Using Causal-Link Graphs to Detect Conflicts Among Goals

Because of some "inherent" limitations, such as specifications of initial state or structures of domain actions, some goals can\´t be arrived together, which we call a planning task with goal conflicts. This planning task can hardly be resolved until goal conflicts are eliminated. And in such cases, people often need to know which goal conflicts a planning task contains and choose a new set of goals. In this paper, we present a technique for automatically detecting conflicts among goals by construction of a causal-link graph that captures the interactions between actions relevant to a given goal. By statically analyzing "competitive" preconditions of actions in a causal-link graph, we may inference which goals can\´t be reached together, without trying all best to resolve such an irresolvable planning task. Our method is sound and scaleable, but not complete; however, it may provide important information when people think about how to reconstruct an appropriate goal set.