Debugging constraint programs by store inspection

Expressiveness of constraint programming permits solving elegantly and efficiently many problems but makes difficult for the programmer to debug and understand the behaviour of his programs since most of the solving process (addition of new constraints and propagation of variables' domains modifications) is concealed by constraint solvers. However, tackling this problem by displaying a graphical representation of the original set of added constraints (store) is useless due to its huge size and its lack of structure whatsoever. W, e present in this chapter a means to organise hierarchically the store in order to divide it into manageable parts while preserving computation correctness; soundness of the method is shown, an algorithm supporting it is given, and an implemented prototype exhibiting its effectiveness is described.