In this paper the Centering model of anaphoraresolution 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 modelis proven to be descriptively equivalent to an earlier algorithmicstatement of Centering due to Brennan, Friedman and Pollard(1987). However, the new model is stated declaratively, and makesclearer the status of the various constraints used in the theory. Inthe second part of the paper, the model is extended, demonstratingthe advantages of the (...) OT reformulation, and capturing formallyideas originally described by Grosz, Joshi and Weinstein. Three newapplications of the extended OT Centering model are described:generation of linguistic forms from meanings, the evaluation andoptimization of extended texts, and the interpretation of accentedpronouns. (shrink)