A Method for Dealing with Potentially Relaxable Constraints and Its Application to a Dispatcher Scheduling System

We present a novel method for dynamically deciding when, how, and to what extent soft constraints should be relaxed. The rst part of the method is a depth-rst search and best-rst repair algorithm, and the second part of the method is an algorithm for gradually relaxing soft constraints. The method can guarantee that (1) a soft constraint will be relaxed only when no backtrack (repair) can be made within a time limit, (2) the relaxation of soft constraints can always deepen the search tree, and (3) the relaxation will only be made at dead nodes, and when the search algorithm can be continued the relaxed soft constraints will return to their initial states. The method has been successfully applied to a dispatcher scheduling system. We also brieey introduce that system.