Understanding Negation in Logic Programming
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. We
have described general techniques for extending model, fixpoint, and
proof theoretic characterizations of an arbitrary semantics of normal
disjunctive logic programs to cover the class of extended programs, and
have given illustrations of these techniques for stable models, minimal
Herbrand models, disjunctive well-founded and stationary semantics. In
addition, we have studied the declarative complexity of the extended
programs, as well as the algorithmic complexity of the proof procedures
and fixpoint operators. Currently, we are investigating the semantics
of disjunctive logic programs containing several kinds of
default negation in addition to explicit.
Participants:
Publications available on-line: