Transformation of optimal planning problems

Cost-optimal planning, in which the aim is to minimize the sum of costs of actions, is a challenging problem due to its computational complexity. A linear program derived from a relaxation which ignores the constraints on the ordering of actions can be used to obtain a lower bound on the cost of a solution-plan. We show that the dual of this linear program provides a transformation of the problem into an equivalent optimal planning problem in which the cost of the goal-achieving action is exactly equal to this lower bound. This transformation is of universal utility since it can be applied as a preprocessing technique and can thus be combined with any of the diverse techniques which have been developed for optimal planning.