Parameterized Horn Clause Specifications: Proof Theory and Correctness

Recently, "algebraic" equational Horn clause specifications (or, in some sense, conditional specifications) have been advocated by several authors as the solution to some of the problems of Prolog [see, for instance, 11]. Most of the work done in this field has been dealing only with the operational aspects of such specifications (e.g. rewriting, narrowing, etc.), perhaps assuming that other kind of results will be direct generalizations of those obtained for the equational case.