Constraint logic programming: Difference between revisions

Revision as of 16:27, 9 March 2006

Revision as of 18:03, 9 March 2006

Line 53:

==Labeling==

The labeling literals are used on variables over finite domains to check satisfiability or partial satisfiability of the constraint store and to find a satisfying assignment of variables on finite domains. A labeling literal is of the form <code>labeling([variables])</code>, where the argument is a list of variables over finite domains. Whenever the interpreter evaluates such a literal, it performs a search over the domains of variables to find an assignment that satisfies all relevant constraints. Typically, this is done by a form of [[backtracking]]: variables are evaluated in order, trying all possible values for each of them, and backtracking when inconsistency is detected.

The first use of the labeling literal is to actual check the satisfiability of the constraint store. Indeed, when the interpreter adds a constraint to the constraint store, it only checks or enforces a form of local consistency on it. This operation may not detect inconsistency even if the constraint store is unsatisfiable. A labeling literal over all variables of the constraint store enforces a complete satisfiability test to be performed.