Goal Transformations in Continuous Planning

Continuous planning refers to the process of planning in a world under continual change. Traditionally, as new world information is encountered, a planner adapts to it through the refinement of the plans that are under construction. The major thesis of this paper, however, is that often it is necessary to modify the goals of the planner in addition to the plans themselves. We introduce the concept of goal transformations in a continuous planner. The extended planner can automatically select the appropriate goal transformations in response to world changes and can completely solve the transformed problem. We present a set of goal transformations that handle, in particular, changes in resources in the world. We introduce a detailed taxonomy of goal transformations. We implemented several transformations within a planning system, and we show empirical results that demonstrate the effectiveness of our approach.