impairs information dissemination. We then propose a Duplicate Removal Module (DRM) for an information dissemination system. The removal of duplicates operates on a per user, per document basis each document read by a user generates a request, or a duplicate restraint. In wide-area environments, the number of restraints handled is very large. We consider the implementation of a DRM, examining alternative algorithms and data structures that may be used. We present a performance evaluation of the alternatives and answer important design questions such as: Which implementation is the best? With ¡°best¡± scheme, how expensive will duplicate removal be? How much memory is required? How fast can restraints be processed?"
"The problem of answering queries using views is to find efficient methods of answering a query using a set of previously materialized views over the database, rather than accessing the database relations. The problem has received significant attention because of its relevance to a wide variety of data management problems, such as data integration, query optimization, and the maintenance of physical data independence. To date, the performance of proposed algorithms has received very little attention, and in particular, their scale up in the presence of a large number of views is unknown. We first analyze two previous algorithms, the bucket algorithm and the inverse-rules, and show their deficiencies. We then describe the MiniCon, a novel algorithm for finding the maximally-contained rewriting of a conjunctive query using a set of conjunctive views. We present the first experimental study of algorithms for answering queries using views. The study shows that the MiniCon scales up well and significantly outperforms the previous algorithms. We describe an extension of the MiniCon to handle comparison predicates, and show its performance experimentally. Finally, we describe how the MiniCon can be extended to the context of query optimization."
"Making a database system active entails developing an expressive event specification language with well-defined semantics, algorithms for the detection of composite events, and an architecture for an event detector along with its implementation. Thii paper presents the semantics of composite events using the notion of a global event history (or a global event-log). Parameter contexts are introduced and precisely defined to facilitate efficient management and detection of composite events. Finally, an architecture and the implementation of a composite event, detector is analyzed in the context of an object-oriented active DBMS."
"Charles Schwab and Co, Inc. is a major web trader generating a large proportion of its revenue from the Web. That revenue is based on both having a site with lots of useful facilities and also the speed of execution, ability to cope with peaks in demand volumes, and the reliability of the site and its underlying services. James Chong, VP Architecture and Planning at Schwab, will talk about the fundamental infrastructure that supports the Web trading, and his plans for its evolution."
"Multilevel relations, based on the current multilevel secure (MLS) relational data models, can present a user with information that is difficult to interpret and may display an inconsistent outlook about the views of other users. Such ambiguity is due to the lack of a comprehensive method for asserting and interpreting beliefs about lower level information. In this paper we identify different beliefs that can be held by higher level users about lower level information, and we introduce the new concept of a mirage tuple. We present a mechanism for asserting beliefs about all accessible tuples, including lower level tuples. This mechanism provides every user of an MLS database with an unambiguous interpretation of all viewable information and presents a consistent account of the views at all levels below the user's level."
"When implementing persistent objects on a relational database, a major performance issue is prefetching data to minimize the number of round-trips to the database. This is especially hard with navigational applications, since future accesses are unpredictable. We propose the use of the context in which an object is loaded as a predictor of future accesses, where a context can be a stored collection of relationships, a query result, or a complex object. When an object O's state is loaded, similar state for other objects in O's context is prefetched. We present a design for maintaining context and for using it to guide prefetch. We give performance measurements of its implementation in Microsoft Repository, showing up to a 70% reduction in running time. We describe several variations of the optimization: selectively applying the technique based on application and database characteristics, using application-supplied performance hints, using concurrent database queries to support asynchronous prefetch, prefetching across relationship paths, and delayed prefetch to save database round-trips."
"Recent results in the Rio project at the University of Michigan show that it is possible to create an area of main memory that is as safe as disk from operating system crashes. This paper explores how to integrate the reliable memory provided by the Rio file cache into a database system. Prior studies have analyzed the performance benefits of reliable memory; we focus instead on how different designs affect reliability. We propose three designs for integrating reliable memory into databases: non-persistent database buffer cache, persistent database buffer cache, and persistent database buffer cache with protection. Non-persistent buffer caches use an I/O interface to reliable memory and require the fewest modifications to existing databases. However, they waste memory capacity and bandwidth due to double buffering. Persistent buffer caches use a memory interface to reliable memory by mapping it into the database address space. This places reliable memory under complete database control and eliminates double buffering, but it may expose the buffer cache to database errors. Our third design reduces this exposure by write protecting the buffer pages. Extensive fault tests show that mapping reliable memory into the database address space does not significantly hurt reliability. This is because wild stores rarely touch dirty, committed pages written by previous transactions. As a result, we believe that databases should use a memory interface to reliable memory."
"Spatio-temporal databases deal with geometries changing over time. The goal of our work is to provide a DBMS data model and query language capable of handling such time-dependent geometries, including those changing continuously that describe moving objects. Two fundamental abstractions are moving point and moving region, describing objects for which only the time-dependent position, or position and extent, respectively, are of interest. We propose to present such time-dependent geometries as attribute data types with suitable operations, that is, to provide an abstract data type extension to a DBMS data model and query language. This paper presents a design of such a system of abstract data types. It turns out that besides the main types of interest, moving point   and moving region, a relatively large number of auxiliary data types are needed. For example, one needs a line type to represent the projection of a moving point into the plane, or a ¡°moving real¡± to represent the time-dependent distance of two points. It then becomes crucial to achieve (i) orthogonality in the design of the system, i.e., type constructors can be applied unifomly; (ii) genericity and consistency of operations, i.e., operations range over as many types as possible and behave consistently; and (iii) closure and consistency between structure and operations of nontemporal and related temporal types. Satisfying these goal leads to a simple and expressive system of abstract data types that may be integrated into a query language to yield a powerful language for   querying spatio-temporal data, including moving objects. The paper formally defines the types and operations, offers detailed insight into the considerations that went into the design, and exemplifies the use of the abstract data types using SQL. The paper offers a precise and conceptually clean foundation for implementing a spatio-temporal DBMS extension."
"One of the critical deficiencies of SQL is lack of support for n-dimensional array-based computations which are frequent in OLAP environments. Relational OLAP (ROLAP) applications have to emulate them using joins, recently introduced SQL Window Functions [18] and complex and inefficient CASE expressions. The designated place in SQL for specifying calculations is the SELECT clause, which is extremely limiting and forces the user to generate queries using nested views, subqueries and complex joins. Furthermore, SQL-query optimizer is pre-occupied with determining efficient join orders and choosing optimal access methods and largely disregards optimization of complex numerical formulas. Execution methods concentrated on efficient computation of a cube [11], [16] rather than on random access structures for inter-row calculations. This has created a gap that has been filled by spreadsheets and specialized MOLAP engines, which are good at formulas for mathematical modeling but lack the formalism of the relational model, are difficult to manage, and exhibit scalability problems. This paper presents SQL extensions involving array based calculations for complex modeling. In addition, we present optimizations, access structures and execution models for processing them efficiently."
"Schema evolution is a problem that is faced by long-lived data. When a schema changes, existing persistent data can become inaccessible unless the database system provides mechanisms to access data created with previous versions of the schema. Most existing systems that support schema evolution focus on changes local to individual types within the schema, thereby limiting the changes that the database maintainer can perform. We have developed a model of type changes involving multiple types. The model describes both type changes and their impact on data by defining derivation rules to initialize new data based on the existing data. The derivation rules can describe local and nonlocal changes to types to capture the intent of a large class of type change operations. We have built a system   called Tess (Type Evolution Software System) that uses this model to recognize type changes by comparing schemas and then produces a transformer that can update data in a database to correspond to a newer version of the schema."
"We discuss several important issues specific to Web caching for content dynamically generated from database applications. We present the techniques employed by Oracle Web Cache to address these issues. They include: content disambiguation based on information in addition to the URL, transparent session management, partial-page caching for personalization, and broad-scope invalidation with performance assurance heuristics."
"Many researchers have investigated the process of decomposing transactions into smaller pieces to increase concurrency. The research typically focuses on implementing a decomposition supplied by the database application developer, with relatively little attention to what constitutes a desirable decomposition and how the developer should obtain such a decomposition. In this paper, we argue that the decomposition process itself warrants attention. A decomposition generates a set of proof obligations that must be satisfied to show ¡­"
"Data cube enables fast online analysis of large data repositories which is attractive in many applications. Although there are several kinds of available cube-based OLAP products, users may still encounter challenges on effectiveness and efficiency in the exploration of large data cubes due to the huge computation space as well as the huge observation space in a data cube. CubeExplorer is an integrated environment for online exploration of data cubes. It integrates our newly developed techniques on iceberg cube computation [2], cube-based feature extraction, and gradient analysis [1], and makes cube exploration effective and efficient. In this demo, we will show the features of CubeExplorer, especially its power and flexibility at exploring and mining of large databases."
"Zusammenfassung Obwohl der Einsatz von Data-Warehouse-Systemen zur g?ngigen Praxis moderner IT-Landschaften geh?rt, haben methodische Untersuchungen zum qualit?tsorientierten Schemaentwurf erst in j¨¹ngerer Zeit begonnen. Ausgehend von einem Schemaentwurfsprozess f¨¹r Data-Warehouse-Systeme werden aktuelle Entwicklungen zur Qualit?tssicherung und Data-Warehouse-spezifische Qualit?tskriterien wie Summierbarkeit sowie deren Verallgemeinerung zu mehrdimensionalen Normalformen und Selbstwartbarkeit vorgestellt."
"The major challenges in web mining are a) tracking the data accurately (as not everything is reported to the web server), b) real-time acquisition of the huge volume of data (435 Million visits to yahoo per day, 2-4 GB clickstream data per hour), c) real-time interpretation of the data without compromising the privacy of the user (order of seconds for personalization and targeting information), and d) visualization of the data to facilitate policy making. To address these challenges, we demonstrate an integrated software platform, called INSITE ¨C a) to accurately track users interactions with a web space with minimum overhead and no voluntary user participation, b) to generate individual and aggregate user profiles in real time (or off-line) through the use of a unique Connectivity Matrix Model (CM-model), c) to show the efficacy and scalability of the CM-model in capturing the essence of the users' participatory attributes in the context of the web, d) to visualize the result of clustering of users navigation paths in real time by leveraging on the CM-model, and e) to execute a suite of queries (including temporal ones) and prove the utility of the captured data in making meaningful decisions about user interaction with a web site."
"The Multimedia Description Standard MPEG-7 is an International Standard since February 2002. It defines a huge set of description classes for multimedia content, for its creation and its communication. This article investigates what MPEG-7 means to Multimedia Database Systems (MMDBSs) and vice versa. We argue that MPEG-7 has to be considered complementary to, rather than competing with, data models employed in MMDBSs. Finally we show by an example scenario how these technologies can reasonably complement one another."
"Microsoft.com, is the world's largest corporate website both in terms of site visitors and pages served. Overall, it is the fourth-largest website in total visitors behind America Online, Yahoo and Netscape. We offer 250,000 pages of content, viewable in all major browser versions (yes, we aggressively support Netscape), supported by three server farms internationally and featuring content updated as often as every three hours, seven days a week."
"Indexing a class hierarchy, in order to efficiently search or update the objects of a class according to a (range of) value(s) of an attribute, impacts OODB performance heavily. For this indexing problem, most systems use the class hierarchy index (CH) technique of [15] implemented using B+-trees. Other techniques, such as those of [14, 18,31], can lead to improved average-case performance but involve the implementation of new data-structures. As a special form of external dynamic two-dimensional range searching, this OODB indexing problem is solvable within reasonable worst-case bounds [12]. Based on this insight, we have developed a technique, called indexing by class-division (CD), which we believe can be used as a practical alternative to CH. We present an optimized implementation and experimental validation of CD's average-case performance. The main advantages of the CD technique are: (1) CD is an extension of CH that provides a significant speed-up over CH for a wide spectrum of range queries--this speed-up is at least linear in the number of classes queried for uniform data and larger otherwise; and (2) CD queries, updates and concurrent use are implementable using existing B+-tree technology. The basic idea of class-division involves a time-space tradeoff and CD requires some space and update overhead in comparison to CH. In practice, this overhead is a small factor (2 to 3) and, in worst-case, is bounded by the depth of the hierarchy and the logarithm of its size."
"According to Michael Stonebraker¡¯s experiences, if you select a group of well-known experts in database research and ask them to identify the domains where meeting use+ requirements is of primary importance and at the ¡®same time more significant advances are needed and more research should be promoted, user interfaces comes out as number one in the list. This has been the case over the last decade. Despite such a strong incentive, research on user interfaces seems to remain marginal within the database community. Part of this community considers that this is a domain for development, not for research. Often researchers feel that the specification of an user interface is not much more than assembling widgets in some order. Significantly, the VLDB 94 program offers no contribution on user interfaces. This panel will try to investigate the reasons for such a gap between discourse and practice, and look for remedies. It will start by setting the scene:"
"Data mining applications place special requirements on clustering algorithms including: the ability to find clusters embedded in subspaces of high dimensional data, scalability, end-user comprehensibility of the results, non-presumption of any canonical data distribution, and insensitivity to the order of input records. We present CLIQUE, a clustering algorithm that satisfies each of these requirements. CLIQUE identifies dense clusters in subspaces of maximum dimensionality. It generates cluster descriptions in the form of DNF expressions that are minimized for ease of comprehension. It produces identical results irrespective of the order in which input records are presented and does not presume any specific mathematical form for data distribution. Through experiments, we show that CLIQUE efficiently finds accurate cluster in large high dimensional datasets."
"Query optimizers normally compile queries into one optimal plan by assuming complete knowledge of all cost parameters such as selectivity and resource availability. The execution of such plans could be sub-optimal when cost parameters are either unknown at compile time or change significantly between compile time and runtime [Loh89, GrW89]. Parametric query optimization [INS+92, CG94, GK94] optimizes a query into a number of candidate plans, each optimal for some region of the parameter space. In this paper, we present parametric query optimization algorithms. Our approach is based on the property that for linear cost functions, each parametric optimal plan is optimal in a convex polyhedral region of the parameter space. This property is used to optimize linear and non-linear cost functions. We also analyze the expected sizes of the parametric optimal set of plans and the number of plans produced by the Cole and Graefe algorithm [CG94]."
"You have a tune lingering in your head for many days, but you don¡¯t know where you heard this tune or which song it is from. This demo will show a Query by Humming system that will tell you the name of that song. Most of the research in pre-existing query by humming systems uses pitch contour to match similar melodies (for example [1]). The user¡¯s humming is transcribed to a sequence of discrete notes and the contour information is extracted from the notes. This contour information is represented by a few letters. For example, (¡°U¡±, ¡°D¡±, ¡°S¡±) represents that a note is above, below or the same as the previous one. The tunes in the databases are also represented by contour information. The edit distance can be use to measure the similarity between two melodies. Unfortunately, it is very hard to segment a user¡¯s humming into discrete notes. Some recent work proposes to match the query directly from audio based on dynamic time warping to match the hum-query with the melodies in the music databases. But this quality improvement comes at a price because a brute-force search using DTW is very slow. The database community has been researching problems in similarity query for time series databases for many years. The techniques developed in the area might shed light on the query by humming problem. In this demo, we treat both the melodies in the music databases and the user humming input as time series. Such an approach allows us to integrate many database indexing techniques into a query by humming system, improving the quality of such system over the traditional (contour) string databases approach. We design special searching techniques that are invariant to shifting, time scaling and local time warping. This makes the system robust and allows more flexible user humming input."
We present an information retrieval system that simultaneously allows to search for text and speech documents. The retrieval system accepts vague queries and performs a best-match search to find those documents that are relevant to the query. The output of the retrieval system is a list of ranked documents where the documents on the top of the list satisfy best the user's information need. The relevance of the documents is estimated by means of metadata (document description vectors). The metadata is automatically generated and it is organized such that queries can be processed efficiently. We introduce a controlled indexing vocabulary for both speech and text documents. The size of the new indexing vocabulary is small (1000 features) compared with the sizes of indexing vocabularies of conventional text retrieval (10000 - 100000 features). We show that the retrieval effectiveness based on such a small indexing vocabulary is similar to the retrieval effectiveness of a Boolean retrieval system.
"Recently, Haas and Hellerstein proposed the hash ripple join algorithm in the context of online aggregation. Although the algorithm rapidly gives a good estimate for many join-aggregate problem instances, the convergence can be slow if the number of tuples that satisfy the join predicate is small or if there are many groups in the output. Furthermore, if memory overflows (for example, because the user allows the algorithm to run to completion for an exact answer), the algorithm degenerates to block ripple join and performance suffers. In this paper, we build on the work of Haas and Hellerstein and propose a new algorithm that (a) combines parallelism with sampling to speed convergence, and (b) maintains good performance in the presence of memory overflow. Results from a prototype implementation in a parallel DBMS show that its rate of convergence scales with the number of processors, and that when allowed to run to completion, even in the presence of memory overflow, it is competitive with the traditional parallel hybrid hash join algorithm."
"The Knowledge and Data Base Systems (KDBS) Laboratory was established in 1992 at the National Technical University of Athens. It is recognised internationally, evidenced by its participation as a central node in the Esprit Network of Excellence IDOMENEUS. The Information and Data on Open MEdia for NEtworks of USers, project aims to coordinate and improve European efforts in the development of next-generation information environments which will be capable of maintaining and communicating a largely extended class of information in an open set of media."
"We enunciate the need for watermarking database relations to deter their piracy, identify the unique characteristics of relational data which pose new challenges for watermarking, and provide desirable properties of a watermarking system for relational data. A watermark can be applied to any database relation having attributes which are such that changes in a few of their values do not affect the applications."
"Abstract Many modern programming languages support basic generics, sufficient to implement type-safe polymorphic containers. Some languages have moved beyond this basic support, and in doing so have enabled a broader, more powerful form of generic programming. This paper reports on a comprehensive comparison of facilities for generic programming in eight programming languages: C++, Standard ML, Objective Caml, Haskell, Eiffel, Java, C# (with its proposed generics extension), and Cecil. By implementing a substantial example in each of these languages, we illustrate how the basic roles of generic programming can be represented in each language. We also identify eight language properties that support this broader view of generic programming: support for multi-type concepts, multiple constraints on type parameters, convenient associated type access, constraints on associated types, retroactive modeling, type aliases, separate compilation of algorithms and data structures, and implicit argument type deduction for generic algorithms. We find that these features are necessary to avoid awkward designs, poor maintainability, and painfully verbose code. As languages increasingly support generics, it is important that language designers understand the features necessary to enable the effective use of generics and that their absence can cause difficulties for programmers."
"Peer-to-Peer (P2P) systems are becoming increasingly popular as they enable users to exchange digital information by participating in complex networks. Such systems are inexpensive, easy to use, highly scalable and do not require central administration. Despite their advantages, however, limited work has been done on employing database systems on top of P2P networks.Here we propose the PeerOLAP architecture for supporting On-Line Analytical Processing queries. A large number low-end clients, each containing a cache with the most useful results, are connected through an arbitrary P2P network. If a query cannot be answered locally (i.e. by using the cache contents of the computer where it is issued), it is propagated through the network until a peer that has cached the answer is found. An answer may also be constructed by partial results from many peers. Thus PeerOLAP acts as a large distributed cache, which amplifies the benefits of traditional client-side caching. The system is fully distributed and can reconfigure itself on-the-fly in order to decrease the query cost for the observed workload. This paper describes the core components of PeerOLAP and presents our results both from simulation and a prototype installation running on geographically remote peers."
"Large herbivores can shape young forest stands and determine the successional trajectory of forested ecosystems by selectively browsing palatable species at the sapling stage. Moose (Alces alces) is the dominant vertebrate herbivore in Fennoscandian boreal forests, and high population densities have raised concerns about potential negative effects on ecosystem functioning and properties including biological diversity and timber production. We used 31 herbivore exclosures in Norway to investigate how forests developed after clear-cutting with or without moose present. We tested how tree demography, abundances of understory plant functional groups, community composition, and plant diversity (including bryophytes) across multiple scales varied with moose exclusion. After seven years, the exclosures were dominated by deciduous trees, including many large rowan (Sorbus aucuparia) individuals, a functionally important keystone species. In contrast, the open plots subject to moose impacts (browsing, trampling, defecation) were dominated by economically important coniferous trees and there was next to no rowan recruitment to taller height classes."
"User-defined Aggregates (UDAs) provide a versatile mechanism for extending the power and applicability of Object-Relational Databases (O-R DBs). In this paper, we describe the AXL system that supports an SQLbased language for introducing new UDAs. AXL is easy to learn and use for database programmers because it preserves the constructs, programming paradigm and data types of SQL (whereas there is an ¡®impedance mismatch¡¯ between SQL and the procedural languages of user-defined functions currently used in O-R DBs). AXL will also inherit the benefits of database query languages, such as scalability, data independence and parallelizability. In this paper, we show that, while adding only minimal extensions to SQL, AXL is very powerful and capable of expressing complex algorithms efficiently. We demonstrate this by coding data mining functions and other advanced applications that, previously, had been a major problem for SQL databases. Due to its flexibility, SQL-compatibility and ease of use, the AXL approach offers a better extensibility mechanism, in several application domains, than the function libraries now offered by commercial O-R DBs under names such as Datablades or DB-Extenders. ? Los Angeles CA 90095, USA, hxwang|zaniolo@cs.ucla.edu "
"Performance benchmarking has played an important role in the research and development in relational DBMS, object-relational DBMS, data warehouse systems, etc. We believe that benchmarking data mining algorithms is a long overdue task, and it will play an important role in the research and development of data mining systems as well."
"Inherent in the operation of many decision support and continuous referral systems is the notion of the ¡°influence¡± of a data point on the database. This notion arises in examples such as finding the set of customers affected by the opening of a new store outlet location, notifying the subset of subscribers to a digital library who will find a newly added document most relevant, etc. Standard approaches to determining the influence set of a data point involve range searching and nearest neighbor queries."
"We consider disjunctive Datalog, a powerful database query language based on disjunctive logic programming. Briefly, disjunctive Datalog is a variant of Datalog where disjunctions may appear in the rule heads; advanced versions also allow for negation in the bodies which can be handled according to a semantics for negation in disjunctive logic programming. In particular, we investigate three different semantics for disjunctive Datalog: the minimal model semantics the perfect model semantics, and the stable model semantics. For each of these semantics, the expressive power and complexity are studied. We show that the possibility variants of these semantics express the same set of queries. In fact, they precisely capture the complexity class ¦²P2. Thus, unless the Polynomial   Hierarchy collapses, disjunctive Datalog is more expressive that normal logic programming with negation. These results are not only of theoretical interest; we demonstrate that problems relevant in practice such as computing the optimal tour value in the Traveling Salesman Problem and eigenvector computations can be handled in disjunctive Datalog, but not Datalog with negation (unless the Polynomial Hierarchy collapses). In addition, we study modularity properties of disjunctive Datalog and investigate syntactic restrictions of the formalisms."
"Abstract. Advances in high-speed networks and multimedia technologies have made it feasible to provide video-on-demand (VOD) services to users. However, it is still a challenging task to design a cost-effective VOD system that can support a large number of clients (who may have different quality of service (QoS) requirements) and, at the same time, provide different types of VCR functionalities. Although it has been recognized that VCR operations are important functionalities in providing VOD service, techniques proposed in the past for providing VCR operations may require additional system resources, such as extra disk I/O, additional buffer space, as well as network bandwidth. In this paper, we consider the design of a VOD storage server that has the following features: (1) provision of different levels of display resolutions to users who have different QoS requirements, (2) provision of different types of VCR functionalities, such as fast forward and rewind, without imposing additional demand on the system buffer space, I/O bandwidth, and network bandwidth, and (3) guarantees of the load-balancing property across all disks during normal and VCR display periods. The above-mentioned features are especially important because they simplify the design of the buffer space, I/O, and network resource allocation policies of the VOD storage system. The load-balancing property also ensures that no single disk will be the bottleneck of the system. In this paper, we propose data block placement, admission control, and I/O-scheduling algorithms, as well as determine the corresponding buffer space requirements of the proposed VOD storage system. We show that the proposed VOD system can provide VCR and multi-resolution services to the viewing clients and at the same time maintain the load-balancing property."
"The quality of execution plans generated by a query optimizer is tied to the accuracy of its cardinality estimation. Errors in estimation lead to poor performance, erratic behavior, and user frustration. Traditionally, the optimizer is restricted to use only statistics on base table columns and derive estimates bottom-up. This approach has shortcomings with dealing with complex queries, and with rich languages such as SQL: Errors grow as estimation is done on top of estimation, and some constructs are simply not handled.    In this paper we describe the creation and utilization of statistics on views in SQL Server, which provides the optimizer with statistical information on the result of scalar or relational expressions. It opens a new dimension on the data available for cardinality estimation and enables arbitrary correction. We describe the implementation of this feature in the optimizer architecture, and show its impact on the quality of plans generated through a number of examples."
"The Web has become a major conduit to information repositories of all kinds. Today, more than 80% of information published on the Web is generated by underlying databases (however access is granted through a Web gateway using forms as a query language and HTML as a display vehicle) and this proportion keeps increasing. But Web data sources also consist of standalone HTML pages hand-coded by individuals, that provide very useful information such as reviews, digests, links, etc. As for the information that also exists in underlying databases, the HTML interface is often the only one available for many would-be clients."
"Datacube queries compute aggregates over database relations at a variety of granularities, and they constitute an important class of decision support queries. Real-world data is frequently sparse, and hence efficiently computing datacubes over large sparse relations is important. We show that current techniques for computing datacubes over sparse relations do not scale well with the number of CUBE BY attributes, especially when the relation is much larger than main memory. We propose a novel algorithm for the fast computation of datacubes over sparse relations, and demonstrate the efficiency of our algorithm using synthetic, benchmark and real-world data sets. When the relation fits in memory, our technique performs multiple in-memory sorts, and does not incur any I/O beyond the input of the relation and the output of the datacube itself. When the relation does not fit in memory, a divideand-conquer strategy divides the problem of computing the datacube into several simpler computations of sub-datacubes. Often, all but one of the sub-datacubes can be computed in memory and our in-memory solution applies. In that case, the total I/O overhead is linear in the number of CUBE BY attributes. We demonstrate with an implementation that the CPU cost of our algorithm is dominated by the I/O cost for sparse relations. ¡®The research of Kenneth A."
"XML is becoming the universal format for data exchange between applications. Recently, the emergence of Web services as standard means of publishing and accessing data on the Web introduced a new class of XML documents, which we call intensional documents. These are XML documents where some of the data is given explicitly while other parts are defined only intensionally by means of embedded calls to Web services.When such documents are exchanged between applications, one has the choice of whether or not to materialize the intensional data (i.e., to invoke the embedded calls) before the document is sent. This choice may be influenced by various parameters, such as performance and security considerations. This article addresses the problem of guiding this materialization process.We argue that---like for regular XML data---schemas (¨¤ la DTD and XML Schema) can be used to control the exchange of intensional data and, in particular, to determine which data should be materialized before sending a document, and which should not. We formalize the problem and provide algorithms to solve it. We also present an implementation that complies with real-life standards for XML data, schemas, and Web services, and is used in the Active XML system. We illustrate the usefulness of this approach through a real-life application for peer-to-peer news exchange."
"We investigate the problem of incremental maintenance of an SQL view in the face of database updates, and show that it is possible to reduce the total time cost of view maintenance by materializing (and maintaining) additional views. We formulate the problem of determining the optimal set of additional views to materialize as an optimization problem over the space of possible view sets (which includes the empty set). The optimization problem is harder than query optimization since it has to deal with multiple view sets, updates of multiple relations, and multiple ways of maintaining each view set for each updated relation.We develop a memoing solution for the problem; the solution can be implemented using the expression DAG representation used in rule-based optimizers such as Volcano. We demonstrate that global optimization cannot, in general, be achieved by locally optimizing each materialized subview, because common subexpressions between different materialized subviews can allow nonoptimal local plans to be combined into an optimal global plan. We identify conditions on materialized subviews in the expression DAG when local optimization is possible. Finally, we suggest heuristics that can be used to efficiently determine a useful set of additional views to materialize.Our results are particularly important for the efficient checking of assertions (complex integrity constraints) in the SQL-92 standard, since the incremental checking of such integrity constraints is known to be essentially equivalent to the view maintenance problem."
"RTMonitor is a real-time data management system for traffic navigation applications. In our system, mobile vehicles initiate time-constrained navigation requests and RTMonitor calculates and communicates the best paths for the clients based on the road network and real-time traffic data. The correctness of the suggested routes highly depends on how well the system can maintain temporal consistency of the traffic data. To minimize the overheads of maintaining the real-time data, RTMonitor adopts a cooperative and distributed approach using mobile agents which can greatly reduce the amount of communications and improves the scalability of the system. To minimize the space and message overheads, we have designed a two-level traffic graph scheme to organize the real-time traffic data to support navigation requests. In the framework, the agents use an Adaptive PUSH OR PULL (APoP) scheme to maintain the temporal consistency of the traffic data. Our experiments using synthetic traffic data show that RTMonitor can provide efficient support to serve navigation requests in a timely fashion. Although several agents may be needed to serve a request, the size of each agent is very small (only a few kilobytes) and the resulting communication and processing overheads for data monitoring can be maintained within a reasonable level."
"For several years now, you've been hearing and reading about an emerging standard that everybody has been calling SQL3. Intended as a major enhancement of the current second generation SQL standard, commonly called SQL-92 because of the year it was published, SQL3 was originally planned to be issued in about 1996¡­but things didn't go as planned."
"Structured documents (e.g., SGML) can benefit a lot from database support and more specifically from object-oriented database (OODB) management systems. This paper describes a natural mapping from SGML documents into OODB's and a formal extension of two OODB query languages (one SQL-like and the other calculus) in order to deal with SGML document retrieval."
"Ranking queries produce results that are ordered on some computed score. Typically, these queries involve joins, where users are usually interested only in the top-k join results. Current relational query processors do not handle ranking queries efficiently, especially when joins are involved. In this paper, we address supporting top-k join queries in relational query processors. We introduce a new rank-join algorithm that makes use of the individual orders of its inputs to produce join results ordered on a user-specified scoring function. The idea is to rank the join results progressively during the join operation. We introduce two physical query operators based on variants of ripple join that implement the rank-join algorithm. The operators are nonblocking and can be integrated into pipelined execution plans. We address several practical issues and optimization heuristics to integrate the new join operators in practical query processors. We implement the new operators inside a prototype database engine based on PREDATOR. The experimental evaluation of our approach compares recent algorithms for joining ranked inputs and shows superior performance."
"Complex similarity queries, i.e., multi-feature multi-object queries, are needed to express the information need of a user against a large multimedia repository. Even if a user initially issues a single-object query over one feature, a system with relevance feedback will automatically generate a complex similarity query. Relevance feedback is only useful if response times are interactive. Therefore, this article contributes to the important problem how to evaluate such complex queries efficiently. We describe a new evaluation technique called Generalized VA-File-based Search (GeVAS). It builds on the VA-File [27], supports queries over several feature types, and borrows the idea to search an index structure with several query objects in parallel from Ciaccia et al. [8]. Our main contributions are twofold: 1) we show that GeVAS does not degenerate for queries with many objects or many feature types. 2) We develop a number of variants of GeVAS, tailored to the different distance measures and distancecombining functions, and we show that they yield a significant performance improvement."
"1. Motivation Internet search engines have popularized keyword based search. While relational database systems offer powerfifl structured query languages such as SQL, there is no support for keyword search over databases. The simplicity of keyword search as a querying paradigm offers compelling values for data exploration. Specifically, keyword search does not require a priori knowledge of the schema. The above is significant as much information in a corporation is increasingly being available at its intranet. However, it is unrealistic to expect users who would browse and query such information to have detailed knowledge of the schema of available databases. Therefore, just as keyword search and classification hierarchies complement each other for document search, keyword search over databases can be effective."
"The proliferation of text databases within large organizations and on the Internet makes it difficult for a person to know which databases to search. Given language models that describe the contents of each database, a database selection algorithm such as GIOSS can provide assistance by automatically selecting appropriate databases for an information need. Current practice is that each database provides its language model upon request, but this cooperative approach has important limitations."
"We are interested in defining and querying views in a huge and highly heterogeneous XML repository (Web scale). In this context, view definitions are very large, involving lots of sources, and there is no apparent limitation to their size. This raises interesting problems that we address in the paper: (i) how to distribute views over several machines without having a negative impact on the query translation process; (ii) how to quickly select the relevant part of a view given a query; (iii) how to minimize the cost of communicating potentially large queries to the machines where they will be evaluated. The solution that we propose is based on a simple view definition language that allows for automatic generation of views. The language maps paths in the view abstract DTD to paths in the concrete source DTDs. It enables a distributed implementation of the view system that is scalable both in terms of data and load. In particular, the query translation algorithm is shown to have a good (linear) complexity."
"Web services are a consolidated reality of the modern Web with tremendous, increasing impact on everyday computing tasks. They turned the Web into the largest, most accepted, and most vivid distributed computing platform ever. Yet, the use and integration of Web services into composite services or applications, which is a highly sensible and conceptually non-trivial task, is still not unleashing its full magnitude of power. A consolidated analysis framework that advances the fundamental understanding of Web service composition building blocks in terms of concepts, models, languages, productivity support techniques, and tools is required. This framework is necessary to enable effective exploration, understanding, assessing, comparing, and selecting service composition models, languages, techniques, platforms, and tools. This article establishes such a framework and reviews the state of the art in service composition from an unprecedented, holistic perspective."
"In this demonstration, we present a prototype peer-topeer (P2P) application called PeerDB[2] that provides database capabilities. This system has been developed at the National University of Singapore in collaboration with Fudan University, and is being enhanced with more features and applications. The concept behind PeerDB is similar to the analogy of publishing personal web sites, except that it is now applied to personal databases. Unlike personal web sites which are usually hosted together in a central web server, personal databases are stored in the person¡¯s own PC. In addition, it is increasingly common for people to keep their data in common personal DBMS like MySQL, and MSAccess. Therefore, a PeerDB node allows an user to index and publish his/her personal database for other peers to query. PeerDB builds on and extends BestPeer [1] for DBMS applications. Briefly, BestPeer is a generic P2P system designed to serve as a platform to develop P2P applications easily and efficiently. It has the following features: (1) It employs mobile agents; (2) It shares data at a finer granularity as well as computational power; (3) It can dynamically reconfigure the BestPeer network so that a node is always directly connected to peers that provide the best service; (4) It employs a set of location independent global name lookup (LIGLO) servers to uniquely recognize nodes whose IP addresses may change as a result. In the PeerDB network, a set of PeerDB nodes communicate or share resources with each other. Each node comprises four components that are loosely integrated: (a) a data management system (we used MySQL in our implementation) that facilitates storage, manipulation and retrieval of the data at the node, and the associated local and export dictionaries that reflect the meta-data (schema and keywords); (b) a database agent system called DBAgent that provides the environment for mobile agents to operate on; (c) a cache manager for managing remote meta-data and data in secondary storage; and (d) a user-friendly user interface. PeerDB has several distinguishing features. First, it allows users to query data without knowing the schema of data in other nodes."
"The addition of stringent security specifications to the list of requirements for an application poses many new problems in DBMS design and implementation, as well as database design, use, and maintenance. Tight security requirements, such as those that result in silent masking of witholding of true information from a user or the introduction of false information into query answers, also raise fundamental questions about the meaning of the database and the semantics of accompanying query languages. In this paper, we propose a belief-based semantics for secure databases, which provides a semantics for databases that can ¡°lie¡± about the state of the world, or about their knowledge about the state of the world, in order to preserve security. This kind of semantics can be  used as a helpful retrofit for the proposals for a ¡°multilevel secure¡± database model (a particularly stringent form of security), and may be useful for less restrictive security policies as well. We also propose a family of query languages for multilevel secure relational database applications, and base the semantics of those languages on our semantics for secure databases. Our query languages are free of the semantic problems associated with use of ordinary SQL in a multilevel secure context, and should be easy for users to understand and employ."
"Semantic data is an integral component for search engines that provide answers beyond simple keyword-based matches. Resource Description Framework (RDF) provides a standardized and flexible graph model for representing semantic data. The astronomical growth of RDF data raises the need for scalable RDF management strategies. Although cloud-based systems provide a rich platform for managing large-scale RDF data, the shared storage provided by these systems introduces several performance challenges, e.g., disk I/O and network shuffling overhead. This paper investigates SPARTI, a scalable RDF data management system. In SPARTI, the partitioning of the data is based on the join patterns found in the query workload. Initially, SPARTI vertically partitions the RDF data, and then incrementally updates the partitioning according to the workload, which improves the query performance of frequent join patterns. SPARTI utilizes a partitioning schema, termed SemVP, that enables the system to read a reduced set of rows instead of entire partitions. SPARTI proposes a budgeting mechanism with a cost model to determine the worthiness of partitioning. Using real and synthetic datasets, SPARTI is compared against a Spark-based state-of-the-art system and is shown to execute queries around half the time over all query shapes while maintaining around an order of magnitude enhancement in storage requirements."
"Rapid advances in networking and Internet technologies have fueled the emergence of the ""software as a service"" model for enterprise computing. Successful examples of commercially viable software services include rent-a-spreadsheet, electronic mail services, general storage services, disaster protection services. ""Database as a Service"" model provides users power to create, store, modify, and retrieve data from anywhere in the world, as long as they have access to the Internet. It introduces several challenges, an important issue being data privacy. It is in this context that we specifically address the issue of data privacy.There are two main privacy issues. First, the owner of the data needs to be assured that the data stored on the service-provider site is protected against data thefts from outsiders. Second, data needs to be protected even from the service providers, if the providers themselves cannot be trusted. In this paper, we focus on the second challenge. Specifically, we explore techniques to execute SQL queries over encrypted data. Our strategy is to process as much of the query as possible at the service providers' site, without having to decrypt the data. Decryption and the remainder of the query processing are performed at the client site. The paper explores an algebraic framework to split the query to minimize the computation at the client site. Results of experiments validating our approach are also presented."
"Abstract.We consider the problems of computing aggregation queries in temporal databases and of maintaining materialized temporal aggregate views efficiently. The latter problem is particularly challenging since a single data update can cause aggregate results to change over the entire time line. We introduce a new index structure called the SB-tree, which incorporates features from both segment-trees and B-trees. SB-trees support fast lookup of aggregate results based on time and can be maintained efficiently when the data change. We extend the basic SB-tree index to handle cumulative (also called moving-window) aggregates, considering separatelycases when the window size is or is not fixed in advance. For materialized aggregate views in a temporal database or warehouse, we propose building and maintaining SB-tree indices instead of the views themselves."
"Support for virtual states and deltas between them is useful for a variety of database applications, including hypothetical database access, version management, simulation, and active databases. The Heraclitus paradigm elevates delta values to be ""first-class citizens"" in database programming languages, so that they can be explicitly created, accessed and manipulated.A fundamental issue concerns the trade-off between the ""accuracy"" or ""robustness"" of a form of delta representation, and the ease of access and manipulation of that form. At one end of the spectrum, code-blocks could be used to represent delta values, resulting in a more accurate capture of the intended meaning of a proposed update, at the cost of more expensive access and manipulation. In the context of object-oriented databases, another point on the spectrum is ""attribute-granularity"" deltas which store the net changes to each modified attribute value of modified objects.This paper introduces a comprehensive framework for specifying a broad array of forms for representing deltas for complex value types (tuple, set, bag, list, o-set and dictionary). In general, the granularity of such deltas can be arbitrarily deep within the complex value structure. Applications of this framework in connection with hypothetical access to, and ""merging"" of, proposed updates are discussed."
"Empowering users to access databases using simple keywords can relieve the users from the steep learning curve of mastering a structured query language and understanding complex and possibly fast evolving data schemas. In this tutorial, we give an overview of the state-of-the-art techniques for supporting keyword search on structured and semi-structured data, including query result definition, ranking functions, result generation and top-k query processing, snippet generation, result clustering, query cleaning, performance optimization, and search quality evaluation. Various data models will be discussed, including relational data, XML data, graph-structured data, data streams, and workflows. We also discuss applications that are built upon keyword search, such as keyword based database selection, query generation, and analytical processing. Finally we identify the challenges and opportunities of future research to advance the field."
"The Teradata Multimedia Object Manager is a general-purpose content analysis multimedia server designed for symmetric multiprocessing and massively parallel processing environments. The Multimedia Object Manager defines and manipulates user-defined functions (UDFs), which are invoked in parallel to analyze or manipulate the contents of multimedia objects. Several computationally intensive applications of this technology, which use large persistent datasets, include fingerprint matching, signature verification, face recognition, and speech recognition/translation."
"Active database systems support mechanisms that enable them to respond automatically to events that are taking place either inside or outside the database system itself. Considerable effort has been directed towards improving understanding of such systems in recent years, and many different proposals have been made and applications suggested. This high level of activity has not yielded a single agreed-upon standard approach to the integration of active functionality with conventional database systems, but has led to improved understanding of active behavior description languages, execution models, and architectures. This survey presents the fundamental characteristics of active database systems, describes a collection of representative systems within a common framework, considers  the consequences for implementations of certain design decisions, and discusses tools for developing active applications."
"Currently gene expression data are being produced at a phenomenal rate. The general objective is to try to gain a better understanding of the functions of cellular tissues. In particular, one specific goal is to relate gene expression to cancer diagnosis, prognosis and treatment. However, a key obstacle is that the availability of analysis tools or lack thereof, impedes the use of the data, making it difficult for cancer researchers to perform analysis efficiently and effectively."
"Previous OnLine DSA server versions have demonstrated the effectiveness of the high performance Parallel Data Query (PDQ) technology on SMP systems. The key components of PDQ are multi-threaded process grOUpSi table partitioning, pipelined hash-partitioned operators, light access methods, and parallel resource management OnLine XPS extends that core PDQ technology from SMP systems to massively parallel clusters of SMp or uniprocessor systems. Further, OnLine XPS leverages the inherent fault tolerant ¡­"
"Temporal, spatial and spatiotemporal queries are inherently multidimensional, combining predicates on explicit attributes with predicates on time dimension(s) and spatial dimension(s). Much confusion has prevailed in the literature on access methods because no consistent notation exists for referring to such queries. As a contribution towards eliminating this problem, we propose a new and simple notation for spatiotemporal queries. The notation aims to address the selection-based spatiotemporal queries commonly studied in the literature of access methods. The notation is extensible and can be applied to more general multidimensional, selection-based queries."
"From about the mid-1980' s to the mid-1990' s there was a flurry of research activity in the area of database triggers and constraints, seeing the development of numerous research proposals and prototypes. Soon thereafter, most mainstream database products ramped up their support for constraints and triggers, with expressive constraint specifications appearing in the SQL-92 standard, and both constraints and triggers in the SQL-99 standard."
"Data mining on large data warehouses is becoming increasingly important. In support of this trend, we consider a spectrum of architectural alternatives for coupling mining with database systems. These alternatives include: loose-coupling through a SQL cursor interface; encapsulation of a mining algorithm in a stored procedure; caching the data to a file system on-the-fly and mining; tight-coupling using primarily user-defined functions; and SQL implementations for processing in the DBMS. We comprehensively study the option of expressing the mining algorithm in the form of SQL queries using Association rule mining as a case in point. We consider four options in SQL-92 and six options in SQL enhanced with object-relational extensions (SQL-OR). Our evaluation of the different architectural alternatives shows that from a performance perspective, the Cache-Mine option is superior, although the performance of the SQL-OR option is within a factor of two. Both the Cache-Mine and the SQL-OR approaches incur a higher storage penalty than the loose-coupling approach which performance-wise is a factor of 3 to 4 worse than Cache-Mine. The SQL-92 implementations were too slow to qualify as a competitive option. We also compare these alternatives on the basis of qualitative factors like automatic parallelization, development ease, portability and inter-operability."
"Many commercial database systems maintain histograms to summarize the contents of relations and permit efficient estimation of query result sizes and access plan costs. Although several types of histograms have been proposed in the past, there has never been a systematic study of all histogram aspects, the available choices for each aspect, and the impact of such choices on histogram effectiveness. In this paper, we provide a taxonomy of histograms that captures all previously proposed histogram types and indicates many new possibilities. We introduce novel choices for several of the taxonomy dimensions, and derive new histogram types by combining choices in effective ways. We also show how sampling techniques can be used to reduce the cost of histogram construction. Finally, we present results from an empirical study of the proposed histogram types used in selectivity estimation of range predicates and identify the histogram types that have the best overall performance."
"This technical note shows how to combine some well-known techniques to create a method that will efficiently execute common multi-table joins. We concentrate on a commonly occurring type of join known as a star-join, although the method presented will generalize to any type of multi-table join. A star-join consists of a central detail table with large cardinality, such as an orders table (where an order row contains a single purchase) with foreign keys that join to descriptive tables, such as customers, products, and (sales) agents. The method presented in this note uses join indices with compressed bitmap representations, which allow predicates restricting columns of descriptive tables to determine an answer set (or foundset) in the central detail table; the method uses different predicates on different descriptive tables in combination to restrict the detail table through compressed bitmap representations of join indices, and easily completes the join of the fully restricted detail table rows back to the descriptive tables. We outline realistic examples where the combination of these techniques yields substantial performance improvements over alternative, more traditional query evaluation plans."
"Hyper-programming is a technology only available in persistent systems, since hyper-program source code contains both text and links to persistent objects. A hyper-programming system has already been prototyped in the persistent programming language Napier88. Here we report on the transfer of that technology to an object-oriented platform, Java. The component technologies required for hyperprogramming include linguistic reflection, a persistent store, and a browsing mechanism, all of which have been reported elsewhere. The topics of discussion here are the additional technologies of: the specification of denotable hyper-links in Java; a mechanism for preserving hyper-links over compilation; a hyper-program editor; and the integration of the editor and the browser with the hyper-programming user interface. We describe their design and implementation. In total, these technologies constitute a hyper-programming system in Java."
"XML is becoming the most relevant new standard for data representation and exchange on the WWW. Novel languages for extracting and restructuring the XML content have been proposed, some in the tradition of database query languages (i.e. SQL, OQL), others more closely inspired by XML. No standard for XML query language has yet been decided, but the discussion is ongoing within the World Wide Web Consortium and within many academic institutions and Internet-related major companies. We present a comparison of five, representative query languages for XML, highlighting their common features and differences."
"We witness a rapid increase in the number of structured information sources that are available online, especially on the WWW. These sources include commercial databases on product information, stock market information, real estate, automobiles, and entertainment. We would like to use the data stored in these databases to answer complex queries that go beyond keyword searches. We face the following challenges: (1) Several information sources store interrelated data, and any query-answering system must understand the relationships between their contents. (2) Many sources are not full-featured database systems and can answer only a small set of queries over their data (for example, forms on the WWW restrict the set of queries one can (3) Since the number of sources is very large, effective techniques are needed to prune the set of information sources accessed to answer a query. (4) The details of interacting with each source vary greatly. We describe the Information Manifold, an implemented system that provides uniform access to a heterogeneous collection of more than 100 information sources, many of them on the WWW. IM tackles the above problems by providing a mechanism to describe declaratively the contents and query capabilities of available information sources. There is a clean separation between the declarative source description and the actual details of interacting with an information source. We describe algorithms that use the source descriptions to prune effciently the set of information sources for a given query and practical algorithms to generate executable query plans. The query plans we generate can inolve querying several information sources and combining their answers. We also present experimental studies that indicate that the architecture and algorithms used in the Information Manifold scale up well to several hundred information sources"
"Any auxiliary structure, such as a bitmap or a B+-tree index, that refers to rows of a table stored as a primary B+-tree (e.g., tables with clustered index in Microsoft SQL Server, or index-organized tables in Oracle) by their physical addresses would require updates due to inherent volatility of those addresses. To address this problem, we propose a mapping mechanism that 1) introduces a single mapping table, with each row holding one key value from the primary B+-tree, as an intermediate structure between the primary B+-tree and the associated auxiliary structures, and 2) augments the primary B+-tree structure to include in each row the physical address of the corresponding mapping table row. The mapping table row addresses can then be used in the auxiliary structures to indirectly refer to the primary B+-tree rows. The two key benefits are: 1) the mapping table shields the auxiliary structures from the volatility of the primary B+-tree row addresses, and 2) the method allows reuse of existing conventional table mechanisms for supporting auxiliary structures on primary B+-trees. The mapping mechanism is used for supporting bitmap indexes on index-organized tables in Oracle9i. The analytical and experimental studies show that the method is storage efficient, and (despite the mapping table overhead) provides performance benefits that are similar to those provided by bitmap indexes implemented on conventional tables."
"In this paper, we propose an efficient direct and indirect file transfer protocol (C2CFTP) that transfers files between clients in a client-server system. Existing file transfer methods use an indirect transfer method through a server to transfer files between sending and receiving clients or a direct transfer method that connects a direct data channel between clients. However, in the case of indirect transmission, unnecessary file input/output (I/O) is required by the server, and in the case of direct transmission, a problem arises in that the file transmission delay time is increased due to channel management cost. "
"There are two key motivations for this work. First, the implementation of object-oriented databases has grown to a significant number. Second, there has been a need for integrated access of information from multiple data sources. The multidatabase system has been proposed as a solution for integrated access of data from multiple distributed, heterogeneous, and autonomous database systems. To present a single database illusion to its users, a multidatabase system maintains a single global database schema, which is the integration of all component database schemas and against which its users will issue queries and updates. Many approaches to schema integration have been proposed in the literature. Most of the previous approaches are concerned with relational databases. In this paper, we propose an approach to the integration of database schemas between object-oriented databases in a multidatabase system environment. The underlying principle of our approach is to facilitate the automation of the schema integration process."
"This paper presents an innovative partitionbased time join strategy for temporal databases where time is represented by time intervals. The proposed method maps time intervals to points in a two dimensional space and partitions the space into subspaces. Tupies of a temporal relation are clustered into partitions based on the mapping in the space. As a result, when two temporal relations are to be joined over the time attribute, a partition in one relation only needs to be compared with a predetermined set of partitions of the other relation. The mapping scheme and the join algorithms are described. The use of spatial indexing techniques to support direct access to the stored partitions is discussed. The results of a preliminary performance study indicate the efficiency of the proposed method."
"In addition to facilitating querying over the Web, XML query languages may provide high level constructs for useful facilities in traditional DBMSs that do not currently exist. In particular, current DBMS query languages do not allow querying across database object types to yield heterogeneous results. This paper motivates the usefulness of heterogeneous querying in traditional DBMSs and investigates XQuery, an emerging standard for XML query languages, to express such queries. The usefulness of querying and storing heterogeneous types is also applied to XML data within a Web information system."
"We present a new family of join algorithms, called ripple joins, for online processing of multi-table aggregation queries in a relational database management system (DBMS). Such queries arise naturally in interactive exploratory decision-support applications."
This paper presents a number of new techniques for parallelizing geo-spatial database systems and discusses their implementation in the Paradise object-relational database system. The effectiveness of these techniques is demonstrated using a variety of complex geo-spatial queries over a 120 GB global geo-spatial data set.
"Extended transaction model (ETM) is a powerful mechanism to ensure the consistency and reliability of complicated enterprise applications. However, there is few implementation of ETM in J2EE. The existing research is deficient in supporting range and requires some special database supporting. This paper explores the obstacle which prevents J2EE from supporting ETMs, and argues it is because of the limitation of J2EE XAResource interface and underlying databases. To overcome the obstacle, we propose a new approach, which processes concurrency control inside J2EE application server instead of in database. Furthermore, we implement TX/E service in JBoss to validate the approach, which is an enhanced J2EE transaction service supporting extended transaction models. Compared to existing work, TX/E supports user-defined transaction models and does not require any special database supporting."
"Response time is a key differentiation among electronic commerce (e-commerce) applications. For many e-commerce applications, Web pages are created dynamically based on the current state of a business stored in database systems. Recently, the topic of Web acceleration for database-driven Web applications has drawn a lot of attention in both the research community and commercial arena. In this paper, we analyze the factors that have impacts on the performance and scalability of Web applications. We discuss system architecture issues and describe approaches to deploying caching solutions for accelerating Web applications. We give the performance matrix measurement for network latency and various system architectures. The paper is summarized with a road map for creating high performance Web applications."
"Several unifications that the application development process has long needed are now occurring, due to developments in object technologies and standards. These will (gradually) change the way data intensive applications are developed, reduce databases' prominence in this process, and change data administration's goals and participants. At the same time, the database community needs to ensure that its experiences are leveraged and its concerns are met within the new methodologies and toolsets. We discuss these issues, and illustrate how they apply to a portion of the Department of Defense (DOD). We also examine things that object technology won't accomplish, and identify research problems whose solution would enable further progress."
"Elasticity is highly desirable for stream systems to guarantee low latency against workload dynamics, such as surges in arrival rate and fluctuations in data distribution. Existing systems achieve elasticity using a resource-centric approach that repartitions keys across the parallel instances, i.e., executors, to balance the workload and scale operators. However, such operator-level repartitioning requires global synchronization and prohibits rapid elasticity. We propose an executor-centric approach that avoids operator-level key repartitioning and implements executors as the building blocks of elasticity. By this new approach, we design the Elasticutor framework with two level of optimizations: i) a novel implementation of executors, i.e., elastic executors, that perform elastic multi-core execution via efficient intra-executor load balancing and executor scaling and ii) a global model-based scheduler that dynamically allocates CPU cores to executors based on the instantaneous workloads. We implemented a prototype of Elasticutor and conducted extensive experiments. We show that Elasticutor doubles the throughput and achieves up to two orders of magnitude lower latency than previous methods for dynamic workloads of real-world applications."
"Over the last few years, Oracle has evolved its flagship relational database system into an Object-Relational system by adding an extensible type system, object storage, an object cache, an extensible query and indexing framework, support for multimedia datatypes, a server-based scalable Java virtual machine, as well as enhancing its SQL DDL and DML language. These extensions were done with the practical goal of bringing objects to mainstream use."
"Despite its hasty claim, it is NOT a ¡°standard¡±. Rather, it is a work-in-progress proposal for an object-oriented database language and language bindings to it for C++ and Smalltalk. ODMG (Object-Oriented Database Management Group) is not a formal ¡°standards¡± body. It is a committee formed by five vendors of first-generation object-oriented database systems (OODB). (For several years, some of these vendors have offered products that are not much more than persistent storage managers for object-oriented programming languages, but the misleading label ¡°Object-Oriented Database System¡± has been stuck on such products in the market.) And now the misleading label ¡°standard¡± seems to be attached to the ODMG-93 work-in-progress proposals."
"We present an elegant technique to reduce inheritance and encapsulation to pure deduction. The reduction technique presented in this paper makes it possible to model object-oriented database features in a purely deductive system. Encapsulation has been given a formal treatment for the first time by introducing the so called conteztresolution scheme. The completion technique presented in this paper elegantly tackles inheritance with overriding and conflict resolution by avoiding non-monotonic reasoning. We show that the completion based reduction technique is robust and appealing compared to any other known rewriting based approaches. We propose an objectoriented front-end language called the Datalog+¡®, and discuss a rewriting scheme to the acclaimed Datalogneg for this language that exploits the context resolution and completion techniques presented here. We claim that our approach outperforms other known approaches in the literature in terms of its modeling capabilities and efficiency. Unlike most others, an implementation based on our reduction technique does not require metainterpretation and consequently readily exploits the rich set of optimization techniques available in Datalogneg"
"As WWW becomes more and more popular and powerful, how to search information on the web in database way becomes an important research topic. COMMIX, which is developed in the DB group in Peking University (China), is a system towards building very large database using data from the Web for information extraction, integration and query answering. COMMIX has some innovative features, such as ontology-based wrapper generation, XML-based information integration, view-based query answering, and QBE-style XML query interface."
"Today the problem of semantic interoperability in information search on the Internet is solved mostly by means of centralization, both at a system and at a logical level. This approach has been successful to a certain extent. Peer-to-peer systems as a new brand of system architectures indicate that the principle of decentralization might offer new solutions to many problems that scale well to very large numbers of users.In this paper we outline how the peer-to-peer system architectures can be applied to tackle the problem of semantic interoperability in the large, driven in a bottom-up manner by the participating peers. Such a system can readily be used to study semantic interoperability as a global scale phenomenon taking place in a social network of information sharing peers."
"Building object-oriented applications which access relational data introduces a number of technical issues for developers who are making the transition to C++. We describe these issues and discuss how we have addressed them in Persistence, an application development tool that uses an automatic code generator to merge C++ applications with relational data. We use client-side caching to provide the application program with efficient access to the data."
"Oracle Materialized Views (MVs) are designed for data warehousing and replication. For data warehousing, MVs based on inner/outer equijoins with optional aggregation, can be refreshed on transaction boundaries, on demand, or periodically. Refreshes are optimized for bulk loads and can use a multi-MV scheduler. MVs based on subqueries on remote tables support bidirectional replication. Optimization with MVs includes transparent query rewrite based on costbased selection method. The ability to rewrite a large class of queries based on a small set of MVs is supported by using Dimensions (new Oracle object), losslessness of joins, functional dependency, column equivalence, join derivability, joinback and aggregate rollup."
"Object-oriented databases enforce behavioral schema consistency rules to guarantee type safety, i.e., that no run-time type error can occur. When the schema must evolve, some schema updates may violate these rules. In order to maintain complete behavioral schema consistency, traditional solutions require significant changes to the types, the type hierarchy and the code of existing methods. Such operations are very expensive in a database context. To ease schema evolution, we propose to support exceptions to the behavioral consistency rules without sacrificing type safety for all that. The basic idea is to detect unsafe statements at compile-time and check them at run-time. The run-time check is performed by a specific clause that is automatically inserted around unsafe statements. This check clause warns the programmer of the safety problem and lets him provide exception-handling code. Schema updates can therefore be performed with only minor changes to the code of methods."
"The 5th East European Conference ADBIS'2001 was organized by the Vilnius Gediminas Technical University, Institute of Mathematics and Informatics (Lithuania), Lithuanian Computer Society in cooperation with Moscow ACM SIGMOD Chapter and Law University of Lithuania in Vilnius, Lithuania, September 25-28, 2001. The call for papers attracted 82 submissions from 30 countries. The international program committee, consisting of 47 researchers from 21 countries, selected 25 papers for long presentations and 19 research communications for regular sessions. Additionally, 9 professional communications and reports have been selected for industrial sessions. The authors of accepted papers come from 29 countries, indicating the truly international recognition of the ADBIS conference series. The conference had 127 registered participants from 23 countries and included invited lectures, tutorials, regular sessions, and industrial sessions. This report describes the goals of the conference and summarizes the issues discussed during the sessions."
"Small Materialized Aggregates (SMAs for short) are considered a highly flexible and versatile alternative for materialized data cubes. The basic idea is to compute many aggregate values for small to medium-sized buckets of tuples. These aggregates are then used to speed up query processing. We present the general idea and present an application of SMAs to the TPC-D benchmark. We show that application of SMAs to TPC-D Query 1 results in a speed up of two orders of magnitude. Then, we elaborate on the problem of query processing in the presence of SMAs. Last, we briefly discuss some further tuning possibilities for SMAs."
"We propose a new dynamic method for multidimensional selectivity estimation for range queries that works accurately independent of data distribution. Good estimation of selectivity is important for query optimization and physical database design. Our method employs the multilevel grid file (MLGF) for accurate estimation of multidimensional data distribution. The MLGF is a dynamic, hierarchical, balanced, multidimensional file structure that gracefully adapts to nonuniform and correlated distributions. We show that the MLGF directory naturally represents a multidimensional data distribution. We then extend it for further refinement and present the selectivity estimation method based on the MLGF. Extensive experiments have been performed to test the accuracy of selectivity estimation. The results show that estimation errors are very small independent of distributions, even with correlated and/or highly skewed ones. Finally, we analyze the cause of errors in estimation and investigate the effects of various parameters on the accuracy of estimation."
"Query optimization is an integral part of relational database management systems. One important task in query optimization is selectivity estimation, that is, given a query P, we need to estimate the fraction of records in the database that satisfy P. Many commercial database systems maintain histograms to approximate the frequency distribution of values in the attributes of relations."
"The automatic extraction of information from unstructured sources has opened up new avenues for querying, organizing, and analyzing data by drawing upon the clean semantics of structured databases and the abundance of unstructured data. The field of information extraction has its genesis in the natural language processing community where the primary impetus came from competitions centered around the recognition of named entities like people names and organization from news articles. As society became more data oriented with easy online access to both structured and unstructured data, new applications of structure extraction came around. Now, there is interest in converting our personal desktops to structured databases, the knowledge in scientific publications to structured records, and harnessing the Internet for structured fact finding queries. Consequently, there are many different communities of researchers bringing in techniques from machine learning, databases, information retrieval, and computational linguistics for various aspects of the information extraction problem."
"Microsoft? TerraServer stores aerial, satellite, and topographic images of the earth in a SQL database available via the Internet. It is the world's largest online atlas, combining eight terabytes of image data from the United States Geological Survey (USGS) and SPIN-2. Internet browsers provide intuitive spatial and text interfaces to the data. Users need no special hardware, software, or knowledge to locate and browse imagery. This paper describes how terabytes of ¡°Internet unfriendly¡± geo-spatial images were scrubbed and edited into hundreds of millions of ¡°Internet friendly¡± image tiles and loaded into a SQL data warehouse. All meta-data and imagery are stored in the SQL database."
"The physical performance of the Oracle RAC hardware architecture directly affects Oracle's output performance. In this paper, we perform performance tests on three Oracle RAC hardware architectures, and the test data is simulated using real teaching management system data on campus. The simulation results show that the two new oracle RAC hardware architectures are respectively occupied by the TPM and IOPS indicators, and the overall is stronger than the traditional external storage architecture. "
"Users often can not easily express their queries. For example, in a multimedia/image by content setting, the user might want photographs with sunsets; in current systems, like QBIC, the user has to give a sample query, and to specify the relative importance of color, shape and texture. Even worse, the user might want correlations between attributes, like, for example, in a traditional, medical record database, a medical researcher might want to find ¡°mildly overweight patients¡±, where the implied query would be ¡°weight/height M 4 lb/inch¡±. Our goal is to provide a user-friendly, but theoretically solid method, to handle such queries. We allow the user to give several examples, and, optionally, their ¡®goodness¡¯ scores, and we propose a novel method to ¡°guess¡± which attributes are important, which correlations are important, and with what weight. Our contributions are twofold: (a) we formalize the problem as a minimization problem and show how to solve for the optimal solution, completely avoiding the ad-hoc heurist Part of this work was done while this author was vising University of Maryland and Carnegie Mellon University. Experiments on synthetic and real datasets show that our method estimates quickly and accurately the ¡®hidden¡¯ distance function in the user¡¯s mind."
"With the rapid growth of XML-document traffic on the Internet, scalable content-based dissemination of XML documents to a large, dynamic group of consumers has become an important research challenge. To indicate the type of content that they are interested in, data consumers typically specify their subscriptions using some XML pattern specification language (e.g., XPath). Given the large volume of subscribers, system scalability and efficiency mandate the ability to aggregate the set of consumer subscriptions to a smaller set of content specifications, so as to both reduce their storage-space requirements as well as speed up the document-subscription matching process. In this paper, we provide the first systematic study of subscription aggregation where subscriptions are specified with tree patterns (an important subclass of XPath expressions). The main challenge is to aggregate an input set of tree patterns into a smaller set of generalized tree patterns such that: (1) a given space constraint on the total size of the subscriptions is met, and (2) the loss in precision (due to aggregation) during document filtering is minimized. We propose an efficient tree-pattern aggregation algorithm that makes effective use of document-distribution statistics in order to compute a precise set of aggregate tree patterns within the allotted space budget. "
"Today's E-Commerce systems are a complex assembly of databases, web servers, home grown glue code, and networking services for security and scalability. The trend is towards larger pieces of these coming together in bundled offerings from leading software vendors, and the networking/hardware being offered through service delivery companies. In this paper we examine the bundle by looking in detail at IBM's WebSphere, Commerce Edition, and its deployment at a major customer site."
"Predicting query execution time is crucial for many database management tasks including admission control, query scheduling, and progress monitoring. While a number of recent papers have explored this problem, the bulk of the existing work either considers prediction for a single query, or prediction for a static workload of concurrent queries, where by ""static"" we mean that the queries to be run are fixed and known. In this paper, we consider the more general problem of dynamic concurrent workloads. Unlike most previous work on query execution time prediction, our proposed framework is based on analytic modeling rather than machine learning. We first use the optimizer's cost model to estimate the I/O and CPU requirements for each pipeline of each query in isolation, and then use a combination queueing model and buffer pool model that merges the I/O and CPU requests from concurrent queries to predict running times. We compare the proposed approach with a machine-learning based approach that is a variant of previous work. Our experiments show that our analytic-model based approach can lead to competitive and often better prediction accuracy than its machine-learning based counterpart."
"Much of the work on conceptual modeling involves the use of an entity-relationship model in which binary relationships appear as associations between two entities. Relationships involving more than two entities are considered rare and, therefore, have not received adequate attention. This research provides a general framework for the analysis of relationships in which binary relationships simply become a special case. The framework helps a designer to identify ternary and other higher-degree relationships that are commonly represented, often inappropriately, as either entities or binary relationships. Generalized rules are also provided for representing higher-degree relationships in the relational model. This uniform treatment of relationships should significantly ease the burden on a designer by enabling him or her to extract more information from a real-world situation and represent it properly in a conceptual design."
"This article summarizes my recent job search that effectively began in the late fall of 2000 and ended in the early summer of 2001. The opinions I express here are largely based on what I experienced, heard and read from various sources, and should be taken as mere tips or suggestions for Ph.D. students who are soon to graduate and look for a position in a research-oriented academic institution.This is by no means a comprehensive guide to job searching: in limited space, I address only the issues that I deem more relevant or important, in an effort to provide information and insight that I believe is not readily available elsewhere. I do, however, try to provide pointers to (hopefully) complementary information throughout the text wherever appropriate and in Section 13.Figure 1 illustrates the typical timeline for the entire process, from pre-application to final decision, and the documents and activities required at each stage. The rest of the article briefly discusses each of these stages."
"Consider the problem of monitoring tens of thousands of time series data streams in an online fashion and making decisions based on them. In addition to single stream statistics such as average and standard deviation, we also want to find high correlations among all pairs of streams. A stock market trader might use such a tool to spot arbitrage opportunities. This paper proposes efficient methods for solving this problem based on Discrete Fourier Transforms and a three level time interval hierarchy. Extensive experiments on synthetic data and real world financial trading data show that our algorithm beats the direct computation approach by several orders of magnitude. It also improves on previous Fourier Transform approaches by allowing the efficient computation of time-delayed correlation over any size sliding window and any time delay. Correlation also lends itself to an efficient grid-based data structure."
"Conduct of scientific and engineering research is becoming critically dependent on effective management of scientific and engineering data and technical information. The rapid advances in scientific instrumentation, computer and communication technologies enable the scientists to collect, generate, process, and share unprecedented volumes of data. For example, the Earth Observing System Data and Information System (EOSDIS) has the task to manage the data from NASA¡¯s Earth science research satellites and field measurement programs, and other data essential for the interpretation of these measurements in support of global change research. Apart from being able to handle a stream of 1 terabyte of data daily by the year 2000, EOSDIS will also need to provide transparent access to heterogeneous data held in the archives of several US government agencies, organizations and countries. A single graphical user interface employing the Global Change Master Directory needs to help users locate data sets of interest among massive and diverse data sets, or find the appropriate data analysis tools, regardless of their location. Another major international effort in the area of human genome research faces some similar, as well as unique issues due to the complexity of the genome data, special querying requirements and much more heterogeneous collections of data. Scientific databases can be viewed as critical repositories of knowledge, both existing and yet to be dis-"
"We devise in this paper a regression-based algorithm, called algorithm FTP-DS (Frequent Temporal Patterns of Data Streams), to mine frequent temporal patterns for data streams. While providing a general framework of pattern frequency counting, algorithm FTP-DS has two major features, namely one data scan for online statistics collection and regression-based compact pattern representation.To attain the feature of one data scan, the data segmentation and the pattern growth scenarios are explored for the frequency counting purpose. Algorithm FTP-DS scans online transaction flows and generates candidate frequent patterns in real time. The second important feature of algorithm FTP-DS is on the regression-based compact pattern representation. Specifically, to meet the space constraint, we devise for pattern representation a compact ATF (standing for Accumulated Time and Frequency) form to aggregately comprise all the information required for regression analysis. In addition, we develop the techniques of the segmentation tuning and segment relaxation to enhance the functions of FTP-DS. With these features, algorithm FTP-DS is able to not only conduct mining with variable time intervals but also perform trend detection effectively. Synthetic data and a real dataset which contains net-Permission work alarm logs from a major telecommunication company are utilized to verify the feasibility of algorithm FTP-DS."
"Approximately every five years, a group of database researchers meet to do a self-assessment of our community, including reflections on our impact on the industry as well as challenges facing our research community. This report summarizes the discussion and conclusions of the 9th such meeting, held during October 9-10, 2018 in Seattle."
"XML has become ubiquitous, and XML data has to be managed in databases. The current industry standard is to map XML data into relational tables and store this information in a relational database. Such mappings create both expressive power problems and performance problems.In the TIMBER [7] project we are exploring the issues involved in storing XML in native format. We believe that the key intellectual contribution of this system is a comprehensive set-at-a-time query processing ability in a native XML store, with all the standard components of relational query processing, including algebraic rewriting and a cost-based optimizer."
"Spatial data mining is the discovery of interesting relationships and characteristics that may exist implicitly in spatial databases. In this paper, we explore whether clustering methods have a role to play in spatial data mining. To this end, we develop a new clustering method called CLAHANS which is based on randomized search. We also develop two spatial data mining algorithms that use CLAHANS. Our analysis and experiments show that with the assistance of CLAHANS, these two algorithms are very effective and can lead to discoveries that are difficult to find with current spatial data mining algorithms. Furthermore, experiments conducted to compare the performance of CLAHANS with that of existing clustering methods show that CLAHANS is the most efficient."
"This paper describes a parallel database load prototype for Digital's Rdb database product. The prototype takes a dataflow approach to database parallelism. It includes an explorer that discovers and records the cluster configuration in a database, a client CUI interface that gathers the load job description from the user and from the Rdb catalogs, and an optimizer that picks the best parallel execution plan and records it in a web data structure. The web describes the data operators, the dataflow rivers among them, the binding of operators to processes, processes to processors, and files to discs and tapes. This paper describes the optimizer's cost-based hierarchical optimization strategy in some detail. The prototype executes the web's plan by spawning a web manager process at each node of the cluster. The managers create the local executor processes, and orchestrate startup, phasing, checkpoint, and shutdown. The execution processes perform one or more operators. Data flows among the operators are via memory-to-memory streams within a node, and via web-manager multiplexed tcp/ip streams among nodes. The design of the transaction and checkpoint/restart mechanisms are also described. Preliminary measurements indicate that this design will give excellent scaleups."
"With t,ha exponential proliferation of databases and advances in wide area networking, interest, in worldwide dat,abase interoperability has gained momentum. Scalability and language support for this new environment remain open questSions. We propose a scheme where database nodes are dynamically clustered around current, areas of ibresl. Data sharing is then pursued, with any relationship informat8ion discovered being fed bac,k for reclustering. In order to achieve scalability, t,he proposed architect(ure sub-divides both the rrlntionship and illformntiorl spaces."
"A workflow consists of a collection of coordinated tasks designed to carry out a well-defined complex process, such as catalog ordering, trip planning, or a business process in an enterprise. Scheduling of workflows is a problem of finding a correct execution sequence for the workflow tasks, i.e., execution that obeys the constraints that embody the business logic of the workflow. Research on workflow scheduling has largely concentrated on temporal constraints, which specify correct ordering of tasks. Another important class of constraints -- those that arise from resource allocation -- has received relatively little attention in workflow modeling. Since typically resources are not limitless and cannot be shared, scheduling of a workflow execution involves decisions as to which resources to use and when. In this work, we present a framework for workflows whose correctness is given by a set of resource allocation constraints and develop techniques for scheduling such systems. Our framework integrates Concurrent Transaction Logic (CTR) with constraint logic programming (CLP), yielding a new logical formalism, which we call Concurrent Constraint Transaction Logic, or CCTR."
"The processing of spatial joins can be greatly improved by the use of filters that reduce the need for examining the exact geometry of polygons in order to find the intersecting ones. Approximations of candidate pairs of polygons are examined using such filters. As a result, three possible sets of answers are identified: the positive one, composed of intersecting polygon pairs; the negative one, composed of nonintersecting polygon pairs; and the inconclusive one, composed of the remaining pairs of candidates. To identify all the intersecting pairs of polygons with inconclusive answers, it is necessary to have access to the representation of polygons so that an exact geometry test can take place. This article presents a polygon approximation for spatial join processing which we call four-colors raster signature (4CRS). The performance of a filter using this approximation was evaluated with real world data sets. The results showed that our approach, when compared to other approaches presented in the related literature, reduced the inconclusive answers by a factor of more than two. As a result, the need for retrieving the representation of polygons and carrying out exact geometry tests is reduced by a factor of more than two, as well. A Raster Approximation for the Processing of Spatial Joins"
"Linkages among documents have a significant impact on the importance of documents, as it can be argued that important documents are pointed to by many documents or by other important documents. Metasearch engines can be used to facilitate ordinary users for retrieving information from multiple local sources (text databases). There is a search engine associated with each database. In a large-scale metasearch engine, the contents of each local database is represented by a representative. Each user query is evaluated against he set of representatives of all databases in order to determine the appropriate databases (search engines) to search (invoke) In previous word, the linkage information between documents has not been utilized in determining the appropriate databases to search. In this paper, such information is employed to determine the degree of relevance of a document with respect to a given query. Specifically, the importance (rank) of each document as determined by the linkages is integrated in each database representative to facilitate the selection of databases for each given query. We establish a necessary and sufficient condition to rank databases optimally, while incorporating the linkage information. A method is provided to estimate the desired quantities stated in the necessary and sufficient condition. The estimation method runs in time linearly proportional to the number of query terms. Experimental results are provided to demonstrate the high retrieval effectiveness of the method."
"The increasing ability to interconnect computers through internet-working, wireless networks, high-bandwidth satellite, and cable networks has spawned a new class of information-centered applications based on data dissemination. These applications employ broadcast to deliver data to very large client populations. We have proposed the Broadcast Disks paradigm [Zdon94, Acha95b] for organizing the contents of a data broadcast program and for managing client resources in response to such a program. Our previous work on Broadcast Disks focused exclusively on the ¡°push-based¡± approach, where data is sent out on the broadcast channel according to a periodic schedule, in anticipation of client requests. In this paper, we study how to augment the push-only model with a ¡°pull-based¡± approach of using a backchannel to allow clients to send explicit requests for data to the server. We analyze the scalability and performance of a broadcast-based system that integrates push and pull and study the impact of this integration on both the steady state and warm-up performance of clients. Our results show that a client backchannel can provide significant performance improvement in the broadcast environment, but that unconstrained use of the backchannel can result in scalability problems due to server saturation. We propose and investigate a set of three techniques that can delay the onset of saturation and thus, enhance the performance and scalability of the system."
"A variety of developments combine to highlight the need for respecting order when manipulating relations. For example, new functionality is being added to SQL to support OLAP-style querying in which order is frequently an important aspect. The set- or multiset-based frameworks for query optimization that are currently being taught to database students are increasingly inadequate.This paper presents a foundation for query optimization that extends existing frameworks to also capture ordering. A list-based relational algebra is provided along with three progressively stronger types of algebraic equivalences, concrete query transformation rules that obey the different equivalences, and a procedure for determining which types of transformation rules are applicable for optimizing a query. The exposition follows the style chosen by many textbooks, making it relatively easy to teach this material in continuation of the material covered in the textbooks, and to integrate this material into the textbooks."
"As we approach the next century, the software industry landscape is undergoing massive technology and business changes. The client/server revolution has barely reached its half-life and it is already being eclipsed by the Internet revolution. Software development is moving away from the direction of being labour-intensive. Customers are buying more pre-packaged software solutions or software components that can easily be assembled on site by in-house personnel or systems integrators. Except for a handful of players like Microsoft, Oracle and Computer Associates, very few leading software companies of the seventies and eighties have survived into the nineties. A whole new generation of software companies have emerged that are focussed on selling advanced¡¯ software components based on industry standards. For Indian software companies with superior technology development skills, the Internet will open up opportunities to build products that have never been built before and to enter global markets on a scale that was never attempted before."
"The dynamic load balancing strategies for parallel association rule mining are proposed under heterogeneous PC cluster environment. PC cluster is recently regarded as one of the most promising platforms for heavy data intensive applications, such as decision support query processing and data mining. The development period of PC hardware is becoming extremely short, which results in heterogeneous system, where the clock cycle of CPU, the performance/capacity of disk drives, etc are di erent among component PC's. Heterogeneity is inevitable. Basically, current algorithms assume the homogeneity. Thus if we naively apply them to heterogeneous system, its performance is far below expectation. We need some new methodologies to handle heterogeneity. In this paper, we propose the new dynamic load balancing methods for association rule mining, which works under heterogeneous system. Two strategies, called candidate migration and transaction migration are proposed. Initially rst one is invoked. When the load imbalance cannot be resolved with the rst method, the second one is employed, which is costly but more e ective for strong imbalance. We have implemented them on the PC cluster system with two di erent types of PCs: one with Pentium Pro, the other one with Pentium II. The experimental results confirm that the proposed approach can very e ectively balance the workload among heterogeneous PCs."
"This paper presents a simulation study of a video-on-demand system. We present video server algorithms for real-time disk scheduling, prefetching, and buffer pool management. The performance of these algorithms is compared against the performance of simpler algorithms such as elevator and round-robin disk scheduling and global LRU buffer pool management. Finally, we show that the SPIFFI video-on-demand system scales nearly linearly as the number of disks, videos, and terminals is increased."
"We propose a new Rtree structure that outperforms all the older ones. The heart of the idea is to facilitate the deferred splitting ap preach in R-trees. This is done by proposing an ordering on the R-tree nodes. This ordering has to be ¡®good¡¯, in the sense that it should group ¡®similar¡¯ data rectangles to gether, to minimize the area and perimeter of the resulting minimum bounding rectangles (MBRs). Following [KF93] we have chosen the so-called ¡®2D-c¡¯ method, which sorts rectangles according to the Hilbert value of the center of the rectangles. Given the ordering, every node has a well-defined set of sibling nodes; thus, we can use deferred splitting. By adjusting the split policy, the Hilbert R-tree can achieve as high utilization as desired. To the contrary, the R.-tree has no control over the space utilization, typically achieving up to 70%. We designed the manipulation algorithms in detail, and we did a full implementation of the *This resexch was partially fuuded by the hmtitutc for Systerm, FLsemch (ISR), by the National Science Foundation under Grants IF&9205273 and IFU-8958546 (PYI), with matching fuuds from EMPRESS Software Inc. und Think& h4achinen"
"Data intensive applications today usually run in either a clientserver or a middleware environment. In either case, they must efficiently handle both database queries, which process large numbers of data objects, and application logic, which involves fine-grained object accesses (e.g., method calls). Sophisticated optimization techniques speed up query processing, while caching is used to reduce the cost of the application logic. Query processing and caching decisions are typically made in isolation, though often in applications queries are used to identify those objects the application will further process. We propose a wholistic approach to speeding up such applications: we load the cache of a system with relevant objects as a byproduct of query processing. This can potentially improve the performance of the application, by eliminating the need to fault in objects. However, it can also increase the cost of queries by forcing them to handle more data, thus potentially reducing the performance of the application. In this paper, we examine both heuristic and cost-based strategies for deciding what to cache, and when to do so. We show how these strategies can be integrated into the query optimizer of an existing system, and how the caching architecture is affected. We present the results of experiments using the Garlic database middleware system; the experiments demonstrate the usefulness of loading a cache with query results and illustrate the tradeoffs between the cost-based and heuristic optimization methods."
"The analysis of business data is often an ill-defined task characterized by large amounts of noisy data. Because of this, business data analysis must combine two kinds of intertwined tasks: exploration and analysis. Exploration is the process of finding the appropriate subset of data to analyze, and analysis is the process of measuring the data to provide the business answer. While there are many tools available both for exploration and for analysis, a single tool or set of tools may not provide full support for these intertwined tasks. We report here on a project that set out to understand a specific business data analysis problem and build an environment to support it. The results of this understanding are, first of all, a detailed list of requirements of this task; second, a set of capabilities that meet these requirements; and third, an implemented client-server solution that addresses many of these requirements and identifies others for future work. Our solution incorporates several novel perspectives on data analysis and combines a history mechanism with a graphical, re-usable representation of the analysis and exploration process. Our approach emphasizes using the database itself to represent as many of these functions as possible."
"Recent years witnessed an increasing interest in researches in XML, partly due to the fact that XML has now become the de facto standard for data interchange over the internet. A large amount of work has been reported on XML storage models and query processing techniques. However, few works have addressed issues of XML query optimization. In this paper, we report our study on one of the challenges in XML query optimization: containment join size estimation. Containment join is well accepted as an important operation in XML query processing. Estimating the size of its results is no doubt essential to generate efficient XML query processing plans. We propose two models, the interval model and the position model, and a set of estimation methods based on these two models. Comprehensive performance studies were conducted. The results not only demonstrate the advantages of our new algorithms over existing algorithms, but also provide valuable insights into the tradeoff among various parameters."
"The W3C XML Scheme language is becomimg increasingly popular for expressing the data model for XML documents. It is a powerful language that incorporates both strutural and datatype modeling features. There are many benefits to storing XML Schema compliant data in a database system, including better queryability, optimied updates and stronger validation. However, the fidelity of the XML document cannot be sacrificed. Thus, the fundamental problem facing database implementers is: how can XML Schemes be mapped to relational (and object-relational) database without losing schema semantics or data-fidelity? In this paper, we present the Oracle XML DB solution for a flexible mapping of XML Schemas to object-relational database. It preserves document fidelity, including ordering, namespaces, comments, processing instructions etc., and handles all the XML Schema semantics including cyclic definitions, dervations (extension and restriction), and wildcards. We also discuss various query and update optimiations that involve rewriting XPath operations to directly operate on the underlying relational data."
"Dynamic queries constitute a very powerful mechanism for information visualization; some universe of data is visualized, and this visualization is modified on-the-fly as users modify the range of interest within the domains of the various attributes of the visualized information. In this paper, we analyze dynamic queries and offer some natural generalizations of the original concept by establishing a connection to SQL. We also discuss some implementation ideas that should make these generalizations efficient as well."
"We are witnessing a profound change in the global information infrastructure that has the potential to fundamentally impact many facets of our life. An important aspect of the evolving infrastructure is the seamless, ubiquitous wireless connectivity which engenders continuous interactions between people and interconnected computers. A challenging area of future ubiquitous wireless computing is the area of providing mobile users with integrated Personal Information Services and Applications (PISA). In this paper, a wireless client/server computing architecture will be discussed for the delivery of PISA. Data management issues such as transactional services and cache consistency will be examined under this architecture."
"We present an architecture and a set of challenges for peer database management systems. These systems team up to build a network of nodes (peers) that coordinate at run time most of the typical DBMS tasks such as the querying, updating, and sharing of data. Such a network works in a way similar to conventional multidatabases. Conventional multidatabase systems are founded on key concepts such as those of a global schema, central administrative authority, data integration, global access to multiple databases, permanent participation of databases, etc. Instead, our proposal assumes total absence of any central authority or control, no global schema, transient participation of peer databases, and constantly evolving coordination rules among databases. In this work, we describe the status of the Hyperion project, present our current solutions, and outline remaining research issues."
"The performance of main-memory index structures is increasingly determined by the number of CPU cache misses incurred when traversing the index. When keys are stored indirectly, as is standard in main-memory databases, the cost of key retrieval in terms of cache misses can dominate the cost of an index traversal. Yet it is inefficient in both time and space to store even moderate sized keys directly in index nodes. In this paper, we investigate the performance of tree structures suitable for OLTP workloads in the face of expensive cache misses and non-trivial key sizes. We propose two index structures, pkT-trees and pkB-trees, which significantly reduce cache misses by storing partial-key information in the index. We show that a small, fixed amount of key information allows most cache misses to be avoided, allowing for a simple node structure and efficient implementation. Finally, we study the performance and cache behavior of partial-key trees by comparing them with other main-memory tree structures for a wide variety of key sizes and key value distributions."
"The analysis of time series in financial and scientific applications requires database functionality with complex specialized modeling capabilities and at the same time an easy-to-use interface. We present the time series management system CALANDA which combines both, a powerful dedicated data model and an intuitive GUI. The focus of this paper and the demonstration is to show how CALANDA is accessed by end users."
"In this demo, we will show the implementation of a content-based SPatial Image Retrieval Engine (SPIRE) for multimodal unstructured data. This architecture provides a framework for retrieving multi-modal data including image, image sequence, time series and parametric data from large archives. Dramatic speedup (from a factor of 4 to 35) has been achieved for many search operations such as template matching, texture feature extraction. This framework has been applied and validated in solar flares and petroleum exploration in which spatial and spatial-temporal phenomena are located."
"We propose a new multi-attribute index. Our approach combines the hB-tree, a multi-attribute index, and the $\Pi$-tree, an abstract index which offers efficient concurrency and recovery methods. We call the resulting method the hB $^\Pi$-tree. We describe several versions of the hB $^\Pi$-tree, each using a different node-splitting and index-term-posting algorithm. We also describe a new node deletion algorithm. We have implemented all the versions of the hB $^\Pi$-tree. Our performance results show that even the version that offers no performance guarantees, actually performs very well in terms of storage utilization, index size (fan-out), exact-match and range searching, under various data types and distributions. We have also shown that our index is fairly insensitive to increases in dimension. Thus, it is suitable for indexing high-dimensional applications. This property and the fact that all our versions of the hB $^\Pi$-tree can use the $\Pi$-tree concurrency and recovery algorithms make the hB $^\Pi$-tree a promising candidate for inclusion in a general-purpose DBMS."
"Spatial data mining is the discovery of interesting relationships and characteristics that may exist implicitly in spatial databases. In this paper, we explore whether clustering methods have a role to play in spatial data mining. To this end, we develop a new clustering method called CLAHANS which is based on randomized search. We also develop two spatial data mining algorithms that use CLAHANS. Our analysis and experiments show that with the assistance of CLAHANS, these two algorithms are very effective and can lead to discoveries that are difficult to find with current spatial data mining algorithms. Furthermore, experiments conducted to compare the performance of CLAHANS with that of existing clustering methods show that CLAHANS is the most efficient."
"Currently, there is tremendous interest in providing ad-hoc mining capabilities in database management systems. As a first step towards this goal, in [15] we proposed an architecture for supporting constraint-based, human-centered, exploratory mining of various kinds of rules including associations, introduced the notion of constrained frequent set queries (CFQs), and developed effective pruning optimizations for CFQs with 1-variable (1-var) constraints."
"I describe the format of the new version of an introductory database course that I taught at the University ofWashington inWinter, 2003. The key idea underlying the course is to expose the students to some of the challenges that arise when working with and integrating data from multiple database systems and applications."
"IP network operators collect aggregate traffic statistics on network interfaces via the Simple Network Management Protocol (SNMP). This is part of routine network operations for most ISPs; it involves a large infrastructure with multiple network management stations polling information from all the network elements and collating a real time data feed. This demo will present a tool that manages the live SNMP data feed on a fully operational large ISP at industry scale. The tool primarily serves to study correlations in the network traffic, by providing a rich mix of ad-hoc querying based on a user-friendly correlation interface and as well as canned queries, based on the expertise of the network operators with field experience. The tool is called IPSOFACTO for IP Stream-Oriented FAst Correlation TOol."
"Structural matching and discovery in documents such as SGML and HTML is important for data warehousing [6], version management [7, 11], hypertext authoring, digital libraries [4] and Internet databases. As an example, a user of the World Wide Web may be interested in knowing changes in an HTML document [2, 5, 10]. Such changes can be detected by comparing the old and new version of the document (referred to as structural matching of documents). As another example, in hypertext authoring, a user may wish to find the common portions in the history list of a document or in a database of documents (referred to as structural discovery of documents). In SIGMOD 95 demo sessions, we exhibited a software package, called TreeDiff [13], for comparing two latex documents and showing their differences. Given two documents, the tool represents the documents as ordered labeled trees and finds an optimal sequence of edit operations to transform one document (tree) to the other. An edit operation could be an insert, delete, or change of a node in the trees. The tool is so named because documents are represented and compared using approximate tree matching techniques [9, 12, 14]."
"A software architecture is presented that allows client application programs to interact with a DBMS server in a flexible and powerful way, using either direct, volatile messages, or messages sent via recoverable queues. Normal requests from clients to the server and replies from the server to clients can be transmitted using direct or recoverable messages. In addition, an application event notification mechanism is provided, whereby client applications running anywhere on the network can register for events, and when those events are raised, the clients are notified. A novel parameter passing mechanism allows a set of tuples to be included in an event notification. The event mechanism is particularly useful in an active DBMS, where events can be raised by triggers to signal running application programs."
"Similarity search in large time series databases has attracted much research interest recently. It is a difficult problem because of the typically high dimensionality of the data. The most promising solutions involve performing dimensionality reduction on the data, then indexing the reduced data with a multidimensional index structure. Many dimensionality reduction techniques have been proposed, including Singular Value Decomposition (SVD), the Discrete Fourier transform (DFT), and the Discrete Wavelet Transform (DWT). In this article, we introduce a new dimensionality reduction technique, which we call Adaptive Piecewise Constant Approximation (APCA). While previous techniques (e.g., SVD, DFT and DWT) choose a common representation for all the items in the database that minimizes the global reconstruction error, APCA approximates each time series by a set of constant value segments of varying lengths such that their individual reconstruction errors are minimal. We show how APCA can be indexed using a multidimensional index structure. We propose two distance measures in the indexed space that exploit the high fidelity of APCA for fast searching: a lower bounding Euclidean distance approximation, and a non-lower-bounding, but very tight, Euclidean distance approximation, and show how they can support fast exact searching and even faster approximate searching on the same index structure. We theoretically and empirically compare APCA to all the other techniques and demonstrate its superiority."
"DEVise is a data exploration system that allows users to easily develop, browse, and share visual presentation of large tabular datasets (possibly containing or referencing multimedia objects) from several sources. The DEVise framework is being implemented in a tool that has been already successfully applied to a variety of real applications by a number of user groups."
"Data mining technology has given us new capabilities to identify correlations in large data sets. This introduces risks when the data is to be made public, but the correlations are private. We introduce a method for selectively removing individual values from a database to prevent the discovery of a set of rules, while preserving the data for other applications. The efficacy and complexity of this method are discussed. We also present an experiment showing an example of this methodology."
"A new menagerie of middleware is emerging. These products promise great flexibility in partitioning enterprise applications across the diverse corporate computing landscape. What factors should you consider when choosing a solution, and how do current products stack up? More important to the focus of this article, what role should Web servers play?"
"A wide range of Web applications retrieve desired information from remote XML data sources across the Internet, which is usually costly due to transmission delays for large volumes of data. Therefore we propose to apply the ideas of semantic caching to XML query processing systems [2], in particular the XQuery engine. Semantic caching [3] implies view-based query answering and cache management. While it is well studied in the traditional database context, query containment for XQuery is left unexplored due to its complexity coming with the powerful expressiveness of hierarchy, recursion and result construction. We hence have developed the first solution for XQuery processing using cached views.We exploit the connections between XML and tree automata, and use subtype relations between two regular expression types to tackle the XQuery containment mapping problem. Inspired by XDuce [1], which explores the use of tree-automata-based regular expression types for XML processing, we have designed a containment mapping process to incorporate type inference and subtyping mechanisms provided by XDuce to establish containment mappings between regular-expression-type-based pattern variables of two queries. We have implemented a semantic caching system called XCache (see Figure 1), to realize the proposed containment and rewriting techniques for XQuery.The main modules of XCache include: (1) Query Decomposer. An input query is is decomposed into source-specific subqueries explicitly represented by matching patterns and return structures. (2) Query Pattern Register. By registering a few queries into semantic regions, we warm up XCache at its initialization phase. (3) Query Containment Mapper. The XDuce subtyper is incorporated into the containment mapper for establishing query containment mappings between variables of a new query and each cached query. (4) Query Rewriter. We implement the classical bucket algorithm and further apply heuristics to decide on an ""optimal"" rewriting plan if several valid ones exist. (5) Replacement Manager. We free space for new regions by both complete and partial replacement. (6) Region Coalescer. We apply a coalescing strategy to control the region granularity over time."
"The authors describe their approach to the optimization of query execution plans in XPRS, a multi-user parallel database machine based on a shared-memory multi-processor and a disk array. The main difficulties in this optimization problem are the compile-time unknown parameters such as available buffer size and number of free processors, and the enormous search space of possible parallel plans. The authors deal with these problems with a novel two phase optimization strategy which dramatically reduces the search space and allows run time parameters without significantly compromising plan optimality. They present their two phase strategy and give experimental evidence from XPRS benchmarks that indicate that it almost always produces optimal plans.<<ETX>>"
"We propose a novel index structure, the A-tree (approximation tree), for similarity searches in high-dimensional data. The basic idea of the A-tree is the introduction of virtual bounding rectangles (VBRs) which contain and approximate MBRs or data objects. VBRs can be represented quite compactly and thus affect the tree configuration both quantitatively and qualitatively. First, since tree nodes can contain a large number of VBR entries, fanout becomes large, which increases search speed. More importantly, we have a free hand in arranging MBRs and VBRs in the tree nodes. Each A-tree node contains an MBR and its children VBRs. Therefore, by fetching an A-tree node, we can obtain information on the exact position of a parent MBR and the approximate position of its children. We have performed experiments using both synthetic and real data sets. For the real data sets, the A-tree outperforms the SR-tree and the VA-file in all dimensionalities up to 64 dimensions, which is the highest dimension in our experiments. Additionally, we propose a cost model for the A-tree. We verify the validity of the cost model for synthetic and real data sets."
"An important problem faced by many database management systems is the ""online object placement problem""--the problem of choosing a disk page to hold a newly allocated object. In the absence of clustering criteria, the goal is to maximize storage utilization. For main-memory based systems, simple heuristics exist that provide reasonable space utilization in the worst case and excellent utilization in typical cases. However, the storage management problem for databases includes significant additional challenges, such as minimizing I/O traffic, coping with crash recovery, and gracefully integrating space management with locking and logging.We survey several object placement algorithms, including techniques that can be found in commercial and research database systems. We then present a new object placement algorithm that we have designed for use in Shore, an object-oriented database system under development at the University of Wisconsin--Madison. Finally, we present results from a series of experiments involving actual Shore implementations of some of these algorithms. Our results show that while current object placement algorithms have serious performance deficiencies, including excessive CPU or main memory overhead, I/O traffic, or poor disk utilization, our new algorithm consistently excellent performance in all of these areas."
"We consider the problem of approximating sliding window joins over data streams in a data stream processing system with limited resources. In our model, we deal with resource constraints by shedding load in the form of dropping tuples from the data streams. We first discuss alternate architectural models for data stream join processing, and we survey suitable measures for the quality of an approximation of a set-valued query result. We then consider the number of generated result tuples as the quality measure, and we give optimal offline and fast online algorithms for it. In a thorough experimental study with synthetic and real data we show the efficacy of our solutions. For applications with demand for exact results we introduce a new Archive-metric which captures the amount of work needed to complete the join in case the streams are archived for later processing."
"The development of the Internet in recent years has made it possible and useful to access many different information systems anywhere in the world to obtain information. While there is much research on the integration of heterogeneous information systems, most commercial systems stop short of the actual integration of available data. Data fusion is the process of fusing multiple records representing the same real-world object into a single, consistent, and clean representation."
"The challenge in a database of evolving time series is to provide efficient algorithms and access methods for query processing, taking into consideration the fact that the database changes continuously as new data become available. Traditional access methods that continuously update the data are considered inappropriate, due to significant update costs. In this paper, we use the IDC-Index (Incremental DFT Computation - Index), an efficient technique for similarity query processing in streaming time series. The index is based on a multidimensional access method enhanced with a deferred update policy and an incremental computation of the Discrete Fourier Transform (DFT), which is used as a feature extraction method. We focus both on range and nearest-neighbor queries, since both types are frequently used in modern applications. An important characteristic of the proposed approach is its ability to adapt to the update frequency of the data streams. By using a simple heuristic approach, we manage to keep the update frequency at a specified level to guarantee efficiency. In order to investigate the efficiency of the proposed method, experiments have been performed for range queries and k-nearest-neighbor queries on real-life data sets. The proposed method manages to reduce the number of false alarms examined, achieving high answers vs. candidates ratio. Moreover, the results have shown that the new techniques exhibit consistently better performance in comparison to previously proposed approaches."
"This paper describes GnatDb, which is an embedded database system that provides protection against both accidental and malicious corruption of data. GnatDb is designed to run on a wide range of appliances, some of which have very limited resources. Therefore, its design is heavily driven by the need to reduce resource consumption. GnatDb employs atomic and durable updates to protect the data against accidental corruption. It prevents malicious corruption of the data using standard cryptographic techniques that leverage the underlying log-structured storage model. We show that the total memory consumption of GnatDb, which includes the code footprint, the stack and the heap, does not exceed 11 KB, while its performance on a typical appliance platform remains at an acceptable level."
"We introduce the Iceberg-CUBE problem as a reformulation of the datacube (CUBE) problem. The Iceberg-CUBE problem is to compute only those group-by partitions with an aggregate value (e.g., count) above some minimum support threshold. The result of Iceberg-CUBE can be used (1) to answer group-by queries with a clause such as HAVING COUNT(*) >= X, where X is greater than the threshold, (2) for mining multidimensional association rules, and (3) to complement existing strategies for identifying interesting subsets of the CUBE for precomputation."
"Over the last decades, improvements in CPU speed have outpaced improvements in main memory and disk access rates by orders of magnitude, enabling the use of data compression techniques to improve the performance of database systems. Previous work describes the benefits of compression for numerical attributes, where data is stored in compressed format on disk. Despite the abundance of string-valued attributes in relational schemas there is little work on compression for string attributes in a database context. Moreover, none of the previous work suitably addresses the role of the query optimizer: During query execution, data is either eagerly decompressed when it is read into main memory, or data lazily stays compressed in main memory and is decompressed on demand only"
The Capability Maturity Model [4] is an orderly way for organizations to determine the capabilities of their current processes for developing software and to establish priorities for improvement [2]. It defines five levels of progressively more mature process capability [3].
"Current information systems are required to deal with more complex data with respect to traditional relational data. The database community has already proposed abstractions for these kinds of data, in particular in terms of semistructured data models. A semistructured model conceives a database essentially as a finite directed labeled graph whose nodes represent objects, and whose edges represent relationships between objects. In the same way as conjunctive queries form the core of any query language for the relational model, regular path queries (RPQs) and their variants are considered the basic querying mechanisms for semistructured data.Besides the basic task of query answering, i.e., evaluating a query over a database, databases should support other reasoning services related to querying. One of the most important is query containment, i.e., verifying whether for all databases the answer to a query is a subset of the answer to a second query. Another important reasoning service that has received considerable attention in the recent years is view-based query processing, which amounts to processing queries based on a set of materialized views, rather than on the raw data in the database.The goal of this paper is to describe basic results and techniques concerning query containment and view based query processing for the class of two-way regular-path queries (which extend RPQs with the inverse operator). We will demonstrate that the basic services for reasoning about two way regular path queries are decidable, thus showing that the limited form of recursion expressible by these queries does not endanger the decidability of reasoning. Besides the specific results, our methods show the power of two-way automata in reasoning on complex queries."
"This paper investigates the problem of incremental joins of multiple ranked data sets when the join condition is a list of arbitrary user-defined predicates on the input tuples. This problem arises in many important applications dealing with ordered inputs and multiple ranked data sets, and requiring the top solutions. We use multimedia applications as the motivating examples but the problem is equally applicable to traditional database applications involving optimal resource allocation, scheduling, decision making, ranking, etc. We propose an algorithm that enables querying of ordered data sets by imposing arbitrary userdefined join predicates. The basic version of the algorithm does not use any random access but a variation can exploit available indexes for efficient random access based on the join predicates. A special case includes the join scenario considered by Fagin [1] for joins based on identical keys, and in that case, our algorithms perform as efficiently as Fagin¡¯s. Our main contribution, however, is the generalization to join scenarios that were previously unsupported, including cases where random access in the algorithm is not possible due to lack of unique keys. In addition, can support multiple join levels, or nested join hierarchies, which are the norm for modeling multimedia data. We also give -approximation versions of both of the above algorithms. Finally, we give strong optimality results for some of the proposed algorithms, and we study their performance empirically."
"Physical layout of data is a crucial determinant of performance in a data warehouse. The optimal clustering of data on disk, for minimizing expected I/O, depends on the query workload. In practice, we often have a reasonable sense of the likelihood of different classes of queries, e.g., 40% of the queries concern calls made from some specific telephone number in some month. In this paper, we address the problem of finding an optimal clustering of records of a fact table on disk, given an expected workload in the form of a probability distribution over query classes."
The tutorial ¡°Semantic B2B Integration¡± will give an introduction to the field of business-to-business (B2B) integration from a technical viewpoint with the focus on semantic integration aspects. The set of B2B integration concepts is introduced as well as their implementation in form of a technical semantic B2B integration architecture. A mix of examples is taken illustrating the problems that need to be solved in semantic B2B integration projects. The tutorial enables the audience to identify semantic B2B integration problems as well as to determine the benefits and deficiencies of various technical integration architecture approaches or B2B integration technologies.
"In a video-on-demand server, resource reservation is required to guarantee continuous delivery. Hence any given storage device (or a striping group treated as a single logical device) can serve only up to a fixed number of client access streams. Each storage device is also limited by the number of video files it can store. For the reasons of availability, incremental growth, and heterogeneity, there may be multiple storage devices in a video server environment. Hence, one or more copies of a particular video may be placed on different storage devices. Since the access rates to different videos are not uniform, there may be load imbalance among the devices. In this paper, we propose a dynamic placement policy (called the Bandwidth to Space Ratio (BSR) Policy) that creates and/or deletes replica of a video, and mixes hot and cold videos so as to make the best use of bandwidth and space of a storage device. The proposed policy is evaluated using a simulation study."
"Approximately every five years, a group of database researchers meet to do a self-assessment of our community, including reflections on our impact on the industry as well as challenges facing our research community. This report summarizes the discussion and conclusions of the 9th such meeting, held during October 9-10, 2018 in Seattle."
"Spatio-temporal databases deal with geometries changing over time. The goal of our work is to provide a DBMS data model and query language capable of handling such time-dependent geometries, including those changing continuously that describe moving objects. Two fundamental abstractions are moving point and moving region, describing objects for which only the time-dependent position, or position and extent, respectively, are of interest. We propose to present such time-dependent geometries as attribute data types with suitable operations, that is, to provide an abstract data type extension to a DBMS data model and query language. This paper presents a design of such a system of abstract data types. It turns out that besides the main types of interest, moving point   and moving region, a relatively large number of auxiliary data types are needed. For example, one needs a line type to represent the projection of a moving point into the plane, or a ¡°moving real¡± to represent the time-dependent distance of two points. It then becomes crucial to achieve (i) orthogonality in the design of the system, i.e., type constructors can be applied unifomly; (ii) genericity and consistency of operations, i.e., operations range over as many types as possible and behave consistently; and (iii) closure and consistency between structure and operations of nontemporal and related temporal types. Satisfying these goal leads to a simple and expressive system of abstract data types that may be integrated into a query language to yield a powerful language for   querying spatio-temporal data, including moving objects. The paper formally defines the types and operations, offers detailed insight into the considerations that went into the design, and exemplifies the use of the abstract data types using SQL. The paper offers a precise and conceptually clean foundation for implementing a spatio-temporal DBMS extension."
"Spatial data mining is to mine high-level spatial information and knowledge from large spatial databases. A spatial data mining system prototype, GeoMiner, has been designed and developed based on our years of experience in the research and development of relational data mining system, DBMiner, and our research into spatial data mining. The data mining power of GeoMiner includes mining three kinds of rules: characteristic rules, comparison rules, and association rules, in geo-spatial databases, with a planned extension to include mining classification rules and clustering rules. The SAND (Spatial And Nonspatial Data) architecture is applied in the modeling of spatial databases, whereas GeoMiner includes the spatial data cube construction module, spatial on-line analytical processing (OLAP) module, and spatial data mining modules. A spatial data mining language, GMQL (Geo-Mining Query Language), is designed and implemented as an extension to Spatial SQL [3], for spatial data mining. Moreover, an interactive, user-friendly data mining interface is constructed and tools are implemented for visualization of discovered spatial knowledge."
"The emergence of Big Data has amounted to the complexity of the discussion on data reuse. The benefits of Big Data lie in the possibilities to discover novel trends, patterns and relationships by combining very large amounts of data from different sources. Current personal data protection requirements like data minimization and purpose specification are potentially inimical to Big Data as they limit the size and use of Big Data. Substantial loss of economic and social benefits of Big Data may be the result. In order to avoid this, the reuse of data could be encouraged. Data reuse, when done properly, may be both privacy preserving and economically and socially beneficial. In this paper, we provide a taxonomy of data reuse from both the data controller¡¯s and the data subject¡¯s perspective that may be useful to determine the extent to which data reuse should be allowed and under which conditions. From the data controller¡¯s perspective we distinguish data recycling, data repurposing and data recontextualisation. From the data subject¡¯s perspective, we distinguish data sharing and data portability. It is argued that forms of data reuse that stay close to the awareness and intentions of data subjects should be approached less tight (for instance, by assuming informed consent), whereas forms of data reuse that are ¡®at a distance¡¯, i.e., in which awareness and transparency may be lacking and data subject¡¯s rights may prove more difficult to exercise, more restrictions and additional protection should be considered (for instance, by requiring explicit consent)."
"Current studies on the storage of XML data are focused on either the efficient mapping of XML data onto an existing RDBMS or the development of a native XML storage. Some native XML storages store each XML node in a parsed object form. Clustering, which means the physical arrangement of objects, can be an important factor in improving the performance in this storage model. In this paper, we propose a clustering method that stores data nodes in an XML document into the native XML storage. The proposed clustering method uses path similarities between data nodes, which can reduce page I/Os required for query processing. In addition, we propose a query processing method using signatures that facilitate the cluster-level access on the stored data to benefit from the proposed clustering method. This method can process a path query by accessing only a small number of clusters and thus need not use all of the clusters, hence enabling the path query to be processed efficiently by skipping unnecessary data. Finally, we compare the performance of the proposed method with that of the existing ones. Our results show that the performance of XML storage can be improved by using a proper clustering method."
"Reverse Nearest Neighbor (RNN) queries have been studied for finite, stored data sets and are of interest for decision support. However, in many applications such as fixed wireless telephony access and sensor-based highway traffic monitoring, the data arrives in a stream and cannot be stored. Exploratory analysis on this data stream can be formalized naturally using the notion of RNN aggregates (RNNAs), which involve the computation of some aggregate (such as C0UNT or MAX DISTANCE) over the set of reverse nearest neighbor ""clients"" associated with each ""server""."
"Empirical research based on time series is a data intensive activity that needs a data base management system (DBMS). We investigate the special properties a time series management system (TSMS) should have. We then show that currently available solutions and related research directions are not well suited to handle the existing problems. Therefore, we propose the development of a special purpose TSMS, which will offer particular modeling, retrieval, and computation capabilities. It will be suitable for end users, offer direct manipulation interfaces, and allow data exchange with a variety of data sources, including other databases and application packages. We intend to build such a system on top of an off-the-shelf object-oriented DBMS."
"Similarity retrieval mechanisms should utilize generalized quadratic form distance functions as well as the Euclidean distance function since ellipsoid queries parameters may vary with the user and situation. In this paper, we present the spatial transformation technique that yields a new search method for adaptive ellipsoid queries with quadratic form distance functions. The basic idea is to transform the bounding rectangles in the original space, wherein distance from a query point is measured by quadratic form distance functions, into spatial objects in a new space wherein distance is measured by Euclidean distance functions. Our method significantly reduces CPU cost due to the distance approximation by the spatial transformation; exact distance evaluations are avoided for most of the accessed bounding rectangles in the index structures. We also present the multiple spatial transformation technique as an extension of the spatial transformation technique. The multiple spatial transformation technique adjusts the tree structures to suit typical ellipsoid queries; the search algorithm utilizes the adjusted structure. This technique reduces both page accesses and CPU time for ellipsoid queries. Experiments using various matrices and index structures demonstrate the superiority of the proposed methods."
"The number, size, and user population of bibliographic and full-text document databases are rapidly growing. With a high document arrival rate, it becomes essential for users of such databases to have access to the very latest documents; yet the high document arrival rate also makes it difficult for users to keep themselves updated. It is desirable to allow users to submit profiles, i.e., queries that are constantly evaluated, so that they will be automatically informed of new additions that may be of interest. Such service is traditionally called Selective Dissemination of Information (SDI)."
"Catalog management in websphere commerce suite. Share on. Author: Thomas Maguire. IBM, Hawthorne. IBM, Hawthorne. Search about this author. Authors Info & Affiliations. Publication: SIGMOD '01: Proceedings of the 2001 ACM SIGMOD international conference on Management of dataMay 2001 https://doi.org/10.1145/375663.375742. 0citation; 268 Downloads. Metrics. Total Citations0. Total Downloads268. Last 12 Months5. Last 6 weeks4. Get Citation Alerts New Citation Alert added! This alert has been successfully added"
"The querying and analysis of data streams has been a topic of much recent interest, motivated by applications from the fields of networking, web usage analysis, sensor instrumentation, telecommunications, and others. Many of these applications involve monitoring answers to continuous queries over data streams produced at physically distributed locations, and most previous approaches require streams to be transmitted to a single location for centralized processing. Unfortunately, the continual transmission of a large number of rapid data streams to a central location can be impractical or expensive. We study a useful class of queries that continuously report the k largest values obtained from distributed data streams (""top-k monitoring queries""), which are of particular interest because they can be used to reduce the overhead incurred while running other types of monitoring queries. We show that transmitting entire data streams is unnecessary to support these queries and present an alternative approach that reduces communication significantly. In our approach, arithmetic constraints are maintained at remote stream sources to ensure that the most recently provided top-k answer remains valid to within a user-specified error tolerance. Distributed communication is only necessary on occasion, when constraints are violated, and we show empirically through extensive simulation on real-world data that our approach reduces overall communication cost by an order of magnitude compared with alternatives that o er the same error guarantees."
"We consider a variant of the view maintenance problem: How does one keep a materialized view up-to-date when the view definition itself changes? Can one do better than recomputing the view from the base relations? Traditional view maintenance tries to maintain the materialized view in response to modifications to the base relations; we try to ""adapt"" the view in response to changes in the view definition.Such techniques are needed for applications where the user can change queries dynamically and see the changes in the results fast. Data archaeology, data visualization, and dynamic queries are examples of such applications.We consider all possible redefinitions of SQL SELECT-FROM-WHERE-GROUPBY, UNION, and EXCEPT views, and show how these views can be adapted using the old materialization for the cases where it is possible to do so. We identify extra information that can be kept with a materialization to facilitate redefinition. Multiple simultaneous changes to a view can be handled without necessarily materializing intermediate results. We identify guidelines for users and database administrators that can be used to facilitate efficient view adaptation."
"In this paper we investigate the co-authorship graph obtained from all papers published at SIGMOD between 1975 and 2002. We find some interesting facts, for instance, the identity of the authors wh..."
"In the era of electronic publishing, there is a need for a comprehensive Web Site Management System (WSMS) that provides an end-to-end solution ranging from integration of web sites to re-structuring and maintenance of new customized web views."
"Spatial data mining is the discovery of interesting relationships and characteristics that may exist implicitly in spatial databases. In this paper, we explore whether clustering methods have a role to play in spatial data mining. To this end, we develop a new clustering method called CLAHANS which is based on randomized search. We also develop two spatial data mining algorithms that use CLAHANS. Our analysis and experiments show that with the assistance of CLAHANS, these two algorithms are very effective and can lead to discoveries that are difficult to find with current spatial data mining algorithms. Furthermore, experiments conducted to compare the performance of CLAHANS with that of existing clustering methods show that CLAHANS is the most efficient."
"It is now common for databases to contain many gigabytes, or even many terabytes, of data. Scientific experiments in areas such as high energy physics produce data sets of enormous size, while in the business sector the emergence of decision-support systems and data warehouses has led organizations to build up gigantic collections of data. Aggregate queries allow one to retrieve concise information from such a database, since they can cover many data items while returning a small result. OLAP queries, used extensively in data warehousing, are based almost entirely on aggregation [4, 16]. Aggregate queries have also been studied in a variety of settings beyond relational databases, such as mobile computing [1], global information systems [21], stream data analysis [12], sensor networks [22] and constraint databases [2]."
"Protecting rights over relational data is of ever increasing interest, especially considering areas where sensitive, valuable content is to be outsourced. A good example is a data mining application, where data is sold in pieces to parties specialized in mining it.Different avenues for rights protection are available, each with its own advantages and drawbacks. Enforcement by legal means is usually ineffective in preventing theft of copyrighted works, unless augmented by a digital counter-part, for example watermarking.Recent research of the authors introduces the issue of digital watermarking for generic number sets. In the present paper we expand on this foundation and introduce a solution for relational database content rights protection through watermarking.Our solution addresses important attacks, such as data re-sorting, subset selection, linear data changes (applying a linear transformation on arbitrary subsets of the data). Our watermark also survives up to 50% and above data loss.Finally we present wmdb.*, a proof-of-concept implementation of our algorithm and its application to real life data, namely in watermarking the outsourced Wal-Mart sales data that we have available at our institute."
"This paper describes a tool, called Nodose, we have developed to expedite the creation of robust wrappers. Nodose allows non-programmers to build components that can convert data from the source format to XML or another generic format. Further, the generated code performs a set of statistical checks at runtime that attempt to find extraction errors before they are propogated back to users."
"workflow, business process, HPPM (HP Process Manager), data analysis, visualization of data Business Process Cockpit (BPC) is a tool that supports real-time monitoring, analysis, management, and optimization of business processes running on top of HP Process Manager, the Business Process Management System developed by HewlettPackard. The main goal of the Business Process Cockpit is to enable business users to perform business-level quality analysis, monitoring, and management of business processes. The BPC visualizes process execution data according to different focus points that identify the process entities that are the focus of the analysis, and different perspectives that define a way to look at the information. The BPC also allows users to define new concepts, such as ¡°slow¡± and ¡°fast¡± executions, and use those concepts to categorize the viewed data and make it much easier for users to interpret."
"Although many extended transaction models have been proposed [Elm93], few practical implementations exist and even fewer can support more than one model. We present the Reflective Transaction Framework, as a practical and modular method to implement extended transaction models. We achieve modularity by applying the Open Implementation approach [Kic92] (also known as meta-object protocol [KdRBSl]) to the design of the reflective transaction framework. We achieve practicality by implementing on top of a commercial transaction processing monitor. For our implementation of the reflective transaction framework, we introduce transaction adapters, add-on modules built on top of existing commercial TP components, such as Encina, that extend their functionality to support extended transaction features and semantics. Since our framework design is based on the transaction processing monitor architecture [GR93], it is widely applicable to many modern TP monitors. The reflective transaction framework enables us to implement a wide range of independently proposed extended transaction models, which we demonstrate by implementing the split/join model [PKH88] and cooperative transaction groups [MP92, RC92]."
"Various commercial and scientific applications require analysis of user behaviour in the Internet. For example, web marketing or network technical support can benefit from web users classification. This is achievable by tracking pages visited by the user during one session (one visit to the particular site). For automated user sessions classification we propose distance that compares sessions judging by the sequence of pages in them and by categories of these pages. Proposed distance is based on Levenshtein metric. Fuzzy C Medoids algorithm was used for clustering, since it has almost linear complexity. Davies-Bouldin, Entropy, and Bezdek validity indices were used to assess the qualities of proposed method. As testing shows, our distance outperforms in this domain both Euclidian and Edit distances."
"We address the problem of efficiently constructing materialized XML views of relational databases. In our setting, the XML view is specified by a query in the declarative query language of a middle-ware system, called SilkRoute. The middle-ware system evaluates a query by sending one or more SQL queries to the target relational database, integrating the resulting tuple streams, and adding the XML tags. We focus on how to best choose the SQL queries, without having control over the target RDBMS."
"We propose multi-precision similarity matching where the image is divided into a number of subblocks, each with its associated color histogram. We present experimental results showing that the spatial distribution information recorded by multiprecision color histograms helps to make similarity matching more precise. We also show that sub-image queries are much better supported with multi-precision color histograms. To minimize the overhead, we employ a filtering scheme based on the 3-dimensional average color vectors. We provide a formal result proving that filtering with multi-precision color histograms is complete. Finally, we develop a novel extendible hashing structure for indexing the average color vectors. We give experimental results showing that the proposed structure significantly outperforms the SR-tree."
"In this article, we study how we can maintain local copies of remote data sources ""fresh,"" when the source data is updated autonomously and independently. In particular, we study the problem of Web crawlers that maintain local copies of remote Web pages for Web search engines. In this context, remote data sources (Websites) do not notify the copies (Web crawlers) of new changes, so we need to periodically poll the sources to maintain the copies up-to-date. Since polling the sources takes significant time and resources, it is very difficult to keep the copies completely up-to-date.This article proposes various refresh policies and studies their effectiveness. We first formalize the notion of ""freshness"" of copied data by defining two freshness metrics, and we propose a Poisson process as the change model of data sources. Based on this framework, we examine the effectiveness of the proposed refresh policies analytically and experimentally. We show that a Poisson process is a good model to describe the changes of Web pages and we also show that our proposed refresh policies improve the ""freshness"" of data very significantly. In certain cases, we got orders of magnitude improvement from existing policies."
"In this paper, we discuss mixed-media access, an information access paradigm for multimedia data in which the media type of a query may differ from that of the data. The types of media considered in this paper are speech, images of text, and full-length text. Some examples of metadata for mixed-media access are locations of keywords in speech and images, identification of speakers, locations of emphasized regions in speech, and locations of topic boundaries in text. Algorithms for automatically generating this metadata are described, including word spotting, speaker segmentation, emphatic speech detection, and subtopic boundary location. We illustrate queries composed of diverse media types in an example of access to recorded meetings, via speaker and keyword location."
"We propose a definition of a spatial database system as a database system that offers spatial data types in its data model and query language, and supports spatial data types in its implementation, providing at least spatial indexing and spatial join methods. Spatial database systems offer the underlying database technology for geographic information systems and other applications. We survey data modeling, querying, data structures and algorithms, and system architecture for such systems. The emphasis is on describing known technology in a coherent manner, rather than listing open problems."
"Finding approximate answers to multi-dimensional range queries over real valued attributes has significant applications in data exploration and database query optimization. In this paper we consider the following problem: given a table of d attributes whose domain is the real numbers, and a query that specifies a range in each dimension, find a good approximation of the number of records in the table that satisfy the query."
We present techniques for computing small space representations of massive data streams. These are inspired by traditional wavelet-based approximations that consist of specific linear projections of the underlying data. We present general "sketch"-based methods for capturing various linear projections and use them to provide pointwise and rangesum estimation of data streams. These methods use small amounts of space and per-item time while streaming through the data and provide accurate representation as our experiments with real data streams show.
"With the growing importance of XML in data exchange, much research has been done in providing flexible query facilities to extract data from structured XML documents. In this paper, we propose ViST, a novel index structure for searching XML documents. By representing both XML documents and XML queries in structure-encoded sequences, we show that querying XML data is equivalent to finding subsequence matches. Unlike index methods that disassemble a query into multiple sub-queries, and then join the results of these sub-queries to provide the final answers, ViST uses tree structures as the basic unit of query to avoid expensive join operations. Furthermore, ViST provides a unified index on both content and structure of the XML documents, hence it has a performance advantage over methods indexing either just content or structure. ViST supports dynamic index update, and it relies solely on B+ Trees without using any specialized data structures that are not well supported by DBMSs. Our experiments show that ViST is effective, scalable, and efficient in supporting structural queries."
"The analytic prediction of buffer hit probability, based on the characterization of database accesses from real reference traces, is extremely useful for workload management and system capacity planning. The knowledge can be helpful for proper allocation of buffer space to various database relations, as well as for the management of buffer space for a mixed transaction and query environment. Access characterization can also be used to predict the buffer invalidation effect in a multi-node environment which, in turn, can influence transaction routing strategies. However, it is a challenge to characterize the database access pattern of a real workload reference trace in a simple manner that can easily be used to compute buffer hit probability. In this article, we use a characterization method that distinguishes three types of access patterns from a trace: (1) locality within a transaction, (2) random accesses by transactions, and (3) sequential accesses by long queries. We then propose a concise way to characterize the access skew across randomly accessed pages by logically grouping the large number of data pages into a small number of partitions such that the frequency of accessing each page within a partition can be treated as equal. Based on this approach, we present a recursive binary partitioning algorithm that can infer the access skew characterization from the buffer hit probabilities for a subset of the buffer sizes. We validate the buffer hit predictions for single and multiple node systems using production database traces. We further show that the proposed approach can predict the buffer hit probability of a composite workload from those of its component files."
"Clio is a system for managing and facilitating the complex tasks of heterogeneous data transformation and integration. In Clio, we have collected together a powerful set of data management techniques that have proven invaluable in tackling these difficult problems. In this paper, we present the underlying themes of our approach and present a brief case study."
"Many sources on the Internet and elsewhere rank the objects in query results according to how well these objects match the original query. For example, a real-estate agent might rank the available houses according to how well they match the user's preferred location and price. In this environment, ``meta-brokers'' usually query multiple autonomous, heterogeneous sources that might use varying result-ranking strategies. A crucial problem that a meta-broker then faces is extracting from the underlying sources the top objects for a user query according to the meta-broker's ranking function. This problem is challenging because these top objects might not be ranked high by the sources where they appear. In this paper we discuss strategies for solving this ``meta-ranking'' problem. In particular, we present a condition that a source must satisfy so that a meta-broker can extract the top objects for a query from the source without examining its entire contents. Not only is this condition necessary but it is also sufficient, and we show an efficient algorithm to extract the top objects from sources that satisfy the given condition."
"Detecting changes by comparing data snapshots is an important requirement for difference queries, active databases, and version and configuration management. In this paper we focus on detecting meaningful changes in hierarchically structured data, such as nested-object data. This problem is much more challenging than the corresponding one for relational or flat-file data. In order to describe changes better, we base our work not just on the traditional ¡°atomic¡± insert, delete, update operations, but also on operations that move an entire sub-tree of nodes, and that copy an entire sub-tree. These operations allows us to describe changes in a semantically more meaningful way. Since this change detection problem is NP-hard, in this paper we present a heuristic change detection algorithm that yields close to ¡°minimal¡± descriptions of the changes, and that has fewer restrictions than previous algorithms. Our algorithm is based on transforming the change detection problem to a problem of computing a minimum-cost edge cover of a bipartite graph. We study the quality of the solution produced by our algorithm, as well as the running time, both analytically and experimentally."
"1. MOTIVATION AND SUMMARY Traditional Database Management Systems (DBMS) software is built on the concept of persistent data sets, that are stored reliably in stable storage and queried/updated several times throughout their lifetime. For several emerging application domains, however, data arrives and needs to be processed on a continuous ( ) basis, without the benefit of several passes over a static, persistent data image. Such continuous data streams arise naturally, for example, in the network installations of large Telecom and Internet service providers where detailed usage information (Call-Detail-Records (CDRs), SNMP/RMON packet-flow data, etc.) from different parts of the underlying network needs to be continuously collected and analyzed for interesting trends. Other applications that generate rapid, continuous and large volumes of stream data include transactions in retail chains, ATM and credit card operations in banks, financial tickers, Web server log records, etc. In most such applications, the data stream is actually accumulated and archived in the DBMS of a (perhaps, off-site) data warehouse, often making access to the archived data prohibitively expensive. Further, the ability to make decisions and infer interesting patterns on-line (i.e., as the data stream arrives) is crucial for several mission-critical tasks that can have significant dollar value for a large corporation (e.g., telecom fraud detection). As a result, recent years have witnessed an increasing interest in designing data-processing algorithms that work over continuous data streams, i.e., algorithms that provide results to user queries while looking at the relevant data items only once and in a fixed order (determined by the stream-arrival pattern). Two key parameters for query processing over continuous datastreams are (1) the amount of memory made available to the online algorithm, and (2) the per-item processing time required by the query processor. The former constitutes an important constraint on the design of stream processing algorithms, since in a typical streaming environment, only limited memory resources are available to the query-processing algorithms. In these situations, we need algorithms that can summarize the data stream(s) involved in a concise, but reasonably accurate, synopsis that can be stored in the allotted (small) amount of memory and can be used to provide approximate answers to user queries along with some reasonable guarantees on the quality of the approximation. Such approx-"
"More than two decades ago, DB researchers faced up to the question of how to design a data-independent database management system (DBMS), that is, a DBMS which offers an appropriate application programming interface (API) to the user and whose architecture is open for permanent evolution. For this purpose, an architectural model based on successive data abstraction steps of record-oriented data was proposed as kind of a standard and later refined to a five-layer hierarchical DBMS model. We review the basic concepts and implementation techniques of this model and survey the major improvements achieved in the system layers to date. Furthermore, we consider the interplay of the layered model with the transactional ACID properties and again outline the progress obtained. In the course of the last 20 years, this DBMS architecture was challenged by a variety of new requirements and changes as far as processing environments, data types, functional extensions, heterogeneity, autonomy, scalability, etc. are concerned. We identify the cases which can be adjusted by our standard system model and which need major extensions or other types of system models."
"A data warehouse provides information for analytical processing, decision making and data mining tools. As the concept of real-time enterprise evolves, the synchronism between transactional data and data warehouses, statically implemented, has been redefined. Traditional data warehouse systems have static structures of their schemas and relationships between data, and therefore are not able to support any dynamics in their structure and content. Their data is only periodically updated because they are not prepared for continuous data integration. For real-time enterprises with needs in decision support purposes, real-time data warehouses seem to be very promising. In this paper we present a methodology on how to adapt data warehouse schemas and user-end OLAP queries for efficiently supporting real-time data integration. To accomplish this, we use techniques such as table structure replication and query predicate restrictions for selecting data, to enable continuously loading data in the data warehouse with minimum impact in query execution time. We demonstrate the efficiency of the method by analyzing its impact in query performance using benchmark TPC-H executing query workloads while simultaneously performing continuous data integration at various insertion time rates."
"The ISDO '00 workshop on ""Infrastructures for Dynamic Business-to-Business Service Outsourcing"" [1] was held as a preconference workshop of the 12th Conference on Advanced Information Systems Engineering (CAiSE *00) in Stockholm, Sweden, on June 5 and 6, 2000. C. Bussler (Net-fish Technologies), M. Bichler (Vienna University of Economics and Business Administration), and Y. Hoffner and H. Ludwig (IBM Zurich Research Laboratory) organised the workshop and chaired the program committee.The objective of the workshop was to provide a platform to discuss models and technologies for service outsourcing, with emphasis on the integration of the dynamic establishment, setup, and enactment of service relationships that connect the business processes of service provider and consumer businesses, thereby establishing virtual enterprises.Nowadays, many production companies integrate their procurement processes using online marketplaces and network-based supply chain management systems. However, this is not the case for the service industry. Whereas many service organisations have already automated their internal business process management (e.g. using workflow management systems or enterprise resource planning (ERP) systems), service marketplaces still remain an uncommon phenomenon. The reason for this is that the integration of service sales, service enactment, and customer interaction with the service process still appears to be highly difficult. This is particularly the case where complex services, such as insurance and complex logistics, involve considerable customer interaction."
"Primary B-tree, a variant of B-tree structure with row data in leaf blocks, is an ideal storage organization for queries involving exact match and/or range search on primary keys. Commercially, primary B-tree like structures have been supported in DBMSs like Compaq Non-Stop SQL, Sybase Adaptive Server, and Microsoft SQL Server. Oracle¡¯s index-organized table is like a primary B-tree; however, it differs from its commercial counterparts in the following respects: 1) The storage organization does not require the entire row to be stored in the primary key index. Infrequently accessed columns can be selectively pushed into an overflow storage area to speed up access to columns that are frequently accessed. 2) Secondary indexes on index-organized tables support logical primary key-based row identifiers, and still provide performance comparable to secondary indexes with physical row identifiers by storing and making use of guess-DBA (Database Block Address). 3) Support for primary key compression leads to reduced storage requirements. This paper presents the index-organized table storage option in Oracle8i with emphasis on the novel aspects mentioned above. The applicability of index-organized tables to new domains such as the Internet, E-Commerce and Data Warehousing is discussed. A performance study is presented, that validates the clustering benefits of Oracle¡¯s primary B-tree implementation, and characterizes the impact of overflow storage area, guess-DBA use in secondary B-tree indexes, and primary key compression."
"Most declarative SQL-like query languages for object-oriented database systems are orthogonal languages allowing for arbitrary nesting of expressions in the select-, from-, and where-clause. Expressions in the from-clause may be base tables as well as set-valued attributes. In this paper, we propose a general strategy for the optimization of nested OOSQL queries. As in the relational model, the translation/optimization goal is to move from tuple- to set-oriented query processing. Therefore, OOSQL is translated into the algebraic language ADL, and by means of algebraic rewriting nested queries are transformed into join queries as far as possible. Three different optimization options are described, and a strategy to assign priorities to options is proposed."
"Modern applications (Web portals, digital libraries, etc.) require integrated access to various information sources (from traditional DBMS to semistructured Web repositories), fast deployment and low maintenance cost in a rapidly evolving environment. Because of its flexibility, there is an increasing interest in using XML as a middleware model for such applications. XML enables fast wrapping and declarative integration. However, query processing in XML-based integration systems is still penalized by the lack of an algebra with adequate optimization properties and the difficulty to understand source query capabilities. In this paper, we propose an algebraic approach to support efficient XML query evaluation. We define a general purpose algebra suitable for semistructured on XML query languages. We show how this algebra can be used, with appropriate type information, to also wrap more structured query languages such as OQL or SQL. Finally, we develop new optimization techniques for XML-based integration systems."
This paper proposes an object database evolution approach based on separation of concerns. The lack of customisability and extensibility in existing evolution frameworks is a consequence of using attributes at the meta-object level to implement links among meta-objects and the injection of instance adaptation code directly into the class versions. The proposed approach uses dynamic relationships to separate the connection code from meta-objects and aspects - abstractions used by Aspect-Oriented Programming to localise cross-cutting concerns - to separate the instance adaptation code from class versions. The result is a customisable and extensible evolution framework with low maintenance overhead.
"Curated databases are databases that are populated and updated with a great deal of human effort. Most reference works that one traditionally found on the reference shelves of libraries -- dictionaries, encyclopedias, gazetteers etc. -- are now curated databases. Since it is now easy to publish databases on the web, there has been an explosion in the number of new curated databases used in scientific research. The value of curated databases lies in the organization and the quality of the data they contain. Like the paper reference works they have replaced, they usually represent the efforts of a dedicated group of people to produce a definitive description of some subject area."
"Approximately every five years, a group of database researchers meet to do a self-assessment of our community, including reflections on our impact on the industry as well as challenges facing our research community. This report summarizes the discussion and conclusions of the 9th such meeting, held during October 9-10, 2018 in Seattle."
"In the typical database system, an execution is correct if it is equivalent to some serial execution. This criterion, called serializability, is unacceptable for new database applications which require long-duration transactions. We present a new transaction model which allows correctness criteria more suitable for these applications. This model combines three enhancements to the standard model: nested transactions, explicit predicates, and multiple versions. These features yield the name of the new model, nested transactions with predicates and versions, or NT/PV."
"We present the architecture behind Twitter's real-time related query suggestion and spelling correction service. Although these tasks have received much attention in the web search literature, the Twitter context introduces a real-time ""twist"": after significant breaking news events, we aim to provide relevant results within minutes. This paper provides a case study illustrating the challenges of real-time data processing in the era of ""big data"". We tell the story of how our system was built twice: our first implementation was built on a typical Hadoop-based analytics stack, but was later replaced because it did not meet the latency requirements necessary to generate meaningful real-time results. The second implementation, which is the system deployed in production today, is a custom in-memory processing engine specifically designed for the task. This experience taught us that the current typical usage of Hadoop as a ""big data"" platform, while great for experimentation, is not well suited to low-latency processing, and points the way to future work on data analytics platforms that can handle ""big"" as well as ""fast"" data."
"In many applications, users specify target values for certain attributes, without requiring exact matches to these values in return. Instead, the result to such queries is typically a rank of the top k"" tuples that best match the given attribute values. In this paper, we study the advantages and limitations of processing a top-k query by translating it into a single range query that traditional relational DBMSs can process eciently. In particular, we study how to determine a range query to evaluate a top-k query by exploiting the statistics available to a relational DBMS, and the impact of the quality of these statistics on the retrieval eciency of the resulting scheme."
"Semantic Web Enabled Web Services (SWWS) will transform the web from a static collection of information into a distributed device of computation on the basis of Semantic technology making content within the World Wide Web machine-processable and machine-interpretable. Semantic Web Enabled Web Services will allow the automatic discovery, selection and execution of inter-organization business logic making areas like dynamic supply chain composition a reality. In this paper we introduce the vision of Semantic Web Enabled Web Services, describe requirements for building semantics-driven web services and sketch a first draft of conceptual architecture for implementing semantic web enabled web services."
"Persistent Application Systems (PASs) are of increasing social and economic importance. They have the potential to be long-lived, concurrently accessed, and consist of large bodies of data and programs. Typical examples of PASs are CAD/CAM systems, office automation, CASE tools, software engineering environments, and patient-care support systems in hospitals. Orthogonally persistent object systems are intended to provide improved support for the design, construction, maintenance, and operation of PASs. Persistence abstraction allows the creation and manipulation of data in a manner that is independent of its lifetime, thereby integrating the database view of information with the programming language view. This yields a number of advantages in terms of orthogonal design and programmer productivity which are beneficial for PASs. Design principles have been proposed for persistent systems. By following these principles, languages that provide persistence as a basic abstraction have been developed. In this paper, the motivation for orthogonal persistence is reviewed along with the above mentioned design principles. The concepts for integrating programming languages and databases through the persistence abstraction, and their benefits, are given. The technology to support persistence, the achievements, and future directions of persistence research are then discussed."
"In this paper, we propose the Pyramid-Technique, a new indexing method for high-dimensional data spaces. The Pyramid-Technique is highly adapted to range query processing using the maximum metric Lmax. In contrast to all other index structures, the performance of the Pyramid-Technique does not deteriorate when processing range queries on data of higher dimensionality. The Pyramid-Technique is based on a special partitioning strategy which is optimized for high-dimensional data. The basic idea is to divide the data space first into 2d pyramids sharing the center point of the space as a top. In a second step, the single pyramids are cut into slices parallel to the basis of the pyramid. These slices from the data pages. Furthermore, we show that this partition provides a mapping from the given d-dimensional space to a 1-dimensional space. Therefore, we are able to use a B+-tree to manage the transformed data. As an analytical evaluation of our technique for hypercube range queries and uniform data distribution shows, the Pyramid-Technique clearly outperforms index structures using other partitioning strategies. To demonstrate the practical relevance of our technique, we experimentally compared the Pyramid-Technique with the X-tree, the Hilbert R-tree, and the Linear Scan. The results of our experiments using both, synthetic and real data, demonstrate that the Pyramid-Technique outperforms the X-tree and the Hilbert R-tree by a factor of up to 14 (number of page accesses) and up to 2500 (total elapsed time) for range queries."
"The Mentor-lite prototype has been developed within the research project ¡°Architecture, Configuration, and Administration of Large Workflow Management Systems¡± funded by the German Science Foundation (DFG). It has evolved from its predecessor Mentor [1], but aims at a simpler architecture. The main goal of Mentor-lite has been to build a light-weight, extensible, and tailorable workflow management system (WFMS) with small footprint and easy-to-use administration capabilities. Our approach is to provide only kernel functionality inside the workflow engine, and consider system components like history management and worklist management as extensions on top of the kernel. The key point to retain the light-weight nature is that these extensions are implemented as workflows themselves."
"The extensible mark-up language (XML) is gaining widespread use as a format for data exchange and storage on the World Wide Web. Queries over XML data require accurate selectivity estimation of path expressions to optimize query execution plans. Selectivity estimation of XML path expression is usually done based on summary statistics about the structure of the underlying XML repository. All previous methods require an off-line scan of the XML repository to collect the statistics. In this paper, we propose XPathLearner, a method for estimating selectivity of the most commonly used types of path expressions without looking at the XML data. XPathLearner gathers and refines the statistics using query feedback in an on-line manner and is especially suited to queries in Internet scale applications since the underlying XML repository is either inaccessible or too large to be scanned in its entirety. Besides the on-line property, our method also has two other novel features: (a) XPathLearner is workload-aware in collecting the statistics and thus can be more accurate than the more costly off-line method under tight memory constraints, and (b) XPathLearner automatically adjusts the statistics using query feedback when the underlying XML data change. We show empirically the estimation accuracy of our method using several real data sets."
"At the heart of all OLAP or multidimensional data analysis applications is the ability to simultaneously aggregate across many sets of dimensions. Computing multidimensional aggregates is a performance bottleneck for these applications. This paper presents fast algorithms for computing a collection of group bys. We focus on a special case of the aggregation problem - computation of the CUBE operator. The CUBE operator requires computing group-bys on all possible combinations of a list of attributes, and is equivalent to the union of a number of standard group-by operations. We show how the structure of CUBE computation can be viewed in terms of a hierarchy of group-by operations. Our algorithms extend sort-based and hashbased grouping methods with several .optimizations, like combining common operations across multiple groupbys, caching, and using pre-computed group-by8 for computing other groupbys. Empirical evaluation shows that the resulting algorithms give much better performance compared to straightforward meth"
"Flexible methods supporting the data interchange between autonomous information systems are important for today's increasingly heterogeneous enterprise IT infrastructures. Updates, insertions, and deletions of data objects in autonomous information systems often have to trigger data changes in other autonomous systems, even if the distributed systems are not integrated into a global schema. We suggest a solution to this problem based on the propagation and transformation of data using several XML technologies. Our prototype manages dependencies between the schemas of distributed data sources and allows to define and process arbitrary actions on changed data by manipulating all dependent data sources. The prototype comprises a propagation engine that interprets scripts based on a workflow specification language, a data dependency specification tool, a system administration tool, and a repository that stores all relevant information for these tools."
"While the XML Stylesheet Language for Transformations (XSLT) was not designed as a query language, it is well-suited for many query-like operations on XML documents including selecting and restructuring data. Further, it actively fulfills the role of an XML query language in modern applications and is widely supported by application platform software. However, the use of database techniques to optimize and execute XSLT has only recently received attention in the research community. In this paper, we focus on the case where XSL transformations are to be run on XML documents defined as views of relational databases. For a subset of XSLT, we present an algorithm to compose a transformation with an XML view, eliminating the need for the XSLT execution. We then describe how to extend this algorithm to handle several additional features of XSLT, including a proposed approach for handling recursion."
"The cost of a query plan depends on many parameters, such as predicate selectivities and available memory, whose values may not be known at optimization time. Parametric query optimization (PQO) optimizes a query into a number of candidate plans, each optimal for some region of the parameter space. We propose a heuristic solution for the PQO problem for the case when the cost functions may be nonlinear in the given parameters. This solution is minimally intrusive in the sense that an existing query optimizer can be used with minor modifications. We have implemented the heuristic and the results of the tests on the TPCD benchmark indicate that the heuristic is very effective. The minimal intrusiveness, generality in terms of cost functions and number of parameters and good performance (up to 4 parameters) indicate that our solution is of significant practical importance."
"Data integration is frequently required to obtain the full value of data from multiple sources. In spite of extensive research on tools to assist users, data integration remains hard, particularly for users with limited technical proficiency. To address this barrier, we study how much we can do with no user guidance. Our vision is that the user should merely specify two input datasets to be joined and get a meaningful integrated result. It turns out that our vision can be realized if the system can correctly determine the join key, for example based on domain knowledge."
"Editor's note: For this issue's ""From the Editors,"" I invited Robert Gephart of the University of Al-berta to reflect on his observations as a long-serving , award-winning reviewer of qualitative research for A!vII Over the past two and a half years, I have developed a tremendous respect for Bob's keen eye for evaluating qualitative research submissions , and great admiration for the painstaking advice he provides authors about how to improve their work. As a world-renowned qualitative author himself, Bob is in an excellent position to provide observations about how authors might increase the chances of having their qualitative research accepted for publication at AMI In a three-way electronic mail conversation about the challenges and opportunities of qualitative research , Bob, Tom Lee, and I all concluded that many authors with potentially very interesting data sets don't seem to know how to analyze them to their full potential. This is perhaps not surprising, gi ven the clear predominance of quantitative methods and statistics courses over qualitative ones, particularly in North America, as well as the inherently greater subjectivity involved in designing and analyzing qualitative research. As such, we encouraged Bob to provide a bit of a minitutorial-complete with reference citations and examples of high-quality papers that use particular qualitative approaches-in addition to his observations about qualitative research submitted to AMI The result is a longer-than-usual ""From the Edi-tors"" column. but one that we believe is well worth the extra reading time for anyone interested in producing , reviewing, or attempting to coax greater insights from qualitative research. We are fortunate to have someone with Bob's expertise share his observations, and we hope that his thoughts will prove useful to researchers for many years to come. Sara Rynes Incoming Editor I am thankful to Sara for inviting me to write this editorial column encouraging scholars to submit their qualitative research to the Academy of Man-I wish to thank Torn Lee and Sara Rynes for their helpful comments and encouragement in preparing this editorial. 454 agement Journal. Qualitative research is important to AMI Qualitative research is actively sought and supported by the Journal, its editors, and its editorial review board. Alv1Jhas published many qualitative papers. The coveted A/'v1jBest Article Award has been won by three qualitative papers-Gersick (1989), Isabella (1990), and Dutton and Duckerich (1991)-and by one paper that combined qualitative and quantitative methods: Sutton and Rafuclli, (1988). Despite these successes, most ¡­"
"The authors' perspective of database mining as the confluence of machine learning techniques and the performance emphasis of database technology is presented. Three classes of database mining problems involving classification, associations, and sequences are described. It is argued that these problems can be uniformly viewed as requiring discovery of rules embedded in massive amounts of data. A model and some basic operations for the process of rule discovery are described. It is shown how the database mining problems considered map to this model, and how they can be solved by using the basic operations proposed. An example is given of an algorithm for classification obtained by combining the basic rule discovery operations. This algorithm is efficient in discovering classification rules and has accuracy comparable to ID3, one of the best current classifiers. >"
"Recent research addressed the importance of optimizing L2 cache utilization in the design of main memory indexes and proposed the so-called cache-conscious indexes such as the CSB+-tree. However, none of these indexes took account of concurrency control, which is crucial for running the real-world main memory database applications involving index updates and taking advantage of the off-the-shelf multiprocessor systems for scaling up the performance of such applications. Observing that latching index nodes for concurrency control (CC) incurs the so-called coherence cache misses on shared-memory multiprocessors thus limiting the scalability of the index performance, this paper presents an optimistic, latch-free index traversal (OLFIT) CC scheme based on a pair of consistent node read and update primitives. An experiment with various index CC implementations for the B+tree and CSB+-tree shows that the proposed scheme shows the superior scalability on the multiprocessor system as well as the performance comparable to that of the sequential execution without CC on the uniprocessor system."
"Research has investigated mappings among data sources under two perspectives. On one side, there are studies of practical tools for schema mapping generation; these focus on algorithms to generate mappings based on visual specifications provided by users. On the other side, we have theoretical researches about data exchange. These study how to generate a solution - i.e., a target instance - given a set of mappings usually specified as tuple generating dependencies. However, despite the fact that the notion of a core of a data exchange solution has been formally identified as an optimal solution, there are yet no mapping systems that support core computations. In this paper we introduce several new algorithms that contribute to bridge the gap between the practice of mapping generation and the theory of data exchange. We show how, given a mapping scenario, it is possible to generate an executable script that computes core solutions for the corresponding data exchange problem. The algorithms have been implemented and tested using common runtime engines to show that they guarantee very good performances, orders of magnitudes better than those of known algorithms that compute the core as a post-processing step."
"New database applications that require the storage and retrieval of many terabytes of data are reaching the limits for disk-based storage systems, in terms of both cost and scalability. These limits provide a strong incentive for the development of databases that augment disk storage with technologies better suited to large volumes of data. In particular, the seamless incorporation of tape storage into database systems would be of great value. Tape storage is two orders of magnitude more efficient than disk in terms of cost per terabyte and physical volume per terabyte; however, a key problem is that the random access latency of tape is three to four orders of magnitude slower than disk. Thus, to incorporate a tape bulk store in an online storage system, the problem of tape access latency must be solved. One approach to reducing the latency is careful I/O scheduling. The focus of this paper is on efficient random I/O scheduling for tape drives that use a serpentine track layout, such as the Quantum DLT and the IBM 3480 and 3590. For serpentine tape, I/O scheduling is problematic because of the complex relationships between logical block numbers, their physical positions on tape, and the time required for tape positioning between these physical positions. The results in this paper show that our scheduling schemes provide a significant improvement in the latency of random access to serpentine tape."
"PAYOFF IDEA. Different styles of user interfaces can dramatically affect data base capabilities. In an environment comprising many different data bases, the goal is to select one data base management system (DBMS) that provides the best selection of design tools, minimizes development times, and enforces relational rules. This article presents a case study performed at the Hospital of the University of Pennsylvania, in which a test data base was developed for implementation with three DBMSs, each with a distinctly different user and programmer interface."
"Automated recommendation (e.g., personalized product recommendation on an ecommerce web site) is an increasingly valuable service associated with many databases--typically online retail catalogs and web logs. Currently, a major obstacle for evaluating recommendation algorithms is the lack of any standard, public, real-world testbed appropriate for the task. In an attempt to fill this gap, we have created REFEREE, a framework for building recommender systems using ResearchIndex--a huge online digital library of computer science research papers--so that anyone in the research community can develop, deploy, and evaluate recommender systems relatively easily and quickly. Research Index is in many ways ideal for evaluating recommender systems, especially so-called hybrid recommenders that combine information filtering and collaborative filtering techniques. The documents in the database are associated with a wealth of content information (author, title, abstract, full text) and collaborative information (user behaviors), as well as linkage information via the citation structure. Our framework supports more realistic evaluation metrics that assess user buy-in directly, rather than resorting to offline metrics like prediction accuracy that may have little to do with end user utility. The sheer scale of ResearchIndex (over 500,000 documents with thousands of user accesses per hour) will force algorithm designers to make real-world trade-offs that consider performance, not just accuracy. We present our own tradeoff decisions in building an example hybrid recommender called PD-Live. The algorithm uses content-based similarity information to select a set of documents from which to recommend, and collaborative information to rank the documents. PD-Live performs reasonably well compared to other recommenders in ResearchIndex."
"Publish/Subscribe is the paradigm in which users express long-term interests (¡°subscriptions¡±) and some agent ¡°publishes¡± events (e.g., offers). The job of Publish/Subscribe software is to send events to the owners of subscriptions satisfied by those events. For example, a user subscription may consist of an interest in an airplane of a certain type, not to exceed a certain price. A published event may consist of an offer of an airplane with certain properties including price. Each subscription consists of a conjunction of (attribute, comparison operator, value) predicates. A subscription closely resembles a trigger in that it is a long-lived conditional query associated with an action (usually, informing the subscriber). However, it is less general than a trigger so novel data structures and implementations may enable the creation of more scalable, high performance publish/subscribe systems. This paper describes an attempt at the construction of such algorithms and its implementation. Using a combination of data structures, application-specific caching policies, and application-specific query processing our system can handle 600 events per second for a typical workload containing 6 million subscriptions."
We provide a concise yet complete formal definition of the semantics of XPath 1 and summarize efficient algorithms for processing queries in this language. Our presentation is intended both for the reader who is looking for a short but comprehensive formal account of XPath as well as the software developer in need of material that facilitates the rapid implementation of XPath engines.
"We describe SAMOS, an active object-oriented database management system prototype. SAMOS offers a powerful rule definition language, including a small yet powerful set of event definition facilities. It is able to detect primitive and composite events automatically and efficiently. Upon event detection, SAMOS executes rules attached to the occurred events."
"We present the PPOST-architecture (Persistent Parallel Object Store) for main-memory database systems on parallel computers, that is suited for applications with challenging performance requirements. The architecture takes full advantage of parallelism, large main memories and fast switching networks. An important property of this architecture is its excellent scaling behavior."
"ion is both a benefit and a curse for the Semantic Web, especially when classes and individuals are introduced by OWL. The question about whether to implement a knowledge representation as either abstract or concrete is subtle(Smith, 1996). For example, the ¡°Dartmouth School of Art¡± can be thought of as an concrete instance of the class of all schools, or as a abstract class which remains the same regardless of the moving of the physical building or the change of staff. It then becomes unclear what one is referring in statements such as ¡°The Dartmouth School of Art is now specializing in sculpture¡± or ¡°The Dartmouth School of Art has changed its address.¡± This problem is recognized by the OWL ontology group. The OWL documentation mentions both that ¡°in certain contexts something that is obviously a class can itself be considered an instance of something else¡± and ¡°it is very easy to confuse the instance-of relationship with the subclass relationship¡±(Welty et al., 2004). This makes ontology mapping and merging exceedingly difficult. While the ability to divide the world into classes and instances provide description logics with a set of principles, it does not make mapping between what one person considers a class and another considers an instance straightforward. 5.4 The Frame Problem The question of how to represent time in an open world is another question from artificial intelligence that haunts the Semantic Web. RDF attempts to avoid this problem by stating that ¡°does not provide any analysis of time-varying data¡±(Hayes, 2004). Yet, it would seem that any statement about an URI is not meant to last forever, especially as URIs and their contents have a tendency to change. Berners-Lee attempts to avoid this problem in a note ¡°Cool URIs don¡¯t Change,¡±4 in which he notes that the change of a URI damages its ability to be universally linked and have statements made about it. However, despite this principle being made fundamental in new Web standards, it at the current moment does not stand true about the Web and we have no reason to believe that it will soon in the future(Jacobs and Walsh, 2004). There is already a need to make temporally-qualified statements using metadata and ontologies. However, as pointed out by the Frame Problem, the issue of handling assumptions 4http://www.w3.org/Provider/Style/URI about time in artificial intelligence has proven remarkably difficult to formalize (McCarthy and Hayes, 1969). Their example is that if ¡°we had a number of actions to be performed in sequence we would have quite a number of conditions to write down that certain actions do not change the values of certain fluents¡±(McCarthy and Hayes, 1969). There is no agreed upon model of time with properties that are well understood. In fact, there are many theories of time with contradictory properties(Hayes, 1995). 5.5 The Symbol Grounding Problem This problem is stated as ¡°How can the semantic interpretation of a formal symbol system be made intrinsic to the system, rather than just parasitic on the meanings in our heads? How can the meanings of the meaningless symbol tokens, manipulated solely on the basis of their (arbitrary) shapes, be grounded in anything but other meaningless symbols?¡±(Harnad, 1990). One answer is to map it via formal semantics to a model theory. However, although the model may resemble the part of the world that it models, it could also may model it in a limited fashion due to the Knowledge Representation problem. Therefore, it is needed to ¡°ground¡± the symbols in some real world object(Davis et al., 1993). It is difficult to imagine how what this would practically entail, perhaps some form of sensors with direct causal content as Harnad suggests(1990). However, it is not clear that such as direct connection is needed, for even humans do not remain in constant causal contact with their subject matter. In fact, this ability to connect and disconnect our representations with their subject matter is a reason for the origins of intentionality and representations in humans(Smith, 1996). "
"Database management systems (or DBMSs) have been around for decades, and yet are still difficult to use, particularly when trying to identify and fix errors in user programs (or queries). We seek to understand what methods have been proposed to help people debug database queries, and whether these techniques have ultimately been adopted by DBMSs (and users). We conducted an interdisciplinary review of 112 papers and tools from the database, visualisation and HCI communities. To better understand whether academic and industry approaches are meeting the needs of users, we interviewed 20 database users (and some designers), and found surprising results. In particular, there seems to be a wide gulf between users' debugging strategies and the functionality implemented in existing DBMSs, as well as proposed in the literature. In response, we propose new design guidelines to help system designers to build features that more closely match users debugging strategies."
"This paper presents structural recursion as the basis of the syntax and semantics of query languages for semistructured data and XML. We describe a simple and powerful query language based on pattern matching and show that it can be expressed using structural recursion, which is introduced as a top-down, recursive function, similar to the way XSL is defined on XML trees. On cyclic data, structural recursion can be defined in two equivalent ways: as a recursive function which evaluates the data top-down and remembers all its calls to avoid infinite loops, or as a bulk evaluation which processes the entire data in parallel using only traditional relational algebra operators. The latter makes it possible for optimization techniques in relational queries to be applied to structural recursion. We show that the composition of two structural recursion queries can be expressed as a single such query, and this is used as the basis of an optimization method for mediator systems. Several other formal properties are established: structural recursion can be expressed in first-order logic extended with transitive closure; its data complexity is PTIME; and over relational data it is a conservative extension of the relational calculus. The underlying data model is based on value equality, formally defined with bisimulation. Structural recursion is shown to be invariant with respect to value equality."
"System developments and research on parallel query processing have concentrated either on ¡°Shared Everything¡± or ¡°Shared Nothing¡± architectures so far. While there are several commercial DBMS based on the ¡°Shared Disk¡± alternative, this architecture has received very little attention with respect to parallel query processing. A comparison between Shared Disk and Shared Nothing reveals many potential benefits for Shared Disk with respect to parallel query processing. In particular, Shared Disk supports more flexible control over the communication overhead for intra-transaction parallelism, and a higher potential for dynamic load balancing and efficient processing of mixed OLTP/query workloads. We also sketch necessary extensions for transaction management (concurrency/coherency control, logging/recovery) to support intra-transaction parallelism in the Shared Disk environment."
"The current integrated developments in network and computing give rise to a technical infrastructure for the information society which one may variously circumscribe by terms such as ubiquitous computing, telepresence and the network as one giant global database. The paper applies to the network the metaphor of global database, and subsumes the aspects of ubiquity and telepresence under it. It should then be possible to preserve many of the existing database techniques and to concentrate on adjusting these to the network information infrastructure. The paper explores four challenges for adjustment: interoperability due to heterogeneous data repositories, proactivity due to autonomy of data sources, interactiveness due to the need of short-term and task-specific interaction and cooperation, and legacy due to the fitting of old systems to the networked environment. Based on several application projects and exemplary solutions, the paper claims as its experiences that objectorientation provides a natural framework for meeting the challenges, but must also draw on the combined resources of databases, data communications, and software engineering. "
"Abstract. The analysis of web usage has mostly focused on sites composed of conventional static pages. However, huge amounts of information available in the web come from databases or other data collections and are presented to the users in the form of dynamically generated pages. The query interfaces of such sites allow the specification of many search criteria. Their generated results support navigation to pages of results combining cross-linked data from many sources. For the analysis of visitor navigation behaviour in such web sites, we propose the web usage miner (WUM), which discovers navigation patterns subject to advanced statistical and structural constraints. Since our objective is the discovery of interesting navigation patterns, we do not focus on accesses to individual pages. Instead, we construct conceptual hierarchies that reflect the query capabilities used in the production of those pages. Our experiments with a real web site that integrates data from multiple databases, the German SchulWeb, demonstrate the appropriateness of WUM in discovering navigation patterns and show how those discoveries can help in assessing and improving the quality of the site."
"A load, such as a logic network of the TTL type, is connected in parallel across a plurality of direct-current sources designed to maintain a substantially constant operating voltage. Each source includes a control unit which compares the load voltage with a reference level in order to stabilize the output voltage of an associated current generator at that level. If the generator current drops below a certain minimum value, however, a threshold sensor in the control unit raises the reference level up to an amount equaling about twice the maximum divergence possible between the reference levels of different control units, thereby ensuring that all sources contribute simultaneously to the load current."
"Data defined by interpolation is frequently found in new applications   involving geographical concepts, moving objects, and   spatio-temporal data. This data leads to potentially infinite collections of   items, (e.g. the elevation of any point in a map), whose definition is based   on the association of a collection of samples with an interpolation   function. We first argue that the manipulation of the data through direct   access to the samples and interpolation functions easily leads   to cumbersome or inaccurate queries. We therefore suggest hiding the   samples and the interpolation function away from the logical level, and   letting the system manipulate them at the physical level.   We propose to model such data conceptually using infinite relations (e.g.   the map with elevation yields an infinite ternary relation) which can be   manipulated through standard relational query languages (e.g. SQL), with no   mention of the interpolated definition. This approach is simple and   establishes a clear separation between logical and physical levels."
"In this paper, we investigate the approach of using low cost PC cluster to parallelize the computation of iceberg-cube queries. We concentrate on techniques directed towards online querying of large, high-dimensional datasets where it is assumed that the total cube has net been precomputed. The algorithmic space we explore considers trade-offs between parallelism, computation and I/0. Our main contribution is the development and a comprehensive evaluation of various novel, parallel algorithms. Specifically: (1) Algorithm RP is a straightforward parallel version of BUC [BR99]; (2) Algorithm BPP attempts to reduce I/0 by outputting results in a more efficient way; (3) Algorithm ASL, which maintains cells in a cuboid in a skiplist, is designed to put the utmost priority on load balancing; and (4) alternatively, Algorithm PT load-balances by using binary partitioning to divide the cube lattice as evenly as possible."
"A well-known challenge in data warehousing is the efficient incremental maintenance of warehouse data in the presence of source data updates. In this paper, we identify several critical data representation and algorithmic choices that must be made when developing the machinery of an incrementally maintained data warehouse. For each decision area, we identify various alternatives and evaluate them through extensive experiments. We show that picking the right alternative can lead to dramatic performance gains, and we propose guidelines for making the right decisions under different scenarios. All of the issues addressed in this paper arose in our development of WHIPS, a prototype data warehousing system supporting incremental maintenance."
The peer review process is generally acknowledged as central to the advancement of scholarly knowledge. It is also vital to the advancement of individual careers.
"A very large number of data sources on environment, energy, and natural resources are available worldwide. Unfortunately, users usually face several problems when they want to search and use environmental information. In this paper, we analyze these problems. We describe a conceptual analysis of the four major tasks in the production of environmental data, from the technology point of view, and describe the organization of the data that results from these tasks. We then discuss the notion of metainformation and outline an architecture for environmental data systems that formally models metadata and addresses some of the major problems faced by users."
"We describe the Infosphere project, which is building the systems software support for information-driven applications such as digital libraries and electronic commerce. The main technical contribution is the Infopipe abstraction to support information flow with quality of service. Using building blocks such as program specialization, software feedback, domain-specific languages, and personalized information filtering, the Infopipe software generates code and manages resources to provide the specified quality of service with support for composition and restructuring."
"To truly meet the requirements of multimedia database (MMDB) management, an integrated framework for modeling, managing and retrieving various kinds of media data in a uniform way is necessary. MediaLand is an experimental MMDB platform being developed at Microsoft Research Asia for users with different levels of experiences and expertise to manage and search multimedia repositories easily, efficiently, and cooperatively. Key features of MediaLand include a uniform data model for describing all kinds of media objects and their relationships, and a 4-tier architecture based on this data model. In this paper, a multi-paradigm querying approach of MediaLand is presented, in which multimedia queries are processed based on a seamless integration of various existing search approaches. In doing so, MediaLand also offers the feature of ""media independence"" which is analogous to the notion of ""data independence"" from the classic ANSI SPARC standard. By incorporating a rich set of facilities and techniques, MediaLand lays down a good foundation for addressing further research issues, such as multimedia query rewriting, optimization, and presentation."
"We describe the external data manager component of the Lore database system for semistructured data. Lore's external data manager enables dynamic retrieval and integration of data from arbitrary, heterogeneous external sources during query processing. The distinction between Lore-resident and external data is invisible to the user. We introduce a flexible notion of arguments that limits the amount of data fetched from an external source, and we have incorporated optimizations to reduce the number of calls to an external source."
"Data warehouses store large volumes of data which are used frequently by decision support applications. Such applications involve complex queries. Query performance in such an environment is critical because decision support applications often require interactive query response time. Because data warehouses are updated infrequently, it becomes possible to improve query performance by caching sets retrieved by queries in addition to query execution plans. In this paper we report on the design of an intelligent cache manager for sets retrieved by queries called WATCHMAN, which is particularly well suited for data warehousing environment. Our cache manager employs two novel, complementary algorithms for cache replacement and for cache admission. WATCHMAN aims at minimizing query response time and its cache replacement policy swaps out entire retrieved sets of queries instead of individual pages. The cache replacement and admission algorithms make use of a profit metric, which considers for each retrieved set its average rate of reference, its size, and execution cost of the associated query. We report on a performance evaluation based on the TPC-D and Set Query benchmarks. These experiments show that WATCHMAN achieves a substantial performance improvement in a decision support environment when compared to a traditional LRU replacement algorithm."
"Softwaresysteme, die ihre Services an Charakteristika individueller Benutzer anpassen haben sich bereits als effektiver und/oder benutzerfreundlicher als statische Systeme in mehreren Anwendungsdomanen erwiesen. Um solche Anpassungsleistungen anbieten zu konnen, greifen benutzeradaptive Systeme auf Modelle von Benutzercharakteristika zuruck. Der Aufbau und die Verwaltung dieser Modelle wird durch dezidierte Benutzermodellierungskomponenten vorgenommen. Ein wichtiger Zweig der Benutzermodellierungsforschung beschaftigt sich mit der Entwicklung sogenannter ?Benutzermodellierungs-Shells?, d.h. generischen Benutzermodellierungssystemen, die die Entwicklung anwendungsspezifischer Benutzermodellierungskomponenten erleichtern. Die Bestimmung des Leistungsumfangs dieser generischen Benutzermodellierungssysteme und deren Dienste bzw. Funktionalitaten wurde bisher in den meisten Fallen intuitiv vorgenommen und/oder aus Beschreibungen weniger benutzeradaptiver Systeme in der Literatur abgeleitet. In der jungeren Vergangenheit fuhrte der Trend zur Personalisierung im World Wide Web zur Entwicklung mehrerer kommerzieller Benutzermodellierungsserver. Die fur diese Systeme als wichtig erachteten Eigenschaften stehen im krassen Gegensatz zu denen, die bei der Entwicklung der Benutzermodellierungs-Shells im Vordergrund standen und umgekehrt. Vor diesem Hintergrund ist das Ziel dieser Dissertation (i) Anforderungen an Benutzermodellierungsserver aus einer multi-disziplinaren wissenschaftlichen und einer einsatzorientierten (kommerziellen) Perspektive zu analysieren, (ii) einen Server zu entwerfen und zu implementieren, der diesen Anforderungen genugt, und (iii) die Performanz und Skalierbarkeit dieses Servers unter der Arbeitslast kleinerer und mittlerer Einsatzumgebungen gegen die diesbezuglichen Anforderungen zu uberprufen. Um dieses Ziel zu erreichen, verfolgen wir einen anforderungszentrierten Ansatz, der auf Erfahrungen aus verschiedenen Forschungsbereichen aufbaut. Wir entwickeln eine generische Architektur fur einen Benutzermodellierungsserver, die aus einem Serverkern fur das Datenmanagement und modular hinzufugbaren Benutzermodellierungskomponenten besteht, von denen jede eine wichtige Benutzermodellierungstechnik implementiert. "
"XML is rapidly becoming one of the most widely adopted technologies for information exchange and representation. As the use of XML becomes more widespread, we foresee the development of active XML rules, i.e., rules explicitly designed for the management of XML information. In particular, we argue that active rules for XML offer a natural paradigm for the rapid development of innovative e-services. In the paper, we show how active rules can be specified in the context of XSLT, a pattern-based language for publishing XML documents (promoted by the W3C) which is receiving strong commercial support, and Lorel, a query language for XML documents that is quite popular in the research world. We demonstrate, through simple examples of active rules for XSLT and Lorel, that active rules can be effective for the implementation of e-commerce services. We also discuss the various issues that need to be considered in adapting the notion of relational triggers to the XML context."
"In this first article of the regular column on data base standardization activities, I give an overview of topic areas under active development in the formal national and international standardization bodies. I solicit contributions on these active topics so that standardizers and researchers can cooperate in the near term, before irreversible decisions are made, to produce the most useful and highest quality database standards."
"Access control in function granularity is one of the features of many object-oriented databases. In those systems, the users are granted rights to invoke composed functions instead of rights to invoke primitive operations. Although primitive operations are invoked inside composed functions, the users can invoke them only through the granted functions. This achieves access control in abstract operation level. Access control utilizing encapsulated functions, however, easily causes many ""security flaws"" through which malicious users can bypass the encapsulation and can abuse the primitive operations inside the functions. In this paper, we develop a technique to statically detect such security flaws. First, we design a framework to describe security requirements that should be satisfied. Then, we develop an algorithm that syntactically analyzes program code of the functions and determines whether given security requirements are satisfied or not. This algorithm is sound, that is, whenever there is a security flaw, it detects it."
"The Second International Workshop on Advanced Issues of E-Commerce and Web-Based Information Systems (WECWIS 2000) was held at the Crowne Plaza San Jose/Silicon Valley in Milpitas, California on June 8-9, 2000. The purpose of this workshop was to bring together leading practitioners, developers and researchers to explore the challenging technical issues and find feasible solutions for advancing the current state of the art in e-commerce and web-based information systems. In particular, the workshop was interested in the infrastructure issues to facilitate e-commerce and Web-based information systems.WECWIS 2000 was successful. There were three invited talks, one industrial panel discussion and six technical sessions. The keynote speech, ""The global trading web: A strategic vision for the Internet economy,"" was delivered by Dr. Jay M. Tenebaum, VP and Chief Scientist, Commerce One, Inc., on June 8 immediately following the opening remarks by the conference chair. The banquet address, ""Business issues in e-commerce,"" was delivered by Mr. Daniel Druker, General Manager, Hyperion e-Business Division. Finally, a lunch address, ""B2C, B2B, N2N, N2M: Why 2 is so instrumental?"" was delivered by Mr. Mstafa A. Syed, VP of Technology, VertialNet, Inc."
The notion of roll-up dependency (RUD) extends functional dependencies with generalization hierarchies. RUDs can be applied in OLAP and database design. The problem of discovering RUDs in large databases is at the center of this paper. An algorithm is provided that relies on a number of theoretical results. The algorithm has been implemented; results on two real-life datasets are given. The extension of functional dependency (FD) with roll-ups turns out to capture meaningful rules that are outside the scope of classical FD mining. Performance figures show that RUDs can be discovered in linear time in the number of tuples of the input dataset.
"The key driving force behind general-purpose enterprise directory services is for providing a central repository for commonly and widely used information such as users, groups, network service access information and profiles, security information, etc. Acceptance of the Lightweight Directory Access Protocol (LDAP) as an access protocol has facilitated widespread integration of these directory services into the network infrastructure and applications."
"New telecommunication services and mobility networks have introduced databases in telecommunication networks. Compared with traditional use of databases, telecom databases must fulfill very tough requirements on response time, throughput, and availability. ClustRa is a telecom database prototype developed to run on standard workstations interconnected by an ATM switch. To meet the throughput and real-time response requirements, ClustRa is a main memory database with neighbor main, memory logging. Transactions are executed in parallel. To meet the availability requirements, we use a 2-safe replication scheme over two sites with independent failure modes, a novel declustering strategy, early detection of failures with fast takeover, and by on-line self-repair and maintenance. This paper gives an overview of ClustRa and includes a set of performance measurements."
"The Carnot research project [CARN, WOEL93] at MCC was initiated in 1990 with the goal of addressing the problem of logically unifying physically-distributed, enterprisewide, heterogeneous information. A prototype has been implemented that provides services for enterprise modeling and model integration to create au enterprise-wide view, semantic expansion of queries on the view to queries on individual resources, and interresource consistency management. Carnot also includes technology for 3D visualization of large information spaecs, knowledge discovery in databases, and software application design recovery. The Camot prototype software has been used by the sponsors of the Carnot project to develop a number of applications. These applications have included worldtow management, heterogeneous database access, knowledge discovery in large databases, and integrated access to both text databases and structured databases from a single initial query."
"Abstract.The requirements for effective search and management of the WWW are stronger than ever. Currently Web documents are classified based on their content not taking into account the fact that these documents are connected to each other by links. We claim that a page¡¯s classification is enriched by the detection of its incoming links¡¯ semantics. This would enable effective browsing and enhance the validity of search results in the WWW context. Another aspect that is underaddressed and strictly related to the tasks of browsing and searching is the similarity of documents at the semantic level. The above observations lead us to the adoption of a hierarchy of concepts (ontology) and a thesaurus to exploit links and provide a better characterization of Web documents. The enhancement of document characterization makes operations such as clustering and labeling very interesting. To this end, we devised a system called THESUS. The system deals with an initial sets of Web documents, extracts keywords from all pages¡¯ incoming links, and converts them to semantics by mapping them to a domain¡¯s ontology. Then a clustering algorithm is applied to discover groups of Web documents. The effectiveness of the clustering process is based on the use of a novel similarity measure between documents characterized by sets of terms. Web documents are organized into thematic subsets based on their semantics. The subsets are then labeled, thereby enabling easier management (browsing, searching, querying) of the Web. In this article, we detail the process of this system and give an experimental analysis of its results."
The recent article by Gray and Graefe in the Sigmod Record [ 1 ] included a study of B-tree page size and the trade-off between page size and the cost of accessing B-tree data. Its goal was to find the page size that would result in the lowest access cost per record. This insightful analysis showed how increasing page size permitted the B-tree to be traversed faster while increasing the amount of data that needed to be read to perform the traversal. Their analysis captures the trade-off between the cost (in time) of each access and how many accesses are needed to traverse the tree.
"In this paper we introduce generalized projections (G P an extension of duplicateeliminating projections, that capture aggregations, groupbys, duplicate-eliminating projections (distinctand duplicate-preserving projections in a common unified framework. Using G P s we extend well known and simple algorithms for SQL queries that use distinct projections to derive algorithms for queries using aggregations like sum, max, min, count, and avg. We develop powerful query rewrite rules for aggregate queries that unify and extend rewrite rules previously known in the literature. We then illustrate the power of our approach by solving a very practical and important problem in data warehousing: how to answer an aggregate query on base tables using materialized aggregate views (summary"
"As large numbers of text databases have become available on the Internet, it is getting harder to locate the right sources for given queries. In this paper we present gGlOSS, a generalized Glossary-Of-Servers Server, that keeps statistics on the available databases to estimate which databases are the potentially most useful for a given query. gGlOSS extends our previous work, which focused on databases using the boolean model of document retrieval, to cover databases using the more sophisticated vector-space retrieval model. We evaluate our new techniques using real-user queries and 53 databases. Finally, we further generalize our approach by showing how to build a hierarchy of gGlOSS brokers. The top level of the hierarchy is so small it could be widely replicated, even at end-user workstations."
"Kimball suggests creating one database (or data mart) per major business process. Enterprisewide cohesion is accomplished by using another Kimball innovation, a data bus standard. Understanding how these two models are similar and how they differ gives the reader a foundational knowledge of the most basic data warehouse concepts. We will also explore which organizational characteristics are best suited to each approach. Mary Breslin has worked in both user and IT roles and she is currently exploring Capella University's data warehouse from the user side. marybreslin@earthlink.net"
"STREAM is a general-purpose relational Data Stream Management System (DSMS). STREAM supports a declarative query language and flexible query execution plans. It is designed to cope with high data rates and large numbers of continuous queries through careful resource allocation and use, and by degrading gracefully to approximate answers as necessary. A description of language design, algorithms, system design, and implementation as of late 2002 can be found in [3]. The demonstration focuses on two aspects:"
"Parallel database machine architectures have evolved from the use of exotic hardware to a software parallel dataflow architecture based on conventional shared-nothing hardware. These new designs provide impressive speedup and scaleup when processing relational database queries. This paper reviews the techniques used by such systems, and surveys current commercial and research systems."
"Materialized views can provide massive improvements in query processing time, especially for aggregation queries over large tables. To realize this potential, the query optimizer must know how and when to exploit materialized views. This paper presents a fast and scalable algorithm for determining whether part or all of a query can be computed from materialized views and describes how it can be incorporated in transformation-based optimizers. The current version handles views composed of selections, joins and a final group-by. Optimization remains fully cost based, that is, a single ¡°best¡± rewrite is not selected by heuristic rules but multiple rewrites are generated and the optimizer chooses the best alternative in the normal way. Experimental results based on an implementation in Microsoft SQL Server show outstanding performance and scalability. Optimization time increases slowly with the number of views but remains low even up to a thousand."
"Conceptual models or semantic data models were developed to capture the meaning of an application domain as perceived by someone. Moreover, concepts employed in semantic data models have recently been adopted in object-oriented approaches to systems analysis and design. To employ conceptual modeling constructs effectively, their meanings have to be defined rigorously. Often, however, rigorous definitions of these constructs are missing. This situation occurs especially in the case of the relationship construct. Empirical evidence shows that use of relationships is often problematical as a way of communicating the meaning of an application domain. For example, users of conceptual modeling methodologies are frequently confused about whether to show an association between things via a relationship, an entity, or an attribute. Because conceptual models are intended to capture knowledge about a real-world domain, we take the view that the meaning of modeling constructs should be sought in models of reality. Accordingly, we use ontology, which is the branch of philosophy dealing with models of reality, to analyze the meaning of common conceptual modeling constructs. Our analysis provides a precise definition of several conceptual modeling constructs. Based on our analysis, we derive rules for the use of relationships in entity-relationship conceptual modeling. Moreover, we show how the rules resolve ambiguities that exist in current practice and how they can enrich the capacity of an entity-relationship conceptual model to capture knowledge about an application domain."
"An important requirement for multimedia presentations is the ability to compose new multimedia objects from the existing ones using temporal relationships. When compositions of continuous media objects are specified dynamically, the task of displaying these objects poses new challenges. These challenges are addressed in this paper. We show that in the case of a single composite object retrieval, a prefetching technique, simple sliding, provides an approach to reduce latency and buffering requirements. We extend this prefetching technique to the problem of retrieving multiple composite objects simultaneously. This new technique is termed buffered sliding. We consider several variants of the buffered sliding algorithm. A simulationbased study is used to compare their usage pattern of available memory and in determining their relative merits in reducing latency and increasing disk bandwidth utilization."
"Data warehousing and On-Line Analytical Processing (OLAP) are becoming critical components of decision support as advances in technology are improving the ability to manage and retrieve large volumes of data. Data warehousing refers to \a collection of decision support technologies aimed at enabling the knowledge worker (executive, manager, analyst) to make better and faster decisions"" [1]. OLAP refers to the technique of performing complex analysis over the information stored in a data warehouse. It is often used by management analysts and decision makers in a variety of functional areas such as sales and marketing planning. Typically, OLAP queries look for speci c trends and anomalies in the base information by aggregating, ranging, ltering and grouping data in many di erent ways [8]. E cient query processing is a critical requirement for OLAP because the underlying data warehouse is very large, queries are often quite complex, and decision support applications typically require in-"
"Abstract. The rapid growth of the Internet and support for interoperability protocols has increased the number of Web accessible sources, WebSources. Current wrapper mediator architectures need to be extended with a wrapper cost model (WCM) for WebSources that can estimate the response time (delays) to access sources as well as other relevant statistics. In this paper, we present a Web prediction tool (WebPT), a tool that is based on learning using query feedback from WebSources. The WebPT uses dimensions time of day, day, and quantity of data, to learn response times from a particular WebSource, and to predict the expected response time (delay) for some query. Experiment data was collected from several sources, and those dimensions that were significant in estimating the response time were determined. We then trained the WebPT on the collected data, to use the three dimensions mentioned above, and to predict the response time, as well as a confidence in the prediction. We describe the WebPT learning algorithms, and report on the WebPT learning for WebSources. Our research shows that we can improve the quality of learning by tuning the WebPT features, e.g., training the WebPT using a logarithm of the input training data; including significant dimensions in the WebPT; or changing the ordering of dimensions. A comparison of the WebPT with more traditional neural network (NN) learning has been performed, and we briefly report on the comparison. We then demonstrate how the WebPT prediction of delay may be used by a scrambling enabled optimizer. A scrambling algorithm identifies some critical points of delay, where it makes a decision to scramble (modify) a plan, to attempt to hide the expected delay by computing some other part of the plan that is unaffected by the delay. We explore the space of real delay at a WebSource, versus the WebPT prediction of this delay, with respect to critical points of delay in specific plans. We identify those cases where WebPT overestimation or underestimation of the real delay results in a penalty in the scrambling enabled optimizer, and those cases where there is no penalty. Using the experimental data and WebPT learning, we test how good the WebPT is in minimizing these penalties."
"When implementing persistent objects on a relational database, a major performance issue is prefetching data to minimize the number of roundtrips to the database. This is especially hard with navigational applications, since future accesses are unpredictable. We propose using the context in which an object is loaded as a predictor of future accesses, where context can be a stored collection of relationships, a query result, or a complex object. When an object O¡¯s state is loaded, similar state for other objects in O¡¯s context is prefetched. We present a design for maintaining context and using it to guide prefetch. We give performance measurements of its implementation in Microsoft Repository, showing up to a 70% reduction in running time. We describe variations that selectively apply the technique, exploit asynchronous access, and use application-supplied performance hints."
"Object-Relational DBMSs have been receiving a great deal of attention from industry analysts and press as the next generation of database management systems. The motivation for a next generation DBMS is driven by the reality of shortened business cycles. This dynamic environment demands fast, cost-effective, time-to-market of new or modified business processes, services, and products. To support this important business need, the next generation DBMS must: 1. leverage the large investments made in existing relational technology, both in data and skill set; 2. Take advantage of the flexibility, productivity, and performance benefits of OO modeling; and 3. Integrate robust DBMS services for production quality systems. The objective of this article is to provide a brief overview of UniSQL's commercial object-relational database management system."
"This study presents a modified B2B CRM using the Genetic algorithm and Data Mining Techniques to improve decision making. The model classifies consumers into consumers of Repeat and Shop-and-Go. Modified data mining C5.0 and the Genetic algorithm was employed to optimize rules generated by the decision tree algorithm. The findings showed that the proposed model allocates resources effectively to the most profitable customers¡¯ decisions. The output metrics are machine time, calibration graph, and ROC curve. In comparison with the conventional C5.0, k-NN, and Support Vector Machine, the proposed model has greater accuracy of 89.3 percent."
"We propose a multi-resolution transmission mechanism that allows various organizational units of a web document to be transferred and browsed according to the amount of information captured. We define the notion of information content for each individual organizational unit of a web document as an indication of its captured information. The concept of information content is used as a foundation for defining the notion of relative information content which determines the transmission order of various units. Our mechanism allows a web client to explore the more content-bearing portion of a web document earlier so as to be able to terminate browsing a possibly irrelevant document sooner. This scheme is based on our observation that different organizational units of a document contribute to different amount of information to the document. Such a multi-resolution transmission paradigm is particularly useful in mobile web where the wireless bandwidth is a scarce resource and browsing every document in detail would consume the bandwidth unnecessarily. This is becoming more serious when the size of a web document is getting large, such as technical documents. We then present a prototype of the system in Java and CORBA to illustrate its feasibility."
"We propose an indexing technique for the fast retrieval of objects in 2D images based on similarity between their boundary shapes. Our technique is robust in the presence of noise and supports several important notions of similarity including optimal matches irrespective of variations in orientation and/or position. Our method can also handle size-invariant matches using a normalization technique, although optimality is not guaranteed here. We implemented our method and performed experiments on real (hand-written digits) data. Our experimental results showed the superiority of our method compared to search based on sequential scanning, which is the only obvious competitor. The performance gain of our method increases with any increase in the number or the size of shapes."
"Semantic query optimization uses semantic knowledge (i.e., integrity constraints) to transform a query into an equivalent one that may be answered more efficiently. This article proposes a general method for semantic query optimization in the framework of Object-Oriented Database Systems. The method is effective for a large class of queries, including conjunctive recursive queries expressed with regular path expressions and is based on three ingredients. The first is a Description Logic, ODLRE, providing a type system capable of expressing: class descriptions, queries, views, integrity constraint rules and inference techniques, such as incoherence detection and subsumption computation. The second is a semantic expansion function for queries, which incorporates restrictions logically implied by the query and the schema (classes + rules) in one query. The third is an optimal rewriting method of a query with respect to the schema classes that rewrites a query into an equivalent one, by determining more specialized classes to be accessed and by reducing the number of factors. We implemented the method in a tool providing an ODMG-compliant interface that allows a full interaction with OQL queries, wrapping underlying Description Logic representation and techniques to the user."
"With the increasing importance of XML, LDAP directories, and text-based information sources on the Internet, there is an ever-greater need to evaluate queries involving (sub)string matching. In many cases, matches need to be on multiple attributes/dimensions, with correlations between the multiple dimensions. Effective query optimization in this context requires good selectivity estimates. In this paper, we use pruned count-suffix trees (PSTs) as the basic data structure for substring selectivity estimation. For the 1-D problem, we present a novel technique called MO (Maximal Overlap). We then develop and analyze two 1-D estimation algorithms, MOC and MOLC, based on MO and a constraint-based characterization of all possible completions of a given PST. For the k-D problem, we first generalize PSTs to multiple dimensions and develop a space- and time-efficient probabilistic algorithm to construct k-D PSTs directly. We then show how to extend MO to multiple dimensions. Finally, we demonstrate, both analytically and experimentally, that MO is both practical and substantially superior to competing algorithms."
"To benefit from mature database technology RDF stores are built on top of relational databases and SPARQL queries are mapped into SQL. Using a shared-nothing computer cluster is a way to achieve scalability by carrying out query processing on top of large RDF datasets in a distributed fashion. Aiming to this the current paper elaborates on the impact of relational schema design when queries are mapped into Apache Spark SQL. A single triple table, a set of tables resulting from partitioning by predicate, a single wide table covering all properties, and a set of tables based on the application model specification called domain-dependent-schema, are the considered designs. For each of the mentioned approaches, the rows of the corresponding tables are stored in the distributed file system HDFS using the columnar-store Parquet. Experiments using standard benchmarks demonstrate that the single wide property table approach, despite its simplicity, is superior to other approaches. Further experiments demonstrate that this single table approach continues to be attractive even when repartitioning by key (RDF subject) is applied before executing queries."
"Data mining research typically assumes that the data to be analyzed has been identified, gathered, cleaned, and processed into a convenient form. While data mining tools greatly enhance the ability of the analyst to make data-driven discoveries, most of the time spent in performing an analysis is spent in data identification, gathering, cleaning and processing the data. Similarly, schema mapping tools have been developed to help automate the task of using legacy or federated data sources for a new purpose, but assume that the structure of the data sources is well understood. However the data sets to be federated may come from dozens of databases containing thousands of tables and tens of thousands of fields, with little reliable documentation about primary keys or foreign keys.We are developing a system, Bellman, which performs data mining on the structure of the database. In this paper, we present techniques for quickly identifying which fields have similar values, identifying join paths, estimating join directions and sizes, and identifying structures in the database. The results of the database structure mining allow the analyst to make sense of the database content. This information can be used to e.g., prepare data for data mining, find foreign key joins for schema mapping, or identify steps to be taken to prevent the database from collapsing under the weight of its complexity."
"While much recent work has focussed on the performance of transaction systems where individual transactions have deadlines, our research addresses the semantics of data usage in real-time applications and its integration with real-time resource management, in particular, the timeless value of real-time data and the inherent path and not state-based constraints on concurrency control. Central to our research is the idea of similarity which is a reflexive, symmetric relation over the domain of a data object. By exploiting the similarity relation, we propose a class of efficient data-access policies for real-time data objects. We shall also discuss the design of a distributed real-time data-access interface. Our goal is to build a database facility which can support predictable real-time applications involving high-speed communication, information access, and multimedia."
"Semistructured data is not strictly typed like relational or object-oriented data and may be irregular or incomplete. It often arises in practice, e.g., when heterogeneous data sources are integrated or data is taken from the World Wide Web. Views over semistructured data can be used to filter the data and to restructure (or provide structure to) it. To achieve fast query response time, these views are often materialized. This paper proposes an incremental maintenance algorithm for materialized views over semistructured data. We use the graph-based data model OEM and the query language Lorel, developed at Stanford, as the framework for our work. our algorithm produces a set of queries that compute the updates to the view based upon an update of the source. We develop an analytic cost model and compare the cost of executing our incremental maintenance algorithm to that of recomputing the view. We show that for nearly all types of database updates, it is more efficient to apply our incremental maintenance algorithm to the view than to recompute the view from the database, even when there are thousands of updates."
"Inasmuch for speed to customers desires change and large completion that describe day world. To lead technology and operations technology to form general, to achieve competitive advantage and special form design technology is master key to determine nature and form product, and what tolerable quality levels that work fit product to uses, and all of features and preferences determine through design technology. For importance CAD/CAM subject, we introduce in this research that offer primary components to CAM system, and styles this system to achieve details work steps, and details design steps. From within completely program in (AutoCAD) system with details steps to how design transportation to manufacturing operations to series achieve to desired product. With offer conclusions that fitness between CAD and CAM to introduce direction communication between design and manufacturing lead to mistakes reduction to large ratio."
"Exploratory search requires the system to assist the user in comprehending the information space and expressing evolving search intents for iterative exploration and retrieval of information. We introduce interactive intent modeling, a technique that models a user¡¯s evolving search intents and visualizes them as keywords for interaction. The user can provide feedback on the keywords, from which the system learns and visualizes an improved intent estimate and retrieves information. We report experiments comparing variants of a system implementing interactive intent modeling to a control system. Data comprising search logs, interaction logs, essay answers, and questionnaires indicate significant improvements in task performance, information retrieval performance over the session, information comprehension performance, and user experience. The improvements in retrieval effectiveness can be attributed to the intent modeling and the effect on users¡¯ task performance, breadth of information comprehension, and user experience are shown to be dependent on a richer visualization. Our results demonstrate the utility of combining interactive modeling of search intentions with interactive visualization of the models that can benefit both directing the exploratory search process and making sense of the information space. Our findings can help design personalized systems that support exploratory information seeking and discovery of novel information."
"textabstractPerformance of modern hardware increasingly depends on proper utilization of both the memory cache hierarchy and parallel execution possibilities in todays super-scalar CPUs. Recent database research has demonstrated that database system performance severely suffers from poor utilization of these resources. In previous work, we presented join algorithms that strongly accelerate large equi-join by tuning the memory access pattern to match the characteristics of the memory cache subsystem in the benchmark hardware.    In order to make such algorithms applicable in database systems that run on a wide variety of platforms, we now present a calibration tool that automatically extracts the relevant parameters about the memory subsystem from any hardware. Exhaustive experiments with join-queries demonstrate how a database system equipped with this calibrator can automatically tune memory-conscious database algorithms to their optimal settings.    Once memory access is optimized, CPU resource usage becomes crucial for database performance. We demonstrate how CPU resource usage can be improved by using appropriate implementation techniques. Join experiments with the Monet database system on various hardware platforms confirm that combining memory and CPU optimization can lead to almost an order of magnitude of performance improvement on modern processors."
"Consider a database that represents information about moving objects and their location. For example, for a database representing the location of taxi-cabs a typical query may be: retrieve the free cabs that are currently within 1 mile of 33 N. Michigan Ave., Chicago (to pick-up a customer); or for a trucking company database a typical query may be: retrieve the trucks that are currently within 1 mile of truck ABT312 (which needs assistance); or for a database representing the current location of objects in a battlefield a typical query may be: retrieve the friendly helicopters that are in a given region, or, retrieve the friendly helicopters that are expected to enter the region within the next 10 minutes. The queries may originate from the moving objects, or from stationary users. We will refer to applications with the above characteristics as moving-objects-database (MOD) applications, and to queries as the ones mentioned above as MOD queries."
"In some database applications the traditional approach of seerializability, in which transactions appear to execute atomically and in isolation on a consistent database state, fails to satisfy performance requirements. Although many researchers have investigated the process of decomposing transactions into steps to increase concurrency, such research typically focuses on providing algorithms necessary to implement a decomposition supplied by the database application developer and pays relatively little attention to what constitutess a desirable decomposition or how the developer should obtain one. We focus onthe decomposition itself. A decomposition generates proof obligations whose descharge ensures desirable properties with respect to the original collection of transactions. We introduce the notion of semantic histories to formulate and prove the necessary properties, and the notion of successor sets to describe efficiently the correct interleavings of steps. The successor set constraints use information about conflicts between steps so as to take full advantage of conflict serializability at the level of steps. We propose a mechanism based on two-phase locking to generate correct stepwise serializable histories."
"The OOPSLA '97 Workshop on Experiences Using Object Data Management in the Real-World was held at the Cobb Galleria Centre in Atlanta, Georgia on Monday 6 October 1997. This report summarises some of the commercial case-study presentations made by workshop participants."
"EAEcient support for set-valued attributes is likely to grow in importance as object-relational database systems, which either support set-valued attributes or propose to do so soon, begin to replace their purely relational predecessors. One of the most interesting and challenging operations on set-valued attributes is the set containment join, because it provides a concise and elegant way to express otherwise complex queries. Unfortunately, evaluating these joins is diAEcult, and naive approaches lead to algorithms that are very expensive. In this paper, we develop a new partition based algorithm for set containment joins: the Partitioning Set Join Algorithm (PSJ), which uses a replicating multilevel partitioning scheme based on a combination of set elements and signatures. We present a detailed performance study with a complete implementation in the Paradise object-relational database system. Our results show that PSJ outperforms previously proposed set join algorithms over a wide range of data sets."
"Query optimizers often limit the search space for join orderings, for example by excluding Cartesian products in subplans or by restricting plan trees to left-deep vines. Such exclusions are widely assumed to reduce optimization effort while minimally affecting plan quality. However, we show that searching the complete space of plans is more affordable than has been previously recognized, and that the common exclusions may be of little benefit.We start by presenting a Cartesian product optimizer that requires at most a few seconds of workstation time to search the space of bushy plans for products of up to 15 relations. Building on this result, we present a join-order optimizer that achieves a similar level of performance, and retains the ability to include Cartesian products in subplans wherever appropriate. The main contribution of the paper is in fully separating join-order enumeration from predicate analysis, and in showing that the former problem in particular can be solved swiftly by novel implementation techniques. A secondary contribution is to initiate a systematic approach to the benchmarking of join-order optimization, which we apply to the evaluation of our method."
"Aqua is a system for providing fast, approximate answers to aggregate queries, which are very common in OLAP applications. It has been designed to run on top of any commercial relational DBMS. Aqua precomputes synopses (special statistical summaries) of the original data and stores them in the DBMS. It provides approximate answers along with quality guarantees by rewriting the queries to run on these synopses. Finally, Aqua keeps the synopses up-to-date as the database changes, using fast incremental maintenance techniques."
"Pat is an IBM Fellow, an ACM SIGMOD Innovations Award recipient, and a member of the National Academy of Engineering. Her PhD is from Harvard University. So, Pat, welcome! Thank you very much. Pat, System R and INGRES showed the nay-sayers that it was possible to build a rational database management system with reasonable performance. As part of the early System R team, you were there at the birth of an industry. What were the biggest surprises that you had while building System R? "
"We present WSQ/DSQ (pronounced ¡°wisk-disk¡±), a new approach for combining the query facilities of traditional databases with existing search engines on the Web. WSQ, for Web-Supported (Database) Queries, leverages results from Web searches to enhance SQL queries over a relational database. DSQ, for Database-Supported (Web) Queries, uses information stored in the database to enhance and explain Web searches. This paper focuses primarily on WSQ, describing a simple, low-overhead way to support WSQ in a relational DBMS, and demonstrating the utility of WSQ with a number of interesting queries and results. The queries supported by WSQ are enabled by two virtual tables, whose tuples represent Web search results generated dynamically during query execution. WSQ query execution may involve many high-latency calls to one or more search engines, during which the query processor is idle. We present a lightweight technique called asynchronous iteration that can be integrated easily into a standard sequential query processor to enable concurrency between query processing and multiple Web search requests. Asynchronous iteration has broader applications than WSQ alone, and it opens up many interesting query optimization issues. We have developed a prototype implementation of WSQ by extending a DBMS with virtual tables and asynchronous iteration; performance results are reported."
"We propose an novel method of computing and storing DataCubes. Our idea is to use Bayesian Networks, which can generate approximate counts for any query combination of attribute values and ¡°don¡¯t cares.¡± A Bayesian network represents the underlying joint probability distribution of the data that were used to generate it. By means of such a network the proposed method, NetCube, exploits correlations among attributes. Our proposed preprocessing algorithm scales linearly on the size of the database, and is thus scalable; it is also parallelizable with a straightforward parallel implementation. Moreover, we give an algorithm to estimate counts of arbitrary queries that is fast ( constant on the database size). Experimental results show that NetCubes have fast generation and use (a few"
"We have been developing a mobile passenger support system for public transport. Passengers can make their travel plans and purchase necessary tickets by accessing databases via the system. After starting the travel, a mobile terminal checks the travel schedule of its user by accessing several databases and gathering various kinds of information. In this application field, many kinds of data must be handled. Examples of such data are route information, fare information, area map, station map, planned operation schedule, real-time operation schedule, vehicle facilities and so on. Depending on the user's situation, different information should be supplied and personalized. In this paper, we propose a new mechanism to support passengers using the multi-channel data communication environments. On the other hand, transport systerns can gather information about situations and demands of users and modify their services offered for the users. We also describe a prototype system developed for visually handicapped passengers and the results of tests in an actual railway station."
"This paper proposes a storage management scheme for disk arrays, named hot mirroring. In this scheme, storage space is partitioned into two regions. One is the mirrored region, which is characterized by high performance and low storage efficiency. The other is the RAID5 region, which is characterized by low performance and high storage efficiency. Hot data blocks are stored in the former area, while cold blocks are stored in the latter. In addition, mirrored pairs and RAID5 stripes are orthogonally laid out, through which the performance degradation during rebuilding is minimized. Hot block clustering in hot mirroring achieves higher performance than conventional RAID5 arrays. The potential of hot mirroring is examined through extensive simulation."
"This paper investigates the use of sequences of system calls for classifying intrusions and faults induced by privileged processes in Unix. Classification is an essential capability for responding to an anomaly (attack or fault), since it gives the ability to associate appropriate responses to each anomaly type. Previous work using the well known dataset from the University of New Mexico (UNM) has demonstrated the usefulness of monitoring sequences of system calls for detecting anomalies induced by processes corresponding to several Unix Programs, such as sendmail, lpr, ftp, etc. Specifically, previous work has shown that the Anomaly Count of a running process, i.e., the number of sequences spawned by the process which are not found in the corresponding dictionary of normal activity for the Program, is a valuable feature for anomaly detection. To achieve Classification, in this paper we introduce the concept of Anomaly Dictionaries, which are the sets of anomalous sequences for each type of anomaly. It is verified that Anomaly Dictionaries for the UNM's sendmail Program have very little overlap, and can be effectively used for Anomaly Classification. The sequences in the Anomalous Dictionary enable a description of Self for the Anomalies, analogous to the definition of Self for Privileged Programs given by the Normal Dictionaries. The dependence of Classification Accuracy with sequence length is also discussed. As a side result, it is also shown that a hybrid scheme, combining the proposed classification strategy with the original Anomaly Counts can lead to a substantial improvement in the overall detection rates for the sendmail dataset. The methodology proposed is rather general, and can be applied to any situation where sequences of symbols provide an effective characterization of a phenomenon."
"Summarizing topological relations is fundamental to many spatial applications including spatial query optimization. In this paper, we present several novel techniques to effectively construct cell density based spatial histograms for range (window) summarizations restricted to the four most important topological relations: contains, contained, overlap, and disjoint. We first present a novel framework to construct a multiscale histogram composed of multiple Euler histograms with the guarantee of the exact summarization results for aligned windows in constant time. Then we present an approximate algorithm, with the approximate ratio 19/12, to minimize the storage spaces of such multiscale Euler histograms, although the problem is generally NP-hard. To conform to a limited storage space where only k Euler histograms are allowed, an effective algorithm is presented to construct multiscale histograms to achieve high accuracy. Finally, we present a new approximate algorithm to query an Euler histogram that cannot guarantee the exact answers; it runs in constant time. Our extensive experiments against both synthetic and real world datasets demonstrated that the approximate multiscale histogram techniques may improve the accuracy of the existing techniques by several orders of magnitude while retaining the cost efficiency, and the exact multiscale histogram technique requires only a storage space linearly proportional to the number of cells for the real datasets."
"Introduction As the Internet has become an essential part of everyday life, hundreds of millions of users now connect to the Internet. At the same time, more resource-hungry and performance-sensitive applications have emerged. Expectations of scalability and performance have made caching and replication common features of the infrastructure of the Web. By directing the workload away from possibly overloaded origin Web servers, Web caching and replication address Web performance and scalability from the client side and the server side, respectively. Caching stores a copy of data close to the data consumer (e.g., in a Web browser) to allow faster data access than if the content had to be retrieved from the origin server. Replication, on the other hand, creates and maintains distributed copies of content under the control of content providers. This is helpful because client requests can then be sent to the nearest and least-busy server. Moreover, value-added services, such as virus checking, Web page language translation, and automatic content adaptation for small handheld devices can be developed upon this platform. This book, by two leading researchers at AT&T Labs, Michael Rabinovich and Oliver Spatscheck, presents the state-of-the-art in Web caching and replication from and for both industry and academic research."
"Recent studies have shown that cache-conscious indexes outperform conventional main memory indexes. Cache-conscious indexes focus on better utilization of each cache line for improving search performance of a single lookup. None has exploited cache spatial and temporal locality between consecutive lookups. We show that conventional indexes, even ""cache-conscious"" ones, suffer from significant cache thrashing between accesses. Such thrashing can impact the performance of applications such as stream processing and query operations such as index-nested-loops join."
"We introduce a new model of similarity of time sequences that captures the intuitive notion that two sequences should be considered similar if they have enough non-overlapping time-ordered pairs of subsequences thar are similar. The model allows the amplitude of one of the two sequences to be scaled by any suitable amount and its offset adjusted appropriately. Two subsequences are considered similar if one can be enclosed within an envelope of a specified width drawn around the other. The model also allows non-matching gaps in the matching subsequences. The matching subsequences need not be aligned along the time axis. Given this model of similarity, we present fast search techniques for discovering all similar sequences in a set of sequences. These techniques can also be used to find all (sub)sequences similar to a given sequence. We applied this matching system to the U.S. mutual funds data and discovered interesting matches."
"PAPER NO. 1077 The focus of this paper is on the characterization of the skewness of an attribute-value distribution and on the extrapolations for interesting parameters. We provide eeective schemes for obtaining estimates about either its statistics or subsets/supersets of the relation. We assume an 80/20 law, and speciically, a p=(1 ? p) law. This law gives a distribution which is commonly known in the fractals literature as`multifractal'. We show how to estimate p from the given information ((rst few multiplicities, and a few moments), and present the results of our experimentations on real data. Our results demonstrate that schemes based on our multifractal assumption consistently outperforms those schemes based on the uniformity assumption, which are commonly used in current DBMSs. Moreover, our schemes can be used to provide estimates for supersets of a relation, which the uniformity assumption based schemes can not not provide at all."
"In this paper, we present an eAEcient method, called iDistance, for K-nearest neighbor (KNN) search in a high-dimensional space. iDistance partitions the data and selects a reference point for each partition. The data in each cluster are transformed into a single dimensional space based on their similarity with respect to a reference point. This allows the points to be indexed using a B-tree structure and KNN search be performed using onedimensional range search. The choice of partition and reference point provides the iDistance technique with degrees of freedom most other techniques do not have. We describe how appropriate choices here can e ectively adapt the index structure to the data distribution. We conducted extensive experiments to evaluate the iDistance technique, and report results demonstrating its e ectiveness."
"In the mobile wireless computing environment of the future a large number of users equipped with low powered palm-top machines will query databases over the wireless communication channels. Palmtop based units will often be disconnected for prolonged periods of time due to the battery power saving measures; palmtops will also frequencly relocate between different cells and connect to different data servers at different times. Caching of frequently accessed data items will be an important technique that will reduce contention on the narrow bandwidth wireless channel. However, cache invalidation strategies will be severely affected by the disconnection and mobility of the clients. The server may no longer know which clients are currently residing under its cell and which of them are   currently on. We propose a taxonomy of different cache invalidation strategies and study the impact of client's disconnection times on their performance. We determine that for the units which are often disconnected (sleepers) the best cache invalidation strategy is based on signatures previously used for efficient file comparison. On the other hand, for units which are connected most of the time (workaholics), the best cache invalidation strategy is based on the periodic broadcast of changed data items."
"S3 is the prototype of a database system supporting the management and similarity retrieval of industrial CAD parts. The major goal of the system is to reduce the cost for developing and producing new parts by maximizing the reuse of existing parts. S3 supports the following three types of similarity queries: query by example (of an existing part in the database), query by sketch and thematic similarity query. S3 is an object-oriented system offering an adequate graphical user interface. On top of providing various state-of-the-art algorithms and index structures for geometry-based similarity retrieval, it is an excellent testbed for developing and testing new similarity algorithms and index structures."
"The strength of commercial query optimizers like DB2 comes from their ability to select an optimal order by generating all equivalent reorderings of binary operators. However, there are no known methods to generate all equivalent reorderings for a SQL query containing joins, outer joins, and groupby aggregations. Consequently, some of the reorderings with significantly lower cost may be missed. Using hypergraph model and a set of novel identities, we propose a method to reorder a SQL query containing joins, outer joins, and groupby aggregations. While these operators are sufficient to capture the SQL semantics, it is during their reordering that we identify a powerful primitive needed for a dbms. We report our findings of a simple, yet fundamental operator, generalized selection, and demonstrate its power to solve the problem of reordering of SQL queries containing joins, outer joins, and groupby aggregations."
"DB-Prism is an integrated data warehouse system developed for distributed financial and management controlling (data collection, processing, and reporting) at Deutsche Bank. It combines finegranular availability of historical data with highactuality reporting and planning facilities. Major components of interest include an OLAP system in the Terabyte range, and a meta database responsible for the whole process from heterogeneous data selection to individual OLAP report positions and back via drill-through to the individual business activity. For these purposes, control workbenches have been developed both at the user ¨Clevel and at the metadata level."
"XML is widely recognized as the data interchange standard for tomorrow, because of its ability to represent data from a wide variety sources. Hence, XML is likely to be the format through which data from multiple sources is integrated.In this paper we study the problem of integrating XML data sources through correlations realized as join operations. A challenging aspect of this operation is the XML document structure. Two documents might convey approximately or exactly the same information but may be quite different in structure. Consequently approximate match in structure, in addition to, content has to be folded in the join operation. We quantify approximate match in structure and content using well defined notions of distance. For structure, we propose computationally inexpensive lower and upper bounds for the tree edit distance metric between two trees. We then show how the tree edit distance, and other metrics that quantify distance between trees, can be incorporated in a join framework. We introduce the notion of reference sets to facilitate this operation. Intuitively, a reference set consists of data elements used to project the data space. We characterize what constitutes a good choice of a reference set and we propose sampling based algorithms to identify them. This gives rise to a variety of algorithmic approaches for the problem, which we formulate and analyze. We demonstrate the practical utility of our solutions using large collections of real and synthetic XML data sets."
"Effective support for XML query languages is becoming increasingly important with the emergence of new applications that access large volumes of XML data. All existing proposals for querying XML (e.g., XQuery) rely on a pattern-specification language that allows path navigation and branching through the XML data graph in order to reach the desired data elements. Optimizing such queries depends crucially on the existence of concise synopsis structures that enable accurate compile-time selectivity estimates for complex path expressions over graph-structured XML data. In this paper, We introduce a novel approach to building and using statistical summaries of large XML data graphs for effective path-expression selectivity estimation. Our proposed graph-synopsis model (termed XSKETCH) exploits localized graph stability to accurately approximate (in limited space) the path and branching distribution in the data graph. To estimate the selectivities of complex path expressions over concise XSKETCH synopses, we develop an estimation framework that relies on appropriate statistical (uniformity and independence) assumptions to compensate for the lack of detailed distribution information. Given our estimation framework, we demonstrate that the problem of building an accuracy-optimal XSKETCH for a given amount of space is ????-hard, and propose an efficient heuristic algorithm based on greedy forward selection. Briefly, our algorithm constructs an XSKETCH synopsis by successive refinements of the label-split graph, the coarsest summary of the XML data graph. Our refinement operations act locally and attempt to capture important statistical correlations between data paths. Extensive experimental results with synthetic as well as real-life data sets verify the effectiveness of our approach. To the best of our knowledge, ours is the first work to address this timely problem in the most general setting of graph-structured data and complex (branching) path expressions."
"Interviewing Stonebraker is Margo Seltzer, one of the founders of Sleepycat Software, makers of Berkeley DB, a popular embedded database engine now owned by Oracle. Seltzer now spends most of her time teaching and doing research at Harvard, where she is full professor of computer science. She was kind enough to lend us her time and travel down the Charles River to speak with Stonebraker, her former Ph.D. advisor, at MIT¡¯s striking Stata Center. "
"Although there are many applications where an object-oriented data model is a good way of representing and querying data, current object database systems are unable to handle objects whose attributes are uncertain. In this article, we extend previous work by Kornatzky and Shimony to develop an algebra to handle object bases with uncertainty. We propose concepts of consistency for such object bases, together with an NP-completeness result, and classes of probabilistic object bases for which consistency is polynomially checkable. In addition, as certain operations involve conjunctions and disjunctions of events, and as the probability of conjunctive and disjunctive events depends both on the probabilities of the primitive events involved as well as on what is known (if anything) about the relationship between the events, we show how all our algebraic operations may be performed under arbitrary probabilistic conjunction and disjunction strategies. We also develop a host of equivalence results in our algebra, which may be used as rewrite rules for query optimization. Last but not least, we have developed a prototype probabilistic object base server on top of ObjectStore. We describe experiments to assess the efficiency of different possible rewrite rules."
"In the mobile wireless computing environment of the future a large number of users equipped with low powered palm-top machines will query databases over the wireless communication channels. Palmtop based units will often be disconnected for prolonged periods of time due to the battery power saving measures; palmtops will also frequencly relocate between different cells and connect to different data servers at different times. Caching of frequently accessed data items will be an important technique that will reduce contention on the narrow bandwidth wireless channel. However, cache invalidation strategies will be severely affected by the disconnection and mobility of the clients. The server may no longer know which clients are currently residing under its cell and which of them are   currently on. We propose a taxonomy of different cache invalidation strategies and study the impact of client's disconnection times on their performance. We determine that for the units which are often disconnected (sleepers) the best cache invalidation strategy is based on signatures previously used for efficient file comparison. On the other hand, for units which are connected most of the time (workaholics), the best cache invalidation strategy is based on the periodic broadcast of changed data items."
"My purpose here at this conference is to provide a background, first for meetings like this on subjects dealing with computers, and second, for this particular meeting. My qualifications for keynoting are, I think, as good as those of anyone here: as far as this particular meeting is concerned, I am not now directly engaged in working on computers of the type that we are going to discuss; and the organization that I represent, the Bell Telephone Laboratories, is not in the business of making such computers. So I speak as a relatively innocent bystander."
"Component-based approaches are becoming more and more popular to support Internet-based application development. Different component modeling approaches, however, can be adopted, obtaining different abstraction levels (either conceptual or operational). In this paper we present a component-based architecture for the design of e-applications, and discuss the concept of wrapper components as building blocks for the development of e-services, where these services are based on legacy systems. We discuss their characteristics and their applicability in Internet-based application development."
"Many database applications require the storage and manipulation of different versions of data objects. To satisfy the diverse needs of these applications, current database systems support versioning at a very low level. This article demonstrates that application-independent versioning can be supported at a significantly higher level. In particular, we extend the EXTRA data model and EXCESS query language so that configurations can be specified conceptually and non-procedurally. We also show how version sets can be viewed multidimensionally, thereby allowing configurations to be expressed at a higher level of abstraction. The resulting model integrates and generalizes ideas in CAD systems, CASE systems, and temporal databases."
"Sensor devices and embedded processors are becoming ubiquitous. Their limited resources (CPU, memory and/or communication bandwidth and power) pose some interesting challenges. We need both powerful and concise ""languages"" to represent the important features of the data, which can (a) adapt and handle arbitrary periodic components, including bursts, and (b) require little memory and a single pass over the data."
"A large number of index structures for high-dimensional data have been proposed previously. In order to tune and compare such index structures, it is vital to have efficient cost prediction techniques for these structures. Previous techniques either assume uniformity of the data or are not applicable to high-dimensional data. We propose the use of sampling to predict the number of accessed index pages during a query execution. Sampling is independent of the dimensionality and preserves clusters which is important for representing skewed data. We present a general model for estimating the index page layout using sampling and show how to compensate for errors. We then give an implementation of our model under restricted memory assumptions and show that it performs well even under these constraints. Errors are minimal and the overall prediction time is up to two orders of magnitude below the time for building and probing the full index without sampling."
"In this paper, I describe first the background behind the development of the original ARIES recovery method, and its significant impact on the commercial world and the research community. Next, I provide a brief introduction to the various concurrency control and recovery methods in the ARIES family of algorithms. Subsequently, I discuss some of the recent developments affecting the transaction management area and what these mean for the future. In ARIES, the concept of repeating history turned out to be an important paradigm. As I examine where transaction management is headed in the world of the internet, I observe history repeating itself in the sense of requirements that used to be considered significant in the mainframe world (e.g., performance, availability and reliability) now becoming important requirements of the broader information technology community as well."
"This paper describes how database systems can use and exploit a cost-effective active storage hierarchy. By active storage hierarchy we mean a database system that uses all storage media (i.e. optical, tape, and disk) to store and retrieve data and not just disk. We describe and emphasize the active part, whereby all storage types are used to store raw data that is converted to strategic business information. We describe an evolution to the Data Warehouse concept, called Atomic Data Store, whereby atomic data is stored in the database system. Atomic data is defined as storing all the historic data values and executing queries against the historic queries. We also describe a Data Warehouse information collection, flow and central data store Hub-and-Spoke architecture, used to feed data into Data Marts. We also describe a commercial product; StorHouse/Relational Manager (RM). RM is a commercial relational database system that executes SQL queries directly against data stored on the storage hierarchy (i.e. tape, optical, disk). We conclude with a brief overview of a real world AT&T Call Detail Warehouse (CDW) case study. 1.0 Introduction Commercial Database Management Systems (DBMS) have evolved and been developed to diverse and ubiquitous range of applications. DBMS have been based on hierarchical, network, relational, objectoriented and the new emerging object/relational database model. With few exceptions these database systems and applications primarily use disk media as their storage. Hierarchical Storage Management (HSM) is used by some of these applications to exploit some of the benefits of cost-effective optical storage systems. We propose and analyze that database systems use and exploit a complete active storage hierarchy (i.e. tape, optical, and disk). The key proposal is that active data be also stored, queried and analyzed on tape farm libraries and optical jukeboxes. Figure 1 shows the cost, performance, size and reliability considerations. In this paper, we use the term active storage hierarchy when (say SQL) queries execute against data stored on diverse media."
"From the standpoint of supporting human-centered discovery of knowledge, the present-day model of mining association rules suffers from the following serious shortcomings: (i) lack of user exploration and control, (ii) lack of focus, and (iii) rigid notion of relationships. In effect, this model functions as a black-box, admitting little user interaction in between. We propose, in this paper, an architecture that opens up the black-box, and supports constraint-based, human-centered exploratory mining of associations. The foundation of this architecture is a rich set of constraint constructs, including domain, class, and SQL-style aggregate constraints, which enable users to clearly specify what associations are to be mined. We propose constrained association queries as a means of specifying the constraints to be satisfied by the antecedent and consequent of a mined association."
"In this paper, we present the results that we have obtained by comparing and testing three well-known database middleware solutions. We have analyzed their features related to global catalog and location transparency, transaction management, DML and DDL operations, SQL-dialects mask, referential integrity, security, scalability, supported data sources and platforms, query optimization, and performance. In particular, we have adapted and implemented the AS3AP benchmark to exhaustively evaluate the performance of the products."
"Approximately every five years, a group of database researchers meet to do a self-assessment of our community, including reflections on our impact on the industry as well as challenges facing our research community. This report summarizes the discussion and conclusions of the 9th such meeting, held during October 9-10, 2018 in Seattle."
"Oracle XML DB Repository is a virtual file system which displayed with file directory format,This open protocol of XML storage access method,can well support the design of knowledge base hierarchy,but also easy to manually manage documents.Therefore,the Operation and Maintenance Services of Information Systems using this hierarchical structure to store the information base,so as to ensure that all types of resources stored classification,and also conducive to all kinds of manual retrieval of resources.In addition,Oracle XML DB provides the security control mechanism based on ACLs(access control lists)to all resources."
"Statistical approaches to processing natural language text have become dominant in recent years. This foundational text is the first comprehensive introduction to statistical natural language processing (NLP) to appear. The book contains all the theory and algorithms needed for building NLP tools. It provides broad but rigorous coverage of mathematical and linguistic foundations, as well as detailed discussion of statistical methods, allowing students and researchers to construct their own implementations. The book covers collocation finding, word sense disambiguation, probabilistic parsing, information retrieval, and other applications."
We address the problem of finding parallel plans for SQL queries using the two-phase approach of join ordering followed by parallelization. We focus on the parallelization phase and develop algorithms for exploiting pipelined parallelism. We formulate parallelization as scheduling a weighted operator tree to minimize response time. Our model of response time captures the fundamental tradeoff between parallel execution and its communication overhead. We assess the quality of an optimization algorithm by its performance ratio which is the ratio of the response time of the generated schedule to that of the optimal. We develop fast algorithms that produce near-optimal schedules the performance ratio is extremely close to 1 on the average and has a worst case bound of about 2 for many cases.
"DataMine is a statistical database mining system with strong emphasis on interactiveness and nice graphical representation of information produced. It also supports an offline mode of discovery, and provides an extensive API which allows users to write ""mining applications"" just as easily as routine database applications, The central idea is to perform discovery with a ""human in the loop"" guiding the system using his initial hypothesis and the feedback from the system. Users can pose a rule-query against a rulebase and the system can generate all rules matching their query. The rulebase could either be pregenerated (using offline mode) or could be realized in real-time as the discovery progresses.Rules generated by the system are of the form:Body -&gt; Consequentwhere Body is a conjunction of the elementary predicates of the form (A=a), where A is an attribute and a is a value from the attribute domain of A. Consequent is a single elementary predicate. Each rule can have several parameters like support, confidence, atypicality, color etc. (the definitions have been left out) which can also be used by the user in framing the rule query.For continuous attributes, the system also allows the user some control in deciding how they are discretized. It also allows for the creation of extra attributes at run time which can then be used in queries like the rest."
"Abstract. In meta-searchers accessing distributed Web-based information repositories, performance is a major issue. Efficient query processing requires an appropriate caching mechanism. Unfortunately, standard page-based as well as tuple-based caching mechanisms designed for conventional databases are not efficient on the Web, where keyword-based querying is often the only way to retrieve data. In this work, we study the problem of semantic caching of Web queries and develop a caching mechanism for conjunctive Web queries based on signature files. Our algorithms cope with both relations of semantic containment and intersection between a query and the corresponding cache items. We also develop the cache replacement strategy to treat situations when cached items differ in size and contribution when providing partial query answers. We report results of experiments and show how the caching mechanism is realized in the Knowledge Broker system."
The database research community prides itself on scalable technologies. Yet database systems traditionally do not excel on one important scalability dimension: the degree of distribution. This limitation has hampered the impact of database technologies on massively distributed systems like the Internet.
"We introduce a new database object called Cache Table that enables persistent caching of the full or partial content of a remote database table. The content of a cache table is either defined declaratively and populated in advance at setup time, or determined dynamically and populated on demand at query execution time. Dynamic cache tables exploit the characteristics of typical transactional web applications with a high volume of short transactions, simple equality predicates, and 3-4 way joins. Based on federated query processing capabilities, we developed a set of new technologies for database caching: cache tables, ""Janus"" (two-headed) query execution plans, cache constraints, and asynchronous cache population methods. Our solution supports transparent caching both at the edge of content-delivery networks and in the middle-tier of an enterprise application infrastructure, improving the response time, throughput and scalability of transactional web applications."
"A view is a derived relation defined in terms of base (stored) relations. A view can be materialized by storing the tuples of the view in the database. A materialized view provides fast access to data; the speed difference is critical in applications where the query rate is high and the views are complex or over data in remote databases, so that it is not feasible to recompute the view for every query."
"Some significant progress related to multidimensional data analysis has been achieved in the past few years, including the design of fast algorithms for computing datacubes, selecting some precomputed group-bys to materialize, and designing efficient storage structures for multidimensional data. However, little work has been carried out on multidimensional query optimization issues. Particularly the response time (or evaluation cost) for answering several related dimensional queries simultaneously is crucial to the OLAP applications. Recently, Zhao et al. first exploited this problem by presenting three heuristic algorithms. In this paper we first consider in detail two cases of the problem in which all the queries are either hash-based star joins or index-based star joins only. In the case of the hash-based star join, we devise a polynomial approximation algorithm which delivers a plan whose evaluation cost is $ O(n^{\epsilon }$) times the optimal, where n is the number of queries and $ \epsilon $ is a fixed constant with $0<\epsilon \leq 1$. We also present an exponential algorithm which delivers a plan with the optimal evaluation cost. In the case of the index-based star join, we present a heuristic algorithm which delivers a plan whose evaluation cost is n times the optimal, and an exponential algorithm which delivers a plan with the optimal evaluation cost. We then consider a general case in which both hash-based star-join and index-based star-join queries are included. For this case, we give a possible improvement on the work of Zhao et al., based on an analysis of their solutions. We also develop another heuristic and an exact algorithm for the problem. We finally conduct a performance study by implementing our algorithms. The experimental results demonstrate that the solutions delivered for the restricted cases are always within two times of the optimal, which confirms our theoretical upper bounds. Actually these experiments produce much better results than our theoretical estimates. To the best of our knowledge, this is the only development of polynomial algorithms for the first two cases which are able to deliver plans with deterministic performance guarantees in terms of the qualities of the plans generated. The previous approaches including that of [ZDNS98] may generate a feasible plan for the problem in these two cases, but they do not provide any performance guarantee, i.e., the plans generated by their algorithms can be arbitrarily far from the optimal one."
"Communication behavior represents dynamic evolution and cooperation of a group of objects in accomplishing a task. It is an important feature in object-oriented systems. We propose the concept of activity as a basic building block for declarative specification of communication behavior in object-oriented database systems, including the temporal ordering of message exchanges within object communication and the behavioral relationships between activity executions. We formally introduce two kinds of activity composition mechanisms: activity specialization and activity aggregation for abstract implementation of communication behavior. The former is suited for behavioral refinement of existing activities into specialized activities. The latter is used for  behavioral composition of simpler activities into complex activities, and ultimately, into the envisaged database system. We use first-order temporal logic as an underlying formalism for specification of communication constraints. The well known Air-traffic-control case is used as a running example to highlight the underlying concepts, to illustrate the usefulness, and to assess the effectiveness of the activity model for declarative specification of communication behavior in the relevant universe of discourse. We also propose a methodological framework for integrating activity schema with entity schema in an object-oriented design environment."
"1. Critical quality of clot structure: Alisa S. Wolberg, Ph.D., F.A.h.A., Associate Professor Pathology and laboratory Medicine, University of north Carolina at Chapel hill 2. Anticoagulation management for surgery and regional anesthesia: Marc Samama, M.D., Ph.D., F.C.C.P., Professor and Chair, Department of Anaesthesia and intensive Care Medicine, Cochin and h?tel-Dieu University hospitals, Paris, France 3. Managing new anticoagulants: Purified and recombinant strategies for prevention and treatment of bleeding: Jerrold h. levy, M.D., F.A.h.A., F.C.C.M., Professor of Anesthesiology, Associate Professor of Surgery, Duke University School of Medicine"
"Extraction of information from unstructured or semistructured Web documents often requires a recognition and delimitation of records. (By ¡°record¡± we mean a group of information relevant to some entity.) Without first chunking documents that contain multiple records according to record boundaries, extraction of record information will not likely succeed. In this paper we describe a heuristic approach to discovering record boundaries in Web documents. In our approach, we capture the structure of a document as a tree of nested HTML tags, locate the subtree containing the records of interest, identify candidate separator tags within the subtree using five independent heuristics, and select a consensus separator tag based on a combined heuristic. Our approach is fast (runs linearly for practical cases within the context of the larger data-extraction problem) and accurate (100% in the experiments we conducted)."
"From the Publisher:  The focus of Data Management for Mobile Computing is on the impact of mobile computing on data management beyond the networking level. The purpose is to provide a thorough and cohesive overview of recent advances in wireless and mobile data management. The book is written with a critical attitude. This volume probes the new issues introduced by wireless and mobile access to data and what are both their conceptual and practical consequences. Data Management for Mobile Computing provides a single source for researchers and practitioners who want to keep current on the latest innovations in the field. It can also serve as a textbook for an advanced course on mobile computing or as a companion text for a variety of courses including courses on distributed systems, database management, transaction management, operating or file systems, information retrieval or dissemination, and web computing."
"Personalization, advertising, and the sheer volume of online data generate a staggering amount of dynamic web content. In addition to web caching, View Materialization has been shown to accelerate the generation of dynamic web content. View materialization is an attractive solution as it decouples the serving of access requests from the handling of updates. In the context of the Web, selecting which views to materialize must be decided online and needs to consider both performance and data freshness, which we refer to as the Online View Selection problem. In this paper, we define data freshness metrics, provide an adaptive algorithm for the online view selection problem, and present experimental results."
"The availability of summary data for XML documents has many applications, from providing users with quick feedback about their queries, to cost-based storage design and query optimization. StatiX is a novel XML Schema-aware statistics framework that exploits the structure derived by regular expressions (which define elements in an XML Schema) to pinpoint places in the schema that are likely sources of structural skew. As we discuss below, this information can be used to build concise, yet accurate, statistical summaries for XML data. StatiX leverages standard XML technology for gathering statistics, notably XML Schema validators, and it uses histograms to summarize both the structure and values in an XML document. In this paper we describe the StatiX system. We develop algorithms that decompose schemas to obtain statistics at different granularities and discuss how statistics can be gathered as documents are validated. We also present an experimental evaluation which demonstrates the accuracy and scalability of our approach and show an application of these statistics to cost-based XML storage design."
"Many database applications need accountability and trace-ability that necessitate retaining previous database states. For a transaction-time database supporting this, the choice of times used to timestamp database records, to establish when records are or were current, needs to be consistent with a committed transaction serialization order. Previous solutions have chosen timestamps at commit time, selecting a time that agrees with commit order. However, SQL standard databases can require an earlier choice because a statement within a transaction may request ¡°current time.¡± Managing timestamps chosen before a serialization order is established is the challenging problem we solve here. By building on two-phase locking concurrency control, we can delay a transaction¡¯s choice of a timestamp, reducing the chance that transactions may need to be aborted in order keep timestamps consistent with a serialization order. Also, while timestamps stored with records in a transaction-time database make it possible to directly identify write-write and write-read conflicts, handling read-write conflicts requires more. Our simple auxiliary structure conservatively detects read-write conflicts, and hence provides transaction timestamps that are consistent with a serialization order."
"Market research companies predict a huge market for services to be delivered to mobile users. Services include route guidance, point-of-interest search, metering services such as road pricing and parking payment, traffic monitoring, etc. We believe that no single such service will be the killer service, but that suites of integrated services are called for. Such integrated services reuse integrated content obtained from multiple content providers."
"Spatial data types or algebras for database systems should (1) be fully general, that is, closed under set operations, (2) have formally defined semantics, (3) be defined in terms of finite representations available in computers, (4) offer facilities to enforce geometric consistency of related spatial objects, and (5) be independent of a particular DBMS data model, but cooperate with any. We present an algebra that usesrealms as geometric domains underlying spatial data types. A realm, as a general database concept, is a finite, dynamic, user-defined structure underlying one or more system data types. Problems of numerical robustness and topological correctness are solved within and below the realm layer so that spatial algebras defined above a realm have very nice algebraic properties. Realms also interact with a DMBS to enforce geometric consistency on object creation or update. The ROSE algebra is defined on top of realms and offers general types to represent point, line, and region features, together with a comprehensive set of operations. It is described within a polymorphic type system and interacts with a DMBS data model and query language through an abstractobject model interface. An example integration of ROSE into the object-oriented data model O2 and its query language is presented."
"Many proposed protocols for replicated databases consider centralized control of each transaction so that given a transaction, some site will monitor the remote data access and transaction commit. We consider the ap preach of broadcasting transactions to remote sites and handling these transactions in their complete form at each site. We consider data of two types: shared-private data and public data and show that transactions working only on shared-private data can be executed under a local concurrency control protocol. We assume a synchronized network with possibilities of partition failures. We show that in our scheme transaction execution can be managed with less communication delay compared to centralized transaction control."
"Significant advances have been achieved in system, syntactic and structural/schematic interoperability in a distributed network. Yet, meaningful exchange of information among autonomously designed and populated, dynamic, structured and semi-structured Heterogeneous Information Sources (HIS) remains a major challenge. A pure Peer-to-Peer architecture lends itself naturally to this problem as the information sources are totally autonomous and, practically, a-priori integration cannot be assumed. While ontologies may play a role in facilitating integration, they are not the panacea [3] advocated by many researchers. Rather, integration ought to be viewed as an emergent phenomenon constructed incrementally, and its state is dependent on the frequency and the quality of interactions between the peers and their subsequent negotiations and agreements to reach common interpretations within the context of a given task."
"CORAL is a modular declarative query language/programming language that supports general Horn clauses with complex terms, set-grouping, aggregation, negation, and relations with tuples that contain (universally quantified) variables. Support for persistent relations is provided by using the EXODUS storage manager. A unique feature of CORAL is that it provides a wide range of evaluation strategies and allows users to optionally tailor execution of a program through high-level annotations. A CORAL program is organized as a collection of modules, and this structure is used as the basis for expressing control choices. CORAL has an interface to C++, and uses the class structure of C++ to provide extensibility. FinaUy, CORAL supports a command sublanguage, in which statements are evaluated in a user-specified order. The statements can be queries, updates, production-system style rules, or any command that can be typed in at the CORAL"
"As computational power and storage capacity increase, processing and analyzing large volumes of data play an increasingly important part in many domains of scientific research. Typical examples of large scientific datasets include long running simulations of time-dependent phenomena that periodically generate snapshots of their state (e.g. hydrodynamics and chemical transport simulation for estimating pollution impact on water bodies [4, 6, 20], magnetohydrodynamics simulation of planetary magnetospheres [32], simulation of a flame sweeping through a volume [28], airplane wake simulations [21]), archives of raw and processed remote sensing data (e.g. AVHRR [25], Thematic Mapper [17], MODIS [22]), and archives of medical images (e.g. confocal light microscopy, CT imaging, MRI, sonography)."
"We consider the problem of mapping data in peer-to-peer data-sharing systems. Such systems often rely on the use of mapping tables listing pairs of corresponding values to search for data residing in different peers. In this paper, we address semantic and algorithmic issues related to the use of mapping tables. We begin by arguing why mapping tables are appropriate for data mapping in a peer-to-peer environment. We discuss alternative semantics for these tables and we present a language that allows the user to specify mapping tables under different semantics. Then, we show that by treating mapping tables as constraints (called mapping constraints) on the exchange of information between peers it is possible to reason about them. We motivate why reasoning capabilities are needed to manage mapping tables and show the importance of inferring new mapping tables from existing ones. We study the complexity of this problem and we propose an efficient algorithm for its solution. Finally, we present an implementation along with experimental results that show that mapping tables may be managed efficiently in practice."
"In stark contrast to the 25% per year increase in areal density delivered by the magnetic disk industry during the 1970s and 1980s, yearly increases today are 60%, on par with DRAM density increases. Moreover, the storage industry is also delivering substantially higher data rates, smart disk-embedded readahead and writebehind, and a new generation of high-speed serial interconnects. This industry has also embraced Redundant Arrays of Inexpensive (or Independent) Disks (RAID) technology - 1997's RAID market is expected to be 13 billion dollars. With this rapidly evolving market and technology base, parallel storage systems must evolve beyond RAID levels 1 through 5. This talk is intended for researchers and practitioners interested in current trends in storage systems. It will highlight storage technology trends, RAID technology trends, and trends toward RAID-style support for network-based parallel storage systems."
"Large database systems (e.g., federations, warehouses) are multi-layer ¡ª i.e., a combination of base databases and (virtual or physical) view databases1. Smaller systems use views for layers that hide detailed physical and conceptual structures. We argue that most databases would be more effective if they were more user-centered ¡ª i.e., if they allowed users, administrators, and application developers to work mostly within their native view. To do so, we need first class views ¡ª views that support most of the metadata and operations available on source tables."
"In order to support dynamic setup of business processes among independent organizations, a formal standard schema for describing the business processes is basically required. The ebXML framework provides such a specification schema called BPSS (Business Process Specification Schema) which is available in two stand-alone representations: a UML version, and an XML version. The former, however, is not intended for the direct creation of business process specifications, but for defining specification elements and their relationships required for creating an ebXML-compliant business process specification. For this reason, it is very important to support conceptual modeling that is well organized and directly matched with major modeling concepts. This paper deals with how to represent and manage B2B business processes using UML-compliant diagrams. The major challenge is to organize UML diagrams in a natural way that is well suited with the business process meta-model and then to transform the diagrams into an XML version. This paper demonstrates the usefulness of conceptually modeling business processes by prototyping a business process editor tool called ebDesigner."
"Real-time computing brings two new requirements to database management. The first is the deadline constraint which requires better scheduling algorithms to meet transaction deadfines. The second requirement is the temporal validity, or external consistency[Lin89], requirement of data: a real-time database must prevent data from being corrupted not only by the executions of concurrent transactions but also by the delay from sharing computing resources and real-time scheduler decisions. In this paper, we study the external consistency requirement in real-time databases. We propose a semantic-based concurrency control scheme that prefers the external consistency to the traditional serializability. Two new concepts are introduced in our work. An update of a physical object value is considered to be compatible to those read operations that need to access the most recent data. Secondly, if a transaction depends strongly on the validity of the value of an object, a new update may cause the transaction to be aborted since continuing the transaction may be harmful to the appfication. A real-Life example is the stock market database. A trading program may be executed for a long time and its read operations should not block any new updates. Moreover, if there is a big sudden change in a particular stock price, it may be better to abort an on-going transaction rather than letting it make some invalid decisions."
"This paper describes the design and implementation of NAOS, an active rule component in the object-oriented database system 02. The contribution of this work is related to two main aspects. The first concerns the integration of the rule concept within the 02 model, providing a way to structure applications. Rules are part of a schema and do not belong to a class. Program execution and data manipulation, including method calls, can be driven on rules. The second aspect concerns the way NAOS interacts with the kernel of the 02 system. To support a reactive capability the object manager semantics has been extended, thus providing an efficient event detection. Applications produce events and the subscribed event types react to these events. As a result, rules are triggered."
"Following the tradition of these acceptance talks, I will be giving my thoughts on where our field is going. Any discussion of the future of information retrieval (IR) research, however, needs to be placed in the context of its history and relationship to other fields. Although IR has had a very strong relationship with library and information science, its relationship to computer science (CS) and its relative standing as a sub-discipline of CS has been more dynamic. IR is quite an old field, and when a number of CS departments were forming in the 60s, it was not uncommon for a faculty member to be pursuing research related to IR."
"Due to the large size and complexity of the sometimes country-wide 3D geospatial data, the GIS software vendors and service providers face many challenges when building 3D spatial data infrastructures for realizing the efficient storage, analysis, management, interaction, and visualization of the 3D city models based on the CityGML standard. Hence, there has been strong demand for an open and comprehensive software solution that can provide full support of the aforementioned functionalities. The ¡®3D City Database¡¯ (3DCityDB) is a free 3D geo-database solution for CityGML-based 3D city models. 3DCityDB has been developed as an Open Source and platform-independent software suite to facilitate the development and deployment of 3D city model applications. The 3DCityDB software package consists of a database schema for spatially enhanced relational database management systems."
"Sybase is a leading RDBMS vendor that started by providing OLTP systems for the client-server environment and is currently maturing into an enterprise-wide data management solution provider. As a critical part of this enterprise-wide data management strategy, Sybase Replication Server supports data replication in a distributed environment. In such an enviromnent, the same data may be replicated at multiple sites for quick data access and for high data availability. Replicated data can be maintained using strong consistency or weak consistence algorithms. Algorithms for maintaining strong consistency, such as primary copy and quorum consensus, severely limit data availability during network partition."
"New telecommunication services and mobility networks have introduced databases in telecommunication networks. Compared with traditional use of databases, telecom databases must fulfill very tough requirements on response time, throughput, and availability. ClustRa is a telecom database prototype developed to run on standard workstations interconnected by an ATM switch. To meet the throughput and real-time response requirements, ClustRa is a main memory database with neighbor main, memory logging. Transactions are executed in parallel. To meet the availability requirements, we use a 2-safe replication scheme over two sites with independent failure modes, a novel declustering strategy, early detection of failures with fast takeover, and by on-line self-repair and maintenance. This paper gives an overview of ClustRa and includes a set of performance measurements."
There has been a lot of talk about how the Internet is going to change the world economy. Companies will come together in a ¡°plug and play¡± fashion to form trading partner networks. Virtual companies will be established and new business models can be created based on access to information and agents that can carry it around the world using computer networks.
"In the last few years, numerous proposals for modelling and querying Multidimensional Databases (MDDB) are proposed. A rigorous classification of the different types of hierarchies is still an open problem. In this paper we propose and discuss some different types of hierarchies within a single dimension of a cube. These hierarchies divide in different levels of aggregation a single dimension. Depending on them, we discuss the characterization of some OLAP operators that refer to hierarchies in order to maintain the data cube consistency. Moreover, we propose a set of operators for changing the hierarchy structure. The issues discussed provide modelling flexibility during the scheme design phase and correct data analysis."
"The automatic reclamation of storage for unreferenced objects is very important in object databases. Existing language system algorithms for automatic storage reclamation have been shown to be inappropriate. In this paper, we investigate methods to improve the performance of algorithms for automatic for automatic storage reclamation of object databases. These algorithms are based on a technique called partitioned garbage collection, in which a subset of the entire database is collected independently of the rest. Specifically, we investigate the policy that is used to select what partition in the database should be collected. The policies that we propose and investigate are based on the intuition that the values of overwritten pointers provide good hints about  where to find garbage. Using trace-driven simulation, we show that one of our policies requires less I/O to collect more garbage than any existing implementable policy and performs close to a near-optimal policy over a wide range of database sizes and object connectivities."
"Huge masses of digital data about products, customers and competitors have become available for companies in the services sector. In order to exploit its inherent (and often hidden) knowledge for improving business processes the application of data mining technology is the only way for reaching good and ef- cient results, as opposed to purely manual and interactive data exploration. This paper reports the rst steps of a pro ject initiated at Swiss Life for mining its data resources from the life insurance business. Based on the Data Warehouse MASY collecting all relevant data from the OLTP systems for the processing of private life insurance contracts, a Data Mining environment is set up which integrates a palette of tools for automatic data analysis, in particular machine learning approaches."
"In this paper, we investigate how to scale hierarchical clustering methods (such as OPTICS) to extremely large databases by utilizing data compression methods (such as BIRCH or random sampling). We propose a three step procedure: 1) compress the data into suitable representative objects; 2) apply the hierarchical clustering algorithm only to these objects; 3) recover the clustering structure for the whole data set, based on the result for the compressed data. The key issue in this approach is to design compressed data items such that not only a hierarchical clustering algorithm can be applied, but also that they contain enough information to infer the clustering structure of the original data set in the third step. This is crucial because the results of hierarchical clustering algorithms, when applied naively to a random sample or to the clustering features (CFs) generated by BIRCH, deteriorate rapidly for higher compression rates. This is due to three key problems, which we identify. To solve these problems, we propose an efficient post-processing step and the concept of a Data Bubble as a special kind of compressed data item. Applying OPTICS to these Data Bubbles allows us to recover a very accurate approximation of the clustering structure of a large data set even for very high compression rates. A comprehensive performance and quality evaluation shows that we only trade very little quality of the clustering result for a great increase in performance."
"The University of Ulm was founded in 1967 with focus on medicine and natural sciences. In 1989 the University established two new faculties: Engineering Sciences and Computer Science. This enlargement took place within the framework of the so-called Science City Ulm. In a joint effort, the State of Baden-W¨¹rttemberg, industrial companies, the University, and the City of Ulm successfully established a research and development infrastructure at or nearby the university campus consisting of the university's research labs, university-related research institutes like the Research Institute for Applied Knowledge Processing (FAW), and industrial research and development labs, especially a large research center of Daimler-Benz AG."
"We present the design and implementation of the XSQ system for querying streaming XML data using XPath 1.0. Using a clean design based on a hierarchical arrangement of pushdown transducers augmented with buffers, XSQ supports features such as multiple predicates, closures, and aggregation. XSQ not only provides high throughput, but is also memory efficient: It buffers only data that must be buffered by any streaming XPath processor. We also present an empirical study of the performance characteristics of XPath features, as embodied by XSQ and several other systems."
"Statements and opinions expressed in this supplement are those of the authors and not necessarily those of the American Osteopathic Association, JAOA, the editors or the Editorial Advisory Board, or the institutions with which the authors are affiliated, unless expressly stated . This supplement to the JAOA is designated by the Division of Continuing Medical Education of the American Osteopathic Association to carry 2 hours of category 1-B credit for osteopathic physicians who read it and return the completed post-test. All editorial content is developed independently by the American Osteopathic Association in accordance with the Food and Drug Administration¡¯s Guidelines for Continuing Medical Education Programs. "
"First-order formulas allow natural descriptions of queries and rules. Van Gelder's alternating fixpoint semantics extends the well-founded semantics of normal logic programs to general logic programs with arbitrary first-order formulas in rule bodies. However, an implementation of general logic programs through the standard translation into normal logic programs does not preserve the alternating fixpoint semantics. This paper presents a direct method for goal-oriented query evaluation of general logic programs. Every general logic program is first transformed into a normal form where the body of each rule is either an existential conjunction of literals or a universal disjunction of literals. Techniques of memoing and loop checking are incorporated so that termination and polynomial-time data complexity are guaranteed for deductive databases (or function-free programs). Results of the soundness and search space completeness are established."
"Query processing and optimization in mediator systems that access distributed non-proprietary sources pose many novel problems. Cost-based query optimization is hard because the mediator does not have access to source statistics information and furthermore it may not be easy to model the source's performance. At the same time, querying remote sources may be very expensive because of high connection overhead, long computation time, financial charges, and temporary unavailability. We propose a cost-based optimization technique that caches statistics of actual calls to the sources and consequently estimates the cost of the possible execution plans based on the statistics cache. We investigate issues pertaining to the design of the statistics cache and experimentally analyze various tradeoffs. We also present a query result caching mechanism that allows us to effectively use results of prior queries when the source is not readily available. We employ the novel invariants mechanism, which shows how semantic information about data sources may be used to discover cached query results of interest."
"Int#ra-operator (or partitioned) parallelism is a well-established mechanism for achieving high performance in parallel database systems. However, the problem of how to exploit intra-operator parallelism in a multi-query environment is not well underst,ood. This paper presents a detailed performance evaluation of several algorithms for managing intra-operator parallelism in a parallel database system. A dynamic scheme based on the concept of matching the ra.te of flow of tuples between operat,ors is shown to perform well on a variety of workloads and configurations."
"In recent years there has been an increasing interest in databases of moving objects where the motion and extent of objects are represented as a function of time. The focus of this paper is on the maintenance of continuous K- nearest neighbor (k-NN) queries on moving points when updates are allowed. Updates change the functions describing the motion of the points, causing pending events to change. Events are processed to keep the query result consistent as points move. It is shown that the cost of maintaining a continuous k-NN query result for moving points represented in this way can be significantly reduced with a modest increase in the number of events processed in the presence of updates. This is achieved by introducing a continuous within query to filter the number of objects that must be taken into account when maintaining a continuous k-NN query. This new approach is presented and compared with other recent work. Experimental results are presented showing the utility of this approach."
"This paper describes the methodology and implementation of a data management system for highly distributed systems, which was built to solve the scalability and reliability problems faced in a wide area postal logistics application developed at Siemens. The core of the approach is to borrow from Internet routing protocols, and their proven scalability and robustness, to build a network-embedded dynamic database index, and to augment schema definition to optimize the use of this index. The system was developed with an eye toward future applications in the area of sensor networks."
"This report describes opportunities for the DB/IS community to contribute to the advancement of the Semantic Web and the challenges or new research topics presented by the vision of the Semantic Web to the database and information systems (DB/IS) researchers. It is based on the NSF-OntoWeb Invitational Workshop on DB/IS Research for Semantic Web and Enterprises that was held during April 3-5, 2002 at the Amicalola Falls State Park in the northern Georgia mountains. Most of the workshop participants were"
"However, MapBase also turned out to share many characteristics of classical information systems: it provides a central repository of carefully administered, mission-critical data used by clients written in many languages and running on a variety of hardware. In addition, our laboratory emphasizes continuous process re-engineering, with the result that MapBase¡¯s schema must evolve rapidly in order to reflect the current experimental workflow."
"Encrypted databases, a popular approach to protecting data from compromised database management systems (DBMS's), use abstract threat models that capture neither realistic databases, nor realistic attack scenarios. In particular, the ""snapshot attacker"" model used to support the security claims for many encrypted databases does not reflect the information about past queries available in any snapshot attack on an actual DBMS."
"Time sequences appear in various application domains. Many applications require time sequences to be seen as continuous where implicit values can be derived from explicit values by arbitrary user-defined interpolation functions. This paper describes the implementation of an extended SELECT operator, ¦Ò*, that retrieves implicit values from a discrete time sequence under various user-defined interpolation assumptions. The ¦Ò* operator is efficiently supported by an indexing technique termed the IP-index. Possible optimizations of the ¦Ò* operator are investigated and verified by experiments on SHORE. The ¦Ò* operator is applicable to any 1-D sequence data."
"We demonstrate the XISS/R system, an implementation of the XML Indexing and Storage System (XISS) on top of a relational database. The system is based on the XISS extended preorder numbering scheme, which captures the nesting structure of XML data and provides the opportunity for storage and query processing independent of the particular structure of the data. The system includes a web-based user interface, which enables stored documents to be queried via XPath. The user interface utilizes the XPath Query Engine, which automatically translates XPath queries into efficient SQL statements."
"We have been designing and implementing an object-relational multimedia database. A new data model was first developed, which represents various types of media entities, and temporal/logical relationships among these entities. Thereafter, a three-layer object-relational database infrastructure was proposed in our project, in order to support the proposed data model. In this paper, we concentrate on the search and query mechanisms designated for our database infrastructure. In particular, we discuss a new query language, which is developed as a multimedia extension of SQL3."
"This work is a proposal for a database index structure that has been specifically designed to support the evaluation of XPath queries. As such, the index is capable to support all XPath axes (including ancestor, following, preceding-sibling, descendant-or-self, etc.). This feature lets the index stand out among related work on XML indexing structures which had a focus on regular path expressions (which correspond to the XPath axes children and descendant-or-self plus name tests). Its ability to start traversals from arbitrary context nodes in an XML document additionally enables the index to support the evaluation of path traversals embedded in XQuery expressions. Despite its flexibility, the new index can be implemented and queried using purely relational techniques, but it performs especially well if the underlying database host provides support for R-trees. A performance assessment which shows quite promising results completes this proposal."
"We formulate the content-based image indexing problem as a multi-dimensional nearest-neighbor search problem, and develop/implement an optimistic vantage-point tree algorithm that can dynamically adapt the indexed search process to the characteristics of given queries. Based on our performance study, the system typically only needs to touch less than 20 % of the index entries for well -behaved queries, i.e., when the query images are relatively close to their nearest neighbors in the database. We also report in this paper the results of extensive performance experiments, which characterise the impacts of various configuration and workload parameters on the performance of the proposed algorithm."
"The read-mostly environment of data warehousing makes it possible to use more complex indexes to speed up queries than in situations where concurrent updates are present. The current paper presents a short review of current indexing technology, including row-set representation by Bitmaps, and then introduces two approaches we call Bit-Sliced indexing and Projection indexing. A Projection index materializes all values of a column in RID order, and a Bit-Sliced index essentially takes an orthogonal bit-by-bit view of the same data. While some of these concepts started with the MODEL 204 product, and both Bit-Sliced and Projection indexing are now fully realized in Sybase IQ, this is the first rigorous examination of such indexing capabilities in the literature. We compare algorithms that become feasible with these variant index types against algorithms using more conventional indexes. The analysis demonstrates important performance advantages for variant indexes in some types of SQL aggregation, predicate evaluation, and grouping. The paper concludes by introducing a new method whereby multi-dimensional group-by queries, reminiscent of OLAP/Datacube queries but with more flexibility, can be very efficiently performed."
"Decision support applications involve complex queries on very large databases. Since response times should be small, query optimization is critical. Users typically view the data as multidimensiona..."
"The increasing usage of location-aware devices, such as GPS and RFID, has made moving object management an important task. Especially, being demanded in real-world applications, continuous query processing on moving objects has attracted significant research efforts. However, little attention has been given to the design of concurrent continuous query processing for multi-user environments. In this paper, we propose a concurrency control protocol to efficiently process continuous queries over moving objects on a B-tree-based framework. The proposed protocol integrates link-based and lock-coupling strategies, and is proven to assure serializable isolation, data consistency, and deadlock-free for continuous query processing. Concurrent operations including continuous query, object movement, and query movement are protected under this protocol. Experimental results on benchmark data sets demonstrated the scalability and efficiency of the proposed concurrent framework."
"Dynamically generated web pages are ubiquitous today but their high demand for resources creates a huge scalability problem at the servers. Traditional web caching is not able to solve this problem since it cannot provide any guarantees as to the freshness of the cached data. A robust solution to the problem is web materialization, where pages are cached at the web server and constantly updated in the background, resulting in fresh data accesses on cache hits. In this work, we define Quality of Data metrics to evaluate how fresh the data served to the users is. We then focus on the update scheduling problem: given a set of views that are materialized, find the best order to refresh them, in the presence of continuous updates, so that the overall Quality of Data (QoD) is maximized. We present a QoD-aware Update Scheduling algorithm that is adaptive and tolerant to surges in the incoming update stream. We performed extensive experiments using real traces and synthetic ones, which show that our algorithm consistently outperforms FIFO scheduling by up to two orders of magnitude."
"Regular expressions with capture variables, also known as ""regex formulas,'' extract relations of spans (interval positions) from text. These relations can be further manipulated via the relational Algebra as studied in the context of ""document spanners,"" Fagin et al.'s formal framework for information extraction. We investigate the complexity of querying text by Conjunctive Queries (CQs) and Unions of CQs (UCQs) on top of regex formulas. Such queries have been investigated in prior work on document spanners, but little is known about the (combined) complexity of their evaluation. We show that the lower bounds (NP-completeness and W[1]-hardness) from the relational world also hold in our setting; in particular, hardness hits already single-character text. Yet, the upper bounds from the relational world do not carry over. Unlike the relational world, acyclic CQs, and even gamma-acyclic CQs, are hard to compute. The source of hardness is that it may be intractable to instantiate the relation defined by a regex formula, simply because it has an exponential number of tuples. Yet, we are able to establish general upper bounds. In particular, UCQs can be evaluated with polynomial delay, provided that every CQ has a bounded number of atoms (while unions and projection can be arbitrary). Furthermore, UCQ evaluation is solvable with FPT (Fixed-Parameter Tractable) delay when the parameter is the size of the UCQ."
"We present a comprehensive performance evaluation of transitive closure (reachability) algorithms for databases. The study is based upon careful implementations of the algorithms, measures page I/O, and covers algorithms for full transitive closure as well as partial transitive closure (finding all successors of each node in a set of given source nodes). We examine a wide range of acyclic graphs with varying density and ¡°locality¡± of arcs in the graph. We also consider query parameters such as the selectivity of the query, and system parameters such as the buffer size and the page and successor list replacement policies. We show that significant cost tradeoffs exist between the algorithms in this spectrum and identify the factors that influence the performance of the algorithms."
"Relational Database Management Systems (RDBMS) have been very successful at managing structured data with well-defined schemas. Despite this, relational systems are generally not the first choice for management of data where schemas are not pre-defined or must be flexible in the face of variations and changes. Instead, No-SQL database systems supporting JSON are often selected to provide persistence to such applications. JSON is a light-weight and flexible semi-structured data format supporting constructs common in most programming languages. In this paper, we analyze the way in which requirements differ between management of relational data and management of JSON data. We present three architectural principles that facilitate a schema-less development style within an RDBMS so that RDBMS users can store, query, and index JSON data without requiring schemas. We show how these three principles can be applied to industry-leading RDBMS platforms, such as the Oracle RDBMS Server, with relatively little effort. Consequently, an RDBMS can unify the management of both relational data and JSON data in one platform and use SQL with an embedded JSON path language as a single declarative language to query both relational data and JSON data. This SQL/JSON approach offers significant benefits to application developers as they can use one product to manage both relational data and semi-structured flexible schema data."
"XML is rapidly emerging as a standard for exchanging business data on the World Wide Web. For the foreseeable future, however, most business data will continue to be stored in relational database systems. Consequently, if XML is to fulfill its potential, some mechanism is needed to publish relational data as XML documents. Towards that goal, one of the major challenges is finding a way to efficiently structure and tag data from one or more tables as a hierarchical XML document. Different alternatives are possible depending on when this processing takes place and how much of it is done inside the relational engine. In this paper, we characterize and study the performance of these alternatives. Among other things, we explore the use of new scalar and aggregate functions in SQL for constructing complex XML documents directly in the relational engine. We also explore different execution plans for generating the content of an XML document. The results of an experimental study show that constructing XML documents inside the relational engine can have a significant performance benefit. Our results also show the superiority of having the relational engine use what we call an ¡°outer union plan¡± to generate the content of an XML document."
"Nowadays parallel object-relational DBMS are envisioned as the next great wave, but there is still a lack of efficient implementation concepts for some parts of the proposed functionality. Thus one of the current goals for parallel object-relational DBMS is to move towards higher performance. In this paper we develop a framework that allows to process user-defined functions with data parallelism. We will describe the class of partitionable functions that can be processed parallelly. We will also propose an extension which allows to speed up the processing of another large class of functions by means of parallel sorting. Functions that can be processed by means of our techniques are often used in decision support queries on large data volumes, for example. Hence a parallel execution is indispensable."
"There has been much work on compressing database indexes, but less on compressing the data itself. We examine the performance gains to be made by compression outside the index. A novel compression algorithm is reported, which enables the processing of queries without decompressing data needed to perform join operations in a database built on a triple store. The results of modelling the performance of the database with and without compression are given and compared with other recent work in this area. It is found that for some applications, gains in performance of over 50% are achievable, and in OLTP-like situations, there are also gains to be made."
Is replication salvation or the devil in disguise? Here's what three implementations tell us
"Multiversion access methods have been emerged in the literature primarily to support queries on a transaction-time database where records are never physically deleted. For a popular class of efficient methods (including the multiversion Btree), data records and index entries are occasionally duplicated to separate data according to time. In this paper, we present techniques for improving query processing in multiversion access methods. In particular, we address the problem of avoiding duplicates in the response sets. We first discuss traditional approaches that eliminate duplicates using hashing and sorting. Next, we propose two new algorithms for avoiding duplicates without using additional data structures. The one performs queries in a depth-first order starting from a root, whereas the other exploits links between data pages. These methods are discussed in full details and their main properties are identitied. Preliminary performance results confirm the advantages of these methods in comparison to traditional ones according to CPU-time, disk accesses and storage."
"Garbage collection is important in object-oriented databases to free the programmer from explicitly deallocating memory. In this paper, we present a garbage collection algorithm, called Transactional Cyclic Reference Counting (TCRC), for object-oriented databases. The algorithm is based on a variant of a reference-counting algorithm proposed for functional programming languages The algorithm keeps track of auxiliary reference count information to detect and collect cyclic garbage. The algorithm works correctly in the presence of concurrently running transactions, and system failures. It does not obtain any long-term locks, thereby minimizing interference with transaction processing. It uses recovery subsystem logs to detect pointer updates; thus, existing code need not be rewritten. Finally, it exploits schema information, if available, to reduce costs. We have implemented the TCRC algorithm and present results of a performance study of the implementation."
"An information retrieval (IR) engine can rank documents based on textual proximity of keywords within each document. In this paper we apply this notion to search across an entire database for objects that are ""near"" other relevant objects. Proximity search enables simple ""focusing"" queries based on general relationships among objects, helpful for interactive query sessions. We view the database as a graph, with data in vertices (objects) and relationships indicated by edges. Proximity is defined based on shortest paths between objects. We have implemented a prototype search engine that uses this model to enable keyword searches over databases, and we have found it very effective for quickly finding relevant information. Computing the distance between objects in a graph stored on disk can be very expensive. Hence, we show how to build compact indexes that allow us to quickly find the distance between objects at search time. Experiments show that our algorithms are effcient and scale well."
"Data abstractions were originally conceived as a specification tool in programming. They also appear to be useful for exploring and explaining the capabilities and shortcomings of the data definition and manipulation facilities of present-day database systems. Moreover they may lead to new approaches to the design of these facilities. In the first section the paper introduces an axiomatic method for specifying data abstractions and, on that basis, gives precise meaning to familiar notions such as data model, data type, and database schema. In a second step the various possibilities for specifying data types within a given data model are examined and illustrated. It is shown that data types prescribe the individual operations that are allowed within a database. Finally, some additions to the method are discussed which permit the formulation of interrelationships between arbitrary operations."
"With the increasing availability and scale of graph data from Web 2.0, graph partitioning becomes one of efficient preprocessing techniques to balance the computing workload. Since the cost of partitioning the entire graph is strictly prohibitive, there are some recent tentative works towards streaming graph partitioning which can run faster, be easily paralleled, and be incrementally updated. Unfortunately, the experiments show that the running time of each partitioning is still unbalanced due to the variation of workload access pattens during the supersteps. In addition, the one-pass streaming partitioning result is not always satisfactory for the algorithms' local view of the graph."
"Workflow management has gained increasing attention recently as an important technology to improve information system development in dynamic and distributed organizations. To develop a workflow application, selected business processes of an organization are modelled, optimized and specified as workflow schemas, using workflow languages [2]. Workflow schemas are used by workflow management systems to control the execution of workflow instances, i.e., representations of real-world business processes [3]. The first generation of workflow management systems (WFMS) were developed mainly to model and control the execution of business processes with fairly static structures, to be executed in homogeneous environments. Recently, the need for enhanced flexibility of workflow modeling and execution and the integration of applications in heterogeneous environments emerged in the workflow context [I]. The WASA project aims at supporting flexible and distributed workflows in heterogeneous environments [4]. This paper briefly overviews the conceptual design and implementation of the object-oriented workflow management system WASAZ, and sketches the proposed demo. References to work that relates to ours or that we started from are given in the cited WASA papers."
"Object-Relational database systems allow users to define new user-defined types and functions. This presents new optimizer and run-time challenges to the database system on shared-nothing architectures. In this paper, we describe a new strategy we are exploring for the NCR Teradata Multimedia Database System; our focus is directing research for real applications we are seeing. In doing so, we will briefly describe optimizer challenges particularly related to predicate use of large multimedia objects, such as video/audio clips, images, and text documents. The motivation for this work is based on database tuning [SD961 for diverse queries related to multimedia objects. Most notably, expensive and/or high variant user defined functions [He198]. Our approach is referred to as plan-per-tuple. The"
"Multiversion support for XML documents is needed in many critical applications, such as software configuration control, cooperative authoring, web information warehouses, and ¡±e-permanence¡± of web documents. In this paper, we introduce efficient and robust techniques for: (i) storing and retrieving; (ii) viewing and exchanging; and (iii) querying multiversion XML documents. We first discuss the limitations of traditional version control methods, such as RCS and SCCS, and then propose novel techniques that overcome their limitations. Initially, we focus on the problem of managing secondary storage efficiently, and introduce an edit-based versioning scheme that enhances RCS with an effective clustering policy based on the concept of page-usefulness. The new scheme drastically improves version retrieval at the expense of a small (linear) space overhead. However, the edit-based approach falls short of achieving objectives (ii) and (iii). Therefore, we introduce and investigate a second scheme, which is reference-based and preserves the structure of the original document. In the reference-based approach, a multiversion document can be represented as yet another XML document, which can be easily exchanged and viewed on the web; furthermore, simple queries are also expressed and supported well under this representation. To achieve objective (i), we extend the page-usefulness clustering technique to the reference-based scheme. After characterizing the asymptotic behavior of the new techniques proposed, the paper presents the results of an experimental study evaluating and comparing their performance."
"Electronic commerce is emerging as a major Web-supported application. In this paper we argue that database technology can, and should, provide the back-bone for a wide range of such applications. More precisely, we present here the ActiveViews system, which, relaying on an extensive use of database features in-cluding views, active rules (triggers), and enhanced mechanisms for notification, access control and logging/tracing of users activities, provides the needed basis for electronic commerce. Based on the emerging XML standards (DOM, query languages for XML, etc.), the system offers a novel declarative view specification language, describing the relevant data and activities of all actors (e.g. vendors and clients) participat-ing in electronic commerce activities . Then, acting as an application generator, the system generates an actual, possibly customized, Web application that allows users to perform the given set of controlled activities and to work interactively on the specified data in a standard distributed environment. Although closely related to workflow management systems, a major difference here is the importance we give to data. While workflow systems give declarative means for specifying the operations flow, the data involved is typically described in a very abstract manner, often disconnected from the description of the flow itself."
"Galax is a light-weight, portable, open-source implementation of XQuery 1.0. Started in December 2000 as a small prototype designed to test the XQuery static type system, Galax has now become a solid implementation, aiming at full conformance with the family of XQuery 1.0 specifications. Because of its completeness and open architecture, Galax also turns out to be a very convenient platform for researchers interested in experimenting with XQuery optimization.  We demonstrate the Galax system as well as its most advanced features, including support for XPath 2.0, XML Schema and static type-checking. We also present some of our first experiments with optimization. Notably, we demonstrate query rewriting capabilities in the Galax compiler, and the ability to run queries on documents up to a Gigabyte without the need for preindexing. Although early versions of Galax have been shown in industrial conferences over the last two years, this is the first time it is demonstrated in the database community."
"In this work, we address the efficient evaluation of XQuery expressions over continuous XML data streams, which is essential for a broad range of applications including monitoring systems and information dissemination systems. While previous work has shown that automata theory is suited for on-the-fly pattern retrieval over XML data streams, we find that automata-based approaches suffer from being not as flexibly optimizable as algebraic query systems. In fact, they enforce a rigid data-driven paradigm of execution. We thus now propose a unified query model to augment automata-style processing with algebra-based query optimization techniques. The proposed model has been successfully applied in the Raindrop stream processing system. Our experimental study confirms considerable performance gains with both established optimization techniques and our novel query rewrite rules."
"We confront the promises of active database systems with the result of their use by application developers. The main problems encountered are iusufficient methodological support in analysis and design, the lack of standardization, missing development and administration tools for triggers, and weak performance. We concentrate on performance because we discovered it is one the maiu reasons that makes users reluctant to use active rules iu the development of large applications. We show, using simple concrete examples, that optimizing large applications is rendered difficult by the separation of transactions and triggers and the misunderstanding of their subtle interactions. We argue that tools, which provide assistance to programmers, database administrators, and database designers to optimize their applications and master application evolution is strongly needed."
"A number of researchers have become interested in the design of global-scale networked systems and applications. Our thesis here is that the database community's principles and technologies have an important role to play in the design of these systems. The point of departure is at the roots of database research: we generalize Codd's notion of data independence to physical environments beyond storage systems. We note analogies between the development of database indexes and the new generation of structured peer-to-peer networks. We illustrate the emergence of data independence in networks by surveying a number of recent network facilities and applications, seen through a database lens. We present a sampling of database query processing techniques that can contribute in this arena, and discuss methods for adoption of these technologies."
"The active object-oriented database system TriGS has been developed as part of a larger EC ESPRIT project aiming at the development of next-generation production scheduling and control systems [Huem93]. The goal of this paper is to summarize the work on TriGS which comprises both aspects concerning the development of the active system itself, and guidelines concerning the design of active databases."
"Classification of large datasets is an important data mining problem. Many classification algorithms have been proposed in the literature, but studies have shown that so far no algorithm uniformly outperforms all other algorithms in terms of quality. In this paper, we present a unifying framework called Rain Forest for classification tree construction that separates the scalability aspects of algorithms for constructing a tree from the central features that determine the quality of the tree. The generic algorithm is easy to instantiate with specific split selection methods from the literature (including C4.5, CART, CHAID, FACT, ID3 and extensions, SLIQ, SPRINT and QUEST).In addition to its generality, in that it yields scalable versions of a wide range of classification algorithms, our approach also offers performance improvements of over a factor of three over the SPRINT algorithm, the fastest scalable classification algorithm proposed previously. In contrast to SPRINT, however, our generic algorithm requires a certain minimum amount of main memory, proportional to the set of distinct values in a column of the input relation. Given current main memory costs, this requirement is readily met in most if not all workloads."
"The J2EE platform provides a variety of options for making business data persistent using DBMS technology. However, the integration with existing backend database systems has proven to be of crucial importance for the scalability and performance of J2EE applications, because modern e-business systems are extremely data-intensive. As a result, the data access layer, and the link between the application server and the database server in particular, are very susceptible to turning into a system bottleneck. In this paper we use the ECperf benchmark as an example of a realistic application in order to illustrate the problems mentioned above and discuss how they could be approached and eliminated. In particular, we show how asynchronous, message-based processing could be exploited to reduce the load on the DBMS and improve system performance, scalability and reliability. Furthermore, we discuss the major issues related to the correct use of entity beans (the components provided by J2EE for modelling persistent data) and present a number of methods to optimize their performance utilizing caching mechanisms. We have evaluated the proposed techniques through measurements and have documented the performance gains that they provide."
"Addressing mechanisms used by the new generation of Data Base Management Systems (DBMS) differ significantly from traditional ones. Such changes are the direct result of new applications requirements such as office information systems (OIS) and computer aided design (CAD). In this context, object format requires different representations on disk and in main memory, and this is often valid for interobject references. It is evident that these mechanisms are closely linked to the mode of object-identity implementation, as well as clustering strategies. All of these functions are controlled by the object manager.This article describes these mechanisms through the implementation of two object managers for object-oriented DBMS: O2 and ORION. We show how the performance of these systems depends on their memory management and addressing scheme. The two managers to be discussed merges techniques proposed by both data base field and object-oriented programming field. Their own mechanism differs, according to the way it handles distribution. ORION-1SX and O2 have a Client/Server architecture, but each one uses a different approach for distributing of functionalities. ORION-1SX implements an object-server, whereas O2 uses a page-server approach. An analysis of the two systems shows that they both use a two-level addressing mechanism. buffer management for objects in memory is diffent and more complex in ORION. On the other hand, the clustering strategies in O2 have the advantage of being more dynamic and can be specified outside the schema."
"Abstract. Support for semantic content is becoming more common in Web-accessible information systems. We see this support emerging with the use of ontologies and machine-readable, annotated documents. The practice of domain modeling coupled with the extraction of domain-specific, contextually relevant metadata also supports the use of semantics. These advancements enable knowledge discovery approaches that define complex relationships between data that is autonomously collected and managed. The InfoQuilt (One of the incarnations of the InfoQuilt system, as applied to the geographic information as part of the NSF Digital Library II initiative is the ADEPT-UGA system [Ade]. This research was funded in part by National Science Foundation grant IIS-9817432.) system supports one such knowledge discovery approach. This paper presents (parts of) the InfoQuilt system with the focus on its use for modeling and utilizing complex semantic inter-domain relationships to enable human-assisted knowledge discovery over Web-accessible heterogeneous data. This includes the specification and execution of Information Scale (IScapes), a semantically rich information request and correlation mechanism."
"Motivation  The field of data warehousing has emerged over the last decades. A data warehouse is developed at a moment in time to support business intelligence for an indefinite period of time. During the life of the data warehouse the world around it evolves, including the systems that are a source for the data warehouse. In order for a data warehouse to remain functioning and guarantee the quality of its data, it needs to be adjusted to the evolving world around it. The concept of Delta Impact Analysis is used by the company BI4U for the activities of analysing the impact of specific changes. This concept is important because it provides insight into how a data warehouse can be adjusted to the evolving world around it. The motivation to perform this research was the fact that a clear definition on the concept of DIA and what it comprehends was lacking.  Goals  The main goals of the research were to examine the topic of DIA in practice, to gather insights from literature and other research, to design and develop a practical model for DIA, to test the DIA model, and to provide recommendations to better support changes in data warehouse source systems. These goals resulted in the following main problem statement: How can a Delta Impact Analysis model be designed that supports the process of analyzing the impact of changes in a data warehouse source system situation?  Approach  The research approach is based on the design science framework by Hevner in combination with action science theory to validate the resulting DIA model from the research. The design science perspective resulted in an approach that is both rigorous, by performing a literature study, and relevant, by applying the research to practice. The research started by investigating the concept of DIA in practice at BI4U, in order to provide more insight into what it comprehends and what was relevant for the focus of the research. Next a thorough literature study was performed. Finally an artifact was proposed, a model for the process of DIA, which was validated in practice with a field study."
"We study sliding window multi-join processing in continuous queries over data streams. Several algorithms are reported for performing continuous, incremental joins, under the assumption that all the sliding windows fit in main memory. The algorithms include multiway incremental nested loop joins (NLJs) and multi-way incremental hash joins. We also propose join ordering heuristics to minimize the processing cost per unit time. We test a possible implementation of these algorithms and show that, as expected, hash joins are faster than NLJs for performing equi-joins, and that the overall processing cost is influenced by the strategies used to remove expired tuples from the sliding windows."
"Our goal is to enhance multidimensional database systems with a suite of advanced operators to automate data analysis tasks that are currently handled through manual exploration. In this paper, we present a key component of our system that characterizes the information content of a cell based on a user's prior familiarity with the cube and provides a context-sensitive exploration of the cube. There are three main modules of this component. A Tracker, that continuously tracks the parts of the cube that a user has visited. A Modeler, that pieces together the information in the visited parts to model the user's expected values in the unvisited parts. An Informer, that processes user's queries about the most informative unvisited parts of the cube. The mathematical basis for the expected value modeling is provided by the classical maximum entropy principle. Accordingly, the expected values are computed so as to agree with every value that is already visited while reducing assumptions about unvisited values to the minimum by maximizing their entropy. The most informative values are defined as those that bring the new expected values closest to the actual values. We believe and prove through experiments that such a user-in-the-loop exploration will enable much faster assimilation of all significant information in the data compared to existing manual explorations."
"It is neither desirable nor possible to abstract sensor network software from the characteristics of the underlying hardware components. In particular the radio has a major impact on higher level software. In this paper, we review the lessons we learnt using Bluetooth radios in the context of sensor networks. These lessons are relevant for (a) application designers choosing the best radio given a set of requirements and for (b) researchers in the data management community who need to formulate assumptions about underlying sensor networks."
"The increasing performance and decreasing cost of processors and memory are causing system intelligence to move into peripherals from the CPU. Storage system designers are using this trend toward ¡°excess¡± compute power to perform more complex processing and optimizations inside storage devices. To date, such optimizations have been at relatively low levels of the storage protocol. At the same time, trends in storage density, mechanics, and electronics are eliminating the bottleneck in moving data off the media and putting pressure on interconnects and host processors to move data more efficiently. We propose a system called Active Disks that takes advantage of processing power on individual disk drives to run application-level code. Moving portions of an application¡¯s processing to execute directly at disk drives can dramatically reduce data traffic and take advantage of the storage parallelism already present in large systems today. "
"In this paper we study how to build an effective incremental crawler. The crawler selectively and incrementally updates its index and/or local collection of web pages, instead of periodically refreshing the collection in batch mode. The incremental crawler can improve the ``freshness'' of the collection significantly and bring in new pages in a more timely manner. We first present results from an experiment conducted on more than half million web pages over 4 months, to estimate how web pages evolve over time. Based on these experimental results, we compare various design choices for an incremental crawler and discuss their trade-offs. We propose an architecture for the incremental crawler, which combines the best design choices."
"Publisher Summary This chapter discusses the distributed workspaces with active XML. The tremendous evolution of the Web has brought the need for platforms allowing to easily deploy distributed data management applications. The current trend goes towards the de-centralization of such platforms, and in particular to peer-to-peer architectures. The active XML system provides a peer-to-peer data integration platform, based on Web standards such as XML, and Web services. The system is centered on Active XML system (AXML) documents: XML documents where parts of the content are explicit XML data, whereas other parts are dynamically generated by calls to Web services on the same or on other peers. By including web service calls, AXML documents already have an inherent form of distributed computation."
"In the data warehousing approach to the integration of data from multiple information sources, selected information is extracted in advance and stored in a repository. A data warehouse (DW) can therefore be seen as a set of materialized views defined over the sources. When a query is posed, it is evaluated locally, using the materialized views, without accessing the original information sources. The applications using DWs require high query performance. This requirement is in conflict with the need to maintain in the DW updated information. The DW configuration problem is the problem of selecting a set of views to materialize in the DW that answers all the queries of interest while minimizing the total query evaluation and view maintenance cost. In this paper we provide a theoretical framework for this problem in terms of the relational model. We develop a method for dealing with it by formulating it as a state space optimization problem and then solving it using an exhaustive incremental algorithm as well as a *Research supported by the European Commission under the ESPRIT Program LTR project No 22469 ¡°DWQ: Foundations of Data Warehouse Quality¡± heuristic one. We extend this method by considering the case where auxiliary views are stored in the DW solely for reducing the view maintenance cost."
"There is not appropriate testing method for the purchasing process of sealing washer in hydraulic support producing company at present.In order to solve the problem,by using the performance testing system of sealing washer worked upright column for hydraulic support,the author designed a test bed used to test the seal performance of hydraulic cylinder in the mine hydraulic support to provide database supports for purchasing sealing washer for hydraulic support manufacturers.In this paper,there will be the introduction of the principles,constitutions and functions of the test bed.It is reflected by the practical applications that the test bed is operating stably,accurately and efficiently which could be used by testing sealing washer."
"Publisher Summary This chapter explores the basic functionality of the volume data model. It considers examples from biology and volumes of measurement from quantum physics. The data model is similar in the two cases, but the operations that are commonly used are quite different. In the second case, for instance, one is often interested in conditions on the behavior of local differential operators, such as zero-flow surfaces, while in the biological case one has a mix of value conditions and geometric condition. With these two application fields, this chapter highlights the generality and flexibility of the model. The system is based on a commercial database, augmented with specialized functions to manipulate the volume data model. The chapter demonstrates various operations specifying queries both using a graphical user interface and entering them directly in structured query language (SQL) augmented with the volume algebra operations."
"Commercial parallel database systems such as DB2 Parallel Edition (DB2 PE) [l, 21 are delivering the ability to execute complex queries on very large databases. However, the serial application interface to these database systems can become a bottleneck for a growing list of applications such as mailing list generation and data propagation from a warehouse to smaller data marts. In this abstract, we describe the CURRENT NODE and NODENUMBER functions provided by DB2 PE and show how these two functions can be used to retrieve data in parallel in a linearly scalable manner with respect to the number of nodes in the system. Before proceeding further, we should point out that DB2 PE uses a hash partitioning strategy to distribute rows of a table to nodes in a nodegroup which is a user-specified subset of system nodes. We apply a system-specified hashing function on the user-specified partitioning key values to generate a partition number. This number is used as an index into a partition map (which can be modified by users) to find the node number where the row will be stored."
"A data warehouse is a repository of integrated information from distributed, autonomous, and possibly heterogeneous, sources. In effect, the warehouse stores one or more materialized views of the source data. The data is then readily available to user applications for querying and analysis. Figure 1 shows the basic architecture of a warehouse: data is collected from each source, integrated with data from other sources, and stored at the warehouse. Users then access the data directly from the warehouse."
I'm happy to be able to share with you the following three reminiscences. I continue to invite unsolicited contributions. See http://www.acm.org/sigmod/record/author.html for submission guidelines.
"Querying XML documents typically involves both tree-based navigation and pattern matching similar to that used in structured information retrieval domains. In this paper, we show that for good performance, a native XML query processing system should support query plans that mix these two processing paradigms. We describe our prototype native XML system, and report on experiments demonstrating that even for simple queries, there are a number of options for how to combine tree-based navigation and structural joins based on information retrieval-style inverted lists, and that these options can have widely varying performance. We present ways of transparently using both techniques in a single system, and provide a cost model for identifying efficient combinations of the techniques. Our preliminary experimental results prove the viability of our approach."
"In this paper, we propose a novel approach for estimating the record selectivities of database queries. The real attribute value distribution is adaptively approximated by a curve-fitting function using a query feedback mechanism. This approach has the advantage of requiring no extra database access overhead for gathering statistics and of being able to continuously adapt the value distribution through queries and updates. Experimental results show that the estimation accuracy of this approach is comparable to traditional methods based on statistics gathering."
"Many real-time database applications arise in electronic financial services, safety-critical installations and military systems where enforcing is crucial to the success of the enterprise. We investigate here the performance implications, in terms of killed transactions, of guaranteeing multi-level secrecy in a real-time database system supporting applications with firm deadlines. In particular, we focus on the buffer management aspects of this issue.Our main contributions are the following. First, we identify the importance and difficulties of providing secure buffer management in the real-time database environment. Second, we present , a novel buffer management algorithm that provides covert-channel-free security. SABRE employs a fully dynamic one-copy allocation policy for efficient usage of buffer resources. It also incorporates several optimizations for reducing the overall number of killed transactions and for decreasing the unfairness in the distribution of killed transactions across security levels. Third, using a detailed simulation model, the real-time performance of SABRE is evaluated against unsecure conventional and real-time buffer management policies for a variety of security-classified transaction workloads and system configurations. Our experiments show that SABRE provides security with only a modest drop in real-time performance. Finally, we evaluate SABRE's performance when augmented with the GUARD adaptive admission control policy. Our experiments show that this combination provides close to ideal fairness for real-time applications that can tolerate covert-channel bandwidths of up to one bit per second (a limit specified in military standards)."
"Businesses today are searching for information solutions that enable them to compete in the global marketplace. To minimize risk, these solutions must build on existing investments, permit the best technology to be applied to the problem, and be manageable."
"A materialized view or Materialized Query Table (MQT) is an auxiliary table with precomputed data that can be used to significantly improve the performance of a database query. A Materialized Query Table Advisor (MQTA) is often used to recommend and create MQTs. The state-of-the-art MQTA works in a standalone database server where MQTs are placed on the same server as that in which the base tables are located. The MQTA does not apply to a federated or scaleout scenario in which MQTs need to be placed on other servers close to applications (i.e. a frontend database server) for offloading the workload on the backend database server. In this paper, we propose a Data Placement Advisor (DPA) and load balancing strategies for multi-tiered database systems. Built on top of the MQTA, DPA recommends MQTs and advises placement strategies for minimizing the response time for a query workload. To demonstrate the benefit of the data placement advising, we implemented a prototype of DPA that works with the MQTA in the IBM^(R) DB2^(R) Universal Database(TM) (DB2 UDB) and the IBM WebSphere^(R) Information Integrator (WebSphere II). The evaluation results showed substantial improvements of workload response times when MQTs are intelligently recommended and placed on a frontend database server subject to space and load characteristics for TPC-H and OLAP type workloads."
"During the past few years our research efforts have been inspired by two different needs. On one hand, the number of non-expert users accessing databases is growing apace. On the other, information systems will no longer be characterized by a single centralized architecture, but rather by several heterogeneous component systems. In order to address such needs we have designed a new query system with both user-oriented and multidatabase features. The system's main components are an adaptive visual interface, providing the user with different and interchangeable interaction modalities, and a ¡°translation layer¡±, which creates and offers to the user the illusion of a single homogeneous schema out of several heterogeneous components. Both components are founded on a common ground, i.e. a formally defined and semantically rich data model, the Graph Model, and a minimal set of Graphical Primitives, in terms of which general query operations may be visually expressed. The Graph Model has a visual syntax, so that graphical operations can be applied on its components without unnecessary mappings, and an object-based semantics. The aim of this paper is twofold. We first present an overall view of the system architecture and then give a comprehensive description of the lower part of the system itself. In particular, we show how schemata expressed in different data models can be translated in terms of Graph Model, possibly by exploiting reverse engineering techniques. Moreover, we show how mappings can be established between well-known query languages and the Graphical Primitives. Finally, we describe in detail how queries expressed by using the Graphical Primitives can be translated in terms of relational expressions so to be processed by actual DBMSs."
"As the size of data warehouses increase to several hundreds of gigabytes or terabytes, the need for methods and tools that will automate the process of knowledge extraction, or guide the user to subsets of the dataset that are of particular interest, is becoming prominent. In this survey paper we explore the problem of identifying and extracting interesting knowledge from large collections of data residing in data warehouses, by using data mining techniques. Such techniques have the ability to identify patterns and build succinct models to describe the data. These models can also be used to achieve summarization and approximation. We review the associated work in the OLAP, data mining, and approximate query answering literature. We discuss the need for the traditional data mining techniques to adapt, and accommodate the specific characteristics of OLAP systems. We also examine the notion of interestingness of data, as a tool to guide the analysis process. We describe methods that have been proposed in the literature for determining what is interesting to the user and what is not, and how these approaches can be incorporated in the data mining algorithms."
"We provide a principled extension of SQL, called SchemaSQL, that offers the capability of uniform manipulation of data and schema in relational multidatabase systems. We develop a precise syntax and semantics of SchemaSQL in a manner that extends traditional SQL syntax and semantics, and demonstrate the following. (1) SchemaSQL retains the flavor of SQL while supporting querying of both data and schema. (2) It can be used to transform data in a database in a structure substantially different from original database, in which data and schema may be interchanged. (3) It also permits the creation of views whose schema is dynamically dependent on the contents of the input instance. (4) While aggregation in SQL is restricted to values occurring in one column at a time, SchemaSQL permits ""horizontal"" aggregation and even aggregation over more general ""blocks"" of information. (5) SchemaSQL provides a useful facility for interoperability and data/schema manipulation in relational multidatabase systems. We provide many examples to illustrate our claims. We clearly spell out the formal semantics of SchemaSQL that accounts for all these features. We describe an architecture for the implementation of SchemaSQL and develop implementation algorithms based on available database technology that allows for powerful integration of SQL based relational DBMS. We also discuss the applicability of SchemaSQL for handling semantic heterogeneity arising in a multidatabase system."
"Index tuning as part of database tuning is the task of selecting and creating indexes with the goal of reducing query processing times. However, in dynamic environments with various ad-hoc queries it is difficult to identify potential useful indexes in advance. In this demonstration, we present our tool QUIET addressing this problem. This tool ""intercepts"" queries and - based on a cost model as well as runtime statistics about profits of index configurations - decides about index creation automatically at runtime. In this way, index tuning is driven by queries without explicit actions of the database users."
"Implementing crash recovery in an Object-Oriented Database System (OODBMS) raises several challenging issues for performance that are not present in traditional DBMSs. These performance concerns result both from significant architectural differences between OODBMSs and traditional database systems and differences in OODBMS's target applications. This paper compares the performance of several alternative approaches to implementing crash recovery in an OODBMS based on a client-server architecture. The four basic recovery techniques examined in the paper are termed page differencing, sub-page differencing, whole-page logging, and redo-at-server. All of the recovery techniques were implemented in the context of QuickStore, a memory-mapped store built using the EXODUS Storage Manager, and their performance is compared using the OO7 database benchmark. The results of the performance study show that the techniques based on differencing generally provide superior performance to whole-page logging."
"The Microsoft Repository is an object-oriented repository that ships as a component of Visual Basic (Version 5.0). It includes a set of ActiveX interfaces that a developer can use to define information models, and a repository engine that is the underlying storage mechanism for these information models. The repository engine sits on top of a SQL database system. The repository is designed to meet the persistent storage needs of software tools. Its two main technical goals are: . compatibility with Microsoft¡¯s existing ActiveX object architecture consisting of the Component Object Model (COM) and Automation and that a developer can use to define information models, and a repository engine that is the underlying storage mechanism for these information ¡®models. (Znformurion model is repository terminology for database schema [3].) The repository engine sits on top of either Microsoft SQL Server or Microsoft Jet (the database system in Microsoft Access) and supports both navigational access via the object-oriented interfaces and direct SQL access to the underlying store. In addition, the Repository includes a set of information models that cover the data sharing needs of software tools. . extensibility by customers and independent software vendors who need to tailor the repository by adding functionality to objects stored by the repository engine and extending information models provided by Microsoft and others. "
"This annotated bibliography presents a collection of published papers, technical reports, Master's and PhD Theses that have investigated various aspects of object database performance."
"Queries on XML documents typically combine selections on element contents, and, via path expressions, the structural relationships between tagged elements. Structural joins are used to find all pairs of elements satisfying the primitive structural relationships specified in the query, namely, parent-child and ancestor-descendant relationships. Efficient support for structural joins is thus the key to efficient implementations of XML queries. Recently proposed node numbering schemes enable the capturing of the XML document structure using traditional indices (such as B+-trees or R-trees). This paper proposes efficient structural join algorithms in the presence of tag indices. We first concentrate on using B+- trees and show how to expedite a structural join by avoiding collections of elements that do not participate in the join. We then introduce an enhancement (based on sibling pointers) that further improves performance. Such sibling pointers are easily implemented and dynamically maintainable. We also present a structural join algorithm that utilizes R-trees. An extensive experimental comparison shows that the B+-tree structural joins are more robust. Furthermore, they provide drastic improvement gains over the current state of the art."
"This paper presents the design of a read-optimized relational DBMS that contrasts sharply with most current systems, which are write-optimized. Among the many differences in its design are: storage of data by column rather than by row, careful coding and packing of objects into storage including main memory during query processing, storing an overlapping collection of column-oriented projections, rather than the current fare of tables and indexes, a non-traditional implementation of transactions which includes high availability and snapshot isolation for read-only transactions, and the extensive use of bitmap indexes to complement B-tree structures."
"Data Preprocessing for Data Mining addresses one of the most important issues within the well-known Knowledge Discovery from Data process. Data directly taken from the source will likely have inconsistencies, errors or most importantly, it is not ready to be considered for a data mining process. Furthermore, the increasing amount of data in recent science, industry and business applications, calls to the requirement of more complex tools to analyze it. Thanks to data preprocessing, it is possible to convert the impossible into possible, adapting the data to fulfill the input demands of each data mining algorithm."
"This paper introduces bifocal sampling, a new technique for estimating the size of an equi-join of two relations. Bifocal sampling classifies tuples in each relation into two groups, sparse and dense, based on the number of tuples with the same join value. Distinct estimation procedures are employed that focus on various combinations for joining tuples (e.g., for estimating the number of joining tuples that are dense in both relations). This combination of estimation procedures overcomes some well-known problems in previous schemes, enabling good estimates with no a priori knowledge about the data distribution. The estimate obtained by the bifocal sampling algorithm is proven to lie with high probability within a small constant factor of the actual join size, regardless of the skew, as long as the join size is &Omega;(n lg n), for relations consisting of n tuples. The algorithm requires a sample of size at most O(&radic;n lg n). By contrast, previous algorithms using a sample of similar size may require the join size to be &Omega;(n&radic;n) to guarantee an accurate estimate. Experimental results support the theoretical claims and show that bifocal sampling is practical and effective."
"XML stream applications bring the challenge of efficiently processing queries on sequentially accessible token-based data. While the automata model is naturally suited for pattern matching on tokenized XML streams, the algebraic model in contrast is a well-established technique for set-oriented processing of self-contained tuples. However, neither automata nor algebraic models are well-equipped to handle both computation paradigms."
"Deduplication, a key operation in integrating data from multiple sources, is a time-consuming, labor-intensive and domain-specific operation. We present our design of ALIAS that uses a novel approach to ease this task by limiting the manual effort to inputing simple, domain-specific attribute similarity functions and interactively labeling a small number of record pairs. We describe how active learning is useful in selecting informative examples of duplicates and nonduplicates that can be used to train a deduplication function. ALIAS provides mechanism for efficiently applying the function on large lists of records using a novel cluster-based execution model."
"Recent developments in spatial relations have led to their use in numerous applications involving spatial databases. This paper is concerned with the retrieval of topological relations in Minimum Bounding Rectangle-based data structures. We study the topological information that Minimum Bounding Rectangles convey about the actual objects they enclose, using the concept of projections. Then we apply the results to R-trees and their variations, R+-trees and R*-trees in order to minimise disk accesses for queries involving topological relations. We also investigate queries that involve complex spatial conditions in the form of disjunctions and conjunctions and we discuss possible extensions."
"The database volumes of enterprise resource planning (ERP) systems like SAP R/3 are growing at a tremendous rate and some of them have already reached a size of several Terabytes. OLTP (Online Transaction Processing) databases of this size are hard to maintain and tend to perform poorly. Therefore most database vendors have implemented new features like horizontal partitioning to optimize such mission critical applications. Horizontal partitioning was already investigated in detail in the context of shared nothing distributed database systems but today's ERP systems mostly use a centralized database with a shared everything architecture. In this work, we therefore investigate how an SAP R/3 system performs when the data in the underlying database is partitioned horizontally. "
"This is a bibliography on active databases and active database systems which reflects the various research activities in this field. We compiled this bibliography for our own use, but hopefully it might be useful to other people as well. All papers that appear in the following list, are generally accessible.We do not claim that the bibliography is exhaustive and covers the complete range of literature that deals with activities. We decided to focus on central approaches, concepts, methods, and systems in the area of active databases. It does not contain entries in the area of ""pure"" real-time, object-oriented, temporal, and deductive databases. But we did include publications related to those approaches, as long as they discuss active databases.We divided the material into various sections following our own personal perception of the field. The sections provide an overview on different projects in the area of active databases, followed by sections on relevant research topics. Each section contains a few remarks followed by a list of cross references into the annotated bibliography. Papers might appear in more than one section in case they discuss different topics relevant to different sections.Additionally, when relevant we also included unpublished, but publicly available material. For those papers we included information how to obtain them from the authors or from the organizations where the were produced.The beauty of our work is the individual annotation to almost all publications. Due to space limitations we are forced to leave out those annotations in the version published here. For a complete annotated bibliography we refer to the entry in our WWW server.The effort to build up such a bibliography is an endless task."
"An increasing number of applications use XML data published from relational databases. For speed and convenience, such applications routinely cache this XML data locally and access it through standard navigational interfaces such as DOM, sacrificing the consistency and integrity guarantees provided by a DBMS for speed. The ROLEX system is being built to extend the capabilities of relational database systems to deliver fast, consistent and navigable XML views of relational data to an application via a virtual DOM interface. This interface translates navigation operations on a DOM tree into execution-plan actions, allowing a spectrum of possibilities for lazy materialization. The ROLEX query optimizer uses a characterization of the navigation behavior of an application, and optimizes view queries to minimize the expected cost of that navigation. This paper presents the architecture of ROLEX, including its model of query execution and the query optimizer. We demonstrate with a performance study the advantages of the ROLEX approach and the importance of optimizing query execution for navigation."
"The MIROWeb Espris developped a unique technology to integrate multiple data sources through an object-relational model with semistructured data types. In addresses the problem of integrating irregular web sources and regular relational databases through a mediated architecture based on hybrid model, supporting relational object and semi-structured features. The project data exchange format is XML, the new standard of the Web and the pivot language is XMLQL, a query language based on XML templates from AT&T. The demonstration will show the data warehousing approach for mediation, based on Oracle 8 and a semi-structured cartridge developped in the project for supporting XML and XMLQL queries."
"We present a functional paradigm for querying efficiently abstract collections of complex objects. Abstract collections are used to model class extents, multivalued attributes as well as indexes or hashing tables. Our paradigm includes a functional language called OFL (Object Functional Language) and a supporting execution model based on graph traversals. OFL is able to support any complex object algebra with recursion as macros. It is an appropriate target language for OQL-like query compilers. The execution model provides various strategies including set-oriented and pipelined traversals. OFL has been implemented on top of an object manager. Measures of a typical query extracted from a geographical benchmark show the value of hybrid strategies integrating pipelined and set-oriented evaluations. They also show the potential of function result memorization, a typical optimization approach known as ""Memoization"" 2 in functional languages."
"Water has an outstanding importance for the life on earth. From this results the necessity for the monitoring and interpretation of mari ne data. For that, the visual analysis is a suitable and effective tool, whereby special demands arise from the heterogeneity of data (different data type s, different data sources), the quality of data (missing values, incorrect values ), and the large quantity of data. The visualization of marine data is particularly import ant within both their geographic context and their temporal course. First, this paper introduces a classification for the visualization of spatial and ti me related data, which is not only appropriate for marine data. Following special visual ization and interaction techniques for marine data are discussed. Thereby we do not raise the claim, to create new visualization paradigms. Rather we want to show solution concepts and special methods using well known paradigms for a special and complex application area, but also to address limits of the visualization paradigms in these applications."
"ANSI SQL-92 [MS, ANSI] defines Isolation Levels in terms of phenomena: Dirty Reads, Non-Repeatable Reads, and Phantoms. This paper shows that these phenomena and the ANSI SQL definitions fail to properly characterize several popular isolation levels, including the standard locking implementations of the levels covered. Ambiguity in the statement of the phenomena is investigated and a more formal statement is arrived at; in addition new phenomena that better characterize isolation types are introduced. Finally, an important multiversion isolation type, called Snapshot Isolation, is defined."
"Response time is a key differentiation among electronic commerce (e-commerce) applications. For many e-commerce applications, Web pages are created dynamically based on the current state of a business stored in database systems. Recently, the topic of Web acceleration for database-driven Web applications has drawn a lot of attention in both the research community and commercial arena. In this paper, we analyze the factors that have impacts on the performance and scalability of Web applications. We discuss system architecture issues and describe approaches to deploying caching solutions for accelerating Web applications. We give the performance matrix measurement for network latency and various system architectures. The paper is summarized with a road map for creating high performance Web applications."
"Web servers are increasingly being used to deliver dynamic content rather than static HTML pages. In order to generate web pages dynamically, servers need to execute a script, which typically connects to a DBMS. Although CGI was the first approach at server side scripting, it has significant performance shortcomings. Currently, there are many alternative server side scripting architectures which offer better performance than CGI. In this paper, we report our experiences using mod_perl, an Apache Server module, which can improve the performance of CGI scripts by at least an order of magnitude. Except for presenting results from our experiments, we also briefly describe the implementation of an industrial strength database-backed web site that we recently built and give a quick overview of the various server-side scripting mechanisms."
"Traditionally, database systems have been evaluated in isolation on the basis of standardized benchmarks (e.g., Wisconsin, TPC-C, TPC-D). We argue that very often such a performance analysis does not reflect the actual use of the DBMSs in the ¡°real world.¡± End users typically don't access a stand-alone database system; rather they use a comprehensive application system, in which the database system constitutes an integrated component. In order to derive performance evaluations of practical relevance to the end users, the application system including the database system has to be benchmarked. In this paper, we present TPC-D benchmark results carried out using the SAP R/3 system, an integrated business administration system. Like many other application systems SAP R/3 is based on a commercial relational database system. We compare the SAP R/3 benchmark results with TPC-D results of an isolated database system, the database product that served as SAP R/3's back-end."
"To meet the needs of many real-world control applications, concepts from Temporal, Real-Time, and Active Databasesmust be integrated: Since the system¡¯s data is supposedto reflect the environment being controlled, theymust be updated frequently tomaintain temporal validity; Many activities, including those that perform the updates, work under time constraints; The occurrence of events, for example, emergency events, trigger actions. In these systems, meeting timeliness, predictability, and QoS guarantee requirements ¨C through appropriate resource and overload management ¨C become very important. So, algorithms and protocols for concurrency control, recovery, and scheduling are needed. These algorithms must exploit semantics of the data and the transactions to be responsive and efficient. Whereas time cognizant scheduling,concurrency control and conflict resolution have been studied in the literature, recovery issues have not. We have developed strategies for data placement at the appropriate level of memory hierarchy, for avoiding undoing/redoing by exploiting data/transaction characteristics, and for placing logs at the appropriate level in the memory hierarchy. Another issue that we have studied deals with the assignment of priority to transactions in active real-time database systems. We are also studying concurrency control for temporal and multi-media data. We have built RADEx, a simulation environment to evaluate our solutions."
"In this paper we describe the design and implementation of OPT++, a tool for extensible database query optimization that uses an object-oriented design to simplify the task of implementing, extending, and modifying an optimizer. Building an optimizer using OPT++ makes it easy to extend the query algebra (to add new query algebra operators and physical implementation algorithms to the system), easy to change the search space, and also to change the search strategy. Furthermore, OPT++ comes equipped with a number of search strategies that are available for use by an optimizer-implementor. OPT++ considerably simplifies both, the task of implementing an optimizer for a new database system, and the task of evaluating alternative optimization techniques and strategies to decide what techniques are best suited for that database system. We present the results of a series of performance studies. These results validate our design and show that, in spite of its flexibility, OPT++ can be used to build efficient optimizers."
"We present an external-memory algorithm for computing a minimum-cost edit script between two rooted, ordered, labeled trees. The I/O, RAM, and CPU costs of our algorithm are, respectively, 4 7 5 , 6 , and 1 5 , where and are the input tree sizes, is the block size, , and . This algorithm can make effective use of surplus RAM capacity to quadratically reduce I/O cost. We extend to trees the commonly used mapping from sequence comparison problems to shortest-path problems in edit graphs."
"Temporal data is pervasive, and challenging to manage in SQL. The June through October issues of Database Programming and Design (volume 11, issues 6¨C10) included a special series on temporal databases; the five articles in that series are reproduced here. Three separate case studies: a neonatal intensive care unit, a commercial cattle feed yard, and astronomical star catalogs, were used to illustrate how temporal applications can be implemented in SQL. The concepts of valid time versus transaction time and of current, sequenced and nonsequenced integrity constraints, queries, and modifications were emphasized. 1 Of Duplicates and Septuplets This special series explores the many issues that arise when attempting to define and manage time-varying data. Such data is pervasive. It has been estimated that one of every 50 lines of database application code involves a date or time value. Data warehouses are by definition time-varying: Ralph Kimball states that every data warehouse has a time dimension. Often the time-oriented nature of the data is what lends it value. DBAs and application programmers constantly wrestle with the vagaries of such data. They find that overlaying simple concepts, such as duplicate prevention, on time-varying data can be surprisingly subtle and complex. And they are perplexed that trade publications and books do not provide guidance and techniques for handling such data. "
"Many of today¡¯s applications need massive real-time data processing. In-memory database systems have become a good alternative for these requirements. These systems maintain the primary copy of the database in the main memory to achieve high throughput rates and low latency. However, a database in RAM is more vulnerable to failures than in traditional disk-oriented databases because of the memory volatility. DBMSs implement recovery activities (logging, checkpoint, and restart) for recovery proposes. Although the recovery component looks similar in disk- and memory-oriented systems, these systems differ dramatically in the way they implement their architectural components, such as data storage, indexing, concurrency control, query processing, durability, and recovery. This survey aims to provide a thorough review of in-memory database recovery techniques. To achieve this goal, we reviewed the main concepts of database recovery and architectural choices to implement an in-memory database system. Only then, we present the techniques to recover in-memory databases and discuss the recovery strategies of a representative sample of modern in-memory databases."
"OdeFS is a file-like interface to the Ode objectoriented database. OdeFS allows database objects to be accessed and manipulated with standard commands, just like files in a traditional file system. No recompilation is required, so proprietary applications can access Ode objects. OdeFS is implemented as a network file server, using the NFS protocol. This paper describes OdeFS and its implementation."
"The notion of variable independence was introduced by Chomicki, Goldin, and Kuper in their PODS'96 paper as a means of adding a limited form of aggregation to constraint query languages while retaining the closure property. Later, Grumbach, Rigoux and Segoufin showed in their ICDT'99 paper that variable independence and a related notion of orthographic dimension are useful tools for optimizing constraint queries."
"Integrity constraint checking for stratifiable deductive databases has been studied by many authors. However, most of these methods may perform unnecessary checking if the update is irrelevant to the constraints. [Lee94] proposed a set called relevant set which can be incorporated in these works to reduce unnecessary checking. [Lee94] adopts a top-down approach and makes use of constants and evaluable functions in the constraints and deductive rules to reduce the search space. In this paper, we further extend this idea to make use of relational predicates, instead of only constants and evaluable functions in [Lee94]. We first show that this extension is not a trivial one as extra database retrieval cost is incurred. We then present a new method to construct a pre-test which can be incorporated in most existing methods to reduce the average checking costs in terms of database accesses by a significant factor. Our method also differs from other partial checking methods as we can handle multiple updates."
"In a lazy master replicated database, a transaction can commit after updating one replica copy (primary copy) at some master node. After the transaction commits, the updates are propagated towards the other replicas (secondary copies), which are updated in separate refresh transactions. A central problem is the design of algorithms that maintain replica's consistency while at the same time minimizing the performance degradation due to the synchronization of refresh transactions. In this paper, we propose a simple and general refreshment algorithm that solves this problem and we prove its correctness. The principle of the algorithm is to let refresh transactions wait for a certain ¡°deliver time¡± before being executed at a node having secondary copies. We then present two main optimizations to this algorithm. One is based on specific properties of the topology of replica distribution across nodes. In particular, we characterize the nodes for which the deliver time can be null. The other improves the refreshment algorithm by using an immediate update propagation strategy."
"This paper describes the architecture and performance of ORACLE, an approach for detecting a unique radio from a large pool of bit-similar devices (same hardware, protocol, physical address, MAC ID) using only IQ samples at the physical layer. ORACLE trains a convolutional neural network (CNN) that balances computational time and accuracy, showing 99% classification accuracy for a 16-node USRP X310 SDR testbed and an external database of >100 COTS WiFi devices. "
"This paper deals with finding outliers (exceptions) in large, multidimensional datasets. The identification of outliers can lead to the discovery of truly unexpected knowledge in areas such as electronic commerce, credit card fraud, and even the analysis of performance statistics of professional athletes. Existing methods that we have seen for finding outliers in large datasets can only deal efficiently with two dimensions/attributes of a dataset. Here, we study the notion of DB- (DistanceBased) outliers. While we provide formal and empirical evidence showing the usefulness of DB-outliers, we focus on the development of algorithms for computing such outliers. First, we present two simple algorithms, both having a complexity of O(k N¡¯), k being the dimensionality and N being the number of objects in the dataset. These algorithms readily support datasets with many more than two attributes. Second, we present an optimized cell-based algorithm that has a complexity that is linear wrt N, but exponential wrt k. Third, for datasets that are mainly disk-resident, we present another version of the cell-based algorithm that guarantees at most 3 passes over a dataset. We provide"
"Physical database design is important for query performance in a shared-nothing parallel database system, in which data is horizontally partitioned among multiple independent nodes. We seek to automate the process of data partitioning. Given a workload of SQL statements, we seek to determine automatically how to partition the base data across multiple nodes to achieve overall optimal (or close to optimal) performance for that workload. Previous attempts use heuristic rules to make those decisions. These approaches fail to consider all of the interdependent aspects of query performance typically modeled by today's sophisticated query optimizers.We present a comprehensive solution to the problem that has been tightly integrated with the optimizer of a commercial shared-nothing parallel database system. Our approach uses the query optimizer itself both to recommend candidate partitions for each table that will benefit each query in the workload, and to evaluate various combinations of these candidates. We compare a rank-based enumeration method with a random-based one. Our experimental results show that the former is more effective."
"Fast indexing in time sequence databases for similarity searching has attracted a lot of research recently. Most of the proposals, however, typically centered around the Euclidean distance and its derivatives. We examine the problem of multimodal similarity search in which users can choose the best one from multiple similarity models for their needs. In this paper, we present a novel and fast indexing scheme for time sequences, when the distance function is any of arbitrary Lp norms (p = 1; 2; : : : ;1). One feature of the proposed method is that only one index structure is needed for all Lp norms including the popular Euclidean distance (L2 norm). Our scheme achieves significant speedups over the state of the art: extensive experiments on real and synthetic time sequences show that the proposed method is comparable to the best competitor forL2 andL1 norms, but significantly (up to 10 times) faster for L1 norm."
"Recent research activities in the area of Temporal Databases have revealed some problems related to the definition of time. In this paper we discuss the problem arising from the definition of valid time and the assumptions about valid time, which exist in current Temporal Database approaches. For this problem we propose a solution, while we identify some consistency problems that may appear in Temporal Databases, and which require further investigation."
"Expert database systems extend the functionality of conventional database systems by providing a facility for creating and automatically executing Condition-Action rules. While Condition-Action rules in database systems are very powerful, they also can be very difficult to program, due to the unstructured and unpredictable nature of rule processing. We provide methods for static analysis of Condition-Action rules; our methods determine whether a given rule set is guaranteed to terminate, and whether rule execution is confluent (has a guaranteed unique final state). Our methods are based on previous methods for analyzing rules in active database systems. We improve considerably on the previous methods by providing analysis criteria that are much less conservative: our methods often determine that a rule set will terminate or is confluent when previous methods could not. Our improved analysis is based on a ``propagation'''' algorithm, which uses a formal approach based on an extended relational algebra to accurately determine when the action of one rule can affect the condition of another. Our algebraic approach yields methods that are applicable to a broad class of expert database rule languages."
"Abstract. The view selection problem is to choose a set of views to materialize over a database schema, such that the cost of evaluating a set of workload queries is minimized and such that the views fit into a prespecified storage constraint. The two main applications of the view selection problem are materializing views in a database to speed up query processing, and selecting views to materialize in a data warehouse to answer decision support queries. In addition, view selection is a core problem for intelligent data placement over a wide-area network for data integration applications and data management for ubiquitous computing. We describe several fundamental results concerning the view selection problem. We consider the problem for views and workloads that consist of equality-selection, project and join queries, and show that the complexity of the problem depends crucially on the quality of the estimates that a query optimizer has on the size of the views it is considering to materialize. When a query optimizer has good estimates of the sizes of the views, we show a somewhat surprising result, namely, that an optimal choice of views may involve a number of views that is exponential in the size of the database schema. On the other hand, when an optimizer uses standard estimation heuristics, we show that the number of necessary views and the expression size of each view are polynomially bounded."
"This paper reports on the principles underlying the semantic and pedagogic interoperability mechanisms built in the European Knowledge Pool System, developed by the European research project ARIADNE. This system, which is the central feature of ARIADNE, consists in a distributed repository of pedagogical documents (or learning objects) of diverse granularity, origin, content, type, language, etc., which are stored in view of their use (and reuse) in telematics-based training or teaching curricula. The learning objects are indexed, usually by faculty staff, according to the ARIADNE metadata set. The principles embodied in the indexation tool, which interacts directly with the repository,stem from a few theoretical ideas but foremost from empirical, pragmatic considerations, suggested by the context of actual use. They tentatively address the stringent demands for semantic and pedagogic interoperability implied by a context of rather wide cultural and linguistic diversity, as well as those stemming from the very nature of the domain application itself: education and training. Possible extensions to the educational metadata scheme developed by ARIADNE on these basis, may accommodate corporate training/information needs. These extensions are briefly discussed as a mean for enhancing 'semantic' interoperability between different (kinds of) corporations. Finally, the architecture of the ARIADNE system, which heavily relies on this educational metadata system, is briefly reviewed."
"This paper presents general algorithms for concurrency control in tree-based access methods as well as a recovery protocol and a mechanism for ensuring repeatable read. The algorithms are developed in the context of the Generalized Search Tree (GiST) data structure, an index structure supporting an extensible set of queries and data types. Although developed in a GiST context, the algorithms are generally applicable to many tree-based access methods. The concurrency control protocol is based on an extension of the link technique originally developed for B-trees, and completely avoids holding node locks during I/Os. Repeatable read isolation is achieved with a novel combination of predicate locks and two-phase locking of data records. To our knowledge, this is the first time that isolation issues have been addressed outside the context of B-trees. A discussion of the fundamental structural differences between B-trees and more general tree structures like GiSTs explains why the algorithms developed here deviate from their B-tree counterparts. An implementation of GiSTs emulating B-trees in DB2/Common Server is underway."
"The cost of a query plan depends on many parameters, such as predicate selectivities and available memory, whose values may not be known at optimization time. Parametric query optimization (PQO) optimizes a query into a number of candidate plans, each optimal for some region of the parameter space."
"String data is ubiquitous, and its management has taken on particular importance in the past few years. Approximate queries are very important on string data especially for more complex queries involving joins. This is due, for example, to the prevalence of typographical errors in data, and multiple conventions for recording attributes such as name and address. Commercial databases do not support approximate string joins directly, and it is a challenge to implement this functionality efficiently with user-defined functions (UDFs). In this paper, we develop a technique for building approximate string join capabilities on top of commercial databases by exploiting facilities already available in them. At the core, our technique relies on matching short substrings of length , called -grams, and taking into account both positions of individual matches and the total number of such matches. Our approach applies to both approximate full string matching and approximate substring matching, with a variety of possible edit distance functions. The approximate string match predicate, with a suitable edit distance threshold, can be mapped into a vanilla relational expression and optimized by conventional relational optimizers. We demonstrate experimentally the benefits of our technique over the direct use of UDFs, using commercial database systems and real data. To study the I/O and CPU behavior of approximate string join algorithms with variations in edit distance and -gram length, we also describe detailed experiments based on a prototype implementation."
"In this paper we examine the semantics and develop constructs for temporal data independent of any traditional data model, such as the relational or network data models. Unlike many other works which extend existing models to support temporal data, our purpose is to characterize the properties of temporal data and operators over them without being influenced by traditional models which were not specifically designed to model temporal data. We develop data constructs that represent sequences of temporal values, identify their semantic properties, and define operations over these structures."
A method for generating an approximate answer in response to a query to a database in which an SQL query Q for operating on a relation R in a database is received. Relation R has an associated histogram H. The SQL query Q is translated to be a query Q¡ä for operating on histogram H. Translated query Q¡ä is executed on histogram H for obtaining a result histogram. The result histogram is expanded into a relation having tuples containing approximate attribute values.
"The paper discusses the issue of views in the Web context. We introduce a set of languages for managing and restructuring data coming from the World Wide Web. We present a specific data model, called the ARANEUS Data Model, inspired to the structures typically present in Web sites. The model allows us to describe the scheme of a Web hypertext, in the spirit of databases. Based on the data model, we develop two languages to support a sophisticate view definition process: the first, called ULIXES, is used to build database views of the Web, which can then be analyzed and integrated using database techniques; the second, called PENELOPE, allows the definition of derived Web hypertexts from relational views. This can be used to generate hypertextual views over the Web."
"The buffer manager is integral to the performance, scalability, and reliability of Oracle¡¯s Universal Dam Server, a high performance object-relational database manager that provides robust data-management services for a variety of applications and tools. The rich functionality of the Universal Data Server poses special challenges to the design of the buffer manager. Buffer management algorithms must be scalable and efficient across a broad spectrum of OLTP, decision support, and multimedia workloads which impose very different concurrency, throughput and bandwidth requirements. The need for portability across a wide range of platforms further complicates buffer management; the database server must run efficiently with buffer pool sizes ranging from 50 buffers to several million buffers and on a wide variety of architectures including uniprocessors, shared-disk clusters, messagepassing MPP systems, and shared-memory muhiprocessors."
"Mining for a.ssociation rules between items in a large database of sales transactions has been described as an important database mining problem. In this paper we present an efficient algorithm for mining association rules that is fundamentally different from known algorithms. Compared to previous algorithms, our algorithm not only reduces the I/O overhead significantly but also has lower CPU overhead for most cases. We have performed extensive experiments and compared the performance of our algorithm with one of the best existing algorithms. It was found that for large databases, the CPU overhead was reduced by as much as a factor of four and I/O was reduced by almost an order of magnitude. Hence this algorithm is especially suitable for very large size databases."
"We describe an investigation into e-mail content mining for author identification, or authorship attribution, for the purpose of forensic investigation. We focus our discussion on the ability to discriminate between authors for the case of both aggregated e-mail topics as well as across different e-mail topics. An extended set of e-mail document features including structural characteristics and linguistic patterns were derived and, together with a Support Vector Machine learning algorithm, were used for mining the e-mail content. Experiments using a number of e-mail documents generated by different authors on a set of topics gave promising results for both aggregated and multi-topic author categorisation."
"Maintaining data consistency is known to be hard. Recent approaches have relied on integrity constraints to deal with the problem - correct and complete constraints naturally work towards data consistency. State-of-the-art data cleaning frameworks have used the formalism known as denial constraint (DC) to handle a wide range of real-world constraints. Each DC expresses a relationship between predicates that indicate which combinations of attribute values are inconsistent. The design of DCs, however, must keep pace with the complexity of data and applications."
"This paper defines a framework for explaining redo recovery after a system crash. In this framework, an installation graph explains the order in which operations must be installed into the stable database if it is to remain recoverable. This installation graph is a significantly weaker ordering on operations than the conflict graph from concurrency control. We use the installation graph to devise (i) a cache management algorithm for writing data from the volatile cache to the stable database, (ii) the specification of a REDO test used to choose the operations on the log to replay during recovery, and (iii) an idempotent recovery algorithm based on this test; and we prove that these cache management and recovery algorithms are correct. Most pragmatic recovery methods depend on constraining the kinds of operations that can appear in the log, but our framework allows arbitrary logged operations. We use our framework to explain pragmatic methods that constrain the logged operations to reading and writing single pages, and then using this new understanding to relax these constraints. The result is a new class of logged operations having a recovery method with practical advantages over current methods."
"While scaling up to the enormous and growing Internet population with unpredictable usage patterns, E-commerce applications face severe challenges in cost and manageability, especially for database servers that are deployed as those applications' backends in a multi-tier configuration. Middle-tier database caching is one solution to this problem. In this paper, we present a simple extension to the existing federated features in DB2 UDB, which enables a regular DB2 instance to become a DBCache without any application modification. On deployment of a DBCache at an application server, arbitrary SQL statements generated from the unchanged application that are intended for a backend database server, can be answered: at the cache, at the backend database server, or at both locations in a distributed manner. The factors that determine the distribution of workload include the SQL statement type, the cache content, the application requirement on data freshness, and cost-based optimization at the cache. We have developed a research prototype of DBCache, and conducted an extensive set of experiments with an E-Commerce benchmark to show the benefits of this approach and illustrate tradeoffs in caching considerations."
"1. Electronic Commerce Electronic commerce challenges our notions of distributed transactions in several ways. I discuss issues how distributed transactions can apply to electronic transactions, with special emphasis on the role of atomic@. I discuss the application of these ideas to two systems I have helped design and build: NetBill (a system for highly atomic micro-transactions) and Cryptographic Postage Indicia (a system for generating postage on laser printers attached to PCs or other devices.) I discuss the dijjficulties in integrating atomic, anonymous payment systems and some issues in supporting anonymous auctions. Finally, I conclude with a set of open questions. Electronic commerce is clearly among the most exciting developments in Internet based applications today. Here are some measures: Dell reports selling more than three million dollars worth of computers each day from their web site. Ernst & Young reports for that the online stores now offer the best prices for 90% of all consumer goods. 10% of all flower orders received by I-800-FLOWERS now arrive via the world wide web. Estimates vary on the amount of electronic commerce now occurring. Here is one measure of the excitement over electronic commerce: the 12 June 1995 issue of Business Week includes the following projection of the role of electronic commerce. This projection is probably overly optimistic, but it indicates that electronic commerce is being taken seriously in some quarters. *Effective September 1998, the author will hold a joint appointment in between the Electrical Engineering & Computer Science Department and the School of Information Management & Systems, both at the University of California, Berkeley, 94720. The author¡¯s e-mail addresses will be tygar@cs.berkeley.edu and tygar@sims.berkeley.edu. This work was in part supported by DARPA (Contract F19628-96-C0061). NSF (Cooperative Agreement IRI-9411299), and the US Postal Service. The U.S Government is authorized to reproduce and distribute reprints for government purposes, not withstanding any copyright notations thereon. The views and conclusions contained in this document are those of the author and should not be interpreted as reflecting the official policies, either expressed or implied, of any of the supporting agencies or the U.S. Government. Traditional Commerce (billion $) Electronic"
"This article addresses the performance of distributed database systems. Specifically, we present an algorithm for dynamic replication of an object in distributed systems. The algorithm is adaptive in the sence that it changes the replication scheme of the object i.e., the set of processors at which the object inreplicated) as changes occur in the read-write patern of the object (i.e., the number of reads and writes issued by each processor). The algorithm continuously moves the replication scheme towards an optimal one. We show that the algorithm can be combined with the concurrency control and recovery mechanisms of ta distributed database management system. The performance of the algorithm is analyzed theoretically and experimentally. On the way we provide a lower bound on the performance of any dynamic replication algorith."
"An important feature of many advanced active database prototypes is support for rules triggered by complex patterns of events. Their composite event languages provide powerful primitives for event-based temporal reasoning. In fact, with one important exception, their expressive power matches and surpasses that of sophisticated languages offered by Time Series Management Systems (TSMS), which have been extensively used for temporal data analysis and knowledge discovery. This exception pertains to temporal aggregation, for which, current active database systems offer only minimal support, if any."
"This paper introduces the Generalized Search Tree (GiST), an index structure supporting an extensible set of queries and data types. The GiST allows new data types to be indexed in a manner supporting queries natural to the types; this is in contrast to previous work on tree extensibility which only supported the traditional set of equality and range predicates. In a single data structure, the GiST provides all the basic search tree logic required by a database system, thereby unifying disparate structures such as B+-trees and R-trees in a single piece of code, and opening the application of search trees to general extensibility. To illustrate the flexibility of the GiST, we provide simple method implementations that allow it to behave like a B+-tree, an R-tree, and an RD-tree, a new index for data with set-valued attributes. We also present a preliminary performance analysis of RD-trees, which leads to discussion on the nature of tree indices and how they behave for various datasets."
"Editor's note: For this issue's ""From the Editors,"" I invited Robert Gephart of the University of Al-berta to reflect on his observations as a long-serving , award-winning reviewer of qualitative research for A!vII Over the past two and a half years, I have developed a tremendous respect for Bob's keen eye for evaluating qualitative research submissions , and great admiration for the painstaking advice he provides authors about how to improve their work. As a world-renowned qualitative author himself, Bob is in an excellent position to provide observations about how authors might increase the chances of having their qualitative research accepted for publication at AMI In a three-way electronic mail conversation about the challenges and opportunities of qualitative research , Bob, Tom Lee, and I all concluded that many authors with potentially very interesting data sets don't seem to know how to analyze them to their full potential. This is perhaps not surprising, gi ven the clear predominance of quantitative methods and statistics courses over qualitative ones, particularly in North America, as well as the inherently greater subjectivity involved in designing and analyzing qualitative research. As such, we encouraged Bob to provide a bit of a minitutorial-complete with reference citations and examples of high-quality papers that use particular qualitative approaches-in addition to his observations about qualitative research submitted to AMI The result is a longer-than-usual ""From the Edi-tors"" column. but one that we believe is well worth the extra reading time for anyone interested in producing , reviewing, or attempting to coax greater insights from qualitative research. We are fortunate to have someone with Bob's expertise share his observations, and we hope that his thoughts will prove useful to researchers for many years to come. Sara Rynes Incoming Editor I am thankful to Sara for inviting me to write this editorial column encouraging scholars to submit their qualitative research to the Academy of Man-I wish to thank Torn Lee and Sara Rynes for their helpful comments and encouragement in preparing this editorial. 454 agement Journal. Qualitative research is important to AMI Qualitative research is actively sought and supported by the Journal, its editors, and its editorial review board. Alv1Jhas published many qualitative papers. The coveted A/'v1jBest Article Award has been won by three qualitative papers-Gersick (1989), Isabella (1990), and Dutton and Duckerich (1991)-and by one paper that combined qualitative and quantitative methods: Sutton and Rafuclli, (1988). Despite these successes, most ¡­"
"Availability requirements for database systems are more stringent than ever before with the widespread use of databases as the foundation for ebusiness. This paper highlights Fast-Start? Fault Recovery, an important availability feature in Oracle, designed to expedite recovery from unplanned outages. Fast-Start allows the administrator to configure a running system to impose predictable bounds on the time required for crash recovery. For instance, fast-start allows fine-grained control over the duration of the roll-forward phase of crash recovery by adaptively varying the rate of checkpointing with minimal impact on online performance. Persistent transaction locking in Oracle allows normal online processing to be resumed while the rollback phase of recovery is still in progress, and fast-start allows quick and transparent rollback of changes made by uncommitted transactions prior to a crash."
"CoDecide is an experimental user interface toolkit that offers an extension to spreadsheet concepts specifically geared towards support for cooperative analysis of the kinds of multi-dimensional data encountered in data warehousing. It is distinguished from previous proposals by direct support for drill-down/roll-up analysis without redesign of an interface; more importantly, CoDecide can link multiple views on a data cube for synchronous or asynchronoous cooperation by multiple analysts, through a conceptual model visualizing the problem dimensions on so-called tapes. Tapes generalize the ideas of ranging and pivoting in current data warehouses for the multi-perspective and multi-user case. CoDecide allows the rapid composition of multi-matrix interfaces and their linkage to underlying data sources. A LAN version of CoDecide has been used in a number of design decision support applications. A WWW version representing externally materialized views on databases is currently under development."
We introduce a logical formalism for the specification of the dynamic behavior of databases. The evolution of databases is characterized by both the dynamic integrity constraints which describe the properties of state transitions and the transactions whose executions lead to state transitions. Our formalism is based on a variant of first-order situational logic in which the states of computations are explicit objects. Integrity constraints and transactions are uniformly specifiable as expressions in our language. We also point out the application of the formalism to the verification and synthesis of transactions.
"As parallel computing has become increasingly common, the need for scalable and efficient ways of storing and locating data has become increasingly acute. For years, both grid and cloud computing have distributed data across machines and even clusters at different geographic locations (sites). However not all sites need all of the data in a particular data set, or have the (perhaps specialized) processing capabilities required. These facts challenge the conventional wisdom that we should always move the computation to the data rather than the data to the computation. Sometimes the data actually required is small. In other cases, the site with specialized processing capabilities (such as a GPU equipped cluster) cannot handle the demands placed on it unless a way is found to let that cluster select the data that is actually needed, even if it is not stored locally. Our system finds partial spatial replicas that intersect with a region of interest.The work is intended to be a key component of a distributed spatial data system.Address the unique problems of accessing subsets of very large spatial datasets.Store R-tree in a relational database and investigate its design and performance.R-tree prefetching, query aggregation and use of a Morton curve in the R-tree."
"To enable modern data intensive applications including data warehousing, global information systems and electronic commerce, we must solve the schema mapping problem in which a source (legacy) database is mapped into a different, but fixed, target schema"
"Solid state disks (SSDs) provide much faster random access to data compared to conventional hard disk drives. Therefore, the response time of a database engine could be improved by moving the objects that are frequently accessed in a random fashion to the SSD. Considering the price and limited storage capacity of solid state disks, the database administrator needs to determine which objects (tables, indexes, materialized views, etc.), if placed on the SSD, would most improve the performance of the system. In this paper we propose a tool called ""Object Placement Advisor"" for making a wise decision for the object placement problem. By collecting profile inputs from workload runs, the advisor utility provides a list of objects to be placed on the SSD by applying heuristics like the greedy knapsack technique or dynamic programming. To show that the proposed approach is effective in conventional database management systems, we have conducted experiments on IBM DB2 with queries and schemas based on the TPC-H and TPC-C benchmarks. The results indicate that using a relatively small amount of SSD storage, the response time of the system can be reduced significantly by considering the recommendation of the advisor."
"During 2001, the Enterprise Engineering Laboratory at George Mason University was contracted by the Boeing Company to develop an eHub capability for aerospace suppliers in Taiwan. In a laboratory environment, the core technology was designed, developed, and tested, and now a large first-tier aerospace supplier in Taiwan is commercializing the technology. The project objective was to provide layered network and application services for transporting XML-based business transaction flows across multi-tier, heterogeneous data processing environments. This paper documents the business scenario, the eHub application, and the network transport mechanisms that were used to build the n-tier hub. Contrary to most eHubs, this solution takes the point of view of suppliers, pushing data in accordance with supplier requirements; hence, enhancing the probability of supplier adoption. The unique contribution of this project is the development of an eHub that meets the needs of Small and Medium Enterprises (SMEs) and first-tier suppliers."
"Most databases contain ¡°name constants¡± like course numbers, personal names, and place names that correspond to entities in the real world. Previous work in integration of heterogeneous databases has assumed that local name constants can be mapped into an appropriate global domain by normalization. However, in many cases, this assumption does not hold; determining if two name constants should be considered identical can require detailed knowledge of the world, the purpose of the user's query, or both. In this paper, we reject the assumption that global domains can be easily constructed, and assume instead that the names are given in natural language text. We then propose a logic called WHIRL which reasons explicitly about the similarity of local names, as measured using the vector-space model commonly adopted in statistical information retrieval. We describe an efficient implementation of WHIRL and evaluate it experimentally on data extracted from the World Wide Web. We show that WHIRL is much faster than naive inference methods, even for short queries. We also show that inferences made by WHIRL are surprisingly accurate, equaling the accuracy of hand-coded normalization routines on one benchmark problem, and outperforming exact matching with a plausible global domain on a second."
"In large data recording and warehousing environments, it is often advantageous to provide fast, approximate answers to queries, whenever possible. Before DBMSs providing highly-accurate approximate answers can become a reality, many new techniques for summarizing data and for estimating answers from summarized data must be developed. This paper introduces two new sampling-based summary statistics, concise samples and counting samples, and presents new techniques for their fast incremental maintenance regardless of the data distribution. We quantify their advantages over standard sample views in terms of the number of additional sample points for the same view size, and hence in providing more accurate query answers. Finally, we consider their application to providing fast approximate answers to hot list queries. Our algorithms maintain their accuracy in the presence of ongoing insertions to the data warehouse."
"The construction of high-performance database systems that combine the best aspects of the relational and object-oriented approaches requires the design of client-server architectures that can fully exploit client and server resources in a flexible manner. The two predominant paradigms for client-server query execution are data-shipping and query-shipping We first define these policies in terms of the restrictions they place on operator site selection during query optimization. We then investigate the performance tradeoffs between them for bulk query processing. While each strategy has advantages, neither one on its own is efficient across a wide range of circumstances. We describe and evaluate a more flexible policy called hybrid-shipping, which can execute queries at clients, servers, or any combination of the two. Hybrid-shipping is shown to at least match the best of the two ""pure"" policies, and in some situations, to perform better than both. The implementation of hybrid-shipping raises a number of difficult problems for query optimization. We describe an initial investigation into the use of a 2-step query optimization strategy as a way of addressing these issues."
"We study the problem of selective dissemination of information in P2P networks. We present our work on data models and laiguages for textual information dissemination and discuss a relemnt P2P architecture that motivates our efforts. We also survey our results on the computational complexity of three related algorithmic problems (query satisfiability, entailment and filtering) and present efficient algorithms for the most crucial of these problems (filtering). Finally, we discuss the features of P2P-DIET, a super-peer system we have implemented at the Technical Lniversity of Crete, that realizes our vision and is able to support both ad-hoc querying and selective information dissemination scenarios in a P2P framework."
"In this paper, we introduce self-tuning histograms. Although similar in structure to traditional histograms, these histograms infer data distributions not by examining the data or a sample thereof, but by using feedback from the query execution engine about the actual selectivity of range selection operators to progressively refine the histogram. Since the cost of building and maintaining self-tuning histograms is independent of the data size, self-tuning histograms provide a remarkably inexpensive way to construct histograms for large data sets with little up-front costs. Self-tuning histograms are particularly attractive as an alternative to multi-dimensional traditional histograms that capture dependencies between attributes but are prohibitively expensive to build and maintain. In this paper, we describe the techniques for initializing and refining self-tuning histograms. Our experimental results show that self-tuning histograms provide a low-cost alternative to traditional multi-dimensional histograms with little loss of accuracy for data distributions with low to moderate skew."
"Lore (for Lightweight Object Repository) is a DBMS designed specifically for managing semistructured information. Implementing Lore has required rethinking all aspects of a DBMS, including storage management, indexing, query processing and optimization, and user interfaces. This paper provides an overview of these aspects of the Lore system, as well as other novel features such as dynamic structural summaries and seamless access to data from external sources."
"Much of the data that we encounter has a spatial (geographic locational) aspect yet this has not been readily exploited by traditional RDBMS. Over the past five years there has been a confluence of Geographic Information System (GIS) technology, RDBMS architecture and SQL standards that has fostered the implementation of spatial processing within the RDBMS. This paper will present a brief overview of spatial processing and the evolution of technology leading to the development of the IBM DB2 Spatial Extender that exploits the IBM DB2 Universal Database (UDB) object-relational support to implement a standards-based SQL spatial capability."
"In the current climate change context, it is important to anticipate possible changes in the occurrence of the most severe events to adapt energy system planning and management. However, because such events are rare, any estimation of their frequency is uncertain and a large data sample is required to reduce any sampling uncertainty. In this paper, we present a way of combining past observations and climate model simulations to generate very large samples for a period extending from the recent past to the near future. It is based on the decomposition of the temperature signal into deterministic parts (smooth trends and seasonality in the mean and the standard deviation) and stochastic residuals. Once the observed signal is decomposed for a long enough time period (at least 30 years), new time series can be built using bias adjusted climate simulation trends, observed seasonality and simulated stochastic residuals. "
"A Query by Humming system allows the user to find a song by humming part of the tune. No musical training is needed. Previous query by humming systems have not provided satisfactory results for various reasons. Some systems have low retrieval precision because they rely on melodic contour information from the hum tune, which in turn relies on the error-prone note segmentation process. Some systems yield better precision when matching the melody directly from audio, but they are slow because of their extensive use of Dynamic Time Warping (DTW). Our approach improves both the retrieval precision and speed compared to previous approaches. We treat music as a time series and exploit and improve well-developed techniques from time series databases to index the music for fast similarity queries. We improve on existing DTW indexes technique by introducing the concept of envelope transforms, which gives a general guideline for extending existing dimensionality reduction methods to DTW indexes. The net result is high scalability. We confirm our claims through extensive experiments."
"ATLAS will be one of the four detectors for the LHC (Large Hadron Collider) particle accelerator currently being built at CERN, Geneva. The project is expected to start production in 2006 and during its lifetime (15-20 years) to generate roughly one petabyte per year of particle physics' data. This vast amount of information will require several meta-data repositories which will ease the manipulation and understanding of physics' data by the final users (physicists doing analysis). Metadata repositories and tools at ATLAS may address such problems as the logical organization of the physics data according to data taking sessions, errors and faults during data gathering, data quality or terciary storage meta-information.    The OBK (Online Book-Keeper) is a component of ATLAS' Online Software - the system which provides configuration, control and monitoring services to the DAQ (Data AQquisition system). In this paper we will explain the role of the OBK as one of the main collectors and managers of meta-data produced online, how that data is stored and the interfaces that are provided to access it - merging the physics data with the collected metadata will play an essential role for future analysis and interpretion of the physics events observed at ATLAS. We also provide an historical background to the OBK by analysing the several prototypes implemented in the context of our software development process and the results and experience obtained with the various DBMS technologies used."
"We discuss data mining based on association rules for two numeric attributes and one Boolean attribute. For example, in a database of bank customers, ""Age"" and ""Balance"" are two numeric attributes, and ""CardLoan"" is a Boolean attribute. Taking the pair (Age, Balance) as a point in two-dimensional space, we consider an association rule of the form((Age, Balance) &isin; P) &rArr; (CardLoan = Yes),which implies that bank customers whose ages and balances fall in a planar region P tend to use card loan with a high probability. We consider two classes of regions, rectangles and admissible (i.e. connected and x-monotone) regions. For each class, we propose efficient algorithms for computing the regions that give optimal association rules for gain, support, and confidence, respectively. We have implemented the algorithms for admissible regions, and constructed a system for visualizing the rules."
"Concurrency control has received considerable attention in multidatabase systems because of their characteristics such as heterogeneity and autonomy. Particulary, various concurrency control protocols have been developped in the litterature. In this paper, we present a protocol that guarantees the two level serializability criterion and built up according to the topdown approach."
"With the advent of XML as a format for data ex-change and semistructured databases, query languagesfor XML and semistructured data have become in-creasingly popular.Many such query languages, like XPath andXQuery, are navigational in the sense that their vari-able binding paradigm requires the programmer tospecify path navigations through the document (ordata item). In contrast, some other languages ¨C suchas UnQL [1] and Xcerpt [2] ¨C are pattern-based: theirvariable binding paradigm is that of mathematical log-ics, i.e. the programmer speci?es patterns (or terms)including variables. Arguably, a pattern-based vari-able binding paradigm makes complex queries mucheasier to specify and to read, thus improving theprogramming e?ciency. Sustaining this ?rst claimwith practical examples is one of the objectives of thepresent demonstration.Xcerpt [2] is an experimental pattern-based queryand transformation language for XML and semistruc-tured data. Xcerpt uses patterns both for bindingvariables in query expressions and for reassembling thevariables (bound to data items in query expressions) inso-called construct terms. Arguably, a pattern-baseddocument construction combined with a pattern-basedvariable binding results in a rather intuitive, userfriendly, and programming e?cient language. Sustain-ing this second claim is another objective of the presentdemonstration.Xcerpt is experimental in the sense that its purposeis to investigate and test another, non-navigational ap-proach to retrieve data from the Web than that ofthe widespread query languages XPath and XQuery.Nonetheless, Xcerpt has been prototypically imple-"
"There is already a sizable body of proposals on OODB query optimization. One of the most challenging problems in this area is query unnesting, where the embedded query can take any form, including aggregation and universal quantification. Although there is already a number of proposed techniques for query unnesting, most of these techniques are applicable to only few cases. We believe that the lack of a general and simple solution to the query unnesting problem is due to the lack of a uniform algebra that treats all operations (including aggregation and quantification) in the same way."
"Bulk loading refers to the process of creating an index from scratch for a given data set. This problem is well understood for B-trees, but so far, non-traditional index structures received modest attention. We are particularly interested in fast generic bulk loading techniques whose implementations only employ a small interface that is satisfied by a broad class of index structures. Generic techniques are very attractive to extensible database systems since different user-implemented index structures implementing that small interface can be bulk-loaded without any modification of the generic code. The main contribution of the paper is the proposal of two new generic and conceptually simple bulk loading algorithms. These algorithms recursively partition the input by using a main-memory index of the same type as the target index to be build. In contrast to previous generic bulk loading algorithms, the implementation of our new algorithms turns out to be much easier. Another advantage is that our new algorithms possess fewer parameters whose settings have to be taken into consideration. An experimental performance comparison is presented where different bulk loading algorithms are investigated in a system-like scenario. Our experiments are unique in the sense that we examine the same code for different index structures (R-tree and Slim-tree). The results consistently indicate that our new algorithms outperform asymptotically worst-case optimal competitors. Moreover, the search quality of the target index will be better when our new bulk loading algorithms are used."
"Emerging applications in the field of biotechnology hold great promise for promoting the health and well-being of the global community, especially in developing states. Yet significant concerns have emerged about biotechnology in the transnational sphere, concerns that no doubt will increase in decades to come. The purpose of the article is to assess the strengths and limits of existing international norms and structures designed to address these concerns, and to suggest a means for augmenting current structures to make them more effective. International law develops and regulates transnational behavior in a manner that goes well beyond the development treaty regimes. International law is driven in large part by the self-interest of states, but they also arise from the social interaction of states and non-state actors, and they ultimately must become grounded in national laws and society in order to become effective. This article accordingly emphasizes the need for coordination at different levels of state and non-state behavior as the law develops over time as well as the need for coordination across different treaty regimes. "
"A fruitful direction for future data mining research will be the development of techniques that incorporate privacy concerns. Specifically, we address the following question. Since the primary task in data mining is the development of models about aggregated data, can we develop accurate models without access to precise information in individual data records? We consider the concrete case of building a decision-tree classifier from training data in which the values of individual records have been perturbed. The resulting data records look very different from the original records and the distribution of data values is also very different from the original distribution. While it is not possible to accurately estimate original values in individual data records, we propose a novel reconstruction procedure to accurately estimate the distribution of original data values. By using these reconstructed distributions, we are able to build classifiers whose accuracy is comparable to the accuracy of classifiers built with the original data."
"Many applications employ sensors for monitoring entities such as temperature and wind speed. A centralized database tracks these entities to enable query processing. Due to continuous changes in these values and limited resources (e.g., network bandwidth and battery power), it is often infeasible to store the exact values at all times. A similar situation exists for moving object environments that track the constantly changing locations of objects. In this environment, it is possible for database queries to produce incorrect or invalid results based upon old data. However, if the degree of error (or uncertainty) between the actual value and the database value is controlled, one can place more confidence in the answers to queries. More generally, query answers can be augmented with probabilistic estimates of the validity of the answers. In this paper we study probabilistic query evaluation based upon uncertain data. A classification of queries is made based upon the nature of the result set. For each class, we develop algorithms for computing probabilistic answers. We address the important issue of measuring the quality of the answers to these queries, and provide algorithms for efficiently pulling data from relevant sensors or moving objects in order to improve the quality of the executing queries. Extensive experiments are performed to examine the effectiveness of several data update policies."
"Sensors are often employed to monitor continuously changing entities like locations of moving objects and temperature. The sensor readings are reported to a centralized database system, and are subsequently used to answer queries. Due to continuous changes in these values and limited resources (e.g., network bandwidth and battery power), the database may not be able to keep track of the actual values of the entities, and use the old values instead. Queries that use these old values may produce incorrect answers. However, if the degree of uncertainty between the actual data value and the database value is limited, one can place more confidence in the answers to the queries. In this paper, we present a frame-work that represents uncertainty of sensor data. Depending on the amount of uncertainty information given to the application, different levels of imprecision are presented in a query answer. We examine the situations when answer imprecision can be represented qualitatively and quantitatively. We propose a new kind of probabilistic queries called Probabilistic Threshold Query, which requires answers to have probabilities larger than a certain threshold value. We also study techniques for evaluating queries under different details of uncertainty, and investigate the tradeoff between data uncertainty, answer accuracy and computation costs."
"Recent technological advances have made multimedia on-demand servers feasible. Two challenging tasks in such systems are: a) satisfying the real-time requirement for continuous delivery of objects at specified bandwidths and b) efficiently servicing multiple clients simultaneously. To accomplish these tasks and realize economies of scale associated with servicing a large user population, the multimedia server can require a large disk subsystem. Although a single disk is fairly reliable, a large disk farm can have an unacceptably high probability of disk failure. Further, due to the real-time constraint, the reliability and availability requirements of multimedia systems are very stringent. In this paper we investigate techniques for providing a high degree of reliability and availability, at low disk storage, bandwidth, and memory costs for on-demand multimedia servers."
"It is a cliche that the Internet has revolutionized many aspects of life in the past decade. Scientific publishing is but one of the many enterprises that have been impacted by the connectivity and high bandwidth afforded by the World Wide Web. Most scientific journals now have a web presence. That said, it is still remarkable the degree to which ACM in general and TODS in particular have embraced the unique capabilities of the web to aid in the propagation of knowledge. Here I summarize the disparate and broad ways in which TODS utilizes the web, in all phases of publishing."
"For as long as there have been DBMS's and applications that use them, there has been interest in the performance characteristics that these systems exhibit. This month's column describes some of the recent work that has taken place in TPC, the Transaction Processing Performance Council.TPC-A and TPC-B are obsolete benchmarks that you might have heard about in the past. TPC-C V3.5 is the current benchmark for OLTP systems. Introduced in 1992, it has been run on many hardware platforms and DBMS's. Indeed, the TPC web site currently lists 202 TPC-C benchmark results. Due to its maturity, TPC-C will not be discussed in this article.We've asked two very knowledgeable individuals to write this article. Meikel Poess is the chair of the TPC H and TPC-R Subcommittees and Chris Floyd is the chair of the TPC-W Subcommittee. We greatly appreciate their efforts.A wealth of information can be found at the TPC web site [ 1 ]. This information includes the benchmark specifications themselves, TPC membership information, and benchmark results."
"Sensor networks are typically unattended because of their deployment in hazardous, hostile or remote environments. This makes the problem of conserving energy at individual sensor nodes challenging. S-MAC and PAMAS are two MAC protocols which periodically put nodes (selected at random) to sleep in order to achieve energy savings. Unlike these protocols, we propose an approach in which node duty cycles (i.e sleep and wake schedules) are based on their criticality. A distributed algorithm is used to find sets of winners and losers, who are then assigned appropriate slots in our TDMA based MAC protocol. We introduce the concept of of energy-criticality of a sensor node as a function of energies and traffic rates. Our protocol makes more critical nodes sleep longer, thereby balancing the energy consumption. Simulation results show that the performance of the protocol with increase in traffic load is better than existing protocols with increase in traffic load is better than existing protocols, thereby illustrating the energy balancing nature of the approach."
"We consider the problem of processing top-N queries in a distributed environment with possibly uncooperative local database systems. For a given top-N query, the problem is to find the N tuples that satisfy the query the best but not necessarily completely in an efficient manner. Top-N queries are gaining popularity in relational databases and are expected to be very useful for e-commerce applications. Many companies provide the same type of goods and services to the public on the Web, and relational databases may be employed to manage the data. It is not feasible for a user to query a large number of databases. It is therefore desirable to provide a facility where a user query is accepted at some site, suitable tuples from appropriate sites are retrieved and the results are merged and then presented to the user. In this paper, we present a method for constructing the desired facility. Our method consists of two steps. The first step determines which databases are likely to contain the desired tuples for a given query so that the databases can be ranked based on their desirability with respect to the query. Four different techniques are introduced for this step with one requiring no cooperation from local systems. The second step determines how the ranked databases should be searched and what tuples from the searched databases should be returned. A new algorithm is proposed for this purpose. Experimental results are presented to compare different methods and very promising results are obtained using the method that requires no cooperation from local databases."
"In spite of the many decades of progress in database research, surprisingly scientists in the life sciences community still struggle with inefficient and awkward tools for querying biological data sets. This work highlights a specific problem involving searching large volumes of protein data sets based on their secondary structure. In this paper we define an intuitive query language that can be used to express queries on secondary structure and develop several algorithms for evaluating these queries. We implement these algorithms both in Periscope, a native system that we have built, and in a commercial ORDBMS. We show that the choice of algorithms can have a significant impact on query performance. As part of the Periscope implementation we have also developed a framework for optimizing these queries and for accurately estimating the costs of the various query evaluation plans. Our performance studies show that the proposed techniques are very efficient in the Periscope system and can provide scientists with interactive secondary structure querying options even on large protein data sets."
"P2P computing has become an extremely popular topic in computer science. It affects diverse areas such as networking, distributed systems, information systems, algorithms and databases. The P2P paradigm introduces an architectural principle ¡°replacing¡± the paradigm of client-server computing. It is based on the concepts of decentralization and resource sharing. By avoiding central bottlenecks and distributing workload it facilitates the deployment of applications at a global scale. The use of the P2P paradigm as a practical"
"A crucial consideration in environments where data is broadcast to clients is the low bandwidth available for clients to communicate with servers. Advanced applications in such environments do need to read data that is mutually consistent as well as current. However, given the asymmetric communication capabilities and the needs of clients in mobile environments, traditional serializability-based approaches are too restrictive, unnecessary, and impractical. We thus propose the use of a weaker correctness criterion called update consistency and outline mechanisms based on this criterion that ensure (1) the mutual consistency of data maintained by the server and read by clients, and (2) the currency of data read by clients. Using these mechanisms, clients can obtain data that is current and mutually consistent ¡°off the air¡±, i.e., without contacting the server to, say, obtain locks. Experimental results show a substantial reduction in response times as compared to existing (serializability-based) approaches. A further attractive feature of the approach is that if caching is possible at a client, weaker forms of currency can be obtained while still satisfying the mutual consistency of data."
"We introduce the problem of mining generalized association rules. Given a large database of transactions, where each transaction consists of a set of items, and a taxonomy (is-a hierarchy) on the items, we find associations between items at any level of the taxonomy. For example, given a taxonomy that says that jackets is-a outerwear is-e clothes, we may infer a rule that ¡°people who buy outerwear tend to buy shoes¡±. This rule may hold even if rules that ¡°people who buy jackets tend to buy shoes¡±, and ¡°people who buy clothes tend to buy shoes¡± do not hold. An obvious solution to the problem is to add all ancestors of each item in a transaction to the transaction, and then run any of the algorithms for mining association rules on these ¡°extended transactions¡± . However, this ¡°Basic¡± algorithm is not very fast; we present two algorithms, Cumulate and EstMerge, which run 2 to 5 times faster than Basic (and more than 100 times faster on one real-life dataset). We also present a new interest-measure for rules which uses the information in the taxonomy. Given a user-specified ¡°minimum-interest-level¡±, this measure prunes a large number of redundant rules; 40% to 60% of all the rules were pruned on two real-life datasets. "
"The rapidly expanding technology of mobile computers, wireless data networks, vehicle navigation, multimedia and database systems has caused the development of powerful mobile information systems. These systems, consisting of a portable computer (Laptop, PDA), have large storage capacities, capabilities of wireless connection to a worldwide information network and provide to their users many functionalities like access to WWW, shopping, banking, reservations and other transactions."
"Mobile Ad-hoc Networks (MANET) is an emerging area of research. Most current work is centered on routing issues. This paper discusses the issues associated with data communication with MANET database systems. While data push and data pull methods have been previously addressed in mobile networks, the proposed methods do not handle the unique requirements associated with MANET. Unlike traditional mobile networks, all nodes within the MANET are mobile and battery powered. Existing wireless algorithms and protocols are insufficient primarily because they do not consider the mobility and power requirements of both clients and servers. This paper will present some of the critical tasks facing this research."
"We consider the problem of mapping data in peer-to-peer data-sharing systems. Such systems often rely on the use of mapping tables listing pairs of corresponding values to search for data residing in different peers. In this paper, we address semantic and algorithmic issues related to the use of mapping tables. We begin by arguing why mapping tables are appropriate for data mapping in a peer-to-peer environment. We discuss alternative semantics for these tables and we present a language that allows the user to specify mapping tables under different semantics. Then, we show that by treating mapping tables as constraints (called mapping constraints) on the exchange of information between peers it is possible to reason about them. We motivate why reasoning capabilities are needed to manage mapping tables and show the importance of inferring new mapping tables from existing ones. We study the complexity of this problem and we propose an efficient algorithm for its solution. Finally, we present an implementation along with experimental results that show that mapping tables may be managed efficiently in practice."
We provide a concise yet complete formal definition of the semantics of XPath 1 and summarize e cient algorithms for processing queries in this language. Our presentation is intended both for the reader who is looking for a short but comprehensive formal account of XPath as well as the software developer in need of material that facilitates the rapid implementation of XPath engines.
"In this paper we propose an approach that enables mobile clients to determine the validity of previous queries based on their current locations. In order to make this possible, the server returns in addition to the query result, a validity region around the client's location within which the result remains the same. We focus on two of the most common spatial query types, namely nearest neighbor and window queries, define the validity region in each case and propose the corresponding query processing algorithms. In addition, we provide analytical models for estimating the expected size of the validity region. Our techniques can significantly reduce the number of queries issued to the server, while introducing minimal computational and network overhead compared to traditional spatial queries."
"Building a data-intensive web site is a complex task. Ad hoc rapid prototyping approaches easily lead to unsatisfactory results, e.g. poor maintainability and extensibility. To address this problem, a number of model-based approaches have been proposed, which attempt to simplify the design and development of data-intensive web sites. However, these approaches typically lack expressive meta-models and, as a result, suffer from a number of limitations, e.g. the lack of appropriate support for the creation of complex user interfaces, for the specification of layouts and presentation styles, and for customization. In this paper we describe a new software tool OntoWeaver, which uses ontologies to drive the design and development of data-intensive web sites. "
"Attributes of a relation are not typically independent. Multidimensional histograms can be an effective tool for accurate multiattribute query selectivity estimation. In this paper, we introduce STHoles, a ¡°workload-aware¡± histogram that allows bucket nesting to capture data regions with reasonably uniform tuple density. STHoles histograms are built without examining the data sets, but rather by just analyzing query results. Buckets are allocated where needed the most as indicated by the workload, which leads to accurate query selectivity estimations. Our extensive experiments demonstrate that STHoles histograms consistently produce good selectivity estimates across synthetic and real-world data sets and across query workloads, and, in many cases, outperform the best multidimensional histogram techniques that require access to and processing of the full data sets during histogram construction."
"Rapid growth in the volume of documents, their diversity, and terminological variations render federated digital libraries increasingly difficult to manage. Suitable abstraction mechanisms are required to construct meaningful and scalable document clusters, forming a cross-digital library information space for browsing and semantic searching. This paper addresses the above issues, proposes a distributed semantic framework that achieves a logical partitioning of the information space according to topic areas, and provides facilities to contextualize and landscape the available document sets in subject-specific categories."
"The view selection problem is to choose a set of views to materialize over a database schema, such that the cost of evaluating a set of workload queries is minimized and such that the views fit into a prespecified storage constraint. The two main applications of the view selection problem are materializing views in a database to speed up query processing, and selecting views to materialize in a data warehouse to answer decision support queries. In addition, view selection is a core problem for intelligent data placement over a wide-area network for data integration applications and data management for ubiquitous computing. We describe several fundamental results concerning the view selection problem. We consider the problem for views and workloads that consist of equality-selection, project and join queries, and show that the complexity of the problem depends crucially on the quality of the estimates that a query optimizer has on the size of the views it is considering to materialize. When a query optimizer has good estimates of the sizes of the views, we show a somewhat surprising result, namely, that an optimal choice of views may involve a number of views that is exponential in the size of the database schema. On the other hand, when an optimizer uses standard estimation heuristics, we show that the number of necessary views and the expression size of each view are polynomially bounded."
"Workflow management systems are among the most interesting concepts for supporting modern organizations with a focus on processes rather than on structure. Workflow management systems offer different degrees of automation of business processes. We classify workflow management systems according to the features they provide and the types of processes they support. Database systems facilitate the realization of workflow management systems in several ways. They can provide the necessary functionality to keep the workflow relevant data, business data as well as process data. The dynamic execution of workflows can be handled by triggers of active database systems. Furthermore, the transaction concept can be extended to develop workflow transactions for consistent execution of workflows and intelligent treatment of exceptions and errors."
"Semantic integration is an active area of research in several disciplines, such as databases, information-integration, and ontologies. This paper provides a brief survey of the approaches to semantic integration developed by researchers in the ontology community. We focus on the approaches that differentiate the ontology research from other related areas. The goal of the paper is to provide a reader who may not be very familiar with ontology research with introduction to major themes in this research and with pointers to different research projects. We discuss techniques for finding correspondences between ontologies, declarative ways of representing these correspondences, and use of these correspondences in various semantic-integration tasks"
"Partitioning a data cube into sets of cells with ""similar behavior"" often better exposes the semantics in the cube. E.g., if we find that average boots sales in the West 10th store of Walmart was the same for winter as for the whole year, it signifies something interesting about the trend of boots sales in that location in that year. In this paper, we are interested in finding succinct summaries of the data cube, exploiting regularities present in the cube, with a clear basis. We would like the summary: (i) to be as concise as possible, (ii) to itself form a lattice preserving the rollup/drilldown semantics of the cube, and (iii) to allow the original cube to be fully recovered. We illustrate the utility of solving this problem and discuss the inherent challenges. We develop techniques for partitioning cube cells for obtaining succinct summaries, and introduce the quotient cube. We give efficient algorithms for computing it from a base table. For monotone aggregate functions (e.g., COUNT, MIN, MAX, SUM on non-negative measures, etc.), our solution is optimal (i.e., quotient cube of the least size). For nonmonotone functions (e.g., AVG), we obtain a locally optimal solution. We experimentally demonstrate the efficacy of our ideas and techniques and the scalability of our algorithms."
"High dimensional data has always been a challenge for clustering algorithms because of the inherent sparsity of the points. Recent research results indicate that in high dimensional data, even the concept of proximity or clustering may not be meaningful. We discuss very general techniques for projected clustering which are able to construct clusters in arbitrarily aligned subspaces of lower dimensionality. The subspaces are specific to the clusters themselves. This definition is substantially more general and realistic than currently available techniques which limit the method to only projections from the original set of attributes. The generalized projected clustering technique may also be viewed as a way of trying to redefine clustering for high dimensional applications by searching for hidden subspaces with clusters which are created by inter-attribute correlations. We provide a new concept of using extended cluster feature vectors in order to make the algorithm scalable for very large databases. The running time and space requirements of the algorithm are adjustable, and are likely ta tradeoff with better accuracy."
Welcome to this installment in the SIGMOD Record's series of interviews with pillars of the database community. This issue's interview with Hector Garcia-Molina took place in June 2001 (face to face) and October 2001 (email). Hector is the Leonard Bosack and Sandra
"Integrating data and knowledge from multiple heterogeneous sources -- like databases, knowledge bases or specific software packages -- is often required for answering certain queries. Recently, a powerful framework for defining mediated views spanning multiple knowledge bases by a set of constrained rules was proposed [24, 4, 16]. We investigate the materialization of these views by unfolding the view definition and the efficient maintenance of the resulting materialized mediated view in case of updates. Thereby, we consider two kinds of updates: updates to the view and updates to the underlying sources. For each of these two cases several efficient algorithms maintaining materialized mediated views are given. We improve on previous algorithms like the DRed algorithm [12] and introduce a new fixpoint operator WP which -- opposed to the standard fixpoint operator TP [9] -- allows us to correctly capture the update's semantics without any recomputation of the materialized view."
"XML parsing is generally known to have poor performance characteristics relative to transactional database processing. Yet, its potentially fatal impact on overall database performance is being underestimated. We report real-word database applications where XML parsing performance is a key obstacle to a successful XML deployment. There is a considerable share of XML database applications which are prone to fail at an early and simple road block: XML parsing. We analyze XML parsing performance and quantify the extra overhead of DTD and schema validation. Comparison with relational database performance shows that the desired response times and transaction rates over XML data can not be achieved without major improvements in XML parsing technology. Thus, we identify research topics which are most promising for XML parser performance in database systems."
"1 Introduction to SQL-92 2 Getting Started with SQL-92 3 Basic Table Creation and Data Manipulation 4 Basic Data Definition Language (DDL) 5 Values, Basic Functions, and Expressions 6 Advanced Value Expressions: CASE, CAST, and Row Value Expressions 7 Predicates 8 Working with Multiple Tables: The Relational Operators 9 Advanced SQL Query Expressions 10 Constraints, Assertions, and Referential Integrity 11 Accessing SQL from the Real World 12 Cursors 13 Privileges, Users, and Security 14 Transaction Management 15 Connections and Remote Database Access 16 DYNAMIC SQL 17 Diagnostics and Error Management 18 Internationalization Aspects of SQL-92 19 Information Schema 20 A Look to the Future A Designing SQL-92 Databases B A Complete SQL-92 Example C The SQL-92 Annexes: Differences, Implementation-Defined and Implementation-Dependent Features, Deprecated Features, and Leveling D Relevant Standards Bodies E Status Codes F The SQL Standardization Process G The Complete SQL-92 Language"
"Today¡¯s Internet economy has primed customers to expect immediate access and immediate results. But instant results are difficult to achieve when your customers want up-to-the-minute information about themselves: account balances, detailed transactional histories across all products, immediate problem resolution, and recommended advice on future purchases. Their expectation is that they will get the same interaction with your company whether they communicate with you via telephone, the web, a kiosk, or e-mail. To retain customers and make better decisions, businesses must step up the pace. Customers and systems need access to events ¨C like orders, shipments, and payments ¨C the moment they occur. They need to be able to act on events automatically, in real time. The prescription: a ¡°Zero Latency Enterprise¡±. 1. The ZLE Challenge From an IT perspective, the challenge is twofold: integrating customer and product information scattered in disparate systems throughout the enterprise, and acting on it in real time. The first challenge, integrating customer and product information scattered in disparate systems throughout the enterprise, focuses on enterprise application integration (EAI). EAI instantaneously transform decisions and information into operational changes by ¡°pushing¡± information to where it is needed. The second challenge, instant access, analysis, and reaction to information, has been addressed traditionally by using business intelligence technologies, such as data marts, data warehouses, and operational data stores (ODS). Of particular need is a data-centric ODS that is a central, operations-focused data store fed in near real time by all of the other databases in the enterprise. This ODS could provide a central repository from which users and applications ¡°pull¡± information as needed. The problems with these traditional approaches is that they don¡¯t address the challenge of minimizing the lag, or information float, between when the data is captured in one place and when it can be used somewhere else. Each approach has its limitations; most organizations require a combination of the two ¨C a real time ODS combined with EAI. "
"Finding patterns in large, real, spatio/temporal data continues to attract high interest (e.g., sales of products over space and time, patterns in mobile phone users; sensor networks collecting operational data from automobiles, or even from humans with wearable computers). In this paper, we describe an interdisciplinary research effort to couple knowledge discovery in large environmental databases with biological and chemical sensor networks, in order to revolutionize drinking water quality and security decision making. We describe a distribution and operation protocol for the placement and utilization of in situ environmental sensors by combining (1) new algorithms for spatialtemporal data mining, (2) new methods to model water quality and security dynamics, and (3) a sophisticated decision-analysis framework. The project was recently funded by NSF and represents application of these research areas to the critical current issue of ensuring safe and secure drinking water to the population of the United States."
"In many applications, users specify target values for certain attributes, without requiring exact matches to these values in return. Instead, the result to such queries is typically a rank of the ""top k"" tuples that best match the given attribute values. In this paper, we study the advantages and limitations of processing a top-k query by translating it into a single range query that a traditional relational database management system (RDBMS) can process efficiently. In particular, we study how to determine a range query to evaluate a top-k query by exploiting the statistics available to an RDBMS, and the impact of the quality of these statistics on the retrieval efficiency of the resulting scheme. We also report the first experimental evaluation of the mapping strategies over a real RDBMS, namely over Microsoft's SQL Server 7.0. The experiments show that our new techniques are robust and significantly more efficient than previously known strategies requiring at least one sequential scan of the data sets."
"One of the common queries in many database applications is finding approximate matches to a given query item from a collection of data items. For example, given an image database, one may want to retrieve all images that are similar to a given query image. Distance-based index structures are proposed for applications where the distance computations between objects of the data domain are expensive (such as high-dimensional data) and the distance function is metric. In this paper we consider using distance-based index structures for similarity queries on large metric spaces. We elaborate on the approach that uses reference points (vantage points) to partition the data space into spherical shell-like regions in a hierarchical manner. We introduce the multivantage point tree structure  (mvp-tree) that uses more than one vantage point to partiton the space into spherical cuts at each level. In answering similarity-based queries, the mvp-tree also utilizes the precomputed (at construction time) distances between the data points and the vantage points."
"Finding approximate answers to multi-dimensional range queries over real valued attributes has significant applications in data exploration and database query optimization. In this paper we consider the following problem: given a table of d attributes whose domain is the real numbers, and a query that specifies a range in each dimension, find a good approximation of the number of records in the table that satisfy the query."
"Internet based eCommerce is expected to grow at a phenomenal rate. As businesses rapidly move to deploy business-to-business eCommerce solutions, systems designers are likely to face new challenges while integrating and managing data. In this presentation, I propose to discuss some of the new business models and the impact on data management in the context of these evolving eCommerce scenarios."
"The VisDB system developed at the University of Munich is a sophisticated tool for visualizing and analyzing large databases. The key idea of the VisDB system is to support the exploration of large databases by using the phenomenal abilities of the human vision system which is able to analyze visualizations of mid-size to large amounts of data very efficiently. The goal of the VisDB system is to provide visualizations of large portions of the database, allowing properties of the data and structure in the data to become perceptually apparent."
"Many applications require the management of spatial data. Clustering large spatial databases is an important problem which tries to find the densely populated regions in the feature space to be used in data mining, knowledge discovery, or efficient information retrieval. A good clustering approach should be efficient and detect clusters of arbitrary shape. It must be insensitive to the outliers (noise) and the order of input data. We propose WaveCluster, a novel clustering approach based on wavelet transforms, which satisfies all the above requirements. Using multiresolution property of wavelet transforms, we can effectively identify arbitrary shape clusters at different degrees of accuracy. We also demonstrate that WaveCluster is highly efficient in terms of time complexity. Experimental results on very large data sets are presented which show the efficiency and effectiveness of the proposed approach compared to the other recent clustering methods. This research is supported by Xerox Corporation. "
"The Moving Picture Experts Group (MPEG) is developing a new standard called the ¡°Multimedia Content Description Interface,¡± also known as MPEG-7. The goal of MPEG-7 is to enable fast and effective searching and filtering of multimedia content. The effort is being driven by requirements taken from a large number of applications related to multimedia databases, interactive media services (music, TV programs), video libraries, and so forth. MPEG-7 is achieving this goal by developing an XML-Schema based standard for describing features of multimedia content. In this tutorial, we study the emerging MPEG-7 standard and describe the new challenges for MPEG-7 multimedia databases."
"As databases have expanded in scope from storing purely business data to include XML documents, product catalogs, e-mail messages, and directory data, it has become increasingly important to search databases based on wild-card string matching: prefix matching, for example, is more common (and useful) than exact matching, for such data. In many cases, matches need to be on multiple attributes/dimensions, with correlations between the dimensions. Traditional multi-dimensional index structures, designed with (fixed length) numeric data in mind, are not suitable for matching unbounded length string data."
"The main purpose of research on the integration of Web Technology with database systems is the delivery of Data-Intensive Web Sites, i.e., Web applications whose primary purpose is to present a large amount of content to a variety of possible users. These sites must o er a generic user the possibility to browse a large collection of data, in a way that ful lls some application-speci c goal (e.g., in electronic commerce, showing to each user exactly those goods that he will most likely purchase). Data-Intensive Web Sites are typically generated by means of tools that extract content from large data sources (e.g., catalogs of goods). One important aspect of these tools is their ability to support one-to-one Web delivery, i.e., to give each user the impression of interacting with the application by means of a dedicated interface, speci cally tailored to the user's needs and preferences. In this paper, we discuss the requirements for e ective one-to-one Web delivery, and then we show how these requirements are supported in the W3I3 1 Project. 1 Requirements for One-to-One Delivery of Data-Intensive Web Sites When a Web site is automatically generated by extracting its content from data sources, the generation process can be personalized so as to take into account the properties of each user or user group. This process is called one-to-one Web delivery and is becoming increasingly popular, especially in electronic commerce applications. Supporting one-to-one Web delivery consists of four basic aspects: The users must be associated to a pro le, i.e., a description of user-speci c properties. Although some information in the pro le is generic (e.g., the user's e-mail), some other information is instead application-speci c (e.g., related to a speci c electronic commerce context). "
"Publisher Summary The support provided by enTrans can be employed by users to realize long running activities with transaction properties¡ªwhere the activities access one or more Lightweight Directory Access Protocol (LDAP) servers. The philosophy underlying enTrans allows any standard LDAP server. It also provides for a pluggable and hence customizable integrity constraint manager. Directories were designed for data-intensive applications where reads are more frequent than writes, and they were primarily meant for the standard white and yellow page applications. LDAP is an open industry standard for accessing directory-based information. Due to its natural way of representing data in hierarchical form, efficient read access, and support for heterogeneous data, LDAP is being used for more demanding applications, such as policy enabled networks and identity and access management. While the early LDAP applications mostly involved reads, as directory applications mature, the need for updates is increasing and updates are typically spread across data repositories which store user profiles in a decentralized fashion."
"We discuss the design of an acquisitional query processor for data collection in sensor networks. Acquisitional issues are those that pertain to where, when, and how often data is physically acquired (sampled) and delivered to query processing operators. By focusing on the locations and costs of acquiring data, we are able to significantly reduce power consumption over traditional passive systems that assume the a priori existence of data. We discuss simple extensions to SQL for controlling data acquisition, and show how acquisitional issues influence query optimization, dissemination, and execution. We evaluate these issues in the context of TinyDB, a distributed query processor for smart sensor devices, and show how acquisitional techniques can provide significant reductions in power consumption on our sensor devices."
"In decision support applications, the ability to provide fast approximate answers to aggregation queries is desirable. One commonly-used technique for approximate query answering is sampling. For many aggregation queries, appropriately constructed biased (non-uniform) samples can provide more accurate approximations than a uniform sample. The optimal type of bias, however, varies from query to query. In this paper, we describe an approximate query processing technique that dynamically constructs an appropriately biased sample for each query by combining samples selected from a family of non-uniform samples that are constructed during a pre-processing phase. We show that dynamic selection of appropriate portions of previously constructed samples can provide more accurate approximate answers than static, non-adaptive usage of uniform or non-uniform samples."
"Rule-based optimizers are extensible because they consist of modifiable sets of rules. For modification to be straightforward, rules must be easily reasoned about (i.e., understood and verified). At the same time, rules must be expressive and efficient (to fire) for rule-based optimizers to be practical. Production-style rules (as in [15]) are expressed with code and are hard to reason about. Pure rewrite rules (as in [1]) lack code, but cannot atomically express complex transformations (e.g., normalizations). Some systems allow rules to be grouped, but sacrifice efficiency by providing limited control over their firing. Therefore, none of these approaches succeeds in making rules expressive, efficient and understandable."
"Cleaning data of errors in structure and content is important for data warehousing and integration. Current solutions for data cleaning involve many iterations of data ¡°auditing¡± to find errors, and long-running transformations to fix them. Users need to endure long waits, and often write complex transformation scripts. We present Potter¡¯s Wheel, an interactive data cleaning system that tightly integrates transformation and discrepancy detection. Users gradually build transformations to clean the data by adding or undoing transforms on a spreadsheet-like interface; the effect of a transform is shown at once on records visible on screen. These transforms are specified either through simple graphical operations, or by showing the desired effects on example data values. In the background, Potter¡¯s Wheel automatically infers structures for data values in terms of user-defined domains, and accordingly checks for constraint violations. Thus users can gradually build a transformation as discrepancies are found, and clean the data without writing complex programs or enduring long delays."
"Relational query processors derive much of their effectiveness from the awareness of specific table properties like sort order, size, or absence of duplicate tuples. This text applies (and adapts) this successful principle to database-supported XML and XPath processing: the relational system is made tree aware, i.e., tree properties like subtree size, intersection of paths, inclusion or disjointness of subtrees are made explicit. We propose a local change to the database kernel, the staircase join, which encapsulates the necessary tree knowledge needed to improve XPath performance. Staircase join operates on an XML encoding which makes this knowledge available at the cost of simple integer operations (e.g., +, ¡Ü ). We finally report on quite promising experiments with a staircase join enhanced main-memory database kernel."
"Given user data, one often wants to find approximate matches in a large database. A good example of such a task is finding images similar to a given image in a large collection of images. We focus on the important and technically diffcult case where each data element is high dimensional, or more generally, is represented by a point in a large metric spaceand distance calculations are computationally expensive. In this paper we introduce a data structure to solve this problem called a GNAT { Geometric Near-neighbor Access Tree. It is based on the philosophy that the data structure should act as a hierarchical geometrical model of the data as opposed to a simple decomposition of the data that does not use its intrinsic geometry. In experiments, we find that GNAT's outperform previous data structures in a number of applications. Keywords { near neighbor, metric space, approximate queries, data mining, Dirichlet domains, Voronoi regions"
"The majority of data reduction techniques for approximate query processing (such as wavelets, histograms, kernels, and so on) are not usually applicable to categorical data. There has been something of a disconnect between research in this area and the reality of data-base data; much recent research has focused on approximate query processing over ordered or numerical attributes, but arguably the majority of database attributes are categorical: country, state, job_title, color, sex, department, and so on."
"Many requests for proposals have been issued since the last issue of this column appeared six months ago. We first briefly touch upon some recent developments along the policy/legislation front concerning NSF, ARPA, and HPCC. We then recap the recent requests for proposals from ARPA, NSF, Air Force, NASA, and Army."
"In outsourced database (ODB)systems the database owner publishes its data through a number of remote servers, with the goal of enabling clients at the edge of the network to access and query the data more efficiently. As servers might be untrusted or can be compromised, query authentication becomes an essential component of ODB systems. Existing solutions for this problem concentrate mostly on static scenarios and are based on idealistic properties for certain cryptographic primitives. In this work, first we define a variety of essential and practical cost metrics associated with ODB systems. Then, we analytically evaluate a number of different approaches, in search for a solution that best leverages all metrics. Most importantly, we look at solutions that can handle dynamic scenarios, where owners periodically update the data residing at the servers. Finally, we discuss query freshness, a new dimension in data authentication that has not been explored before. A comprehensive experimental evaluation of the proposed and existing approaches is used to validate the analytical models and verify our claims. Our findings exhibit that the proposed solutions improve performance substantially over existing approaches, both for static and dynamic environments."
"TimesTen is an in-memory, application-tier data manager that delivers low response time and high throughput. Applications may create tables and manage them exclusively in TimesTen, and they may optionally cache frequently used subsets of a disk-based relational database in TimesTen. Cached tables and tables managed exclusively by TimesTen may coexist in the same database. Queries and updates to the cache are performed by the application through SQL. Applications running on different mid-tier servers may cache different or overlapping subsets of the same back-end database. TimesTen keeps the caches synchronized with each other and with the back-end database."
"Replication is a key mechanism to achieve scalability and fault-tolerance in databases. Its importance has recently been further increased because of the role it plays in achieving elasticity at the database layer. In database replication, the biggest challenge lies in the trade-off between performance and consistency. A decade ago, performance could only be achieved through lazy replication at the expense of transactional guarantees. The strong consistency of eager approaches came with a high cost in terms of reduced performance and limited scalability. Postgres-R combined results from distributed systems and databases to develop a replication solution that provided both scalability and strong consistency. The use of group communication primitives with strong ordering and delivery guarantees together with optimized transaction handling (tailored locking, transferring logs instead of re-executing updates, keeping the message overhead per transaction constant) were a drastic departure from the state-of-the-art at the time. Ten years later, these techniques are widely used in a variety of contexts but particularly in cloud computing scenarios. In this paper we review the original motivation for Postgres-R and discuss how the ideas behind the design have evolved over the years."
"After the successful first International Workshop on Engineering Federated Database Systems (EFDBS'97) in Barcelona in June 1997 [CEH+ 97], the goal of this second workshop was to bring together researchers and practitioners interested in various issues in the development of federated information systems, whereby the scope has been extended to cover database and non-database information sources (the change from EFDBS to EFIS reflects this). This report provides details of the workshop content and the conclusions reached in the final discussion"
"The MOMIS project (Mediator envirOnment for Multiple Information Sources) developed in the past years allows the integration of data from structured and semi-structured data sources. SI-Designer (Source Integrator Designer) is a designer support tool implemented within the MOMIS project for semi-automatic integration of heterogeneous sources schemata. It is a java application where all modules involved are available as CORBA Object and interact using established IDL interfaces. The goal of this demonstration is to present a new tool: SI-Web (Source Integrator on Web), it offers the same features of SI-Designer but it has got the great advantage of being usable on Internet through a web browser."
"Clustering is one of the most effective means to enhance the performance of object base applications. Consequently, many proposals exist for algorithms computing good object placements depending on the application profile. However, in an effective object base reorganization tool the clustering algorithm is only one constituent. In this paper, we report on our object base reorganization tool that covers all stages of reorganizing the objects: the application profile is determined by a monitoring tool, the object placement is computed from the monitored access statistics utilizing a variety of clustering algorithms and, finally, the reorganization tool restructures the object base accordingly. The costs as well as the effectiveness of these tools is quantitatively evaluated on the basis of the OO1-benchmark."
"Semantic Binary Object-oriented Data Model (Sem-ODM) provides an expressive data model (similar to Object-oriented Data Models) with a well-known declarative query facility - SQL (similar to relational databases). Advantages of using Sem-ODM include (i.) friendlier and more intelligent generic user interfaces; (ii.) comprehensive enforcement of integrity constraints; (iii.) greater flexibility; (iv.) substantially shorter application programs; and (v.) easier query facility. SemanticAccess is a set of tools developed to provide a semantic interface to Semantic Binary Object-oriented Databases (Sem-ODB) as well as relational databases. This presentation focuses on the system architecture of SemanticAccess including Semantic Binary Object-oriented Data Model, Semantic SQL query language, Semantic Binary Database and a wrapper developed for relational databases. 1. Purpose"
"This paper proposes an extension of the multiversion two phase locking protocol, called EMVZPL, which enables update transactions to use versions while guaranteeing the serializability of all transactions. The use of the protocol is restricted to transactions, called write-then-read transactions that consist of two consecutive parts: a write part containing both read and write operations in some arbitrary order, and an abusively called read part, containing read operations or write operations on data items already locked in the write part of the transaction. With EMVZPL, read operations in the read part use versions and read locks acquired in the write part can be released just before entering the read part. We prove the correctness of our protocol, and show that its implementation requires very few changes to classical implementations of MVZPL. After presenting various methods used by application developers to implement integrity checking, we show how EMV2PL can be effectively used to optimize the processing of update transactions that perform integrity checks. Finally, performance studies show the benefits of our protocol compared to a (strict) two phase locking protocol."
"Computing multiple related group-bys and aggregates is one of the core operations of On-Line Analytical Processing (OLAP) applications. Recently, Gray et al. [GBLP95] proposed the ¡°Cube¡± operator, which computes group-by aggregations over all possible subsets of the specified dimensions. The rapid acceptance of the importance of this operator has led to a variant of the Cube being proposed for the SQL standard. Several efficient algorithms for Relational OLAP (ROLAP) have been developed to compute the Cube. However, to our knowledge there is nothing in the literature on how to compute the Cube for Multidimensional OLAP (MOLAP) systems, which store their data in sparse arrays rather than in tables. In this paper, we present a MOLAP algorithm to compute the Cube, and compare it to a leading ROLAP algorithm. The comparison between the two is interesting, since although they are computing the same function, one is value-based (the ROLAP algorithm) whereas the other is position-based (the MOLAP algorithm). Our tests show that, given appropriate compression techniques, the MOLAP algorithm is significantly faster than the ROLAP algorithm. In fact, the difference is so pronounced that this MOLAP algorithm may be useful for ROLAP systems as well as MOLAP systems, since in many cases, instead of cubing a table directly, it is faster to first convert the table to an array, cube the array, then convert the result back to a table."
"Formulating queries on networked information systems is laden with problems: data diversity, data complexity, network growth, varied user base, and slow network access. This paper proposes a new approach to a network query user interface which consists of two phases: query preview and query refinement. This new approach is based on dynamic queries and tight coupling, guiding users to rapidly and dynamically eliminate undesired items, reduce the data volume to a manageable size, and refine queries locally before submission over a network. A two-phase dynamic query system for NASA's Earth Observing Systems--Data Information Systems (EOSDIS) is presented. The prototype was well received by the team of scientists who evaluated the interface."
"Data mining on large data warehouses is becoming increasingly important. In support of this trend, we consider a spectrum of architectural alternatives for coupling mining with database systems. These alternatives include: loose-coupling through a SQL cursor interface; encapsulation of a mining algorithm in a stored procedure; caching the data to a file system on-the-fly and mining; tight-coupling using primarily user-defined functions; and SQL implementations for processing in the DBMS. We comprehensively study the option of expressing the mining algorithm in the form of SQL queries using Association rule mining as a case in point. We consider four options in SQL-92 and six options in SQL enhanced with object-relational extensions (SQL-OR). Our evaluation of the different architectural alternatives shows that from a performance perspective, the Cache-Mine option is superior, although the performance of the SQL-OR option is within a factor of two. Both the Cache-Mine and the SQL-OR approaches incur a higher storage penalty than the loose-coupling approach which performance-wise is a factor of 3 to 4 worse than Cache-Mine. The SQL-92 implementations were too slow to qualify as a competitive option. We also compare these alternatives on the basis of qualitative factors like automatic parallelization, development ease, portability and inter-operability."
"The volume of medical imaging data produced per year is rapidly increasing, overtaxing the capabilities of Picture Archival and Communication (PACS) systems. Image compression methods can lessen the problem by encoding digital images into more space-efficient forms. Image compression is achieved by reducing redundancy in the imaging data. Existing methods reduce redundancy in individual images. However, these methods ignore an additional source of redundancy, which is based on the common information stored in more than one image in a set of similar images. We use the term ""set redundancy"" to describe this type of redundancy. Medical image databases contain large sets of similar images, therefore they also contain significant amounts of set redundancy.This paper presents two methods that extract set redundancy from medical imaging data: the Min-Max Differential (MMD), and the Min-Max Predictive (MMP) methods. These methods can improve compression of standard image compression techniques for sets of medical images. Our tests compressing CT brain scans have shown an average of as much as 129% improvement for Huffman encoding, 93% for Arithmetic Coding, and 37% for Lempel-Ziv compression when they are combined with Min-Max methods. Both MMD and MMP are based on reversible operations, hence they provide lossless compression."
"Abstract. The requirements of wide-area distributed database systems differ dramatically from those of local-area network systems. In a wide-area network (WAN) configuration, individual sites usually report to different system administrators, have different access and charging algorithms, install site-specific data type extensions, and have different constraints on servicing remote requests. Typical of the last point are production transaction environments, which are fully engaged during normal business hours, and cannot take on additional load. Finally, there may be many sites participating in a WAN distributed DBMS.  In this world, a single program performing global query optimization using a cost-based optimizer will not work well. Cost-based optimization does not respond well to site-specific type extension, access constraints, charging algorithms, and time-of-day constraints. Furthermore, traditional cost-based distributed optimizers do not scale well to a large number of possible processing sites. Since traditional distributed DBMSs have all used cost-based optimizers, they are not appropriate in a WAN environment, and a new architecture is required.  We have proposed and implemented an economic paradigm as the solution to these issues in a new distributed DBMS called Mariposa. In this paper, we present the architecture and implementation of Mariposa and discuss early feedback on its operating characteristics. "
"In this paper we describe the design and implementation of OPT++, a tool for extensible database query optimization that uses an object-oriented design to simplify the task of implementing, extendi..."
"Whenever data is moved across nodes in the parallel database system, the indexes need to be modified too. Index modification overhead can be quite severe because there can be a large number of indexes on a relation. In this paper, we study two alternatives to index modification, namely OAT (One-At-a-Time page movement) and BULK (bulk page movement). OAT and BULK are two extremes on the spectrum of the granularity of data movement. OAT and BULK differ in two respects: first, OAT uses very little additional disk space (at most one extra page), whereas BULK uses a large amount of disk space. Second, BULK uses sequential prefetch I/O to optimize on the number of I/Os during index modification, while OAT does not. Using an experimental testbed, we show that BULK is an order of magnitude faster than OAT. In terms of the impact on transaction performance during reorganization, BULK and OAT perform differently: when the number of indexes to be modified is either one or two, OAT has a lesser impact on the transaction performance degradation. However, when the number of indexes is greater than two, both techniques have the same impact on transaction performance."
"The rapid growth of structured data on the Web has created a high demand for making this content more reusable and consumable. Companies are competing not only on gathering structured content and making it public, but also on encouraging people to reuse and profit from this content. Many companies have made their content publicly accessible not only through APIs but also started to widely adopt web metadata standards such as XML, RDF, RDFa, and microformats. This trend of structured data on the Web (Data Web) is shifting the focus of Web technologies towards new paradigms of structured-data retrieval. "
"DB2 DataPropagator is one of the IBM's solutions for asynchronous replication of relational data by two separate programs Capture and Apply. The Capture program captures changes made to source data from recovery log files into staging tables, while the Apply program applies the changes from the staging tables to target data. Currently the Capture program only supports capturing changes made by local transactions in a single database log file. With the increasing deployment of partitioned database systems in OLTP environments there is a need to replicate the operational data from the partitioned systems. This paper introduces a system called CaptureEEE which extends the Capture program to capture global transactions executed on partitioned databases supported by DB2 Enterprise-Extended Edition. The architecture and the components of CaptureEEE are presented. The algorithm for merging log entries from multiple recovery log files is discussed in detail."
"This paper describes the design and implementation of a replicable, Internet-based negotiation server for conducting bargaining-type negotiations between enterprises involved in e-commerce and e-business. Enterprises can be buyers and sellers of products/services or participants of a complex supply chain engaged in purchasing, planning, and scheduling. Multiple copies of our server can be installed to complement the services of Web servers. Each enterprise can install or select a trusted negotiation server to represent his/her interests. Web-based GUI tools are used during the build-time registration process to specify the requirements, constraints, and rules that represent negotiation policies and strategies, preference scoring of different data conditions, and aggregation methods for deriving a global cost-benefit score for the item(s) under negotiation. The registration information is used by the negotiation servers to automatically conduct bargaining type negotiations on behalf of their clients. In this paper, we present the architecture of our implementation as well as a framework for automated negotiations, and describe a number of communication primitives which are used in the underlying negotiation protocol. A constraint satisfaction processor (CSP) is used to evaluate a negotiation proposal or counterproposal against the registered requirements and constraints of a client company. In case of a constraint violation, an event is posted to trigger the execution of negotiation strategic rules, which either automatically relax the violated constraint, ask for human intervention, invoke an application, or perform other remedial operations. An Event-Trigger-Rule (ETR) server is used to manage events, triggers, and rules. Negotiation strategic rules can be added or modified at run-time. A cost-benefit analysis component is used to perform quantitative analysis of alternatives. The use of negotiation servers to conduct automated negotiation has been demonstrated in the context of an integrated supply chain scenario."
"Over the past decade, a large number of deductive object-oriented database languages have been proposed. The earliest of these languages had few object-oriented features, and more and more features have systematically been incorporated in successive languages. However, a language with a clean logical semantics that naturally accounts for all the key object-oriented features, is still missing from the literature. This article takes us another step towards solving this problem. Two features that are currently missing are the encapsulation of rule-based methods in classes, and nonmonotonic structural and behavioral inheritance with overriding, conflict resolution and blocking. This article introduces the syntax of a language with these features. The language is restricted in the sense that we have omitted other object-oriented and deductive features that are now well understood, in order to make our contribution clearer. It then defines a class of databases, called well-defined databases, that have an intuitive meaning and develops a direct logical semantics for this class of databases. The semantics is based on the well-founded semantics from logic programming. The work presented in this article establishes a firm logical foundation for deductive object-oriented databases."
"The design of webbases, database systems for supporting Web-based applications, is currently an active area of research. In this paper, we propose a 3-year architecture for designing and implementing webbases for querying dynamic Web content(i.e., data that can only be extracted by filling out multiple forms). The lowest layer, virtual physical layer, provides navigation independence by shielding the user from the complexities associated with retrieving data from raw Web sources. Next, the traditional logical layer supports site independence. The top layer is analogous to the external schema layer in traditional databases."
"Semantic interoperability is a growing challenge in the United States Department of Defense (DoD). In this paper, we describe the basis of an infrastructure for the reconciliation of relevant, but semantically heterogeneous attribute values. Three types of information are described which can be used to infer the context of attributes, making explicit hidden semantic conflicts and making it possible to adjust values appropriately. Through an extended example, we show how an automated integration agent can derive the transformations necessary to perform four tasks in a simple semantic reconciliation."
"The analysis of web usage has mostly focused on sites composed of conventional static pages. However, huge amounts of information available in the web come from databases or other data collections and are presented to the users in the form of dynamically generated pages. The query interfaces of such sites allow the specification of many search criteria. Their generated results support navigation to pages of results combining cross-linked data from many sources. For the analysis of visitor navigation behaviour in such web sites, we propose the web usage miner (WUM), which discovers navigation patterns subject to advanced statistical and structural constraints. Since our objective is the discovery of interesting navigation patterns, we do not focus on accesses to individual pages. Instead, we construct conceptual hierarchies that reflect the query capabilities used in the production of those pages. Our experiments with a real web site that integrates data from multiple databases, the German SchulWeb, demonstrate the appropriateness of WUM in discovering navigation patterns and show how those discoveries can help in assessing and improving the quality of the site."
"Over the last few years, there has been a tremendous increase in the number of interactive multimedia presentations prepared by different individuals and organizations. In this paper, we present an algebra for querying multimedia presentation databases. In contrast to the relational algebra, an algebra for interactive multimedia presentations must operate on trees whose branches reflect different possible playouts of a family of presentations. The query language supports selection type operations for locating objects and presentation paths that are of interest to the user, join type operations for combining presentations from multiple databases into a single presentation, and finally set theoretic operations for comparing different databases. The algebra operations can be used to locate presentations with specific properties and also for creating new presentations by borrowing different components from existing ones. We prove a host of equivalence results for queries in this algebra which may be used to build query optimizers for interactive presentation databases."
"We give a straightforward definition for redundancy in individual nested relations and define a new normal form that precisely characterizes redundancy for nested relations. We base our definition of redundancy on an arbitrary set of functional and multivalued dependencies, and show that our definition of nested normal form generalizes standard relational normalization theory. In addition, we give a condition that can prevent an unwanted structural anomaly in nested relations, namely, embedded nested relations with at most one tuple. Like other normal forms, our nested normal form can serve as a guide for database design."
"Abstract. Approximate query processing has emerged as a cost-effective approach for dealing with the huge data volumes and stringent response-time requirements of today's decision support systems (DSS). Most work in this area, however, has so far been limited in its query processing scope, typically focusing on specific forms of aggregate queries. Furthermore, conventional approaches based on sampling or histograms appear to be inherently limited when it comes to approximating the results of complex queries over high-dimensional DSS data sets. In this paper, we propose the use of multi-dimensional wavelets as an effective tool for general-purpose approximate query processing in modern, high-dimensional applications. Our approach is based on building wavelet-coefficient synopses of the data and using these synopses to provide approximate answers to queries. We develop novel query processing algorithms that operate directly on the wavelet-coefficient synopses of relational tables, allowing us to process arbitrarily complex queries entirely in the wavelet-coefficient domain. This guarantees extremely fast response times since our approximate query execution engine can do the bulk of its processing over compact sets of wavelet coefficients, essentially postponing the expansion into relational tuples until the end-result of the query. We also propose a novel wavelet decomposition algorithm that can build these synopses in an I/O-efficient manner. Finally, we conduct an extensive experimental study with synthetic as well as real-life data sets to determine the effectiveness of our wavelet-based approach compared to sampling and histograms. Our results demonstrate that our techniques: (1) provide approximate answers of better quality than either sampling or histograms; (2) offer query execution-time speedups of more than two orders of magnitude; and (3) guarantee extremely fast synopsis construction times that scale linearly with the size of the data."
"This paper introduces a pair of query editors for SuperSQL: SSedit and SSvisual. SSedit is a structured editor specialized for SuperSQL, which is mainly used to create a query statement from scratch. SSvisual is a WYSIWYG editor, which is mainly used to fine tune the layout and visual effects on HTML."
"The bypass technique, which was formerly restricted to selections only [KMPS94], is extended to join operations. Analogous to the selection case, the join operator may generate two output streams-the join result and its complement-whose subsequent operator sequence is optimized individually. By extending the bypass technique to joins, several problems have to be solved. (1) An algorithm for exhaustive generation of the search space for bypass plans has to be developed. (2) The search space for bypass plans is quite large. Hence, partial exploration strategies still resulting in sufficiently efficient plans have to be developed. (3) Since the complement of a join can be very large, those cases where the complement can be restricted to the complement of the semijoin have to be detected. We attack all three problems. Especially, we present an algorithm generating the optimal bypass plan and one algorithm producing near optimal plans exploring the search space only partially. As soon as disjunctions occur, bypassing results in savings. Since the join operator is often more expensive than the selection, the savings for bypassing joins are even higher than those for selections only. We give a quantitative assessment of these savings on the basis of some example queries. Further, we evaluate the performance of the two bypass plan generating algorithms. ¡®This work was supported by the German Research Council under contract DFG Ke401/6-2. "
"This paper addresses the effectiveness of two data mining techniques in analyzing and retrieving unknown behavior patterns from gigabytes of data collected in the health insurance industry. Specifically, an episode (claims) database for pathology services and a general practitioners database were used. Association rules were applied to the episode database; neural segmentation was applied to the overlaying of both databases. The results obtained from this study demonstrate the potential value of data mining in health insurance information systems, by detecting patterns in the ordering of pathology services and by classifying the general practitioners into groups reflecting the nature and style of their practices. The approach used led to results which could not have been obtained using conventional techniques."
"Author-¦Ö is a Java-based system for access control to XML documents. Author-¦Ö implements a discretionary access control model specifically tailored to the characteristics of XML documents. In particular, our system allows (i) a set-oriented and single-oriented document protection, by supporting authorizations both at document type and document level; (ii) a differentiated protection of document/document type contents by supporting multi-granularity protection objects and positive/negative authorizations; (iii) a controlled propagation of authorizations among protection objects, by enforcing multiple propagation options."
"Data mining is the discovery of previously unknown, potentially useful and hidden knowledge in databases. In this paper, we concentrate on the discovery of association rules. Many algorithms have been proposed to find association rules in databases with binary attributes. We introduce the fuzzy association rules of the form, 'If X is A then Y is B', to deal with quantitative attributes. X, Y are set of attributes and A, B are fuzzy sets which describe X and Y respectively. Using the fuzzy set concept, the discovered rules are more understandable to human. Moreover, fuzzy sets handle numerical values better than existing methods because fuzzy sets soften the effect of sharp boundaries."
"Automatic tuning has been an elusive goal for database technology for a long time and is becoming a pressing issue for modern E-services. This paper reviews and assesses the advances that have been made on this important subject during the last ten years. A major conclusion is that self-tuning database technology should be based on the paradigm of a feedback control loop, but is also bound to build on mathematical models and their proper engineering into system components. In addition, the composition of information services into truly self-tuning, higher-level E-services may require a radical departure towards simpler, highly componentized software architectures with narrow interfaces between RISC-style ""autonomic"" components."
"This qualifying dissertation is intended to review the state-of-the-art of Real-Time Database Systems under a uniprocessor and centralized environments. Due to the heterogeneity of the issues, the large amounts of information , and space limitation, we limit our presentation to the most important issues to the overall design, construction , and advancement of Real-Time Database Systems. Such topics are believed to include Transaction these issues, the most emphasis is placed on Concurrency Control and Conflict Resolution protocols due to their severe role on the overall systems performance. Other important issues that were not included in our presentation include Fault Tolerance and Failure Recovery, Predictability, and most important of all, Minimizing Transaction Support; i.e., Relaxing Atomicity and Serializability. Various solutions to many of the included topics are listed in chronological order along with their advantages, disadvantages, and limitations. While we took the liberty to debate some solutions, we list the debates of other researchers as well. The presentation concludes with the identification of five research areas, all of which are believed to be very important to the advancement of Real-Time Database Systems."
"The goal of data analysis in aviation safety is simple: improve safety. However, the path to this goal is hard to identify. What data mining methods are most applicable to this task? What data are available and how should they be analyzed? How do we focus on the most interesting results? Our answers to these questions are based on a recent research project we completed. The encouraging news is that we found a number of aviation safety offices doing commendable work to collect and analyze safety-related data. But we also found a number of areas where data mining techniques could provide new tools that either perform analyses that were not considered before, or that can now be done more easily."
"We consider an environment where distributed data sources continuously stream updates to a centralized processor that monitors continuous queries over the distributed data. Significant communication overhead is incurred in the presence of rapid update streams, and we propose a new technique for reducing the overhead. Users register continuous queries with precision requirements at the central stream processor, which installs filters at remote data sources. The filters adapt to changing conditions to minimize stream rates while guaranteeing that all continuous queries still receive the updates necessary to provide answers of adequate precision at all times. Our approach enables applications to trade precision for communication overhead at a fine granularity by individually adjusting the precision constraints of continuous queries over streams in a multi-query workload. Through experiments performed on synthetic data simulations and a real network monitoring implementation, we demonstrate the effectiveness of our approach in achieving low communication overhead compared with alternate approaches."
"When querying a temporal database, a user often makes certain semantic assumptions on stored temporal data. This paper formalizes and studies two types of semantic assumptions: point-based and interval-based. The point-based assumptions include those assumptions that use interpolation methods, while the interval-based assumptions include those that involve different temporal types (time granularities). Each assumption is viewed as a way to derive certain implicit data from the explicit data stored in the database. The database system must use all explicit as well as (possibly infinite) implicit data to answer user queries. This paper introduces a new method to facilitate such query evaluations. A user query is translated into a system query such that the answer of this system query over the explicit data is the same as that of the user query over the explicit and the implicit data. The paper gives such a translation procedure and studies the properties (safety in particular) of user queries and system queries."
"Spatial database operations are typically performed in two steps. In the filtering step, indexes and the minimum bounding rectangles (MBRs) of the objects are used to quickly determine a set of candidate objects, and in the refinement step, the actual geometries of the objects are retrieved and compared to the query geometry or each other. Because of the complexity of the computational geometry algorithms involved, the CPU cost of the refinement step is usually the dominant cost of the operation for complex geometries such as polygons. In this paper, we propose a novel approach to address this problem using efficient rendering and searching capabilities of modern graphics hardware. This approach does not require expensive pre-processing of the data or changes to existing storage and index structures, and it applies to both intersection and distance predicates. Our experiments with real world datasets show that by combining hardware and software methods, the overall computational cost can be reduced substantially for both spatial selections and joins."
"Parallel disk systems provide opportunities for exploiting I/O parallelism in two possible ways, namely via inter-request and intra-request parallelism. In this paper, we discuss the main issues in performance tuning of such systems, namely striping and load balancing, and show their relationship to response time and throughput. We outline the main components of an intelligent, self-reliant file system that aims to optimize striping by taking into account the requirements of the applications, and performs load balancing by judicious file allocation and dynamic redistributions of the data when access patterns change. Our system uses simple but effective heuristics that incur only little overhead. We present performance experiments based on synthetic workloads and real-life traces."
"As no database exists without indexes, no index implementation exists without order-preserving key compression, in particular, without prefix and tail compression. However, despite the great potentials of making indexes smaller and faster, application of general compression methods to ordered data sets has advanced very little. This paper demonstrates that the fast dictionary-based methods can be applied to order-preserving compression almost with the same freedom as in the general case. The proposed new technology has the same speed and a compression rate only marginally lower than the traditional order-indifferent dictionary encoding. Procedures for encoding and generating the encode tables are described covering such order-related features as ordered data set restrictions, sensitivity and insensitivity to a character position, and one-symbol encoding of each frequent trailing character sequence. The experimental results presented demonstrate five-folded compression on real-life data sets and twelve-folded compression on Wisconsin benchmark text fields."
"Since it quotes extensively from writings of my own, I feel obliged to respond to the article ¡°Domains, Relations and Religious Wars,¡± by R. Camps (SIGMOD Record 25, No. 3, September 1996). In that article, Camps is clearly suggesting (among other things) that my definition of the term ¡°domain¡± has changed over the years. I agree, it has! But Camps goes on to say: ¡°¡­ considering that [Date's book An Introduction to Database Systems] was the bible [Camps' italics] where most university graduates all over the world learnt, I believe that Date can be held partly responsible for the lack of implementation of domains [in today's SQL DBMSs].¡±"
"This paper illustrates how the notion of pattern can be used in the automatic analysis and synthesis of diagrams, applied particularly to the automatic marking of ER-diagrams. The paper describes how diagram patterns fit into a general framework for diagram interpretation and provides examples of how patterns can be exploited in other fields. Diagram patterns are defined and specified within the area of ER-diagrams. The paper also shows how patterns are being exploited in a revision tool for understanding ER-diagrams."
"The Relational On-Line Analytical Processing (ROLAP) is emerging as the dominant approach in data warehousing with decision support applications. In order to enhance query performance, the ROLAP approach relies on selecting and materializing in summary tables appropriate subsets of aggregate views which are then engaged in speeding up OLAP queries. However, a straight forward relational storage implementation of materialized ROLAP views is immensely wasteful on storage and incredibly inadequate on query performance and incremental update speed. In this paper we propose the use of Cubetrees, a collection of packed and compressed R-trees, as an alternative storage and index organization for ROLAP views and provide an efficient algorithm for mapping an arbitrary set of OLAP views to a collection of Cubetrees that achieve excellent performance. Compared to a conventional (relational) storage organization of materialized OLAP views, Cubetrees offer at least a 2-1 storage reduction, a 10-1 better OLAP query performance, and a 100-1 faster updates. We compare the two alternative approaches with data generated from the TPC-D benchmark and stored in the Informix Universal Server (IUS). The straight forward implementation materializes the ROLAP views using IUS tables and conventional B-tree indexing. The Cubetree implementation materializes the same ROLAP views using a Cubetree Datablade developed for IUS. The experiments demonstrate that the Cubetree storage organization is superior in storage, query performance and update speed."
"We give a tutorial introduction to the basic definitions surrounding the idea of constraint databases, and survey and indicate some of the achieved research results on this subject. This paper is not written as a scholarly piece, nor as polished course notes, but rather as something like the transcript of an invited talk I gave at a meeting bringing together researchers from finite model theory, database theory, and computer-aided verification, which was held at Schloss Dagstuhl in October 1999.Very recently the first book on the subject appeared [20]. It covers the state of the art in constraint databases up to, say, mid 1999 [20]. You should see this paper merely as an appetizer for the book. I will also not try to be complete in my bibliographical references. Again, see the book for that."
"We propose a framework for integrating data from multiple relational sources into an XML document that both conforms to a given DTD and satisfies predefined XML constraints. The framework is based on a specification language, AIG, that extends a DTD by (1) associating element types with semantic attributes (inherited and synthesized, inspired by the corresponding notions from Attribute Grammars), (2) computing these attributes via parameterized SQL queries over multiple data sources, and (3) incorporating XML keys and inclusion constraints. The novelty of AIG consists in semantic attributes and their dependency relations for controlling context-dependent, DTD-directed construction of XML documents, as well as for checking XML constraints in parallel with document-generation. We also present cost-based optimization techniques for efficiently evaluating AIGs, including algorithms for merging queries and for scheduling queries on multiple data sources. This provides a new grammar-based approach for data integration under both syntactic and semantic constraints."
"Digital archives are dedicated to the long-term preservation of electronic information and have the mandate to enable sustained access despite rapid technology changes. Persistent archives are confronted with heterogeneous data formats, helper applications, and platforms being used over the lifetime of the archive. This is not unlike the interoperability challenges, for which mediators are devised. To prevent technological obsolescence over time and across platforms, a migration approach for persistent archives is proposed based on an XML infrastructure.We extend current archival approaches that build upon standardized data formats and simple metadata mechanisms for collection management, by involving high-level conceptual models and knowledge representations as an integral part of the archive and the ingestion/migration processes. Infrastructure independence is maximized by archiving generic, executable specifications of (i) archival constraints (i.e., ""model validators""), and (ii) archival transformations that are part of the ingestion process. The proposed architecture facilitates construction of self-validating and self-instantiating knowledge-based archives. We illustrate our overall approach and report on first experiences using a sample collection from a collaboration with the National Archives and Records Administration (NARA)."
"We describe the tools and theory of a comprehensive system for database design, and show how they work together to support multiple conceptual and logical design processes. The Database Design and Evaluation Workbench (DDEW) system uses a rigorous, information-content-preserving approach to schema transformation, but combines it with heuristics, guess work, and user interactions. The main contribution lies in illustrating how theory was adapted to a practical system, and how the consistency and power of a design system can be increased by use of theory."
"When we design an object-oriented database schema, we need to normalize object classes as we do for relations when designing a relational database schema. However, the normalization process for an object class cannot be the same as that of a relation, because of the distinct characteristics of an object-oriented data model such as complex attributes, collection data types, and the usage of object identifiers in place of relational key attributes. We need only one kind of dependency proposed here -- the object functional dependency -- which specifies the dependency of object attributes with respect to the object identifier. We also propose the object normal form of an object class, for which all determinants of object functional dependencies are object identifiers. There is no risk of update anomalies as long as all object classes are in the object normal form."
"Literature search is an important part of any research and publication activity. In the era of electronic database and explosion of scientific publication, keywords play an immense role in digging out the relevant published material, since these keywords act as ""keys"" to unlock the desired scientific paper abstracts/full articles from a vast collection of related publications1. Hence it is important to include and select pertinent keywords which can easily identify and search relevant references and filter-out the large body of unwanted material. It is, therefore, important that certain words may be added to the abstract of the article which a future researcher might be expected to use as keywords in MEDLINE search. These words should be such that they would make an article which might have remained invisible to the researcher visible on search2. It has been observed that the keywords included along with the abstracts by some journals in the research reports frequently do not identify relevant papers. In view of this problem we have analysed an issue of the Indian Journal of Pharmacology [2002; Vol 34 (Issue 1): 3-58] for the relevance of the keywords used."
"A broad spectrum of data is available on the Web in distinct heterogeneous sources, and stored under different formats. As the number of systems that utilize this heterogeneous data grows, the importance of data translation and conversion mechanisms increases greatly. In this paper we present a new translation system, based on schema-matching, aimed at simplifying the intricate task of data conversion. We observe that in many cases the schema of the data in the source system is very similar to that of the target system. In such cases, much of the translation work can be done automatically, based on the schemas similarity. This saves a lot of effort for the user, limiting the amount of programming needed. We define common schema and data models, in which schemas and data (resp.) from many common models can be represented. Using a rule-based method, the source schema is compared with the target one, and each component in the source schema is matched with a corresponding component in the target schema. Then, based on the matching achieved, data instances of the source schema can be translated to instances of the target schema. We show that our schema-based translation system allows a convenient specification and customization of data conversions, and can be easily combined with the traditional data-based translation languages."
"We present a new client cache consistency algorithm for client caching database management systems. The algorithm, called Asynchronous Avoidance-based Cache Consistency (AACC), provides both good performance as well as a low abort rate. We present simulation results that compare AACC with two leading cache consistency algorithms: Adaptive Callback Locking (ACBL) and Adaptive Optimistic Concurrency Control (AOCC). Callback cache consistency (e.g. ACBL) is the most widely implemented algorithm due to its low abort rate and good performance. AOCC is an optimistic algorithm that has been shown to outperform ACBL under certain workload and system configurations. Until now one could either have high performance and high abort rate as in AOCC, or relatively lower performance but the low abort rate of ACBL. Our performance study shows that AACC outperforms both ACBL and AOCC for important workloads and system configurations. AACC has the high performance of AOCC, as well as the robustness and low abort rate of ACBL."
"We describe the design and implementation of a new data layout scheme, called multi-dimensional clustering, in DB2 Universal Database Version 8. Many applications, e.g., OLAP and data warehousing, process a table or tables in a database using a multi-dimensional access paradigm. Currently, most database systems can only support organization of a table using a primary clustering index. Secondary indexes are created to access the tables when the primary key index is not applicable. Unfortunately, secondary indexes perform many random I/O accesses against the table for a simple operation such as a range query. Our work in multi-dimensional clustering addresses this important deficiency in database systems. Multi-Dimensional Clustering is based on the definition of one or more orthogonal clustering attributes (or expressions) of a table. The table is organized physically by associating records with similar values for the dimension attributes in a cluster. We describe novel techniques for maintaining this physical layout efficiently and methods of processing database operations that provide significant performance improvements. We show results from experiments using a star-schema database to validate our claims of performance with minimal overhead."
"The two observations that 1) many XML documents are stored in a database or generated from data stored in a database and 2) processing these documents with XSL stylesheet processors is an important, often recurring task justify a closer look at the current situation. Typically, the XML document is retrieved or constructed from the database, exported, parsed, and then processed by a special XSL processor. This cumbersome process clearly sets the goal to incorporate XSL stylesheet processing into the database engine.    We describe one way to reach this goal by translating XSL stylesheets into algebraic expressions. Further, we present algorithms to optimize the template rule selection process and the algebraic expression resulting from the translation. Along the way, we present several undecidability results hinting at the complexity of the problem on hand."
"Recent work on querying data streams has focused on systems where newly arriving data is processed and continuously streamed to the user in real-time. In many emerging applications, however, ad hoc queries and/or intermittent connectivity also require the processing of data that arrives prior to query submission or during a period of disconnection. For such applications, we have developed PSoup, a system that combines the processing of ad-hoc and continuous queries by treating data and queries symmetrically, allowing new queries to be applied to old data and new data to be applied to old queries. PSoup also supports intermittent connectivity by separating the computation of query results from the delivery of those results. PSoup builds on adaptive query processing techniques developed in the Telegraph project at UC Berkeley. In this paper, we describe PSoup and present experiments that demonstrate the effectiveness of our approach."
"Online alternative finance is rapidly growing worldwide while driving financial inclusion thanks to the growing body of data made available by the expansion of cyberspace and the advancement of machine learning and other technology. The epicenter of the growth is China, but online alternative finance is also continuing to grow in developed countries, such as the United States and the United Kingdom, through the creation of new market segments and a shift from some existing financial institutions. The sort of information used for loan screening in the case of online alternative finance is different from that used in the case of finance provided by existing financial institutions. There are even cases where credit history information is not used. Even when credit history information is used, the range of additional data used for loan screening is expanding to include information related to electronic commerce (EC) sites, in the case of corporate borrowers, and detailed information on personality and academic achievement and the history of residential moving, in the case of individual borrowers. "
"Although several access control policies can be devised for controlling access to information, all existing authorization models, and the corresponding enforcement mechanisms, are based on a specific policy (usually the closed policy). As a consequence, although different policy choices are possible in theory, in practice only a specific policy can be actually applied within a given system. However, protection requirements within a system can vary dramatically, and no single policy may simultaneously satisfy them all."
"The Decomposition Storage Model (DSM) vertically partitions all attributes of a given relation. DSM has excellent I/O behavior when the number of attributes touched in the query is small. It also has a better cache footprint than the n N-ary storage model (NSM) that is used by most database system. However, DSM incurs a high cost in reconstructing the original tuple from the partitions. We first revisit some of the performance problems associated with DSM. We suggest a simple indexing strategy and compare different reconstruction algorithms. The paper then proposes a new mirroring scheme, termed fractured mirrors, using both NSM and DSM models. This scheme combines the best aspects of both models, along with the added benefit of mirroring to better serve an ad-hoc query workload. A prototype system has been built using the Shore storage manager and performance is evaluated using queries from the TPC-H workload."
"In recent years, Massively Parallel Processors have increasingly been used to manage and query vast amounts of data. Dramatic performance improvements are achieved through distributed execution of queries across many nodes. Query optimization for such system is a challenging and important problem. In this paper we describe the Query Optimizer inside the SQL Server Parallel Data Warehouse product (PDW QO). We leverage existing QO technology in Microsoft SQL Server to implement a cost-based optimizer for distributed query execution. By properly abstracting metadata we can readily reuse existing logic for query simplification, space exploration and cardinality estimation. Unlike earlier approaches that simply parallelize the best serial plan, our optimizer considers a rich space of execution alternatives, and picks one based on a cost-model for the distributed execution environment. The result is a high-quality, effective query optimizer for distributed query processing in an MPP."
"One of the central tasks in managing, monitoring and mining data streams is that of identifying outliers. There is a long history of study of various outliers in statistics and databases, and a recent focus on mining outliers in data streams. Here, we adopt the notion of ""deviants"" from Jagadish et al. (1999) as outliers. Deviants are based on one of the most fundamental statistical concept of standard deviation (or variance). Formally, deviants are defined based on a representation sparsity metric, i.e., deviants are values whose removal from the dataset leads to an improved compressed representation of the remaining items. Thus, deviants are not global maxima/minima, but rather these are appropriate local aberrations. Deviants are known to be of great mining value in time series databases. We present first-known algorithms for identifying deviants on massive data streams. "
"Some aggregate and grouping queries are conceptually simple, but difficult to express in SQL. This difficulty causes both conceptual and implementation problems for the SQLbased database system. Complicated queries and views are hard to understand and maintain. Further, the code produced is sometimes unnecessarily inefficient, as we demonstrate experimentally using a commercial database system. In this paper, we examine a class of queries involving (potentially repeated) selection, grouping and aggregation over the same groups, and propose an extension of SQL syntax that allows the succinct representation of these queries. We propose a new relational algebra operation that represents several levels of aggregation over the same groups in an operand relation. We demonstrate that the extended relational operator can be evaluated using efficient algorithms. We describe a translation from the extended SQL language into our algebraic language. We have implemented a preprocessor that evaluates our extended language on top of a commercial database system. We demonstrate that on a variety of examples, our implementation improves performance over standard SQL representations of the same examples by orders of magnitude."
"Analysts and decision-makers use what-if analysis to assess the e?ects of hypotheti- cal scenarios. What-if analysis is currently supported by spreadsheets and ad-hoc O L AP tools. Unfortunately, the former lack seam- less integration with the data and the lat- ter lack ¡ãexibility and performance appropri- ate for O L AP applications. To tackle these problems we developed the Sesamesystem, which models an hypothetical scenario as a list of hypothetical modications on the ware- house views and fact data. We provide formal scenario syntax and semantics, which extend view update semantics for accomodating the special requirements of O L AP. We focus on query algebra operators suitable for perform- ing spreadsheet-style computations. Then we present Sesame's optimizer and its corner- stone substitution and rewriting mechanisms. Substitution enables lazy evaluation of the hy- pothetical updates. The substitution module delivers orders-of-magnitude optimizations in cooperation withtherewriterthatusesknowl- edge of arithmetic, relational, ¡¥nancial and other operators. Finally we discuss the chal- lenges that the size of the scenario specica- tionsandthe arbitrarynatureof theoperators pose to the rewriter."
"We describe an investigation into e-mail content mining for author identification, or authorship attribution, for the purpose of forensic investigation. We focus our discussion on the ability to discriminate between authors for the case of both aggregated e-mail topics as well as across different e-mail topics. An extended set of e-mail document features including structural characteristics and linguistic patterns were derived and, together with a Support Vector Machine learning algorithm, were used for mining the e-mail content. Experiments using a number of e-mail documents generated by different authors on a set of topics gave promising results for both aggregated and multi-topic author categorisation."
"Existing data-integration systems based on the mediation architecture employ a variety of mechanisms to describe the query-processing capabilities of sources. However, these systems do not compute the capabilities of the mediators based on the capabilities of the sources they integrate. In this paper, we proposed a framework to capture a rich variety of query-processing capabilities of data sources and mediators. We present algorithms to compute the set of supported queries of a mediator, based on the capability limitations of its sources. Our algorithms take into consideration a variety of query-processing techniques employed by mediators to enhance the set of supported queries."
"Derived data is maintained in a database system to correlate and summarize base data which records real world facts. As base data changes, derived data needs to be recomputed. This is often implemented by writing active rules that are triggered by changes to base data. In a system with rapidly changing base data, a database with a standard rule system may consume most of its resources running rules to recompute data. This paper presents the rule system implemented as part of the STandard Real-time Information Processor (STRIP). The STRIP rule system is an extension of SQL3-type rules that allows groups of rule actions to be batched together to reduce the total recomputation load on the system. In this paper we describe the syntax and semantics of the STRIP rule system, present an example set of rules to maintain stock index and theoretical option prices in a program trading application, and report the results of experiments performed on the running system. The experiments verify that STRIP's rules allow much more efficient derived data maintenance than conventional rules without batching."
"Traditional indexes aim at optimizing the node accesses during query processing, which, however, does not necessarily minimize the total cost due to the possibly large number of random accesses. In this paper, we propose a general framework for adaptive indexes that improve overall query cost. The performance gain is achieved by allowing index nodes to contain a variable number of disk pages. Update algorithms dynamically re-structure adaptive indexes depending on the data and query characteristics. Extensive experiments show that adaptive B- and R-trees significantly outperform their conventional counterparts, while incurring minimal update overhead."
"The amount of scientific and technical information is growing exponentially. As a result, the scientific community has been overwhelmed by the information published in number of new books, journal articles, and conference proceedings. In addition to increasing number of publications, advances in information technology have dramatically reduced the barriers in electronic publishing and distribution of information over networks virtually anywhere in the world. As a result, the scientific community is facing the problem of locating relevant or interesting information. To address the problem of information overload and to sift all available information sources for useful information, recommender systems or filtering systems have emerged. Generally, recommender systems are used online to suggest items that users find interesting, thereby, benefiting both the user and merchant. Recommender systems benefit the user by making him suggestions on items that he is likely to purchase and the business by increase of sales. Filtering information or generation of recommendatio ns by the recommender systems mimic the process of information retrieval systems by incorporating advanced profile building techniques, item/user representation techniques, filtering and recommendation techniques, and profile adaptation techniques. This paper addresses the application domain analysis, functional classification, advantages and disadvantages of various filtering and recommender systems."
"With the proliferation of the world's ¡°information highways¡± a renewed interest in efficient document indexing techniques has come about. In this paper, the problem of incremental updates of inverted lists is addressed using a new dual-structure index. The index dynamically separates long and short inverted lists and optimizes retrieval, update, and storage of each type of list. To study the behavior of the index, a space of engineering trade-offs which range from optimizing update time to optimizing query performance is described. We quantitatively explore this space by using actual data and hardware in combination with a simulation of an information retrieval system. We then describe the best algorithm for a variety of criteria."
"Significant performance advantages can be gained by implementing a database system on a cache-coherent shared memory multiprocessor. However, problems arise when failures occur. A single node (where a node refers to a processor/memory pair) crash may require a reboot of the entire shared memory system. Fortunately, shared memory multiprocessors that isolate individual node failures are currently being developed. Even with these, because of the side effects of the cache coherency protocol, a transaction executing strictly on a single node may become dependent on the validity of the memory of many nodes thereby inducing unnecessary transaction aborts. This happens when database objects, such as records, and database support structures, such as index structures and shared lock tables, are stored in shared memory.In this paper, we propose crash recovery protocols for shared memory database systems which avoid the unnecessary transaction aborts induced by the effects of using shared physical memory. Our recovery protocols guarantee that if one or more nodes crash, all the effects of active transactions running on the crashed nodes will be undone, and no effects of transactions running on nodes which did not crash will be undone. In order to show the practicality of our protocols, we discuss how existing features of cache-coherent multiprocessors can be utilized to implement these recovery protocols. Specifically, we demonstrate that (1) for many types of database objects and support structures, volatile (in-memory) logging is sufficient to avoid unnecessary transaction aborts, and (2) a very low overhead implementation of this strategy can be achieved with existing multiprocessor features."
"The objective of the project HyperStorM (¡¯Hypermedia Document Storage and Modeling¡¯) is to use objec~oriented database technology to administer structured documents like SGMLand HyTime-documents. It 1s an asset of formats such as SGML to allow for the seam!ess integration of metainformation, HyTime provides a set of archi~ectural forms, i.e., templates with a predefine semantics to be used in hypermedia documents for scheduling or hyperlinking. to give examples. Requirements. We have identified the following requirements in the context of structured document storage: the database application has to administer documents conformant to arbitrary document-type definit~ons ( DTDs) With regard to declarative access, it must be possible to formulate queries in a more precise way, e.g., by referring to documents¡¯ structure, in order tO COPe with th~ increase of documents in number and size. Updates on documents are advantageous as, first,, it may be pointless to only insert entire documents when considering certain document types, such as encyclopedia or codes of law. Second, t¡°ormats such as SGML are m use to capture structured reformation going beyond the conventional notion of ¡®document,¡¯. Document components¡¯ semantics should be available within the dat,abase application to ensure adequate performance, and to allow for querying based on such concepts Finally, we think that. wnth regard to access vm the WWW documents¡¯ conversion to HTML should take place at the server site: transformation of docume~ts might not be straightforward, hut may instead be driven by the database context. Then, the process is more efficient when carried out in the database. System Overview. Due to the dynamic nature of the sys~em. most structures comprising the document conrent have to be generated at mntime. & a first"
"Scheduling query execution plans is an important component of query optimization in parallel database systems. The problem is particularly complex in a shared-nothing execution environment, where each system node represents a collection of time-shareable resources (e.g., CPU(s), disk(s), etc.) and communicates with other nodes only by message-passing. Significant research effort has concentrated on only a subset of the various forms of intra-query parallelism so that scheduling and synchronization is simplified. In addition, most previous work has focused its attention on one-dimensional models of parallel query scheduling, effectively ignoring the potential benefits of resource sharing. In this paper, we develop an approach that is more general in both directions, capturing all forms of intra-query parallelism and exploiting sharing of multi-dimensional resource nodes among concurrent plan operators. This allows scheduling a set of independent query tasks (i.e., operator pipelines) to be seen as an instance of the multi-dimensional bin-design problem. Using a novel quantification of coarse grain parallelism, we present a list scheduling heuristic algorithm that is provably near-optimal in the class of coarse grain parallel executions (with a worst-case performance ratio that depends on the number of resources per node and the granularity parameter). We then extend this algorithm to handle the operator precedence constraints in a bushy query plan by splitting the execution of the plan into synchronized phases. Preliminary performance results confirm the effectiveness of our scheduling algorithm compared both to previous approaches and the optimal solution. Finally, we present a technique that allows us to relax the coarse granularity restriction and obtain a list scheduling method that is provably near-optimal in the space of all possible parallel schedules."
"Data in a warehouse typically has multiple dimensions of interest, such as location, time, and product. It is well-recognized that these dimensions have hierarchies deened on them, such as \store-city-state-region"" for location. The standard way to model such data is with a star/snowwake schema. However, current approaches do not give a rst-class status to dimensions. Consequently, a substantial class of interesting queries involving dimension hierarchies and their interaction with the fact tables are quite verbose to write, hard to read, and diicult to optimize. We propose the SQL(H) model and a natural extension to the SQL query language, that gives a rst-class status to dimensions, and we pin down its semantics. Our model permits structural and schematic heterogeneity in dimension hierarchies, situations often arising in practice that cannot be modeled satisfactorily using the star/snowwake approach. We show using examples that sophisticated queries involving dimension hierarchies and their interplay with aggregation can be expressed concisely in SQL(H). By comparison, expressing such queries in SQL would involve a union of numerous complex sequences of joins. Finally, we develop an eecient implementation strategy for computing SQL queries, based on an algorithm for hierarchical joins, and the use of dimension indexes. "
"In a path-breaking paper last year Pat and Betty O¡¯Neil and Gerhard Weikum pro posed a self-tuning improvement to the Least Recently Used (LRU) buffer management algorithm[l5]. Their improvement is called LRU/k and advocates giving priority to buffer pages baaed on the kth most recent access. (The standard LRU algorithm is denoted LRU/l according to this terminology.) If Pl¡¯s kth most recent access is more more recent than P2¡¯s, then Pl will be replaced after P2. Intuitively, LRU/k for k > 1 is a good strategy, because it gives low priority to pages that have been scanned or to pages that belong to a big randomly accessed file (e.g., the account file in TPC/A). They found that LRU/S achieves most of the advantage of their method. The one problem of LRU/S is the processor"
"Clustering of large data bases is an important research area with a large variety of applications in the data base context. Missing in most of the research efforts are means for guiding the clustering process and understanding the results, which is especially important for high dimensional data. Visualization technology may help to solve this problem since it provides effective support of different clustering paradigms and allows a visual inspection of the results. The HD-Eye (high-dim. eye) system shows that a tight integration of advanced clustering algorithms and state-of-the-art visualization techniques is powerful for a better understanding and effective guidance of the clustering process, and therefore can help to significantly improve the clustering results."
"In this paper we propose a new operator for advanced exploration of large multidimensional databases. The proposed operator can automatically generalize from a specific problem case in detailed data and return the broadest context in which the problem occurs. Such a functionality would be useful to an analyst who after observing a problem case, say a drop in sales for a product in a store, would like to find the exact scope of the problem. With existing tools he would have to manually search around the problem tuple trying to draw a pattern. This process is both tedious and imprecise. Our proposed operator can automate these manual steps and return in a single step a compact and easy-to-interpret summary of all possible maximal generalizations along various roll-up paths around the case. We present a fle xible cost-based framework that can generalize various kinds of behaviour (not simply drops) while requiring little additional customization from the user. We design an algorithm that can work efficiently on large multidimensional hierarchical data cubes so as to be usable in an interactive setting."
"A new model to evaluate dependencies in data mining problems is presented and discussed. The well-known concept of the association rule is replaced by the new definition of dependence value, which is a single real number uniquely associated with a given itemset. Knowledge of dependence values is sufficient to describe all the dependencies characterizing a given data mining problem. The dependence value of an itemset is the difference between the occurrence probability of the itemset and a corresponding ¡°maximum independence estimate.¡± This can be determined as a function of joint probabilities of the subsets of the itemset being considered by maximizing a suitable entropy function. So it is possible to separate in an itemset of cardinaltiy k the dependence inherited from its subsets of cardinality (k ? 1) and the specific inherent dependence of that itemset."
"The need to automatically extract and classify the contents of multimedia data archives such as images, video, and text documents has led to significant work on similarity based retrieval of data. To date, most work in this area has focused on the creation of index structures for similarity based retrieval. There is very little work on developing formalisms for querying multimedia databases that support similarity based computations and optimizing such queries, even though it is well known that feature extraction and identification algorithms in media data are very expensive. We introduce a similarity algebra that brings together relational operators and results of multiple similarity implementations in a uniform language. The algebra can be used to specify complex queries that combine different interpretations of similarity values and multiple algorithms for computing these values. We prove equivalence and containment relationships between similarity algebra expressions and develop query rewriting methods based on these results. We then provide a generic cost model for evaluating cost of query plans in the similarity algebra and query optimization methods based on this model. We supplement the paper with experimental results that illustrate the use of the algebra and the effectiveness of query optimization methods using the Integrated Search Engine (I.SEE) as the testbed."
"The management of organizational knowledge is becoming a key requirement in many engineering organizations. In many cases, it is difficult to capture this knowledge directly, as it is hidden in the way-of-working followed by networks of highly qualified specialists. Moreover, much of this knowledge is strongly context-dependent, so rules to be followed must be augmented by adequate situation analysis. Hardware and software tools used to support these processes are strongly heterogeneous, involving significant effort of usage and very different kinds of data. In this paper, we propose SURFHVV GDWD ZDUH KRXVHV as a means to remedy these problems. A process data warehouse, according to our approach, is centered around a knowledge-based metadata repository which records and drives a heterogeneous engineering process, supported by selected materialized instance data. We follow a concept-centered approach expanding ideas from the European DWQ project and illustrate our solution with a prototypical process data warehouse for chemical engineering design developed within the Collaborative Research Centre IMPROVE at Aachen University of Technology."
Invited Talk I.- Some Advances in Data-Mining Techniques.- Web Exploration.- Querying Semantically Tagged Documents on the World-Wide Web.- WWW Exploration Queries.- Strategies for Filtering E-mail Messages Combining Content-Based and Sociological Filtering with User-Stereotypes.- Interactive Query Expansion in a Meta-search Engine.- Database Technology.- On the Optimization of Queries containing Regular Path Expressions.- A Database Array Algebra for Spatio-Temporal Data and Beyond.- Dynamic Relationships and Their Propagation and Concurrency Semantics in Object-Oriented Databases.- Tracking Moving Objects Using Database Technology in DOMINO.- OLOG: A Deductive Object Database Language.
"Once again, scientists were called upon to take greater role in the political process. And this time, they did! We report on the continuous debate on the nation's R&D policy. We also cover funding opportunities from DoD and NSF."
"Spatio-temporal data warehouses store enormous amount of data. They are usually exploited by spatiotemporal OLAP systems to extract relevant information. For extracting interesting information, the current user launches spatio-temporal OLAP (ST-OLAP) queries to navigate within a geographic data cube (Geo-cube). Very often choosing which part of the Geo-cube to navigate further, and thus designing the forthcoming ST-OLAP query, is a difficult task. So, to help the current user refine his queries after launching in the geo-cube his current query, we need a ST-OLAP queries suggestion by exploiting a Geo-cube. "
"Temporal functional dependencies (TFD) are defined  for temporal databases that include object identity. It is argued that object identity can overcome certain semantic diffuculties with existing temporal relational data models. Practical applications of TFDs in object bases are discussed. Reasoning about TFDs is at the center of this paper. It turns out that the distinction between acyclic and cyclic schemas is significant. For acyclic schemas, a complete axiomatization for finite implication is given and an algorithm for deciding finite implication provided. The same axiomatization is proven complete for unrestricted implication in unrestricted schemas, which can be cyclic. An interesting result is that there are cyclic schemas for which unrestricted and finite  implication do not coincide. TFDs relate and extend some earlier work on dependency theory in temporal databases. Throughout this paper, the construct of TFD is compared with the notion of temporal FD introduced by Wang et al. (1997). A comparison with other related work is provided at the end of the article."
"The national and international standards committees responsible for Database Language SQL have proposed a candidate extension for SQL Persistent Stored Modules (SQL/PSM). The purpose of this extension is to provide a computationally complete language for the declaration and invocation of SQL stored modules and routines. Typically, such routines are stored in a database Server and executed from an application Client in a Client/Server environment.The proposed SQL/PSM consists of syntax and semantics for variable and cursor declarations, function and procedure (routines) invocations, condition handling, and control statements for looping and branching. An SQL routine is block structured, with each block consisting of local variable and condition handler declarations, a list of SQL statements, and local condition handler execution.Condition handling is a major new feature of SQL/PSM (henceforth referred to as PSM), although the style and comprehensiveness of the specification is still an issue in further progression of the standard. The specification currently under ballot includes conditions for exceptions, warnings, and other completions such as success of no data, and handlers for Continue, Exit, Redo, and Undo.Condition handling allows the user to separate condition handling code from the main flow of a routine, thereby eliminating the need to write numerous short and redundant code fragments to handle each unique condition. In some database products, one cannot even resolve the condition in the Server and must instead resort to the Client application program for resolution. Such approaches are often tedious, error-prone, and inflexible. "
"Materialized views have been found to be very effective at speeding up queries, and are increasingly being supported by commercial databases and data warehouse systems. However, whereas the amount of data entering a warehouse and the number of materialized views are rapidly increasing, the time window available for maintaining materialized views is shrinking. These trends necessitate efficient techniques for the maintenance of materialized views."
"In many applications, new data is being generated every day. Often an index of the data of a past window of days is required to answer queries efficiently. For example, in a warehouse one may need an index on the sales records of the last week for efficient data mining, or in a Web service one may provide an index of Netnews articles of the past month. In this paper, we propose a variety of wave indices where the data of a new day can be efficiently added, and old data can be quickly expired, to maintain the required window. We compare these schemes based on several system performance measures, such as storage, query response time, and maintenance work, as well as on their simplicity and ease of coding."
"Phrase matching is a common IR technique to search text and identify relevant documents in a document collection. Phrase matching in XML presents new challenges as text may be interleaved with arbitrary markup, thwarting search techniques that require strict contiguity or close proximity of keywords. We present a technique for phrase matching in XML that permits dynamic specification of both the phrase to be matched and the markup to be ignored. We develop an effective algorithm for our technique that utilizes inverted indices on phrase words and XML tags. We describe experimental results comparing our algorithm to an indexed-nested loop algorithm that illustrate our algorithm's efficiency."
"Similarity queries are fundamental operations that are used extensively in many modern applications, whereas disk arrays are powerful storage media of increasing importance. The basic trade-off in similarity query processing in such a system is that increased parallelism leads to higher resource consumptions and low throughput, whereas low parallelism leads to higher response times. Here, we propose a technique which is based on a careful investigation of the currently available data in order to exploit parallelism up to a point, retaining low response times during query processing. The underlying access method is a variation of the R*-tree, which is distributed among the components of a disk array, whereas the system is simulated using event-driven simulation. The performance results conducted, demonstrate that the proposed approach outperforms by factors a previous branch-and-bound algorithm and a greedy algorithm which maximizes parallelism as much as possible. Moreover, the comparison of the proposed algorithm to a hypothetical (non-existing) optimal one (with respect to the number of disk accesses) shows that the former is on average two times slower than the latter."
"Gray discusses his childhood in Rome and education at the University of California, Berkeley. He explains the influence of Sputnik, Norbert Wiener's view of cybernetics and society, the social impact of computing, and the artificial intelligence papers of Newell and"
"Selectivity estimation of queries is an important and well-studied problem in relational database systems. In this paper, we examine selectivity estimation in the context of Geographic Information Systems, which manage spatial data such as points, lines, poly-lines and polygons. In particular, we focus on point and range queries over two-dimensional rectangular data. We propose several techniques based on using spatial indices, histograms, binary space partitionings (BSPs), and the novel notion of spatial skew. Our techniques carefully partition the input rectangles into subsets and approximate each partition accurately. We present a detailed experimental study comparing the proposed techniques and the best known sampling and parametric techniques. We evaluate them using synthetic as well as real-life TIGER datasets. Based on our experiments, we identify a BSP based partitioning that we call Min-Skew which consistently provides the most accurate selectivity estimates for spatial queries. The Min-Skew partitioning can be constructed efficiently, occupies very little space, and provides accurate selectivity estimates over a broad range of spatial queries."
"The democratization of ubiquitous computing (access data anywhere, anytime, anyhow), the increasing connection of corporate databases to the Internet and the today's natural resort to Web-hosting companies strongly emphasize the need for data confidentiality. Database servers arouse user's suspicion because no one can fully trust traditional security mechanisms against more and more frequent and malicious attacks and no one can be fully confident on an invisible DBA administering confidential data. This paper gives an in-depth analysis of existing security solutions and concludes on the intrinsic weakness of the traditional server-based approach to preserve data confidentiality. With this statement in mind, we propose a solution called C-SDA (Chip-Secured Data Access), which enforces data confidentiality and controls personal privileges thanks to a client-based security component acting as a mediator between a client and an encrypted database. This component is embedded in a smartcard to prevent any tampering to occur. This cooperation of hardware and software security components constitutes a strong guarantee against attacks threatening personal as well as business data."
"This second Long Range Planning special issue on PLS-SEMin strategic management research and practice seeks to further progress towards this goal. The journal received 41 articles for its special issue on PLS-SEM, twelve of which completed a thorough review process successfully. Based on the number of high quality manuscripts, a decision was made to split the special issue. In the first Long Range Planning special issue on PLS-SEM in strategic management (Hair et al., 2012a; Robins, 2012), the focus was on methodological developments and their application (Becker et al., 2012; Furrer et al., 2012; Gudergan et al., 2012; Hair et al., 2012a,b,c; Money et al., 2012; Rigdon, 2012). "
"We propose a new class of algorithms that can be used to speed up the execution of multi-way join queries or of queries that involve one or more joins and a group-by. These new evaluation techniques allow to perform several hash-based operations (join and grouping) in one pass without repartitioning intermediate results. These techniques work particularly well for joining hierarchical structures, e.g., for evaluating functional join chains along key/foreign-key relationships. The idea is to generalize the concept of hash teams as proposed by Graefe et.al [GBC98] by indirectly partitioning the input data. Indirect partitioning means to partition the input data on an attribute that is not directly needed for the next hash-based operation, and it involves the construction of bitmaps to approximate the partitioning for the attribute that is needed in the next hash-based operation. Our performance experiments show that such generalized hash teams perform significantly better than conventional strategies for many common classes of decision support queries."
Personalization is here defined as a process of changing a system to increase its personal relevance. This may have a work or social motivation. A taxonomy of motivations is developed and illustrated by application to mobile phones and e-commerce Web pages.
"The goal of the Garlic [1] project is to build a multimedia information system capable of integrating data that resides in different database systems as well as in a variety of non-database data servers. This integration must be enabled while maintaining the independence of the data servers, and without creating copies of their data. ""Multimedia"" should be interpreted broadly to mean not only images, video, and audio, but also text and application specific data types (e.g., CAD drawings, medical objects, &hellip;). Since much of this data is naturally modeled by objects, Garlic provides an object-oriented schema to applications, interprets object queries, creates execution plans for sending pieces of queries to the appropriate data servers, and assembles query results for delivery back to the applications. A significant focus of the project is support for ""intelligent"" data servers, i.e., servers that provide media-specific indexing and query capabilities [2]. Database optimization technology is being extended to deal with heterogeneous collections of data servers so that efficient data access plans can be employed for multi-repository queries.A prototype of the Garlic system has been operational since January 1995. Queries are expressed in an SQL-like query language that has been extended to include object-oriented features such as reference-valued attributes and nested sets. In addition to a C++ API, Garlic supports a novel query/browser interface called PESTO. "
"We describe a scheme to fragment and distribute centralized databases. ¡¯ The problem is motivated by trends towards down-sizing and reorganization, reflecting actual, often distributed responsibilities within companies. A major practical requirement is that existing application code must be left unchanged. We present SQL extensions to specify ownership and data replication information declaratively. From this, a compiler generates triggers and view definitions that implement the distributed scheme, on top of a collection of local databases. Our strategy has been applied successfully at Telenor the Norwegian telephone comp.any."
"The ODMG proposal has helped to focus the work on object-oriented databases (OODBs) onto a common object model and query language. Nevertheless there are several shortcomings of the current proposal stemming from the adaption of concepts of object-oriented programming and a lack of formalization. In this paper we present a formalization of the ODMG model and the OQL query language that is used in the CROQUE project as a basis for query optimization. An essential part is a complete, formally sound type system that allows us to reason about the types of intermediate query results and gives rise to fully orthogonal queries, including useful extensions of projections and set operations."
"This paper proposes a simple model for a timer-driven triggering and alerting system. Such a system can be used with relational and object-relational databases systems. Timer-driven trigger systems have a number of advantages over traditional trigger systems that test trigger conditions and run trigger actions in response to update events. They are relatively easy to implement since they can be built using a middleware program that simply runs SQL statements against a DBMS. Also, they can check certain types of conditions, such as ¡°a value did not change¡± or a ¡°a value did not change by more than 10% in six months.¡± Such conditions may be of interest for a particular application, but cannot be checked correctly by an event-driven trigger system. Also, users may be perfectly happy being notified once a day, once a week, or even less often of certain conditions, depending on their application. Timer triggers are appropriate for these users. The semantics of timer triggers are defined here using a simple procedure. Timer triggers are meant to complement event-driven triggers, not replace them. We challenge the database research community to developed alternate algorithms and optimizations for processing timer triggers, provided that the semantics are the same as when using the simple procedure presented here."
"We formulate this task as an inverse problem, specifying a well-defined cost function that has to be optimized under constraints. We show that our formulation includes the uniformity and independence assumptions as a special case, and that it can achieve better reconstruction results if we maximize the smoothness as opposed to the uniformity. In our experiments on real and synthetic datasets, the proposed method almost consistently outperforms its competitor, improving the rootmean-square error by up to 20 per cent for stock price data, and up to 90 per cent for smoother data sets."
"Classification and regression trees are machine©\learning methods for constructing prediction models from data. The models are obtained by recursively partitioning the data space and fitting a simple prediction model within each partition. As a result, the partitioning can be represented graphically as a decision tree. Classification trees are designed for dependent variables that take a finite number of unordered values, with prediction error measured in terms of misclassification cost. Regression trees are for dependent variables that take continuous or ordered discrete values, with prediction error typically measured by the squared difference between the observed and predicted values. This article gives an introduction to the subject by reviewing some widely available algorithms and comparing their capabilities, strengths, and weakness in two examples. ? 2011 John Wiley & Sons, Inc. WIREs Data Mining Knowl Discov 2011 1 14©\23 DOI: 10.1002/widm.8"
"It's a growing science, and I think that's part of its success. It has been able to grow and adapt as new inven- tions come along for accessing the data, or for joining the data in differ- ent ways. All of the relational database products have gone to a cost-based query optimization approach"
"It is envisaged that the application of the multilevel security (MLS) scheme will enhance flexibility and effectiveness of authorization policies in shared enterprise databases and will replace cumbersome authorization enforcement practices through complicated view definitions on a per user basis. However, as advances in this area are being made and ideas crystallized, the concomitant weaknesses of the MLS databases are also surfacing. We insist that the critical problem with the current model is that the belief at a higher security level is cluttered with irrelevant or inconsistent data as no mechanism for attenuation is supported. Critics also argue that it is imperative for MLS database users to theorize about the belief of others, perhaps at different security levels, an apparatus that is currently missing and the absence of which is seriously felt."
"Abstract.Data placement in shared-nothing database systems has been studied extensively in the past and various placement algorithms have been proposed. However, there is no consensus on the most efficient data placement algorithm and placement is still performed manually by a database administrator with periodic reorganization to correct mistakes. This paper presents the first comprehensive simulation study of data placement issues in a shared-nothing system. The results show that current hardware technology trends have significantly changed the performance tradeoffs considered in past studies. A simplistic data placement strategy based on the new results is developed and shown to perform well for a variety of workloads. "
From beginning of to the end of the IRO DB ESPRIT project has developed tools for accessing relational and object oriented databases in an integrated way The sys tem is based on the ODMG standard as pivot model and language It consists of three lay ers The local layer provides for an ODMG in terface to heterogeneous DBMSs the commu nication layer implements object oriented re mote data access and the interoperable layer supports design and querying of integrated views This paper describes the architecture and main design choices of IRO DB and re views them against the experiences gained with implementation and application It con cludes with analyzing the revisions and ex tensions needed for applying the developed technology to inter and intranet federations which are tackled in the follow up ESPRIT project MIRO Web
"Publisher Summary This chapter provides a comprehensive and cohesive overview of the key research results in the area of data stream query processing, both for SQL-like and XML query languages. Stream data are also generated naturally by web services, in which loosely coupled systems interact by exchanging high volumes of business data tagged in XML, forming continuous XML data streams. A central aspect of web services is the ability to efficiently operate on these XML data streams executing queries to continuously match, extract, and transform parts of the XML data stream to drive legacy back-end business applications. Manipulating stream data presents many technical challenges, which are just beginning to be addressed in the database, systems, algorithms, networking, and other computer science communities."
"In contrast to the conventional methodology of object-oriented program design focused on the interaction of objects, object-oriented database design should be based on the representation of objects. We put more emphasis in the application semantics pertinent to the structures of, relationships between, and constraints on objects than operations on the objects. Enhanced Entity-Relationship (EER) model is a convenient tool for representing these semantics. In this paper, I address the concept and methodology of using the EER model to design an object oriented database schema. The EER model facilitates the design of a logical schema that can be mapped to an object-oriented schema straightforward. An EER schema diagram is also a useful document that describes the logical database schema to other designers and users."
"Corporations worldwide are finding that understanding and managing rapidly growing, enterprisewide data is critical for making timely decisions and responding to changing business conditions. To manage and use business information competitively, many companies are establishing decision support systems built around a data warehouse of subject-oriented, integrated, historical information. In order to understand why the data warehouse must replace old legacy applications for effective information processing, it is necessary to understand the root causes of the difficulty in getting information in the first place. The first difficulty in getting information from the base of old applications is that those old applications were shaped around business requirements that were relevant as much as twenty-five years ago. These applications that were shaped yesterday do not reflect today¡¯s business. The second reason why older applications are so hard to use as a basis for information is that those applications were shaped around the clerical needs of the corporation. A clerically focused application of necessity does not have the historical foundation required to support a long-term view. Another reason why the clerical perspective of applications does not support management¡¯s need for information is that the clerical community focuses on detailed data. While detailed data is tine for the day-to-day clerical needs of the organization, management needs to see summary data in order to identify trends, challenges and opportunities. "
"The functionality of extensible database servers can be augmented by user-defined functions (UDFs). However, the server's security and stability are concerns whenever new code is incorporated. Recently, there has been interest in the use of Java for database extensibility. This raises several questions: Does Java solve the security problems? How does it affect efficiency?"
"Many current database systems use histograms to approximate the frequency distribution of values in the attributes of relations and based on them estimate query result sizes and access plan costs. In choosing among the various histograms, one has to balance between two conflicting goals: optimality, so that generated estimates have the least error, and practicality, so that histograms can be constructed and maintained efficiently. In this paper, we present both theoretical and experimental results on several issues related to this trade-off. Our overall conclusion is that the most effective approach is to focus on the class of histograms that accurately maintain the frequencies of a few attribute values and assume the uniform distribution for the rest, and choose for each relation the histogram in that class that is optimal for a self-join query."
"Continuous queries are persistent queries that allow users to receive new results when they become available. While continuous query systems can transform a passive web into an active environment, they need to be able to support millions of queries due to the scale of the Internet. No existing systems have achieved this level of scalability. NiagaraCQ addresses this problem by grouping continuous queries based on the observation that many web queries share similar structures. Grouped queries can share the common computation, tend to fit in memory and can reduce the I/O cost significantly. Furthermore, grouping on selection predicates can eliminate a large number of unnecessary query invocations. Our grouping technique is distinguished from previous group optimization approaches in the following ways. First, we use an incremental group optimization strategy with dynamic re-grouping. New queries are added to existing query groups, without having to regroup already installed queries. Second, we use a query-split scheme that requires minimal changes to a general-purpose query engine. Third, NiagaraCQ groups both change-based and timer-based queries in a uniform way. To insure that NiagaraCQ is scalable, we have also employed other techniques including incremental evaluation of continuous queries, use of both pull and push models for detecting heterogeneous data source changes, and memory caching. This paper presents the design of NiagaraCQ system and gives some experimental results on the system's performance and scalability."
"Full-text information retrieval systems have traditionally been designed for archival environments. They often provide little or no support for adding new documents to an existing document collection, requiring instead that the entire collection be re-indexed. Modern applications, such as information filtering, operate in dynamic environments that require frequent additions to document collections. We provide this ability using a traditional inverted file index built on top of a persistent object store. The data management facilities of the persistent object store are used to produce efficient incremental update of the inverted lists. We describe our system and present experimental results showing superior incremental indexing and competitive query processing performance."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
Inheritance hierarchies have become more and more complex according to an enlargement of object-oriented technology. One of the main problems is the effective searching in such hierarchies. More sophisticated algorithms are needed to searching in the data. In this article we present a novel approach to efficient searching in large inheritance hierarchies. The updatable approach employs the multi-dimensional data structures to indexing inheritance hierarchies and effective searching in the data.
"This paper examines the characteristics and challenges presented by medical databases and medical information systems. It begins with a survey of medical databases/information systems. This is followed by a list of challenges for database management systems generated by the needs of these systems. It concludes with a look at some systems which address these challenges. In the context of this background information, the database community is asked to consider whether the results of database research are reaching those who are making day-to-day decisions regarding design and implementation of medical information systems."
"The ESPRIT Project DWQ (Foundations of Data Warehouse Quality) aimed at improving the quality of DW design and operation through systematic enrichment of the semantic foundations of data warehousing. Logic-based knowledge representation and reasoning techniques were developed to control accuracy, consistency, and completeness via advanced conceptual modeling techniques for source integration, data reconciliation, and multi-dimensional aggregation. This is complemented by quantitative optimization techniques for view materialization, optimizing timeliness and responsiveness without losing the semantic advantages from the conceptual approach. At the operational level, query rewriting and materialization refreshment algorithms exploit the knowledge developed at design time. The demonstration shows the interplay of these tools under a shared metadata repository, based on an example extracted from an application at Telecom Italia."
"A WebView is a web page automatically created from base data typically stored in a DBMS. Given the multi-tiered architecture behind database-backed web servers, we have the option of materializing a WebView inside the DBMS, at the web server, or not at all, always computing it on the fly (virtual). Since WebViews must be up to date, materialized WebViews are immediately refreshed with every update on the base data. In this paper we compare the three materialization policies (materialized inside the DBMS, materialized at the web server and virtual) analytically, through a detailed cost model, and quantitatively, through extensive experiments on an implemented system. Our results indicate that materializing at the web server is a more scalable solution and can facilitate an order of magnitude more users than the virtual and materialized inside the DBMS policies, even under high update workloads."
"In the March 1994 issue of the ACM SIGMOD Record, Dr. Won Kim of UniSQL and the SIGMOD Chairperson published ¡°Observations on the ODMG-93 Proposal for Object-Oriented Database Language¡± (Volume 23, Number 1)."
"The result size of a query that involves multiple attributes from the same relation depends on these attributes¡¯joinr data distribution, i.e., the frequencies of all combinations of attribute values. To simplify the estimation of that size, most commercial systems make the artribute value independenceassumption and maintain statistics (typically histograms) on individual attributes only. In reality, this assumption is almost always wrong and the resulting estimations tend to be highly inaccurate. In this paper, we propose two main alternatives to effectively approximate (multi-dimensional) joint data distributions. (a) Using a multi-dimensional histogram, (b) Using the Singular Value Decomposition (SVD) technique from linear algebra. An extensive set of experiments demonstrates the advantages and disadvantages of the two approaches and the benefits of both compared to the independence assumption."
"The history of histograms is long and rich, full of detailed information in every step. It includes the course of histograms in different scientific fields, the successes and failures of histograms in approximating and compressing information, their adoption by industry, and solutions that have been given on a great variety of histogram-related problems. In this paper and in the same spirit of the histogram techniques themselves, we compress their entire history (including their ""future history"" as currently anticipated) in the given/fixed space budget, mostly recording details for the periods, events, and results with the highest (personally-biased) interest. In a limited set of experiments, the semantic distance between the compressed and the full form of the history was found relatively small!"
"One of the fundamental aspects of information and database systems is that they change. Moreover, in so doing they evolve, although the manner and quality of this evolution is highly dependent on the mechanisms in place to handle it. While changes in data are handled well, changes in other aspects, such as structure, rules, constraints, the model, etc., are handled to varying levels of sophistication and completeness."
"We present a method for efficiently performing deletions and updates of records when the records to be deleted or updated are chosen by a range scan on an index. The traditional method involves numerous unnecessary lock calls and traversals of the index from root to leaves, especially when the qualifying records' keys span more than one leaf page of the index. Customers have suffered performance losses from these inefficiencies and have complained about them. Our goal was to minimize the number of interactions with the lock manager, and the number of page fixes, comparison operations and, possibly, I/Os. Some of our improvements come from increased synergy between the query planning and data manager components of a DBMS. Our patented method has been implemented in DB2 V7 to address specific customer requirements. It has also been done to improve performance on the TPC-H benchmark."
"Mobile computing technology is developing rapidly due to the advantages of information access through mobile devices and the need to retrieve information at remote locations. However, many obstacles within the discipline of wireless computing are yet to be resolved. One of the most significant of these issues is the speed of data retrieval, which directly affects the performance of mobile database applications. To remedy this problem, we propose here a revised methodology focusing on the management of mobile transactions. This paper investigates an extended semantic-based transaction management mechanism, and applies a model-based approach for developing a simulation model to evaluate the performance of our approach."
"Data sharing in current P2P systems is very much restricted to file-system-like capabilities. In this paper, we present the strategies that we have adopted in our BestPeer project to support more fine-grained data sharing, especially, relational data sharing, in a P2P context. First, we look at some of the issues in designing a peer-based data management system, and discuss some possible solutions to address these issues. Second, we present the design of our first prototype system, PeerDB, and report our experience with it. Finally, we discuss our current extensions to PeerDB to support keyword-based queries."
"The current development of the Web and the generalization of XML technology provide a major opportunity which can radically change the face of the Web. Xyleme intends to be a leader of this revolution by providing database services over the XML data of the Web. Originally, Xyleme was a research project functioning as an open, loosely coupled network of researchers. At the end of 2000, a prototype had been implemented. A start-up company, also called Xyleme, is now turning into a product. The authors summarize the main research efforts of the Xyleme team. They concern: a scalable architecture; the efficient storage of huge quantities of XML data (hundreds of millions of pages); XML query processing with full-text and structural indexing; data acquisition strategies to build the repository and keep it up-to-date; change control with services such as query subscription; and semantic data integration to free users from having to deal with many specific DTDs when expressing queries."
"The advent of new database applications such as engineering design stresses the need for new functie nalities in database systems. It includes the management of multiple representations for database objects, long transactions as well as dynamic data structures. This paper presents the approach used in CADB, a prototype expert database system dedicated to CAD, for the management and control of the consistency of design objects. It concerns both the operations on the object property values and the interactive manipulation of their structure. They involve concepts of the object models as well as the application semantics. They rely therefore on concepts used for representing the design objects and on semantic notions related to expert knowledge in the application domain. Among these are the notions of consistency and of completeness of the objects. These two complementary aspects are detailed and their relationships described. The emphasis is on the heuristic rules that provide a unified knowledge-based approach for their management independent of the particular application being considered. Dynamic inheritance mechanisms are also presented that sup port the manipulations performed on the object structures. It is shown how they help providing expert database facilities. "
"Many Web applications are based on dynamic interactions between Web components exchanging flows of information. Such a situation arises for instance in mashup systems or when monitoring distributed autonomous systems. Our work is in this challenging context that has generated recently a lot of attention; see Web 2.0. We introduce the axlog formal model for capturing such interactions and show how this model can be supported efficiently. The central component is the axlog widget defined by one tree-pattern query or more, over an active document (in the Active XML style) that includes some input streams of updates. A widget generates a stream of updates for each query, the updates that are needed to maintain the view corresponding to the query. We exploit an array of known technologies: datalog optimization techniques such as Differential or MagicSet, constraint query languages, and efficient XML filtering (YFilter). The novel optimization technique we propose is based on fundamental new notions: a relevance (different than that of MagicSet), satisfiability and provenance for active documents. We briefly discuss an implementation of an axlog engine, an application that we used to test the approach, and results of experiments."
"Information becomes a more and more valuable asset in today¡¯s organizations. Therefore the need of creating an integrated view over all available data sources arises. Several technical problems must be overcome in the design and implementation of a system for integrating different data sources. To the main obstacles count autonomy, data heterogeneity and different query capabilities of the repositories. This thesis presents the data integration system AMOS II , which is based on the wrapper-mediator approach. The main focus of this work lies on data model transformation and query processing. The following extensions to the AMOS II system are described in this thesis: ? A framework for transforming various data models into the objectoriented model of AMOS II is presented. ? The roles and tasks of wrappers are described. In particular their participation in query processing and query optimization is discussed. ? A way for describing and utilizing the query capabilities of the different data sources is proposed. ? Two different approaches to query processing over external data sources are developed and analyzed. All the proposed techniques are implemented in the AMOS II system, which runs on a Windows NT platform."
"The database research community is rightly proud of success in basic research, and its remarkable record of technology transfer. Now the field needs to radically broaden its research focus to attack the issues of capturing, storing, analyzing, and presenting the vast array of online data. The database research community should embrace a broader research agenda ¡ª broadening the definition of database management to embrace all the content of the Web and other online data stores, and rethinking our fundamental assumptions in light of technology shifts. To accelerate this transition, we recommend changing the way research results are evaluated and presented. In particular, we advocate encouraging more speculative and long-range work, moving conferences to a poster format, and publishing all research literature on the Web."
"Classification of large datasets is an important data mining problem. Many classification algorithms have been proposed in the literature, but studies have shown that so far no algorithm uniformly outperforms all other algorithms in terms of quality. In this paper, we present a unifying framework called Rain Forest for classification tree construction that separates the scalability aspects of algorithms for constructing a tree from the central features that determine the quality of the tree. The generic algorithm is easy to instantiate with specific split selection methods from the literature (including C4.5, CART, CHAID, FACT, ID3 and extensions, SLIQ, SPRINT and QUEST).In addition to its generality, in that it yields scalable versions of a wide range of classification algorithms, our approach also offers performance improvements of over a factor of three over the SPRINT algorithm, the fastest scalable classification algorithm proposed previously. In contrast to SPRINT, however, our generic algorithm requires a certain minimum amount of main memory, proportional to the set of distinct values in a column of the input relation. Given current main memory costs, this requirement is readily met in most if not all workloads."
"One of the challenging aspects of scientific data repositories is how to efficiently explore the catalogues that describe the data. We have encountered such a problem while developing HEDC, HESSI Experimental data center, a multi-terabyte repository built for the recently launched HESSI satellite. In HEDC, scientific users will soon be confronted with a catalogue of many million tuples. In this paper we present a novel technique that allows users to efficiently explore such a large data space in an interactive manner. Our approach is to store a copy of relevant fields in segmented and wavelet encoded views that are streamed to specialized clients. These clients use approximated data and adaptive decoding techniques to allow users to quickly visualize the search space. In the paper we describe how this approach reduces from hours to seconds the time needed to generate meaningful visualizations of millions of tuples."
"We propose a new client-side data-caching scheme for relational databases with a central server and multiple clients. Data are loaded into each client cache based on queries executed on the central database at the server. These queries are used to form predicates that describe the cache contents. A subsequent query at the client may be satisfied in its local cache if we can determine that the query result is entirely contained in the cache. This issue is called  cache completeness . A separate issue,  cache currency , deals with the effect on client caches of updates committed at the central database. We examine the various performance tradeoffs and optimization issues involved in addressing the questions of cache currency and completeness using predicate descriptions and suggest solutions that promote good dynamic behavior. Lower query-response times, reduced message traffic, higher server throughput, and better scalability are some of the expected benefits of our approach over commonly used relational server-side and object ID-based or page-based client-side caching."
"There is currently considerable interest in developing multimedia digital libraries. However, it has become clear that existing architectures for management systems do not support the particular requirements of continuous media types. This is particularly the case in the important area of quality of service support. In this correspondence, we discuss quality of service issues within digital libraries and present a reference architecture able to support some quality aspects."
"In this paper we argue for using a ""Game First"" approach to teaching introductory programming. We believe that concerns over whether an OO approach or a procedural approach should be used first are secondary to the course assignment and example content. If examples are not compelling, student interest often lags thus making the OO versus procedural argument moot. We believe that game programming motivates most new programmers. Compelling assignments mean that students are far more likely to learn because they are interested, and the visual component allows students to see mistakes in their code as manifested in the resultant graphics. We describe our experiences after redesigning and offering a new introductory computer science sequence using 2D game development as a unifying theme. We teach fundamental programming concepts via two dimensional game development in Flash and ActionScript during the first quarter, transition to C++ to solidify concepts and add pointers during the second quarter, then teach a multi-phase project based game approach using C++ and openGL (2D graphics only) during the third quarter. Our surveys show that this approach improved student understanding of all seven basic topics examined."
"A repository is a shared database of information about engineered artifacts. We define a repository manager to be a database application that suPports checkout/checkin, version and configuration management, notification, context management, and workflow control. Since the main value of a repository is in the tools that use it, we discuss technical issues of integrating tools with repositories. We also discuss how to implement a repository manager by layering it on a DBMS, focusing especially on issues of programming interface, performance, distribu,; tion, and interoperability."
"Complex queries containing outer joins are, for the most part, executed by commercial DBMS products in an ""as written"" manner. Only a very few reorderings of the operations are considered and the benefits of considering comprehensive reordering schemes are not exploited. This is largely due to the fact there are no readily usable results for reordering such operations for relations with duplicates and/or outer join predicates that are other than ""simple."" Most previous approaches have ignored duplicates and complex predicates; the very few that have considered these aspects have suggested approaches that lead to a possibly exponential number of, and redundant intermediate joins. Since traditional query graph models are inadequate for modeling outer join queries with complex predicates, we present the needed hypergraph abstraction and algorithms for reordering such queries with joins and outer joins. As a result, the query optimizer can explore a significantly larger space of execution plans, and choose one with a low cost. Further, these algorithms are easily incorporated into well known and widely used enumeration methods such as dynamic programming."
"The integration of knowledge for multiple sources is an important aspect of automated reasoning systems. When different knowledge bases are used to store knowledge provided by multiple sources, we are faced with the problem of integrating multiple knowledge bases: Under these circumstances, we are also confronted with the prospect of inconsistency. In this paper we present a uniform theoretical framework, based on annotated logics, for amalgamating multiple knowledge bases when these knowledge bases (possibly) contain inconsistencies, uncertainties, and nonmonotonic modes of negation. We show that annotated logics may be used, with some modifications, to mediate between different knowledge bases. The multiple knowledge bases are amalgamated by a transformation of the individual knowledge bases into new annotated logic programs, together with the addition of a new axiom scheme. We characterize the declarative semantics of such amalgamated knowledge bases and study how the semantics of the amalgam is related to the semantics of the individual knowledge bases being combined.¡ªAuthor's Abstract"
"Abstract. In this paper we present a mechanism for approximately translating Boolean query constraints across heterogeneous information sources. Achieving the best translation is challenging because sources support different constraints for formulating queries, and often these constraints cannot be precisely translated. For instance, a query [score>8] might be ¡°perfectly¡± translated as [rating>0.8] at some site, but can only be approximated as [grade=A] at another. Unlike other work, our general framework adopts a customizable ¡°closeness¡± metric for the translation that combines both precision and recall. Our results show that for query translation we need to handle interdependencies among both query conjuncts as well as disjuncts. As the basis, we identify the essential requirements of a rule system for users to encode the mappings for atomic semantic units. Our algorithm then translates complex queries by rewriting them in terms of the semantic units. We show that, under practical assumptions, our algorithm generates the best approximate translations with respect to the closeness metric of choice. We also present a case study to show how our technique may be applied in practice."
"Often many records in a database share similar values for several attributes. If one is able to identify and group these records together that share similar values for some ¡ª even if not all ¡ª attributes, not only does one have the possibility of a more parsimonious representation of the data, but one may also gain useful insight into the data from an analysis and mining perspective. In this thesis, we introduce the notion of fascicles. A fascicle F(k,t) is a subset of records that have k compact attributes. An attribute A of a collection F of records is compact if the width of the range of A-values (for numeric attributes) or the number of distinct A-values (for categorical attributes) of all the records in F does not exceed t. We introduce and study two problems related to fascicles. First, we consider how to find fascicles such that the total storage of the relation is minimized. Second, we study how best to extract fascicles whose sizes exceed a given minimum threshold and that represent patterns of maximal quality, where quality is measured by the pair (k,t). We develop algorithms to attack both of the above problems. We show that these two problems are very hard to solve optimally. But we demonstrate empirically that good solutions can be obtained using our algorithms."
"Smartcards are the most secure portable computing device today. They have been used successfully in applications involving money, and proprietary and personal data (such as banking, healthcare, insurance, etc.). As smartcards get more powerful (with 32-bit CPU and more than 1 MB of stable memory in the next versions) and become multi-application, the need for database management arises. However, smartcards have severe hardware limitations (very slow write, very little RAM, constrained stable memory, no autonomy, etc.) which make traditional database technology irrelevant. The major problem is scaling down database techniques so they perform well under these limitations. In this paper, we give an in-depth analysis of this problem and propose a PicoDBMS solution based on highly compact data structures, query execution without RAM, and specific techniques for atomicity and durability. We show the effectiveness of our techniques through performance evaluation."
"Multi-level transactions are a varlant of open-nested transactions in which the subtransactions correspond to operations at different levels of a layered system architecture. They allow the exploitation of semantics of high-level operations to increase concurrency. As a consequence, undoing a transaction requires compensation of completed subtransactions. In addition, multi-level recovery methods must take into consideration that high-level operations are not necessarily atomic if multiple pages are updated in a single subtransaction. This article presents algorithms for multi-level transaction management that are implemented in the database kernel system (DASDBS). In particular, we show that multi-level recovery can be implemented in an efficient way. We discuss performance measurements using a synthetic benchmark for processing complex objects in a multi-user environment. We show that multi-level transaction management can be extended easily to cope with parallel subtransactions within a single transaction. Performance results are presented with varying degrees of inter- and intratransaction parallelism."
"Current client-server object database management systems employ either a page server or an object server architecture. Both of these architectures have their respective strengths, but they also have key drawbacks for important system and workload configurations. We propose a new hybrid server architecture which combines the best features of both page server and object server architectures while avoiding their problems. The new architecture incorporates new or adapted versions of data transfer, recovery, and cache consistency algorithms; in this paper we focus only on the data transfer and recovery issues. The data transfer mechanism allows the hybrid server to dynamically behave as both page and object server. The performance comparison of the hybrid server with object and page servers indicates that the performance of the hybrid server is more robust than the others."
"To meet the needs of many real-world control applications, concepts from Temporal, Real-Time, and Active Databases must be integrated:"
"We present incremental view maintenance algorithms for a data warehouse derived from multiple distributed autonomous data sources. We begin with a detailed framework for analyzing view maintenance algorithms for multiple data sources with concurrent updates. Earlier approaches for view maintenance in the presence of concurrent updates typically require two types of messages: one to compute the view change due to the initial update and the other to compensate the view change due to interfering concurrent updates. The algorithms developed in this paper instead perform the compensation locally by using the information that is already available at the data warehouse. The first algorithm, termed SWEEP, ensures complete consistency of the view at the data warehouse in the presence of concurrent updates. Previous algorithms for incremental view maintenance either required a quiescent state at the data warehouse or required an exponential number of messages in terms of the data sources. In contrast, this algorithm does not require that the data warehouse be in a quiescent state for incorporating the new views and also the message complexity is linear in the number of data sources. The second algorithm, termed Nested SWEEP, attempts to compute a composite view change for multiple updates that occur concurrently while maintaining strong consistency."
"Data mining is supposed to be an iterative and exploratory process. In this context, we are working on a project with the overall objective of developing a practical computing environment for the human-centered exploratory mining of frequent sets. One critical component of such an environment is the support for the dynamic mining of constrained frequent sets of items. Constraints enable users to impose a certain focus on the mining process; dynamic means that, in the middle of the computation, users are able to (i) change (such as tighten or relax) the constraints and/or (ii) change the minimum support threshold, thus having a decisive influence on subsequent computations. In a real-life situation, the available buffer space may be limited, thus adding another complication to the problem.In this article, we develop an algorithm, called DCF, for Dynamic Constrained Frequent-set computation. This algorithm is enhanced with a few optimizations, exploiting a lightweight structure called a segment support map. It enables DCF to (i) obtain sharper bounds on the support of sets of items, and to (ii) better exploit properties of constraints. Furthermore, when handling dynamic changes to constraints, DCF relies on the concept of a delta member generating function, which generates precisely the sets of items that satisfy the new but not the old constraints. Our experimental results show the effectiveness of these enhancements."
"We show that adaptive agents on the Internet can learn to exploit bidding agents who use a (limited) number of fixed strategies. These learning agents can be generated by adapting a special kind of finite automata with evolutionary algorithms (EAs). Our approach is especially powerful if the adaptive agent participates in frequently occurring micro-transactions, where there is sufficient opportunity for the agent to learn online from past negotiations. More in general, results presented in this paper provide a solid basis for the further development of adaptive agents for Internet applications."
"In order to access information from a variety of heterogeneous information sources, one has to be able to translate queries and data from one data model into another. This functionality is provided by so-called (source) wrappers [4,8] which convert queries into one or more commands/queries understandable by the underlying source and transform the native results into a format understood by the application. As part of the TSIMMIS project [1, 6] we have developed hard-coded wrappers for a variety of sources (e.g., Sybase DBMS, WWW pages, etc.) including legacy systems (Folio). However, anyone who has built a wrapper before can attest that a lot of effort goes into developing and writing such a wrapper. In situations where it is important or desirable to gain access to new sources quickly, this is a major drawback. Furthermore, we have also observed that only a relatively small part of the code deals with the specific access details of the source. The rest of the code is either common among wrappers or implements query and data transformation that could be expressed in a high level, declarative fashion."
"Multidimensional discrete data (MDD) i.e., arrays of arbitrary size, dimension, and base type appear in a variety of business, technical, and scientific application fields. RasDaMan is an effort to give comprehensive domain-independent MDD database support. Based on a formal algebraic array model, RasDaMan offers declarative array operators embedded in standard SQL; key DBMS components are an MDD query optimizer and a streamlined storage manager for efficient access to subsets of huge arrays. We present the RasDaMan approach to MDD management based on the medical and geographic application fields addressed in the project."
The Capability Maturity Model [4] is an orderly way for organizations to determine the capabilities of their current processes for developing software and to establish priorities for improvement [2]. It defines five levels of progressively more mature process capability [3].
"XML employs a tree-structured data model, and, naturally, XML queries specify patterns of selection predicates on multiple elements related by a tree structure. Finding all occurrences of such a twig pattern in an XML database is a core operation for XML query processing. Prior work has typically decomposed the twig pattern into binary structural (parent-child and ancestor-descendant) relationships, and twig matching is achieved by: (i) using structural join algorithms to match the binary relationships against the XML database, and (ii) stitching together these basic matches. A limitation of this approach for matching twig patterns is that intermediate result sizes can get large, even when the input and output sizes are more manageable.In this paper, we propose a novel holistic twig join algorithm, TwigStack, for matching an XML query twig pattern. Our technique uses a chain of linked stacks to compactly represent partial results to root-to-leaf query paths, which are then composed to obtain matches for the twig pattern. When the twig pattern uses only ancestor-descendant relationships between elements, TwigStack is I/O and CPU optimal among all sequential algorithms that read the entire input: it is linear in the sum of sizes of the input lists and the final result list, but independent of the sizes of intermediate results. We then show how to use (a modification of) B-trees, along with TwigStack, to match query twig patterns in sub-linear time. Finally, we complement our analysis with experimental results on a range of real and synthetic data, and query twig patterns."
"Materialized views (or Automatic Summary Tables¡ªASTs) are commonly used to improve the performance of aggregation queries by orders of magnitude. In contrast to regular tables, ASTs are synchronized by the database system. In this paper, we present techniques for maintaining cube ASTs. Our implementation is based on IBM DB2 UDB."
"Currently, the Internet provides access to a very large number and wide variety of information sources (e.g., textual databases, sites containing technical reports, directory listings), and systems to access these sources (e.g., World Wide Web, Gopher, WAIS). The challenge is to provide easy, efficient, robust and secure access to this information and other kinds (e.g., relational and object oriented databases). This aim of this panel is to explore whether there are any new technical problems, relevant to the Database field, that need to be solved in order to realize such global information systems. In particular, we debate whether existing techniques from database systems (e.g., multidatabases and distributed databases) can be applied or straigtitforwardly extended to global information systems. Furthermore, we attempt to establish realistic goals for database technologies in global information systems. Some of the specific issues discussed are the following:"
"The DARPA Intelligent Integration of Information (I3) effort is based on the assumption that systems can easily exchange data. However, as a consequence of the rapid development of research, and prototype implementations, in this area, the initial outcome of this program appears to have been to produce a new set of systems. While they can perform certain advanced information integration tasks, they cannot easily communicate with each other.With a view to understanding and solving this problem, there was a group discussion at the DARPA Intelligent Integration of Information/Persistent Object Bases (I3/POB) meeting in San Diego, in January, 1996; and a further workshop was held on this topic at the University of Maryland in April, 1996. The list of participants is in Appendix A. The idea emerging from these meeting a was not to force all systems to communicate according to specified standards, but to agree on the following:&bull; A minimal core language, or Level 1 option, which would be a restriction of the object-oriented query language OQL, such that it will accept queries for relational databases. We recommend that all system components be able, at a minimum, to accept queries in this syntax, provided they address concepts (e.g., relations or classes, attributes or instance variables) known to that component. There must be a simple protocol to determine the schema of a system (its set of supported concepts).&bull; A simple format for representing answers. This could also be a fragment of OQL and will be included in the core language specification.&bull; A set of extensions, one of which could be full OQL, and would handle complex structures and abstract types (with methods). Other extensions will be needed to support rules (e.g., definitions of terms that can be shared among components), semistructured data (for self-describing objects), and shared code. A system component could support one or more of these extensions, independently, and there should be some simple protocol to determine the particular extensions that are supported."
"The goal of this demonstration is to present the main features of (i) Axielle, an XML repository developed by Ardent Software [3] on top of the O2 object-oriented DBMS and (ii) the ActiveView system which has been built by the Verso project at INRIA [1] on top of Axielle. The demonstration is based on a simple electronic commerce application which will be described in Section 2. Electronic commerce is emerging as a major Web-supported application. It involves handling and exchange of data (e.g. product catalogs, yellow pages, etc.) and must provide (i) database functionalities (query language, transactions, concurrency control, distribution and recovery) for the efficient management of large data volumes and hundreds of users as well as (ii) standard data storage and exchange formats (e.g. XML, SGML) for the easy integration of existing software and data. The ActiveView system combined with the Axielle XML repository enables a fast deployment of electronic commerce applications based on a new high-level declarative specification language (AVL), advanced database technology (object-oriented data model, XML query language, notifications), Web standards (HTTP, HTML) and other Internet compliant"
"To resolve the syntax, structure and semantic heterogeneity for sharing information resources, the representative technologies are XML and Metadata. XML is used to represent the syntax and structure of information resources but the various XML schema definitions that have been developed by independent organizations without any standards or guidelines, make it difficult to share the semantic meaning of XML encoded information resources. In this paper, we propose a mechanism, named MSDL that represents the exact meaning of XML tags by describing the structural and semantic differences with standard metadata in metadata registries. MSDL overcomes the limitations of other approaches with respect to exactness, flexibility and standardization, and provides an environment for business partners using different metadata to share their XML encoded information resources."
"We describe an algorithm for estimating the number of page fetches for a partial or complete scan of a B-tree index. The algorithm obtains estimates for the number of page fetches for an index scan when given the number of tuples selected and the number of LRU buffers currently available. The algorithm has an initial phase that is performed exactly once before any estimates are calculated. This initial phase, involving LRU buffer modeling, requires a scan of all the index entries and calculates the number of page fetches for different buffer sizes. An approximate empirical model is obtained from this data. Subsequently, an inexpensive estimation procedure is called by the query optimizer whenever it needs an estimate of the page fetches for the index scan. This procedure utilizes the empirical model obtained in the initial phase."
"This paper presents an algorithm, called ARIES/CSA (Algorithm for Recovery and Isolation Exploiting Semantics for Client-Server Architectures), for performing recovery correctly in client-server (CS) architectures. In CS, the server manages the disk version of the database. The clients, after obtaining database pages from the server, cache them in their buffer pools. Clients perform their updates on the cached pages and produce log records. The log records are buffered locally in virtual storage and later sent to the single log at the server. ARIES/CSA supports a write-ahead logging (WAL), fine-granularity (e.g., record) locking, partial rollbacks and flexible buffer management policies like steal and no-force. It does not require   that the clocks on the clients and the server be synchronized. Checkpointing by the server and the clients allows for flexible and easier recovery."
"Several object-oriented database management systems have been implemented without an accompanying theoretical foundation for constraint, query specification, and processing. The pattern-based object calculus presented in this article provides such a theoretical foundation for describing and processing object-oriented databases. We view an object-oriented database as a network of interrelated classes (i.e., the intension) and a collection of time-varying object association patterns (i.e., the extension). The object calculus is based on first-order logic. It provides the formalism for interpreting precisely and uniformly the semantics of queries and integrity constraints in object-oriented databases. The power of the object calculus is shown in four aspects. First, associations among objects are expressed explicitly in an object-oriented database. Second, the ""nonassociation"" operator is included in the object calculus. Third, set-oriented operations can be performed on both homogeneous and heterogeneous object association patterns. Fourth, our approach does not assume a specific form of database schema. A proposed formalism is also applied to the design of high-level object-oriented query and constraint languages."
"The Joumal is a quarterly puUication of the VLDB Endowment. As a database systems journal it is dedicated to the intemational publication of scholarly contributions to the advancement of information system architectures, the impact of emerging technologies on information systems, and the development of novel applications. It presents significant advances in the design, implementation, and evaluation of systems for databases and for other information collections Its scope ranges from the development of special-purpose hardware, the design of innovative software approaches, integrated system architectures, the design analysis and performance evaluation of systems to new techniques for presenting and capturing information.  "
"In July of this year, the American and International committees responsible for the SQL standard finalized the specification for new binding style called the Call Level Interface (SQL/CLI)[2]. This new binding style is an addendum to the existing SQL Standard [1], and"
"A point data retrieval algorithm for the HG-tree is introduced which improves the number of nodes accessed. The HG-tree is a multidimensional indexing tree designed for point data and it is a simple modification from the Hilbert R-tree for indexing spatial data. The HG-tree data search method mainly makes use of the Hilbert index values to search for exact data, instead of using conventional point search methods as used in most of the R-tree papers. The use of Hilbert curve values and MBR can reduce the spatial cover of an MBR."
"One of the main tasks of mediators is to fuse information from heterogeneous information sources. This may involve, for example, removing redundancies, and resolving inconsistencies in favor of the most reliable source. The problem becomes harder when the sources are unstructured/semistructured and we do not have complete knowledge of their contents and structure. In this paper we show how many common fusion operations can be specified non-procedurally and succinctly. The key to our approach is to assign semantically meaningful object ids to objects as they are ¡°imported¡± into the mediator. These semantic ids can then be used to specify how various objects are combined or merged into objects ¡°exported¡± by the mediator. In this paper we also discuss the implementation of a mediation system based on these principles. In particular, we present key optimization techniques that significantly reduce the processing costs associated with information fusion."
"Publisher Summary The ServiceGlobe system provides a platform on which e-services (also called services or Web services) can be implemented, stored, published, discovered, deployed, and dynamically invoked at arbitrary Internet servers participating in the ServiceGlobe federation. The next generation of Internet applications¡ªe-services¡ªis emerging. By an e-service, one understands an autonomous software component that is uniquely identified by a Unique Resource Identifier (URI) and that can be accessed by using standard Internet protocols like eXtensible Markup Language (XML), SOAP, or Hypertext Transfer Protocol (HTTP). An e-service may combine several applications that a user needs, such as the different pieces of a supply chain architecture. For the end-user, however, the entire infrastructure will appear as a single application. Due to its potential of changing the Internet to a platform of application collaboration and integration, e-service technology gains more and more attention in research and industry; initiatives such as HP Web Services Platform [WSP], Sun ONE [Sun], or Microsoft .NET [NET] show this development."
"Deterministic testing of SQL database systems is human intensive and cannot adequately cover the SQL input domain. A system (RAGS), was built to stochastically generate valid SQL statements 1 million times faster than a human and execute them. 1 Testing SQL is Hard Good test coverage for commercial SQL database systems is very hard. The input domain, all SQL statements, from any number of users, combined with all states of the database, is gigantic. It is also difficult to verify output for positive tests because the semantics of SQL are complicated.¡¯ Software engineering technology exists to predictably improve quality ([Bei90] for example). The techniques involve a software development process including unit tests and final system validation tests (to verify the absence of bugs). This process requires a substantial investment so commercial SQL vendors with tight schedules tend to use a more ad hoc process. The most popular method¡¯ is rapid development followed by test-repair cycles. SQL test groups focus on deterministic testing to cover individual features of the language. Typical SQL test libraries contain tens of thousands of statements and require an estimated % person-hour per statement to compose. These test libraries cover an important, but tiny, fraction of the SQL input domain. Large increases in test coverage must come from automating the generation of tests. This paper describes a method to rapidly create a very large number of SQL statements without human intervention. The SQL statements are generated stochastically (or ¡®randomly¡¯) which provides the speed as well as wider coverage of the input domain. The challenge is to SQL testing procedures and bug counts are proprietary so there is little public information. 618 distribute the SQL statements in useful regions of the input domain. If the distribution is adequate, stochastic testing has the advantage that the quality of the tests improves as the test size increases. A system called RAGS (Random Generation of SQL) was built to explore automated testing. RAGS is currently used by the Microsoft SQL Server [MSS98] testing group. This paper describes RAGS and some illustrative test results. Figure 1 illustrates the test coverage problem. Customers use the hexagon, bugs are in the oval, and the test libraries cover the shaded circle."
"We present a pattern-mining algorithm that scales roughly linearly in the number of maximal patterns embedded in a database irrespective of the length of the longest pattern. In comparison, previous algorithms based on Apriori scale exponentially with longest pattern length. Experiments on real data show that when the patterns are long, our algorithm is more efficient by an order of magnitude or more."
"Over the last few years, the information technology industry has witnessed revolutions in multiple dimensions. Increasing ubiquitous sources of data have posed two connected challenges to data management solutions -- processing unprecedented volumes of data, and providing ad-hoc real-time analysis in mainstream production data stores without compromising regular transactional workload performance. In parallel, computer hardware systems are scaling out elastically, scaling up in the number of processors and cores, and increasing main memory capacity extensively. The data processing challenges combined with the rapid advancement of hardware systems has necessitated the evolution of a new breed of main-memory databases optimized for mixed OLTAP environments and designed to scale.    The Oracle RDBMS In-memory Option (DBIM) is an industry-first distributed dual format architecture that allows a database object to be stored in columnar format in main memory highly optimized to break performance barriers in analytic query workloads, simultaneously maintaining transactional consistency with the corresponding OLTP optimized row-major format persisted in storage and accessed through database buffer cache. In this paper, we present the distributed, highly-available, and fault-tolerant architecture of the Oracle DBIM that enables the RDBMS to transparently scale out in a database cluster, both in terms of memory capacity and query processing throughput. We believe that the architecture is unique among all mainstream in-memory databases. It allows complete application-transparent, extremely scalable and automated distribution of Oracle RDBMS objects in-memory across a cluster, as well as across multiple NUMA nodes within a single server. It seamlessly provides distribution awareness to the Oracle SQL execution framework through affinitized fault-tolerant parallel execution within and across servers without explicit optimizer plan changes or query rewrites."
"A common query against large protein and gene sequence data sets is to locate targets that are similar to an input query sequence. The current set of popular search tools, such as BLAST, employ heuristics to improve the speed of such searches. However, such heuristics can sometimes miss targets, which in many cases is undesirable. The alternative to BLAST is to use an accurate algorithm, such as the Smith-Waterman (S-W) algorithm. However, these accurate algorithms are computationally very expensive, which limits their use in practice. This paper takes on the challenge of designing an accurate and efficient algorithm for evaluating local-alignment searches."
"Efficient algorithms for incrementally computing nested query expressions do not exist. Nested query expressions are query expressions in which selection/join predicates contain subqueries. In order to respond to this problem, we propose a two-step strategy for incrementaly computing nested query expressions. In step (1), the query expression is transformed into an equivalent unnested flat query expression. In step (2), the flat query expression is incrementally computed. To support step (1), we have developed a very concise algebra-to-algebra transformation algorithm, and we have formally proved its correctness. The flat query expressions resulting from the transformation make intensive use of the relational set-difference operator. To support step (2), we present and analyze an efficient algorithm for incrementally computing set differences based on view pointer caches. When combined with existing incremental algorithms for SPJ queries, our incremental set-difference algorithm can be used to compute the unnested flat query expressions efficiently. It is important to notice that without our incremental set-difference algorithm the existing incremental algorithms for SPJ queries are useless for any query involving the set-difference operator, including queries that are not the result of unnesting nested queries."
"The coming years will witness dramatic advances in wireless communications as well as positioning technologies. As a result, tracking the changing positions of objects capable of continuous movement is becoming increasingly feasible and necessary. The present paper proposes a novel, R*-tree based indexing technique that supports the efficient querying of the current and projected future positions of such moving objects. The technique is capable of indexing objects moving in one-, two-, and three-dimensional space. Update algorithms enable the index to accommodate a dynamic data set, where objects may appear and disappear, and where changes occur in the anticipated positions of existing objects. A comprehensive performance study is reported."
"Although there have been many studies on data mining, to date there have been few research prototypes or commercial systems supporting comprehensive query-driven mining, which encourages interactive exploration of the data. Our thesis is that constraint constructs and the optimization they induce play a pivotal role in mining queries, thus substantially enhancing the usefulness and performance of the mining system. This is based on the analogy of declarative query languages like SQL and query optimization which have made relational databases so successful. To this end, our proposed demo is not yet another data mining system, but of a new paradigm in data mining - mining with constraints, as the important first step towards supporting ad-hoc mining in DBMS."
"There are a number of data manipulation requirements common to most decision support (DSS) systems; these requirements are currently being addressed through the use of sophisticated decision support engines working in conjunction with the RDBMS. Since RDBMSS are the preferred data storage layer for DSS, there is an opportunity to provide many of the most frequent data manipulation requirements within the database. Recommendations on how decision support functionality should be partitioned between the RDBMS engine and the DSS application will be presented."
"In this paper we present a mechanism for translating constraint queries, i.e., Boolean expressions of constraints, across heterogeneous information sources. Integrating such systems is difficult in part because they use a wide range of constraints as the vocabulary for formulating queries. We describe algorithms that apply user-provided mapping rules to translate query constraints into ones that are understood and supported in another context, e.g., that use the proper operators and value formats. We show that the translated queries minimally subsume the original ones. Furthermore, the translated queries are also the most compact possible. Unlike other query mapping work, we effectively consider inter-dependencies among constraints, i.e., we handle constraints that cannot be translated independently. Furthermore, when constraints are not fully supported, our framework explores relaxations (semantic rewritings) into the closest supported version. Our most sophisticated algorithm (Algorithm TDQM) does not blindly convert queries to DNF (which would be easier to translate, but expensive); instead it performs a top-down mapping of a query tree, and does local query structure conversion only when necessary."
"Many commercial database systems maintain histograms to summarize the contents of large relations and permit efficient estimation of query result sizes for use in query optimizers. Delaying the propagation of database updates to the histogram often introduces errors into the estimation. This article presents new sampling-based approaches for incremental maintenance of approximate histograms. By scheduling updates to the histogram based on the updates to the database, our techniques are the first to maintain histograms effectively up to date at all times and avoid computing overheads when unnecessary. Our techniques provide highly accurate approximate histograms belonging to the equidepth and Compressed classes. Experimental results show that our new approaches provide orders of magnitude more accurate estimation than previous approaches.An important aspect employed by these new approaches is a backing sample, an up-to-date random sample of the tuples currently in a relation. We provide efficient solutions for maintaining a uniformly random sample of a relation in the presence of updates to the relation. The backing sample techniques can be used for any other application that relies on random samples of data."
"In this paper, we present a unified formalism, based on Past Temporal Logic, for specifying conditions and events in the rules for active database system. This language permits specification of many time varying properties of database systems. It also permits specification of temporal aggregates. We present an efficient incremental algorithm for detecting conditions specified in this language. The given algorithm, for a subclass of the logic, was implemented on top of Sybase."
"Much has been written about the explosion of data, also known as the ¡°data deluge¡±. Similarly, much of today's research and decision making are based on the de facto acceptance that knowledge and insight can be gained from analyzing and contextualizing the vast (and growing) amount of ¡°open¡± or ¡°raw¡± data. The concept that the large number of data sources available today facilitates analyses on combinations of heterogeneous information that would not be achievable via ¡°siloed¡± data maintained in warehouses is very powerful. The term data lake has been coined to convey the concept of a centralized repository containing virtually inexhaustible amounts of raw (or minimally curated) data that is readily made available anytime to anyone authorized to perform analytical activities. The often unstated premise of a data lake is that it relieves users from dealing with data acquisition and maintenance issues, and guarantees fast access to local, accurate and updated data without incurring development costs (in terms of time and money) typically associated with structured data warehouses. However appealing this premise, practically speaking, it is our experience, and that of our customers, that ¡°raw¡± data is logistically difficult to obtain, quite challenging to interpret and describe, and tedious to maintain. Furthermore, these challenges multiply as the number of sources grows, thus increasing the need to thoroughly describe and curate the data in order to make it consumable. In this paper, we present and describe some of the challenges inherent in creating, filling, maintaining, and governing a data lake, a set of processes that collectively define the actions of data wrangling, and we propose that what is really needed is a curated data lake, where the lake contents have undergone a curation process that enable its use and deliver the promise of ad-hoc data accessibility to users beyond the enterprise IT staff."
"In this paper, we present a new multimedia retrieval paradigm to innovate large-scale search of heterogenous multimedia data. It is able to return results of different media types from heterogeneous data sources, e.g., using a query image to retrieve relevant text documents or images from different data sources. This utilizes the widely available data from different sources and caters for the current users' demand of receiving a result list simultaneously containing multiple types of data to obtain a comprehensive understanding of the query's results. To enable large-scale inter-media retrieval, we propose a novel inter-media hashing (IMH) model to explore the correlations among multiple media types from different data sources and tackle the scalability issue. To this end, multimedia data from heterogeneous data sources are transformed into a common Hamming space, in which fast search can be easily implemented by XOR and bit-count operations. Furthermore, we integrate a linear regression model to learn hashing functions so that the hash codes for new data points can be efficiently generated. Experiments conducted on real-world large-scale multimedia datasets demonstrate the superiority of our proposed method compared with state-of-the-art techniques."
"Over the years, the connection between database theory and database practice has weakened. We argue here that the new challenges posed by XML and its applications are strengthening this connection today. We illustrate three examples of theoretical problems arising from XML applications, based on our own research."
"We propose a new class of algorithms that can be used to speed up the execution of multi-way join queries or of queries that involve one or more joins and a group-by. These new evaluation techniques allow to perform several hash-based operations (join and grouping) in one pass without repartitioning intermediate results. These techniques work particularly well for joining hierarchical structures, e.g., for evaluating functional join chains along key/foreign-key relationships. The idea is to generalize the concept of hash teams as proposed by Graefe et.al [GBC98] by indirectly partitioning the input data. Indirect partitioning means to partition the input data on an attribute that is not directly needed for the next hash-based operation, and it involves the construction of bitmaps to approximate the partitioning for the attribute that is needed in the next hash-based operation. Our performance experiments show that such generalized hash teams perform significantly better than conventional strategies for many common classes of decision support queries."
"The clustering problem is a difficult problem for the data stream domain. This is because the large volumes of data arriving in a stream renders most traditional algorithms too inefficient. In recent years, a few one-pass clustering algorithms have been developed for the data stream problem. Although such methods address the scalability issues of the clustering problem, they are generally blind to the evolution of the data and do not address the following issues: (1) The quality of the clusters is poor when the data evolves considerably over time. (2) A data stream clustering algorithm requires much greater functionality in discovering and exploring clusters over different portions of the stream."
"Spatial data mining is the discovery of interesting relationships and characteristics that may exist implicitly in spatial databases. In this paper, we explore whether clustering methods have a role to play in spatial data mining. To this end, we develop a new clustering method called CLAHANS which is based on randomized search. We also develop two spatial data mining algorithms that use CLAHANS. Our analysis and experiments show that with the assistance of CLAHANS, these two algorithms are very effective and can lead to discoveries that are difficult to find with current spatial data mining algorithms. Furthermore, experiments conducted to compare the performance of CLAHANS with that of existing clustering methods show that CLAHANS is the most efficient."
"With the exponential growth of the World Wide Web, looking for pages with high quality and relevance in the Web has become an important research field. There have been many keyword-based search engines built for this purpose. However, these search engines usually suffer from the problem that a relevant Web page may not contain the keyword in its page text. Algorithms exploiting the link structure of Web documents, such as HITS, have also been proposed to overcome the problems of traditional search engines. Though these algorithms perform better than keyword-based search engines, they still have some defects. Among others, one major problem is that links in Web pages are only able to reflect the view of the page authors on the topic of those pages but not that of the page readers. In this paper, we propose a new algorithm with the idea of using virtual links which are created according to what the user behaves in browsing the output list of the query result. These virtual links are then employed to identify authoritative resources in the Web. Speci fically, the algorithm, referred to as algorithm VIPAS (standing for virtual link powered authority search), is divided into three phases. The first phase performs basic link analysis. The second phase collects statistics by observing the user behavior in browsing pages listed in the query result, and virtual links are then created according to what observed. In the third phase, these virtual links as well as real ones are taken together to produce an updated list of authoritative pages that will be presented to the user when the query with similar keywords is encountered next time. A Web warehouse is built and the algorithm is integrated into the system. By conducting experiments on the system, we have shown that VIPAS is not only very effective but also very adaptive in providing much more valuable information to users."
"Multidimensional access methods have shown high potential for significant performance improvements in various application domains. However, only few approaches have made their way into commercial products. In commercial database management systems (DBMSs) the BTree is still the prevalent indexing technique. Integrating new indexing methods into existing database kernels is in general a very complex and costly task. Exceptions exist, as our experience of integrating the UB-Tree into TransBase, a commercial DBMS, shows. The UB-Tree is a very promising multidimensional index, which has shown its superiority over traditional access methods in different scenarios, especially in OLAP applications. In this paper we discuss the major issues of a UB-Tree integration. As we will show, the complexity and cost of this task is reduced significantly due to the fact that the UBTree relies on the classical B-Tree. Even though commercial DBMSs provide interfaces for index extensions, we favor the kernel integration because of the tight coupling with the query optimizer, which allows for optimal usage of the UBTree in execution plans. Measurements on a real-world data warehouse show that the kernel integration leads to an additional performance improvement compared to our prototype implementation and competing index methods."
"In query-intensive database application areas, like decision support and data mining, systems that use vertical fragmentation have a significant performance advantage. In order to support relational or object oriented applications on top of such a fragmented data model, a flexible yet powerful intermediate language is needed. This problem has been successfully tackled in Monet, a modern extensible database kernel developed by our group. We focus on the design choices made in the Monet interpreter language (MIL), its algebraic query language, and outline how its concept of tactical optimization enhances and simplifies the optimization of complex queries. Finally, we summarize the experience gained in Monet by creating a highly efficient implementation of MIL."
"XML is rapidly emerging as a standard for exchanging business data on the World Wide Web. For the foreseeable future, however, most business data will continue to be stored in relational database systems. Consequently, if XML is to fulfill its potential, some mechanism is needed to publish relational data as XML documents. Towards that goal, one of the major challenges is finding a way to efficiently structure and tag data from one or more tables as a hierarchical XML document. Different alternatives are possible depending on when this processing takes place and how much of it is done inside the relational engine. In this paper, we characterize and study the performance of these alternatives. Among other things, we explore the use of new scalar and aggregate functions in SQL for constructing complex XML documents directly in the relational engine. We also explore different execution plans for generating the content of an XML document. The results of an experimental study show that constructing XML documents inside the relational engine can have a significant performance benefit. Our results also show the superiority of having the relational engine use what we call an ¡°outer union plan¡± to generate the content of an XML document."
"Today's information system executives desperately need to improve programmer productivity and reduce software maintenance costs. They are demanding flexibility in frameworks and architectures in order to meet unforeseen changes (see [Yankee 94]). Adaptability is a major requirement of most company's information systems efforts. Management of change is one of the key computing concepts of the 1990s.Object-oriented tools and development frameworks are starting to deliver the benefits of increased productivity and flexibility. These next-generation products now need to be combined with relational databases to leverage investments and facilitate access to business data. Object-Relational Enablers automate the process of storing complex objects in a relational database management system (see [Aberdeen 94]).The Enterprise Objects Framework product is a second generation product bringing the benefits of object-oriented programming to relational database application development. Enterprise Objects Framework enables developers to construct reusable business objects that combine business logic with persistent storage in industry-standard relational databases. Enterprise objects are first class citizens in the NEXTSTEP and OpenStep developer and user environments. They can be geographically distributed throughout heterogeneous servers within an enterprise using the Portable Distributed Objects product (see [NeXT-DO 94]).In this extended abstract we first describe the enterprise object distribution model and then give a brief synopsis of how relational data is mapped into objects. We then present an outline of the system architecture, explain how objects are mapped to multiple tables, and summarize the transaction semantics as well as the application development life-cycle. We conclude with an outlook on future development."
"Web performance is a key differentiation among content providers. Snafus and slowdowns at major web sites demonstrate the difficulty that companies face trying to scale to a large amount of web traffic. One solution to this problem is to store web content at server-side and edge-caches for fast delivery to the end users. However, for many e-commerce sites, web pages are created dynamically based on the current state of business processes, represented in application servers and databases. Since application servers, databases, web servers, and caches are independent components, there is no efficient mechanism to make changes in the database content reflected to the cached web pages. As a result, most application servers have to mark dynamically generated web pages as non-cacheable. In this paper, we describe the architectural framework of the CachePortal system for enabling dynamic content caching for database-driven e-commerce sites. We describe techniques for intelligently invalidating dynamically generated web pages in the caches, thereby enabling caching of web pages generated based on database contents. We use some of the most popular components in the industry to illustrate the deployment and applicability of the proposed architecture."
"If replacement selection is used in an external mergesort to generate initial runs, individual records are deleted and inserted in the sort operation's workspace. Variable-length records introduce the need for possibly complex memory management and extra copying of records. As a result, few systems employ replacement selection, even though it produces longer runs than commonly used algorithms. We experimentally compared several algorithms and variants for managing this workspace. We found that the simple best fit algorithm achieves memory utilization of 90% or better and run lengths over 1.8 times workspace size, with no extra copying of records and very little other overhead, for widely varying record sizes and for a wide range of memory sizes. Thus, replacement selection is a viable algorithm for commercial database systems, even for variable-length records."
"We propose a new framework for resource allocation based on concepts from microeconomics. Specifically, we address the difficult problem of managing resources in a multiple-query environment composed of queries with widely varying resource requirements. The central element of the framework is a resource broker that realizes a profit by ""selling"" resources to competing operators using a performance-based ""currency."" The guiding principle for brokering resources is profit maximization. In other words, since the currency is derived from the performance objective, the broker can achieve the best performance by making the scheduling and resource allocation decisions that maximize profit. Moreover, the broker employs dynamic techniques and adapts by changing previous allocation decisions while queries are executing. In a first validation study of the framework, we developed a prototype broker that manages memory and disk bandwidth for a multi-user query workload. The performance objective for the prototype broker is to minimize slowdown with the constraint of fairness. Slowdown measures how much higher the response time is in a multi-user environment than a single-user environment, and fairness measures how even is the degradation in response time among all queries as the system load increases, Our simulation results show the viability of the broker framework and the effectiveness of our query admission and resource allocation policies for multi-user workloads."
"Content delivery networks (CDNs) currently deliver mostly static and streaming content. However, proxy caches can improve the delivery of these content types as well. A unique value of CDNs could be in improving access to dynamic content, which cannot be cached by proxies. We refer to such a CDN as an Applications CDN, or ACDN. An ACDN will allow a content provider not to worry about the amount of resources provisioned for its application. Instead, it can deploy the application on a single computer anywhere in the network, and then the ACDN will replicate and migrate the application as needed by the observed demand. This demo shows a functional prototype of an ACDN. An ACDN has a fundamental difference with a traditional CDN oriented towards static content. A traditional CDN server is willing to satisfy any request for any content from the subscriber Web site, either from its cache or by obtaining the response from the origin server. In contrast, an ACDN server must have the requested application, including executables, underlying data, and the computing environment, to be able to process a request. Deploying an application at the time of the request is impractical; thus the ACDN can distribute requests only among the servers that currently have a replica of the application; at the same time, the applications must be placed on ACDN servers asynchronously with requests. Thus, ACDN must provide solutions for the following problems that traditional CDNs do not face: Application distribution framework: An ACDN needs a mechanism to deploy an application replica dynamically, and to keep the replica consistent. The latter issue is complicated by the fact that an application typically contains multiple components whose versions must be mutually consistent for the application to function properly. Content placement algorithm: An ACDN must decide which applications to deploy where and when. Content placement is solved trivially in traditional CDNs by cache replacement algorithms. Request distribution algorithm: in addition to load and proximity factors that traditional CDNs must consider, the request distribution mechanism in an ACDN must be aware of where in the system applications are currently deployed. An ACDN is different from Edge-Side Includes (ESI) from Akamai, 1 which divides a dynamic page into a static template and dynamic fragments and reconstructs the final page at cache servers."
"The problem of indexing path queries in semistructured/XML databases has received considerable attention recently, and several proposals have advocated the use of structure indexes as supporting data structures for this problem. In this paper, we investigate efficient update algorithms for structure indexes. We study two kinds of updates -- the addition of a subgraph, intended to represent the addition of a new file to the database, and the addition of an edge, to represent a small incremental change. We focus on three instances of structure indexes that are based on the notion of graph bisimilarity. We propose algorithms to update the bisimulation partition for both kinds of updates and show how they extend to these indexes. Our experiments on two real world data sets show that our update algorithms are an order of magnitude faster than dropping and rebuilding the index. To the best of our knowledge, no previous work has addressed updates for structure indexes based on graph bisimilarity."
"Many web users monitor dynamic data such as stock prices, real-time sensor data and traffic data for making on-line decisions. Instances of such data can be viewed as data streams. In this paper, we consider techniques for creating a resilient and efficient content distribution network for such dynamically changing streaming data. We address the problem of maintaining the coherency of dynamic data items in a network of repositories: data disseminated to one repository is filtered by that repository and disseminated to repositories dependent on it. Our method is resilient to link failures and repository failures. This resiliency implies that data fidelity is not lost even when the repository from which (or a communication path through which) a user obtains data experiences failures. Experimental evaluation, using real world traces of streaming data, demonstrates that (i) the (computational and communication) cost of adding this redundancy is low, and (ii) surprisingly, in many cases, adding resiliency enhancing features actually improves the fidelity provided by the system even in cases when there are no failures. To further enhance fidelity, we also propose efficient techniques for filtering data arriving at one repository and for scheduling the dissemination of filtered data to another repository. "
"This second special issue provides a forum for topical issues that demonstrate the usefulness of PLS-SEM by piloting applications of this method in the field of strategic management with strong implications for strategic research and practice. As such, the special issue targets two audiences: academics involved in the fields of strategy and management, and practitioners such as consultants. The six articles in this issue are summarized in the following paragraphs."
"Skyline queries ask for a set of interesting points from a potentially large set of data points. If we are traveling, for instance, a restaurant might be interesting if there is no other restaurant which is nearer, cheaper, and has better food. Skyline queries retrieve all such interesting restaurants so that the user can choose the most promising one. In this paper, we present a new online algorithm that computes the Skyline. Unlike most existing algorithms that compute the Skyline in a batch, this algorithm returns the first results immediately, produces more and more results continuously, and allows the user to give preferences during the running time of the algorithm so that the user can control what kind of results are produced next (e.g., rather cheap or rather near restaurants)."
"Government and industry are investing substantial resources in new technologies for accessing heterogeneous information sources, including text-based corpora, structured data, imagery, geo-spatial data, audio, video, and more. Managers of programs that fund relevant research face a difficult problem: they are required to justify investment in certain technologies and approaches versus alternate ones. These program managers recognize a need for good evaluation criteria, but there is little consensus on which criteria to use"
EFIS 2000 was held at Dublin City University in June 2000. The principal aim of this third workshop was to bring together new insights from academic research with industry-driven developments and perspectives in the area of federated information systems. This report describes the observations of the workshop together with the outcome and future research possibilities.
"Although ¡°now<¡± is expressed in SQL and CURRENT_TIMESTAMP within queries, this value cannot be stored in the database. How ever, this notion of an ever-increasing current-time value has been reflected in some temporal data models by inclusion of database-resident variables, such as ¡°now<¡± ¡°until-changed,< ¡± ¡°**,¡± ¡°@,¡± and ¡°-¡±. Time variables are very desirable, but their used also leads to a new type of database, consisting of tuples with variables, termed a variable database.<"
"The goal of this work is to support replicated network services that accept updates to numerical records from multiple wide-area locations. Given the high overhead of maintaining strong consistency, many replicated services can tolerate divergence of their shared data, as long as the numerical error is bounded. Target distributed services include replicated stock quotes services, online auctions, distributed sensor systems, wide-area resource accounting and load balancing for replicated servers. We present two algorithms to e ciently bound absolute error using only local information. Split-Weight AE separately bounds increases and decreases, while Compound-Weight AE bounds them together. The two algorithms can be combined to provide good performance and low space overhead. Our Inductive RE algorithm transforms relative error to absolute error solely based on local knowledge, taking advantage of the fact that the divergence was properly bounded prior to each invocation of the algorithm. We also discuss two optimizations that reduce the space and computational overheads in the algorithms."
"The subject of this paper is the creation of knowledge bases by enumerating and organizing all web occurrences of certain subgraphs. We focus on subgraphs that are signatures of web phenomena such as tightly-focused topic communities, webrings, taxonomy trees, keiretsus, etc. For instance, the signature of a webring is a central page with bidirectional links to a number of other pages. We develop novel algorithms for such enumeration problems. A key technical contribution is the development of a model for the evolution of the web graph, based on experimental observations derived from a snapshot of the web. We argue that our algorithms run efficiently in this model, and use the model to explain some statistical phenomena on the web that emerged during our experiments. Finally, we describe the design and implementation of Campfire, a knowledge base of over one hundred thousand web communities."
"Microsoft¡¯s strategic interest in the database field dates from 1993 and the efforts of David Vaskevitch, who is now the Microsoft Vice President in charge of the database and transaction processing product development groups. David¡¯s vision was that the world would need millions of servers, and that this presented a wonderful opportunity to a company like Microsoft that sells software in high volume and at low prices. Database systems played an important role in Vaskevitch¡¯s vision, and, indeed, in Microsoft¡¯s current product plans. David began looking for premier database and transaction processing people in late 1993. The scope of Vaskevitch¡¯s efforts included a desire for Microsoft to establish a database research group. Rick Rashid, Microsoft Research Vice President, collaborated with Vaskevitch in recruiting David Lomet from Digital¡¯s Cambridge Research Lab to initiate the Microsoft Database Research Group. Lomet joined Microsoft Research in January of 1995. Hence, Microsoft¡¯s Database Research Group is now a little over three and a half years old. One person does not a group make. Recruiting efforts continued. Surajit Chaudhuri, a researcher from HP Labs joined the Database Group in February of 1996. Paul Larson, a professor from the University of Waterloo joined in May of that year. Vivek Narasayya was initially an intern as a graduate student from the University of Washington in the summer of 1996, officially joining the group in April of 1997. Roger Barga, the newest member of the group and a new Oregon Graduate Institute Ph.D., joined in December, 1997."
"In late May, 2008, a group of database researchers, architects, users and pundits met at the Claremont Resort in Berkeley, California to discuss the state of the research field and its impacts on practice. This was the seventh meeting of this sort in twenty years, and was distinguished by a broad consensus that we are at a turning point in the history of the field, due both to an explosion of data and usage scenarios, and to major shifts in computing hardware and platforms. Given these forces, we are at a time of opportunity for research impact, with an unusually large potential for influential results across computing, the sciences and society. This report details that discussion, and highlights the group's consensus view of new focus areas, including new database engine architectures, declarative programming languages, the interplay of structured and unstructured data, cloud data services, and mobile and virtual worlds. We also report on discussions of the community's growth, including suggestions for changes in community processes to move the research agenda forward, and to enhance impact on a broader audience."
"Digital libraries are being built upon a firm foundation of prior work as the high-end information systems of the future. A component architecture approach is becoming popular, with well established support for key components like the repository, especially through the Open Archives Initiative. We consider digital objects, metadata, harvesting, indexing, searching, browsing, rights management, linking, and powerful interfaces. Flexible interaction will be possible through a variety of architectures, using buses, agents, and other technologies. The field as a whole is undergoing rapid growth, supported by advances in storage, processing, networking, algorithms, and interaction. There are many initiatives and developments, including those supporting education, and these will certainly be of benefit in Latin America."
"In a large modern enterprise, it is almost inevitable that different parts of the organization will use different systems to produce, store, and search their critical data. Yet, it is only by combining the information from these various systems that the enterprise can realize the full value of the data they contain. Database federation is one approach to data integration in which middleware, consisting of a relational database management system, provides uniform access to a number of heterogeneous data sources. In this paper, we describe the basics of database federation, introduce several styles of database federation, and outline the conditions under which each style of federation should be used. We discuss the benefits of an information integration solution based on database technology, and we demonstrate the utility of the database federation approach through a number of usage scenarios involving IBM's DB2 product."
"Aggregation in traditional database systems is performed in batch mode: a query is submitted, the system processes a large volume of data over a long period of time, and, eventually, the final answer is returned. This archaic approach is frustrating to users and has been abandoned in most other areas of computing. In this paper we propose a new online aggregation interface that permits users to both observe the progress of their aggregation queries and control execution on the fly. After outlining usability and performance requirements for a system supporting online aggregation, we present a suite of techniques that extend a database system to meet these requirements. These include methods for returning the output in random order, for providing control over the relative rate at which different aggregates are computed, and for computing running confidence intervals. Finally, we report on an initial implementation of online aggregation in POSTGRES."
"The Internet community has recently been focused on peer-to-peer systems like Napster, Gnutella, and Freenet. The grand vision ¡ª a decentralized community of machines pooling their resources to benefit everyone ¡ª is compelling for many reasons: scalability, robustness, lack of need for administration, and even anonymity and resistance to censorship. Existing peer-to-peer (P2P) systems have focused on specific application domains (e.g. music files) or on providing filesystem-like capabilities; these systems ignore the semantics of data. An important question for the database community is how data management can be applied to P2P, and what we can learn from and contribute to the P2P area. We address these questions, identify a number of potential research ideas in the overlap between data management and P2P systems, present some preliminary fundamental results, and describe our initial work in constructing a P2P data management system."
"Since the last issue of this column six months ago, there have been many interesting program announcements, some of which have already passed deadline. We'll go over these announcements anyway, with the hope that they can get the readers better prepared for future funding opportunities. But first, we'll talk about the continuing budget battle at Congress, and the recent turmoil at NASA."
"The automation of Web services interoperation is gaining a considerable momentum as a paradigm for effective Business-to-Business collaboration [2]. Established enterprises are continuously discovering new opportunities to form alliances with other enterprises, by offering value-added integrated services. However, the technology to compose Web services in appropriate time-frames has not kept pace with the rapid growth and volatility of available opportunities. Indeed, the development of integrated Web services is often ad-hoc and requires a considerable eort of low level programming. This approach is inadequate given the size and the volatility of the Web. Furthermore, the number of services to be integrated may be large, so that approaches where the development of an integrated service requires the understanding of each of the underlying services are inappropriate. In addition, Web services may need to be composed as part of a short term partnership, and disbanded when the partnership is no longer profitable. Hence, the integration of a large number of Web services requires scalable and flexible techniques, such as those based on declarative languages. Also, the execution of an integrated service in existing approaches is usually centralised, whereas the underlying services are distributed and autonomous. This calls for the investigation of distributed execution paradigms (e.g., peer-to-peer models), that do not suffer of the scalability and availability problems of centralised coordination [3].    Motivated by these concerns, we have developed the SELF-SERV platform for rapid composition of Web services [1]. In SELF-SERV, Web services are declaratively composed, and the resulting composite services are executed in a peer-to-peer and dynamic environment. In this paper we overview the design and implementation of the SELF-SERV system."
"The emergence and growing popularity of Internet-based electronic market-places, in their various forms, has raised the challenge to explore genericity in market design. In this paper we present a domain-specific software architecture that delineates the abstract components of a generic market and specifies control and data-flow constraints between them, and a framework that allows convenient pluggability of components that implement specific market policies. The framework was realized in the GEM system. GEM provides infrastructure services that allow market designers to focus solely on market-issues. In addition, it allows dynamic (re)configuration of components. This functionality can be used to change market-policies as the environment or market trends change, adding another level of flexibility to market designers and administrators."
"Oracle's corporate mission is to enable the Information Age through network computing, a vision of broader access to information for all and the empowerment and increased productivity that can result. The technology implications of the network computing vision are ubiquitous access via low-cost appliances to smaller numbers of larger databases, accessed via professionally managed networks compliant with open internetworking protocols. The latest release of the Oracle data server, Oracle8, provides new technology for management of very large databases containing rich and user-defined data types, and is continuing to evolve to make it economically beneficial to store all forms of digital information in a database."
"In many applications from telephone fraud detection to network management, data arrives in a stream, and there is a need to maintain a variety of statistical summary information about a large number of customers in an online fashion. At present, such applications maintain basic aggregates such as running extrema values (MIN, MAX), averages, standard deviations, etc., that can be computed over data streams with limited space in a straightforward way. However, many applications require knowledge of more complex aggregates relating different attributes, so-called correlated aggregates. As an example, one might be interested in computing the percentage of international phone calls that are longer than the average duration of a domestic phone call. Exact computation of this aggregate requires multiple passes over the data stream, which is infeasible."
"Systems for managing and querying semistructured-data sources often store data in proprietary object repositories or in a tagged-text format. We describe a technique that can use relational database management systems to store and manage semistructured data. Our technique relies on a mapping between the semistructured data model and the relational data model, expressed in a query language called STORED. When a semistructured data instance is given, a STORED mapping can be generated automatically using data-mining techniques. We are interested in applying STORED to XML data, which is an instance of semistructured data. We show how a document-type-descriptor (DTD), when present, can be exploited to further improve performance."
"The authors propose a declarative Pictorial Query Language (called PQL) that is able to express queries on an Object-Oriented geographic database drawing the features which form the query. These features refer to the classic ones of a geographic environment (geo-null, geo-points, geo-polyline, and geo-region) and define the alphabet of the above mentioned language. This language, extended with respect to a previous one, considers twelve positional operators and a set of their specifications. Moreover, the possibility to use the mentioned language to query multidimensional databases is discussed. Finally, the characteristic of the mentioned language by a query example is shown."
"In this paper we describe novel techniques that make it possible to build an industrial-strength tool for automating the choice of indexes in the physical design of a SQL database. The tool takes as input a workload of SQL queries, and suggests a set of suitable indexes. We ensure that the indexes chosen are effective in reducing the cost of the workload by keeping the index selection tool and the query optimizer ""in step"". The number of index sets that must be evaluated to find the optimal configuration is very large. We reduce the complexity of this problem using three techniques. First, we remove a large number of spurious indexes from consideration by taking into account both query syntax and cost information. Second, we introduce optimizations that make it possible to cheaply evaluate the ¡°goodness¡± of an index set. Third, we describe an iterative approach to handle the complexity arising from multicolumn indexes. The tool has been implemented on Microsoft SQL Server 7.0. We performed extensive experiments over a range of workloads, including TPC-D. The results indicate that the tool is efficient and its choices are close to optimal."
"SIGMOD should be careful not to stretch itself too thinly. The current community that SIGMOD serves is the database research-oriented community"": those producing the research results (academicians and research lab members), those utilizing the research results (DBMS, middleware, and tool vendors), and those interested in where the eld is going (forwardlooking users and consultants). At the present time, conventional database application developers and users of such applications are not SIGMOD's primary focus. "
"These advantages do not come for free. The challenge of this architecture (as of any clustered or distributed architecture) is to provide data coherency for the independent users of the system. The way to do that is to use locking. Oracle uses multiple level locking: row locks on transaction levels, instance locks within instances, and global locks among the instances. The latter are specific to Oracle Parallel Server."
"This paper introduces the Generalized Search Tree (GiST), an index structure supporting an extensible set of queries and data types. The GiST allows new data types to be indexed in a manner supporting queries natural to the types; this is in contrast to previous work on tree extensibility which only supported the traditional set of equality and range predicates. In a single data structure, the GiST provides all the basic search tree logic required by a database system, thereby unifying disparate structures such as B+-trees and R-trees in a single piece of code, and opening the application of search trees to general extensibility. To illustrate the flexibility of the GiST, we provide simple method implementations that allow it to behave like a B+-tree, an R-tree, and an RD-tree, a new index for data with set-valued attributes. We also present a preliminary performance analysis of RD-trees, which leads to discussion on the nature of tree indices and how they behave for various datasets."
"In a graphical interface which is used to display database objects, dynamic displays are updated automatically as modifications occur to the database objects being visualised. Approaches based on enlarging either the database system or the interface code to provide the appropriate communication, complicates the interaction between the two systems, as well as making later updates cumbersome. In this paper, an approach based on active rules is presented. The declarative and modular description of active rules enables active displays to be supported with minimal changes to the database or its graphical interface. Although this approach has been used to support the link between a database system and its graphical interface, it can easily be adapted to support dynamic interaction between an active database system and other external systems."
"Businessestoday need to interrelate data stored in diverse systems with differing capabilities, ideally via a single high-level query interface. We present the design of a query optimizer for Garlic [C 95], a middleware system designedto integrate data from a broad range of data sources with very different query capabilities. Garlic¡¯s optimizer extends the rule-based approach of [Loh88] to work in a heterogeneous environment, by defining generic rules for the middleware and using wrapper-provided rules to encapsulate the capabilities of each data source. This approach offers great advantages in terms of plan quality, extensibility to new sources, incremental implementationof rules for new sources, and the ability to express the capabilities of a diverse set of sources. We describe the design and implementationof this optimizer, and illustrate its actions through an example."
"A number of researchers have become interested in the design of global-scale networked systems and applications. Our thesis here is that the database community's principles and technologies have an important role to play in the design of these systems. The point of departure is at the roots of database research: we generalize Codd's notion of data independence to physical environments beyond storage systems. We note analogies between the development of database indexes and the new generation of structured peer-to-peer networks. We illustrate the emergence of data independence in networks by surveying a number of recent network facilities and applications, seen through a database lens. We present a sampling of database query processing techniques that can contribute in this arena, and discuss methods for adoption of these technologies."
"The UniSQL/X unified relational and object--cmented database system is designed to support application development in either a convenuonal host programming Ianguagc (such as C), or an Object-aiented programming language (such as C++ or Smalltalk). In particular, C++ programmers can take advantage of all the capabilities of UniSQL/X in C++ programming style by using the UniSQL/X C++ Interfi~ce. C programmers can access the UniSQL/X database by using the Embedded SQL/X (objectaiented SQL) Preprocessor and/or the UniSQL/X AH (call levcl interface)."
"TPC Benchmark&trade; C (TPC-C) is the modern standard for measuring OLTP performance. Running TPC-C, Tandem demonstrated a massively parallel configuration of 112 CPUs which achieved ten times higher performance than any other system previously measured (and today is still better by a factor of five). This result qualifies as the largest industry-standard benchmark ever run.This paper briefly describes how the benchmark was configured and the results which were obtained."
"Recently, broadcasting has attracted considerable attention as a means of disseminating information to large client populations in both wired and wireless settings. In this paper, we exploit versions to increase the concurrency of client transactions in the presence of updates. We consider three alternative mediums for storing versions: (a) the air: older versions are broadcast along with current data, (b) the client's local cache: older versions are maintained in cache, and (c) a local database or warehouse at the client: part of the server's database is maintained at the client in the form of a multiversion materialized view. The proposed techniques are scalable in that they provide consistency without any direct communication from clients to the server. Performance results show that the overhead of maintaining versions can be kept low, while providing a considerable increase in concur-rency."
"The DB2 Design Advisor in IBM? DB2? Universal DatabaseTM (DB2 UDB) Version 8.2 for Linux?, UNIX? and Windows? is a tool that, for a given workload, automatically recommends physical design features that are any subset of indexes, materialized query tables (also called materialized views), shared-nothing database partitionings, and multidimensional clustering of tables. Our work is the very first industrial-strength tool that covers the design of as many as four different features, a significant advance to existing tools, which support no more than just indexes and materialized views. Building such a tool is challenging, because of not only the large search space introduced by the interactions among features, but also the extensibility needed by the tool to support additional features in the future. We adopt a novel ""hybrid"" approach in the Design Advisor that allows us to take important interdependencies into account as well as to encapsulate design features as separate components to lower the reengineering cost. The Design Advisor also features a built-in module that automatically reduces the given workload, and therefore provides great scalability for the tool. Our experimental results demonstrate that our tool can quickly provide good physical design recommendations that satisfy users' requirements."
"This panel will examine the implications of the XML revolution, which is currently raging on the web, for database systems research and development."
"This paper presents the framework of an Intelligent Information Presentation System (IIPS), which provides intelligent interface presentation support for data-intensive web-based applications through the use of ontologies to drive the web site generation and maintenance process. IIPS defines a comprehensive set of ontologies to model the navigational structure, the compositional structure, and the user interfaces of data-intensive web sites, and provides a suit of tools to support site generation, maintenance, and personalization."
"Association rule mining recently attracted strong attention. Usually, the classification hierarchy over the data items is available. Users are interested in generalized association rules that span different levels of the hierarchy, since sometimes more interesting rules can be derived by taking the hierarchy into account."
"Increasingly, we are becoming a data-driven society with massive information requirements and evermore numerous on-line data sources. The research activities of the Database Group at ETH are centred on the investigation of architectures and techniques for exploring and managing the data COSMOS with its proliferation and diversity of data, and with its inherent heterogeneity. Our key aim is to provide a spectrum of data connectivity whereby data sources and application systems may cooperate at various levels of interoperability and integration. Multilevel interoperability allows application systems to cooperate with application systems, database systems to coopera.te with dat,a.base systems, and storage services to cooperate with storage services."
"Recovery activities, like logging, checkpointing and restart, are used to restore a database to a consistent state after a system crash has occurred. Recovery related overhead is particularly troublesome in a mainmemory database where I/O activities are performed for the sole purpose of ensuring data durability. In this paper we present a recovery technique for main-memory databases, whose benefits are as follows. First, disk I/O is reduced by logging to disk only redo records during normal execution. The undo log is normally resident only in main memory, and is garbage collected after transaction commit. Second, our technique reduces lock contention on account of the checkpointer by allowing action consistent checkpointing to do so, the checkpointer writes to disk relevant parts of the undo log. Third, the recovery algorithm makes only a single pass over the log. Fourth, our technique does not require the availability of any special hardware such as non-volatile RAM. Thus our recovery technique combines the benefits of several techniques proposed in the past. The ideas behind our technique can be used to advantage in disk-resident databases aa well. Permission Lo copy without fee all or part of this material is granted provided that the copies are not made or distriluled for dinxt commercial advantage, the VLDB copyright notice and the We of Ihe pullicaGon and its date appear, and notice is given Ihal copying ir by permission of the Very Large Data Base Endowmenk To copy otherwise, or lo republish, requires a fee and/or special permission jkrn Ihe Endowmrrlt. Proceedings of the 19th VLDB Conference Dublin, Ireland, 1993"
"Central to any XML query language is a path language such as XPath which operates on the tree structure of the XML document. We demonstrate in this paper that the tree structure can be effectively compressed and manipulated using techniques derived from symbolic model checking. Specifically, we show first that succinct representations of document tree structures based on sharing subtrees are highly effective. Second, we show that compressed structures can be queried directly and efficiently through a process of manipulating selections of nodes and partial decompression. We study both the theoretical and experimental properties of this technique and provide algorithms for querying our compressed instances using node-selecting path query languages such as XPath.    We believe the ability to store and manipulate large portions of the structure of very large XML documents in main memory is crucial to the development of efficient, scalable native XML databases and query engines."
"Current Web services standards enable publishing service descriptions and finding services on a match based on criteria such as method signatures or service category. However, current approaches provide no basis for selecting a good service or for comparing ratings of services. We describe a conceptual model for reputation using which reputation information can be organized and shared and service selection can be facilitated and automated."
The Capability Maturity Model [4] is an orderly way for organizations to determine the capabilities of their current processes for developing software and to establish priorities for improvement [2]. It defines five levels of progressively more mature process capability [3].
"Editor's note: For this issue's ""From the Editors,"" I invited Robert Gephart of the University of Al-berta to reflect on his observations as a long-serving , award-winning reviewer of qualitative research for A!vII Over the past two and a half years, I have developed a tremendous respect for Bob's keen eye for evaluating qualitative research submissions , and great admiration for the painstaking advice he provides authors about how to improve their work. As a world-renowned qualitative author himself, Bob is in an excellent position to provide observations about how authors might increase the chances of having their qualitative research accepted for publication at AMI In a three-way electronic mail conversation about the challenges and opportunities of qualitative research , Bob, Tom Lee, and I all concluded that many authors with potentially very interesting data sets don't seem to know how to analyze them to their full potential. This is perhaps not surprising, gi ven the clear predominance of quantitative methods and statistics courses over qualitative ones, particularly in North America, as well as the inherently greater subjectivity involved in designing and analyzing qualitative research. As such, we encouraged Bob to provide a bit of a minitutorial-complete with reference citations and examples of high-quality papers that use particular qualitative approaches-in addition to his observations about qualitative research submitted to AMI The result is a longer-than-usual ""From the Edi-tors"" column. "
"Spatial data mining, i.e., discovery of interesting characteristics and patterns that may implicitly exist in spatial databases, is a challenging task due to the huge amounts of spatial data and to the new conceptual nature of the problems which must account for spatial distance. Clustering and region oriented queries are common problems in this domain. Several approaches have been presented in recent years, all of which require at least one scan of all individual objects (points). Consequently, the computational complexity is at least linearly proportional to the number of objects to answer each query. In this paper, we propose a hierarchical statistical information grid based approach for spatial data mining to reduce the cost further. The idea is to capture statistical information associated with spatial cells in such a manner that whole classes of queries and clustering problems can be answered without recourse to the individual objects. In theory, and confirmed by empirical studies, this approach outperforms the best previous method by at least an order of magnitude, especially when the data set is very large."
"Abstract.Due to their expressive power, regular expressions (REs) are quickly becoming an integral part of language specifications for several important application scenarios. Many of these applications have to manage huge databases of RE specifications and need to provide an effective matching mechanism that, given an input string, quickly identifies the REs in the database that match it. In this paper, we propose the RE-tree, a novel index structure for large databases of RE specifications. Given an input query string, the RE-tree speeds up the retrieval of matching REs by focusing the search and comparing the input string with only a small fraction of REs in the database. Even though the RE-tree is similar in spirit to other tree-based structures that have been proposed for indexing multidimensional data, RE indexing is significantly more challenging since REs typically represent infinite sets of strings with no well-defined notion of spatial locality. To address these new challenges, our RE-tree index structure relies on novel measures for comparing the relative sizes of infinite regular languages. We also propose innovative solutions for the various RE-tree operations including the effective splitting of RE-tree nodes and computing a ""tight"" bounding RE for a collection of REs. Finally, we demonstrate how sampling-based approximation algorithms can be used to significantly speed up the performance of RE-tree operations. Preliminary experimental results with moderately large synthetic data sets indicate that the RE-tree is effective in pruning the search space and easily outperforms naive sequential search approaches."
"We present techniques for robustly scaling high-throughput, 24 x 7, data-stream processing applications. Examples of such applications include intrusion or denial-of-service detection, click-stream processing, and online analysis of financial quote streams. In the TelegraphCQ project, we implement these applications using a general-purpose continuous query (CQ) engine that executes long-running dataflows. To scale the performance of these dataflows, we parallelize them across a cluster of workstations.  For these critical applications, high availability, fault-tolerance, and scalability are important goals. These goals are challenging to achieve on a cluster because machines are bound to fail, and load imbalances are likely to arise. In this thesis, we develop the design of Flux, a reusable communication abstraction that enables long-running, parallel dataflows to adapt on-the-fly to these problems. Flux encapsulates mechanisms that allow a dataflow to mask failures and to automatically recover from them as they occur during execution. Flux leverages these same mechanisms to periodically rebalance a dataflow and keep it running efficiently. By encapsulating the critical, fault-tolerance and load-balancing logic into Flux, we enable its reuse in a variety of dataflow applications with little modification to existing dataflow components and interfaces. Thus, by simply constructing a parallel dataflow using Flux, an application developer can make the dataflow robust."
This paper describes some of the ways the Internet and World Wide Web have affected databases and data warehousing and the lasting impact in these areas.
The XQuery formalization is an ongoing effort of the W3C XML Query working group to define a precise formal semantics for XQuery. This paper briefly introduces the current state of the formalization and discusses some of the more demanding remaining challenges in formally describing an expressive query language for XML.
Extensibility is one of the mayor benefits of object-relational database management systems. We have used this system property to implement a StateMachine Module inside an object-relational database management system. The module allows the checking of dynamic integrity constraints as well as the execution of active behavior specified with the UML. Our approach demonstrates that extensibility can effectively be applied to integrate such dynamic aspects specified with UML statecharts into an object-relational database management system.
"In this paper, we present a novel index structure, called ¦¤-tree, to speed up processing of high-dimensional K-nearest neighbor (KNN) queries in main memory environment. The ¦¤-tree is a multi-level structure where each level represents the data space at different dimensionalities: the number of dimensions increases towards the leaf level which contains the data at their full dimensions. The remaining dimensions are obtained using Principal Component Analysis, which has the desirable property that the first few dimensions capture most of the information in the dataset. Each level of the tree serves to prune the search space more efficiently as the reduced dimensions can better exploit the small cache line size. Moreover, the distance computation on lower dimensionality is less expensive. We also propose an extension, called ¦¤+-tree, that globally clusters the data space and then further partitions clusters into small regions to reduce the search space. We conducted extensive experiments to evaluate the proposed structures against existing techniques on different kinds of datasets. Our results show that the ¦¤+-tree is superior in most cases."
"Abstract Spatial-Query-by-Sketch is the design of a query language for geographic information systems. It allows a user to formulate a spatial query by drawing the desired configuration with a pen on a touch-sensitive computer screen and translates this sketch into a symbolic representation that can be processed against a geographic database. Since the configurations queried usually do not match exactly the sketch, it is necessary to relax the spatial constraints drawn. This paper describes the representation of a sketch and outlines the design of the constraint relaxation methods used during query processing."
"Much of business XML data has accompanying XSD specifications. In many scenarios, ""shredding such XML data into a relational storage is a popular paradigm. Optimizing evaluation of XPath queries over such XML data requires paying careful attention to both the logical and physical designs of the relational database where XML data is shredded. None of the existing solutions has taken into account physical design of the generated relational database. In this paper, we study the interplay of logical and physical design and conclude that 1) solving them independently leads to suboptimal performance and 2) there is substantial overlap between logical and physical designs: some well-known logical design transformations generate the same mappings as physical design. Furthermore, existing search algorithms are inefficient to search the extremely large space of logical and physical design combinations. We propose a search algorithm that carefully avoids searching duplicated mappings and utilizes the workload information to further prune the search space. Experimental results confirm the effectiveness of our approach."
"Extended transaction models in databases were motivated by the needs of complex applications such as CAD and software engineering. Transactions in such applications have diverse needs, for example, they may be long lived and they may need to cooperate. We describe ASSET, a system for supporting extended transactions. ASSET consists of a set of transaction primitives that allow users to define custom transaction semantics to match the needs of specific applications. We show how the transaction primitives can be used to specify a variety of transaction models, including nested transactions, split transactions, and sagas. Application-specific transaction models with relaxed correctness criteria, and computations involving workflows, can also be specified using the primitives. We describe the implementation of the ASSET primitives in the context of the Ode database."
"We discuss data mining based on association rules for two numeric attributes and one Boolean attribute. For example, in a database of bank customers, Age and Balance are two numeric attributes, and CardLoan is a Boolean attribute. Taking the pair (Age, Balance) as a point in two-dimensional space, we consider an association rule of the form"
This paper presents a model of a nomadic middleware system with support for temporal consistency of structures semantically associated to XML-documents. Specially defined high-level operations commute with each other in most cases reducing amount of transaction aborts and increasing system availability.
"While scaling up to the enormous and growing Internet population with unpredictable usage patterns, E-commerce applications face severe challenges in cost and manageability, especially for database servers that are deployed as those applications' backends in a multi-tier configuration. Middle-tier database caching is one solution to this problem. In this paper, we present a simple extension to the existing federated features in DB2 UDB, which enables a regular DB2 instance to become a DBCache without any application modification. On deployment of a DBCache at an application server, arbitrary SQL statements generated from the unchanged application that are intended for a backend database server, can be answered: at the cache, at the backend database server, or at both locations in a distributed manner. The factors that determine the distribution of workload include the SQL statement type, the cache content, the application requirement on data freshness, and cost-based optimization at the cache. We have developed a research prototype of DBCache, and conducted an extensive set of experiments with an E-Commerce benchmark to show the benefits of this approach and illustrate tradeoffs in caching considerations."
"Multidimensional access methods have shown high potential for significant performance improvements in various application domains. However, only few approaches have made their way into commercial products. In commercial database management systems (DBMSs) the BTree is still the prevalent indexing technique. Integrating new indexing methods into existing database kernels is in general a very complex and costly task. Exceptions exist, as our experience of integrating the UB-Tree into TransBase, a commercial DBMS, shows. The UB-Tree is a very promising multidimensional index, which has shown its superiority over traditional access methods in different scenarios, especially in OLAP applications. In this paper we discuss the major issues of a UB-Tree integration. As we will show, the complexity and cost of this task is reduced significantly due to the fact that the UBTree relies on the classical B-Tree. Even though commercial DBMSs provide interfaces for index extensions, we favor the kernel integration because of the tight coupling with the query optimizer, which allows for optimal usage of the UBTree in execution plans. Measurements on a real-world data warehouse show that the kernel integration leads to an additional performance improvement compared to our prototype implementation and competing index methods."
"The tutorial surveys state-of-the-art methods for storing and retrieving multimedia data from large databases. Records (= documents) may consist of formatted fields, text, images, voice, animation etc. .4 sample query that we would like to support is ¡®in a collection of 2-d color images, find images that are similar to a sunset photograph¡¯. Indexing for images and other media is a new, active area of research; the tutorial will present recent approaches and prototype systems, for 2-d and 3-d medical image databases, 2-d color image databases, and l-d time series databases."
"We describe an algorithm for estimating the number of page fetches for a partial or complete scan of a B-tree index. The algorithm obtains estimates for the number of page fetches for an index scan when given the number of tuples selected and the number of LRU buffers currently available. The algorithm has an initial phase that is performed exactly once before any estimates are calculated. This initial phase, involving LRU buffer modeling, requires a scan of all the index entries and calculates the number of page fetches for different buffer sizes. An approximate empirical model is obtained from this data. Subsequently, an inexpensive estimation procedure is called by the query optimizer whenever it needs an estimate of the page fetches for the index scan. This procedure utilizes the empirical model obtained in the initial phase."
"Predictive queries over spatio-temporal data proved to be vital in many location-based services including traffic management, ride sharing, and advertising. In the last few years, one of the most exciting work on spatio-temporal data management is about predictive queries. In this paper, we review the current research trends and present their related applications in the field of predictive spatio-temporal queries processing. Then, we discuss some basic challenges arising from new opportunities and open problems. The goal of this paper is to catch the interesting areas and future work under the umbrella of predictive queries over spatio-temporal data."
"Events are at the core of reactive and proactive applications, which have become popular in many domains."
"Multidimensional data-base technology is a key factor in the interactive analysis of large amounts of data for decision-making purposes. In contrast to previous technologies, these databases view data as multidimensional cubes that are particularly well suited for data analysis. Multidimensional models categorize data either as facts with associated numerical measures or as textual dimensions that characterize the facts. Queries aggregate measure values over a range of dimension values to provide results such as total sales per month of a given product. Multidimensional database technology is being applied to distributed data and to new types of data that current technology often cannot adequately analyze. For example, classic techniques such as preaggregation cannot ensure fast query response times when data-such as that obtained from sensors or GPS-equipped moving objects-changes continuously. Multidimensional database technology will increasingly be applied where analysis results are fed directly into other systems, thereby eliminating humans from the loop. When coupled with the need for continuous updates, this context poses stringent performance requirements not met by current technology."
"Chopping transactions into pieces is good for performance but may lead to nonserializable executions. Many researchers have reacted to this fact by either inventing new concurrency-control mechanisms, weakening serializability, or both. We adopt a different approach. We assume a user who"
"A decade ago, the connection between objects and databases was new and was being explored in a number of different ways within our community. Driven by the perception that managing traditional business data was largely a solved problem, projects were investigating ideas such as adding abstract data types to relational databases and building extensible database systems, objectoriented database systems, and toolkits for constructing special-purpose database systems. In addition, work was underway elsewhere in the computer science research community on extending programming languages with database-inspired features such as persistence and transactions. In this paper, we take a look at where our field was a decade ago and where it is now in terms of database support for objects (and vice versa). We look both at research projects and at commercial database products. We share our vision and our biases about the future of objects and databases, and we identify a number of research challenges that remain to be addressed in order to ultimately achieve our vision. "
"Continuous Query (CQ) systems typically exploit commonality among query expressions to achieve improved efficiency through shared processing. Recently proposed CQ systems have introduced window specifications in order to support unbounded data streams. There has been, however, little investigation of sharing for windowed query operators. In this paper, we address the shared execution of windowed joins, a core operator for CQ systems. We show that the strategy used in systems to date has a previously unreported performance flaw that can negatively impact queries with relatively small windows. We then propose two new execution strategies for shared joins. We evaluate the alternatives using both analytical models and implementation in a DBMS. The results show that one strategy, called MQT, provides the best performance over a range of workload settings."
"OptimizingQueriesOnCompressedBitmapsSihem Amer-YahiaAT&T Labs{Researchsihem@research.att.comTheo doreJohnsonjohnsont@research.att.comAbstractBitmap indices are used by DBMS's to accelerate decision supp ort queries.A signi cant advantage ofbitmap indices is that complex logical selection op erations can b e p erformed very quickly, by p erformingbit-wiseAND,OR,andNOTop erators.Althoughbitmapindicescanb espaceinecientforhighcardinalityattributes,the space use of compressed bitmapscompares well to other indexingmetho ds.Oracle and Sybase IQ are two commercial pro ducts that make extensive use of compressed bitmap indices.Our recent research showed that there are several fast algorithmsfor evaluatingBo oleanop eratorson compressedbitmaps.Dep endingon the natureof the op erandbitmaps(theirformat, densityandclusterdness) and the op eration to b e p erformed (AND, NOT, ...), these algorithms can have executiontimes that are orders of magnitude di erent.Cho osing an algorithm for p erforming a Bo olean op erationhas global e ects in the Bo olean query expression, requiring global optimization.We present a linear timedynamicprogrammingsearch strategy based on a cost mo delto optimizequeryexpressionevaluationplans.We alsopresentrewritingheuristicsthat rewritethe queryexpressionto anequivalenonetoencourage b etter algorithmsassignments.Our p erformance results show that the optimizerrequiresanegligibl e amount of time to execute, and that optimized complex queries can execute up to three timesfaster than unoptimized queries on real data.1Intro ductionAbitmap indexis a bit string in which each bit is mapp ed to a record ID (RID) of a relation.A bit in thebitmap index is set (to 1) if the corresp onding RID has prop ertyP(i.e., the RID represents a customer thatlives in New York), and is reset (to 0) otherwise.In typical usage, the predicatePis true for a record if it hasthe valueafor attributeA.One such predicate is asso ciated to one bitmap index for each unique value ofthe attributeA.The predicates can b e more complex, for example bitslice indices [OQ97] and precomputedcomplex selection predicates [HEP99]."
"The Brazilian Symposium on Database Systems (SBBD) is a traditional conference in Brazil, and is sponsored by the Brazilian Computer Society. SBBD's technical program contemplates the following activities: presentation of peer reviewed full technical papers, invited talks, tutorials (either invited and selected from submissions), discussion panels and presentation of tools."
"Keyword indices, topic directories, and link-based rankings are used to search and structure the rapidly growing Web today. Surprisingly little use is made of years of browsing experience of millions of people. Indeed, this information is routinely discarded by browsers. Even deliberate bookmarks are stored in a passive and isolated manner. All this goes against Vannevar Bush¡¯s dream of the Memex : an enhanced supplement to personal and community memory. We propose to demonstrate the beginnings of a ¡®Memex¡¯ for the Web: a browsing assistant for individuals and groups with focused interests. Memex blurs the articial distinction between browsing history and deliberate bookmarks. The resulting glut of data is analyzed in a number of ways at the individual and community levels. Memex constructs a topic directory customized to the community, mapping their interests naturally to nodes in this directory. This lets the user recall topic-based browsing contexts by asking questions like \What trails was I following when I was last surng about classical music?"" and \What are some popular pages in or near my community¡¯s recent trail graph related to music?"" 1 Motivation Three paradigms have emerged for exploring the Web: keyword search, directory browsing, and following links. "
"From the Publisher: Find out just how easy it is to set up and manage a commercial Web site with Microsoft's latest high-end Web solution package, Site Server 3. With precise instructions and tons of illustrations, Web expert Brad Harris demonstrates all the tools you'll need to get up and running on the Internet. Covering everything from context management to e-commerce to site performance analysis, Microsoft Site Server 3 Bible is your one-step resource for building a successful Web enterprise. "
"We provide a principled extension of SQL, called SchemaSQL, that offers the capability of uniform manipulation of data and schema in relational multidatabase systems. We develop a precise syntax and semantics of SchemaSQL in a manner that extends traditional SQL syntax and semantics, and demonstrate the following. (1) SchemaSQL retains the flavor of SQL while supporting querying of both data and schema. (2) It can be used to transform data in a database in a structure substantially different from original database, in which data and schema may be interchanged. (3) It also permits the creation of views whose schema is dynamically dependent on the contents of the input instance. (4) While aggregation in SQL is restricted to values occurring in one column at a time, SchemaSQL permits ""horizontal"" aggregation and even aggregation over more general ""blocks"" of information. (5) SchemaSQL provides a useful facility for interoperability and data/schema manipulation in relational multidatabase systems. We provide many examples to illustrate our claims. We clearly spell out the formal semantics of SchemaSQL that accounts for all these features. We describe an architecture for the implementation of SchemaSQL and develop implementation algorithms based on available database technology that allows for powerful integration of SQL based relational DBMS. We also discuss the applicability of SchemaSQL for handling semantic heterogeneity arising in a multidatabase system."
"We describe the conceptual model of SORAC, a data modeling system developed at the University of Rhode Island. SORAC supports both semantic objects and relationships, and provides a tool for modeling databases needed for complex design domains. SORAC's set of built-in semantic relationships permits the schema designer to specify enforcement rules that maintain constraints on the object and relationship types. SORAC then automatically generates C++ code to maintain the specified enforcement rules, producing a schema that is compatible with Ontos. This facilitates the task of the schema designer, who no longer has to ensure that all methods on object classes correctly maintain necessary constraints. In addition, explicit specification of enforcement rules permits automated analysis of enforcement propagations. We compare the interpretations of relationships within the semantic and object-oriented models as an introduction to the mixed model that SORAC supports. Next, the set of built-in SORAC relationship types is presented in terms of the enforcement rules permitted on each relationship type. We then use the modeling requirements of an architectural design support system, called ArchObjects, to demonstrate the capabilities of SORAC. The implementation of the current SORAC prototype is also briefly discussed."
"Schema matching is the task of finding semantic correspondences between elements of two schemas. It is needed in many database applications, such as integration of web data sources, data warehouse loading and XML message mapping. To reduce the amount of user effort as much as possible, automatic approaches combining several match techniques are required. While such match approaches have found considerable interest recently, the problem of how to best combine different match algorithms still requires further work. We have thus developed the COMA schema matching system as a platform to combine multiple matchers in a flexible way. We provide a large spectrum of individual matchers, in particular a novel approach aiming at reusing results from previous match operations, and several mechanisms to combine the results of matcher executions. We use COMA as a framework to comprehensively evaluate the effectiveness of different matchers and their combinations for real-world schemas. The results obtained so far show the superiority of combined match approaches and indicate the high value of reuse-oriented strategies."
"A WebView is a web page automatically created from base data typically stored in a DBMS. Given the multi-tiered architecture behind database-backed web servers, we have the option of materializing a WebView inside the DBMS, at the web server, or not at all, always computing it on the fly (virtual). Since WebViews must be up to date, materialized WebViews are immediately refreshed with every update on the base data. In this paper we compare the three materialization policies (materialized inside the DBMS, materialized at the web server and virtual) analytically, through a detailed cost model, and quantitatively, through extensive experiments on an implemented system. Our results indicate that materializing at the web server is a more scalable solution and can facilitate an order of magnitude more users than the virtual and materialized inside the DBMS policies, even under high update workloads."
"A join index hierarchy method is proposed to handle the ¡°goto¡¯s on disk¡± problem in objectoriented query processing. The method constructs a hierarchy of join indices and transforms a sequence of pointer chasing operations into a simple search in an appropriate join index file, and thus accelerates navigation in object-oriented databases. The method extends the join index structure studied in relational and spatial databases, supports both forward and backward navigations among objects and classes, and localizes update propagations in the hierarchy. Our performance study shows that partial join index hierarchy outperforms several other indexing mechanisms in object-oriented query processing."
"For about a year and a half, an informal and open group of companies has been meeting to consider how the Java programming language and relational databases might be used together. Initially called JSQL and later SQLJ, the companies that have participated in this group are Compaq (Tandem), IBM, Informix, Micro Focus, Microsoft, Oracle, Sun, and Sybase. The intent of this group when it was formed was to suggest and review one another¡¯ s ideas, meeting fairly often, see where there was common understanding and agreement on syntax and semantics, and to eventuall y provide a basis for one or several formal standards. The work began with a proposal on how SQL statements might be embedded in Java, put forward by Oracle. Later Sybase put forward proposals on how to use Java in the database to provide the implementation of stored routines and user-defined data types (UDTs). Once an initial draft of a specification was put forward, the entire group participated in reviewing it, spotting problems, and suggesting enhancements. These 3 parts are, then, roughly described as:"
"Abstract. In this paper we describe the design and implementation of ParSets, a means of exploiting parallelism in the SHORE OODBMS. We used ParSets to parallelize the graph traversal portion of the OO7 OODBMS benchmark, and present speedup and scaleup results from parallel SHORE running these traversals on a cluster of commodity workstations connected by a standard ethernet. For some OO7 traversals, SHORE achieved excellent speedup and scaleup; for other OO7 traversals, only marginal speedup and scaleup occurred. The characteristics of these traversals shed light on when the ParSet approach to parallelism can and cannot be applied to speed up an application. "
"In the last decade the database research community gave valuable results in modelling and retrieving spatial objects, in a temporal framework, e.g., [8] [9]. It is recognized that the representation and the management of GIS play a central part in data manipulation and querying. In fact, the incorporation of time in them may lead to consider new types of information for modelling those highly time dependent spatial data (e.g., temperatures, land use coverage, epidemic information related to a given area, etc.) and moving objects (e.g., entities that change the relative spatial position). The trend of temporal data modelling in GIS is moving from time-stamping layer (the snapshot models, [2]), attributes (space-time composites, [5]), and spatial objects to time-stamping events or processes that are mainly based on the concepts of time sequences [8]."
"The number of processor cache misses has a critical impact on the performance of DBMSs running on servers with large main-memory configurations. In turn, the cache utilization of database systems is highly dependent on the physical organization of the records in main-memory. A recently proposed storage model, called PAX, was shown to greatly improve the performance of sequential file-scan operations when compared to the commonly implemented N-ary storage model. However, the PAX storage model can also demonstrate poor cache utilization for other common operations, such as index scans. Under a workload of heterogenous database operations, neither the PAX storage model nor the N-ary storage model is optimal."
"Approximately every five years, a group of database researchers meet to do a self-assessment of our community, including reflections on our impact on the industry as well as challenges facing our research community. This report summarizes the discussion and conclusions of the 9th such meeting, held during October 9-10, 2018 in Seattle."
"Infomaster is an information integration system that provides integrated access to multiple distributed heterogeneous information sources on the Internet, thus giving the illusion of a centralized, homogeneous information system. We say that Infomaster creates a virtual data warehouse. The core of Infomaster is a facilitator that dynamically determines an efficient way to answer the user's query using as few sources as necessary and harmonizes the heterogeneities among these sources. Infomaster handles both structural and content translation to resolve differences between multiple data sources and the multiple applications for the collected data. Infomaster connects to a variety of databases using wrappers, such as for Z39.50, SQL databases through ODBC, EDI transactions, and other World Wide Web (WWW) sources. There are several WWW user interfaces to Infomaster, including forms based and textual. Infomaster also includes a programmatic interface and it can download results in structured form onto a client computer. Infomaster has been in production use for integrating rental housing advertisements from several newspapers (since fall 1995), and for meeting room scheduling (since winter 1996). Infomaster is also being used to integrate heterogeneous electronic product catalogs."
"The Java programming language [1,3] from its inception has been publicized as a web programming language. Many programmers have developed simple applications such as games, clocks, news tickers and stock tickers in order to create informative, innovative web sites. However, it is important to note that the Java programming language possesses much more capability. The language components and constructs originally designed to enhance the functionality of Java as a web-based programming language can be utilized in a broader extent. Java provides a developer with the tools allowing for the creation of innovative network, database, and Graphical User Interface (GUI) applications. In fact, Java and its associated technologies such as JDBC API [11,5], JDBC drivers [2,12], threading [10], and AWT provide the programmer with the much-needed assistance for the development of platform-independent database-independent interfaces. Thus, it is possible to build a graphical database interface capable of connecting and querying distributed databases [13,14]. Here are components that are important for building the database interface we have in mind."
"Current State of Health Promotion The science and art of health promotion has made very impressive progress in the past two decades. It has evolved from :in innovative idea that made conceptual sense, but had no scientific backing to a maturing field supported by over ],000 empirical studies which demonstrate the positive health and financial impact of programs, and practiced by virtually all major employers in the US. Despite this progress, health promotion is not a part of mainstream medicine. Only a small fraction, probably less than 1%, of the $1.149 trillion spent annually on medical care is spent on health promotion. Despite the progress we h~.ve made on developing the science of health promotion, it is not recognized as a mature science by any respected scientific group. Repeated analyses conclude that roughly half of all prematu:ve deaths in the United States are from lifestyle related causes. Indeed, conservative estimates are that tobacco kills 450,000; obesity kills 300,000; and alcohol kills 100,000. "
"In Spring 2003, Joe Hellerstein at Berkeley and Natassa Ailamaki at CMU collaborated in designing and running parallel editions of an undergraduate database course that exposed students to developing code in the core of a ful-function database system. As part of this exercise, our course teams developed new programming projects based on the PostgreSQL open-source DBMS. This report describes our experience with this effort."
"Research work in programming languages and in database systems is combating the same problems of scale, change and complexity. This paper looks at the present difficulties of relating persistent data with changing programs. It illustrates the influence that the present interfaces have on programming methodology and algorithm design. It recognises the need for new language primitives to encapsulate database concepts and a few putative primitives are examined. It is suggested that such primitives could simplify the use of databases by programmers. These ideas are illustrated with examples from geometric modelling using Algol 68."
"We propose a product specification database which is suited to product evolution, modeling the product specification as an object. In this database, we propose a behavioral constraint to maintain consistency. Furthermore, this database can manage visual specification, such as operational specification, which is hard to handle in an ordinary database. We have been developing Visual CASE: an object-oriented software development system for home appliances. Visual CASE is a visual prototyping system based on the object model we propose. In this paper, we show that the product specification is easy to examine, using visual prototyping. We also discuss implementation issues of the database applied to the home appliance software development process. "
"Previous studies on mining association rules find rules at single concept level, however, mining association rules at multiple concept levels may lead to the discovery of more specific and concrete knowledge from data. In this study, a top-down progressive deepening method is developed for mining multiplelevel association rules from large transaction databases by extension of some existing association rule mining techniques. A group of variant algorithms are proposed based on the ways of sharing intermediate results, with the relative performance tested on different kinds of data. Relaxation of the rule conditions for finding ¡°level-crossing¡± association rules is also discussed in the paper."
"Similarity retrieval mechanisms should utilize generalized quadratic form distance functions as well as the Euclidean distance function since ellipsoid queries parameters may vary with the user and situation. In this paper, we present the spatial transformation technique that yields a new search method for adaptive ellipsoid queries with quadratic form distance functions. The basic idea is to transform the bounding rectangles in the original space, wherein distance from a query point is measured by quadratic form distance functions, into spatial objects in a new space wherein distance is measured by Euclidean distance functions. Our method significantly reduces CPU cost due to the distance approximation by the spatial transformation; exact distance evaluations are avoided for most of the accessed bounding rectangles in the index structures. We also present the multiple spatial transformation technique as an extension of the spatial transformation technique. The multiple spatial transformation technique adjusts the tree structures to suit typical ellipsoid queries; the search algorithm utilizes the adjusted structure. This technique reduces both page accesses and CPU time for ellipsoid queries. Experiments using various matrices and index structures demonstrate the superiority of the proposed methods."
"This paper showcases some of the newly introduced parallel execution methods in Oracle RDBMS. These methods provide highly scalable and adaptive evaluation for the most commonly used SQL operations - joins, group-by, rollup/cube, grouping sets, and window functions. The novelty of these techniques is their use of multi-stage parallelization models, accommodation of optimizer mistakes, and the runtime parallelization and data distribution decisions. These parallel plans adapt based on the statistics gathered on the real data at query execution time. We realized enormous performance gains from these adaptive parallelization techniques. The paper also discusses our approach to parallelize queries with operations that are inherently serial. We believe all these techniques will make their way into big data analytics and other massively parallel database systems."
"All existing proposals for querying XML (e.g., XQuery) rely on a pattern-specification language that allows (1) path navigation and branching through the label structure of the XML data graph, and (2) predicates on the values of specific path/branch nodes, in order to reach the desired data elements. Optimizing such queries depends crucially on the existence of concise synopsis structures that enable accurate compile-time selectivity estimates for complex path expressions over graph-structured XML data. In this paper, we extent our earlier work on structural XSKETCH synopses and we propose an (augmented) XSKETCH synopsis model that exploits localized stability and value-distribution summaries (e.g., histograms) to accurately capture the complex correlation patterns that can exist between and across path structure and element values in the data graph. We develop a systematic XSKETCH estimation framework for complex path expressions with value predicates and we propose an efficient heuristic algorithm based on greedy forward selection for building an effective XSKETCH for a given amount of space (which is, in general, an NP-hard optimization problem). Implementation results with both synthetic and real-life data sets verify the effectiveness of our approach."
"The IFO data model was proposed by Abiteboul and Hull [Abiteboul 87] as a formalized semantic database model. It has been claimed by the authors that the model subsumes the Relational model [Codd 70], the Entity-Relationship model [Chen 76], the Functional Data Model [Kerschberg 76] and virtually all of the structured aspects of the Semantic Data Model [Hammer 81], the INSYDE Model [King 85], and the Extended Semantic Hierarchy Model [Brodie 84].This paper examines the IFO data model as presented in [Abiteboul 87], compares it to other models, and thus concludes that the IFO data model is actually a subset of the Semantic Data Model proposed by Hammer in [Hammer 81]. The paper also shows that the IFO data model has failed to support concepts that are essential to both the E-R model and the Semantic Data Model which are claimed to be subsumed by the IFO model.Section 2 discusses the three IFO constructs, objects, fragments, and relationships. The mapping of these constructs to constructs in the Semantic Data Model is established as an informal proof of the result that the IFO model is subsumed by the SDM.Section 3 lists constructs supported by the Entity-Relationship model [Chen 76, Teorey 86] as will as constructs supported by SDM [Hammer 81]that the IFO data model fails to support."
"Real data mining/analysis applications call for a framework which adequately supports knowledge discovery as a multi-step process, where the input of one mining operation can be the output of another. Previous studies, primarily focusing on fast computation of one speci c mining task at a time, ignore this vital issue. Motivated by this observation, we develop a unied model supporting all major mining and analysis tasks. Our model consists of three distinct worlds, corresponding to intensional and extensional dimensions, and to data sets. The notion of dimension is a centerpiece of the model. Equipped with hierarchies, dimensions integrate the output of seemingly dissimilar mining and analysis operations in a clean manner. We propose an algebra, called the dimension algebra, for manipulating (intensional) dimensions, as well as operators that serve as \bridges"" between the worlds. We demonstrate by examples that several real data mining processes can be captured using our model and algebra. We demonstrate the naturality of the algebra by establishing several identities. Finally, we discuss e cient implementation of the proposed framework."
"The concept of serializability has been the traditionally accepted correctness criterion in database systems. However in multidatabase systems (MDBSs), ensuring global serializability is a difficult task. The difficulty arises due to the heterogeneity of the concurrency control protocols used by the participating local database management systems (DBMSs), and the desire to preserve the autonomy of the local DBMSs. In general, solutions to the global serializability problem result in executions with a low degree of concurrency. The alternative, relaxed serializability, may result in data inconsistency."
"Privacy ¨C the control over one¡¯s personal data ¨C and security ¨C the attempted access to data by unauthorized others ¨C are two critical problems for both e-commerce consumers and sites alike. Without either, consumers will not visit or shop at a site, nor can sites function effectively without considering both. This chapter reviews the current state of the art and the relevance for privacy and security respectively. We examine privacy from social psychological, organizational, technical, regulatory, and economic perspectives. We then examine security from technical, social and organizational, and economic perspectives."
"Commercial relational database systems today provide only limited temporal support. To address the needs of applications requiring rich temporal data and queries, we have built TIP (Temporal Information Processor), a temporal extension to the Informix database system based on its DataBlade technology. Our TIP DataBlade extends Informix with a rich set of datatypes and routines that facilitate temporal modeling and querying. TIP provides both C and Java libraries for client applications to access a TIP-enabled database, and provides end-users with a GUI interface for querying and browsing temporal data."
"There has been recent interest in using relational database systems to store and query XML documents. Each of the techniques proposed in this context works by (a) creating tables for the purpose of storing XML documents (also called relational schema generation), (b) storing XML documents by shredding them into rows in the created tables, and (c) converting queries over XML documents into SQL queries over the created tables. Since relational schema generation is a physical database design issue -- dependent on factors such as the nature of the data, the query workload and availability of schemas -- there have been many techniques proposed for this purpose. Currently, each relational schema generation technique requires its own query processor to efficiently convert queries over XML documents into SQL queries over the created tables. In this paper, we present an efficient technique whereby the same query-processor can be used for all such relational schema generation techniques. This greatly simplifies the task of relational schema generation by eliminating the need to write a special-purpose query processor for each new solution to the problem. In addition, our proposed technique enables users to query seamlessly across relational data and XML documents. This provides users with unified access to both relational and XML data without them having to deal with separate databases."
"We consider the view data lineageproblem in a warehousing environment: For a given data item in a materialized warehouse view, we want to identify the set of source data items that produced the view item. We formally define the lineage problem, develop lineage tracing algorithms for relational views with aggregation, and propose mechanisms for performing consistent lineage tracing in a multisource data warehousing environment. Our result can form the basis of a tool that allows analysts to browse warehouse data, select view tuples of interest, and then ¡°drill-through¡± to examine the exact source tuples that produced the view tuples of interest."
"The learning-enhanced relevance feedback has been one of the most active research areas in content-based image retrieval in recent years. However, few methods using the relevance feedback are currently available to process relatively complex queries on large image databases. In the case of complex image queries, the feature space and the distance function of the user's perception are usually different from those of the system. This difference leads to the representation of a query with multiple clusters (i.e., regions) in the feature space. Therefore, it is necessary to handle disjunctive queries in the feature space.In this paper, we propose a new content-based image retrieval method using adaptive classification and cluster-merging to find multiple clusters of a complex image query. When the measures of a retrieval method are invariant under linear transformations, the method can achieve the same retrieval quality regardless of the shapes of clusters of a query. Our method achieves the same high retrieval quality regardless of the shapes of clusters of a query since it uses such measures. Extensive experiments show that the result of our method converges to the user's true information need fast, and the retrieval quality of our method is about 22% in recall and 20% in precision better than that of the query expansion approach, and about 34% in recall and about 33% in precision better than that of the query point movement approach, in MARS."
"Pervasive computing introduces data management requirements that must be tackled in a growing variety of lightweight computing devices. Personal folders on chip, networks of sensors and data hosted by autonomous mobile computers are different illustrations of the need for evaluating queries confined in hardware constrained computing devices. RAM is the most limiting factor in this context. This paper gives a thorough analysis of the RAM consumption problem and makes the following contributions. First, it proposes a query execution model that reaches a lower bound in terms of RAM consumption. Second, it devises a new form of optimization, called iteration filter, that drastically reduces the prohibitive cost incurred by the preceding model, without hurting the RAM lower bound. Third, it analyses how the preceding techniques can benefit from an incremental growth of RAM. This work paves the way for setting up co-design rules helping to calibrate the RAM resource of a hardware platform according to given application's requirements as well as to adapt an application to an existing hardware platform. To the best of our knowledge, this work is the first attempt to devise co-design rules for data centric embedded applications. We illustrate the effectiveness of our techniques through a performance evaluation."
"A Bloom Filter is a space-efficient randomized data structure allowing membership queries over sets with certain allowable errors. It is widely used in many applications which take advantage of its ability to compactly represent a set, and filter out effectively any element that does not belong to the set, with small error probability. This paper introduces the Spectral Bloom Filter (SBF), an extension of the original Bloom Filter to multi-sets, allowing the filtering of elements whose multiplicities are below a threshold given at query time. Using memory only slightly larger than that of the original Bloom Filter, the SBF supports queries on the multiplicities of individual keys with a guaranteed, small error probability. The SBF also supports insertions and deletions over the data set. We present novel methods for reducing the probability and magnitude of errors. We also present an efficient data structure and algorithms to build it incrementally and maintain it over streaming data, as well as over materialized data with arbitrary insertions and deletions. The SBF does not assume any a priori filtering threshold and effectively and efficiently maintains information over the entire data-set, allowing for ad-hoc queries with arbitrary parameters and enabling a range of new applications."
"Digital libraries bring about the integration, management, and communication of gigabytes of multimedia data in a distributed environment. Digital library systems currently envision users as being static when they access information. But it is expected in the near future that tens of millions of users will have access to a digital library through wireless access. Providing digital library services to users whose location is constantly changing, whose network connections are through a wireless medium, and whose computing power is low necessitates modifications to existing digital library systems. In this paper, we identify the issues that arise when users are mobile, classify queries that are specific to mobile users and introduce an architecture that supports flexible and transparent access to digital libraries for mobile users. The main features of the architecture include a layered data representation, support of adaptability, dual broadcast and on demand querying, caching, and mobile-specific user interfaces."
"This paper discusses issues related to the integration of spatial operators into the new generation of SQL-like query languages. Starting from spatial data models, current spatial extensions of query languages are briefly reviewed and research directions are highlighted. A taxonomy of requirements to be satisfied by spatial operators is proposed with emphasis on users' needs and on the introduction of data uncertainty support. Further, spatial operators are classified into the three important categories of topological, projective, and metric operators and for each of them the state of the art is outlined."
"Mobility demands the systems be adaptive. One approach is to make adaptation transparent to applications, allowing them to remain unchanged. An alternative approach views adaptation as a collaborative partnership between applications and the system. This paper is a status report on our research on both fronts. We report on our considerable experience with application-transparent adaptation in the Coda File System. We also describe our ongoing work on application-aware adaptation in Odyssey."
"The evolving challenges in lifesciences research cannot be all addressed by off-the-shelf bioinformatics applications. Life scientists need to analyze their data using novel or context-sensitive approaches that might be published in recent journals and publications, or based on their own hypotheses and assumptions. The genomics Research Network Architecture (gRNA) is a highly programmable, modular environment specially designed to invigorate the development of genomics-centric tools for life sciences-research. The gRNA provides the development environment in which new applications can be quickly written, and the deployment environment in which they can systematically avail of computing resources and integrate information from distributed biological data sources."
"One important step in integrating heterogeneous databases is matching equivalent attributes: Determining which fields in two databases refer to the same data. The meaning of information may be embodied within a. database model, a conceptual schema, application programs, or data contents. Integration involves extracting semantics, expressing them as metadata, and matching semantically equivalent data elements. We present a procedure using a classifier to categorize attributes according to their field specifications and data values, then train a neural network to recognize similar attributes. In our technique, the knowledge of how to match equivalent data elements is ¡°discovered¡± from metadata , not ¡°pre-programmed¡±."
"Concurrency control is essential to the correct functioning of a database due to the need for correct, reproducible results. For this reason, and because concurrency control is a well-formulated problem, there has developed an enormous body of literature studying the performance of concurrency control algorithms. Most of this literature uses either analytic modeling or random number-driven simulation, and explicitly or implicitly makes certain assumptions about the behavior of transactions and the patterns by which they set and unset locks. Because of the difficulty of collecting suitable measurements, there have been only a few studies which use trace-driven simulation, and still less study directed toward the characterization of concurrency control behavior of real workloads. In this paper, we present a study of three database workloads, all taken from IBM DB2 relational database systems running commercial applications in a production environment. This study considers topics such as frequency of locking and unlocking, deadlock and blocking, duration of locks, types of locks, correlations between applications of lock types, two-phase versus non-two-phase locking, when locks are held and released, etc. In each case, we evaluate the behavior of the workload relative to the assumptions commonly made in the research literature and discuss the extent to which those assumptions may or may not lead to erroneous conclusions."
"Publisher Summary This chapter explores the basic functionality of the volume data model. It considers examples from biology and volumes of measurement from quantum physics. The data model is similar in the two cases, but the operations that are commonly used are quite different. In the second case, for instance, one is often interested in conditions on the behavior of local differential operators, such as zero-flow surfaces, while in the biological case one has a mix of value conditions and geometric condition. With these two application fields, this chapter highlights the generality and flexibility of the model. The system is based on a commercial database, augmented with specialized functions to manipulate the volume data model. The chapter demonstrates various operations specifying queries both using a graphical user interface and entering them directly in structured query language (SQL) augmented with the volume algebra operations."
"The optimization capabilities of RDBMSs make them attractive for executing data transformations. However, despite the fact that many useful data transformations can be expressed as relational queries, an important class of data transformations that produce several output tuples for a single input tuple cannot be expressed in that way. To overcome this limitation, we propose to extend Relational Algebra with a new operator named data mapper. In this paper, we formalize the data mapper operator and investigate some of its properties. We then propose a set of algebraic rewriting rules that enable the logical optimization of expressions with mappers and prove their correctness. Finally, we experimentally study the proposed optimizations and identify the key factors that influence the optimization gains."
"An interdisciplinary research community needs to address challenging issues raised by applying workflow management technology in information systems. This conclusion results from the NSF workshop on Workflow and Process Automation in Information Systems which was held at the State Botanical Garden of Georgia during May 8-10, 1996. The workshop brought together active researchers and practitioners from several communities, with significant representation from database and distributed systems, software process and software engineering, and computer supported cooperative work. The presentations given at the workshop are available in the form of an electronic proceedings of this workshop at http://lsdis.cs.uga.edu/activities/). This report is the joint work of selected representatives from the workshop and it documents the results of significant group discussions and exchange of ideas."
The OASIS Prototype is under development at Dublin City University in Ireland. We describe a multi-database architecture which uses the ODMG model as a canonical model and describe an extention for construction of virtual schemas within the multidatabase system. The OMG model is used to provide a standard distribution layer for data from local databases. This takes the form of CORBA objects representing export schemas from separate data sources.
"Database systems are concerned with structured data. Unfortunately, data is still often available in an unstructured manner (e.g., in files) even when it does have a strong internal structure (e.g., electronic documents or programs). In a previous paper [2], we focussed on the use of high-level query languages to access such files and developed optimization techniques to do so. In this paper, we consider how structured data stored in files can be updated using database update languages."
"We describe the design and implementation of real-time data management services. These services combine technologies developed in the context of real-time distributed object management, object DBMSs, and scheduling. This combination simplifies many of the services, and produces a result which is greater than the sum of its parts, because it can be used to improve the portability and flexibility of real-time applications."
"On-Line Analytical Processing (OLAP) and Data Warehousing are decision support technologies. Their goal is to enable enterprises to gain competitive advantage by exploiting the ever-growing amount of data that is collected and stored in corporate databases and files for better and faster decision making. Over the past few years, these technologies have experienced explosive growth, both in the number of products and services offered, and in the extent of coverage in the trade press. Vendors, including all database companies, are paying increasing attention to all aspects of decision support."
"The Distributed Information Search COmponent (DISCO) is a prototype heterogeneous distributed database that accesses underlying data sources. The DISCO prototype currently focuses on three central research problems in the context of these systems. First, since the capabilities of each data source is different, transforming queries into subqueries on data source is difficult. We call this problem the weak data source problem. Second, since each data source performs operations in a generally unique way, the cost for performing an operation may vary radically from one wrapper to another. We call this problem the radical cost problem. Finally, existing systems behave rudely when attempting to access an unavailable data source. We call this problem the ungraceful failure problem."
"It is well known that context plays an important role in the meaning of a work of art. This paper addresses the dynamic context of a collection of linked multimedia documents, of which the web is a perfect example. Contextual document semantics emerge through identification of various users' browsing paths though this multimedia collection. In this paper, we present techniques that use multimedia information as part of this determination. Some implications of our approach are that the author of a webpage cannot completely define that document's semantics and that semantics emerge through use."
"Despite decades of research on AQP (approximate query processing), our understanding of sample-based joins has remained limited and, to some extent, even superficial. The common belief in the community is that joining random samples is futile. This belief is largely based on an early result showing that the join of two uniform samples is not an independent sample of the original join, and that it leads to quadratically fewer output tuples. Unfortunately, this early result has little applicability to the key questions practitioners face. For example, the success metric is often the final approximation's accuracy, rather than output cardinality. Moreover, there are many non-uniform sampling strategies that one can employ. Is sampling for joins still futile in all of these settings? If not, what is the best sampling strategy in each case? To the best of our knowledge, there is no formal study answering these questions."
"He single-handedly constructed the cost-based optimizer for which Ingres is still well known. With only minor modifications, his design survives to this day. His Ingres co-workers remember his intense determination to deliver the best technology possible and his willingness to do whatever it took to make good on that goal Even though he took a fair amount of kidding about it, it was not unexpected for early arrivers at the office to find him sleeping on the foam pad he kept under his desk when in the midst of this project. Some of this work was reported in [ 11"
"In this column, we review these three books: 1. The Problem With Software: Why Smart Engineers Write Bad Code, by Adam Barr. Answers to a question many of us have probably asked; and what we can do about it. Review by Shoshana Marcus. 2. Theorems of the 21st Century: Volume I, by Bogdan Grechuk. The background, context, and statement of numerous important (accessible) mathematical theorems from the past 20 years."
"As database application performance depends on the utilization of the memory hierarchy, smart data placement plays a central role in increasing locality and in improving memory utilization. Existing techniques, however, do not optimize accesses to all levels of the memory hierarchy and for all the different workloads, because each storage level uses different technology (cache, memory, disks) and each application accesses data using different patterns. Clotho is a new buffer pool and storage management architecture that decouples in-memory page layout from data organization on non-volatile storage devices to enable independent data layout design at each level of the storage hierarchy. Clotho can maximize cache and memory utilization by (a) transparently using appropriate data layouts in memory and non-volatile storage, and (b) dynamically synthesizing data pages to follow application access patterns at each level as needed. Clotho creates in-memory pages individually tailored for compound and dynamically changing workloads, and enables efficient use of different storage technologies (e.g., disk arrays or MEMS-based storage devices). This paper describes the Clotho design and prototype implementation and evaluates its performance under a variety of workloads using both disk arrays and simulated MEMS-based storage devices."
"Suitable data set organizers are necessary to help users assimilating information retrieved from a database. In this paper we present (1) a general hypertextual framework for the interaction with tables, and (2) a specialization of the framework in order to present in hypertextual format the results of queries expressed in terms of a visual semantic query language."
"The plan for ""e-Government"", and the need to facilitate interactions between citizen and Public Administration, make find in the electronic identity card EIC one of the most important means to access network services in a secure way. There are five inspiring principles: ??security for the complete lifecycle of the card from production of the physical support to initialisation, emission and its use as a service card. Security must be addressed the point of view of both police and citizen; ??network service access to bring Public Administration (at both central and local level) nearer to the citizen; ??interoperability ie compatibility of national network services by use of the same card standard open technological architecture international standard compliance and vendor independence nationwide; ??virtual centralisation for authorisation and logging operations during production and emission processes; ??full independence of local authorities (which release the EIC) to install their local services. 1 Layout and environment The EIC is an hybrid smart card with two different technologies aboard: a 16K microchip and a laser band. Due to the restricted printable area of the card, all data are written without labels. This approach allows a multilingual solution where needed, for example, in the frontier regions such as the Italian/French, Italian/Slovenian and Italian/German borders. On the first side are the name of the authority releasing the card, the personal data of the cardholder (surname, name, place and date of birth, photo and sex), a unique card ID number and the ICAO band. On the other side are the cardholder's address and fiscal code, the card's validity period and the two electronic devices: the chip and the laser band. On the laser band are replicated, in embedded hologram, personal data and images of the citizen's fingerprint (not mandatory) and holograph signature."
"Previous research has shown that cache behavior is important for main memory index structures. Cache conscious index structures such as Cache Sensitive Search Trees (CSS-Trees) perform lookups much faster than binary search and T-Trees. However, CSS-Trees are designed for decision support workloads with relatively static data. Although B+-Trees are more cache conscious than binary search and T-Trees, their utilization of a cache line is low since half of the space is used to store child pointers. Nevertheless, for applications that require incremental updates, traditional B+-Trees perform well."
"The Teradata Multimedia Object Manager is a general-purpose content analysis multimedia server designed for symmetric multiprocessing and massively parallel processing environments. The Multimedia Object Manager defines and manipulates user-defined functions (UDFs), which are invoked in parallel to analyze or manipulate the contents of multimedia objects. Several computationally intensive applications of this technology, which use large persistent datasets, include fingerprint matching, signature verification, face recognition, and speech recognition/translation."
"In large federated and shared-nothing databases, resources can exhibit widely fluctuating characteristics. Assumptions made at the time a query is submitted will rarely hold throughout the duration of query processing. As a result, traditional static query optimization and execution techniques are ineffective in these environments."
"On-Line Analytical Processing (OLAP) systems provide good performance and ease-of-use when retrieving summary information from very large amounts of data. However, the complex structures and relationships inherent in related non-summary data are not handled well by OLAP systems. In contrast, object database systems are built to handle such complexity, but do not support summary querying well. This paper presents OLAP++, a flexible, federated system that enables OLAP users to exploit simultaneously the features of OLAP and object database systems. In a previous paper [1], we have defined a comprehensive framework for handling federations of OLAP and object databases, including the SumQL++ language that allows OLAP systems to naturally support queries that refer to and retrieve data from object databases. The OLAP++ system allows data to be handled using the most appropriate data model and technology: OLAP systems for summary data and object database systems for the more complex, general data. Also, the need for physical integration of data is reduced considerably. We present a case study based on the Transaction Processing Council (TPC) TPC-R benchmark [3]. The system is implemented in C++ on top of the Object Protocol Model (OPM) system [4] and the Microsoft SQL Server OLAP Services system [2]. )HGHUDWLRQV RI 2/$3 DQG 2EMHFW 'DWDEDVHV"
"Multi-dimensional data is being generated at an ever increasing rate in practically all modern applications. The development of techniques and tools to extract useful information out of such data is one of critical challenges to be tackled in the 21st century. Visualization is one popular technique for achieving effective data exploration by exploiting the visual perception abilities of domain experts. Visualization involves the graphical presentation of data and information for the purposes of communicating results, verifying hypotheses, and qualitative exploration. In this demonstration, we present our solution to particular challenges we have been tackling in this area in the context of our XMDVtool project, a multi-year effort funded by NSF. These include multivariate data visualization to facilitate outlier and pattern discovery via a variety of displays, visual interaction tools, scalability of these visualization techniques to large data sets, interaction with commercial database technology and, more recently, extensions to handle data of very high-dimensionality."
Putting electronic business on a sound foundation --- model theoretically as well as technologically --- has to be seen as a central challenge for research as well as for commercial development. This paper concentrates on the discovery and the negotiation phase of concluding an agreement based on a contract. We present a methodology how to come seamlessly from a many-to-many relationship in the discovery phase to a one-to-one relationship in the contract negotiation phase. Making the content of the contracts persistent is achieved by reconstructing contract templates by means of mereologic (logic of the whole-part relation). Possibly nested sub-structures of the contract template are taken as a basis for negotiation in a dialogical way. For the negotiation itself the contract templates are extended by implications (logical) and sequences (topical).
"The query execution engine in Microsoft SQL Server employs hash-based algorithms for inner and outer joins, semi-joins, set operations (such as intersection), grouping, and duplicate removal. The implementation combines many techniques proposed individually in the research literature but never combined in a single implementation, neither in a product nor in a research prototype. One of the paper¡¯s contributions is a design that cleanly integrates most existing techniques. One technique, however, which we call hash teams and which has previously been described only in vague terms, has not been implemented in prior research or product work. It realizes in hash-based query processing many of the benefits of interesting orderings in sort-based query processing. Moreover, we describe how memory is managed in complex and bushy query evaluation plans with multiple sort and hash operations. Finally, we report on the effectiveness of hashing using two very typical database queries, including the performance effects of hash teams."
"I'd like to start out by welcoming the new officers of the Society. At our Board of Directors meeting in Raleigh, NC we elected the following new officers for the EMC Society: President Elect ¡ª Bob Scully Vice President, Communications ¡ª Flavio Canavero Vice President, Member Services ¡ª Bob Davis Vice President, Standards ¡ª Don Heirman Vice President, Technical Services ¡ª Colin Brench Vice President, Conferences ¡ª Bruce Archambeault Treasurer ¡ª John LaSalle"
"We present a multi-dimensional database model, which we believe can serve as a conceptual model for On-Line Analytical Processing (OLAP)-based applications. Apart from providing the functionalities necessary for OLAP-based applications, the main feature of the model we propose is a clear separation between structural aspects and the contents. This separation of concerns allows us to define data manipulation languages in a reasonably simple, transparent way. In particular, we show that the data cube operator can be expressed easily. Concretely, we define an algebra and a calculus and show them to be equivalent. We conclude by comparing our approach to related work. The conceptual multi-dimensional database model developed here is orthogonal to its implementation, which is not a subject of the present paper."
"We identify an emergent class of database systems that has not been dealt with extensively in the literature that we call ARCS (Active, Rapidly Changing data Systems) databases. These systems impose certain unique requirements on databases that monitor and control them. These requirements are such that traditional data and transaction management models appear inadequate. We present an analysis of data and transaction characteristics in ARCS systems and identify relevant research issues."
"Database systems must become more open to retain their relevance as a technology of choice and necessity. Openness implies not only databases exporting their data, but also exporting their services. This is as true in classical application areas as in non-classical (GIS, multimedia, design, etc).This paper addresses the problem of exporting storage-management services of indexing, replication and basic query processing. We describe an abstract-object storage model which provides the basic mechanism, 'likeness', through which these services are applied uniformly to internally-stored, internally-defined data, and to externally-stored, externally-defined data. Managing external data requires the coupling of external operations to the database system. We discuss the interfaces and protocols required of these to achieve correct resource management and admit efficient realisation. Throughout, we demonstrate our solutions in the area of semi-structured file management; in our case, geospatial metadata files."
"In this paper, we present continuous research on data analysis based on our previous work on the shrinking approach. Shrinking[19] is a novel data preprocessing technique which optimizes the inner structure of data inspired by the Newton's Universal Law of Gravitation[16]in the real world. It can be applied in many data mining fields. In this approach data are moved along the direction of the density gradient, thus making the inner structure of data more prominent. It is conducted on a sequence of grids with different cell sizes. In this paper, we applied the Fuzzy concept to improve the performance of the shrinking approach, targeting the better decision making for the movement for individual data points in each iteration. This approach can assist to improve the performance of existing data analysis approaches."
"Content-based retrieval of images is the ability to retrieve images that are similar to a query image. Oracle8i Visual Information Retrieval provides this facility based on technology licensed from Virage, Inc. This product is built on top of Oracle8i interMedia which enables storage, retrieval and management of images, audios and videos. Images are matched using attributes such as color, texture and structure and efficient content-based retrieval is provided using indexes of an image index type. The design of the index type is based on a multi-level filtering algorithm. The filters reduce the search space so that the expensive comparison algorithm operates on a small subset of the data. Bitmap indexes are used to evaluate the first filter resulting in a design which performs well and is scalable. The image index type is built using Oracle8i extensible indexing technology, allowing users to create, use, and drop instances of this index type as they would any other standard index. In this paper we present an overview of the product, the design of the image index type, and some performance results of our product."
"Information integration provides a competitive advantage to businesses and is fundamental to on demand computing. It is strategic area of investment by software companies today whose goal is to provide a unified view of the data regardless of differences in data format, data location and access interfaces, dynamically manage data placement to match availability, currency and performance requirements, and provide autonomic features that reduce the burden on IT staffs for managing complex data architectures. This paper describes the motivation for integrating information for on demand computing, explains its requirements, and illustrates its value through usage scenarios. As shown in the paper, there is still a tremendous amount of research, engineering, and development work needed to make the full information integration vision a reality and it is expected that software companies will continue to heavily invest in aggressively pursing the information integration vision."
"Unfortunately, this will be my last influential papers column. I've been editor for about five years now (how time flies!) and have enjoyed it immensely. I've always found it rewarding to step back and look at why we do the research we do, and this column makes a big contribution to the process of self-examination. Further, I feel that there's a strong need for ways to publicly and explicitly highlight ""quality"" in papers. Criticism is easy, and is the more common experience given the amount of reviewing (and being reviewed) we typically engage in. I look forward to seeing this column in future issues."
"Most of new databases are no more built from scratch, but re-use existing data from several autonomous data stores. To facilitate application development, the data to be re-used should preferably be redefined as a virtual database, providing for the logical unification of the underlying data sets. This unification process is called database integration. This chapter provides a global picture of the issues raised and the approaches that have been proposed to tackle the problem."
"Satisfiability, implication, and equivalence problems involving conjunctive inequalities are important and widely encountered database problems that need to be efficiently and effectively processed. In this article we consider two popular types of arithmetic inequalities, (XopY) and (X op C), where X and Y are attributes, C is a constant of the domain or X, and op ¡Ê{<, ¡Ü, =, ¡Ù, >, ¡Ý). These inequalities are most frequently used in a database system, inasmuch as the former type of inequality represents a 0-join, and the latter is a selection. We study the satisfiability and implication problems under the integer domain and the real domain, as well as under two different operator sets ({<, ¡Ü, =, ¡Ý, >} and {<, ¡Ü, =, ¡Ù, ¡Ý, >}). Our results show that solutions under different domains and/or different operator sets are quite different. Out of these eight cases, excluding two cases that had been shown to be NP-hard, we either report the first necessary and sufficient conditions for these problems as well as their efficient algorithms with complexity analysis (for four cases), or provide an improved algorithm (for two cases). These iff conditions and algorithms are essential to database designers, practitioners, and researchers. These algorithms have been implemented and an experimental study comparing the proposed algorithms and those previously known is conducted. Our experiments show that the proposed algorithms are more efficient than previously known algorithms even for small input. The C++ code can be obtained by an anonymous ftp from <archive.fiu.edu>."
"A range-sum query is very popular and becomes important in finding trends and in discovering relationships between attributes in diverse database applications. It sums over the selected cells of an OLAP data cube where target cells are decided by the specified query ranges. The direct method to access the data cube itself forces too many cells to be accessed, therefore it incurs a severe overhead. The response time is very crucial for OLAP applications which need interactions with users. In the recent dynamic enterprise environment, data elements in the cube are frequently changed. The response time is affected in such an environment by the update cost as well as the search cost of the cube. In this paper, we propose an efficient algorithm to reduce the update cost significantly while maintaining reasonable search efficiency, by using an index structure called the ? -tree. In addition, we propose a hybrid method to provide either an approximate result or a precise one to reduce the overall cost of queries. It is useful for various applications that need a quick approximate answer rather than an accurate one, such as decision support systems."
"Reliable request-response interactions, in which the server never executes a given request more than once, are being used to support business and safety-critical operations in diverse sectors, such as banking, E-commerce, or healthcare. This form of interactions can be quite difficult to implement, because the client, server, or communication channel may fail, potentially requiring diverse and complex recovery procedures, which may result in duplicate messages being processed at the server. In this paper we address the following question: could we provide a meaningful taxonomy of reliable request-response protocols? We generate valid sequences of client and server actions, organize the generated sequences into a prefix tree, and classify them according to their reliability semantics and memory requirements. The tree reveals three families of protocols matching common real-world implementations that try to deliver exactly-once or at-most-once. The strict organization of the protocols provides a solid foundation for creating correct services, and we show that it also serves to easily identify fallacies and pitfalls of existing implementations."
"Recent developments in database technology, such as deductive database systems, have given rise to the demand for new, cost-effective optimization techniques for join expressions. In this paper many different algorithms that compute approximate solutions for optimizing join orders are studied since traditional dynamic programming techniques are not appropriate for complex problems. Two possible solution spaces, the space of left-deep and bushy processing trees, are evaluated from a statistical point of view. The result is that the common limitation to left-deep processing trees is only advisable for certain join graph types. Basically, optimizers from three classes are analysed: heuristic, randomized and genetic algorithms. Each one is extensively scrutinized with respect to its working principle and its fitness for the desired application. It turns out that randomized and genetic algorithms are well suited for optimizing join expressions. They generate solutions of high quality within a reasonable running time. The benefits of heuristic optimizers, namely the short running time, are often outweighed by merely moderate optimization performance."
"Object-oriented database (OODB) users bring with them large quantities of legacy data (megabytes and even gigabIn addition, scientific OODB users continually generate new data. All this data must be loaded into the OODB. Every relational database system has a load utility , but most OODBs do not. The process of loading data into an OODB is complicated by inter-object references, or relationships, in the data. These relationships are expressed in the OODB as object identifiers, which are not known at the time the load data is generated; they may contain cycles; and there may be implicit system-maintained inverse relationships that must also be stored. W e introduce seven algorithms for loading data into an OODB that examine different techniques for dealing with circular and inverse relationships. W e present a performance study based on both an analytic model and an implementation of all seven algorithms on top of the Shore object repository . Our study demonstrates that it is ortant to choose a load algorithm carefully; in some cases the best algorithm achieved an improvement of one to two orders of magnitude over the naive algorithm"
"Intrusion detection systems have traditionally been based on the characterization of an attack and the tracking of the activity on the system to see if it matches that characterization. Recently, new intrusion detection systems based on data mining are making their appearance in the field. This paper describes the design and experiences with the ADAM (Audit Data Analysis and Mining) system, which we use as a testbed to study how useful data mining techniques can be in intrusion detection."
"Query optimizers are error prone, due to both their nature and the increased search space that modern query processing requires them to manage. This paper introduces the Sybase Adaptive Server Enterprise (ASE) Abstract Plan (AP) language, a novel technology that puts together a set of proven techniques to palliate optimizer mistaken decisions. The AP language is a 2-way user-optimizer communication mechanism based on a physical level relational algebra. AP expressions are used both by the optimizer to describe the plan that it selected and by the user to direct the optimizer choices. APs are not textually part of the query. They are persistent objects stored in the system catalogs. APs yield important performance gains by eliminating all optimizer errors."
"National Tsing Hua University (NTttU) was founded in 1911 and is located in a suburb of the city of Hsinehu, Taiwan, about 50 miles southwest of Taipei, the capital city. Its Computer Science Department was established in 1977, and currently has 23 faculty members"
"We present a simple, exact algorithm for identifying in a multiset the items with frequency more than a threshold ¦È. The algorithm requires two passes, linear time, and space 1/¦È. The first pass is an on-line algorithm, generalizing a well-known algorithm for finding a majority element, for identifying a set of at most 1/¦È items that includes, possibly among others, all items with frequency greater than ¦È."
"Most RDBMSs maintain a set of histograms for estimating the selectivities of given queries. These selectivities are typically used for cost-based query optimization. While the problem of building an accurate histogram for a given attribute or attribute set has been well-studied, little attention has been given to the problem of building and tuning a set of histograms collectively for multidimensional queries in a self-managed manner based only on query feedback. In this paper, we present SASH, a Self-Adaptive Set of Histograms that addresses the problem of building and maintaining a set of histograms. SASH uses a novel two-phase method to automatically build and maintain itself using query feedback information only. In the online tuning phase, the current set of histograms is tuned in response to the estimation error of each query in an online manner. In the restructuring phase, a new and more accurate set of histograms replaces the current set of histograms. The new set of histograms (attribute sets and memory distribution) is found using information from a batch of query feedback. We present experimental results that show the effectiveness and accuracy of our approach."
"Similarity search in large time series databases has attracted much research interest recently. It is a difficult problem because of the typically high dimensionality of the data. The most promising solutions involve performing dimensionality reduction on the data, then indexing the reduced data with a multidimensional index structure. Many dimensionality reduction techniques have been proposed, including Singular Value Decomposition (SVD), the Discrete Fourier transform (DFT), and the Discrete Wavelet Transform (DWT). In this article, we introduce a new dimensionality reduction technique, which we call Adaptive Piecewise Constant Approximation (APCA). While previous techniques (e.g., SVD, DFT and DWT) choose a common representation for all the items in the database that minimizes the global reconstruction error, APCA approximates each time series by a set of constant value segments of varying lengths such that their individual reconstruction errors are minimal. We show how APCA can be indexed using a multidimensional index structure. We propose two distance measures in the indexed space that exploit the high fidelity of APCA for fast searching: a lower bounding Euclidean distance approximation, and a non-lower-bounding, but very tight, Euclidean distance approximation, and show how they can support fast exact searching and even faster approximate searching on the same index structure. We theoretically and empirically compare APCA to all the other techniques and demonstrate its superiority."
"We are living in an exciting time in the field of clinical research. There are changes occurring that will alter how medical care is provided, and it is the work of clinical research professionals that will lead these changes. In this column, the Chair of ACRP¡¯s Association Board of Trustees considers the impact of genetics in medicine and their application through precision medicine. "
"A tone arm assembly for record players having a first motor for rotating a tone arm in the vertical direction, a second motor for rotating the tone arm in the horizontal direction with respect to a record disc, respectively, a detector for detecting low frequency vertical and horizontal vibrations of the tone arm during the reproduction of a record disc and feeding back an output signal of the detector to the motors so as to cancel the vibrations, whereby high fidelity reproduction of sounds can be performed. Further, the stylus pressure adjustment and elevation angle adjustment of the tone arm are also performed."