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

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…

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…

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…

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…

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…

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…

More NP types Inferrables 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.

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…

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

Referring expressions and discourse referents

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.

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.

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

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

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)

Continued: Generic vs specific reference 1. The Vice-President of the United States is also President of the Senate. 2. Historically, he is the Presidents 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