Reasoning on Constraints in Constraint Logic Programming

Constraint Logic Programming solvers on finite domains use constraints to prune those combinations of assignments which cannot appear in any consistent solution. There are applications, such as temporal reasoning or scheduling, requiring some form of qualitative reasoning where constraints can be changed (restricted) during the computation or even chosen when disjunction occurs. We embed in a CLP(FD) solver the concept of constraints as first class objects. In the extended language, variables range on finite domains of integers and relation variables range on finite domains of relation symbols. We define operations and constraints on the two sorts and one constraint linking the two. Programming examples are given, showing the advantages and the expressive power of the extension proposed