Symmetry-based task reduction for relaxed reachability analysis

Relaxed reachability analysis is relevant to efficient grounding, invariant synthesis as well as the computation of relaxation-based heuristics. Planning domains are typically specified in a lifted representation, where the size of the tasks grows exponentially with the number of objects in the world. This growth also affects the analysis of relaxed reachability. We present a task reduction based on symmetries of the lifted representation that allows to perform the same analysis on smaller tasks.