Embracing Occlusion in Specifying the Indirect Effects of Actions

In this paper we extend PMON a logic for reasoning about action and change with causal rules which are used to specify the indirect e ects of actions The extension called PMON RCs has the advantage of us ing explicit time includes actions with dura tions nondeterministic actions allows par tial speci cation of the timing and order of actions and has been assessed correct for at least the K IA class of action scenarios with in the Features and Fluents framework Most importantly the circumscription policy used is easily shown to be reducible to the rst order case which insures that standard the orem proving techniques and their optimiza tions may be used to compute entailment In addition we show how the occlusion concept previously used to deal with duration and nondeterministic actions proves to be equal ly versatile in representing causal constraints and delayed e ects of actions We also dis cuss related work and consider the strong correspondence between our work and recent work by Lin who uses a Cause predicate to specify indirect e ects similar to our use of Occlude in PMON and a minimization poli cy related to that used in PMON