A decision-making process for the real time control of a production unit

The scheduling of jobs on machines in a job-shop is considered using a multilevel decision-making structure. The levels are coordinated by considering as constraints on one level the decision made on the preceding level. For job-shop scheduling a tool is proposed to enable one to find and to analyse the set of feasible schedules in the light of the decision taken on the previous level. The information obtained as to the earliest starting and latest finishing times for performing the operations, as well as the logical sequence constraints acts as decision aids for the scheduling of the operations. The decision is made by choosing, from amongst the actions which are possible in the light of the overall objective, an action which takes into account secondary elements and considerations particular to the job-shop.