ON THE RELATION BETWEEN SITUATION CALCULUS AND EVENT CALCULUS

In this paper we make a detailed comparison of the Situation Calculus and the Event Calculus, two logic-based temporal reasoning formalisms. We concentrate on differences between the calculi, considering the si milarities sufficiently indicated in the recent literature. We illustr ate the inability of Event Calculus to handle counterfactual reasoning problems, and that of Situation Calculus to deal with counterfactual statements in the presence of actions with nondeterministic effects. W e present a new calculus which extends both Situation and Event Calcul us. In this new calculus we define a natural and clear relation betwee n situations and time points, which differs from those used in previou s comparisons. We show the relation of this new calculus to both origi nal calculi. We compare the original calculi using the new calculus as an analysis tool. (C) Elsevier Science Inc., 1997.