Results 11  20
of
673
Answer Set Planning
"... In "answer set programming," solutions to a problem are represented by answer sets, and not by answer substitutions produced in response to a query, as in conventional logic programming. Instead of Prolog, answer set programming uses software systems capable of computing answer sets. This paper is a ..."
Abstract

Cited by 150 (5 self)
 Add to MetaCart
In "answer set programming," solutions to a problem are represented by answer sets, and not by answer substitutions produced in response to a query, as in conventional logic programming. Instead of Prolog, answer set programming uses software systems capable of computing answer sets. This paper is about applications of this idea to planning.
Propositional Semantics for Disjunctive Logic Programs
 Annals of Mathematics and Artificial Intelligence
, 1994
"... In this paper we study the properties of the class of headcyclefree extended disjunctive logic programs (HEDLPs), which includes, as a special case, all nondisjunctive extended logic programs. We show that any propositional HEDLP can be mapped in polynomial time into a propositional theory such th ..."
Abstract

Cited by 145 (2 self)
 Add to MetaCart
In this paper we study the properties of the class of headcyclefree extended disjunctive logic programs (HEDLPs), which includes, as a special case, all nondisjunctive extended logic programs. We show that any propositional HEDLP can be mapped in polynomial time into a propositional theory such that each model of the latter corresponds to an answer set, as defined by stable model semantics, of the former. Using this mapping, we show that many queries over HEDLPs can be determined by solving propositional satisfiability problems. Our mapping has several important implications: It establishes the NPcompleteness of this class of disjunctive logic programs; it allows existing algorithms and tractable subsets for the satisfiability problem to be used in logic programming; it facilitates evaluation of the expressive power of disjunctive logic programs; and it leads to the discovery of useful similarities between stable model semantics and Clark's predicate completion. 1 Introduction ...
Preferred Answer Sets for Extended Logic Programs
 ARTIFICIAL INTELLIGENCE
, 1998
"... In this paper, we address the issue of how Gelfond and Lifschitz's answer set semantics for extended logic programs can be suitably modified to handle prioritized programs. In such programs an ordering on the program rules is used to express preferences. We show how this ordering can be used to de ..."
Abstract

Cited by 131 (17 self)
 Add to MetaCart
In this paper, we address the issue of how Gelfond and Lifschitz's answer set semantics for extended logic programs can be suitably modified to handle prioritized programs. In such programs an ordering on the program rules is used to express preferences. We show how this ordering can be used to define preferred answer sets and thus to increase the set of consequences of a program. We define a strong and a weak notion of preferred answer sets. The first takes preferences more seriously, while the second guarantees the existence of a preferred answer set for programs possessing at least one answer set. Adding priorities
On the Computational Cost of Disjunctive Logic Programming: Propositional Case
, 1995
"... This paper addresses complexity issues for important problems arising with disjunctive logic programming. In particular, the complexity of deciding whether a disjunctive logic program is consistent is investigated for a variety of wellknown semantics, as well as the complexity of deciding whethe ..."
Abstract

Cited by 113 (26 self)
 Add to MetaCart
This paper addresses complexity issues for important problems arising with disjunctive logic programming. In particular, the complexity of deciding whether a disjunctive logic program is consistent is investigated for a variety of wellknown semantics, as well as the complexity of deciding whether a propositional formula is satised by all models according to a given semantics. We concentrate on nite propositional disjunctive programs with as wells as without integrity constraints, i.e., clauses with empty heads; the problems are located in appropriate slots of the polynomial hierarchy. In particular, we show that the consistency check is P 2 complete for the disjunctive stable model semantics (in the total as well as partial version), the iterated closed world assumption, and the perfect model semantics, and we show that the inference problem for these semantics is P 2 complete; analogous results are derived for the an
Nested expressions in logic programs
 Annals of Mathematics and Artificial Intelligence
, 1999
"... We extend the answer set semantics to a class of logic programs with nested expressions permitted in the bodies and heads of rules. These expressions are formed from literals using negation as failure, conjunction (,) and disjunction (;) that can be nested arbitrarily. Conditional expressions are in ..."
Abstract

Cited by 111 (13 self)
 Add to MetaCart
We extend the answer set semantics to a class of logic programs with nested expressions permitted in the bodies and heads of rules. These expressions are formed from literals using negation as failure, conjunction (,) and disjunction (;) that can be nested arbitrarily. Conditional expressions are introduced as abbreviations. The study of equivalent transformations of programs with nested expressions shows that any such program is equivalent to a set of disjunctive rules, possibly with negation as failure in the heads. The generalized answer set semantics is related to the LloydTopor generalization of Clark's completion and to the logic of minimal belief and negation as failure.
A Deductive System for NonMonotonic Reasoning
, 1997
"... Disjunctive Deductive Databases (DDDBs)  functionfree disjunctive logic programs with negation in rule bodies allowed  have been recently recognized as a powerful tool for knowledge representation and commonsense reasoning. Much research has been spent on issues like semantics and complexity ..."
Abstract

Cited by 102 (21 self)
 Add to MetaCart
Disjunctive Deductive Databases (DDDBs)  functionfree disjunctive logic programs with negation in rule bodies allowed  have been recently recognized as a powerful tool for knowledge representation and commonsense reasoning. Much research has been spent on issues like semantics and complexity of DDDBs, but the important area of implementing DDDBs has been less addressed so far. However, a thorough investigation thereof is a basic requirement for building systems which render previous foundational work on DDDBs useful for practice. This paper presents the architecture of a DDDB system currently developed at TU Vienna in the FWF project P11580MAT "A Query System for Disjunctive Deductive Databases".
Answer Sets in General Nonmonotonic Reasoning (Preliminary Report)
, 1992
"... Languages of declarative logic programming differ from other modal nonmonotonic formalisms by lack of syntactic uniformity. For instance, negation as failure can be used in the body of a rule, but not in the head; in disjunctive programs, disjunction is used in the head of a rule, but not in the bod ..."
Abstract

Cited by 102 (9 self)
 Add to MetaCart
Languages of declarative logic programming differ from other modal nonmonotonic formalisms by lack of syntactic uniformity. For instance, negation as failure can be used in the body of a rule, but not in the head; in disjunctive programs, disjunction is used in the head of a rule, but not in the body; in extended programs, negation as failure can be used on top of classical negation, but not the other way around. We argue that this lack of uniformity should not be viewed as a distinguishing feature of logic programming in general. As a starting point, we take a translation from the language of disjunctive programs with negation as failure and classical negation into MBNFthe logic of minimal belief and negation as failure. A class of theories based on this logic is defined, theories with protected literals, which is syntactically uniform and contains the translations of all programs. We show that theories with protected literals have a semantics similar to the answer set semantics us...
Temporal Reasoning in Logic Programming: A Case for the Situation Calculus
 IN PROCEEDINGS OF 10TH INTERNATIONAL CONFERENCE IN LOGIC PROGRAMMING, HUNGARY
, 1993
"... We propose, and axiomatize, an extended version of the situation calculus [10] for temporal reasoning in a logic programming framework. This extended language provides for a linear temporal structure, which may be viewed as a path of actual event occurrences within the tree of possible situations ..."
Abstract

Cited by 86 (5 self)
 Add to MetaCart
We propose, and axiomatize, an extended version of the situation calculus [10] for temporal reasoning in a logic programming framework. This extended language provides for a linear temporal structure, which may be viewed as a path of actual event occurrences within the tree of possible situations of the "classical" situation calculus. The extended language provides for events to occur and fluents to hold at specific points in time. As a result, it is possible to establish a close correspondence between this extended situation calculus and other linear time formalisms which have been proposed in opposition to the situation calculus. In particular, we argue that the functionality of the event calculus [6] is subsumed by the extended situation calculus. We present a logic program for temporal reasoning which is provably sound for our axiomatization, relative to the Clark completion semantics of the program. Our logic programming approach has the advantage of being grounded in a pure (without negation as failure) first order axiomatization suitable for reasoning about events and their occurrences. Moreover, efficient algorithms can be obtained for a suitable class of temporal reasoning problems, following the ideas of Kowalski [5].
Logic Programming and Knowledge Representation  the AProlog perspective
 Artificial Intelligence
, 2002
"... In this paper we give a short introduction to logic programming approach to knowledge representation and reasoning. The intention is to help the reader to develop a 'feel' for the field's history and some of its recent developments. The discussion is mainly limited to logic programs under the answer ..."
Abstract

Cited by 84 (0 self)
 Add to MetaCart
In this paper we give a short introduction to logic programming approach to knowledge representation and reasoning. The intention is to help the reader to develop a 'feel' for the field's history and some of its recent developments. The discussion is mainly limited to logic programs under the answer set semantics. For understanding of approaches to logic programming build on wellfounded semantics, general theories of argumentation, abductive reasoning, etc., the reader is referred to other publications.
Representing Actions In Logic Programs And Default Theories
, 1997
"... We address the problem of representing commonsense knowledge about action domains in the formalisms of logic programming and default logic. We employ a methodology proposed by Gelfond and Lifschitz which involves first defining a highlevel language for representing commonsense knowledge about actio ..."
Abstract

Cited by 84 (7 self)
 Add to MetaCart
We address the problem of representing commonsense knowledge about action domains in the formalisms of logic programming and default logic. We employ a methodology proposed by Gelfond and Lifschitz which involves first defining a highlevel language for representing commonsense knowledge about actions, and then specifying a translation from the highlevel action language into a generalpurpose formalism, such as logic programming. Accordingly, we define a highlevel action language AC, and specify sound and complete translations of portions of AC into logic programming and default logic. The language AC includes "static causal laws" of the following kind: a fluent formula F can be made true by making a fluent formula G true (or, more precisely, F is caused whenever G is caused). Such propositions are more expressive than the state constraints traditionally used to represent background knowledge. Our translations of AC into logic programming and default logic are simple in part because the noncontrapositive nature of causal laws is easily reflected in such rulebased formalisms.