Centering: A Framework for Modeling the Local Coherence of Discourse

1 Introduction

1. What does centering theory model?
   The local component of attentional state: relationships among focus of attention, choice of referring expression (pronoun vs full noun phrase) and perceived coherence of the utterances within a discourse segment.
   • Grosz et al., 1995, Centering (Computational Linguistics), §1
2. Why was this 1995 paper published so long after the theory was proposed?
   Centering was presented in 1983 and elaborated in a draft that circulated from 1986 and was widely cited and extended but never published; this paper gives the definitive statement of the original motivations, definitions and claims.
   • Grosz et al., 1995, Centering (Computational Linguistics), §1
3. What are the three components of discourse structure in Grosz and Sidner’s theory, into which centering fits?
   Linguistic structure (discourse segments, possibly embedded), intentional structure (the discourse purpose and discourse segment purposes, and relations among them) and attentional state (the participants’ focus of attention). Centering models the local level of attentional state.
   • Grosz et al., 1995, Centering (Computational Linguistics), §1
4. Distinguish local and global coherence, and how each is modelled.
   Local coherence holds among utterances within a segment, modelled by centering. Global coherence holds between segments and depends on intentional structure; Grosz and Sidner model global attentional state with a stack of focus spaces pushed and popped according to intentional relations.
   • Grosz et al., 1995, Centering (Computational Linguistics), §1
5. Which earlier work did centering build on?
   Grosz’s (1977) global vs immediate focusing; Sidner’s (1979) analysis of immediate focus (discourse focus vs potential foci) with rules for resolving pronouns; and Joshi, Kuhn and Weinstein’s work linking changes in immediate focus to the complexity of inference, which introduced the term “centering”.
   • Grosz et al., 1995, Centering (Computational Linguistics), §1