version of that system, show how quantifiers can be included in it, and study its relation to circumscription and default logic, to logic programming, and to the theory of epistemic queries developed by Hector Levesque and Ray Reiter. 1 Introduction Lin and Shoham [16] defined a propositional

are important when considering interactions of automated agents in complex dynamic environments, such as the semantic web. Here we revisit Hector Levesque’s original motivation of implicit knowledge and consider several contemporary realizations of implicit knowledge. We present a framework to compare different

We report on a sound and complete proof system, COOL, for the propositional fragment of Hector Levesque's nonmonotonic logic `The Logic of Only Knowing' [Lev90]. The proof system is devised using the framework of compiled labelled deductive systems [BrGaRu00], which enables a translation

the computational complexity of a logical formalism is an essential tool for characterizing the properties of the formalism itself, at that time this kind of investigation was not so common. Only recently, people like Hector Levesque, Ron Brach-man, Ray Reiter and others had started pointing out the importance

keynote speech given at COSIT 2011. Thanks to Max Egenhofer and Reinhard Moratz for the invitation to speak at COSIT; and to Antony Galton, Hector Levesque, and James Pustejovsky for helpful suggestions. 1 Lauder’s definition of “aorta ” is, “the personification of the benevolently paternal welfare State

, the representation of agent’s intentions varies greatly between theories. Some logics characterize intention as a primitive operator, while others define intention in terms of more primitive con-structs. Taking the latter approach is a theory due to Philip Cohen and Hector Levesque, under which intentions are a

for such a theory. We emphasize the role of model expansion for first order logic, with extensions, in specifying NP search problems, and describe the formalization of arithmetic in this context. This paper is dedicated to Hector J. Levesque.