We examine the problem of generating definite noun phrases that are appropri-ate referring expressions: that is, noun phrases that (a) successfully identify the intended referent to the hearer whilst (b) not conveying to him or her any false conversational implicatures (Grice, 1975). We review several possible computa-tional interpretotions of the conversational implicature maxims, with different computational costs, and argue that the simplest may be the best, because it seems to be closest to what human speakers do. We describe our recommended algorithm in detail, along with a specification of the resources a host system must provide in order to make use of the algorithm, and an implementation used in the natural language generation component of the IDAS system. 1.

... this paper, we argue that, to handle explanation dialogues successfully, a discourse model must include information about the intended effect of individual parts of the text on the hearer, as well as how the parts relate to one another rhetorically. We present a text planner that records this information and show how the resulting structure is used to respond appropriately to a follow-up question.

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 ...

This paper considers the semantics of the agent communication language KQML. By using this language for communication, agents will be able to request and provide services. Indeed, numerous projects have shown how the language can profitably support interoperation among distributed agents. However, before becoming a widely-accepted standard, it would be worthwhile to examine the language in detail, especially the semantical issues it raises. This paper identifies numerous difficulties with the language, and an attempt is made to point to their resolution. The paper illustrates the kind of semantics we believe to be necessary to characterize agent communication languages, identifies an important adequacy condition "compositionality" and shows how to compose a question from a request and an inform. Finally, the paper discusses possible impacts to be felt on various KQML decisions from the semantical issues raised here.

This paper summarizes work over the past five years on the automated planning and generation of multisentence texts using discourse structure relations, placing it in context of ongoing efforts by Computational Linguists and Linguists to understand the structure of discourse. Based on a series of studies by the author and others, the paper describes how the orientation of generation toward communicative intentions illuminates the central structural role played by intersegment discourse relations. It outlines several facets of discourse structure relations as they are required by and used in text planners --- their nature, number, and extension to associated tasks such as sentence planning and text formatting. In Artificial Intelligence 63, Special Issue on Natural Language Processing, 1993. This work was partially supported by the Rome Air Development Center under RADC contract FQ7619-8903326 -0001. 1 1 Introduction Every day, people produce thousands of words of connected...

this paper, we focus on two levels of analysis. The first involves the relation between the information conveyed in consecutive elements of a coherent discourse. Thus, for example, one utterance may describe an event that can be presumed to be the cause of another event described in the subsequent utterance. This causal relation is at what we will call the informational level. The second level of relation results from the fact that discourses are produced to effect changes in the mental state of the discourse participants. In coherent discourse, a speaker is carrying out a consistent plan to achieve the intended changes, and consecutive discourse elements are related to one another by means of the ways in which they participate in that plan. Thus, one utterance may be intended to increase the likelihood that the hearer will come to * Department of Computer Science and Intelligent Systems Program, University of Pittsburgh, Pittsburgh, PA 15260. e-mail: jmoore,pollackcs.pitt.edu 1 In addition, intentional structure is needed to make certain types of choices during the generation process, e.g., how to refer to an object (Appelt 1985)

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The growing interest in multimodal interface design is inspired in large part by the goals of supporting more transparent, flexible, efficient, and powerfully expressive means of humancomputer interaction than in the past. Multimodal interfaces are expected to support a wider range of diverse applications, to be usable by a broader spectrum of the average population, and to function more reliably under realistic and challenging usage conditions. In this paper, we summarize the emerging architectural approaches for interpreting speech and pen-based gestural input in a robust manner--- including early and late fusion approaches, and the new hybrid symbolic/statistical approach. We also describe a diverse collection of state-of-the-art multimodal systems that process users' spoken and gestural input. These applications range from map-based and virtual reality systems for engaging in simulations and training, to field medic systems for mobile use in noisy environments, to web-based transactions and standard text-editing applications that will reshape daily computing and have a significant commercial impact. To realize successful multimodal systems of the future, many key research challenges remain to be addressed. Among these challenges are the development of cognitive theories to guide multimodal system design, and the development of effective natural language processing, dialogue processing, and error handling techniques. In addition, new multimodal systems will be needed that can function more robustly and adaptively, and with support for collaborative multi-person use. Before this new class of systems can proliferate, toolkits also will be needed to promote software development for both simulated and functioning systems. Multimodal Speech and Gesture Interfaces 3 CONT...

We present an algorithm for simultaneously constructing both the syntax and semantics of a sentence using a Lexicalized Tree Adjoining Grammar (LTAG). This approach captures naturally and elegantly the interaction between pragmatic and syntactic constraints on descriptions in a sentence, and the inferential interactions between multiple descriptions in a sentence. At the same

We are studying how to create believable agents that perform actions and use natural language in interactive, animated, real-time worlds. Believable agents are autonomous agents that have specific, rich personalities like characters in movies and animation. We have extended Hap, the behavior-based architecture used by the Oz group to construct non-linguistic believable agents, to support natural language text generation. These extensions allow us to tightly integrate text generation with other aspects of the agent, including action, perception, inference and emotion. We describe our approach, and show how it leads to agents with properties we believe important for believability, such as: using language and action together to accomplish communication goals; using perception to help make linguistic choices; varying generated text according to emotional state; varying generated text to express the specific personality; and issuing the text in real-time with pauses, restarts and other brea...