G22.2590 - Natural Language Processing - Spring 2006 Prof. Grishman

Lecture 12 Outline

April 18, 2006

Discourse.  Until now we considered the structure and meaning of sentences in isolation.  We now turn to issues primarily connected with multi-sentence text -- discourse.

Reference Resolution (J&M 18.1)

Terminology

Types of referring expressions

Complications

Resolving pronoun reference

Resolving other referring expressions

Anaphora resolution in Jet

Using anaphora resolution for extraction:  an example

In many cases, we want to be able to retrieve an argument from context when it is not part of the immediate syntactic structure.  A simple way of doing this is to generate a zero anaphor (an ngroup constituent not spanning any text) and then let reference resolution map it to an entity.  We have created a version of the AppointPatterns which uses this method to collect organization names and, in some cases, people names.

Discourse Analysis:  Analyzing Text Coherence  (J&M 18.2)

Why are we interested in analyzing the structure of a discourse beyond the sentence level? How to analyze text coherence?