Disjunctive Logic Programming as

Earlier, we have proposed a logic, called priority logic 16, 18], where a theory consists of a collection of logic programming-like inference rules (without default negation) and a priority constraint among them. We showed that nonmonotonic reasoning in general can be viewed as a reasoning based on selecting monotonic inferences that satisfy the speciied priority constraints. The goal of this paper is to investigate how semantics of disjunctive programs can be understood as selecting monotonic inferences. We focus on credulous semantics. We show that the stable semantics of a disjunctive program can be represented by priority logic. The highlight of this paper is an interesting new semantics for disjunctive programs discoved during this study which extends the stable semantics for disjunctive programs in the same way as the regular semantics extends stable semantics for normal programs. This shows that the view of nonmonotonic reasoning in terms of constraint inferences leads to interesting new insights into semantics of nonmonotonic reasoning.