Probabilistic Reasoning about Actions in Nonmonotonic Causal Theories

We present the language PC+ for probabilistic reasoning about actions, which is a generaliza­ tion of the action language C + that allows to deal with probabilistic as well as nondeterministic ef­ fects of actions. We define a formal semantics of PC+ in terms of probabilistic transitions be­ tween sets of states. Using a concept of a history and its belief state, we then show how several im­ portant problems in reasoning about actions can be concisely formulated in our formalism.