The optimization of discourse anaphora

In this paper the Centering model of anaphora resolution and discourse coherence (Grosz et al. 1983, 1995) is reformulated in terms of Optimality Theory (OT) (Prince and Smolensky 1993). One version of the reformulated model is proven to be descriptively equivalent to an earlier algorithimic statement of Centering due to Brennan, Friedman and Pollard (1987). However, the new model is stated declaratively, and makes clearer the status of the various constraints used in the theory. In the second part of the paper, the model is extended, demonstrating the advantages of the OT reformulation, and capturing formally ideas originally described by Grosz, Joshi, and Weinstein. Three new applications of the extended OT centering model are described: generation of linguistic forms from meanings, the evaluation and optimization of extended texts, and the interpretation of accented pronouns.