Towards a Process Semantics in the Logic Programming Style

We propose a new, more informative semantics for HCL: the meaning of a program is a set of observations over successful computations (refutations), which is parametric with respect to the observation function. The semantics is given in a logic programming style, i.e. with three different although equivalent characterizations (operational, model-theoretic and fixpoint). This semantics should fill the gap between the classic HCL semantics (not informative enough to be generalized to concurrent logic languages), and the process semantics used for imperative languages. Consistency of our approach with the classic semantics of HCL is checked by considering the minimal observation function, which observes just the initial and final state of a computation. Actually, the semantic definitions are given at the very basic level of transition systems, and it is shown how to represent a logic program with such a system. Therefore, the same constructions can be applied to every formalism representable as a transition system.