Situation calculus as hybrid logic: First steps

The situation calculus, originally conceived by John McCarthy, is one of the main representation languages in artificial intelligence. The original papers introducing the situation calculus also highlight the connection between the fields of artificial intelligence and philosophical logic (especially modal logics of belief, knowledge, and tense). Modal logic changed enormously since the 60s. This paper sets out to revive the connection between situation calculus and modal logic. In particular, we will show that quantified hybrid logic, QHL, is able to express situation calculus formulas often more natural and concise than the original formulations. The main contribution of this paper is a new quantified hybrid logic with temporal operators and action modalities, tailor-made for expressing the fluents of situation calculus.