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A Method for Measuring Wide Range Performance of Boolean Queries in FullText Databases
, 2000
"... A new laboratorybased method for the evaluation of Boolean queries in freetext searching of fulltext databases is proposed. The method is based on a controlled formulation of inclusive query plans, on an automatic conversion of query plans into a set of elementary queries, and on composing optima ..."
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Cited by 24 (7 self)
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A new laboratorybased method for the evaluation of Boolean queries in freetext searching of fulltext databases is proposed. The method is based on a controlled formulation of inclusive query plans, on an automatic conversion of query plans into a set of elementary queries, and on composing optimal queries at varying operational levels by combining appropriate subsets of elementary queries. The method is based on the idea of reverse engineering, and exploits full relevance data of documents to find the query performing optimally within given operational constraints. The proposed
An Algebra for Cyclic Ordering of 2D Orientation
 in Proceedings AAAI98
, 1998
"... We define an algebra of ternary relations for cyclic ordering of 2D orientations. The algebra (1) is a refinement of the CYCORD theory; (2) contains 24 atomic relations, hence 2 24 general relations, of which the usual CYCORD relation is a particular relation; and (3) is NPcomplete, which is not ..."
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Cited by 9 (3 self)
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We define an algebra of ternary relations for cyclic ordering of 2D orientations. The algebra (1) is a refinement of the CYCORD theory; (2) contains 24 atomic relations, hence 2 24 general relations, of which the usual CYCORD relation is a particular relation; and (3) is NPcomplete, which is not surprising since the CYCORD theory is. We then provide: (1) a constraint propagation algorithm for the algebra, which we show is polynomial, and complete for a subclass including all atomic relations; (2) a proof that another subclass, expressing only information on parallel orientations, is NPcomplete; and (3) a solution search algorithm for a general problem expressed in the algebra. Introduction Qualitative spatial reasoning (QSR) has become an important and challenging research area of Artificial Intelligence. An important aspect of it is topological reasoning (e.g. (Cohn 1997)). However, many applications (e.g., robot navigation (Levitt & Lawton 1990), reasoning about shape (Schlieder...
A Parallel Abductive Query Answering in Probabilistic Logic Programs
"... Actionprobabilistic logic programs (apprograms) are a class of probabilistic logic programs that have been extensively used during the last few years for modeling behaviors of entities. Rules in apprograms have the form “If the environment in which entity E operates satisfies certain conditions, ..."
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Cited by 1 (1 self)
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Actionprobabilistic logic programs (apprograms) are a class of probabilistic logic programs that have been extensively used during the last few years for modeling behaviors of entities. Rules in apprograms have the form “If the environment in which entity E operates satisfies certain conditions, then the probability that E will take some action A is between L and U”. Given an approgram, we are interested in trying to change the environment, subject to some constraints, so that the probability that entity E takes some action (or combination of actions) is maximized. This is called the Basic Abductive Query Answering Problem (BAQA). We first formally define and study the complexity of BAQA, and then go on to provide an exact (exponential time) algorithm to solve it, followed by more efficient algorithms for specific subclasses of the problem. We also develop appropriate heuristics to solve BAQA efficiently. The second problem, called the Costbased Query Answering (CBQA) problem checks to see if there is some way of achieving a desired action (or set of actions) with a probability exceeding a threshold, given certain costs. We first formally define and study an exact (intractable) approach to CBQA, and then go on to propose a more efficient algorithm for a specific subclass of apprograms that builds on the results for the basic version of this problem. We also develop the first algorithms for parallel evaluation of CBQA. We conclude with an extensive report on experimental evaluations performed over prototype implementations of the algorithms developed for both BAQA and CBQA, showing that our parallel algorithms work well in practice.
A Bayesian Approach to Cluster Validation
"... In this paper, we propose a novel approach to validating clusterings. We treat a given clustering as a baseline and define a collection of perturbations of it that give possibly different assignment of points to clusters. If these are indexed by a hyperparameter, integrating with respect to a prior ..."
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In this paper, we propose a novel approach to validating clusterings. We treat a given clustering as a baseline and define a collection of perturbations of it that give possibly different assignment of points to clusters. If these are indexed by a hyperparameter, integrating with respect to a prior gives an averaged assignment matrix. This matrix can be visualized as a heat map, allowing clusterings and their stability properties to be readily seen. The difference between an averaged assignment matrix and the baseline gives a measure of the stability of the baseline. This approach motivates a general and computationally fast algorithm for evaluating the stability of distancebased and exponentialmodel type clusterings, including kmeans. In addition, these criteria can be used to choose the optimal number of clusters. Our method compares favorably with data based perturbation procedures, such as subsampling, in some conditions such as small sample size. In addition, there is evidence that our method performs better relative to subsampling methods on some problems. 1
Qualitative Spatial Reasoning h la Allen: An Algebra for Cyclic Ordering of 2D Orientations
"... We define an algebra of ternary relations for cyclic ordering of 2D orientations, which is a refinement of the CYCORD theory. The algebra (1) contains atomic relations, hence 224 general relations, of which the usual CYCORD relation is a particular relation; and (2) is NPcomplete, which is not surp ..."
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We define an algebra of ternary relations for cyclic ordering of 2D orientations, which is a refinement of the CYCORD theory. The algebra (1) contains atomic relations, hence 224 general relations, of which the usual CYCORD relation is a particular relation; and (2) is NPcomplete, which is not surprising since the CYCORD theory is. We then provide the following: (1) a constraint propagation algorithm for the algebra; (2) a proof that the propagation algorithm polynomial, and complete for a subclass including all atomic relations; (3) a proof that another subclass, expressing only information on parallel orientations, is NPcomplete; and (4) a solution search algorithm for a general problem expressed in the algebra. A comparison to related work indicates that the approach is promising.