9 1996 Kluwer Academic Publishers. Printed in the Netherlands. Reasoning about Action and Change A Dynamic Logic Approach

Abstract. Reasoning about change is a central issue in research on human and robot planning. We study an approach to reasoning about action and change in a dynamic logic setting and provide a solution to problems which are related to the frame problem. Unlike most work on the flame problem the logic described in this paper is monotonic. It (implicitly) allows for the occurrence of actions of multiple agents by introducing non-stationary notions of waiting and test. The need to state a large number of "frame axioms " is alleviated by introducing a concept of chronological preservation to dynamic logic. As a side effect, this concept permits the encoding of temporal properties ina natural way. We compare the relative merits of our approach and non-monotonic approaches as regards different aspects of the frame problem. Technically, we show that he resulting extended systems of propositional dynamic logic preserve (weak) completeness, finite model property and decidability