Supporting Flexible Plan Reuse

Publisher Summary This chapter discusses a framework called PRIAR that effectively supports retrieval and modification of plans for reuse. PRIAR enables a hierarchical nonlinear planner to improve its planning by reusing previously generated plans. PRIAR uses the causal structures of plans to judge the appropriateness of reusing them in new problem situations and to modify them minimally to make them solve new problems. PRIAR provides an integrated framework for supporting reuse within hierarchical nonlinear planning. Hierarchical nonlinear planning is a dominant method of abstraction and least commitment in domain-independent planning. In this approach, plans are represented as partially ordered network of tasks at various levels of abstraction. PRIAR facilitates the modification of a hierarchical plan by justifying the individual decisions underlying its development in terms of its causal dependency structure. PRIAR also provides a domain-independent similarity metric based on the plan validation structure to measure the utility of modifying a given plan to solve a new problem. The key insight used in developing the similarity metric is that the modification cost depends on the number and types of inconsistencies that are caused by the specifications changes in the plan validation structure.