Ramification and causality in a modal action logic

The paper presents a logic for action theory based on a modal language, where modalities represent actions. The frame problem is tackled by using a nonmonotonic formalism which maximizes persistency assumptions. The problem of ramification is tackled by introducing a modal causality operator which is used to represent causal rules. Assumptions on the value of fluents in the initial state allow reasoning with incomplete initial states and postdiction. The action theory can also deal with nonminimal change and nondeterministic actions.