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46
A Survey on Knowledge Compilation
, 1998
"... this paper we survey recent results in knowledge compilation of propositional knowledge bases. We first define and limit the scope of such a technique, then we survey exact and approximate knowledge compilation methods. We include a discussion of compilation for nonmonotonic knowledge bases. Keywor ..."
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Cited by 119 (4 self)
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this paper we survey recent results in knowledge compilation of propositional knowledge bases. We first define and limit the scope of such a technique, then we survey exact and approximate knowledge compilation methods. We include a discussion of compilation for nonmonotonic knowledge bases. Keywords: Knowledge Representation, Efficiency of Reasoning
Updating description logic aboxes
 In International Conference of Principles of Knowledge Representation and Reasoning(KR
, 2006
"... Description logic (DL) ABoxes are a tool for describing the state of affairs in an application domain. In this paper, we consider the problem of updating ABoxes when the state changes. We assume that changes are described at an atomic level, i.e., in terms of possibly negated ABox assertions that in ..."
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Cited by 76 (5 self)
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Description logic (DL) ABoxes are a tool for describing the state of affairs in an application domain. In this paper, we consider the problem of updating ABoxes when the state changes. We assume that changes are described at an atomic level, i.e., in terms of possibly negated ABox assertions that involve only atomic concepts and roles. We analyze such basic ABox updates in several standard DLs by investigating whether the updated ABox can be expressed in these DLs and, if so, whether it is computable and what is its size. It turns out that DLs have to include nominals and the “@” constructor of hybrid logic (or, equivalently, admit Boolean ABoxes) for updated ABoxes to be expressible. We devise algorithms to compute updated ABoxes in several expressive DLs and show that an exponential blowup in the size of the whole input (original ABox + update information) cannot be avoided unless every PTIME problem is LOGTIMEparallelizable. We also exhibit ways to avoid an exponential blowup in the size of the original ABox, which is usually large compared to the update information.
Preprocessing of Intractable Problems
 Information and Computation
, 1997
"... Some computationally hard problems e.g., deduction in logical knowledge bases are such that part of an instance is known well before the rest of it, and remains the same for several subsequent instances of the problem. In these cases, it is meaningful to preprocess offline this known part so as ..."
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Cited by 46 (15 self)
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Some computationally hard problems e.g., deduction in logical knowledge bases are such that part of an instance is known well before the rest of it, and remains the same for several subsequent instances of the problem. In these cases, it is meaningful to preprocess offline this known part so as to simplify the remaining online problem. In this paper we investigate such a technique in the context of intractable, i.e., NPhard, problems. Recent results in the literature show that not all NPhard problems behave in the same way: for some of them preprocessing yields polynomialtime online simplified problems (we call them compilable), while for other ones there is strong evidence that this should not happen. Our primary goal is to provide a sound methodology that can be used either to prove or disprove that a problem is compilable. To this end, we define new models of computation, complexity classes, and reductions. We find complete problems for such classes, completeness meaning...
How Hard is it to Revise a Belief Base?
, 1996
"... If a new piece of information contradicts our previously held beliefs, we have to revise our beliefs. This problem of belief revision arises in a number of areas in Computer Science and Artificial Intelligence, e.g., in updating logical database, in hypothetical reasoning, and in machine learning. M ..."
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Cited by 43 (0 self)
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If a new piece of information contradicts our previously held beliefs, we have to revise our beliefs. This problem of belief revision arises in a number of areas in Computer Science and Artificial Intelligence, e.g., in updating logical database, in hypothetical reasoning, and in machine learning. Most of the research in this area is influenced by work in philosophical logic, in particular by Gardenfors and his colleagues, who developed the theory of belief revision. Here we will focus on the computational aspects of this theory, surveying results that address the issue of the computational complexity of belief revision.
Knowledge Representation with Logic Programs
 DEPT. OF CS OF THE UNIVERSITY OF KOBLENZLANDAU
, 1996
"... In this tutorialoverview, which resulted from a lecture course given by the authors at ..."
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Cited by 38 (6 self)
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In this tutorialoverview, which resulted from a lecture course given by the authors at
On Compact Representations of Propositional Circumscription
 Theoretical Computer Science
, 1997
"... . We prove that  unless the polynomial hierarchy collapses at the second level  the size of a purely propositional representation of the circumscription CIRC(T ) of a propositional formula T grows faster than any polynomial as the size of T increases. We then analyze the significance of this res ..."
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Cited by 37 (14 self)
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. We prove that  unless the polynomial hierarchy collapses at the second level  the size of a purely propositional representation of the circumscription CIRC(T ) of a propositional formula T grows faster than any polynomial as the size of T increases. We then analyze the significance of this result in the related field of closedworld reasoning. Appeared on the Proceedings of the 12th Symposium on Theoretical Aspects of Computer Science (STACS'95) March 24, 1995, Munchen, Germany Lecture Notes in Computer Science, 900, pages 205216, SpringerVerlag 1 Introduction Reasoning with selected (or intended) models of a logical formula is a common reasoning technique used in Databases, Logic Programming, Knowledge Representation and Artificial Intelligence (AI). One of the most popular criteria for selecting intended models is minimality wrt the set of true atoms. The idea behind minimality is to assume that a fact is false whenever possible. Such a criterion allows one to represent o...
Distancebased merging: A general framework and some complexity results
, 2001
"... The importance of belief merging is reflected by the abundance of the literature about it for the last years. In the following, a model for belief merging based on distances is introduced; many merging operators already pointed out so far can be recovered as specific instances of this model. We inve ..."
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Cited by 27 (9 self)
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The importance of belief merging is reflected by the abundance of the literature about it for the last years. In the following, a model for belief merging based on distances is introduced; many merging operators already pointed out so far can be recovered as specific instances of this model. We investigate the computational aspects of such distancebased operators and give two general results showing that the complexity of inference for them is at the first level of the polynomial hierarchy (under very weak assumptions). Then some specific distancebased operators are considered and their complexity is identified. Finally, distancebased merging operators are investigated from the logical point of view.
Reducing Belief Revision to Circumscription (and viceversa)
, 2002
"... Nonmonotonic formalisms and belief revision operators have been introduced as useful tools to describe and reason about evolving scenarios. Both approaches have been proven effective in a number of different situations. However, little is known about their relationship. Previous work by Winslett ha ..."
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Cited by 22 (4 self)
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Nonmonotonic formalisms and belief revision operators have been introduced as useful tools to describe and reason about evolving scenarios. Both approaches have been proven effective in a number of different situations. However, little is known about their relationship. Previous work by Winslett has shown some correlations between a specific operator and circumscription. In this paper we greatly extend Winslett’s work by establishing new relations between circumscription and a large number of belief revision operators. This highlights similarities and differences between these formalisms. Furthermore, these connections provide us with the possibility of importing results in one field into the other one.
The Complexity of Iterated Belief Revision
 In Proceedings of the Sixth International Conference on Database Theory (ICDT'97
, 1997
"... In this paper we analyze the complexity of revising a knowledge base when an iteration of this process is necessary. The analysis concerns both the classical problems of belief revision (inference, model checking, computation of the new base) and new issues, related to the problem of "committin ..."
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Cited by 21 (4 self)
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In this paper we analyze the complexity of revising a knowledge base when an iteration of this process is necessary. The analysis concerns both the classical problems of belief revision (inference, model checking, computation of the new base) and new issues, related to the problem of "committing" the changes.
Compiling Propositional Weighted Bases
, 2004
"... In this paper, we investigate the extent to which knowledge compilation can be used to improve model checking and inference from propositional weighted bases. We first focus on the compilability issue for both problems, deriving mainly noncompilability results in the case preferences are subject to ..."
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Cited by 21 (7 self)
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In this paper, we investigate the extent to which knowledge compilation can be used to improve model checking and inference from propositional weighted bases. We first focus on the compilability issue for both problems, deriving mainly noncompilability results in the case preferences are subject to change. Then, we present a general notion of ¤normal weighted base that is parametrized by a tractable class ¤ for the clausal entailment problem. We show how every weighted base can be turned (“compiled”) into a queryequivalent ¤normal base whenever ¤ is a complete class for propositional logic. Both negative and positive results are presented. On the one hand, complexity results are identified, showing that the inference problem from a ¤normal weighted base is as difficult as in the general case, when the prime implicates, Horn cover or renamable Horn cover classes are targeted. On the other hand, we show that both the model checking and the (clausal) inference problem become tractable whenever ¥§¦¨¦� ©normal bases are considered. Moreover, we show that the set of all preferred models of a ¥�¦¨¦� ©normal weighted base can be computed in time polynomial in the output size, and as a consequence, model checking is also tractable for such bases. Finally, we sketch how our results can be used in model–based diagnosis in order to compute the most likely diagnoses of a system.