Functional Centering - Grounding Referential Coherence in Information Structure

Considering empirical evidence from a free-word-order language (German) we propose a revision of the principles guiding the ordering of discourse entities in the forward-looking center list within the centering model. We claim that grammatical role criteria should be replaced by criteria that reflect the functional information structure of the utterances. These new criteria are based on the distinction between hearer-old and hearer-new discourse entities. We demonstrate that such a functional model of centering can be successfully applied to the analysis of several forms of referential text phenomena, viz. pronominal, nominal, and functional anaphora. Our methodological and empirical claims are substantiated by two evaluation studies. In the first one, we compare success rates for the resolution of pronominal anaphora that result from a grammaticalrole-driven centering algorithm and from a functional centering algorithm. The second study deals with a new cost-based evaluation methodology for the assessment of centering data, one which can be directly derived from and justified by the cognitive load premises of the centering model.