!2th Workshop on Nonmonotonic Reasoning (NMR'08)Like any other logical theory, action theories in reasoning about actions may evolve, and thus need revision methods to adequately accommodate new information about the behavior of actions. Here we give a semantics that complies with minimal change for revising action theories stated in a version of PDL. We give algorithms that are proven correct w.r.t. the semantics for those theories that are modular
