Showing papers by "Hector J. Levesque published in 1998"

Foundations for the Situation Calculus.

Abstract: The publishers will keep this article on-line on the Internet (or its possible replacement network in the future) for a period of 25 years from the date of publication, barring exceptional circumstances as described separately. The on-line availability of the article implies a permanent permission for anyone to read the article on-line, to print out single copies of it, and to use it unchanged for any non-commercial research and educational purpose, including making copies for classroom use. This permission can not be revoked by subsequent transfers of copyright. All other uses of the article are conditional on the consent of the copyright owner. The publication of the article on the date stated above included also the production of a limited number of copies on paper, which were archived in Swedish university libraries like all other written works published in Sweden. The publisher has taken technical and administrative measures to assure that the on-line version of the article will be permanently accessible using the URL stated above, unchanged, and permanently equal to the archived printed copies at least until the expiration of the publication period. For additional information about the Linkk oping University Electronic Press and its procedures for publication and for assurance of document integrity, please refer to its WWW home page: Abstract This article gives the logical foundations for the situations-as-histories variant of the situation calculus, focusing on the following items: The language of the situation calculus. Foundational axioms for the domain of situations. Axioms for an underlying domain theory. The syntax and semantics of the logic programminglanguage GOLOG. Axioms for knowledge and sensing actions. Essential metatheoretic results about the situation calculus.

A Completeness Result for Reasoning with Incomplete First-Order Knowledge Bases.

Abstract: 1 INTRODUCTION

Reasoning about Noisy Sensors and Effectors in the Situation Calculus

Abstract: Agents interacting with an incompletely known world need to be able to reason about the effects of their actions, and to gain further information about that world they need to use sensors of some sort. Unfortunately, both the effects of actions and the information returned from sensors are subject to error. To cope with such uncertainties, the agent can maintain probabilistic beliefs about the state of the world. With probabilistic beliefs the agent will be able to quantify the likelihood of the various outcomes of its actions and is better able to utilize the information gathered from its error-prone actions and sensors. In this paper, we present a model in which we can reason about an agent's probabilistic degrees of belief and the manner in which these beliefs change as various actions are executed. We build on a general logical theory of action developed by Reiter and others, formalized in the situation calculus. We propose a simple axiomatization that captures an agent's state of belief and the manner in which these beliefs change when actions are executed. Our model displays a number of intuitively reasonable properties.

AOL: A logic of Acting, Sensing, Knowing, and Only Knowing.

Abstract: This work is motivated by the existence of two useful but quite different knowledge representation formalisms, the situation calculus due to McCarthy, and the logic of only knowing due to Levesque. In this paper, we propose the logic , which combines both approaches in a clean and natural way. We present a semantics for which generalizes the semantics of to account for actions, and a sound and complete set of axioms for which generalizes the Lin and Reiter foundational axioms of the situation calculus to account for only knowing. The logic is compatible with earlier work on knowledge and action in that the solution to the frame problem for knowledge proposed by Scherl and Levesque becomes now a theorem of . We also demonstrate that the logic avoids certain anomalies present in related work by Lakemeyer. Finally we provide a mapping from into such that a sentence of is valid iff its mapping is a theorem of , thus providing, for the first time, a complete axiomatic characterization of .

Specifying communicative multi-agent systems

Abstract: , In this paper, we describe a framework for specifying communicative multi-agent systems, using a theory of action based on the situation calculus to describe the effects of actions on the world and on the mental states of agents; and the concurrent, logic programming language ConGolog to specify the actions performed by each agent. Since ConGolog has a well-defined semantics, the specifications can be used to reason about the behavior of individual agents and the system as a whole. We extend the work presented in [7] to allow the specifications to mention agents' goals explicitly. The framework presented here allows the behavior of different agents to be specified at different levels of abstraction, using a rich set of programming language constructs. As an example, we specify a meeting scheduler multi-agent system.