This paper presents a framework and initial theory of "centering" to model the local component of attentional state in discourse. Centering examines the relationship between focus of attention, choice of referring expressions, and perceived coherence within a discourse segment. The authors argue that differences in coherence are partly due to the inference demands made by different types of referring expressions, given a particular attentional state. They demonstrate that the attentional state properties modeled by centering can account for these differences. The paper builds on previous research by Grosz, Joshi, and Weinstein (1983) and further develops the ideas presented in their 1986 draft manuscript. The authors define various centering constructs and propose two centering rules. They discuss the interactions between local coherence and the choice of referring expressions, emphasizing that different types of referring expressions (e.g., pronouns and definite descriptions) make different inference demands on the hearer or reader, affecting the perceived coherence of the discourse. The paper is organized into several sections, including an introduction, basic center definitions, claims of centering theory, constraints on center movement and realization, applications of the rules, and a discussion of the necessary properties of an underlying semantic framework. The authors provide examples to illustrate the concepts and argue that the centering framework can explain a range of variations in local coherence. They also discuss the implications of centering for discourse processing and interpretation systems.This paper presents a framework and initial theory of "centering" to model the local component of attentional state in discourse. Centering examines the relationship between focus of attention, choice of referring expressions, and perceived coherence within a discourse segment. The authors argue that differences in coherence are partly due to the inference demands made by different types of referring expressions, given a particular attentional state. They demonstrate that the attentional state properties modeled by centering can account for these differences. The paper builds on previous research by Grosz, Joshi, and Weinstein (1983) and further develops the ideas presented in their 1986 draft manuscript. The authors define various centering constructs and propose two centering rules. They discuss the interactions between local coherence and the choice of referring expressions, emphasizing that different types of referring expressions (e.g., pronouns and definite descriptions) make different inference demands on the hearer or reader, affecting the perceived coherence of the discourse. The paper is organized into several sections, including an introduction, basic center definitions, claims of centering theory, constraints on center movement and realization, applications of the rules, and a discussion of the necessary properties of an underlying semantic framework. The authors provide examples to illustrate the concepts and argue that the centering framework can explain a range of variations in local coherence. They also discuss the implications of centering for discourse processing and interpretation systems.