A Unified View of Cost-Based Heuristics

Many cost-based planning heuristics are based on partial or complete delete relaxation. Definitions of these heuristics are of different nature, which makes it difficult to establish relations and formal comparisons among them. In this paper, we propose a unified definition with enough generality to cover most of existing heuristics. Important relations among heuristics can be derived from our study, as, for example, that some heuristics are equivalent to others under some conditions. Also, a side effect is that the generalized definition provides a framework to derive new heuristics for cost-based planning.