Observational Equivalences for Logic Programs.
Maurizio Gabbrielli, Giorgio Levi, Maria Chiara Meo · 1992
We first introduce a general semantic scheme for logic programs which provides a uniform framework for defining different compositional semantics parametrically wrt a given notion of observable. The equivalence of the operational (top-down) and fixpoint (bottom-up) costruction of the semantics is ensured by the scheme (provided a congruence property is verified). We then define several observational equivalences on logic programs and investigate how they are related. The equivalences are based on various observables (successful derivations, computed answers, partial computed answers and call patterns) and on a notion of program composition. For each observational equivalence we study the relation with a suitable formal semantics, by investigating correctness and full abstraction properties. All the semantics we consider are obtained as instances of the general scheme. 1 Introduction The first application of any semantics is to help understanding the meaning of programs, and program un...