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19
Tabled Evaluation with Delaying for General Logic Programs
, 1996
"... SLD resolution with negation as finite failure (SLDNF) reflects the procedural interpretation of predicate calculus as a programming language and forms the computational basis for Prolog systems. Despite its advantages for stackbased memory management, SLDNF is often not appropriate for query evalu ..."
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Cited by 260 (27 self)
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SLD resolution with negation as finite failure (SLDNF) reflects the procedural interpretation of predicate calculus as a programming language and forms the computational basis for Prolog systems. Despite its advantages for stackbased memory management, SLDNF is often not appropriate for query evaluation for three reasons: a) it may not terminate due to infinite positive recursion; b) it may not terminate due to infinite recursion through negation; c) it may repeatedly evaluate the same literal in a rule body, leading to unacceptable performance. We address three problems fir a goaloriented query evaluation of general logic programs by presenting tabled evaluation with delaying (SLG resolution).
Every Logic Program Has a Natural Stratification And an Iterated Least Fixed Point Model (Extended Abstract)
, 1989
"... 1 Introduction The perfect model semantics [ABW88, VG89b, Prz88a, Prz89b] provides an attractive alternative to the traditionally used semantics of logic programs based on Clark's completion of the program [Cla78, Llo84, Fit85, Kun87]. Perfect models are minimal models of the program, which can be ..."
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Cited by 137 (12 self)
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1 Introduction The perfect model semantics [ABW88, VG89b, Prz88a, Prz89b] provides an attractive alternative to the traditionally used semantics of logic programs based on Clark's completion of the program [Cla78, Llo84, Fit85, Kun87]. Perfect models are minimal models of the program, which can be equivalently described as iterated least fixed points of natural operators [ABW88, VG89b], as iterated least models of the program [ABW88, VG89b] or as preferred models with respect to a natural priority relation [Prz88a, Prz89b]. As a result, the perfect model semantics is not only very intuitive, but it also has been proven equivalent to suitable forms of all four major formalizations of nonmonotonic reasoning in AI (see [Prz88b]) and is used in existing database [Zan88] and truth maintenance systems. Additionally, the perfect model semantics eliminates some serious drawbacks of Clark's semantics [Prz89b] and admits a natural sound and complete procedural mechanism, called SLSresolution [...
Modular stratification and magic sets for Datalog programs with negation
 In Proceedings of the ACM Symposium on Principles of Database Systems
, 1990
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On the Declarative and Procedural Semantics of Logic Programs
 Journal of Automated Reasoning
, 1995
"... One of the most important and difficult problems in logic programming is the problem of finding a suitable declarative or intended semantics for logic programs. The importance of this problem stems from the declarative character of logic programming, whereas its difficulty can be largely attributed ..."
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Cited by 65 (8 self)
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One of the most important and difficult problems in logic programming is the problem of finding a suitable declarative or intended semantics for logic programs. The importance of this problem stems from the declarative character of logic programming, whereas its difficulty can be largely attributed to the nonmonotonic character of the negation operator used in logic programs. The problem can therefore be viewed as the problem of finding a suitable formalization of the type of nonmonotonic reasoning used in logic programming. In this paper we introduce a semantics of logic programs based on the class PERF(P) of all, not necessarily Herbrand, perfect models of a program P and we show that the proposed semantics is not only natural but it also combines many of the desirable features of previous approaches, at the same time eliminating some of their drawbacks. For a positive program P, the class PERF(P) of perfect models coincides with the class MIN(P) of all minimal models of P. The per...
A Procedural Semantics for Well Founded Negation in Logic Programs
 Journal of Logic programming
, 1989
"... We introduce global SLSresolution, a procedural semantics for wellfounded negation as defined by Van Gelder, Ross and Schlipf. Global SLSresolution extends Przymusinski 's SLSresolution, and may be applied to all programs, whether locally stratified or not. 1 Global SLSresolution is defined in ..."
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Cited by 54 (2 self)
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We introduce global SLSresolution, a procedural semantics for wellfounded negation as defined by Van Gelder, Ross and Schlipf. Global SLSresolution extends Przymusinski 's SLSresolution, and may be applied to all programs, whether locally stratified or not. 1 Global SLSresolution is defined in terms of global trees, a new data structure representing the dependence of goals on derived negative subgoals. We prove that global SLSresolution is sound with respect to the wellfounded semantics, and complete for nonfloundering queries. While not effective in general, global SLSresolution is effective for classes of "acyclic" programs, and can be augmented with a memoing device to be effective for all functionfree programs. This research was supported by the National Science Foundation under grant IRI8722886, by a grant from IBM Corporation, and by the United States Air Force Office of Scientific Research under contract AFOSR880266. A preliminary version of this paper was presen...
What is Failure? An Approach to Constructive Negation
, 1994
"... A standard approach to negation in logic programming is negation as failure. Its major drawback is that it cannot produce answer substitutions to negated queries. Approaches to overcoming this limitation are termed constructive negation. This work proposes an approach based on construction of failed ..."
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Cited by 53 (4 self)
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A standard approach to negation in logic programming is negation as failure. Its major drawback is that it cannot produce answer substitutions to negated queries. Approaches to overcoming this limitation are termed constructive negation. This work proposes an approach based on construction of failed trees for some instances of a negated query. For this purpose a generalization of the standard notion of a failed tree is needed. We show that a straightforward generalization leads to unsoundness and present a correct one. The method is applicable to arbitrary normal programs. If finitely failed trees are concerned then its semantics is given by Clark completion in 3valued logic (and our approach is a proper extension of SLDNFresolution). If infinite failed trees are allowed then we obtain a method for the wellfounded semantics. In both cases soundness and completeness are proved.
Tabulated Resolution for Well Founded Semantics
 Journal of Logic Programming
, 1993
"... Based on the search forest for positive programs as defined by Bol and Degerstedt, we define a tabulated version of SLSresolution that is sound and complete w.r.t. well founded semantics. In contrast to SLSresolution as proposed by Przymusinski and by Ross, a positivistic computation rule is not ..."
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Cited by 51 (2 self)
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Based on the search forest for positive programs as defined by Bol and Degerstedt, we define a tabulated version of SLSresolution that is sound and complete w.r.t. well founded semantics. In contrast to SLSresolution as proposed by Przymusinski and by Ross, a positivistic computation rule is not required. This proposal is closely related to that of Chen and Warren, but it relies on tabulation for both positive and negative recursion. In this way, only one forest needs to be constructed, rather than a forest for each negative context. For functionfree programs, the resulting search forest is finite. Keywords: logic programming, deductive databases, well founded semantics, tabulation, search forest, SLSresolution, implementation. 1 Introduction It was shown in [5, 24] that bottomup computation with magic templates [2, 22] and tabulated SLDresolution [9, 26, 27] perform `essentially' the same computation. This result is made more precise in [4], where a common framework for both ...
Explicit and Implicit Indeterminism: Reasoning About Uncertain and Contradictory Specifications of Dynamic Systems
 Journal of Logic Programming
, 1997
"... A highlevel action semantics to specify and reason about dynamic systems is presented which supports both uncertain knowledge (taken as explicit indeterminism) and contradictory information (taken as implicit indeterminism). We start by developing an action description language for intentionally re ..."
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Cited by 21 (12 self)
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A highlevel action semantics to specify and reason about dynamic systems is presented which supports both uncertain knowledge (taken as explicit indeterminism) and contradictory information (taken as implicit indeterminism). We start by developing an action description language for intentionally representing nondeterministic actions in dynamic systems. We then study the different possibilities of interpreting contradictory specifications of concurrent actions. We argue that the most reasonable interpretation which allows for exploiting as much information as possible is to take such conflicts as implicit indeterminism. As the second major contribution, we present a calculus for our resulting action semantics based on the logic programming paradigm including negationasfailure and equational theories. Soundness and completeness of this encoding wrt the notion of entailment in our highlevel action language is proved by taking the completion semantics for equational logic programs with...
Constructive Negation and Constraint Logic Programming with Sets
 New Generation Computing
"... The aim of this paper is to extend the Constructive Negation technique to the case of CLP (SET ), a Constraint Logic Programming (CLP ) language based on hereditarily (and hybrid) finite sets. The challenging aspects of the problem originate from the fact that the structure on which CLP (SET ) is ba ..."
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Cited by 8 (5 self)
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The aim of this paper is to extend the Constructive Negation technique to the case of CLP (SET ), a Constraint Logic Programming (CLP ) language based on hereditarily (and hybrid) finite sets. The challenging aspects of the problem originate from the fact that the structure on which CLP (SET ) is based is not admissible closed, and this does not allow to reuse the results presented in the literature concerning the relationships between CLP and constructive negation. We propose a new constraint satisfaction algorithm, capable of correctly handling constructive negation for large classes of CLP (SET ) programs; we also provide a syntactic characterization of such classes of programs. The resulting algorithm provides a novel constraint simplification procedure to handle constructive negation, suitable to theories where unification admits multiple most general unifiers. We also show, using a general result, that it is impossible to construct an interpreter...
Processing Negation and Disjunction in Logic Programs Through Integrity Constraints
 Journal of Intelligent Information Systems
, 1992
"... Integrity constraints were initially defined to verify the correctness of the data that is stored in a database. They were used to restrict the modifications that can be applied to a database. However, there are many other applications in which integrity constraints can play an important role. For e ..."
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Cited by 7 (0 self)
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Integrity constraints were initially defined to verify the correctness of the data that is stored in a database. They were used to restrict the modifications that can be applied to a database. However, there are many other applications in which integrity constraints can play an important role. For example, the semantic query optimization method developed by Chakravarthy, Grant, and Minker for definite deductive databases uses integrity constraints during query processing to prevent the exploration of search space that is bound to fail. In this paper, we generalize the semantic query optimization method to apply to negated atoms. The generalized method is referred to as semantic compilation. This exploration has led to two significant results. First, semantic compilation provides an alternative search space for negative query literals. The alternative search space can find answers in cases for which negationas finitefailure and constructive negation cannot. Second, we show how semant...