The replacement operation for CLP modules

In this paper we study the replacement transformation for Constraint Logic Programming modules. We define new applicabihty conditions which guarantee the correctness of the operation also wrt module¿s composition: under this conditions, the original and the transformed modules have the same observable properties also when they are composed with other modules. Furthermore, the applicability y conditions are uot bound to a specific notion of observable. Here we consider three distinct such notions: two of them are operational and are based on the computed constraints; the third one is the algebraic one based on the least model. We show that our transformation method can be applied in any of these distinct contexts, thus providing a parametric approach.