Goal Interactions and Plan Quality*

Goals rarely occur in isolation. Efficient plan-ning for conjunctive goals is therefore of central interest. We identify a particular class of con-junctive goal interactions, which cannot be di-rectly inferred from the domain knowledge, as they are not explicitly represented in the precon-ditions and effects of the domain operators. We call such goal interactions, quality goal interac-tions, for they relate to issues on plan quality rather than to the common plan achievement is-sues. We illustrate the discussion with examples and briefly present the method we are develop-ing for acquiring control knowledge to direct the planner to consider the quality-goal interactions. 1 What Are Goal Interactions Planning goals rarely occur in isolation. A planner must be capable of taking into account the interactions between con-junctive goals in order to produce a plan to solve the prob-lem. There have been many research efforts addressing the issue of planning for conjunctive goals, focusing on a va-riety of aspects, including analyzing the complexity of this planning problem [Sussman, 1975, Chapman, 1987], de-signing appropriate planning algorithms [Sacerdoti, 1977