Abstract
We describe an approach to computing upper bounds on the lengths of solutions to reachability problems in transition systems. It is based on a decomposition of state-variable dependency graphs (causal graphs). Our approach is able to find practical upper bounds in a number of planning benchmarks. Computing the bounds is computationally cheap in practice, and in a number of benchmarks our algorithm runs in polynomial time in the number of actions and propositional variables that characterize the problem.