Focusing on focus: a formalization

Proceedings of EACL '99 Focusing on focus: a formalization Yah Zuo Letteren/GM/CLS Postbus 90153 5000LE Tilburg The Netherlands yzuo@kub.nl Abstract We present an operable definition of focus which is argued to be of a cognito-pragmatic nature and explore how it is determined in discourse in a formalized manner. For this purpose, a file card model of discourse model and knowledge store is introduced enabling the decomposition and formal representation of its determination process as a programmable algorithm (FDA). Interdisciplinary evidence from social and cognitive psychology is cited and the prospect of the integration of focus via FDA as a discourse-level construct into speech synthesis systems, in particular, concept-to- speech systems, is also briefly discussed. 1. Introduction The present paper aims to propose a working definition of focus and thereupon explore how focus is determined in discourse; in doing so, it hopes to contribute to the potential integration of a focus module into speech synthesis systems, in particular, concept-to-speech ones. The motivation largely derives from the observation that focus, though recognized as 'the meeting point of linguistics and artificial intelligence' (Hajicova, 1987) carrying significant discourse information closely related to prosody generation, has nonetheless appeared evasive and intractable to formalization. Most current speech synthesis systems simply take focus as the point of departure in an a priori manner whilst few have looked into the issue of how focus occurs as it is, namely, how focus is determined (by the speaker presumably) in the discourse. We aim to redress this inadequacy by first defining focus as a cognito- pragmatic category, which then enables a formal and procedural characterization of focus determination process in discourse, captured as focus determination algorithm (FDA). The FDA to be proposed is largely based on human-human dialogue (though space consideration precludes the full presentation of data), but is believed to be applicable to human-computer interaction as well. The study is characterized by its interdisciplinary approach, combining insights and inputs from linguistics, neuroscience and social psychology. 2. Defining focus: a eognito-pragmatie category The term focus has been used in various senses, at least six of which can be identified, i.e., phonological (Pierrehumbert, 1980; Ladd, 1996), semantic (Jackendoff, 1972; Prince, 1985), syntactic (Rochemont, 1986), cognitive (Sanford & Garrod, 1981; Musseler et al., 1995), pragmatic (Halliday, 1967), and AI-focus (Grosz & Sidner, 1986) ~. We argue that, first, these multiple uses of focus, though resulting in conceptual confusion, hint at the central status of the notion in core as well as peripheral linguistics. Second, focus as occurs in discourse is best captured by referring to both the interlocutors' cognitive computation and constant interaction, in accordance with the dual (i.e., cognitive and pragmatic) nature of discourse per se (Nuyts, 1992). Of the six above-mentioned senses, the cognitive and pragmatic ones serve as the basis for the present definition, although the caveat is immediately made that the two aspects are to be fully integrated rather than merely added together. Moreover, neither is to be adopted blindly given certain shortcomings of previous accounts of each, …

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