Selectively delaying linking commitments in partial-order planners
R. S. de Silva · 1996
. Total-order planners perform backtracking search over all possible total-orderings, but their commitment to a total order gives them a well-defined current state that can be used to guide the search at later choice-points. Partial-order planners handle operator-orderings more efficiently, but lack a current state. In such planners, an open condition can be linked to many steps (both pre-existing and newly introduced) , and making a causal link to one is a choice-point. Veloso & Blythe (1994) showed how the lack of a current state to give guidance at these choice-points causes linkability difficulties. This paper explores how partial-order planners can maintain an approximation of the current state, and use it to give guidance at linkability choice-points. An inexpensive domain-independent heuristic selectively delays linking commitments in a manner very similar to that in which a total-order planner handles goals that are already satisfied in the current state. The heuristic, impleme...