Exploiting Zero Pronouns to Improve Chinese Coreference Resolution
Summary
Chinese often leaves pronouns unexpressed. Kong and Ng ask whether recovering these zero pronouns (ZPs) can help a Chinese coreference resolver. They start from a learning-based baseline that has two parts: an anaphoricity classifier and a mention-pair resolver. The resolver uses the 12 features of Soon et al. (2001) plus extra features for pronoun type, speakers and document parts, all trained with SVM-light on the CoNLL-2012 shared task data. To find ZPs, the authors detect clauses with a simplified semantic role labeling framework. They then use the detected ZPs in two ways. First, they retrain the syntactic parser with ZPs inserted. Second, they change how training examples are generated, treating ZPs as a special pronoun. With automatically detected ZPs, the system improves under every mention setting. With automatic mentions and with gold mention boundaries, it beats the top three CoNLL-2012 Chinese closed-track systems. This matters because it is reported as the first work to show that ZPs give a significant gain for Chinese coreference.
Key points
- In a corpus study of OntoNotes v5.0, anaphoric ZPs make up 10.7% of coreference-chain mentions in the training data and 11.3% in the development data.
- Adding ZPs to the Berkeley parser improves parsing F-measure by 1.8% with gold ZPs and by 1.4% with automatically detected ZPs.
- With automatic mentions, the average F-measure rises from 60.71 to 63.07. MUC gains 3.31, BCUBED 1.42 and CEAF 2.34.
- The refined parser mainly raises recall, while refined example generation mainly raises precision. Combining the two works best, and gold ZPs push the average to 65.14.
- Automatic ZPs close roughly half of the gap between using no ZPs and using gold ZPs. For correctly identified anaphoric ZPs on the dev set, resolution precision reaches 94.76%.
Cited by
- Investigating Multilingual Coreference Resolution by Universal Annotations
- Chinese Zero Pronoun Resolution: A Joint Unsupervised Discourse-Aware Model Rivaling State-of-the-Art Resolvers
- Tackling Zero Pronoun Resolution and Non-Zero Coreference Resolution Jointly
Cite
@inproceedings{kong2013exploiting,
title = {{Exploiting Zero Pronouns to Improve Chinese Coreference Resolution}},
author = {Kong, Fang and Ng, Hwee Tou},
booktitle = {Proceedings of the 2013 Conference on Empirical Methods in Natural Language Processing},
year = {2013},
url = {https://aclanthology.org/D13-1028/}
}References
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