inverse problem of plan recognition has focused on specific kinds of recognition in specific domains. This includes work on story understanding [Bruce 1981, Schank 1975, Wilensky

This chapter surveys the field of user modeling in artificial intelligence dialog systems. First, reasons why user modeling has become so important in the last few years are pointed out, and definitions are proposed for the terms 'user model ' and 'user modeling component'. Research within and outside of artificial intelligence which is related to user modeling in dialog systems is discussed. In Section 2, techniques for constructing user models in the course of a dialog are presented and, in Section 3, recent proposals for representing a wide range of assumptions about a user's beliefs and goals in a system's knowledge base are surveyed. Examples for the application of user models in systems developed to date are then given, and some social implications discussed. Finally, unsolved problems like coping with collective beliefs or resource-limited processes are investigated, and prospects for applicationoriented research are outlined. Although the survey is restricted to user models in naturallanguage dialog systems, most of the concepts and methods discussed can be extended to AI dialog systems in general.

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Journal of Experimental and Theoretical Artificial Intelligence (JETAI) 9, 1997, 215-235. Special issue on Architectures for Physical Agents. Mobile robots, if they areto perform useful tasks andbecome accepted in open environments, must be fully autonomous. Autonomy has many different aspects; here we concentrate on three central ones: the ability to attend to another agent, to take advice about the environment, and to carry out assigned tasks. All three involve complex sensing and planning operations on the part of the robot, including the use of visual tracking of humans, coordination of motor controls, and planning. We show how these capabilities are integrated in the Saphira architecture, using the concepts of coordination of behavior, coherence of modeling, and communication with other agents. This paper reports work done while this author was at SRI International. 1 Autonomous Mobile Agents What are the minimal capabilities for an autonomous mobile agent? Posed in this way,...

This paper describes a novel approach to high-level robot programming based on a highly developed logical theory of action. The user provides a specification of the robot's basic actions (their preconditions and effects on the environment) as well as of relevant aspects of the environment, in an extended version of the situation calculus. He can then specify robot behaviors in terms of these actions in a programming language that allows references to world conditions (e.g. if 9c(Pop can(c) On table(c)) then pick up(c)). The programs can be executed to drive the robot. The interpreter automatically maintains the world model required to execute programs based on the specification. The theoretical framework includes a solution to the frame problem and is very general --- it handles dynamic and incompletely known worlds, as well as perception actions. Given this kind of domain specification, it is also possible to support more sophisticated reasoning, such as task planni...

This paper proposes a solution to the frame problem for knowledgeproducing actions. An example of a knowledge-producing action is a sense operation performed by a robot to determine whether or not there is an object of a particular shape within its grasp. The work is an extension of Reiter's solution to the frame problem for ordinary actions and Moore's work on knowledge and action.

In presence of incomplete information about the world we need to distinguish between the state of the world and the state of the agent’s knowledge about the world. In such a case the agent may need to have at its disposal sensing actions that change its state of knowledge about the world and may need to construct more general plans consisting of sensing actions and conditional statements to achieve its goal. In this paper we first develop a high-level action description language that allows specification of sensing actions and their effects in its domain description and allows queries with conditional plans. We give provably correct translations of domain description in our language to axioms in first-order logic, and relate our formulation to several earlier formulations in the literature. We then analyze the state space of our formulation and develop several sound approximations that have much smaller state spaces. Finally we define regression of knowledge formulas over conditional plans,

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Several formalizations of cognitive state that include intentions and beliefs based on normal modal logics (NMLs) have appeared in the recent literature. We argue that NMLs are not an appropriate representation for intention, and provide an alternative model, one that is representationalist, in the sense that its semantic objects provide a more direct representation of cognitive state of the intending agent. We argue that this approach results in a much simpler model of intention than does the use of an NML, and that, moreover, it allows us to capture interesting properties of intention that have not been addressed in previous work. 1 Introduction Formalizations of cognitive state that include intentions and beliefs have appeared in the recent literature (Cohen and Levesque 1990a, Rao and Georgeff 1991, Shoham 1990, Konolige and Pollack 1989) . With the exception of the current authors, these have all employed normal modal logics (NMLs), that is, logics in which the semantics of the...

THE aim of this thesis is to investigate logical formalisms for describing, reasoning about, specifying, and perhaps ultimately verifying the properties of systems composed of multiple intelligent computational agents. There are two obvious resources available for this task. The first is the (largely AI) tradition of reasoning about the intentional notions (belief, desire, etc.). The second is the (mainstream computer science) tradition of temporal logics for reasoning about reactive systems. Unfortunately, neither resource is ideally suited to the task: most intentional logics have little to say on the subject of agent architecture, and tend to assume that agents are perfect reasoners, whereas models of concurrent systems from mainstream computer science typically deal with the execution of individual program instructions. This thesis proposes a solution which draws upon both resources. It defines a model of agents and multi-agent systems, and then defines two execution models, which ...