We present a technique which allows partial-order causal-link (POCL) planning systems to use heuristics known from state-based planning to guide their search.

The technique encodes a given partially ordered partial plan as a new classical planning problem that yields the same set of solutions reachable from the given partial plan. As heuristic estimate of the given partial plan a state-based heuristic can be used estimating the goal distance of the initial state in the encoded problem. This technique also provides the first admissible heuristics for POCL planning, simply by using admissible heuristics from state-based planning. To show the potential of our technique, we conducted experiments where we compared two of the currently strongest heuristics from state-based planning with two of the currently best-informed heuristics from POCL planning.