node_id int64 0 76.9k | label int64 0 39 | text stringlengths 13 124k | neighbors listlengths 0 3.32k | mask stringclasses 4
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|---|---|---|---|---|
2,394 | 2 | Title: A Comparison of Dynamic Reposing and Tangent Distance for Drug Activity Prediction
Abstract: In drug activity prediction (as in handwritten character recognition), the features extracted to describe a training example depend on the pose (location, orientation, etc.) of the example. In handwritten character recognition, one of the best techniques for addressing this problem is the tangent distance method of Simard, LeCun and Denker (1993). Jain, et al. (1993a; 1993b) introduce a new technique|dynamic reposing|that also addresses this problem. Dynamic reposing iteratively learns a neural network and then reposes the examples in an effort to maximize the predicted output values. New models are trained and new poses computed until models and poses converge. This paper compares dynamic reposing to the tangent distance method on the task of predicting the biological activity of musk compounds. In a 20-fold cross-validation, | [
2427
] | Train |
2,395 | 0 | Title: Improving Competence by Integrating Case-Based Reasoning and Heuristic Search
Abstract: We analyse the behaviour of a Propose & Revise architecture in the VT elevator design problem and we show that this problem solving method cannot solve all possible cases covered by the available domain knowledge. We investigate this problem and we show that this limitation is caused by the restricted search regime employed by the method and that the competence of the method cannot be improved by acquiring additional domain knowledge. We therefore propose an alternative design problem solver, which integrates case-based reasoning and heuristic search techniques and overcomes the competence-related limitations exhibited by the Propose & Revise architecture, while maintaining the same level of efficiency. We describe four algorithms for case-based design, which exploit both general properties of parametric design tasks and application specific heuristic knowledge. | [
2665
] | Train |
2,396 | 1 | Title: Properties of Genetic Representations of Neural Architectures
Abstract: Genetic algorithms and related evolutionary techniques offer a promising approach for automatically exploring the design space of neural architectures for artificial intelligence and cognitive modeling. Central to this process of evolutionary design of neural architectures (EDNA) is the choice of the representation scheme that is used to encode a neural architecture in the form of a gene string (genotype) and to decode a genotype into the corresponding neural architecture (phenotype). The representation scheme used not only constrains the class of neural architectures that are representable (evolvable) in the system, but also determines the efficiency and the time-space complexity of the evolutionary design procedure as a whole. This paper identifies and discusses a set of properties that can be used to characterize different representations used in EDNA and to design or select representations with the necessary properties for particular classes of applications. | [
163,
503,
1583,
1952,
2563
] | Test |
2,397 | 2 | Title: CuPit-2 A Parallel Language for Neural Algorithms: Language Reference and Tutorial
Abstract: and load balancing even for irregular neural networks. The idea to achieve these goals lies in the programming model: CuPit-2 programs are object-centered, with connections and nodes of a graph (which is the neural network) being the objects. Algorithms are based on parallel local computations in the nodes and connections and communication along the connections (plus broadcast and reduction operations). This report describes the design considerations and the resulting language definition and discusses in detail a tutorial example program. This CuPit-2 language manual and tutorial is an updated version of the original CuPit language manual [Pre94]. The new language CuPit-2 differs from the original CuPit in several ways. All language changes from CuPit to CuPit-2 are listed in the appendix. | [
2203,
2405
] | Train |
2,398 | 0 | Title: Issues in Goal-Driven Explanation
Abstract: When a reasoner explains surprising events for its internal use, a key motivation for explaining is to perform learning that will facilitate the achievement of its goals. Human explainers use a range of strategies to build explanations, including both internal reasoning and external information search, and goal-based considerations have a profound effect on their choices of when and how to pursue explanations. However, standard AI models of explanation rely on goal-neutral use of a single fixed strategy|generally backwards chaining|to build their explanations. This paper argues that explanation should be modeled as a goal-driven learning process for gathering and transforming information, and discusses the issues involved in developing an active multi-strategy process for goal-driven explanation. | [
583,
1498,
2184,
2372,
2399
] | Test |
2,399 | 0 | Title: Abduction, Experience, and Goals: A Model of Everyday Abductive Explanation*
Abstract: When a reasoner explains surprising events for its internal use, a key motivation for explaining is to perform learning that will facilitate the achievement of its goals. Human explainers use a range of strategies to build explanations, including both internal reasoning and external information search, and goal-based considerations have a profound effect on their choices of when and how to pursue explanations. However, standard AI models of explanation rely on goal-neutral use of a single fixed strategy|generally backwards chaining|to build their explanations. This paper argues that explanation should be modeled as a goal-driven learning process for gathering and transforming information, and discusses the issues involved in developing an active multi-strategy process for goal-driven explanation. | [
136,
2398,
2626
] | Train |
2,400 | 2 | Title: A Neural Network Model of Visual Tilt Aftereffects
Abstract: RF-LISSOM, a self-organizing model of laterally connected orientation maps in the primary visual cortex, was used to study the psychological phenomenon known as the tilt aftereffect. The same self-organizing processes that are responsible for the long-term development of the map and its lateral connections are shown to result in tilt aftereffects over short time scales in the adult. The model allows observing large numbers of neurons and connections simultaneously, making it possible to relate higher-level phenomena to low-level events, which is difficult to do experimentally. The results give computational support for the idea that direct tilt aftereffects arise from adaptive lateral interactions between feature detectors, as has long been surmised. They also suggest that indirect effects could result from the conservation of synaptic resources during this process. The model thus provides a unified computational explanation of self-organization and both direct and indirect tilt aftereffects in the primary visual cortex. | [
122,
124,
127,
1916
] | Train |
2,401 | 3 | Title: Factor Graphs and Algorithms
Abstract: A factor graph is a bipartite graph that expresses how a global function of several variables factors into a product of local functions. Factor graphs subsume many other graphical models, including Bayesian networks, Markov random fields, and Tanner graphs. We describe a general algorithm for computing "marginals" of the global function by distributed message-passing in the corresponding factor graph. A wide variety of algorithms developed in the artificial intelligence, statistics, signal processing, and digital communications communities can be derived as specific instances of this general algorithm, including Pearl's "belief propagation" and "belief revision" algorithms, the fast Fourier transform, the Viterbi algorithm, the forward/backward algorithm, and the iterative "turbo" decoding algorithm. | [
1988
] | Test |
2,402 | 1 | Title: Evolution of a Time-Optimal Fly-To Controller Circuit using Genetic Programming
Abstract: | [
1921,
1931
] | Train |
2,403 | 0 | Title: Reasoning with Portions of Precedents
Abstract: This paper argues that the task of matching in case-based reasoning can often be improved by comparing new cases to portions of precedents. An example is presented that illustrates how combining portions of multiple precedents can permit new cases to be resolved that would be indeterminate if new cases could only be compared to entire precedents. A system that uses of portions of precedents for legal analysis in the domain of Texas worker's compensation law, GREBE, is described, and examples of GREBE's analysis that combine reasoning steps from multiple precedents are presented. | [
649,
2581
] | Train |
2,404 | 3 | Title: A Model for Projection and Action
Abstract: In designing autonomous agents that deal competently with issues involving time and space, there is a tradeoff to be made between guaranteed response-time reactions on the one hand, and flexibility and expressiveness on the other. We propose a model of action with probabilistic reasoning and decision analytic evaluation for use in a layered control architecture. Our model is well suited to tasks that require reasoning about the interaction of behaviors and events in a fixed temporal horizon. Decisions are continuously reevaluated, so that there is no problem with plans becoming obsolete as new information becomes available. In this paper, we are particularly interested in the tradeoffs required to guarantee a fixed reponse time in reasoning about nondeterministic cause-and- effect relationships. By exploiting approximate decision making processes, we are able to trade accuracy in our predictions for speed in decision making in order to improve expected per | [
1459,
2221
] | Train |
2,405 | 2 | Title: A Parallel Programming Model for Irregular Dynamic Neural Networks a programming model that allows to
Abstract: A compiler for CuPit has been built for the MasPar MP-1/MP-2 using compilation techniques that can also be applied to most other parallel machines. The paper shortly presents the main ideas of the techniques used and results obtained by the various optimizations. | [
881,
1119,
2203,
2397
] | Validation |
2,406 | 4 | Title: Approximating Value Trees in Structured Dynamic Programming
Abstract: We propose and examine a method of approximate dynamic programming for Markov decision processes based on structured problem representations. We assume an MDP is represented using a dynamic Bayesian network, and construct value functions using decision trees as our function representation. The size of the representation is kept within acceptable limits by pruning these value trees so that leaves represent possible ranges of values, thus approximating the value functions produced during optimization. We propose a method for detecting convergence, prove errors bounds on the resulting approximately optimal value functions and policies, and describe some preliminary experi mental results. | [
2078
] | Validation |
2,407 | 1 | Title: Evolving Turing-Complete Programs for a Register Machine with Self-modifying Code
Abstract: The majority of commercial computers today are register machines of von Neumann type. We have developed a method to evolve Turing-complete programs for a register machine. The described implementation enables the use of most program constructs, such as arithmetic operators, large indexed memory, automatic decomposition into subfunctions and subroutines (ADFs), conditional constructs i.e. if-then-else, jumps, loop structures, recursion, protected functions, string and list functions. Any C-function can be compiled and linked into the function set of the system. The use of register machine language allows us to work at the lowest level of binary machine code without any interpreting steps. In a von Neumann machine, programs and data reside in the same memory and the genetic operators can thus directly manipulate the binary machine code in memory. The genetic operators themselves are written in C-language but they modify individuals in binary representation. The result is an execution speed enhancement of up to 100 times compared to an interpreting C-language implementation, and up to 2000 times compared to a LISP implementation. The use of binary machine code demands a very compact coding of about one byte per node in the individual. The resulting evolved programs are disassembled into C-modules and can be incorporated into a conventional software development environment. The low memory requirements and the significant speed enhancement of this technique could be of use when applying genetic programming to new application areas, platforms and research domains. | [
1631,
2704
] | Test |
2,408 | 4 | Title: Exploratory Learning in the Game of GO
Abstract: This paper considers the importance of exploration to game-playing programs which learn by playing against opponents. The central question is whether a learning program should play the move which offers the best chance of winning the present game, or if it should play the move which has the best chance of providing useful information for future games. An approach to addressing this question is developed using probability theory, and then implemented in two different learning methods. Initial experiments in the game of Go suggest that a program which takes exploration into account can learn better against a knowledgeable opponent than a program which does not. | [
523,
1975,
2145
] | Train |
2,409 | 2 | Title: Framework for Combining Symbolic and Neural Learning rule extraction from neural networks the KBANN algorithm
Abstract: Technical Report 1123, Computer Sciences Department, University of Wisconsin - Madison, Nov. 1992 ABSTRACT This article describes an approach to combining symbolic and connectionist approaches to machine learning. A three-stage framework is presented and the research of several groups is reviewed with respect to this framework. The first stage involves the insertion of symbolic knowledge into neural networks, the second addresses the refinement of this prior knowledge in its neural representation, while the third concerns the extraction of the refined symbolic knowledge. Experimental results and open research issues are discussed. A shorter version of this paper will appear in Machine Learning. | [
174,
477,
638,
1644,
1869,
2027,
2543,
2672
] | Train |
2,410 | 2 | Title: Subsymbolic Case-Role Analysis of Sentences with Embedded Clauses
Abstract: A distributed neural network model called SPEC for processing sentences with recursive relative clauses is described. The model is based on separating the tasks of segmenting the input word sequence into clauses, forming the case-role representations, and keeping track of the recursive embeddings into different modules. The system needs to be trained only with the basic sentence constructs, and it generalizes not only to new instances of familiar relative clause structures, but to novel structures as well. SPEC exhibits plausible memory degradation as the depth of the center embeddings increases, its memory is primed by earlier constituents, and its performance is aided by semantic constraints between the constituents. The ability to process structure is largely due to a central executive network that monitors and controls the execution of the entire system. This way, in contrast to earlier subsymbolic systems, parsing is modeled as a controlled high-level process rather than one based on automatic reflex responses. | [
204,
1811,
2049
] | Validation |
2,411 | 4 | Title: Predictive Q-Routing: A Memory-based Reinforcement Learning Approach to Adaptive Traffic Control
Abstract: In this paper, we propose a memory-based Q-learning algorithm called predictive Q-routing (PQ-routing) for adaptive traffic control. We attempt to address two problems encountered in Q-routing (Boyan & Littman, 1994), namely, the inability to fine-tune routing policies under low network load and the inability to learn new optimal policies under decreasing load conditions. Unlike other memory-based reinforcement learning algorithms in which memory is used to keep past experiences to increase learning speed, PQ-routing keeps the best experiences learned and reuses them by predicting the traffic trend. The effectiveness of PQ-routing has been verified under various network topologies and traffic conditions. Simulation results show that PQ-routing is superior to | [
2666
] | Train |
2,412 | 4 | Title: On-Line Adaptation of a Signal Predistorter through Dual Reinforcement Learning
Abstract: Several researchers have demonstrated how neural networks can be trained to compensate for nonlinear signal distortion in e.g. digital satellite communications systems. These networks, however, require that both the original signal and its distorted version are known. Therefore, they have to be trained off-line, and they cannot adapt to changing channel characteristics. In this paper, a novel dual reinforcement learning approach is proposed that can adapt on-line while the system is performing. Assuming that the channel characteristics are the same in both directions, two predistorters at each end of the communication channel co-adapt using the output of the other predistorter to determine their own reinforcement. Using the common Volterra Series model to simulate the channel, the system is shown to successfully learn to compensate for distortions up to 30%, which is significantly higher than what might be expected in an actual channel. | [
427,
1758,
2255
] | Train |
2,413 | 2 | Title: On-Line Adaptation of a Signal Predistorter through Dual Reinforcement Learning
Abstract: Most connectionist modeling assumes noise-free inputs. This assumption is often violated. This paper introduces the idea of clearning, of simultaneously cleaning the data and learning the underlying structure. The cleaning step can be viewed as top-down processing (where the model modifies the data), and the learning step can be viewed as bottom-up processing (where the data modifies the model). Clearning is used in conjunction with standard pruning. This paper discusses the statistical foundation of clearning, gives an interpretation in terms of a mechanical model, describes how to obtain both point predictions and conditional densities for the output, and shows how the resulting model can be used to discover properties of the data otherwise not accessible (such as the signal-to-noise ratio of the inputs). This paper uses clearning to predict foreign exchange rates, a noisy time series problem with well-known benchmark performances. On the out-of-sample 1993-1994 test period, clearning obtains an annualized return on investment above 30%, significantly better than an otherwise identical network. The final ultra-sparse network with 36 remaining non-zero input-to-hidden weights (of the 1035 initial weights between 69 inputs and 15 hidden units) is very robust against overfitting. This small network also lends itself to interpretation. | [
668,
1366,
1718,
2239,
2373
] | Train |
2,414 | 2 | Title: On-Line Adaptation of a Signal Predistorter through Dual Reinforcement Learning
Abstract: Most connectionist modeling assumes noise-free inputs. This assumption is often violated. This paper introduces the idea of clearning, of simultaneously cleaning the data and learning the underlying structure. The cleaning step can be viewed as top-down processing (where the model modifies the data), and the learning step can be viewed as bottom-up processing (where the data modifies the model). Clearning is used in conjunction with standard pruning. This paper discusses the statistical foundation of clearning, gives an interpretation in terms of a mechanical model, describes how to obtain both point predictions and conditional densities for the output, and shows how the resulting model can be used to discover properties of the data otherwise not accessible (such as the signal-to-noise ratio of the inputs). This paper uses clearning to predict foreign exchange rates, a noisy time series problem with well-known benchmark performances. On the out-of-sample 1993-1994 test period, clearning obtains an annualized return on investment above 30%, significantly better than an otherwise identical network. The final ultra-sparse network with 36 remaining non-zero input-to-hidden weights (of the 1035 initial weights between 69 inputs and 15 hidden units) is very robust against overfitting. This small network also lends itself to interpretation. | [
668,
1366,
1718,
2239,
2373
] | Test |
2,415 | 0 | Title: LEARNING MORE FROM LESS DATA: EXPERIMENTS WITH LIFELONG ROBOT LEARNING
Abstract: Most connectionist modeling assumes noise-free inputs. This assumption is often violated. This paper introduces the idea of clearning, of simultaneously cleaning the data and learning the underlying structure. The cleaning step can be viewed as top-down processing (where the model modifies the data), and the learning step can be viewed as bottom-up processing (where the data modifies the model). Clearning is used in conjunction with standard pruning. This paper discusses the statistical foundation of clearning, gives an interpretation in terms of a mechanical model, describes how to obtain both point predictions and conditional densities for the output, and shows how the resulting model can be used to discover properties of the data otherwise not accessible (such as the signal-to-noise ratio of the inputs). This paper uses clearning to predict foreign exchange rates, a noisy time series problem with well-known benchmark performances. On the out-of-sample 1993-1994 test period, clearning obtains an annualized return on investment above 30%, significantly better than an otherwise identical network. The final ultra-sparse network with 36 remaining non-zero input-to-hidden weights (of the 1035 initial weights between 69 inputs and 15 hidden units) is very robust against overfitting. This small network also lends itself to interpretation. | [
1112,
2530
] | Train |
2,416 | 3 | Title: Wavelet Thresholding via a Bayesian Approach
Abstract: We discuss a Bayesian formalism which gives rise to a type of wavelet threshold estimation in non-parametric regression. A prior distribution is imposed on the wavelet coefficients of the unknown response function, designed to capture the sparseness of wavelet expansion common to most applications. For the prior specified, the posterior median yields a thresholding procedure. Our prior model for the underlying function can be adjusted to give functions falling in any specific Besov space. We establish a relation between the hyperparameters of the prior model and the parameters of those Besov spaces within which realizations from the prior will fall. Such a relation gives insight into the meaning of the Besov space parameters. Moreover, the established relation makes it possible in principle to incorporate prior knowledge about the function's regularity properties into the prior model for its wavelet coefficients. However, prior knowledge about a function's regularity properties might be hard to elicit; with this in mind, we propose a standard choise of prior hyperparameters that works well in our examples. Several simulated examples are used to illustrate our method, and comparisons are made with other thresholding methods. We also present an application to a data set collected in an anaesthesiological study. | [
1910,
2375,
2506
] | Train |
2,417 | 3 | Title: Choice of Basis for Laplace Approximation
Abstract: Maximum a posteriori optimization of parameters and the Laplace approximation for the marginal likelihood are both basis-dependent methods. This note compares two choices of basis for models parameterized by probabilities, showing that it is possible to improve on the traditional choice, the probability simplex, by transforming to the `softmax' basis. | [
157,
2532
] | Train |
2,418 | 6 | Title: A Fast Algorithm for the Computation and Enumeration of Perfect Phylogenies
Abstract: The Perfect Phylogeny Problem is a classical problem in computational evolutionary biology, in which a set of species/taxa is described by a set of qualitative characters. In recent years, the problem has been shown to be NP-Complete in general, while the different fixed parameter versions can each be solved in polynomial time. In particular, Agarwala and Fernandez-Baca have developed an O(2 3r (nk 3 +k 4 )) algorithm for the perfect phylogeny problem for n species defined by k r-state characters. Since commonly the character data is drawn from alignments of molecular sequences, k is the length of the sequences and can thus be very large (in the hundreds or thousands). Thus, it is imperative to develop algorithms which run efficiently for large values of k. In this paper we make additional observations about the structure of the problem and produce an algorithm for the problem that runs in time O(2 2r k 2 n). We also show how it is possible to efficiently build a structure that implicitly represents the set of all perfect phylogenies, and to randomly sample from that set. | [
2141,
2345,
2511
] | Test |
2,419 | 3 | Title: Adaptive probabilistic networks
Abstract: Belief networks (or probabilistic networks) and neural networks are two forms of network representations that have been used in the development of intelligent systems in the field of artificial intelligence. Belief networks provide a concise representation of general probability distributions over a set of random variables, and facilitate exact calculation of the impact of evidence on propositions of interest. Neural networks, which represent parameterized algebraic combinations of nonlinear activation functions, have found widespread use as models of real neural systems and as function approximators because of their amenability to simple training algorithms. Furthermore, the simple, local nature of most neural network training algorithms provides a certain biological plausibility and allows for a massively parallel implementation. In this paper, we show that similar local learning algorithms can be derived for belief networks, and that these learning algorithms can operate using only information that is directly available from the normal, inferential processes of the networks. This removes the main obstacle preventing belief networks from competing with neural networks on the above-mentioned tasks. The precise, local, probabilistic interpretation of belief networks also allows them to be partially or wholly constructed by humans; allows the results of learning to be easily understood; and allows them to contribute to rational decision-making in a well-defined way. | [
492,
1268,
2323
] | Validation |
2,420 | 3 | Title: A Parallel Learning Algorithm for Bayesian Inference Networks
Abstract: We present a new parallel algorithm for learning Bayesian inference networks from data. Our learning algorithm exploits both properties of the MDL-based score metric, and a distributed, asynchronous, adaptive search technique called nagging. Nagging is intrinsically fault tolerant, has dynamic load balancing features, and scales well. We demonstrate the viability, effectiveness, and scalability of our approach empirically with several experiments using on the order of 20 machines. More specifically, we show that our distributed algorithm can provide optimal solutions for larger problems as well as good solutions for Bayesian networks of up to 150 variables. | [
1527,
2169
] | Train |
2,421 | 3 | Title: On Convergence of the EM Algorithm and the Gibbs Sampler SUMMARY
Abstract: In this article we investigate the relationship between the two popular algorithms, the EM algorithm and the Gibbs sampler. We show that the approximate rate of convergence of the Gibbs sampler by Gaussian approximation is equal to that of the corresponding EM type algorithm. This helps in implementing either of the algorithms as improvement strategies for one algorithm can be directly transported to the other. In particular, by running the EM algorithm we know approximately how many iterations are needed for convergence of the Gibbs sampler. We also obtain a result that under conditions, the EM algorithm used for finding the maximum likelihood estimates can be slower to converge than the corresponding Gibbs sampler for Bayesian inference which uses proper prior distributions. We illustrate our results in a number of realistic examples all based on the generalized linear mixed models. | [
74,
115,
263,
345,
1829,
1856,
1868,
1906,
2266,
2389,
2590,
2654
] | Validation |
2,422 | 2 | Title: Classification of Underwater Mammals using Feature Extraction Based on Time-Frequency Analysis and BCM Theory
Abstract: Underwater mammal sound classification is demonstrated using a novel application of wavelet time/frequency decomposition and feature extraction using a BCM unsupervised network. Different feature extraction methods and different wavelet representations are studied. The system achieves outstanding classification performance even when tested with mammal sounds recorded at very different locations (from those used for training). The improved results suggest that nonlinear feature extraction from wavelet representations outperforms different linear choices of basis functions. | [
359,
2376,
2499,
2500
] | Train |
2,423 | 6 | Title: Error-Correcting Output Codes: A General Method for Improving Multiclass Inductive Learning Programs
Abstract: Multiclass learning problems involve finding a definition for an unknown function f(x) whose range is a discrete set containing k > 2 values (i.e., k "classes"). The definition is acquired by studying large collections of training examples of the form hx i ; f(x i )i. Existing approaches to this problem include (a) direct application of multiclass algorithms such as the decision-tree algorithms ID3 and CART, (b) application of binary concept learning algorithms to learn individual binary functions for each of the k classes, and (c) application of binary concept learning algorithms with distributed output codes such as those employed by Sejnowski and Rosenberg in the NETtalk system. This paper compares these three approaches to a new technique in which BCH error-correcting codes are employed as a distributed output representation. We show that these output representations improve the performance of ID3 on the NETtalk task and of backpropagation on an isolated-letter speech-recognition task. These results demonstrate that error-correcting output codes provide a general-purpose method for improving the performance of inductive learning programs on multiclass problems. | [
550,
853,
862,
881,
1161,
1191,
1601,
1644,
1732,
2225,
2627,
2657
] | Test |
2,424 | 5 | Title: Which Hypotheses Can Be Found with Inverse Entailment? -Extended Abstract
Abstract: In this paper we give a completeness theorem of an inductive inference rule inverse entailment proposed by Muggleton. Our main result is that a hypothesis clause H can be derived from an example E under a background theory B with inverse entailment iff H subsumes E relative to B in Plotkin's sense. The theory B can be any clausal theory, and the example E can be any clause which is neither a tautology nor implied by B. The derived hypothesis H is a clause which is not always definite. In order to prove the result we give declarative semantics for arbitrary consistent clausal theories, and show that SB-resolution, which was originally introduced by Plotkin, is complete procedural semantics. The completeness is shown as an extension of the completeness theorem of SLD-resolution. We also show that every hypothesis H derived with saturant generalization, proposed by Rouveirol, must subsume E w.r.t. B in Buntine's sense. Moreover we show that saturant generalization can be obtained from inverse entailment by giving some restriction to its usage. | [
1428,
2589
] | Train |
2,425 | 3 | Title: Structured Arc Reversal and Simulation of Dynamic Probabilistic Networks
Abstract: We present an algorithm for arc reversal in Bayesian networks with tree-structured conditional probability tables, and consider some of its advantages, especially for the simulation of dynamic probabilistic networks. In particular, the method allows one to produce CPTs for nodes involved in the reversal that exploit regularities in the conditional distributions. We argue that this approach alleviates some of the overhead associated with arc reversal, plays an important role in evidence integration and can be used to restrict sampling of variables in DPNs. We also provide an algorithm that detects the dynamic irrelevance of state variables in forward simulation. This algorithm exploits the structured CPTs in a reversed network to determine, in a time-independent fashion, the conditions under which a variable does or does not need to be sampled. | [
62,
423,
788,
2341,
2474
] | Test |
2,426 | 5 | Title: Inductive Constraint Logic
Abstract: A novel approach to learning first order logic formulae from positive and negative examples is presented. Whereas present inductive logic programming systems employ examples as true and false ground facts (or clauses), we view examples as interpretations which are true or false for the target theory. This viewpoint allows to reconcile the inductive logic programming paradigm with classical attribute value learning in the sense that the latter is a special case of the former. Because of this property, we are able to adapt AQ and CN2 type algorithms in order to enable learning of full first order formulae. However, whereas classical learning techniques have concentrated on concept representations in disjunctive normal form, we will use a clausal representation, which corresponds to a conjuctive normal form where each conjunct forms a constraint on positive examples. This representation duality reverses also the role of positive and negative examples, both in the heuristics and in the algorithm. The resulting theory is incorporated in a system named ICL (Inductive Constraint Logic). | [
344,
638,
1007,
1686,
1919,
2126,
2282,
2431,
2493
] | Train |
2,427 | 2 | Title: Solving the Multiple-Instance Problem with Axis-Parallel Rectangles
Abstract: The multiple instance problem arises in tasks where the training examples are ambiguous: a single example object may have many alternative feature vectors (instances) that describe it, and yet only one of those feature vectors may be responsible for the observed classification of the object. This paper describes and compares three kinds of algorithms that learn axis-parallel rectangles to solve the multiple-instance problem. Algorithms that ignore the multiple instance problem perform very poorly. An algorithm that directly confronts the multiple instance problem (by attempting to identify which feature vectors are responsible for the observed classifications) performs best, giving 89% correct predictions on a musk-odor prediction task. The paper also illustrates the use of artificial data to debug and compare these algorithms. | [
318,
507,
1888,
2391,
2394,
2548,
2591
] | Train |
2,428 | 3 | Title: Bumptrees for Efficient Function, Constraint, and Classification Learning
Abstract: A new class of data structures called bumptrees is described. These structures are useful for efficiently implementing a number of neural network related operations. An empirical comparison with radial basis functions is presented on a robot arm mapping learning task. Applications to density estimation, classification, and constraint representation and learning are also outlined. | [
44,
116,
225,
760,
1860,
2021,
2042
] | Train |
2,429 | 1 | Title: Automatic Definition of Modular Neural Networks
Abstract: A new class of data structures called bumptrees is described. These structures are useful for efficiently implementing a number of neural network related operations. An empirical comparison with radial basis functions is presented on a robot arm mapping learning task. Applications to density estimation, classification, and constraint representation and learning are also outlined. | [
1143,
2152,
2281,
2317,
2624,
2667
] | Validation |
2,430 | 4 | Title: Category: Control, Navigation and Planning Preference: Oral presentation Exploiting Model Uncertainty Estimates for Safe Dynamic
Abstract: Model learning combined with dynamic programming has been shown to be effective for learning control of continuous state dynamic systems. The simplest method assumes the learned model is correct and applies dynamic programming to it, but many approximators provide uncertainty estimates on the fit. How can they be exploited? This paper addresses the case where the system must be prevented from having catastrophic failures during learning. We propose a new algorithm adapted from the dual control literature and use Bayesian locally weighted regression models with stochastic dynamic programming. A common reinforcement learning assumption is that aggressive exploration should be encouraged. This paper addresses the converse case in which the system has to reign in exploration. The algorithm is illustrated on a 4 dimensional simulated control problem. | [
294,
682,
1860,
2647
] | Train |
2,431 | 5 | Title: Multi-class problems and discretization in ICL Extended abstract
Abstract: Handling multi-class problems and real numbers is important in practical applications of machine learning to KDD problems. While attribute-value learners address these problems as a rule, very few ILP systems do so. The few ILP systems that handle real numbers mostly do so by trying out all real values that are applicable, thus running into efficiency or overfitting problems. This paper discusses some recent extensions of ICL that address these problems. ICL, which stands for Inductive Constraint Logic, is an ILP system that learns first order logic formulae from positive and negative examples. The main charateristic of ICL is its view on examples. These are seen as interpretations which are true or false for the clausal target theory (in CNF). We first argue that ICL can be used for learning a theory in a disjunctive normal form (DNF). With this in mind, a possible solution for handling more than two classes is given (based on some ideas from CN2). Finally, we show how to tackle problems with continuous values by adapting discretization techniques from attribute value learners. | [
426,
1919,
2426,
2591
] | Test |
2,432 | 4 | Title: Learning the Peg-into-Hole Assembly Operation with a Connectionist Reinforcement Technique
Abstract: The paper presents a learning controller that is capable of increasing insertion speed during consecutive peg-into-hole operations, without increasing the contact force level. Our aim is to find a better relationship between measured forces and the controlled velocity, without using a complicated (human generated) model. We followed a connectionist approach. Two learning phases are distinguished. First the learning controller is trained (or initialised) in a supervised way by a suboptimal task frame controller. Then a reinforcement learning phase follows. The controller consists of two networks: (1) the policy network and (2) the exploration network. On-line robotic exploration plays a crucial role in obtaining a better policy. Optionally, this architecture can be extended with a third network: the reinforcement network. The learning controller is implemented on a CAD-based contact force simulator. In contrast with most other related work, the experiments are simulated in 3D with 6 degrees of freedom. Performance of a peg-into-hole task is measured in insertion time and average/maximum force level. The fact that a better performance can be obtained in this way, demonstrates the importance of model-free learning techniques for repetitive robotic assembly tasks. The paper presents the approach and simulation results. Keywords: robotic assembly, peg-into-hole, artificial neural networks, reinforcement learning. | [
1755
] | Test |
2,433 | 2 | Title: Robust Sound Localization: An Application of an Auditory Perception System for a Humanoid Robot
Abstract: The paper presents a learning controller that is capable of increasing insertion speed during consecutive peg-into-hole operations, without increasing the contact force level. Our aim is to find a better relationship between measured forces and the controlled velocity, without using a complicated (human generated) model. We followed a connectionist approach. Two learning phases are distinguished. First the learning controller is trained (or initialised) in a supervised way by a suboptimal task frame controller. Then a reinforcement learning phase follows. The controller consists of two networks: (1) the policy network and (2) the exploration network. On-line robotic exploration plays a crucial role in obtaining a better policy. Optionally, this architecture can be extended with a third network: the reinforcement network. The learning controller is implemented on a CAD-based contact force simulator. In contrast with most other related work, the experiments are simulated in 3D with 6 degrees of freedom. Performance of a peg-into-hole task is measured in insertion time and average/maximum force level. The fact that a better performance can be obtained in this way, demonstrates the importance of model-free learning techniques for repetitive robotic assembly tasks. The paper presents the approach and simulation results. Keywords: robotic assembly, peg-into-hole, artificial neural networks, reinforcement learning. | [
2437
] | Train |
2,434 | 3 | Title: Causal Inference from Indirect Experiments
Abstract: Indirect experiments are studies in which randomized control is replaced by randomized encouragement, that is, subjects are encouraged, rather than forced to receive treatment programs. The purpose of this paper is to bring to the attention of experimental researchers simple mathematical results that enable us to assess, from indirect experiments, the strength with which causal influences operate among variables of interest. The results reveal that despite the laxity of the encouraging instrument, indirect experimentation can yield significant and sometimes accurate information on the impact of a program on the population as a whole, as well as on the particular individuals who participated in the program. | [
105,
1326,
1747,
2069,
2160
] | Validation |
2,435 | 2 | Title: Identification in H 1 with Nonuniformly Spaced Frequency Response Measurements
Abstract: In this paper, the problem of "system identification in H 1 " is investigated in the case when the given frequency response data is not necessarily on a uniformly spaced grid of frequencies. A large class of robustly convergent identification algorithms are derived. A particular algorithm is further examined and explicit worst case error bounds (in the H 1 norm) are derived for both discrete-time and continuous-time systems. Examples are provided to illustrate the application of the algorithms. | [
2236,
2262
] | Test |
2,436 | 5 | Title: Space-Time Scheduling of Instruction-Level Parallelism on a Raw Machine
Abstract: Advances in VLSI technology will enable chips with over a billion transistors within the next decade. Unfortunately, the centralized-resource architectures of modern microprocessors are ill-suited to exploit such advances. Achieving a high level of parallelism at a reasonable clock speed requires distributing the processor resources a trend already visible in the dual-register-file architecture of the Alpha 21264. A Raw microprocessor takes an extreme position in this space by distributing all its resources such as instruction streams, register files, memory ports, and ALUs over a pipelined two-dimensional interconnect, and exposing them fully to the compiler. Compilation for instruction-level parallelism (ILP) on such distributed-resource machines requires both spatial instruction scheduling and traditional temporal instruction scheduling. This paper describes the techniques used by the Raw compiler to handle these issues. Preliminary results from a SUIF-based compiler for sequential programs written in C and Fortran indicate that the Raw approach to exploiting ILP can achieve speedups scalable with the number of processors for applications with such parallelism. The Raw architecture attempts to provide performance that is at least comparable to that provided by scaling an existing architecture, but that can achieve orders of magnitude improvement in performance for applications with a large amount of parallelism. This paper offers some positive results in this direction. | [
2649
] | Train |
2,437 | 4 | Title: Embodiment and Manipulation Learning Process for a Humanoid Hand
Abstract: Advances in VLSI technology will enable chips with over a billion transistors within the next decade. Unfortunately, the centralized-resource architectures of modern microprocessors are ill-suited to exploit such advances. Achieving a high level of parallelism at a reasonable clock speed requires distributing the processor resources a trend already visible in the dual-register-file architecture of the Alpha 21264. A Raw microprocessor takes an extreme position in this space by distributing all its resources such as instruction streams, register files, memory ports, and ALUs over a pipelined two-dimensional interconnect, and exposing them fully to the compiler. Compilation for instruction-level parallelism (ILP) on such distributed-resource machines requires both spatial instruction scheduling and traditional temporal instruction scheduling. This paper describes the techniques used by the Raw compiler to handle these issues. Preliminary results from a SUIF-based compiler for sequential programs written in C and Fortran indicate that the Raw approach to exploiting ILP can achieve speedups scalable with the number of processors for applications with such parallelism. The Raw architecture attempts to provide performance that is at least comparable to that provided by scaling an existing architecture, but that can achieve orders of magnitude improvement in performance for applications with a large amount of parallelism. This paper offers some positive results in this direction. | [
427,
745,
2433
] | Train |
2,438 | 2 | Title: Integrating Initialization Bias and Search Bias in Neural Network Learning
Abstract: The use of previously learned knowledge during learning has been shown to reduce the number of examples required for good generalization, and to increase robustness to noise in the examples. In reviewing various means of using learned knowledge from a domain to guide further learning in the same domain, two underlying classes are discerned. Methods which use previous knowledge to initialize a learner (as an initialization bias), and those that use previous knowledge to constrain a learner (as a search bias). We show such methods in fact exploit the same domain knowledge differently, and can complement each other. This is shown by presenting a combined approach which both initializes and constrains a learner. This combined approach is seen to outperform the individual methods under the conditions that accurate previously learned domain knowledge is available, and that there are irrelevant features in the domain representation. | [
92,
2091
] | Train |
2,439 | 2 | Title: Analog Neural Nets with Gaussian or other Common Noise Distributions cannot Recognize Arbitrary Regular Languages
Abstract: We consider recurrent analog neural nets where the output of each gate is subject to Gaussian noise, or any other common noise distribution that is nonzero on a large set. We show that many regular languages cannot be recognized by networks of this type, and we give a precise characterization of those languages which can be recognized. This result implies severe constraints on possibilities for constructing recurrent analog neural nets that are robust against realistic types of analog noise. On the other hand we present a method for constructing feedforward analog neural nets that are robust with regard to analog noise of this type. | [
407,
1875
] | Test |
2,440 | 2 | Title: Modifying Network Architectures for Certainty-Factor Rule-Base Revision
Abstract: This paper describes Rapture | a system for revising probabilistic rule bases that converts symbolic rules into a connectionist network, which is then trained via connectionist techniques. It uses a modified version of backpropagation to refine the certainty factors of the rule base, and uses ID3's information-gain heuristic (Quinlan, 1986) to add new rules. Work is currently under way for finding improved techniques for modifying network architectures that include adding hidden units using the UPSTART algorithm (Frean, 1990). A case is made via comparison with fully connected connectionist techniques for keeping the rule base as close to the original as possible, adding new input units only as needed. | [
2543
] | Validation |
2,441 | 5 | Title: Distance Induction in First Order Logic used for classification via a k-nearest-neighbor process. Experiments on
Abstract: This paper tackles the supervised induction of a distance from examples described as Horn clauses or constrained clauses. In opposition to syntax-driven approaches, this approach is discrimination-driven: it proceeds by defining a small set of complex discriminant hypotheses. These hypotheses serve as new concepts, used to redescribe the initial examples. Further, this redescription can be embedded into the space of natural integers, and a distance between examples thus naturally follows. | [
66,
344,
2585
] | Train |
2,442 | 4 | Title: Using Temporal-Difference Reinforcement Learning to Improve Decision-Theoretic Utilities for Diagnosis
Abstract: Probability theory represents and manipulates uncertainties, but cannot tell us how to behave. For that we need utility theory which assigns values to the usefulness of different states, and decision theory which concerns optimal rational decisions. There are many methods for probability modeling, but few for learning utility and decision models. We use reinforcement learning to find the optimal sequence of questions in a diagnosis situation while maintaining a high accuracy. Automated diagnosis on a heart-disease domain is used to demonstrate that temporal-difference learning can improve diagnosis. On the Cleveland heart-disease database our results are better than those reported from all previous methods. | [
71,
523,
565,
929,
2118
] | Train |
2,443 | 3 | Title: Issues in the Integration of Data Mining and Data Visualization Visualizing the Simple Bayesian Classifier
Abstract: The simple Bayesian classifier (SBC), sometimes called Naive-Bayes, is built based on a conditional independence model of each attribute given the class. The model was previously shown to be surprisingly robust to obvious violations of this independence assumption, yielding accurate classification models even when there are clear conditional dependencies. The SBC can serve as an excellent tool for initial exploratory data analysis when coupled with a visualizer that makes its structure comprehensible. We describe such a visual representation of the SBC model that has been successfully implemented. We describe the requirements we had for such a visualization and the design decisions we made to satisfy them. | [
1339,
2338,
2343
] | Train |
2,444 | 4 | Title: Symbiotic Evolution of Neural Networks in Sequential Decision Tasks
Abstract: The simple Bayesian classifier (SBC), sometimes called Naive-Bayes, is built based on a conditional independence model of each attribute given the class. The model was previously shown to be surprisingly robust to obvious violations of this independence assumption, yielding accurate classification models even when there are clear conditional dependencies. The SBC can serve as an excellent tool for initial exploratory data analysis when coupled with a visualizer that makes its structure comprehensible. We describe such a visual representation of the SBC model that has been successfully implemented. We describe the requirements we had for such a visualization and the design decisions we made to satisfy them. | [
500,
2257
] | Train |
2,445 | 2 | Title: Simulation of Reduced Precision Arithmetic for Digital Neural Networks Using the RAP Machine
Abstract: This paper describes some of our recent work in the development of computer architectures for efficient execution of artificial neural network algorithms. Our earlier system, the Ring Array Processor (RAP), was a multiprocessor based on commercial DSPs with a low-latency ring interconnection scheme. We have used the RAP to simulate variable precision arithmetic and guide us in the design of higher performance neurocomputers based on custom VLSI. The RAP system played a critical role in this study, enabling us to experiment with much larger networks than would otherwise be possible. Our study shows that back-propagation training algorithms only require moderate precision. Specifically, 16b weight values and 8b output values are sufficient to achieve training and classification results comparable to 32b floating point. Although these results were gathered for frame classification in continuous speech, we expect that they will extend to many other connectionist calculations. We have used these results as part of the design of a programmable single chip microprocessor, SPERT. The reduced precision arithmetic permits the use of multiple units per processor. Also, reduced precision operands make more efficient use of valuable processor-memory bandwidth. For our moderate-precision fixed-point arithmetic applications, SPERT represents more than an order of magnitude reduction in cost over systems based on DSP chips. | [
2268,
2275
] | Validation |
2,446 | 1 | Title: Simulation of Reduced Precision Arithmetic for Digital Neural Networks Using the RAP Machine
Abstract: 1] R.K. Belew, J. McInerney, and N. Schraudolph, Evolving networks: using the genetic algorithm with connectionist learning, in Artificial Life II, SFI Studies in the Science of Complexity, C.G. Langton, C. Taylor, J.D. Farmer, S. Rasmussen Eds., vol. 10, Addison-Wesley, 1991. [2] M. McInerney, and A.P. Dhawan, Use of genetic algorithms with back propagation in training of feed-forward neural networks, in IEEE International Conference on Neural Networks, vol. 1, pp. 203-208, 1993. [3] F.Z. Brill, D.E. Brown, and W.N. Martin, Fast genetic selection of features for neural network classifiers, IEEE Transactions on Neural Networks, vol. 3, no. 2, pp. 324-328, 1992. [4] F. Dellaert, and J. Vandewalle, Automatic design of cellular neural networks by means of genetic algorithms: finding a feature detector, in The Third IEEE International Workshop on Cellular Neural Networks and Their Applications, IEEE, New Jersey, pp. 189-194, 1994. [5] D.E. Moriarty, and R. Miikkulainen, Efficient reinforcement learning through symbiotic evolution, Machine Learning, vol. 22, pp. 11-33, 1996. [6] L. Davis, Handbook of Genetic Algorithms, Van Nostrand Reinhold, New York, 1991. [7] D. Whitely, The GENITOR algorithm and selective pressure, in Proceedings of the Third Interanational Conference on Genetic Algorithms, J.D. Schaffer Ed., Morgan Kauffman, San Mateo, CA, 1989, pp. 116-121. [8] van Camp, D., T. Plate and G.E. Hinton (1992). The Xerion Neural Network Simulator and Documentation. Department of Computer Science, University of Toronto, Toronto. | [
129,
247,
2451
] | Test |
2,447 | 0 | Title: New Roles for Machine Learning in Design for Design of Educational Computing New roles for
Abstract: Research on machine learning in design has concentrated on the use and development of techniques that can solve simple well-defined problems. Invariably, this effort, while important at the early stages of the development of the field, cannot scale up to address real design problems since all existing techniques are based on simplifying assumptions that do not hold for real design. In particular they do not address the dependence on context and multiple, often conflicting, interests that are constitutive of design. This paper analyzes the present situation and criticizes a number of prevailing views. Subsequently, the paper offers an alternative approach whose goal is to advance the use of machine learning in design practice. The approach is partially integrated into a modeling system called n-dim. The use of machine learning in n-dim is presented and open research issues are outlined. | [
378,
2010
] | Train |
2,448 | 2 | Title: Automatic Smoothing Spline Projection Pursuit Automatic Smoothing Spline Projection Pursuit.
Abstract: kj = 1. The standard PPR algorithm of Friedman and Stuet-zle (1981) estimates the smooth functions f j using the supersmoother nonparametric scatterplot smoother. Friedman's algorithm constructs a model with M max linear combinations, then prunes back to a simpler model of size M M max , where M and M max are specified by the user. This paper discusses an alternative algorithm in which the smooth functions are estimated using smoothing splines. The direction coefficients ff j , the amount of smoothing in each direction, and the number of terms M and M max are determined to optimize a single generalized cross-validation measure. | [
427,
519,
2311,
2526
] | Train |
2,449 | 5 | Title: Learning by Refining Algorithm Sketches
Abstract: In this paper we suggest a mechanism that improves significantly the performance of a top-down inductive logic programming (ILP) learning system. This improvement is achieved at the cost of giving to the system extra information that is not difficult to formulate. This information appears in the form of an algorithm sketch: an incomplete and somewhat vague representation of the computation related to a particular example. We describe which sketches are admissible, give details of the learning algorithm that exploits the information contained in the sketch. The experiments carried out with the implemented system (SKIL) have demonstrated the usefulness of the method and its potential in future applications. | [
1881,
2158,
2450
] | Train |
2,450 | 5 | Title: Architecture for Iterative Learning of Recursive Definitions
Abstract: In this paper we are concerned with the problem of inducing recursive Horn clauses from small sets of training examples. The method of iterative bootstrap induction is presented. In the first step, the system generates simple clauses, which can be regarded as properties of the required definition. Properties represent generalizations of the positive examples, simulating the effect of having larger number of examples. Properties are used subsequently to induce the required recursive definitions. This paper describes the method together with a series of experiments. The results support the thesis that iterative bootstrap induction is indeed an effective technique that could be of general use in ILP. | [
1498,
1881,
2449
] | Train |
2,451 | 1 | Title: Automatic Design of Cellular Neural Networks by means of Genetic Algorithms: Finding a Feature Detector
Abstract: This paper aims to examine the use of genetic algorithms to optimize subsystems of cellular neural network architectures. The application at hand is character recognition: the aim is to evolve an optimal feature detector in order to aid a conventional classifier network to generalize across different fonts. To this end, a performance function and a genetic encoding for a feature detector are presented. An experiment is described where an optimal feature detector is indeed found by the genetic algorithm. We are interested in the application of cellular neural networks in computer vision. Genetic algorithms (GA's) [1-3] can serve to optimize the design of cellular neural networks. Although the design of the global architecture of the system could still be done by human insight, we propose that specific sub-modules of the system are best optimized using one or other optimization method. GAs are a good candidate to fulfill this optimization role, as they are well suited to problems where the objective function is a complex function of many parameters. The specific problem we want to investigate is one of character recognition. More specifically, we would like to use the GA to find optimal feature detectors to be used in the recognition of digits . | [
129,
163,
1973,
2446
] | Train |
2,452 | 2 | Title: A Bootstrap Evaluation of the Effect of Data Splitting on Financial Time Series
Abstract: This article exposes problems of the commonly used technique of splitting the available data into training, validation, and test sets that are held fixed, warns about drawing too strong conclusions from such static splits, and shows potential pitfalls of ignoring variability across splits. Using a bootstrap or resampling method, we compare the uncertainty in the solution stemming from the data splitting with neural network specific uncertainties (parameter initialization, choice of number of hidden units, etc.). We present two results on data from the New York Stock Exchange. First, the variation due to different resamplings is significantly larger than the variation due to different network conditions. This result implies that it is important to not over-interpret a model (or an ensemble of models) estimated on one specific split of the data. Second, on each split, the neural network solution with early stopping is very close to a linear model; no significant nonlinearities are extracted. | [
1315,
2595
] | Train |
2,453 | 4 | Title: Packet Routing and Reinforcement Learning: Estimating Shortest Paths in Dynamic Graphs
Abstract: This article exposes problems of the commonly used technique of splitting the available data into training, validation, and test sets that are held fixed, warns about drawing too strong conclusions from such static splits, and shows potential pitfalls of ignoring variability across splits. Using a bootstrap or resampling method, we compare the uncertainty in the solution stemming from the data splitting with neural network specific uncertainties (parameter initialization, choice of number of hidden units, etc.). We present two results on data from the New York Stock Exchange. First, the variation due to different resamplings is significantly larger than the variation due to different network conditions. This result implies that it is important to not over-interpret a model (or an ensemble of models) estimated on one specific split of the data. Second, on each split, the neural network solution with early stopping is very close to a linear model; no significant nonlinearities are extracted. | [
427,
2666
] | Validation |
2,454 | 2 | Title: Early Stopping but when?
Abstract: Validation can be used to detect when overfitting starts during supervised training of a neural network; training is then stopped before convergence to avoid the overfitting ("early stopping"). The exact criterion used for validation-based early stopping, however, is usually chosen in an ad-hoc fashion or training is stopped interactively. This trick describes how to select a stopping criterion in a systematic fashion; it is a trick for either speeding learning procedures or improving generalization, whichever is more important in the particular situation. An empirical investigation on multi-layer perceptrons shows that there exists a tradeoff between training time and generalization: From the given mix of 1296 training runs using different 12 problems and 24 different network architectures I conclude slower stopping criteria allow for small improvements in generalization (here: about 4% on average), but cost much more training time (here: about factor 4 longer on average). | [
881,
1058,
1342,
2129
] | Train |
2,455 | 6 | Title: Learning From a Population of Hypotheses
Abstract: We introduce a new formal model in which a learning algorithm must combine a collection of potentially poor but statistically independent hypothesis functions in order to approximate an unknown target function arbitrarily well. Our motivation includes the question of how to make optimal use of multiple independent runs of a mediocre learning algorithm, as well as settings in which the many hypotheses are obtained by a distributed population of identical learning agents. | [
453,
456,
2354
] | Train |
2,456 | 3 | Title: Markov Chain Monte Carlo in Practice: A Roundtable Discussion
Abstract: Markov chain Monte Carlo (MCMC) methods make possible the use of flexible Bayesian models that would otherwise be computationally infeasible. In recent years, a great variety of such applications have been described in the literature. Applied statisticians who are new to these methods may have several questions and concerns, however: How much effort and expertise are needed to design and use a Markov chain sampler? How much confidence can one have in the answers that MCMC produces? How does the use of MCMC affect the rest of the model-building process? At the Joint Statistical Meetings in August, 1996, a panel of experienced MCMC users discussed these and other issues, as well as various "tricks of the trade". This paper is an edited recreation of that discussion. Its purpose is to offer advice and guidance to novice users of MCMC and to not-so-novice users as well. Topics include building confidence in simulation results, methods for speeding convergence, assessing standard errors, identification of models for which good MCMC algorithms exist, and the current state of software development. | [
41,
48,
1029,
1742
] | Train |
2,457 | 2 | Title: In Proceedings of the 1997 Sian Kaan International Workshop on Neural Networks and Neurocontrol. Real-Valued
Abstract: 2 Neural Network & Machine Learning Laboratory Computer Science Department Brigham Young University Provo, UT 84602, USA Email: martinez@cs.byu.edu WWW: http://axon.cs.byu.edu Abstract. Many neural network models must be trained by finding a set of real-valued weights that yield high accuracy on a training set. Other learning models require weights on input attributes that yield high leave-one-out classification accuracy in order to avoid problems associated with irrelevant attributes and high dimensionality. In addition, there are a variety of general problems for which a set of real values must be found which maximize some evaluation function. This paper presents an algorithm for doing a schemata search over a real-valued weight space to find a set of weights (or other real values) that yield high values for a given evaluation function. The algorithm, called the Real-Valued Schemata Search (RVSS), uses the BRACE statistical technique [Moore & Lee, 1993] to determine when to narrow the search space. This paper details the RVSS approach and gives initial empirical results. | [
690,
1980
] | Train |
2,458 | 3 | Title: ESTIMATING THE SQUARE ROOT OF A DENSITY VIA COMPACTLY SUPPORTED WAVELETS
Abstract: A large body of nonparametric statistical literature is devoted to density estimation. Overviews are given in Silverman (1986) and Izenman (1991). This paper addresses the problem of univariate density estimation in a novel way. Our approach falls in the class of so called projection estimators, introduced by Cencov (1962). The orthonor-mal basis used is a basis of compactly supported wavelets from Daubechies' family. Kerkyacharian and Picard (1992, 1993), Donoho et al. (1996), and Delyon and Judit-sky (1993), among others, applied wavelets in density estimation. The local nature of wavelet functions makes the wavelet estimator superior to projection estimators that use classical orthonormal bases (Fourier, Hermite, etc.) Instead of estimating the unknown density directly, we estimate the square root of the density, which enables us to control the positiveness and the L 1 norm of the density estimate. However, in that approach one needs a pre-estimator of the density to calculate sample wavelet coefficients. We describe VISUSTOP, a data-driven procedure for determining the maximum number of levels in the wavelet density estimator. Coefficients in the selected levels are thresholded to make the estimator parsimonious. | [
2242,
2366,
2506
] | Validation |
2,459 | 2 | Title: Control of Selective Visual Attention: Modeling the "Where" Pathway
Abstract: Intermediate and higher vision processes require selection of a subset of the available sensory information before further processing. Usually, this selection is implemented in the form of a spatially circumscribed region of the visual field, the so-called "focus of attention" which scans the visual scene dependent on the input and on the attentional state of the subject. We here present a model for the control of the focus of attention in primates, based on a saliency map. This mechanism is not only expected to model the functionality of biological vision but also to be essential for the understanding of complex scenes in machine vision. | [
553,
2606
] | Train |
2,460 | 3 | Title: Mutual Information as a Bayesian Measure of Independence
Abstract: 0.0 Abstract. The problem of hypothesis testing is examined from both the historical and the Bayesian points of view in the case that sampling is from an underlying joint probability distribution and the hypotheses tested for are those of independence and dependence of the underlying distribution. Exact results for the Bayesian method are provided. Asymptotic Bayesian results and historical method quantities are compared, and historical method quantities are interpreted in terms of clearly defined Bayesian quantities. The asymptotic Bayesian test relies upon a statistic that is predominantly mutual information. Problems of hypothesis testing arise ubiquitously in situations where observed data is produced by an unknown process and the question is asked From what process did this observed data arise? Historically, the hypothesis testing problem is approached from the point of view of sampling, whereby several fixed hypotheses to be tested for are given, and all measures of the test and its quality are found directly from the likelihood, i.e. by what amounts to sampling the likelihood [2] [3]. (To be specific, a hypothesis is a set of possible parameter vectors, each parameter vector completely specifying a sampling distribution. A simple hypothesis is a hypothesis set that contains one parameter vector. A composite hypothesis occurs when the (nonempty) hypothesis set is not a single parameter vector.) Generally, the test procedure chooses as true the hypothesis that gives the largest test value, although the notion of procedure is not specific and may refer to any method for choosing the hypothesis given the test values. Since it is of interest to quantify the quality of the test, a level of significance is generated, this level being the probability that, under the chosen hypothesis and test procedure, an incorrect hypothesis choice is made. The significance is generated using the sampling distribution, or likelihood. For simple hypotheses the level of significance is found using the single parameter value of the hypothesis. When a test is applied in the case of a composite hypothesis, a size for the test is found that is given by the supremum probability (ranging over the parameter vectors in the hypothesis set) that under the chosen | [
2384
] | Train |
2,461 | 3 | Title: A guide to the literature on learning probabilistic networks from data
Abstract: This literature review discusses different methods under the general rubric of learning Bayesian networks from data, and includes some overlapping work on more general probabilistic networks. Connections are drawn between the statistical, neural network, and uncertainty communities, and between the different methodological communities, such as Bayesian, description length, and classical statistics. Basic concepts for learning and Bayesian networks are introduced and methods are then reviewed. Methods are discussed for learning parameters of a probabilistic network, for learning the structure, and for learning hidden variables. The presentation avoids formal definitions and theorems, as these are plentiful in the literature, and instead illustrates key concepts with simplified examples. | [
1076,
1078,
2492
] | Validation |
2,462 | 3 | Title: Building Classifiers using Bayesian Networks
Abstract: Recent work in supervised learning has shown that a surprisingly simple Bayesian classifier with strong assumptions of independence among features, called naive Bayes, is competitive with state of the art classifiers such as C4.5. This fact raises the question of whether a classifier with less restrictive assumptions can perform even better. In this paper we examine and evaluate approaches for inducing classifiers from data, based on recent results in the theory of learning Bayesian networks. Bayesian networks are factored representations of probability distributions that generalize the naive Bayes classifier and explicitly represent statements about independence. Among these approaches we single out a method we call Tree Augmented Naive Bayes (TAN), which outperforms naive Bayes, yet at the same time maintains the computational simplicity (no search involved) and robustness which are characteristic of naive Bayes. We experimentally tested these approaches using benchmark problems from the U. C. Irvine repository, and compared them against C4.5, naive Bayes, and wrapper-based feature selection methods. | [
401,
1986
] | Validation |
2,463 | 3 | Title: Learning Belief Networks in the Presence of Missing Values and Hidden Variables
Abstract: In recent years there has been a flurry of works on learning probabilistic belief networks. Current state of the art methods have been shown to be successful for two learning scenarios: learning both network structure and parameters from complete data, and learning parameters for a fixed network from incomplete datathat is, in the presence of missing values or hidden variables. However, no method has yet been demonstrated to effectively learn network structure from incomplete data. In this paper, we propose a new method for learning network structure from incomplete data. This method is based on an extension of the Expectation-Maximization (EM) algorithm for model selection problems that performs search for the best structure inside the EM procedure. We prove the convergence of this algorithm, and adapt it for learning belief networks. We then describe how to learn networks in two scenarios: when the data contains missing values, and in the presence of hidden variables. We provide experimental results that show the effectiveness of our procedure in both scenarios. | [
558,
1934
] | Train |
2,464 | 3 | Title: Static Data Association with a Terrain-Based Prior Density
Abstract: In recent years there has been a flurry of works on learning probabilistic belief networks. Current state of the art methods have been shown to be successful for two learning scenarios: learning both network structure and parameters from complete data, and learning parameters for a fixed network from incomplete datathat is, in the presence of missing values or hidden variables. However, no method has yet been demonstrated to effectively learn network structure from incomplete data. In this paper, we propose a new method for learning network structure from incomplete data. This method is based on an extension of the Expectation-Maximization (EM) algorithm for model selection problems that performs search for the best structure inside the EM procedure. We prove the convergence of this algorithm, and adapt it for learning belief networks. We then describe how to learn networks in two scenarios: when the data contains missing values, and in the presence of hidden variables. We provide experimental results that show the effectiveness of our procedure in both scenarios. | [
1817
] | Test |
2,465 | 0 | Title: A systematic description of greedy optimisation algorithms for cost sensitive generalisation
Abstract: This paper defines a class of problems involving combinations of induction and (cost) optimisation. A framework is presented that systematically describes problems that involve construction of decision trees or rules, optimising accuracy as well as measurement- and misclassification costs. It does not present any new algorithms but shows how this framework can be used to configure greedy algorithms for constructing such trees or rules. The framework covers a number of existing algorithms. Moreover, the framework can also be used to define algorithm configurations with new functionalities, as expressed in their evaluation functions. | [
228,
638,
2057
] | Train |
2,466 | 0 | Title: FLARE: Induction with Prior Knowledge
Abstract: This paper defines a class of problems involving combinations of induction and (cost) optimisation. A framework is presented that systematically describes problems that involve construction of decision trees or rules, optimising accuracy as well as measurement- and misclassification costs. It does not present any new algorithms but shows how this framework can be used to configure greedy algorithms for constructing such trees or rules. The framework covers a number of existing algorithms. Moreover, the framework can also be used to define algorithm configurations with new functionalities, as expressed in their evaluation functions. | [
831,
1830,
2240
] | Validation |
2,467 | 6 | Title: Learning to Reason with a Restricted View
Abstract: The Learning to Reason framework combines the study of Learning and Reasoning into a single task. Within it, learning is done specifically for the purpose of reasoning with the learned knowledge. Computational considerations show that this is a useful paradigm; in some cases learning and reasoning problems that are intractable when studied separately become tractable when performed as a task of Learning to Reason. In this paper we study Learning to Reason problems where the interaction with the world supplies the learner only partial information in the form of partial assignments. Several natural interpretations of partial assignments are considered and learning and reasoning algorithms using these are developed. The results presented exhibit a tradeoff between learnability, the strength of the oracles used in the interface, and the range of reasoning queries the learner is guaranteed to answer correctly. | [
323,
2155,
2468
] | Train |
2,468 | 3 | Title: On the Hardness of Approximate Reasoning
Abstract: Many AI problems, when formalized, reduce to evaluating the probability that a propositional expression is true. In this paper we show that this problem is computationally intractable even in surprisingly restricted cases and even if we settle for an approximation to this probability. We consider various methods used in approximate reasoning such as computing degree of belief and Bayesian belief networks, as well as reasoning techniques such as constraint satisfaction and knowledge compilation, that use approximation to avoid computational difficulties, and reduce them to model-counting problems over a propositional domain. We prove that counting satisfying assignments of propositional languages is intractable even for Horn and monotone formulae, and even when the size of clauses and number of occurrences of the variables are extremely limited. This should be contrasted with the case of deductive reasoning, where Horn theories and theories with binary clauses are distinguished by the existence of linear time satisfiability algorithms. What is even more surprising is that, as we show, even approximating the number of satisfying assignments (i.e., "approximating" approximate reasoning), is intractable for most of these restricted theories. We also identify some restricted classes of propositional formulae for which efficient algorithms for counting satisfying assignments can be given. fl Preliminary version of this paper appeared in the Proceedings of the 13th International Joint Conference on Artificial Intelligence, IJCAI93. y Supported by NSF grants CCR-89-02500 and CCR-92-00884 and by DARPA AFOSR-F4962-92-J-0466. | [
2467
] | Validation |
2,469 | 2 | Title: Extended Kalman filter in recurrent neural network training and pruning
Abstract: Recently, extended Kalman filter (EKF) based training has been demonstrated to be effective in neural network training. However, its conjunction with pruning methods such as weight decay and optimal brain damage (OBD) has not yet been studied. In this paper, we will elucidate the method of EKF training and propose a pruning method which is based on the results obtained by EKF training. These combined training pruning method is applied to a time series prediction problem. | [
1789
] | Train |
2,470 | 1 | Title: Induction and Recapitulation of Deep Musical Structure
Abstract: We describe recent extensions to our framework for the automatic generation of music-making programs. We have previously used genetic programming techniques to produce music-making programs that satisfy user-provided critical criteria. In this paper we describe new work on the use of connectionist techniques to automatically induce musical structure from a corpus. We show how the resulting neural networks can be used as critics that drive our genetic programming system. We argue that this framework can potentially support the induction and recapitulation of deep structural features of music. We present some initial results produced using neural and hybrid symbolic/neural critics, and we discuss directions for future work. | [
1230,
1277,
2101,
2643,
2646
] | Test |
2,471 | 0 | Title: ILA: Combining Inductive Learning with Prior Knowledge and Reasoning
Abstract: We describe recent extensions to our framework for the automatic generation of music-making programs. We have previously used genetic programming techniques to produce music-making programs that satisfy user-provided critical criteria. In this paper we describe new work on the use of connectionist techniques to automatically induce musical structure from a corpus. We show how the resulting neural networks can be used as critics that drive our genetic programming system. We argue that this framework can potentially support the induction and recapitulation of deep structural features of music. We present some initial results produced using neural and hybrid symbolic/neural critics, and we discuss directions for future work. | [
2245
] | Train |
2,472 | 4 | Title: Toward an Ideal Trainer*
Abstract: This paper appeared in 1994 in Machine Learning, 15 (3): 251-277. Abstract This paper demonstrates how the nature of the opposition during training affects learning to play two-person, perfect information board games. It considers different kinds of competitive training, the impact of trainer error, appropriate metrics for post-training performance measurement, and the ways those metrics can be applied. The results suggest that teaching a program by leading it repeatedly through the same restricted paths, albeit high quality ones, is overly narrow preparation for the variations that appear in real-world experience. The results also demonstrate that variety introduced into training by random choice is unreliable preparation, and that a program that directs its own training may overlook important situations. The results argue for a broad variety of training experience with play at many levels. This variety may either be inherent in the game or introduced deliberately into the training. Lesson and practice training, a blend of expert guidance and knowledge-based, self-directed elaboration, is shown to be particularly effective for learning during competition. | [
565,
2476
] | Test |
2,473 | 0 | Title: A Heuristic Approach to the Discovery of Macro-operators. Machine Learning, 3, 285-317. L e a
Abstract: The negative effect is naturally more significant in the more complex domain. The graph for the simple domain crosses the 0 line earlier than the complex domain. That means that learning starts to be useful with weight greater than 0.6 for the simple domain and 0.7 for the complex domain. As we relax the optimality requirement more s i g n i f i c a n t l y ( w i t h a W = 0.8), macro usage in the more complex domain becomes more advantageous. The purpose of the research described in this paper is to identify the parameters that effects deductive learning and to perform experiments systematically in order to understand the nature of those effects. The goal of this paper is to demonstrate the methodology of performing parametric experimental study of deductive learning. The example here include the study of two parameters: the point on the satisficing-optimizing scale that is used during the search carried out during problem solving time and during learning time. We showed that A*, which looks for optimal solutions, cannot benefit from macro learning but as the strategy comes closer to best-first (satisficing search), the utility of macros increases. We also demonstrated that deductive learners that learn offline by solving training problems are sensitive to the type of search used during the learning. We showed that in general optimizing search is best for learning. It generates macros that increase the quality solutions regardless of the search method used during problem solving. It also improves the efficiency for problem solvers that require a high level of optimality. The only drawback in using optimizing search is the increase in learning resources spent. We are aware of the fact that the results described here are not very surprising. The goal of the parametric study is not necessarily to find exciting results, but to obtain results, sometimes even previously known, in a controlled experimental environment. The work described here is only part of our research plan. We are currently in the process of extensive experimentation with all the parameters described here and also with others. We also intend to test the validity of the conclusions reached during the study by repeating some of the tests in several of the commonly known search problems. We hope that such systematic experimentation will help the research community to better understand the process of deductive learning and will serve as a demonstration of the experimental methodology that should be used in machine learning research. | [
434,
551,
1192,
2551
] | Train |
2,474 | 3 | Title: The Frame Problem and Bayesian Network Action Representations
Abstract: We examine a number of techniques for representing actions with stochastic effects using Bayesian networks and influence diagrams. We compare these techniques according to ease of specification and size of the representation required for the complete specification of the dynamics of a particular system, paying particular attention the role of persistence relationships. We precisely characterize two components of the frame problem for Bayes nets and stochastic actions, propose several ways to deal with these problems, and compare our solutions with Re-iter's solution to the frame problem for the situation calculus. The result is a set of techniques that permit both ease of specification and compact representation of probabilistic system dynamics that is of comparable size (and timbre) to Reiter's representation (i.e., with no explicit frame axioms). | [
62,
2078,
2425
] | Train |
2,475 | 6 | Title: Learning polynomials with queries: The highly noisy case task for the case when F
Abstract: Given a function f mapping n-variate inputs from a finite field F into F , we consider the task of reconstructing a list of all n-variate degree d polynomials which agree with f on a tiny but non-negligible fraction, ffi, of the input space. We give a randomized algorithm for solving this task which accesses f as a black box and runs in time polynomial in 1 d=jF j). For the special case when d = 1, we solve this problem for all * def jF j > 0. In this case the running time of our algorithm is bounded by a polynomial in 1 * ; n and exponential in d. Our algorithm generalizes a previously known algorithm, due to Goldreich and Levin, that solves this | [
574,
591,
640,
1363,
2246
] | Validation |
2,476 | 6 | Title: Why Experimentation can be better than "Perfect Guidance"
Abstract: Many problems correspond to the classical control task of determining the appropriate control action to take, given some (sequence of) observations. One standard approach to learning these control rules, called behavior cloning, involves watching a perfect operator operate a plant, and then trying to emulate its behavior. In the experimental learning approach, by contrast, the learner first guesses an initial operation-to-action policy and tries it out. If this policy performs sub-optimally, the learner can modify it to produce a new policy, and recur. This paper discusses the relative effectiveness of these two approaches, especially in the presence of perceptual aliasing, showing in particular that the experimental learner can often learn more effectively than the cloning one. | [
294,
2472
] | Validation |
2,477 | 2 | Title: Neural Models for Part-Whole Hierarchies
Abstract: We present a connectionist method for representing images that explicitly addresses their hierarchical nature. It blends data from neu-roscience about whole-object viewpoint sensitive cells in inferotem-poral cortex 8 and attentional basis-field modulation in V4 3 with ideas about hierarchical descriptions based on microfeatures. 5, 11 The resulting model makes critical use of bottom-up and top-down pathways for analysis and synthesis. 6 We illustrate the model with a simple example of representing information about faces. | [
2678
] | Train |
2,478 | 1 | Title: Culture Enhances the Evolvability of Cognition
Abstract: This paper discusses the role of culture in the evolution of cognitive systems. We define culture as any information transmitted between individuals and between generations by non-genetic means. Experiments are presented that use genetic programming systems that include special mechanisms for cultural transmission of information. These systems evolve computer programs that perform cognitive tasks including mathematical function mapping and action selection in a virtual world. The data show that the presence of culture-supporting mechanisms can have a clear beneficial impact on the evolvability of correct programs. The implications that these results may have for cognitive science are briefly discussed. | [
2220,
2226
] | Test |
2,479 | 1 | Title: A Transformation System for Interactive Reformulation of Design Optimization Strategies
Abstract: Numerical design optimization algorithms are highly sensitive to the particular formulation of the optimization problems they are given. The formulation of the search space, the objective function and the constraints will generally have a large impact on the duration of the optimization process as well as the quality of the resulting design. Furthermore, the best formulation will vary from one application domain to another, and from one problem to another within a given application domain. Unfortunately, a design engineer may not know the best formulation in advance of attempting to set up and run a design optimization process. In order to attack this problem, we have developed a software environment that supports interactive formulation, testing and reformulation of design optimization strategies. Our system represents optimization strategies in terms of second-order dataflow graphs. Reformulations of strategies are implemented as transformations between dataflow graphs. The system permits the user to interactively generate and search a space of design optimization strategies, and experimentally evaluate their performance on test problems, in order to find a strategy that is suitable for his application domain. The system has been implemented in a domain independent fashion, and is being tested in the domain of racing yacht design. | [
2128,
2319
] | Train |
2,480 | 4 | Title: Planning by Incremental Dynamic Programming
Abstract: This paper presents the basic results and ideas of dynamic programming as they relate most directly to the concerns of planning in AI. These form the theoretical basis for the incremental planning methods used in the integrated architecture Dyna. These incremental planning methods are based on continually updating an evaluation function and the situation-action mapping of a reactive system. Actions are generated by the reactive system and thus involve minimal delay, while the incremental planning process guarantees that the actions and evaluation function will eventually be optimal|no matter how extensive a search is required. These methods are well suited to stochastic tasks and to tasks in which a complete and accurate model is not available. For tasks too large to implement the situation-action mapping as a table, supervised-learning methods must be used, and their capabilities remain a significant limitation of the approach. | [
523,
565,
566,
653,
2485
] | Train |
2,481 | 6 | Title: The Design and Evaluation of a Rule Induction Algorithm
Abstract: technical report BYU-CS-93-11 June 1993 | [
1858
] | Test |
2,482 | 0 | Title: CBR for Document Retrieval: The FAllQ Project
Abstract: This paper reports about a project on document retrieval in an industrial setting. The objective is to provide a tool that helps finding documents related to a given query, such as answers in Frequently Asked Questions databases. A CBR approach has been used to develop a running prototypical system which is currently under practical evaluation. | [
1854,
1855,
2123,
2645
] | Train |
2,483 | 6 | Title: How Many Queries are Needed to Learn?
Abstract: We investigate the query complexity of exact learning in the membership and (proper) equivalence query model. We give a complete characterization of concept classes that are learnable with a polynomial number of polynomial sized queries in this model. We give applications of this characterization, including results on learning a natural subclass of DNF formulas, and on learning with membership queries alone. Query complexity has previously been used to prove lower bounds on the time complexity of exact learning. We show a new relationship between query complexity and time complexity in exact learning: If any "honest" class is exactly and properly learnable with polynomial query complexity, but not learnable in polynomial time, then P 6= NP. In particular, we show that an honest class is exactly polynomial-query learnable if and only if it is learnable using an oracle for p | [
1003,
1004,
1848
] | Test |
2,484 | 0 | Title: The evaluation of Anapron: A case study in evaluating a case-based system
Abstract: This paper presents a case study in evaluating a case-based system. It describes the evaluation of Anapron, a system that pronounces names by a combination of rule-based and case-based reasoning. Three sets of experiments were run on Anapron: a set of exploratory measurements to profile the system's operation; a comparison between Anapron and other name-pronunciation systems; and a set of studies that modified various parts of the system to isolate the contribution of each. Lessons learned from these experiments for CBR evaluation methodology and for CBR theory are discussed. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories of Cambridge, Massachusetts; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories. All rights reserved. | [
986,
1644,
2614,
2616
] | Test |
2,485 | 4 | Title: Tight Performance Bounds on Greedy Policies Based on Imperfect Value Functions
Abstract: Consider a given value function on states of a Markov decision problem, as might result from applying a reinforcement learning algorithm. Unless this value function equals the corresponding optimal value function, at some states there will be a discrepancy, which is natural to call the Bellman residual, between what the value function specifies at that state and what is obtained by a one-step lookahead along the seemingly best action at that state using the given value function to evaluate all succeeding states. This paper derives a tight bound on how far from optimal the discounted return for a greedy policy based on the given value function will be as a function of the maximum norm magnitude of this Bellman residual. A corresponding result is also obtained for value functions defined on state-action pairs, as are used in Q-learning. One significant application of these results is to problems where a function approximator is used to learn a value function, with training of the approxi-mator based on trying to minimize the Bellman residual across states or state-action pairs. When control is based on the use of the resulting value function, this result provides a link between how well the objectives of function approximator training are met and the quality of the resulting control. | [
173,
565,
566,
575,
749,
1378,
1816,
2480
] | Train |
2,486 | 2 | Title: The Canonical Distortion Measure for Vector Quantization and Function Approximation
Abstract: To measure the quality of a set of vector quantization points a means of measuring the distance between a random point and its quantization is required. Common metrics such as the Hamming and Euclidean metrics, while mathematically simple, are inappropriate for comparing natural signals such as speech or images. In this paper it is shown how an environment of functions on an input space X induces a canonical distortion measure (CDM) on X. The depiction canonical is justified because it is shown that optimizing the reconstruction error of X with respect to the CDM gives rise to optimal piecewise constant approximations of the functions in the environment. The CDM is calculated in closed form for several different function classes. An algorithm for training neural networks to implement the CDM is presented along with some en couraging experimental results. | [
1970,
2586
] | Train |
2,487 | 6 | Title: An Optimized Theory Revision Module
Abstract: Theory revision systems typically use a set of theory-to-theory transformations f k g to hill-climb from a given initial theory to a new theory whose empirical accuracy, over a given set of labeled training instances fc j g, is a local maximum. At the heart of each such process is an "evaluator", which compares the accuracy of the current theory KB with that of each of its "neighbors" f k (KB)g, with the goal of determining which neighbor has the highest accuracy. The obvious "wrapper" evaluator simply evaluates each individual neighbor theory KB k = k (KB) on each instance c j . As it can be very expensive to evaluate a single theory on a single instance, and there can be a great many training instances and a huge number of neighbors, this approach can be prohibitively slow. We present an alternative system which employs a smarter evaluator that quickly computes the accuracy of a transformed theory k (KB) by "looking inside" KB and reasoning about the effects of the k transformation. We compare the performance of with the naive wrapper system on real-world theories obtained from a fielded expert system, and find that runs over 35 times faster than , while attaining the same accuracy. This paper also discusses 's source of power. Keywords: theory revision, efficient algorithm, hill-climbing system Multiple Submissions: We have submited a related version of this paper to AAAI96. fl We gratefully acknowledge the many helpful comments on this report from George Drastal, Chandra Mouleeswaran and Geoff Towell. | [
52,
136,
430,
1823
] | Train |
2,488 | 3 | Title: Density and hazard rate estimation for right censored data using wavelet methods
Abstract: This paper describes a wavelet method for the estimation of density and hazard rate functions from randomly right censored data. We adopt a nonparametric approach in assuming that the density and hazard rate have no specific parametric form. The method is based on dividing the time axis into a dyadic number of intervals and then counting the number of events within each interval. The number of events and the survival function of the observations are then separately smoothed over time via linear wavelet smoothers, and then the hazard rate function estimators are obtained by taking the ratio. We prove that the estimators possess pointwise and global mean square consistency, obtain the best possible asymptotic MISE convergence rate and are also asymptotically normally distributed. We also describe simulation experiments that show these estimators are reasonably reliable in practice. The method is illustrated with two real examples. The first uses survival time data for patients with liver metastases from a colorectal primary tumour without other distant metastases. The second is concerned with times of unemployment for women and the wavelet estimate, through its flexibility, provides a new and interesting interpretation. | [
1910
] | Train |
2,489 | 0 | Title: BECOMING AN EXPERT CASE-BASED REASONER: LEARNING TO ADAPT PRIOR CASES
Abstract: Experience plays an important role in the development of human expertise. One computational model of how experience affects expertise is provided by research on case-based reasoning, which examines how stored cases encapsulating traces of specific prior problem-solving episodes can be retrieved and re-applied to facilitate new problem-solving. Much progress has been made in methods for accessing relevant cases, and case-based reasoning is receiving wide acceptance both as a technology for developing intelligent systems and as a cognitive model of a human reasoning process. However, one important aspect of case-based reasoning remains poorly understood: the process by which retrieved cases are adapted to fit new situations. The difficulty of encoding effective adaptation rules by hand is widely recognized as a serious impediment to the development of fully autonomous case-based reasoning systems. Consequently, an important question is how case-based reasoning systems might learn to improve their expertise at case adaptation. We present a framework for acquiring this expertise by using a combination of general adaptation rules, introspective reasoning, and case-based reasoning about the case adaptation task itself. | [
643,
1126,
2371,
2372
] | Train |
2,490 | 1 | Title: Computer Evolution of Buildable Objects for Evolutionary Design by Computers
Abstract: Experience plays an important role in the development of human expertise. One computational model of how experience affects expertise is provided by research on case-based reasoning, which examines how stored cases encapsulating traces of specific prior problem-solving episodes can be retrieved and re-applied to facilitate new problem-solving. Much progress has been made in methods for accessing relevant cases, and case-based reasoning is receiving wide acceptance both as a technology for developing intelligent systems and as a cognitive model of a human reasoning process. However, one important aspect of case-based reasoning remains poorly understood: the process by which retrieved cases are adapted to fit new situations. The difficulty of encoding effective adaptation rules by hand is widely recognized as a serious impediment to the development of fully autonomous case-based reasoning systems. Consequently, an important question is how case-based reasoning systems might learn to improve their expertise at case adaptation. We present a framework for acquiring this expertise by using a combination of general adaptation rules, introspective reasoning, and case-based reasoning about the case adaptation task itself. | [
1807
] | Train |
2,491 | 2 | Title: Prosopagnosia in Modular Neural Network Models
Abstract: There is strong evidence that face processing in the brain is localized. The double dissociation between prosopagnosia, a face recognition deficit occurring after brain damage, and visual object agnosia, difficulty recognizing other kinds of complex objects, indicates that face and non-face object recognition may be served by partially independent neural mechanisms. In this chapter, we use computational models to show how the face processing specialization apparently underlying prosopagnosia and visual object agnosia could be attributed to 1) a relatively simple competitive selection mechanism that, during development, devotes neural resources to the tasks they are best at performing, 2) the developing infant's need to perform subordinate classification (identification) of faces early on, and 3) the infant's low visual acuity at birth. Inspired by de Schonen and Mancini's (1998) arguments that factors like these could bias the visual system to develop a specialized face processor, and Jacobs and Kosslyn's (1994) experiments in the mixtures of experts (ME) modeling paradigm, we provide a preliminary computational demonstration of how this theory accounts for the double dissociation between face and object processing. We present two feed-forward computational models of visual processing. In both models, the selection mechanism is a gating network that mediates a competition between modules attempting to classify input stimuli. In Model I, when the modules are simple unbiased classifiers, the competition is sufficient to achieve enough of a specialization that damaging one module impairs the model's face recognition more than its object recognition, and damaging the other module impairs the model's object recognition more than its face recognition. In Model II, however, we bias the modules by providing one with low spatial frequency information and the other with high spatial frequency information. In this case, when the model's task is subordinate classification of faces and superordinate classification of objects, the low spatial frequency network shows an even stronger specialization for faces. No other combination of tasks and inputs shows this strong specialization. We take these results as support for the idea that something resembling a face processing "module" could arise as a natural consequence of the infant's developmental environment without being innately specified. | [
1981
] | Train |
2,492 | 3 | Title: Robust Parameter Learning in Bayesian Networks with Missing Data
Abstract: There is strong evidence that face processing in the brain is localized. The double dissociation between prosopagnosia, a face recognition deficit occurring after brain damage, and visual object agnosia, difficulty recognizing other kinds of complex objects, indicates that face and non-face object recognition may be served by partially independent neural mechanisms. In this chapter, we use computational models to show how the face processing specialization apparently underlying prosopagnosia and visual object agnosia could be attributed to 1) a relatively simple competitive selection mechanism that, during development, devotes neural resources to the tasks they are best at performing, 2) the developing infant's need to perform subordinate classification (identification) of faces early on, and 3) the infant's low visual acuity at birth. Inspired by de Schonen and Mancini's (1998) arguments that factors like these could bias the visual system to develop a specialized face processor, and Jacobs and Kosslyn's (1994) experiments in the mixtures of experts (ME) modeling paradigm, we provide a preliminary computational demonstration of how this theory accounts for the double dissociation between face and object processing. We present two feed-forward computational models of visual processing. In both models, the selection mechanism is a gating network that mediates a competition between modules attempting to classify input stimuli. In Model I, when the modules are simple unbiased classifiers, the competition is sufficient to achieve enough of a specialization that damaging one module impairs the model's face recognition more than its object recognition, and damaging the other module impairs the model's object recognition more than its face recognition. In Model II, however, we bias the modules by providing one with low spatial frequency information and the other with high spatial frequency information. In this case, when the model's task is subordinate classification of faces and superordinate classification of objects, the low spatial frequency network shows an even stronger specialization for faces. No other combination of tasks and inputs shows this strong specialization. We take these results as support for the idea that something resembling a face processing "module" could arise as a natural consequence of the infant's developmental environment without being innately specified. | [
577,
1900,
2461,
2547
] | Test |
2,493 | 5 | Title: Relational Knowledge Discovery in Databases
Abstract: In this paper, we indicate some possible applications of ILP or similar techniques in the knowledge discovery field, and then discuss several methods for adapting and linking ILP-systems to relational database systems. The proposed methods range from "pure ILP" to "based on techniques originating in ILP". We show that it is both easy and advantageous to adapt ILP-systems in this way. | [
1428,
2426
] | Train |
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