G22.2590 - Natural Language Processing - Spring 2010    Prof. Grishman

Lecture 13 Outline

April 22, 2010

Review feature vectors and similarity based on normalized dot product of vectors (from end of Lecture 12).
Term project status.

Question Answering and Summarization [J&M Chap 23]

Information Retrieval [J&M 23.1]

Factoid Question Answering [J&M 23.2]

    1. document retrieval (using IR techniques)
    2. passage retrieval ... selecting passages or sentences in the retrieved documents which are likely to contain the answer, based on the presence of individual keywords or sequences of keywords from the question as well as NEs of the type identified by question analysis
    3. answer extraction, using either the extended NE tagger or (for some answer types) specific patterns.  These are similar to relation extraction patterns, and can be written by hand or learned by bootstrapping.

Summarization [J&M 23.3]

Types of summarization

Generic single-document summarization

Generic multi-document summarization

Focused summarization