Achieving Several Goals Simultaneously
by Waldinger, Richard
Technical Note 107
Institution: AI Center, SRI International
Address: 333 Ravenswood Ave., Menlo Park, CA 94025
In the synthesis of a plan or computer program, the problem of achieving several goals simultaneously presents special difficulties, since a plan to achieve one goal may interfere with attaining the others. This paper develops the following strategy: to achieve two goals simultaneously, develop a plan to achieve one of them and then modify that plan to achieve the second as well. A systematic program modification technique is presented to support this strategy. The technique requires the introduction of a special ``skeleton model’’ to represent a changing world that can accommodate modifications in the plan. This skeleton model also provides a novel approach to the ``frame problem.’’ The strategy is illustrated by its application to three examples. Two examples involve synthesizing the following programs: interchanging the values of two variables and sorting three variables. The third entails formulating a tricky blocks world plan. The strategy has been implemented in a simple QLISP program. It is argued that skeleton modeling is valuable as a planning technique apart from its use in plan modification, particularly because it facilitates the representation of ``influential actions’’ whose effects may be far reaching. The second part of the paper is a critical survey of contemporary planning literature, which compares our approach with other techniques for facing the same problems.
|Waldinger, Richard J||Principal Scientist|