Beyond the Glass Box: Constraints as Objects.

This work proposed to give access to the constraints as first class citizen of the CLP language, and implemented this approach into an object oriented language, where constraints are explicitly represented by objects.

Abstract

Constraint Logic Programming (CLP) is a very active research area. One reason being that finite domain CLP systems have been successfully applied to various combinatorial optimization problems such as time tabling, scheduling, frequency allocation, manpower planning, production planning. State of the art finite domain CLP languages offer programming constructs that gives access to the state of the constraint solver. With these constructs, new constraints can be defined in the CLP language directly, hence the name "glass-box". However, current glass box approaches do not give access to the constraints themselves. This prevents the use of sophisticated constraint solving techniques borrowed from Operations Research. In order to overcome this limitation, we propose to give acces to the constraints as first class citizen of the CLP language. We implemented this approach into an object oriented language, where constraints are explicitly represented by objects. We provide both theoretical and experimental evidence of the interest of our approach. In particular, we show that some of our extensions provide speedups of more than one order of magnitude over current glass box constraint solvers.