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Reliable Semantics for Extended Logic Programs with Rule Prioritization
 

Summary: Reliable Semantics for Extended Logic Programs with
Rule Prioritization
Anastasia Analyti & Sakti Pramanik
Department of Computer Science, Michigan State University, E. Lansing, MI 48824
E-mail: analyti@cps.msu.edu, pramanik@cpswh.msu.edu
Abstract
We present a new semantics for extended logic programs with rule prioritization (EPP). The semantics,
called reliable semantics (RS), generalizes the well-founded semantics which is defined for normal programs
[34]. It also generalizes the extended well-founded semantics which is defined for non-contradictory extended
programs [24]. Because of the classical negation in the head of the rules, the well-founded model of a
program can be contradictory. RS is contradiction-free and defined for all EPPs. To avoid contradictions,
only reliable rules and reliable closed world assumptions are used in the fixpoint computation of RS. A
closed world assumption (CWA) is considered reliable if it is not "suspect" for any constraint violation. A
rule r is considered reliable if it is not "suspect" for any constraint violation caused by rules with priority
no lower than r. We define the stable r-models of an EPP and we show that the RS of a program coincides
with its least stable r-model. The RS of an EPP, P, represents the skeptical "meaning" of P whereas stable
r-models of P represent the possible "meanings" of P.
Keywords: extended logic programs, rule prioritization, constraint violation, semantics.
1 Introduction
Extended programs are normal programs extended with classical negation. Extended programs pro-

  

Source: Analyti, Anastasia - Institute of Computer Science, Foundation of Research and Technology, Hellas

 

Collections: Computer Technologies and Information Sciences