Constraint Propagation and the DSP

Abstract

In section 2.2, constraint propagation has been introduced as an elementary method of search space reduction for the CSP or the COP. In this chapter, we examine how constraint propagation techniques can be adapted to the DSP. An important issue is the computational complexity of the techniques applied which has to be weighed against the search space reduction obtained. Recall that establishing n-, n-d- and n-b-consistency for instances of the CSP or the COP are NP-hard problems. It is not difficult to show that the same complexity result applies if we confine ourselves to the more special DSP. Thus, if constraint propagation is to be of any use in solving the DSP, we will have to content ourselves with approximations of the consistency levels mentioned above.