Making Forward Chaining Relevant

Planning by forward chaining through the world space has long been dismissed as being “obviously” infeasible. Nevertheless, this approach to planning has many advantages. Most importantly forward chaining planners maintain complete descriptions of the intermediate states that arise during the course of the plan’s execution. These states can be utilized to provide highly effective search control. Another advantage is that such planners can support richer planning representations that can model, e.g., resources and resource consumption. Forward chaining planners are still plagued however by their traditional weaknesses: a lack of goal direction, and the fact that they search totally ordered action sequences. In this paper we address the issue of goal direction. We present two algorithms that provide a forward chaining planner with more information about the goal, and allow it to avoid certain types of irrelevant state information and actions.