Flexible reuse of plans via annotation and verification.

An approach is presented for flexible reuse of old plans in the presence of a generative planner. In this approach, the planner leaves information relevant to the reuse process in the form of annotations on every generated plan. To reuse an old plan in solving a new problem, the plan along with its annotations is mapped into the problem. A process of annotation verification is used to locate applicability failures and suggest refitting tasks. The planner is then called upon to carry out the suggested modifications, i.e., to produce an executable plan for the new problem. This integrated approach obviates the need for any extra domain knowledge (other than that already known to the planner) during reuse and thus affords a relatively domain independent framework for plan reuse. Details are presented of annotation and plan reuse in PRIAR, a plan-reuse system based on this approach. The authors believe that their approach can be profitably used by generative planners in many application domains.