The Need for Di erent Domain-Independent Heuristics

prodigy's planning algorithm uses domain-independent search heuristics. In this paper, we support our belief that there is no single search heuristic that performs more e ciently than others for all problems or in all domains. The paper presents three di erent domain-independent search heuristics of increasing complexity. We run prodigy with these heuristics in a series of arti cial domains (introduced in (Barrett & Weld 1994)) where in fact one of the heuristics performs more e ciently than the others. However, we introduce an additional simple domain where the apparently worst heuristic outperforms the other two. The results we obtained in our empirical experiments lead to the main conclusion of this paper: planning algorithms need to use di erent search heuristics in di erent domains. We conclude the paper by advocating the need to learn the correspondence between particular domain characteristics and speci c search heuristics for planning e ciently in complex domains.