The And-compositionality of CLP Computed Answer Constraints.
Roberto Bagnara, Marco Comini, Francesca Scozzari, Enea Zaffanella · 1996
We present a semantic characterization of CLP languages for the class of quick-checking systems. We define a semantics of computed answer constraints which is AND-compositional, does not loose the distinction between active and passive constraints in the answers and has both a top-down and a bottom-up characterization. We also show that an incrementality property we impose on the constraint solver is essential in order to define an AND-compositional atombased semantics. 1 Introduction The semantics of CLP languages presented in [6] is (at least in its intentions) very general. Real CLP systems, in fact, are often equipped with incomplete constraint solvers and delay mechanisms. For instance, the arithmetic solver employed in the CLP(R) system [7] deals only with linear constraints, whereas non-linear ones are delayed. The languages truly implemented by these "real systems" are not captured by standard semantics constructions such as the original one of [5] and its refinements [4]. T...