Compiling Plan Operators from Domains Expressed in Qualitative Process Theory

John C. Hogge

The study of Qualitative Physics has concentrated on expressing qualitatively how the physical world behaves. Qualitative Physics systems accept partial descriptions of the world and output the possible changes that can occur. These systems currently assume that the world is left untouched by human or robot agents, limiting them to certain types of problem solving. For instance, a state-of-the-art qualitative physics system can diagnose faulty electrical circuits but can not construct plans to rewire circuits to change their behavior. This paper describes an approach to planning in physical domains and a working implementation which integrates Forbus’ Qualitative Process Engine (QPE) with a temporal interval-based planner. The approach involves compiling QPE expressions describing a physical domain into a set of operators and rules of the planner. The planner can then construct plans involving processes, existence of individuals, and changes in quantities. We describe how the compilation is performed, the types derivable plans, and current limitations in our approach.
