Abstract

This paper presents a novel approach to the semantics of deductive databases. The possible model semantics is introduced as an alternative approach to the classical minimal model semantics. The possible model semantics can distinguish both inclusive and exclusive disjunctions, and provide a flexible mechanism for inferring negation in disjunctive databases. The possible model semantics is characterized by a new fixpoint semantics of disjunctive databases. A proof procedure called the SLDP -resolution is presented and shown to be sound and complete with respect to the possible model semantics. 1 Introduction The declarative semantics of logic programming and deductive databases has been widely studied based on the minimal model semantics by incorporating an inference rule for negation. For definite Horn databases, the unique least Herbrand model gives a declarative meaning of a program [VK76], and the closed world assumption (CWA) [Rei78] provides negative information as the facts fal...

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