Semantics for Disjunctive Logic Programs with Explicit and Default Negation

The use of explicit negation enhances the expressive power of logic programs by providing a natural and unambiguous way to assert negated information about the domain being represented. We study the semantics of disjunctive programs that contain both explicit negation and negation-by-default, called extended disjunctive logic programs. General techniques are described for extending model, xpoint, and proof theoretic characterizations of an arbitrary semantics of normal disjunctive logic programs to cover the class of extended programs. Illustrations of these techniques are given for stable models, disjunctive well-founded and stationary semantics. The declarative complexity of the extended programs, as well as the algorithmic complexity of the proof procedures and xpoint operators, are discussed.