A Model of Planning for Plan Efficiency: Taking Advantage of Operator Overlap

Abstract

Many realistic planning problems (such as those in m~ufacturing) place a hi~ premium on plan effic1ency. However, class1cal planning theory does. not offer much insight into ways of obtaining effic1ent plans. The objective of this paper is to present a model of planning for plan efficiency that has been drawn from a case study in the machining domain. Some of the important features of this domain are that problems are stated as sets of conjunctive goals, and operators that achieve those goals have a high degree of overlap. Operators can be said to overlap when they can share work. Because of this overlap, the cost of the operators is dependent on their order in the plan, (for example, it is less time consuming to buy vegetables if your last action was also done at the grocery store) However, looking for a near optimal set of overlapping operators can lead a very expensive search. The methods that human machinists were found to be using reduced the co~plexity of the searc~ for good operators by usmg cues and patterns m the problem specification, gained from experience, to tell them when it might be useful to explore an operator.