SUMMARY
Recent progress in manufacturing systems research has identified the feature of forbidding early shipment (FES) of orders as a prevalent characteristic of real systems. This report examines the implications of this feature on the choice of scheduling rules within a job shop. Simulation results of a simplified job shop reconfirm the superiority of the modified due date approach when the criterion is mean job tardiness. However, when the criterion is system inventory, the slack time per remaining operation ratio approach performs slightly better than modified due date. The shortest operation processing time yields very poor results in job shops that include the FES assumption.