Discourse

1
Discourse
Read J M Chapter 18.1
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More than One Sentence at a Time
The alphas have a long-standing hatred of the
betas. Their leaders have decided that the time
has come to launch an attack. They are
considering the Thanksgiving weekend.
Suppose we are trying to do text extraction and
we want to fill in records such
as attack (status ltplanned, imminent, active,
completedgt) (attacker ) (attackee ) (locati
on ) (mode-of-attack ) (time-of-attack )
(credit-claimer )
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Or Dialogue Management
Reference resolution gt Who planned the October
attack? The UMPA guerrillas. gt Who is their
leader? Coherence http//www.alicebot.org/
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Or Machine Translation
English John saw a new bicycle at the store.
He wants it. French John a vu une nouvelle
bicyclette au magasin. Il le/la veut. from
Babel Fish John a vu une nouvelle bicyclette au
magasin. Il le veut.
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Reference Resolution
Indefinite NPs A boy and a girl came in.
They were happy. The girl laughed. Definite
NPs The city council will vote tomorrow.
John went to the store/hospital. (brit)
John went to hospital.
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Pronouns

1. John went wrote a new book. It is a bestseller.
2. John went to the store with Bill. He bought a
   new TV.
3. John was the first person to get there. Bill
   arrived a bit later. He brought the cookies and
   tea.
4. John parked his car in his garage. It is
   incredibly messy, with old bike and car parts
   lying around everywhere.
5. John parked his car in Beverly Hills. It is
   incredibly messy, with old bike and car parts
   lying around everywhere.
6. Nancy ate her oatmeal this morning because she
   heard that it lowers cholesterol.
7. Nancy hates raccoons because they ate her corn
   last year.
8. If a farmer owns a donkey, he beats it.
9. If a farmer doesnt own a donkey, he beats it.
10. Why dont they ever fix the roads?

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One Anaphora

1. I just saw the new Hondas. I want one.
2. Reserve a seat for me on the flight. Reserve one
   for Jack too.
3. John has a red jumper and a blue one.
4. I saw two bears in the woods. Bill saw some in
   the parking lot too.
5. Is there a flight to Melbourne before 7am? No
   but there is one at 9.

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A Discourse Model

• A realistic model has three layers
• Linguistic
• Discourse (pegs)
• Knowledge base
• Examples
• There are a lot of books in the room. Pick one.
  Look at the title page. It should contain both
  the authors name and the title.
• John wants Bill to know about the movie. He
  thinks he would like it.

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A Blackboard Model
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Constraint Sources

• Each constraint source has four components
• Modeller
• Constraint poster
• Proposer
• Evaluator

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The Process
Each CS updates its model if necessary. Each CS
posts constraints if necessary. Example He saw
him. Each CS has the opportunity to propose
candidates. Evaluation
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Kinds of Constraint Sources
Finite set generators (e.g., reflexive
pronouns) Fading infinite set generators (e.g.,
recency) Filters (number agreement) Preferences
(semantic coherence)
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Coherence
Mary gave Sue her favorite book. It was hard to
part with it, but she knew it would be
appreciated. Mary gave Sue her favorite book.
Shell always be grateful for that. Mary gave
Sue her favorite book. Shes very tall. The
problem with coherence It appears to be an AI
complete problem.