Scheduling and rescheduling

As Smith (1995) has noted in most practical environments, scheduling is an ongoing reactive process where evolving and changing circumstances continually force reconsideration and revision of existing schedules. The aim of this paper is to introduce work from the TRUTH project on constraint based reasoning and reason maintenance systems and its use in addressing the dynamic nature of scheduling problems, in particular the problem of rescheduling. A fundamental problem has been that designers and implementers of scheduling systems to date have not taken reactivity as a central concern. The research reported here has been concerned with the reality of the planning and scheduling problem-particularly the fact that people managing schedules in real world contexts need help in responding effectively when change to a schedule is needed (the reactive rescheduling problem). This issue is based on a need for there to be, both in the user and within the system, a clear understanding of how the schedule has been put together and the interconnections between scheduling decisions within a typically complex scheduling environment.