Component Programming and Interoperability in Constraint Solver Design

Prolog was once the main host for implementing constraint solvers. It seems that it is no longer so. To be useful, constraint solvers have to be integrable into industrial applications written in imperative or object-oriented languages; to be efficient, they have to interact with other solvers. To meet these requirements, many solvers are now implemented in the form of extensible object-oriented libraries. Following Pfister and Szyperski, we argue that ``objects are not enough,'' and we propose to design solvers as component-oriented libraries. We illustrate our approach by the description of the architecture of a prototype, and we assess its strong points and weaknesses.