Symbolic Planning for Strong-Cyclic Policies

A solution for Fully Observable Non-Deterministic FOND planning is classified as weak, strong or strong-cyclic, indicating different ways to reach a goal state due to the non-determinism of the actions. In this paper, we propose a new algorithm to solve FOND planning problems for strong-cyclic policies, where the agent always achieves the goal, under the fairness assumption that execution will eventually exit from all existing cycles. The planner, called Pactl-Sym-StrongCyclic, is based on symbolic model checking using alpha-CTL logic: an extension of CTL that considers actions behind the transitions. To the best of our knowledge, this is the first FOND planner for strong-cyclic policies that applies symbolic reasoning over the actions (and not over the state transition relation), and therefore can outperform state-of-the-art FOND planners.