UsingSchedules for Operational Guidance

The broad goal o, production scheduling is to produce a factory behavior where products are produced in a timely and cast-effective manner. In complex environments, advance development of. a schedule appeélrs fundamental to this goal, as it is only through anticipation 01resource contention (the prim~ry obstacle to efficient lactory behavior) that the deleterious effects of these conflicts can be minimized. However, the extent to which the behavior impliedby a generated schedule is actually realized depends on the manner in which the schedule is "executed " on the factory floor. The unpredictability of factory operations (e.g. machine breakdowns, quality control failures) will inevitably lorce deviations from prescribed behavior, and an advance schedule will be of little use unless the guidance it contains is continually adapted to the specifics of the current factorystate. Research in production scheduling [2] has trac:titionallyignored problems of schedule execution, evaluating its results as if the world were entirely predictable and generated sch~dules could be executed exactly as planned. On the other hand, research relevant to factory floor oontrol"[6]has emphasized the development of local dispatch heuristics for dynamic decision-making, and conceded any potential benefits 01advance scheduling (withthe exception of establishing release and due dates). In this talk we consider the scheduling problem from the operational perspective of providingglobal guidance to the. actual decisions that must be made on th