The original formulation of SharedPlans (Grosz and Sidner, 1990a) was developed to provide a model of collaborative planning in which it was not necessary for one agent to have intentions-to toward an act of a different agent. Unlike other contemporaneous approaches (Searle, 1990), this formulation provided for two agents to coordinate their activities without introducing any notion of irreducible joint intentions. However, it only treated activities that directly decomposed into single-agent actions, did not address the need for agents to commit to their joint activity, and did not adequately deal with agents having only partial knowledge of the way in which to perform an action. This paper provides a revised and expanded version of SharedPlans that addresses these shortcomings. It also reformulates Pollack's definition of individual plans (Pollack, 1990) to handle cases in which a single agent has only partial knowledge; this reformulation meshes with the definition of Shar...

An agent's ability to understand an utterance depends upon its ability to relate that utterance to the preceding discourse. The agent must determine whether the utterance begins a new segment of the discourse, completes the current segment, or contributes to it. The intentional structure of the discourse, comprised of discourse segment purposes and their interrelationships, plays a central role in this process (Grosz and Sidner, 1986). In this thesis, we provide a computational model for recognizing intentional structure and utilizing it in discourse processing. The model specifies how an agent's beliefs about the intentions underlying a discourse affects and are affected by its subsequent discourse. We characterize this process for both interpretation and generation and then provide specific algorithms for modeling the interpretation process. The collaborative planning framework of SharedPlans (Lochbaum, Grosz, and Sidner, 1990; Grosz and Kraus, 1993) provides the basis for our model ...

The notion that a text is coherent in virtue of the `relations' that hold between its component spans currently forms the basis for an active research programme in discourse linguistics. Coherence relations feature prominently in many theories of discourse structure, and have recently been used with considerable success in text generation systems. However, while the concept of coherence relations is now common currency for discourse theorists, there remains much confusion about them, and no standard set of relations has yet emerged. The aim of this thesis is to contribute towards the development of a standard set of relations. We begin from an explicitly empirical conception of relations: they are taken to model a collection of psychological mechanisms operative during the tasks of reading and writing. This conception is fleshed out with reference to psychological theories of skilled task performance, and to Rosch's notion of the basic level of categorisation. A methodology for investi...

The formalization of multi-agent autonomous systems requires a rich ontology for capturing a variety of collective behaviours and a powerful semantics for distinguishing between collective agents having, executing, and jointly intending a plan. In this paper, we introduce the notion of social agents and social plans. A definition of joint intentions is provided that avoids some of the problems encountered by previous formalizations. In particular, it models cooperation by requiring that agents adopt a joint goal and a joint plan of action before forming a joint intention. The paper also stresses the planning capability of agents and outlines a process for means-end reasoning by multiple agents. 1 Introduction Situated agents are systems embedded in dynamic environments; they continuously sense their environment and effect changes to it by performing actions. These agents have to balance the time they devote to thinking against the time they take acting. Also they need to balance the...

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This paper presents an analysis of purpose clauses in the context of instruction understanding. Such analysis shows that goals affect the interpretation and / or execution of actions, lends support to the proposal of using generation and enablement to model relations between actions, and sheds light on some inference processes necessary to interpret purpose clauses.

Certain spans of utterances in a discourse, referred to here as segments, are widely assumed'to form coherent units. Further, the segmental structure of discourse has been claimed to constrain and be constrained by many phenomena. However, there is weak consensus on the nature of segments and the criteria for recognizing or generating them. We present quantitative results of a two part study using a corpus of spontaneous, narrative monologues. The first part evaluates the statistical reliability of human segmentation of our corpus, where speaker intention is the segmentation criterion. We then use the subjects' segmentations to evaluate the corre- lation of discourse segmentation with three linguistic cues (referential noun phrases, cue words, and pauses), using information retrieval metrics.

In modeling the structure of task-related discourse using plans, it is important to distinguish between plans that the agent has adopted and is pursuing and those that are only being considered and explored, since the kinds of utterances arising from a particular domain plan and the patterns of reference to domain plans and movement within the plan tree are quite different in the two cases. This paper presents a three-level discourse model that uses separate domain and exploration layers, in addition to a layer of discourse metaplans, allowing these distinct behavior patterns and the plan adoption and reconsideration moves they imply to be recognized and modeled.

Agents collaborating to achieve a goal bring to their joint activity different beliefs about ways in which to achieve the goal and the actions necessary for doing so. Thus, a model of collaboration must provide a way of representing and distinguishing among agents' beliefs and of stating the ways in which the intentions of different agents contribute to achieving their goal. Furthermore, in collaborative activity, collaboration occurs in the planning process itself. Thus, rather than modelling plan recognition, per se, what must be modelled is the augmentation of beliefs about the actions of multiple agents and their intentions. In this paper, we modify and expand the SharedPlan model of collaborative behavior (Grosz and Sidner, 1990) . We present an algorithm for updating an agent's beliefs about a partial SharedPlan and describe an initial implementation of this algorithm in the domain of network management. Introduction Agents collaborating to achieve a goal bring to their joint ...

Natural language interfaces require dialogue models that allow for robust habitable and efficient interaction. This paper presents such a model for dialogue management for natural language interfaces. The model is based on empirical studies of human computer interaction in various simple service applications. It is shown that for applications belonging to this class the dialogue can be handled using fairly simple means. The interaction can be modeled in a dialogue grammar with information on the functional role of an utterance as conveyed in the linguistic structure. Focusing is handled using dialogue objects recorded in a dialogue tree representing the constituents of the dialogue. The dialogue objects in the dialogue tree can be accessed by the various modules for interpretation generation and background system access. Focused entities are modeled in entities pertaining to objects or sets of objects and related domain concept information; properties of the domain objects. A simple copying principle where a new dialogue object's focal parameters are instantiated with information from the preceding dialogue object accounts for most context dependent utterances. The action to be carried out by the interface is determined on the basis of how the objects and related properties are specified. This in turn depends on information presented in the user utterance context information from the dialogue tree and information in the domain model. The use of dialogue objects facilitates customization to the sublanguage utilized in a specific application. The framework has successfully been applied to various background systems and interaction modalities. In the paper results are presented from the customization of the dialogue manager to three typed interaction applications are prese...