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

Olga Uryupina ([email protected])

Institute of Linguistics, RAS

13.11.08


Overview

  • Anaphoricity and Antecedenthood

  • Experiments

  • Incorporating A&A detectors into a CR system

  • Conclusion


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: 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

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: 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: 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

Related to referentiality (Karttunen, 1976):

„no debt“ etc

Antecedenthood vs. Referentiality: corpus-based decision


Experiments

  • Can we learn anaphoricity/antecedenthood classifiers?

  • Do they help for coreference resolution?


Methodology

  • MUC-7 dataset

  • Anaphoricity/antecedenthood induced from the MUC annotations

  • Ripper, SVM


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: antecedenthood


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

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 prefiltering


Automatically induced classifiers

Precision more crucial than Recall

Learn Ripper classifiers with different Ls (Loss Ratio)


Anaphoricity prefiltering


Antecedenthood prefiltering


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!


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