Projection in Constraint Logic Programming
Projection is the elimination of dead variables in constraint systems, preserving equivalence. In CLP systems as well as in Prolog, local variables may become inaccessible during computation. Their removal can be considered as a form of garbage collection, it bears however another potential. It can support the solver, and it can reduce search spaces. This book investigates when it is wise to apply projection and proves its usefulness in tackling two practical planning problems.