Interpreting Vague Utterances in Context

Interpreting Vague Utterances in Context David DeVault and Matthew Stone Department of Computer Science Rutgers University Piscataway NJ 08854-8019 David.DeVault@rutgers.edu, Matthew.Stone@rutgers.edu Abstract We use the interpretation of vague scalar predi- cates like small as an illustration of how system- atic semantic models of dialogue context en- able the derivation of useful, fine-grained utter- ance interpretations from radically underspeci- fied semantic forms. Because dialogue context suffices to determine salient alternative scales and relevant distinctions along these scales, we can infer implicit standards of comparison for vague scalar predicates through completely general pragmatics, yet closely constrain the in- tended meaning to within a natural range. 1 Introduction Modeling context and its effects on interpretation may once have seemed to call for an open-ended in- vestigation of people’s knowledge of the common- sense world (Hobbs et al., 1993). But research on the semantics of practical dialogue (Allen et al., 2001) now approaches dimensions of context sys- tematically, through increasingly lightweight, fac- tored models. The evolving state of real-world ac- tivity proceeds predictably according to background plans and principles of coordination (Rich et al., 2001). The status of the dialogue itself is defined by circumscribed obligations to ground prior ut- terances, follow up open issues, and advance real- world negotiation (Larsson and Traum, 2000). Fi- nally, the evolving state of the linguistic context is a direct outgrowth of the linguistic forms inter- locutors use and the linguistic relationships among successive utterances (Ginzburg and Cooper, 2001; Asher and Lascarides, 2003). These compatible models combine directly to characterize an aggre- gate information state that provides a general back- ground for interpretation (Bunt, 2000). We argue in this paper that such integrated mod- els enable systems to calculate useful, fine-grained utterance interpretations from radically underspec- ified semantic forms. We focus in particular on vague scalar predicates like small or long. These predicates typify qualitative linguistic expression of quantitative information, and are thus both chal- lenging and commonplace. Building on a mul- tidimensional treatment of dialogue context, we develop and implement a theoretically-motivated model of vagueness which is unique in treating vague predicates as genuinely vague and genuinely context-sensitive, yet amenable to general processes of contextual and interpretive inference. 1.1 Semantic insights We pursue our argument in the context of an imple- mented drawing application, FIGLET, which allows users to give English instructions to draw a carica- ture of an expressive face. Figure 1 shows a repre- sentative interaction with FIGLET; the user gives the successive instructions in (1): (1) a. Make two small circles. b. Draw a long line underneath. Like Di Eugenio and Webber (1996), we empha- size that understanding such instructions requires contextual inference combining linguistic, task and domain knowledge. For example, consider the re- sponse to (1a) of placing circles so as to form the eyes of a new face. To recognize the possibility of drawing eyes exploits knowledge of the ongoing drawing task. To put the eyes where they belong in the upper part of the new face exploits domain knowledge. The response …

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