1. Referring Expressions: Definition
Referring expressions are words or phrases, the semantic interpretation of which is a discourse entity (also called referent)
Discourse entities are semantic objects and they can have multiple syntactic realizations within a text
Discourse entities live in the domain D, where a text is interpreted

2. Referring Expressions: Example
A pretty woman entered the restaurant. She sat at the table next to mine and only then I recognized her. This was Amy Garcia, my next door neighbor from 10 years ago. The woman has totally changed! Amy was at the time shy…

3. Pronouns vs. Full NP
A pretty woman entered the restaurant. She sat at the table next to mine and only then I recognized her. This was Amy Garcia, my next door neighbor from 10 years ago. The woman has totally changed! Amy was at the time shy…

4. Definite vs. Indefinite NPs
A pretty woman entered the restaurant. She sat at the table next to mine and only then I recognized her. This was Amy Garcia, my next door neighbor from 10 years ago. The woman has totally changed! Amy was at the time shy…

5. Common Noun vs. Proper Noun
A pretty woman entered the restaurant. She sat at the table next to mine and only then I recognized her. This was Amy Garcia, my next door neighbor from 10 years ago. The woman has totally changed! Amy was at the time shy…

6. Modified vs. Bare head NP
A pretty woman entered the restaurant. She sat at the table next to mine and only then I recognized her. This was Amy Garcia, my next door neighbor from 10 years ago. The woman has totally changed! Amy was at the time shy…

7. Premodified vs. postmodified
A pretty woman entered the restaurant. She sat at the table next to mine and only then I recognized her. This was Amy Garcia, my next door neighbor from 10 years ago. The woman has totally changed! Amy was at the time shy…

8. More NP types Inferrables Discontinuous sets
He bought a used car. The engine is rather noisy.\
Discontinuous sets
John has known Bill for many years now. They often go hiking together.

9. A more intriguing coloring…
A pretty woman entered the restaurant. She sat at the table next to mine and only then I recognized her. This was Amy Garcia, my next door neighbor from 10 years ago. The woman has totally changed! Amy was at the time shy…

10. Referring Expressions: Definition
Referring expressions are words or phrases, the semantic interpretation of which is a discourse entity (also called referent)
Discourse entities are semantic objects and they can have multiple syntactic realizations within a text
Discourse entities live in the domain D, where a text is interpreted

11. Referring expressions and discourse referents

12. Centering theory
(Gro 1995) examines interactions between local coherence and the choice of referring expressions
A pretty woman entered the restaurant. She sat at the table next to mine…
A woman entered the restaurant. They like icecream.

13. Crash course #1: Centering theory. Motivation
(Gro 1995) examines interactions between local coherence and the choice of referring expressions
Pronouns and definite descriptions are not equivalent with respect to their effect on coherence
They make different inference demands on the hearer or reader.

14. Crash course #1: Centering theory. Definitions
The centers of an utterance are discourse entities serving to link the utterance to other utterances
Forward looking centers – a ranked list
A backward looking center
Centers are semantic objects, not words, phrases, or syntactic forms but they are realized by such in the utterance

15. Anaphora resolution
Finding in a text all the referring expressions that have one and the same denotation
Pronominal anaphora resolution
Anaphora resolution between named entities
Full noun phrase anaphora resolution

16. Pronominal anaphora resolution
Rule-based vs statistical
(Ken 1996), (Lap 1994) vs (Ge 1998)
Performed on full syntactic parse vs on shallow syntactic parse
(Lap 1994), (Ge 1998) vs (Ken 1996)
Type of text used for the evaluation
(Lap 1994) computer manual texts (86% accuracy)
(Ge 1998) WSJ articles (83% accuracy)
(Ken 1996) different genres (75% accuracy)

17. Continued: Generic vs specific reference
1. The Vice-President of the United States is also President of the Senate.
2. Historically, he is the President’s key man in negotiations with Congress
3a. He is required to be 35 years old.
3b. As Ambassador to China, he handled many tricky negotiations, so he is well prepared for the job