Exploiting local flexibility during execution of pre-computed schedules

In this paper we address the problem of realizing the benefits of pre-computed schedules in the face of a partially unpredictable execution environment. We focus specifically on the problem of manufacturing production scheduling, where advance planning is crucial to overall factory performance but is, at the same time, confounded by the unpredictability of factory operations. We present a scheduling framework where decision-making responsibility is shared between a global scheduler, responsible for establishing and maintaining execution constraints in accordance with overall performance objectives, and a local dispatcher, responsible for containing execution within globally imposed constraints and notifying the scheduler when containment is no longer possible. We identify the sources of local executional flexibility that can be expected in a pre-computed schedule, and describe an execution-time scheduler (the dispatcher) capable of exploiting this flexibility.