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37
Relating Defeasible and Normal Logic Programming through Transformation Properties
, 2001
"... This paper relates the Defeasible Logic Programming (DeLP ) framework and its semantics SEM DeLP to classical logic programming frameworks. In DeLP we distinguish between two different sorts of rules: strict and defeasible rules. Negative literals (A) in these rules are considered to represent cl ..."
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Cited by 76 (31 self)
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This paper relates the Defeasible Logic Programming (DeLP ) framework and its semantics SEM DeLP to classical logic programming frameworks. In DeLP we distinguish between two different sorts of rules: strict and defeasible rules. Negative literals (A) in these rules are considered to represent classical negation. In contrast to this, in normal logic programming (NLP ), there is only one kind of rules, but the meaning of negative literals (notA) is different: they represent a kind of negation as failure, and thereby introduce defeasibility. Various semantics have been defined for NLP, notably the wellfounded semantics WFS and the stable semantics Stable. In this paper we consider the transformation properties for NLP introduced by Brass and Dix and suitably adjusted for the DeLP framework. We show which transformation properties are satisfied, thereby identifying aspects in which NLP and DeLP differ. We contend that the transformation rules presented in this paper can he...
TransformationBased BottomUp Computation of the WellFounded Model
, 1997
"... . We present a bottomup algorithm for the computation of the wellfounded model of nondisjunctive logic programs. Our method is based on the elementary program transformations studied by Brass and Dix [6, 7]. However, their "residual program" can grow to exponential size, whereas for fu ..."
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Cited by 51 (4 self)
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. We present a bottomup algorithm for the computation of the wellfounded model of nondisjunctive logic programs. Our method is based on the elementary program transformations studied by Brass and Dix [6, 7]. However, their "residual program" can grow to exponential size, whereas for functionfree programs our "program remainder " is always polynomial in the size, i.e. the number of tuples, of the extensional database (EDB). As in the SLGresolution of Chen and Warren [11, 12, 13], we do not only delay negative but also positive literals if they depend on delayed negative literals. When disregarding goaldirectedness, which needs additional concepts, our approach can be seen as a simplified bottomup version of SLGresolution applicable to rangerestricted Datalog programs. Since our approach is also closely related to the alternating fixpoint procedure [27, 28], it can possibly serve as a basis for an integration of the resolutionbased, fixpointbased, and transformationbased ev...
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
Heterogeneous Active Agents, III: Polynomially Implementable Agents
 Artificial Intelligence
, 2000
"... In [17], two of the authors have introduced techniques to build agents on top of arbitrary data structures, and to "agentize" new/existing programs. They provided a series of successively more sophisticated semantics for such agent systems, and showed that as these semantics become epis ..."
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Cited by 26 (7 self)
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In [17], two of the authors have introduced techniques to build agents on top of arbitrary data structures, and to "agentize" new/existing programs. They provided a series of successively more sophisticated semantics for such agent systems, and showed that as these semantics become epistemically more desirable, a computational price may need to be paid. In this paper, we identify a class of agents that are called weakly regularthis is done by first identifying a fragment of agent programs [17] called weakly regular agent programs (WRAPs for short).
Equivalence in answer set programming
 In Proc. LOPSTR 2001, LNCS 2372
, 2001
"... Abstract. We study the notion of strong equivalence between two Answer Set programs and we show how some particular cases of testing strong equivalence between programs can be reduced to verify if a formula is a theorem in intuitionistic or classical logic. We present some program transformations ..."
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Cited by 25 (5 self)
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Abstract. We study the notion of strong equivalence between two Answer Set programs and we show how some particular cases of testing strong equivalence between programs can be reduced to verify if a formula is a theorem in intuitionistic or classical logic. We present some program transformations for disjunctive programs, which can be used to simplify the structure of programs and reduce their size. These transformations are shown to be of interest for both computational and theoretical reasons. Then we propose how to generalize such transformations to deal with free programs (which allow the use of default negation in the head of clauses). We also present a linear time transformation that can reduce an augmented logic program (which allows nested expressions in both the head and body of clauses) to a program consisting only of standard disjunctive clauses and constraints. 1
A General Theory of Confluent Rewriting Systems for Logic Programming and its Applications
, 2001
"... Recently, Brass and Dix showed (Journal of Automated Reasoning 20(1), 1998) that the wellfounded semantics WFS can be defined as a conuent calculus of transformation rules. This lead not only to a simple extension to disjunctive programs (Journal of Logic Programming 38(3), 1999), but also to a new ..."
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Cited by 22 (13 self)
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Recently, Brass and Dix showed (Journal of Automated Reasoning 20(1), 1998) that the wellfounded semantics WFS can be defined as a conuent calculus of transformation rules. This lead not only to a simple extension to disjunctive programs (Journal of Logic Programming 38(3), 1999), but also to a new computation of the wellfounded semantics which is linear for a broad class of programs. We take this approach as a starting point and generalize it considerably by developing a general theory of Confluent LPSystems CS. Such a system CS is a rewriting system on the set of all logic programs over a fixed signature L and it induces in a natural way a canonical semantics. Moreover, we show four important applications of this theory: (1) most of the wellknown semantics are induced by confluent LPsystems, (2) there are many more transformation rules that lead to confluent LPsystems, (3) semantics induced by such systems can be used to model aggregation, (4) the new systems can be ...
Comparisons and computation of wellfounded semantics for disjunctive logic programs
 ACM Transactions on Computational Logic
, 2005
"... Much work has been done on extending the wellfounded semantics to general disjunctive logic programs and various approaches have been proposed. However, these semantics are different from each other and no consensus is reached about which semantics is the most intended. In this paper we look at dis ..."
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Cited by 18 (4 self)
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Much work has been done on extending the wellfounded semantics to general disjunctive logic programs and various approaches have been proposed. However, these semantics are different from each other and no consensus is reached about which semantics is the most intended. In this paper we look at disjunctive wellfounded reasoning from different angles. We show that there is an intuitive form of the wellfounded reasoning in disjunctive logic programming which can be characterized by slightly modifying some existing approaches to defining disjunctive wellfounded semantics, including program transformations, argumentation, unfounded sets (and resolutionlike procedure). By employing the techniques developed by Brass and Dix in their transformationbased approach, we also provide a bottomup procedure for this semantics. The significance of our work is not only in clarifying the relationship among different approaches, but also shed some light on what is an intended wellfounded semantics for disjunctive logic programs. Categories and Subject Descriptors: F.4.1 [Mathematical Logic and Formal Languages]: Mathematical Logic—logic and constraint programming; computational logic; I.2.3 [Artificial Intelligence]: Deduction and Theorem Proving—logic programming; nonmonotonic reasoning
Disjunctive Logic Programming: A Survey And Assessment
, 2002
"... We describe the elds of disjunctive logic programming and disjunctive deductive databases from the time of their inception to the current time. Contributions with respect to semantics, implementations and applications are surveyed. ..."
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Cited by 17 (0 self)
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We describe the elds of disjunctive logic programming and disjunctive deductive databases from the time of their inception to the current time. Contributions with respect to semantics, implementations and applications are surveyed.
DisLoP: A Research Project on Disjunctive Logic Programming
 AI COMMUNICATIONS
, 1997
"... This paper gives a brief highlevel description of what has been done in the Disjunctive Logic Programmingproject (funded by Deutsche ForschungsGemeinschaft), undertaken by the University of Koblenz since July 1995. We present the main ideas, cite the relevant papers and point to the implemented s ..."
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Cited by 14 (2 self)
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This paper gives a brief highlevel description of what has been done in the Disjunctive Logic Programmingproject (funded by Deutsche ForschungsGemeinschaft), undertaken by the University of Koblenz since July 1995. We present the main ideas, cite the relevant papers and point to the implemented systems and how to access them. This paper also serves as a brief survey of the current status of disjunctive logic programming by highlighting important developments and providing enough pointers for further reading.