Zero Pronoun Resolution with Attention-based Neural Network
Summary
The paper addresses anaphoric zero pronoun resolution in Chinese, a pro-drop language. A zero pronoun is an omitted argument with no surface form, so it must be represented through its context. Earlier neural approaches either used only a few nearby words or treated every context word as equally relevant.
The authors propose a pair-wise neural model with two components:
- Zero pronoun encoder: a self-attentive mechanism, inspired by Lin et al. (2017), applies several attention hops over the words before and after the gap.
- Candidate encoder: an attention-based RNN encodes each candidate noun phrase. It uses the zero pronoun's vector to weight the words inside the mention.
The two vectors pass through tanh layers, which output a coreference score for each pronoun–candidate pair.
On the Chinese portion of OntoNotes 5.0, the model outperforms prior systems, including the strongest baseline (Liu et al., 2017), and is reported as state of the art. The work matters because it shows that selectively attending to context and to mention words helps represent elements absent from the text. This idea may carry over to other pro-drop languages.
Key points
- Candidate selection: noun phrases within two sentences of the gap, limited to max or modifier NPs. This retains about 98% of the true antecedents.
- Per-genre gains over Liu et al. (2017) in F-score:
- NW: +5.1
- BN: +4.6
- BC: +2.1
- WB: +1.5
- MZ: +1.2
- TC: +0.3
- Why TC lags: the gain on telephone conversation (TC) is marginal, which the authors attribute to short texts and many filler words.
- Number of attention hops (r): r = 2 gives the best results among the values tried (2–6).
- Ablation: removing attention entirely costs 0.9 F-score.
- Training dynamics: on the development set, F-score rises from about 46% after the first epoch to about 52% after roughly 30 iterations, then levels off.
- Case study: attention heat maps show the model focusing on informative words such as "数字证书/digital certificate".
Cited by
- Anaphoric Zero Pronoun Identification: A Multilingual Approach
- Cross-lingual Zero Pronoun Resolution
- Tackling Zero Pronoun Resolution and Non-Zero Coreference Resolution Jointly
- An Empirical Study of Contextual Data Augmentation for Japanese Zero Anaphora Resolution
- Pseudo Zero Pronoun Resolution Improves Zero Anaphora Resolution
- ZPR2: Joint Zero Pronoun Recovery and Resolution using Multi-Task Learning and BERT
Cite
@inproceedings{yin2018zero,
title = {{Zero Pronoun Resolution with Attention-based Neural Network}},
author = {Yin, Qingyu and Zhang, Yu and Zhang, Weinan and Liu, Ting and Wang, William Yang},
booktitle = {Proceedings of the 27th International Conference on Computational Linguistics},
year = {2018},
url = {https://aclanthology.org/C18-1002/}
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