Simulation and Constraint Programming as Support Methodologies for Job Shop Scheduling

ABSTRACT In this paper we introduce a modelling, simulation and scheduling system for discrete production processes. It contains a model builder, a simulator and an evaluator manipulator. The model builder allows to create hierarchical models of discrete production processes. The hierarchical organisation of the models allows the user to focus his attention on relevant parts of the production process and to organise data (e.g. performance data). The simulator and the evaluator manipulator enable the user to explore the space of possible schedules for a given problem. The evaluator manipulator—written as a constraint propagation program—enables the system to visualise the effects of the decisions taken by the user during the scheduling process. The simulator can also be used to test the robustness of schedules with respect to machine breakdowns. The production model insulates the user from the technicalities of specifying constraints and events. Finally, we describe the use of a genetic algorithm to discov...