Reasoning about Action and Change: Defeasible Observations and Actions with Abnormal Effects

We provide a very general framework to reason about action and change. Our approach generalizes existing formalisms aimed at this type of inference in three respects. Firstly, we admit actions with abnormal effects, i.e. actions that may behave abnormally with respect to their intended specifications. Secondly, we admit defeasible observations, i.e. observations that are subject to invalidation. Thirdly, we admit arbitrary priorities between abnormalities, what allows us to prefer some actions and/or observations while resolving conflicts.