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cs/0606011
|
Vectorial Resilient $PC(l)$ of Order $k$ Boolean Functions from AG-Codes
|
cs.CR cs.IT math.IT
|
Propagation criterion of degree $l$ and order $k$ ($PC(l)$ of order $k$) and
resiliency of vectorial Boolean functions are important for cryptographic
purpose (see [1, 2, 3,6, 7,8,10,11,16]. Kurosawa, Stoh [8] and Carlet [1] gave
a construction of Boolean functions satisfying $PC(l)$ of order $k$ from binary
linear or nonlinear codes in. In this paper, algebraic-geometric codes over
$GF(2^m)$ are used to modify Carlet and Kurosawa-Satoh's construction for
giving vectorial resilient Boolean functions satisfying $PC(l)$ of order $k$.
The new construction is compared with previously known results.
|
cs/0606014
|
On the Capacity of Multiple Access Channels with State Information and
Feedback
|
cs.IT math.IT
|
In this paper, the multiple access channel (MAC) with channel state is
analyzed in a scenario where a) the channel state is known non-causally to the
transmitters and b) there is perfect causal feedback from the receiver to the
transmitters. An achievable region and an outer bound are found for a discrete
memoryless MAC that extend existing results, bringing together ideas from the
two separate domains of MAC with state and MAC with feedback. Although this
achievable region does not match the outer bound in general, special cases
where they meet are identified.
In the case of a Gaussian MAC, a specialized achievable region is found by
using a combination of dirty paper coding and a generalization of the
Schalkwijk-Kailath, Ozarow and Merhav-Weissman schemes, and this region is
found to be capacity achieving. Specifically, it is shown that additive
Gaussian interference that is known non-causally to the transmitter causes no
loss in capacity for the Gaussian MAC with feedback.
|
cs/0606015
|
The Size of Optimal Sequence Sets for Synchronous CDMA Systems
|
cs.IT math.IT
|
The sum capacity on a symbol-synchronous CDMA system having processing gain
$N$ and supporting $K$ power constrained users is achieved by employing at most
$2N-1$ sequences. Analogously, the minimum received power (energy-per-chip) on
the symbol-synchronous CDMA system supporting $K$ users that demand specified
data rates is attained by employing at most $2N-1$ sequences. If there are $L$
oversized users in the system, at most $2N-L-1$ sequences are needed. $2N-1$ is
the minimum number of sequences needed to guarantee optimal allocation for
single dimensional signaling. $N$ orthogonal sequences are sufficient if a few
users (at most $N-1$) are allowed to signal in multiple dimensions. If there
are no oversized users, these split users need to signal only in two dimensions
each. The above results are shown by proving a converse to a well-known result
of Weyl on the interlacing eigenvalues of the sum of two Hermitian matrices,
one of which is of rank 1. The converse is analogous to Mirsky's converse to
the interlacing eigenvalues theorem for bordering matrices.
|
cs/0606016
|
Performance Analysis of Iterative Channel Estimation and Multiuser
Detection in Multipath DS-CDMA Channels
|
cs.IT math.IT
|
This paper examines the performance of decision feedback based iterative
channel estimation and multiuser detection in channel coded aperiodic DS-CDMA
systems operating over multipath fading channels. First, explicit expressions
describing the performance of channel estimation and parallel interference
cancellation based multiuser detection are developed. These results are then
combined to characterize the evolution of the performance of a system that
iterates among channel estimation, multiuser detection and channel decoding.
Sufficient conditions for convergence of this system to a unique fixed point
are developed.
|
cs/0606017
|
From semiotics of hypermedia to physics of semiosis: A view from system
theory
|
cs.HC cs.CL cs.IT math.IT
|
Given that theoretical analysis and empirical validation is fundamental to
any model, whether conceptual or formal, it is surprising that these two tools
of scientific discovery are so often ignored in the contemporary studies of
communication. In this paper, we pursued the ideas of a) correcting and
expanding the modeling approaches of linguistics, which are otherwise
inapplicable (more precisely, which should not but are widely applied), to the
general case of hypermedia-based communication, and b) developing techniques
for empirical validation of semiotic models, which are nowadays routinely used
to explore (in fact, to conjecture about) internal mechanisms of complex
systems, yet on a purely speculative basis. This study thus offers two
experimentally tested substantive contributions: the formal representation of
communication as the mutually-orienting behavior of coupled autonomous systems,
and the mathematical interpretation of the semiosis of communication, which
together offer a concrete and parsimonious understanding of diverse
communication phenomena.
|
cs/0606020
|
Imagination as Holographic Processor for Text Animation
|
cs.AI
|
Imagination is the critical point in developing of realistic artificial
intelligence (AI) systems. One way to approach imagination would be simulation
of its properties and operations. We developed two models: AI-Brain Network
Hierarchy of Languages and Semantical Holographic Calculus as well as
simulation system ScriptWriter that emulate the process of imagination through
an automatic animation of English texts. The purpose of this paper is to
demonstrate the model and to present ScriptWriter system
http://nvo.sdsc.edu/NVO/JCSG/get_SRB_mime_file2.cgi//home/tamara.sdsc/test/demo.zip?F=/home/tamara.sdsc/test/demo.zip&M=application/x-gtar
for simulation of the imagination.
|
cs/0606021
|
A simulation engine to support production scheduling using
genetics-based machine learning
|
cs.CE cs.AI
|
The ever higher complexity of manufacturing systems, continually shortening
life cycles of products and their increasing variety, as well as the unstable
market situation of the recent years require introducing grater flexibility and
responsiveness to manufacturing processes. From this perspective, one of the
critical manufacturing tasks, which traditionally attract significant attention
in both academia and the industry, but which have no satisfactory universal
solution, is production scheduling. This paper proposes an approach based on
genetics-based machine learning (GBML) to treat the problem of flow shop
scheduling. By the approach, a set of scheduling rules is represented as an
individual of genetic algorithms, and the fitness of the individual is
estimated based on the makespan of the schedule generated by using the
rule-set. A concept of the interactive software environment consisting of a
simulator and a GBML simulation engine is introduced to support human
decision-making during scheduling. A pilot study is underway to evaluate the
performance of the GBML technique in comparison with other methods (such as
Johnson's algorithm and simulated annealing) while completing test examples.
|
cs/0606022
|
Limited Feedback Beamforming Over Temporally-Correlated Channels
|
cs.IT math.IT
|
Feedback of quantized channel state information (CSI), called limited
feedback, enables transmit beamforming in multiple-input-multiple-output (MIMO)
wireless systems with a small amount of overhead. Due to its efficiency,
beamforming with limited feedback has been adopted in several wireless
communication standards. Prior work on limited feedback commonly adopts the
block fading channel model where temporal correlation in wireless channels is
neglected. This paper considers temporally-correlated channels and designs
single-user transmit beamforming with limited feedback. Analytical results
concerning CSI feedback are derived by modeling quantized CSI as a first-order
finite-state Markov chain. These results include the source bit rate generated
by time-varying quantized CSI, the required bit rate for a CSI feedback
channel, and the effect of feedback delay. In particular, based on the theory
of Markov chain convergence rate, feedback delay is proved to reduce the
throughput gain due to CSI feedback at least exponentially. Furthermore, an
algorithm is proposed for CSI feedback compression in time. Combining the
results in this work leads to a new method for designing limited feedback
beamforming as demonstrated by a design example.
|
cs/0606024
|
Consecutive Support: Better Be Close!
|
cs.AI cs.DB
|
We propose a new measure of support (the number of occur- rences of a
pattern), in which instances are more important if they occur with a certain
frequency and close after each other in the stream of trans- actions. We will
explain this new consecutive support and discuss how patterns can be found
faster by pruning the search space, for instance using so-called parent support
recalculation. Both consecutiveness and the notion of hypercliques are
incorporated into the Eclat algorithm. Synthetic examples show how interesting
phenomena can now be discov- ered in the datasets. The new measure can be
applied in many areas, ranging from bio-informatics to trade, supermarkets, and
even law en- forcement. E.g., in bio-informatics it is important to find
patterns con- tained in many individuals, where patterns close together in one
chro- mosome are more significant.
|
cs/0606026
|
Generating parity check equations for bounded-distance iterative erasure
decoding
|
cs.IT math.IT
|
A generic $(r,m)$-erasure correcting set is a collection of vectors in
$\bF_2^r$ which can be used to generate, for each binary linear code of
codimension $r$, a collection of parity check equations that enables iterative
decoding of all correctable erasure patterns of size at most $m$.
That is to say, the only stopping sets of size at most $m$ for the generated
parity check equations are the erasure patterns for which there is more than
one manner to fill in theerasures to obtain a codeword.
We give an explicit construction of generic $(r,m)$-erasure correcting sets
of cardinality $\sum_{i=0}^{m-1} {r-1\choose i}$. Using a random-coding-like
argument, we show that for fixed $m$, the minimum size of a generic
$(r,m)$-erasure correcting set is linear in $r$.
Keywords: iterative decoding, binary erasure channel, stopping set
|
cs/0606027
|
Building a logical model in the machining domain for CAPP expert systems
|
cs.AI cs.CE cs.SE
|
Recently, extensive efforts have been made on the application of expert
system technique to solving the process planning task in the machining domain.
This paper introduces a new formal method to design CAPP expert systems. The
formal method is applied to provide a contour of the CAPP expert system
building technology. Theoretical aspects of the formalism are described and
illustrated by an example of know-how analysis. Flexible facilities to utilize
multiple knowledge types and multiple planning strategies within one system are
provided by the technology.
|
cs/0606029
|
Belief Calculus
|
cs.AI
|
In Dempster-Shafer belief theory, general beliefs are expressed as belief
mass distribution functions over frames of discernment. In Subjective Logic
beliefs are expressed as belief mass distribution functions over binary frames
of discernment. Belief representations in Subjective Logic, which are called
opinions, also contain a base rate parameter which express the a priori belief
in the absence of evidence. Philosophically, beliefs are quantitative
representations of evidence as perceived by humans or by other intelligent
agents. The basic operators of classical probability calculus, such as addition
and multiplication, can be applied to opinions, thereby making belief calculus
practical. Through the equivalence between opinions and Beta probability
density functions, this also provides a calculus for Beta probability density
functions. This article explains the basic elements of belief calculus.
|
cs/0606035
|
Finding roots of polynomials over finite fields
|
cs.IT math.IT
|
We propose an improved algorithm for finding roots of polynomials over finite
fields. This makes possible significant speedup of the decoding process of
Bose-Chaudhuri-Hocquenghem, Reed-Solomon, and some other error-correcting
codes.
|
cs/0606039
|
Evolutionary Design: Philosophy, Theory, and Application Tactics
|
cs.CE cs.AI
|
Although it has contributed to remarkable improvements in some specific
areas, attempts to develop a universal design theory are generally
characterized by failure. This paper sketches arguments for a new approach to
engineering design based on Semiotics - the science about signs. The approach
is to combine different design theories over all the product life cycle stages
into one coherent and traceable framework. Besides, it is to bring together the
designer's and user's understandings of the notion of 'good product'. Building
on the insight from natural sciences that complex systems always exhibit a
self-organizing meaning-influential hierarchical dynamics, objective laws
controlling product development are found through an examination of design as a
semiosis process. These laws are then applied to support evolutionary design of
products. An experiment validating some of the theoretical findings is
outlined, and concluding remarks are given.
|
cs/0606048
|
A New Quartet Tree Heuristic for Hierarchical Clustering
|
cs.DS cs.CV cs.DM math.ST physics.data-an q-bio.QM stat.TH
|
We consider the problem of constructing an an optimal-weight tree from the
3*(n choose 4) weighted quartet topologies on n objects, where optimality means
that the summed weight of the embedded quartet topologiesis optimal (so it can
be the case that the optimal tree embeds all quartets as non-optimal
topologies). We present a heuristic for reconstructing the optimal-weight tree,
and a canonical manner to derive the quartet-topology weights from a given
distance matrix. The method repeatedly transforms a bifurcating tree, with all
objects involved as leaves, achieving a monotonic approximation to the exact
single globally optimal tree. This contrasts to other heuristic search methods
from biological phylogeny, like DNAML or quartet puzzling, which, repeatedly,
incrementally construct a solution from a random order of objects, and
subsequently add agreement values.
|
cs/0606049
|
Decentralized Erasure Codes for Distributed Networked Storage
|
cs.IT cs.NI math.IT
|
We consider the problem of constructing an erasure code for storage over a
network when the data sources are distributed. Specifically, we assume that
there are n storage nodes with limited memory and k<n sources generating the
data. We want a data collector, who can appear anywhere in the network, to
query any k storage nodes and be able to retrieve the data. We introduce
Decentralized Erasure Codes, which are linear codes with a specific randomized
structure inspired by network coding on random bipartite graphs. We show that
decentralized erasure codes are optimally sparse, and lead to reduced
communication, storage and computation cost over random linear coding.
|
cs/0606051
|
Minimum Pseudo-Weight and Minimum Pseudo-Codewords of LDPC Codes
|
cs.IT math.IT
|
In this correspondence, we study the minimum pseudo-weight and minimum
pseudo-codewords of low-density parity-check (LDPC) codes under linear
programming (LP) decoding. First, we show that the lower bound of Kelly,
Sridhara, Xu and Rosenthal on the pseudo-weight of a pseudo-codeword of an LDPC
code with girth greater than 4 is tight if and only if this pseudo-codeword is
a real multiple of a codeword. Then, we show that the lower bound of Kashyap
and Vardy on the stopping distance of an LDPC code is also a lower bound on the
pseudo-weight of a pseudo-codeword of this LDPC code with girth 4, and this
lower bound is tight if and only if this pseudo-codeword is a real multiple of
a codeword. Using these results we further show that for some LDPC codes, there
are no other minimum pseudo-codewords except the real multiples of minimum
codewords. This means that the LP decoding for these LDPC codes is
asymptotically optimal in the sense that the ratio of the probabilities of
decoding errors of LP decoding and maximum-likelihood decoding approaches to 1
as the signal-to-noise ratio leads to infinity. Finally, some LDPC codes are
listed to illustrate these results.
|
cs/0606052
|
Topology for Distributed Inference on Graphs
|
cs.IT math.IT
|
Let $N$ local decision makers in a sensor network communicate with their
neighbors to reach a decision \emph{consensus}. Communication is local, among
neighboring sensors only, through noiseless or noisy links. We study the design
of the network topology that optimizes the rate of convergence of the iterative
decision consensus algorithm. We reformulate the topology design problem as a
spectral graph design problem, namely, maximizing the eigenratio~$\gamma$ of
two eigenvalues of the graph Laplacian~$L$, a matrix that is naturally
associated with the interconnectivity pattern of the network. This
reformulation avoids costly Monte Carlo simulations and leads to the class of
non-bipartite Ramanujan graphs for which we find a lower bound on~$\gamma$. For
Ramanujan topologies and noiseless links, the local probability of error
converges much faster to the overall global probability of error than for
structured graphs, random graphs, or graphs exhibiting small-world
characteristics. With noisy links, we determine the optimal number of
iterations before calling a decision. Finally, we introduce a new class of
random graphs that are easy to construct, can be designed with arbitrary number
of sensors, and whose spectral and convergence properties make them practically
equivalent to Ramanujan topologies.
|
cs/0606060
|
Complex Networks: New Concepts and Tools for Real-Time Imaging and
Vision
|
cs.CV cs.DC physics.soc-ph
|
This article discusses how concepts and methods of complex networks can be
applied to real-time imaging and computer vision. After a brief introduction of
complex networks basic concepts, their use as means to represent and
characterize images, as well as for modeling visual saliency, are briefly
described. The possibility to apply complex networks in order to model and
simulate the performance of parallel and distributed computing systems for
performance of visual methods is also proposed.
|
cs/0606062
|
Logics for Unranked Trees: An Overview
|
cs.LO cs.DB
|
Labeled unranked trees are used as a model of XML documents, and logical
languages for them have been studied actively over the past several years. Such
logics have different purposes: some are better suited for extracting data,
some for expressing navigational properties, and some make it easy to relate
complex properties of trees to the existence of tree automata for those
properties. Furthermore, logics differ significantly in their model-checking
properties, their automata models, and their behavior on ordered and unordered
trees. In this paper we present a survey of logics for unranked trees.
|
cs/0606065
|
On the complexity of XPath containment in the presence of disjunction,
DTDs, and variables
|
cs.DB cs.LO
|
XPath is a simple language for navigating an XML-tree and returning a set of
answer nodes. The focus in this paper is on the complexity of the containment
problem for various fragments of XPath. We restrict attention to the most
common XPath expressions which navigate along the child and/or descendant axis.
In addition to basic expressions using only node tests and simple predicates,
we also consider disjunction and variables (ranging over nodes). Further, we
investigate the containment problem relative to a given DTD. With respect to
variables we study two semantics, (1) the original semantics of XPath, where
the values of variables are given by an outer context, and (2) an existential
semantics introduced by Deutsch and Tannen, in which the values of variables
are existentially quantified. In this framework, we establish an exact
classification of the complexity of the containment problem for many XPath
fragments.
|
cs/0606066
|
The Cumulative Rule for Belief Fusion
|
cs.AI
|
The problem of combining beliefs in the Dempster-Shafer belief theory has
attracted considerable attention over the last two decades. The classical
Dempster's Rule has often been criticised, and many alternative rules for
belief combination have been proposed in the literature. The consensus operator
for combining beliefs has nice properties and produces more intuitive results
than Dempster's rule, but has the limitation that it can only be applied to
belief distribution functions on binary state spaces. In this paper we present
a generalisation of the consensus operator that can be applied to Dirichlet
belief functions on state spaces of arbitrary size. This rule, called the
cumulative rule of belief combination, can be derived from classical
statistical theory, and corresponds well with human intuition.
|
cs/0606069
|
Inference and Evaluation of the Multinomial Mixture Model for Text
Clustering
|
cs.IR cs.CL
|
In this article, we investigate the use of a probabilistic model for
unsupervised clustering in text collections. Unsupervised clustering has become
a basic module for many intelligent text processing applications, such as
information retrieval, text classification or information extraction. The model
considered in this contribution consists of a mixture of multinomial
distributions over the word counts, each component corresponding to a different
theme. We present and contrast various estimation procedures, which apply both
in supervised and unsupervised contexts. In supervised learning, this work
suggests a criterion for evaluating the posterior odds of new documents which
is more statistically sound than the "naive Bayes" approach. In an unsupervised
context, we propose measures to set up a systematic evaluation framework and
start with examining the Expectation-Maximization (EM) algorithm as the basic
tool for inference. We discuss the importance of initialization and the
influence of other features such as the smoothing strategy or the size of the
vocabulary, thereby illustrating the difficulties incurred by the high
dimensionality of the parameter space. We also propose a heuristic algorithm
based on iterative EM with vocabulary reduction to solve this problem. Using
the fact that the latent variables can be analytically integrated out, we
finally show that Gibbs sampling algorithm is tractable and compares favorably
to the basic expectation maximization approach.
|
cs/0606070
|
Is there an Elegant Universal Theory of Prediction?
|
cs.AI cs.CC
|
Solomonoff's inductive learning model is a powerful, universal and highly
elegant theory of sequence prediction. Its critical flaw is that it is
incomputable and thus cannot be used in practice. It is sometimes suggested
that it may still be useful to help guide the development of very general and
powerful theories of prediction which are computable. In this paper it is shown
that although powerful algorithms exist, they are necessarily highly complex.
This alone makes their theoretical analysis problematic, however it is further
shown that beyond a moderate level of complexity the analysis runs into the
deeper problem of Goedel incompleteness. This limits the power of mathematics
to analyse and study prediction algorithms, and indeed intelligent systems in
general.
|
cs/0606071
|
Scheduling and Codeword Length Optimization in Time Varying Wireless
Networks
|
cs.IT math.IT
|
In this paper, a downlink scenario in which a single-antenna base station
communicates with K single antenna users, over a time-correlated fading
channel, is considered. It is assumed that channel state information is
perfectly known at each receiver, while the statistical characteristics of the
fading process and the fading gain at the beginning of each frame are known to
the transmitter. By evaluating the random coding error exponent of the
time-correlated fading channel, it is shown that there is an optimal codeword
length which maximizes the throughput. The throughput of the conventional
scheduling that transmits to the user with the maximum signal to noise ratio is
examined using both fixed length codewords and variable length codewords.
Although optimizing the codeword length improves the performance, it is shown
that using the conventional scheduling, the gap between the achievable
throughput and the maximum possible throughput of the system tends to infinity
as K goes to infinity. A simple scheduling that considers both the signal to
noise ratio and the channel time variation is proposed. It is shown that by
using this scheduling, the gap between the achievable throughput and the
maximum throughput of the system approaches zero.
|
cs/0606073
|
Comparison of the estimation of the degree of polarization from four or
two intensity images degraded by speckle noise
|
cs.IR physics.optics
|
Active polarimetric imagery is a powerful tool for accessing the information
present in a scene. Indeed, the polarimetric images obtained can reveal
polarizing properties of the objects that are not avalaible using conventional
imaging systems. However, when coherent light is used to illuminate the scene,
the images are degraded by speckle noise. The polarization properties of a
scene are characterized by the degree of polarization. In standard polarimetric
imagery system, four intensity images are needed to estimate this degree . If
we assume the uncorrelation of the measurements, this number can be decreased
to two images using the Orthogonal State Contrast Image (OSCI). However, this
approach appears too restrictive in some cases. We thus propose in this paper a
new statistical parametric method to estimate the degree of polarization
assuming correlated measurements with only two intensity images. The estimators
obtained from four images, from the OSCI and from the proposed method, are
compared using simulated polarimetric data degraded by speckle noise.
|
cs/0606074
|
Rate Regions for Relay Broadcast Channels
|
cs.IT math.IT
|
A partially cooperative relay broadcast channel (RBC) is a three-node network
with one source node and two destination nodes (destinations 1 and 2) where
destination 1 can act as a relay to assist destination 2. Inner and outer
bounds on the capacity region of the discrete memoryless partially cooperative
RBC are obtained. When the relay function is disabled, the inner and outer
bounds reduce to new bounds on the capacity region of broadcast channels. Four
classes of RBCs are studied in detail. For the partially cooperative RBC with
degraded message sets, inner and outer bounds are obtained. For the
semideterministic partially cooperative RBC and the orthogonal partially
cooperative RBC, the capacity regions are established. For the parallel
partially cooperative RBC with unmatched degraded subchannels, the capacity
region is established for the case of degraded message sets. The capacity is
also established when the source node has only a private message for
destination 2, i.e., the channel reduces to a parallel relay channel with
unmatched degraded subchannels.
|
cs/0606075
|
10^(10^6) Worlds and Beyond: Efficient Representation and Processing of
Incomplete Information
|
cs.DB
|
Current systems and formalisms for representing incomplete information
generally suffer from at least one of two weaknesses. Either they are not
strong enough for representing results of simple queries, or the handling and
processing of the data, e.g. for query evaluation, is intractable.
In this paper, we present a decomposition-based approach to addressing this
problem. We introduce world-set decompositions (WSDs), a space-efficient
formalism for representing any finite set of possible worlds over relational
databases. WSDs are therefore a strong representation system for any relational
query language. We study the problem of efficiently evaluating relational
algebra queries on sets of worlds represented by WSDs. We also evaluate our
technique experimentally in a large census data scenario and show that it is
both scalable and efficient.
|
cs/0606077
|
On Sequence Prediction for Arbitrary Measures
|
cs.LG
|
Suppose we are given two probability measures on the set of one-way infinite
finite-alphabet sequences and consider the question when one of the measures
predicts the other, that is, when conditional probabilities converge (in a
certain sense) when one of the measures is chosen to generate the sequence.
This question may be considered a refinement of the problem of sequence
prediction in its most general formulation: for a given class of probability
measures, does there exist a measure which predicts all of the measures in the
class? To address this problem, we find some conditions on local absolute
continuity which are sufficient for prediction and which generalize several
different notions which are known to be sufficient for prediction. We also
formulate some open questions to outline a direction for finding the conditions
on classes of measures for which prediction is possible.
|
cs/0606078
|
Dimension Extractors and Optimal Decompression
|
cs.CC cs.IT math.IT
|
A *dimension extractor* is an algorithm designed to increase the effective
dimension -- i.e., the amount of computational randomness -- of an infinite
binary sequence, in order to turn a "partially random" sequence into a "more
random" sequence. Extractors are exhibited for various effective dimensions,
including constructive, computable, space-bounded, time-bounded, and
finite-state dimension. Using similar techniques, the Kucera-Gacs theorem is
examined from the perspective of decompression, by showing that every infinite
sequence S is Turing reducible to a Martin-Loef random sequence R such that the
asymptotic number of bits of R needed to compute n bits of S, divided by n, is
precisely the constructive dimension of S, which is shown to be the optimal
ratio of query bits to computed bits achievable with Turing reductions. The
extractors and decompressors that are developed lead directly to new
characterizations of some effective dimensions in terms of optimal
decompression by Turing reductions.
|
cs/0606081
|
New Millennium AI and the Convergence of History
|
cs.AI
|
Artificial Intelligence (AI) has recently become a real formal science: the
new millennium brought the first mathematically sound, asymptotically optimal,
universal problem solvers, providing a new, rigorous foundation for the
previously largely heuristic field of General AI and embedded agents. At the
same time there has been rapid progress in practical methods for learning true
sequence-processing programs, as opposed to traditional methods limited to
stationary pattern association. Here we will briefly review some of the new
results, and speculate about future developments, pointing out that the time
intervals between the most notable events in over 40,000 years or 2^9 lifetimes
of human history have sped up exponentially, apparently converging to zero
within the next few decades. Or is this impression just a by-product of the way
humans allocate memory space to past events?
|
cs/0606083
|
The Diversity Order of the Semidefinite Relaxation Detector
|
cs.IT math.IT
|
We consider the detection of binary (antipodal) signals transmitted in a
spatially multiplexed fashion over a fading multiple-input multiple-output
(MIMO) channel and where the detection is done by means of semidefinite
relaxation (SDR). The SDR detector is an attractive alternative to maximum
likelihood (ML) detection since the complexity is polynomial rather than
exponential. Assuming that the channel matrix is drawn with i.i.d. real valued
Gaussian entries, we study the receiver diversity and prove that the SDR
detector achieves the maximum possible diversity. Thus, the error probability
of the receiver tends to zero at the same rate as the optimal maximum
likelihood (ML) receiver in the high signal to noise ratio (SNR) limit. This
significantly strengthens previous performance guarantees available for the
semidefinite relaxation detector. Additionally, it proves that full diversity
detection is in certain scenarios also possible when using a non-combinatorial
receiver structure.
|
cs/0606084
|
The Completeness of Propositional Resolution: A Simple and
Constructive<br> Proof
|
cs.LO cs.AI
|
It is well known that the resolution method (for propositional logic) is
complete. However, completeness proofs found in the literature use an argument
by contradiction showing that if a set of clauses is unsatisfiable, then it
must have a resolution refutation. As a consequence, none of these proofs
actually gives an algorithm for producing a resolution refutation from an
unsatisfiable set of clauses. In this note, we give a simple and constructive
proof of the completeness of propositional resolution which consists of an
algorithm together with a proof of its correctness.
|
cs/0606090
|
Error Rate Analysis for Coded Multicarrier Systems over Quasi-Static
Fading Channels
|
cs.IT math.IT
|
Several recent standards such as IEEE 802.11a/g, IEEE 802.16, and ECMA
Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) for high
data-rate Ultra-Wideband (UWB), employ bit-interleaved convolutionally-coded
multicarrier modulation over quasi-static fading channels. Motivated by the
lack of appropriate error rate analysis techniques for this popular type of
system and channel model, we present two novel analytical methods for bit error
rate (BER) estimation of coded multicarrier systems operating over
frequency-selective quasi-static channels with non-ideal interleaving. In the
first method, the approximate performance of the system is calculated for each
realization of the channel, which is suitable for obtaining the outage BER
performance (a common performance measure for e.g. MB-OFDM systems). The second
method assumes Rayleigh distributed frequency-domain subcarrier channel gains
and knowledge of their correlation matrix, and can be used to directly obtain
the average BER performance. Both methods are applicable to
convolutionally-coded interleaved multicarrier systems employing Quadrature
Amplitude Modulation (QAM), and are also able to account for narrowband
interference (modeled as a sum of tone interferers). To illustrate the
application of the proposed analysis, both methods are used to study the
performance of a tone-interference-impaired MB-OFDM system.
|
cs/0606093
|
Predictions as statements and decisions
|
cs.LG
|
Prediction is a complex notion, and different predictors (such as people,
computer programs, and probabilistic theories) can pursue very different goals.
In this paper I will review some popular kinds of prediction and argue that the
theory of competitive on-line learning can benefit from the kinds of prediction
that are now foreign to it.
|
cs/0606094
|
On Typechecking Top-Down XML Tranformations: Fixed Input or Output
Schemas
|
cs.DB cs.PL
|
Typechecking consists of statically verifying whether the output of an XML
transformation always conforms to an output type for documents satisfying a
given input type. In this general setting, both the input and output schema as
well as the transformation are part of the input for the problem. However,
scenarios where the input or output schema can be considered to be fixed, are
quite common in practice. In the present work, we investigate the computational
complexity of the typechecking problem in the latter setting.
|
cs/0606096
|
Building a resource for studying translation shifts
|
cs.CL
|
This paper describes an interdisciplinary approach which brings together the
fields of corpus linguistics and translation studies. It presents ongoing work
on the creation of a corpus resource in which translation shifts are explicitly
annotated. Translation shifts denote departures from formal correspondence
between source and target text, i.e. deviations that have occurred during the
translation process. A resource in which such shifts are annotated in a
systematic way will make it possible to study those phenomena that need to be
addressed if machine translation output is to resemble human translation. The
resource described in this paper contains English source texts (parliamentary
proceedings) and their German translations. The shift annotation is based on
predicate-argument structures and proceeds in two steps: first, predicates and
their arguments are annotated monolingually in a straightforward manner. Then,
the corresponding English and German predicates and arguments are aligned with
each other. Whenever a shift - mainly grammatical or semantic -has occurred,
the alignment is tagged accordingly.
|
cs/0606097
|
Synonym search in Wikipedia: Synarcher
|
cs.IR cs.DM
|
The program Synarcher for synonym (and related terms) search in the text
corpus of special structure (Wikipedia) was developed. The results of the
search are presented in the form of graph. It is possible to explore the graph
and search for graph elements interactively. Adapted HITS algorithm for synonym
search, program architecture, and program work evaluation with test examples
are presented in the paper. The proposed algorithm can be applied to a query
expansion by synonyms (in a search engine) and a synonym dictionary forming.
|
cs/0606099
|
Fairness in Multiuser Systems with Polymatroid Capacity Region
|
cs.IT math.IT
|
For a wide class of multi-user systems, a subset of capacity region which
includes the corner points and the sum-capacity facet has a special structure
known as polymatroid. Multiaccess channels with fixed input distributions and
multiple-antenna broadcast channels are examples of such systems. Any interior
point of the sum-capacity facet can be achieved by time-sharing among corner
points or by an alternative method known as rate-splitting. The main purpose of
this paper is to find a point on the sum-capacity facet which satisfies a
notion of fairness among active users. This problem is addressed in two cases:
(i) where the complexity of achieving interior points is not feasible, and (ii)
where the complexity of achieving interior points is feasible. For the first
case, the corner point for which the minimum rate of the active users is
maximized (max-min corner point) is desired for signaling. A simple greedy
algorithm is introduced to find the optimum max-min corner point. For the
second case, the polymatroid properties are exploited to locate a rate-vector
on the sum-capacity facet which is optimally fair in the sense that the minimum
rate among all users is maximized (max-min rate). In the case that the rate of
some users can not increase further (attain the max-min value), the algorithm
recursively maximizes the minimum rate among the rest of the users. It is shown
that the problems of deriving the time-sharing coefficients or rate-spitting
scheme can be solved by decomposing the problem to some lower-dimensional
subproblems. In addition, a fast algorithm to compute the time-sharing
coefficients to attain a general point on the sum-capacity facet is proposed.
|
cs/0606100
|
The generating function of the polytope of transport matrices $U(r,c)$
as a positive semidefinite kernel of the marginals $r$ and $c$
|
cs.LG cs.DM
|
This paper has been withdrawn by the author due to a crucial error in the
proof of Lemma 5.
|
cs/0606104
|
An information-spectrum approach to large deviation theorems
|
cs.IT math.IT
|
In this paper we show a some new look at large deviation theorems from the
viewpoint of the information-spectrum (IS) methods, which has been first
exploited in information theory, and also demonstrate a new basic formula for
the large deviation rate function in general, which is a pair of the lower and
upper IS rate functions. In particular, we are interested in establishing the
general large deviation rate functions that can be derivable as the
Fenchel-Legendre transform of the cumulant generating function. The final goal
is to show a necessary and sufficient condition for the rate function to be of
Cram\'er-G\"artner-Ellis type.
|
cs/0606105
|
Iso9000 Based Advanced Quality Approach for Continuous Improvement of
Manufacturing Processes
|
cs.IR
|
The continuous improvement in TQM is considered as the core value by which
organisation could maintain a competitive edge. Several techniques and tools
are known to support this core value but most of the time these techniques are
informal and without modelling the interdependence between the core value and
tools. Thus, technique formalisation is one of TQM challenges for increasing
efficiency of quality process implementation. In that way, the paper proposes
and experiments an advanced quality modelling approach based on meta-modelling
the "process approach" as advocated by the standard ISO9000:2000. This
meta-model allows formalising the interdependence between technique, tools and
core value
|
cs/0606106
|
Self-orthogonality of $q$-ary Images of $q^m$-ary Codes and Quantum Code
Construction
|
cs.IT math.IT
|
A code over GF$(q^m)$ can be imaged or expanded into a code over GF$(q)$
using a basis for the extension field over the base field. The properties of
such an image depend on the original code and the basis chosen for imaging.
Problems relating the properties of a code and its image with respect to a
basis have been of great interest in the field of coding theory. In this work,
a generalized version of the problem of self-orthogonality of the $q$-ary image
of a $q^m$-ary code has been considered. Given an inner product (more
generally, a biadditive form), necessary and sufficient conditions have been
derived for a code over a field extension and an expansion basis so that an
image of that code is self-orthogonal. The conditions require that the original
code be self-orthogonal with respect to several related biadditive forms
whenever certain power sums of the dual basis elements do not vanish. Numerous
interesting corollaries have been derived by specializing the general
conditions. An interesting result for the canonical or regular inner product in
fields of characteristic two is that only self-orthogonal codes result in
self-orthogonal images. Another result is that image of a code is
self-orthogonal for all bases if and only if trace of the code is
self-orthogonal, except for the case of binary images of 4-ary codes. The
conditions are particularly simple to state and apply for cyclic codes. To
illustrate a possible application, new quantum error-correcting codes have been
constructed with larger minimum distance than previously known.
|
cs/0606114
|
Hidden Markov Process: A New Representation, Entropy Rate and Estimation
Entropy
|
cs.IT math.IT
|
We consider a pair of correlated processes {Z_n} and {S_n} (two sided), where
the former is observable and the later is hidden. The uncertainty in the
estimation of Z_n upon its finite past history is H(Z_n|Z_0^{n-1}), and for
estimation of S_n upon this observation is H(S_n|Z_0^{n-1}), which are both
sequences of n. The limits of these sequences (and their existence) are of
practical and theoretical interest. The first limit, if exists, is the entropy
rate. We call the second limit the estimation entropy. An example of a process
jointly correlated to another one is the hidden Markov process. It is the
memoryless observation of the Markov state process where state transitions are
independent of past observations. We consider a new representation of hidden
Markov process using iterated function system. In this representation the state
transitions are deterministically related to the process. This representation
provides a unified framework for the analysis of the two limiting entropies for
this process, resulting in integral expressions for the limits. This analysis
shows that under mild conditions the limits exist and provides a simple method
for calculating the elements of the corresponding sequences.
|
cs/0606115
|
Evaluating Variable Length Markov Chain Models for Analysis of User Web
Navigation Sessions
|
cs.AI cs.IR
|
Markov models have been widely used to represent and analyse user web
navigation data. In previous work we have proposed a method to dynamically
extend the order of a Markov chain model and a complimentary method for
assessing the predictive power of such a variable length Markov chain. Herein,
we review these two methods and propose a novel method for measuring the
ability of a variable length Markov model to summarise user web navigation
sessions up to a given length. While the summarisation ability of a model is
important to enable the identification of user navigation patterns, the ability
to make predictions is important in order to foresee the next link choice of a
user after following a given trail so as, for example, to personalise a web
site. We present an extensive experimental evaluation providing strong evidence
that prediction accuracy increases linearly with summarisation ability.
|
cs/0606117
|
Performance comparison of multi-user detectors for the downlink of a
broadband MC-CDMA system
|
cs.IT math.IT
|
In this paper multi-user detection techniques, such as Parallel and Serial
Interference Cancellations (PIC & SIC), General Minimum Mean Square Error
(GMMSE) and polynomial MMSE, for the downlink of a broadband Multi-Carrier Code
Division Multiple Access (MCCDMA) system are investigated. The Bit Error Rate
(BER) and Frame Error Rate (FER) results are evaluated, and compared with
single-user detection (MMSEC, EGC) approaches, as well. The performance
evaluation takes into account the system load, channel coding and modulation
schemes.
|
cs/0606118
|
Adapting a general parser to a sublanguage
|
cs.CL cs.IR
|
In this paper, we propose a method to adapt a general parser (Link Parser) to
sublanguages, focusing on the parsing of texts in biology. Our main proposal is
the use of terminology (identication and analysis of terms) in order to reduce
the complexity of the text to be parsed. Several other strategies are explored
and finally combined among which text normalization, lexicon and
morpho-guessing module extensions and grammar rules adaptation. We compare the
parsing results before and after these adaptations.
|
cs/0606119
|
Lexical Adaptation of Link Grammar to the Biomedical Sublanguage: a
Comparative Evaluation of Three Approaches
|
cs.CL cs.IR
|
We study the adaptation of Link Grammar Parser to the biomedical sublanguage
with a focus on domain terms not found in a general parser lexicon. Using two
biomedical corpora, we implement and evaluate three approaches to addressing
unknown words: automatic lexicon expansion, the use of morphological clues, and
disambiguation using a part-of-speech tagger. We evaluate each approach
separately for its effect on parsing performance and consider combinations of
these approaches. In addition to a 45% increase in parsing efficiency, we find
that the best approach, incorporating information from a domain part-of-speech
tagger, offers a statistically signicant 10% relative decrease in error. The
adapted parser is available under an open-source license at
http://www.it.utu.fi/biolg.
|
cs/0606121
|
Performance of Orthogonal Beamforming for SDMA with Limited Feedback
|
cs.IT math.IT
|
On the multi-antenna broadcast channel, the spatial degrees of freedom
support simultaneous transmission to multiple users. The optimal multiuser
transmission, known as dirty paper coding, is not directly realizable.
Moreover, close-to-optimal solutions such as Tomlinson-Harashima precoding are
sensitive to CSI inaccuracy. This paper considers a more practical design
called per user unitary and rate control (PU2RC), which has been proposed for
emerging cellular standards. PU2RC supports multiuser simultaneous
transmission, enables limited feedback, and is capable of exploiting multiuser
diversity. Its key feature is an orthogonal beamforming (or precoding)
constraint, where each user selects a beamformer (or precoder) from a codebook
of multiple orthonormal bases. In this paper, the asymptotic throughput scaling
laws for PU2RC with a large user pool are derived for different regimes of the
signal-to-noise ratio (SNR). In the multiuser-interference-limited regime, the
throughput of PU2RC is shown to scale logarithmically with the number of users.
In the normal SNR and noise-limited regimes, the throughput is found to scale
double logarithmically with the number of users and also linearly with the
number of antennas at the base station. In addition, numerical results show
that PU2RC achieves higher throughput and is more robust against CSI
quantization errors than the popular alternative of zero-forcing beamforming if
the number of users is sufficiently large.
|
cs/0606126
|
May We Have Your Attention: Analysis of a Selective Attention Task
|
cs.NE cs.AI
|
In this paper we present a deeper analysis than has previously been carried
out of a selective attention problem, and the evolution of continuous-time
recurrent neural networks to solve it. We show that the task has a rich
structure, and agents must solve a variety of subproblems to perform well. We
consider the relationship between the complexity of an agent and the ease with
which it can evolve behavior that generalizes well across subproblems, and
demonstrate a shaping protocol that improves generalization.
|
cs/0606128
|
Automatic forming lists of semantically related terms based on texts
rating in the corpus with hyperlinks and categories (In Russian)
|
cs.IR cs.DM
|
HITS adapted algorithm for synonym search, the program architecture, and the
program work evaluation with test examples are presented in the paper.
Synarcher program for synonym (and related terms) search in the text corpus of
special structure (Wikipedia) was developed. The results of search are
presented in the form of a graph. It is possible to explore the graph and
search graph elements interactively. The proposed algorithm could be applied to
the search request extending and for synonym dictionary forming.
|
cs/0607002
|
Coding for Parallel Channels: Gallager Bounds for Binary Linear Codes
with Applications to Repeat-Accumulate Codes and Variations
|
cs.IT math.IT
|
This paper is focused on the performance analysis of binary linear block
codes (or ensembles) whose transmission takes place over independent and
memoryless parallel channels. New upper bounds on the maximum-likelihood (ML)
decoding error probability are derived. These bounds are applied to various
ensembles of turbo-like codes, focusing especially on repeat-accumulate codes
and their recent variations which possess low encoding and decoding complexity
and exhibit remarkable performance under iterative decoding. The framework of
the second version of the Duman and Salehi (DS2) bounds is generalized to the
case of parallel channels, along with the derivation of their optimized tilting
measures. The connection between the generalized DS2 and the 1961 Gallager
bounds, addressed by Divsalar and by Sason and Shamai for a single channel, is
explored in the case of an arbitrary number of independent parallel channels.
The generalization of the DS2 bound for parallel channels enables to re-derive
specific bounds which were originally derived by Liu et al. as special cases of
the Gallager bound. In the asymptotic case where we let the block length tend
to infinity, the new bounds are used to obtain improved inner bounds on the
attainable channel regions under ML decoding. The tightness of the new bounds
for independent parallel channels is exemplified for structured ensembles of
turbo-like codes. The improved bounds with their optimized tilting measures
show, irrespectively of the block length of the codes, an improvement over the
union bound and other previously reported bounds for independent parallel
channels; this improvement is especially pronounced for moderate to large block
lengths.
|
cs/0607003
|
Tightened Upper Bounds on the ML Decoding Error Probability of Binary
Linear Block Codes
|
cs.IT math.IT
|
The performance of maximum-likelihood (ML) decoded binary linear block codes
is addressed via the derivation of tightened upper bounds on their decoding
error probability. The upper bounds on the block and bit error probabilities
are valid for any memoryless, binary-input and output-symmetric communication
channel, and their effectiveness is exemplified for various ensembles of
turbo-like codes over the AWGN channel. An expurgation of the distance spectrum
of binary linear block codes further tightens the resulting upper bounds.
|
cs/0607004
|
On the Error Exponents of Some Improved Tangential-Sphere Bounds
|
cs.IT math.IT
|
The performance of maximum-likelihood (ML) decoded binary linear block codes
over the AWGN channel is addressed via the tangential-sphere bound (TSB) and
two of its recent improved versions. The paper is focused on the derivation of
the error exponents of these bounds. Although it was exemplified that some
recent improvements of the TSB tighten this bound for finite-length codes, it
is demonstrated in this paper that their error exponents coincide. For an
arbitrary ensemble of binary linear block codes, the common value of these
error exponents is explicitly expressed in terms of the asymptotic growth rate
of the average distance spectrum.
|
cs/0607005
|
Belief Conditioning Rules (BCRs)
|
cs.AI
|
In this paper we propose a new family of Belief Conditioning Rules (BCRs) for
belief revision. These rules are not directly related with the fusion of
several sources of evidence but with the revision of a belief assignment
available at a given time according to the new truth (i.e. conditioning
constraint) one has about the space of solutions of the problem.
|
cs/0607007
|
Theory of sexes by Geodakian as it is advanced by Iskrin
|
cs.NE cs.GL
|
In 1960s V.Geodakian proposed a theory that explains sexes as a mechanism for
evolutionary adaptation of the species to changing environmental conditions. In
2001 V.Iskrin refined and augmented the concepts of Geodakian and gave a new
and interesting explanation to several phenomena which involve sex, and sex
ratio, including the war-years phenomena. He also introduced a new concept of
the "catastrophic sex ratio." This note is an attempt to digest technical
aspects of the new ideas by Iskrin.
|
cs/0607010
|
ITs, a structure sensitive information theory
|
cs.IT math.IT
|
Broadly speaking Information theory (IT) assumes no structure of the
underlying states. But what about contexts where states do have a clear
structure - how should IT cope with such situations? And if such coping is at
all possible then - how should structure be expressed so that it can be coped
with? A possible answer to these questions is presented here. Noting that IT
can cope well with a structure expressed as an accurate clustering (by shifting
to the implied reduced alphabet), a generalization is suggested in which
structure is expressed as a measure on reduced alphabets. Given such structure
an extension of IT is presented where the reduced alphabets are treated
simultaneously. This structure-sensitive IT, called ITs, extends traditional IT
in the sense that: a)there are structure-sensitive analogs to the notions of
traditional IT and b)translating a theorem in IT by replacing its notions with
their structure-sensitive counterparts, yields a (provable) theorem of ITs.
Seemingly paradoxically, ITs extends IT but it's completely within the
framework of IT. The richness of the suggested structures is demonstrated by
two disparate families studied in more detail: the family of hierarchical
structures and the family of linear structures. The formal findings extend the
scope of cases to which a rigorous application of IT can be applied (with
implications on quantization, for example). The implications on the foundations
of IT are that the assumption regarding no underlying structure of states is
not mandatory and that there is a framework for expressing such underlying
structure.
|
cs/0607012
|
A Flexible Structured-based Representation for XML Document Mining
|
cs.IR
|
This paper reports on the INRIA group's approach to XML mining while
participating in the INEX XML Mining track 2005. We use a flexible
representation of XML documents that allows taking into account the structure
only or both the structure and content. Our approach consists of representing
XML documents by a set of their sub-paths, defined according to some criteria
(length, root beginning, leaf ending). By considering those sub-paths as words,
we can use standard methods for vocabulary reduction, and simple clustering
methods such as K-means that scale well. We actually use an implementation of
the clustering algorithm known as "dynamic clouds" that can work with distinct
groups of independent variables put in separate variables. This is useful in
our model since embedded sub-paths are not independent: we split potentially
dependant paths into separate variables, resulting in each of them containing
independant paths. Experiments with the INEX collections show good results for
the structure-only collections, but our approach could not scale well for large
structure-and-content collections.
|
cs/0607013
|
Database Querying under Changing Preferences
|
cs.DB cs.AI
|
We present here a formal foundation for an iterative and incremental approach
to constructing and evaluating preference queries. Our main focus is on query
modification: a query transformation approach which works by revising the
preference relation in the query. We provide a detailed analysis of the cases
where the order-theoretic properties of the preference relation are preserved
by the revision. We consider a number of different revision operators: union,
prioritized and Pareto composition. We also formulate algebraic laws that
enable incremental evaluation of preference queries. Finally, we consider two
variations of the basic framework: finite restrictions of preference relations
and weak-order extensions of strict partial order preference relations.
|
cs/0607014
|
Strong Consistency of the Good-Turing Estimator
|
cs.IT math.IT
|
We consider the problem of estimating the total probability of all symbols
that appear with a given frequency in a string of i.i.d. random variables with
unknown distribution. We focus on the regime in which the block length is large
yet no symbol appears frequently in the string. This is accomplished by
allowing the distribution to change with the block length. Under a natural
convergence assumption on the sequence of underlying distributions, we show
that the total probabilities converge to a deterministic limit, which we
characterize. We then show that the Good-Turing total probability estimator is
strongly consistent.
|
cs/0607015
|
The uncovering of hidden structures by Latent Semantic Analysis
|
cs.IR
|
Latent Semantic Analysis (LSA) is a well known method for information
retrieval. It has also been applied as a model of cognitive processing and
word-meaning acquisition. This dual importance of LSA derives from its capacity
to modulate the meaning of words by contexts, dealing successfully with
polysemy and synonymy. The underlying reasons that make the method work are not
clear enough. We propose that the method works because it detects an underlying
block structure (the blocks corresponding to topics) in the term by document
matrix. In real cases this block structure is hidden because of perturbations.
We propose that the correct explanation for LSA must be searched in the
structure of singular vectors rather than in the profile of singular values.
Using Perron-Frobenius theory we show that the presence of disjoint blocks of
documents is marked by sign-homogeneous entries in the vectors corresponding to
the documents of one block and zeros elsewhere. In the case of nearly disjoint
blocks, perturbation theory shows that if the perturbations are small the zeros
in the leading vectors are replaced by small numbers (pseudo-zeros). Since the
singular values of each block might be very different in magnitude, their order
does not mirror the order of blocks. When the norms of the blocks are similar,
LSA works fine, but we propose that when the topics have different sizes, the
usual procedure of selecting the first k singular triplets (k being the number
of blocks) should be replaced by a method that selects the perturbed Perron
vectors for each block.
|
cs/0607016
|
An Analysis of Arithmetic Constraints on Integer Intervals
|
cs.AI cs.PL
|
Arithmetic constraints on integer intervals are supported in many constraint
programming systems. We study here a number of approaches to implement
constraint propagation for these constraints. To describe them we introduce
integer interval arithmetic. Each approach is explained using appropriate proof
rules that reduce the variable domains. We compare these approaches using a set
of benchmarks. For the most promising approach we provide results that
characterize the effect of constraint propagation. This is a full version of
our earlier paper, cs.PL/0403016.
|
cs/0607017
|
Performance of STBC MC-CDMA systems over outdoor realistic MIMO channels
|
cs.IT math.IT
|
The paper deals with orthogonal space-time block coded MC-CDMA systems in
outdoor realistic downlink scenarios with up to two transmit and receive
antennas. Assuming no channel state information at the transmitter, we compare
several linear single-user detection and spreading schemes, with or without
channel coding, achieving a spectral efficiency of 1-2 bits/s/Hz. The different
results obtained demonstrate that spatial diversity significantly improves the
performance of MC-CDMA systems, and allows different chip-mapping without
notably decreasing performance. Moreover, the global system exhibits a good
trade-off between complexity at mobile stations and performance. Then,
Alamouti's STBC MC-CDMA schemes derive full benefit from the frequency and
spatial diversities and can be considered as a very realistic and promising
candidate for the air interface downlink of the 4/sup th/ generation mobile
radio systems.
|
cs/0607018
|
Feynman Checkerboard as a Model of Discrete Space-Time
|
cs.CE
|
In 1965, Feynman wrote of using a lattice containing one dimension of space
and one dimension of time to derive aspects of quantum mechanics. Instead of
summing the behavior of all possible paths as he did, this paper will consider
the motion of single particles within this discrete Space-Time lattice,
sometimes called Feynman's Checkerboard. This empirical approach yielded
several predicted emergent properties for a discrete Space-Time lattice, one of
which is novel and testable.
|
cs/0607019
|
Modelling the Probability Density of Markov Sources
|
cs.NE
|
This paper introduces an objective function that seeks to minimise the
average total number of bits required to encode the joint state of all of the
layers of a Markov source. This type of encoder may be applied to the problem
of optimising the bottom-up (recognition model) and top-down (generative model)
connections in a multilayer neural network, and it unifies several previous
results on the optimisation of multilayer neural networks.
|
cs/0607020
|
Iterative Decoding Performance Bounds for LDPC Codes on Noisy Channels
|
cs.IT math.IT
|
The asymptotic iterative decoding performances of low-density parity-check
(LDPC) codes using min-sum (MS) and sum-product (SP) decoding algorithms on
memoryless binary-input output-symmetric (MBIOS) channels are analyzed in this
paper. For MS decoding, the analysis is done by upper bounding the bit error
probability of the root bit of a tree code by the sequence error probability of
a subcode of the tree code assuming the transmission of the all-zero codeword.
The result is a recursive upper bound on the bit error probability after each
iteration. For SP decoding, we derive a recursively determined lower bound on
the bit error probability after each iteration. This recursive lower bound
recovers the density evolution equation of LDPC codes on the binary erasure
channel (BEC) with inequalities satisfied with equalities. A significant
implication of this result is that the performance of LDPC codes under SP
decoding on the BEC is an upper bound of the performance on all MBIOS channels
with the same uncoded bit error probability. All results hold for the more
general multi-edge type LDPC codes.
|
cs/0607021
|
Slepian-Wolf Code Design via Source-Channel Correspondence
|
cs.IT math.IT
|
We consider Slepian-Wolf code design based on LDPC (low-density parity-check)
coset codes for memoryless source-side information pairs. A density evolution
formula, equipped with a concentration theorem, is derived for Slepian- Wolf
coding based on LDPC coset codes. As a consequence, an intimate connection
between Slepian-Wolf coding and channel coding is established. Specifically we
show that, under density evolution, design of binary LDPC coset codes for
Slepian-Wolf coding of an arbitrary memoryless source-side information pair
reduces to design of binary LDPC codes for binary-input output-symmetric
channels without loss of optimality. With this connection, many classic results
in channel coding can be easily translated into the Slepian-Wolf setting.
|
cs/0607024
|
Results on Parity-Check Matrices with Optimal Stopping and/or Dead-End
Set Enumerators
|
cs.IT math.IT
|
The performance of iterative decoding techniques for linear block codes
correcting erasures depends very much on the sizes of the stopping sets
associated with the underlying Tanner graph, or, equivalently, the parity-check
matrix representing the code. In this paper, we introduce the notion of
dead-end sets to explicitly demonstrate this dependency. The choice of the
parity-check matrix entails a trade-off between performance and complexity. We
give bounds on the complexity of iterative decoders achieving optimal
performance in terms of the sizes of the underlying parity-check matrices.
Further, we fully characterize codes for which the optimal stopping set
enumerator equals the weight enumerator.
|
cs/0607027
|
A general computation rule for lossy summaries/messages with examples
from equalization
|
cs.IT math.IT
|
Elaborating on prior work by Minka, we formulate a general computation rule
for lossy messages. An important special case (with many applications in
communications) is the conversion of "soft-bit" messages to Gaussian messages.
By this method, the performance of a Kalman equalizer is improved, both for
uncoded and coded transmission.
|
cs/0607029
|
A Coding Theorem Characterizing Renyi's Entropy through
Variable-to-Fixed Length Codes
|
cs.IT math.IT
|
This paper has been withdrawn
|
cs/0607030
|
Towards a General Theory of Simultaneous Diophantine Approximation of
Formal Power Series: Multidimensional Linear Complexity
|
cs.IT math.IT
|
We model the development of the linear complexity of multisequences by a
stochastic infinite state machine, the Battery-Discharge-Model, BDM. The states
s in S of the BDM have asymptotic probabilities or mass Pr(s)=1/(P(q,M)
q^K(s)), where K(s) in N_0 is the class of the state s, and P(q,M)=\sum_(K
in\N0) P_M(K)q^(-K)=\prod_(i=1..M) q^i/(q^i-1) is the generating function of
the number of partitions into at most M parts. We have (for each timestep
modulo M+1) just P_M(K) states of class K \.
We obtain a closed formula for the asymptotic probability for the linear
complexity deviation d(n) := L(n)-\lceil n\cdot M/(M+1)\rceil with
Pr(d)=O(q^(-|d|(M+1))), for M in N, for d in Z. The precise formula is given in
the text. It has been verified numerically for M=1..8, and is conjectured to
hold for all M in N.
From the asymptotic growth (proven for all M in N), we infer the Law of the
Logarithm for the linear complexity deviation, -liminf_{n\to\infty} d_a(n) /
log n = 1 /((M+1)log q) = limsup_{n\to\infty} d_a(n) / log n, which immediately
yields L_a(n)/n \to M/(M+1) with measure one, for all M in N, a result recently
shown already by Niederreiter and Wang. Keywords: Linear complexity, linear
complexity deviation, multisequence, Battery Discharge Model, isometry.
|
cs/0607037
|
The Minimal Cost Algorithm for Off-Line Diagnosability of Discrete Event
Systems
|
cs.AI cs.CC
|
The failure diagnosis for {\it discrete event systems} (DESs) has been given
considerable attention in recent years. Both on-line and off-line diagnostics
in the framework of DESs was first considered by Lin Feng in 1994, and
particularly an algorithm for diagnosability of DESs was presented. Motivated
by some existing problems to be overcome in previous work, in this paper, we
investigate the minimal cost algorithm for diagnosability of DESs.
More specifically: (i) we give a generic method for judging a system's
off-line diagnosability, and the complexity of this algorithm is
polynomial-time; (ii) and in particular, we present an algorithm of how to
search for the minimal set in all observable event sets, whereas the previous
algorithm may find {\it non-minimal} one.
|
cs/0607039
|
Set-Theoretic Preliminaries for Computer Scientists
|
cs.DM cs.DB
|
The basics of set theory are usually copied, directly or indirectly, by
computer scientists from introductions to mathematical texts. Often
mathematicians are content with special cases when the general case is of no
mathematical interest. But sometimes what is of no mathematical interest is of
great practical interest in computer science. For example, non-binary relations
in mathematics tend to have numerical indexes and tend to be unsorted. In the
theory and practice of relational databases both these simplifications are
unwarranted. In response to this situation we present here an alternative to
the ``set-theoretic preliminaries'' usually found in computer science texts.
This paper separates binary relations from the kind of relations that are
needed in relational databases. Its treatment of functions supports both
computer science in general and the kind of relations needed in databases. As a
sample application this paper shows how the mathematical theory of relations
naturally leads to the relational data model and how the operations on
relations are by themselves already a powerful vehicle for queries.
|
cs/0607042
|
Towards a classical proof of exponential lower bound for 2-probe smooth
codes
|
cs.CR cs.IT math.IT
|
Let C: {0,1}^n -> {0,1}^m be a code encoding an n-bit string into an m-bit
string. Such a code is called a (q, c, e) smooth code if there exists a
decoding algorithm which while decoding any bit of the input, makes at most q
probes on the code word and the probability that it looks at any location is at
most c/m. The error made by the decoding algorithm is at most e. Smooth codes
were introduced by Katz and Trevisan in connection with Locally decodable
codes.
For 2-probe smooth codes Kerenedis and de Wolf have shown exponential in n
lower bound on m in case c and e are constants. Their lower bound proof went
through quantum arguments and interestingly there is no completely classical
argument as yet for the same (albeit completely classical !) statement.
We do not match the bounds shown by Kerenedis and de Wolf but however show
the following. Let C: {0,1}^n -> {0,1}^m be a (2,c,e) smooth code and if e <=
c^2/8n^2, then m >= 2^(n/320c^2 - 1)$. We hope that the arguments and
techniques used in this paper extend (or are helpful in making similar other
arguments), to match the bounds shown using quantum arguments. More so,
hopefully they extend to show bounds for codes with greater number of probes
where quantum arguments unfortunately do not yield good bounds (even for
3-probe codes).
|
cs/0607043
|
Analysis of CDMA systems that are characterized by eigenvalue spectrum
|
cs.IT cond-mat.dis-nn math.IT
|
An approach by which to analyze the performance of the code division multiple
access (CDMA) scheme, which is a core technology used in modern wireless
communication systems, is provided. The approach characterizes the objective
system by the eigenvalue spectrum of a cross-correlation matrix composed of
signature sequences used in CDMA communication, which enables us to handle a
wider class of CDMA systems beyond the basic model reported by Tanaka. The
utility of the novel scheme is shown by analyzing a system in which the
generation of signature sequences is designed for enhancing the orthogonality.
|
cs/0607047
|
PAC Classification based on PAC Estimates of Label Class Distributions
|
cs.LG
|
A standard approach in pattern classification is to estimate the
distributions of the label classes, and then to apply the Bayes classifier to
the estimates of the distributions in order to classify unlabeled examples. As
one might expect, the better our estimates of the label class distributions,
the better the resulting classifier will be. In this paper we make this
observation precise by identifying risk bounds of a classifier in terms of the
quality of the estimates of the label class distributions. We show how PAC
learnability relates to estimates of the distributions that have a PAC
guarantee on their $L_1$ distance from the true distribution, and we bound the
increase in negative log likelihood risk in terms of PAC bounds on the
KL-divergence. We give an inefficient but general-purpose smoothing method for
converting an estimated distribution that is good under the $L_1$ metric into a
distribution that is good under the KL-divergence.
|
cs/0607048
|
Evaluation de Techniques de Traitement des Refus\'{e}s pour l'Octroi de
Cr\'{e}dit
|
cs.NE math.ST stat.TH
|
We present the problem of "Reject Inference" for credit acceptance. Because
of the current legal framework (Basel II), credit institutions need to
industrialize their processes for credit acceptance, including Reject
Inference. We present here a methodology to compare various techniques of
Reject Inference and show that it is necessary, in the absence of real
theoretical results, to be able to produce and compare models adapted to
available data (selection of "best" model conditionnaly on data). We describe
some simulations run on a small data set to illustrate the approach and some
strategies for choosing the control group, which is the only valid approach to
Reject Inference.
|
cs/0607051
|
Raisonner avec des diagrammes : perspectives cognitives et
computationnelles
|
cs.CL
|
Diagrammatic, analogical or iconic representations are often contrasted with
linguistic or logical representations, in which the shape of the symbols is
arbitrary. The aim of this paper is to make a case for the usefulness of
diagrams in inferential knowledge representation systems. Although commonly
used, diagrams have for a long time suffered from the reputation of being only
a heuristic tool or a mere support for intuition. The first part of this paper
is an historical background paying tribute to the logicians, psychologists and
computer scientists who put an end to this formal prejudice against diagrams.
The second part is a discussion of their characteristics as opposed to those of
linguistic forms. The last part is aimed at reviving the interest for
heterogeneous representation systems including both linguistic and diagrammatic
representations.
|
cs/0607052
|
Dealing with Metonymic Readings of Named Entities
|
cs.AI cs.CL
|
The aim of this paper is to propose a method for tagging named entities (NE),
using natural language processing techniques. Beyond their literal meaning,
named entities are frequently subject to metonymy. We show the limits of
current NE type hierarchies and detail a new proposal aiming at dynamically
capturing the semantics of entities in context. This model can analyze complex
linguistic phenomena like metonymy, which are known to be difficult for natural
language processing but crucial for most applications. We present an
implementation and some test using the French ESTER corpus and give significant
results.
|
cs/0607053
|
Linguistically Grounded Models of Language Change
|
cs.AI cs.CL
|
Questions related to the evolution of language have recently known an
impressive increase of interest (Briscoe, 2002). This short paper aims at
questioning the scientific status of these models and their relations to
attested data. We show that one cannot directly model non-linguistic factors
(exogenous factors) even if they play a crucial role in language evolution. We
then examine the relation between linguistic models and attested language data,
as well as their contribution to cognitive linguistics.
|
cs/0607056
|
Reasoning with Intervals on Granules
|
cs.AI cs.DM
|
The formalizations of periods of time inside a linear model of Time are
usually based on the notion of intervals, that may contain or may not their
endpoints. This is not enought when the periods are written in terms of coarse
granularities with respect to the event taken into account. For instance, how
to express the inter-war period in terms of a {\em years} interval? This paper
presents a new type of intervals, neither open, nor closed or open-closed and
the extension of operations on intervals of this new type, in order to reduce
the gap between the discourse related to temporal relationship and its
translation into a discretized model of Time.
|
cs/0607060
|
Circle Formation of Weak Mobile Robots
|
cs.RO
|
In this paper we prove the conjecture of D\'{e}fago & Konagaya. Furthermore,
we describe a deterministic protocol for forming a regular n-gon in finite
time.
|
cs/0607062
|
Get out the vote: Determining support or opposition from Congressional
floor-debate transcripts
|
cs.CL cs.SI physics.soc-ph
|
We investigate whether one can determine from the transcripts of U.S.
Congressional floor debates whether the speeches represent support of or
opposition to proposed legislation. To address this problem, we exploit the
fact that these speeches occur as part of a discussion; this allows us to use
sources of information regarding relationships between discourse segments, such
as whether a given utterance indicates agreement with the opinion expressed by
another. We find that the incorporation of such information yields substantial
improvements over classifying speeches in isolation.
|
cs/0607064
|
How to Find Good Finite-Length Codes: From Art Towards Science
|
cs.IT math.IT
|
We explain how to optimize finite-length LDPC codes for transmission over the
binary erasure channel. Our approach relies on an analytic approximation of the
erasure probability. This is in turn based on a finite-length scaling result to
model large scale erasures and a union bound involving minimal stopping sets to
take into account small error events. We show that the performances of
optimized ensembles as observed in simulations are well described by our
approximation. Although we only address the case of transmission over the
binary erasure channel, our method should be applicable to a more general
setting.
|
cs/0607065
|
Decomposable Theories
|
cs.LO cs.AI
|
We present in this paper a general algorithm for solving first-order formulas
in particular theories called "decomposable theories". First of all, using
special quantifiers, we give a formal characterization of decomposable theories
and show some of their properties. Then, we present a general algorithm for
solving first-order formulas in any decomposable theory "T". The algorithm is
given in the form of five rewriting rules. It transforms a first-order formula
"P", which can possibly contain free variables, into a conjunction "Q" of
solved formulas easily transformable into a Boolean combination of
existentially quantified conjunctions of atomic formulas. In particular, if "P"
has no free variables then "Q" is either the formula "true" or "false". The
correctness of our algorithm proves the completeness of the decomposable
theories.
Finally, we show that the theory "Tr" of finite or infinite trees is a
decomposable theory and give some benchmarks realized by an implementation of
our algorithm, solving formulas on two-partner games in "Tr" with more than 160
nested alternated quantifiers.
|
cs/0607067
|
Competing with stationary prediction strategies
|
cs.LG
|
In this paper we introduce the class of stationary prediction strategies and
construct a prediction algorithm that asymptotically performs as well as the
best continuous stationary strategy. We make mild compactness assumptions but
no stochastic assumptions about the environment. In particular, no assumption
of stationarity is made about the environment, and the stationarity of the
considered strategies only means that they do not depend explicitly on time; we
argue that it is natural to consider only stationary strategies even for highly
non-stationary environments.
|
cs/0607068
|
Computation of the Weight Distribution of CRC Codes
|
cs.IT math.AC math.IT
|
In this article, we illustrate an algorithm for the computation of the weight
distribution of CRC codes. The recursive structure of CRC codes will give us an
iterative way to compute the weight distribution of their dual codes starting
from just some ``representative'' words. Thanks to MacWilliams Theorem, the
computation of the weight distribution of dual codes can be easily brought back
to that of CRC codes. This algorithm is a good alternative to the standard
algorithm that involves listing every word of the code.
|
cs/0607071
|
Islands for SAT
|
cs.AI
|
In this note we introduce the notion of islands for restricting local search.
We show how we can construct islands for CNF SAT problems, and how much search
space can be eliminated by restricting search to the island.
|
cs/0607074
|
On Construction of the (24,12,8) Golay Codes
|
cs.IT math.IT
|
Two product array codes are used to construct the (24, 12, 8) binary Golay
code through the direct sum operation. This construction provides a systematic
way to find proper (8, 4, 4) linear block component codes for generating the
Golay code, and it generates and extends previously existing methods that use a
similar construction framework. The code constructed is simple to decode.
|
cs/0607075
|
On entropy for mixtures of discrete and continuous variables
|
cs.IT math.IT
|
Let $X$ be a discrete random variable with support $S$ and $f : S \to
S^\prime$ be a bijection. Then it is well-known that the entropy of $X$ is the
same as the entropy of $f(X)$. This entropy preservation property has been
well-utilized to establish non-trivial properties of discrete stochastic
processes, e.g. queuing process \cite{prg03}. Entropy as well as entropy
preservation is well-defined only in the context of purely discrete or
continuous random variables. However for a mixture of discrete and continuous
random variables, which arise in many interesting situations, the notions of
entropy and entropy preservation have not been well understood.
In this paper, we extend the notion of entropy in a natural manner for a
mixed-pair random variable, a pair of random variables with one discrete and
the other continuous. Our extensions are consistent with the existing
definitions of entropy in the sense that there exist natural injections from
discrete or continuous random variables into mixed-pair random variables such
that their entropy remains the same. This extension of entropy allows us to
obtain sufficient conditions for entropy preservation in mixtures of discrete
and continuous random variables under bijections.
The extended definition of entropy leads to an entropy rate for continuous
time Markov chains. As an application, we recover a known probabilistic result
related to Poisson process. We strongly believe that the frame-work developed
in this paper can be useful in establishing probabilistic properties of complex
processes, such as load balancing systems, queuing network, caching algorithms.
|
cs/0607076
|
Capacity of Cooperative Fusion in the Presence of Byzantine Sensors
|
cs.IT math.IT
|
The problem of cooperative fusion in the presence of Byzantine sensors is
considered. An information theoretic formulation is used to characterize the
Shannon capacity of sensor fusion. It is shown that when less than half of the
sensors are Byzantine, the effect of Byzantine attack can be entirely
mitigated, and the fusion capacity is identical to that when all sensors are
honest. But when at least half of the sensors are Byzantine, they can
completely defeat the sensor fusion so that no information can be transmitted
reliably. A capacity achieving transmit-then-verify strategy is proposed for
the case that less than half of the sensors are Byzantine, and its error
probability and coding rate is analyzed by using a Markov decision process
modeling of the transmission protocol.
|
cs/0607078
|
Complex Lattice Reduction Algorithm for Low-Complexity MIMO Detection
|
cs.DS cs.IT math.IT
|
Recently, lattice-reduction-aided detectors have been proposed for
multiple-input multiple-output (MIMO) systems to give performance with full
diversity like maximum likelihood receiver, and yet with complexity similar to
linear receivers. However, these lattice-reduction-aided detectors are based on
the traditional LLL reduction algorithm that was originally introduced for
reducing real lattice bases, in spite of the fact that the channel matrices are
inherently complex-valued. In this paper, we introduce the complex LLL
algorithm for direct application to reduce the basis of a complex lattice which
is naturally defined by a complex-valued channel matrix. We prove that complex
LLL reduction-aided detection can also achieve full diversity. Our analysis
reveals that the new complex LLL algorithm can achieve a reduction in
complexity of nearly 50% over the traditional LLL algorithm, and this is
confirmed by simulation. It is noteworthy that the complex LLL algorithm
aforementioned has nearly the same bit-error-rate performance as the
traditional LLL algorithm.
|
cs/0607081
|
Syst\`{e}me de repr\'{e}sentation d'aide au besoin dans le domaine
architectural
|
cs.OH cs.IR
|
The image is a very important mean of communication in the field of
architectural who intervenes in the various phases of the design of a project.
It can be regarded as a tool of decision-making aid. The study of our research
aims at to see the contribution of the Economic Intelligence in the resolution
of a decisional problem of the various partners (Architect, Contractor,
Customer) in the architectural field, in order to make strategic decisions
within the framework of the realization or design of an architectural work. The
economic Intelligence allows the taking into account of the real needs for the
user-decision makers, so that their waiting are considered at the first stage
of a search for information and not in the final stage of the development of
the tool in the evaluation of this last.
|
cs/0607083
|
Mathematical Modelling of the Thermal Accumulation in Hot Water Solar
Systems
|
cs.CE
|
Mathematical modelling and defining useful recommendations for construction
and regimes of exploitation for hot water solar installation with thermal
stratification is the main purpose of this work. A special experimental solar
module for hot water was build and equipped with sufficient measure apparatus.
The main concept of investigation is to optimise the stratified regime of
thermal accumulation and constructive parameters of heat exchange equipment
(heat serpentine in tank). Accumulation and heat exchange processes were
investigated by theoretical end experimental means. Special mathematical model
was composed to simulate the energy transfer in stratified tank. Computer
program was developed to solve mathematical equations for thermal accumulation
and energy exchange. Extensive numerical and experimental tests were carried
out. A good correspondence between theoretical and experimental data was
arrived. Keywords: Mathematical modelling, accumulation
|
cs/0607084
|
About Norms and Causes
|
cs.AI
|
Knowing the norms of a domain is crucial, but there exist no repository of
norms. We propose a method to extract them from texts: texts generally do not
describe a norm, but rather how a state-of-affairs differs from it. Answers
concerning the cause of the state-of-affairs described often reveal the
implicit norm. We apply this idea to the domain of driving, and validate it by
designing algorithms that identify, in a text, the "basic" norms to which it
refers implicitly.
|
cs/0607085
|
Using Pseudo-Stochastic Rational Languages in Probabilistic Grammatical
Inference
|
cs.LG
|
In probabilistic grammatical inference, a usual goal is to infer a good
approximation of an unknown distribution P called a stochastic language. The
estimate of P stands in some class of probabilistic models such as
probabilistic automata (PA). In this paper, we focus on probabilistic models
based on multiplicity automata (MA). The stochastic languages generated by MA
are called rational stochastic languages; they strictly include stochastic
languages generated by PA; they also admit a very concise canonical
representation. Despite the fact that this class is not recursively enumerable,
it is efficiently identifiable in the limit by using the algorithm DEES,
introduced by the authors in a previous paper. However, the identification is
not proper and before the convergence of the algorithm, DEES can produce MA
that do not define stochastic languages. Nevertheless, it is possible to use
these MA to define stochastic languages. We show that they belong to a broader
class of rational series, that we call pseudo-stochastic rational languages.
The aim of this paper is twofold. First we provide a theoretical study of
pseudo-stochastic rational languages, the languages output by DEES, showing for
example that this class is decidable within polynomial time. Second, we have
carried out a lot of experiments in order to compare DEES to classical
inference algorithms such as ALERGIA and MDI. They show that DEES outperforms
them in most cases.
|
cs/0607086
|
Representing Knowledge about Norms
|
cs.AI
|
Norms are essential to extend inference: inferences based on norms are far
richer than those based on logical implications. In the recent decades, much
effort has been devoted to reason on a domain, once its norms are represented.
How to extract and express those norms has received far less attention.
Extraction is difficult: as the readers are supposed to know them, the norms of
a domain are seldom made explicit. For one thing, extracting norms requires a
language to represent them, and this is the topic of this paper. We apply this
language to represent norms in the domain of driving, and show that it is
adequate to reason on the causes of accidents, as described by car-crash
reports.
|
cs/0607088
|
Using Answer Set Programming in an Inference-Based approach to Natural
Language Semantics
|
cs.CL cs.AI
|
Using Answer Set Programming in an Inference-Based approach to Natural
Language Semantics
|
cs/0607089
|
Superregular Matrices and the Construction of Convolutional Codes having
a Maximum Distance Profile
|
cs.IT math.CO math.IT
|
Superregular matrices are a class of lower triangular Toeplitz matrices that
arise in the context of constructing convolutional codes having a maximum
distance profile. These matrices are characterized by the property that no
submatrix has a zero determinant unless it is trivially zero due to the lower
triangular structure. In this paper, we discuss how superregular matrices may
be used to construct codes having a maximum distance profile. We also introduce
group actions that preserve the superregularity property and present an upper
bound on the minimum size a finite field must have in order that a superregular
matrix of a given size can exist over that field.
|
cs/0607090
|
Neural Networks with Complex and Quaternion Inputs
|
cs.NE
|
This article investigates Kak neural networks, which can be instantaneously
trained, for complex and quaternion inputs. The performance of the basic
algorithm has been analyzed and shown how it provides a plausible model of
human perception and understanding of images. The motivation for studying
quaternion inputs is their use in representing spatial rotations that find
applications in computer graphics, robotics, global navigation, computer vision
and the spatial orientation of instruments. The problem of efficient mapping of
data in quaternion neural networks is examined. Some problems that need to be
addressed before quaternion neural networks find applications are identified.
|
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