Detecting anaphoricity and antecedenthood for coreference resolution
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Detecting Anaphoricity and Antecedenthood for Coreference Resolution. Olga Uryupina ( uryupina @ gmail . com ) Institute of Linguistics, RAS 13.11.08. Overview. Anaphoricity and Antecedenthood Experiments Incorporating A&A detectors into a CR system Conclusion. A&A: example.

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Detecting Anaphoricity and Antecedenthood for Coreference Resolution

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Detecting anaphoricity and antecedenthood for coreference resolution

Detecting Anaphoricity and Antecedenthood for Coreference Resolution

Olga Uryupina ([email protected])

Institute of Linguistics, RAS

13.11.08


Overview

Overview

  • Anaphoricity and Antecedenthood

  • Experiments

  • Incorporating A&A detectors into a CR system

  • Conclusion


A a example

A&A: example

Shares in Loral Space will be distributed to Loral shareholders. The new company will start life with no debt and $700 million in cash. Globalstar still needs to raise $600 million, and Schwartz said that the company would try to raise the money in the debt market.


A a example1

A&A: example

Shares in Loral Space will be distributed to Loral shareholders. The new company will start life with no debt and $700 million in cash. Globalstar still needs to raise $600 million, and Schwartz said that the company would try to raise the money in the debt market.


Anaphoricity

Anaphoricity

Likely anaphors:

- pronouns, definite descriptions

Unlikely anaphors:

- indefinites

Unknown:

- proper names

Poesio&Vieira: more than 50% of definite descriptions in a newswire text are not anaphoric!


A a example2

A&A: example

Shares in Loral Space will be distributed to Loral shareholders. The new company will start life with no debt and $700 million in cash. Globalstar still needs to raise $600 million, and Schwartz said that the company would try to raise the money in the debt market.


A a example3

A&A: example

Shares in Loral Space will be distributed to Loral shareholders. The new company will start life with no debt and $700 million in cash. Globalstar still needs to raise $600 million, and Schwartz said that the company would try to raise the money in the debt market.


Antecedenthood

Antecedenthood

Related to referentiality (Karttunen, 1976):

„no debt“ etc

Antecedenthood vs. Referentiality: corpus-based decision


Experiments

Experiments

  • Can we learn anaphoricity/antecedenthood classifiers?

  • Do they help for coreference resolution?


Methodology

Methodology

  • MUC-7 dataset

  • Anaphoricity/antecedenthood induced from the MUC annotations

  • Ripper, SVM


Features

Features

  • Surface form (12)

  • Syntax (20)

  • Semantics (3)

  • Salience (10)

  • „same-head“ (2)

  • From Karttunen, 1976 (7)

    49 features – 123 boolean/continuous


Results anaphoricity

Results: anaphoricity


Results antecedenthood

Results: antecedenthood


Integrating a a into a cr system

Integrating A&A into a CR system

Apply an A&A prefiltering before CR starts:

  • Saves time

  • Improves precision

    Problem: we can filter out good candidates..:

    - Will loose some recall


Oracle based a a prefiltering

Oracle-based A&A prefiltering

Take MUC-based A&A classifier („gold standard“

CR system: Soon et al. (2001) with SVMs

MUC-7 validation set (3 „training“ documents)


Oracle based a a prefiltering1

Oracle-based A&A prefiltering


Automatically induced classifiers

Automatically induced classifiers

Precision more crucial than Recall

Learn Ripper classifiers with different Ls (Loss Ratio)


Anaphoricity prefiltering

Anaphoricity prefiltering


Antecedenthood prefiltering

Antecedenthood prefiltering


Conclusion

Conclusion

Automatically induced detectors:

  • Reliable for anaphoricity

  • Much less reliable for antecedenthood

    (a corpus, explicitly annotated for referentiality could help)

    A&A prefiltering:

  • Ideally, should help

  • In practice – substantial optimization required


Thank you

Thank You!


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