COMP 4060 Natural Language Processing

1. COMP 4060 Natural Language Processing Discourse and Dialogue

2. Discourse and Dialogue • Discourse Phenomena • Speech Acts • Dialogue Acts

3. Discourse • Discourse = collocated, related group of sentences • Monologues and Dialogues • Referring Expressions: he, she • Coherence • Discourse Structure see Jurafsky and Martin, Ch. 18 and 19

4. Reference the Jurafsky • Referring Expressions • Referent the 406 textbook

5. Reference • Discourse Model - keeps track of representations of entities mentioned in discourse so far • Referring Expression - encodes information / signals for hearer to identify referent Methods: • Determine mapping from sign in referring expression to set of beliefs / discourse model of hearer. • Referents can be different parts, aspects of a sentence or utterance. • Use constraints on co-reference (syntax, discourse) to determine mapping.

6. Reference "According to John, Bob bought Sue an Integra, and Sue bought Fred a Legend." • But that turned out to be a lie.speech act • But that was false. proposition • That caused Sue to become rather poor. event • That caused both of them to become rather poor. combination of events

7. Reference • Indefinite / definite noun phrases • specific / non-specific entity • Pronouns • salience (last mentioned) • cataphora (pronoun mentioned before entity) • bound in context of "quantified variable" • Demonstratives (this, that) • "spatial proximity" (metaphorically), e.g. old - new car

8. Coherence Coherence Relations (Hobbs) – model "connectedness" of sentences in text • Result John bought an Acura. His father went ballistic. • Explanation John hid Bill's car keys. He was drunk. • Parallel John bought an Acura. Bill leased a BMW. • Elaboration John bought an Acura this weekend. He purchased a new beautiful Acura for ... on Saturday afternoon. • Occasion John bought an Acura. He drove to the ballgame.

9. Discourse Structure • Arrangement of sentence elements into (coherent) text / analysis of text according to coherence relations Jurafsky and Martin, Figure 18.10, p. 705

10. Speech Acts

11. Three Aspects of Speech Acts • Locutionary: the literal meaning of the utterance • Illocutionary: the social function that the utterance or written text has (e.g. informing, ordering, warning, undertaking.) • Perlocutionary: the result or effect that is produced by the utterance in that given context (e.g. convincing, persuading, deterring.)

12. Illocutionary Acts • Assertives • Directives • Commissives • Permissives • Prohibitives • Declaratives

13. Speech Acts • Assertives • committing the speaker to something's being the case • “The door is shut.” • Directives • attempts by the speaker to get the addressee to do something • “Shut the door.” • Commissives • committing the speaker to some future course of action • “I will shut the door.” • Expressives • expressing the psychological state of the speaker about a state of affairs • "Thanks for shutting the door."

14. Speech Acts • Permissives • allow / permit the hearer to a course of action as described by the propositional content of the utterance • "You may shut the door." • Prohibitives • deny the hearer to a course of action as described by the propositional content • "Don't shut the door." • Declarations / Declaratives • bringing about a different state of the world via the utterance • "You're fired."

15. DAMSL - Dialogue Act Markup in Several Layers • Statement • Info-request • Check • Influence on Addressee • Influence on Speaker • Offer • Commit • Conventional • Opening ...

17. Questions and Frames

18. Reference Dan Jurafsky and James H. Martin, Speech and Language Processing, 1st Edition, Chapters 18 and 19, Prentice-Hall, 2000