Discourse Representation Theory models meaning across sentences, building structures with referents and conditions. It interprets sentences based on context and resolves anaphora by linking to referents. This approach captures how meaning accumulates through discourse.

Centering Theory tracks entity salience in discourse, classifying transitions between utterances. It aids anaphora resolution by preferring the most salient entity as antecedent. Both theories offer complementary insights into how we interpret connected language.

Discourse Representation Theory

Concepts of discourse representation theory

• Models meaning of a discourse (sequence of sentences or utterances in a context)
• Constructs a Discourse Representation Structure (DRS) captures cumulative meaning of a discourse
  • DRS consists of discourse referents (entities introduced in the discourse, represented by variables like x, y) and conditions (predicate-argument structures or relations between discourse referents)
• Assumes interpretation of a sentence depends on context provided by preceding discourse
• Resolves anaphoric expressions (pronouns) by linking them to appropriate discourse referents in the DRS

Centering Theory and Anaphora Resolution

Application of centering theory

• Discourse coherence model tracks local attentional state (salience of entities) in a discourse
• Each utterance evokes forward-looking centers (Cf, potential candidates for Cb of following utterance, ranked by salience) and a single backward-looking center (Cb, most salient entity in previous utterance realized in current utterance)
• Classifies transitions between utterances based on Cb and Cf relationships
  1. Continue: Cb(Un) = Cb(Un-1), Cb(Un) is most salient entity in Cf(Un)
  2. Retain: Cb(Un) = Cb(Un-1), Cb(Un) is not most salient entity in Cf(Un)
  3. Smooth-shift: Cb(Un) ≠ Cb(Un-1), Cb(Un) is most salient entity in Cf(Un)
  4. Rough-shift: Cb(Un) ≠ Cb(Un-1), Cb(Un) is not most salient entity in Cf(Un)
• Predicts discourses with more continue transitions are more coherent

Discourse structure in anaphora resolution

• Anaphoric references (pronouns, definite descriptions) depend on discourse structure for interpretation
• DRT resolves anaphoric references by linking them to accessible discourse referents in DRS
  • Accessibility determined by hierarchical structure of DRS and scope of quantifiers and negation
• Centering theory resolves anaphoric references by preferring Cb as antecedent
  • If Cb is not suitable antecedent, considers other entities in Cf in order of salience

Discourse representation vs centering theory

• Both DRT and centering theory aim to resolve anaphoric references in discourse
• DRT focuses on global discourse structure and accessibility of discourse referents
  • Constructs cumulative representation of discourse (DRS) to resolve anaphora
• Centering theory focuses on local attentional state and salience of entities
  • Uses Cb and Cf to resolve anaphora based on local coherence constraints
• DRT provides more comprehensive account of anaphora resolution (considers quantifier scope, negation)
• Centering theory offers insights into role of entity salience and local coherence in anaphora resolution
• Approaches can be seen as complementary (DRT captures global discourse structure, centering theory captures local attentional state)