Regression Planning

There are two strands of research into automated planning: the study of nonlinear, progressive, heuristic planners, and the study of linear, regressive, rigorous planners. We focus on the latter, in particular the formulation of E. Pednault. Regression planning can be viewed as a nondeterministic algorithm in which a goal is reduced by preserving it from the initial situation, by insertion of a step to accomplish it, or by adaptation of an existing step. This algorithm can be proven complete, in the sense that it finds any straight-line plan with no redundant steps. An extension of the algorithm to make use of "formal objects" is also complete. A practical implementation of the algorithm can solve several nontrivial problems. A powerful predicate-calculus simplifier is an important component. It is still unclear whether these elegant results make contact with practicality.