Discourse Structure

1
Discourse Structure

• Grosz and Sidner

2
Why bother?

• Leads to an account of discourse meaning
• Constrains how utterances are related
• Useful for explaining interruptions
• and the purpose of discourse participants

3
Linguistic

• Structure of the sequence of the utterances
• Discourse segments
• Utterances within a segment contribute to a
  common purpose
• Drawback hard to figure out segmentation
• Clues pause lengths, cue words, use of referring
  expressions

4
Intentional

• Discourse Purpose reason why discourse happens
  in the first place
• Discourse Segment Purpose how a segment
  contributes to the DP
• Relations
• Dominance (DSP1 dominates DSP2)
• Satisfaction Precedence (DSP1 sat-pres DSP2)

5
Attentional

• Different property fo Discourse not participants
• abstraction of the participants focus of
  attention as their discourse unfolds
• Dynamic stack that records salient objects,
  properties and relations
• Focusing process of manipulating focus spaces
  on attentional (focus) stack

6
Attentional

• DSs tied to focus spaces.
• Pushed and popped off stack depending on
  dominance hierarchy
• Focus stack only what is relevant at that time,
  Intentional complete record
• At end of discourse, focus stack is empty
• Only attentional state constrains referring
  expressions

7
Processing Issues

• How does OCP judge segmentation?
• Intention recognition
• Cue phrases
• Utterance level intentions
• Shared knowledge about actions and objects in
  domain

8
Processing Issues

• Recognition complete at end of segment
• But OCP must be able to recognize a
  generalization of DSP
• Focus Stack
• Constrain range of DSPs for relating to current
  DSP
• Constrain search for possible referents
  (centering)

9
Interruptions

• True Interruptions
• Weak Interruptions/Flashbacks
• Digressions