Avoiding scheduling errors by partial simulation of the future

Scheduling based on partial simulation is described. The proposed solution is of a predictor-corrector type. The essential idea is not to start with the uncontrolled system with all its flexibility in the sequencing of the operations but with a controlled system. The basic control algorithm is a priority rule. Then, the potential errors are considered. This means one starts on the bottleneck machines and simulates the situation on the stations which the jobs which are presently waiting will encounter. This requires simulating all other stations from which potentially competing jobs may originate. Still, only a small part of the system is considered. This analysis yields the probable earliest possible starting times for the next processing steps and hence the real due dates for the operations waiting in front of the bottleneck station. Scheduling on this station is then done based on these due dates rather than based on the global slack of the job or on the operation due date determined in advance. The result of the partial simulation is a dynamical operation due date for each operation in the queue considered