Reactive constraint-based scheduling

The authors of the paper are currently concerned with the design of a knowledge-based scheduling system at the operational level of VLSI wafer fabrication. This is a particular difficult job-shop scheduling problem for two reasons. Firstly, it is difficult to define the criteria by which a schedule can be considered optimal, due to conflicting and changing objectives. Secondly, the wafer fabrication environment is highly dynamic, as unexpected events (such as machine breakdowns and new job arrivals) occur at frequent intervals. The paper describes an approach to solving both of these problems, it establishes a framework for realizing this approach and it describes the implementation of a prototype system within this framework. Most of the examples discussed are from the domain of wafer fabrication, but the basic ideas should be applicable to any job-shop scheduling domain