This paper summarizes the main existing approaches to propagate resource constraints in Constraint-Based scheduling and identifies some of their limitations for using them in an integrated planning and scheduling framework. We then describe two new algorithms to propagate resource constraints on discrete resources and reservoirs. Unlike most of the classical work in scheduling, our algorithms focus on the precedence relations between activities rather than on their absolute position in time. They are efficient even when the set of activities is not completely defined and when the time window of activities is large. These features explain why our algorithms are particularly suited for integrated planning and scheduling approaches. All our algorithms are illustrated with examples. Encouraging preliminary results are reported on pure scheduling problems.

Planning has belonged to fundamental areas of AI since its beginning and sessions on planning are an integral part of major AI conferences. By generating activities necessary to achieve some goal, planning is also closely related to scheduling that deals with allocation of activities to scarce resources. Although the planning and scheduling communities are somehow separated, both areas have interacted more and more in recent years, especially when dealing with real-life problems. This FLAIRS special track attempts to make the conference attractive for the planning community, a traditional part of the AI family, and also the scheduling community -- especially for those using AImotivated solving techniques such as constraint satisfaction. FLAIRS 2008 hosted the first special track on AI planning and scheduling.