A process semantics of logic programs

Abstract

The notions of compositionality and equivalence are fundamental questions in programming language semantics. We focus on these notions and study the semantics of logic programs in the setting of a graph model. We represent a logic program by a graph model, we derive some semantics related to the well-known classic semantics of logic programs (success set, computed answer substitution set and finite failure set). Furthermore we consider the set of partial computations, and prove that is compatible with the set of logic consequences of the program. A simulation equivalence with silent (or invisible) steps on these graphs is also considered, we show that the subsumption equivalence defined on logic programs is compatible with this τ-simulation equivalence. Finally, we prove that the τ-simulation equivalence is a congruence w.r.t two graph combining operators which are the counterpart of the union and hiding operators respectively defined on logic programs.