מיכאל קודיש

A denotational, hence, compositional semantics for a a subset of concurrent Prolog is developed and related to an operational semantics. The denotational semantics makes divergence and the resultant substitutions of finite computations together with the termination mode--success, failure, or deadlock--observable. Relative to this notion of observation it is proved that the denotational semantics is fully abstract in the sense that it records the minimal amount of extra information beyond the observables to make it compositional. Full abstraction is an important property because it quantifies the information that one needs in order to reason about individual program-parts independently. This is believed to be the first such result in the area of concurrent logic programming.