Using and Re-Using Partial Plans

Abstract

Partial or default plans are responsible for much of the speed and flexibility of human problem solving. This paper describes a computer planning and execution monitoring system which attempts to use partial or default plans to achieve goals posed to it. The planner is sometimes thwarted and hampered by an inaccurate world model. If the default plan fails to achieve the given goal, the planner attempts to modify the default plan with a local analysis leading to local changes to the failed plan. The modified plan is then delivered to the execution monitor for another execution attempt. Occasionally, a strategy based solely on local considerations is insufficient to result in successful plan modification and execution. In those situations, global analysis frequently reveals that some information can be ignored during plan execution.