CAW-coref: Conjunction-Aware Word-level Coreference Resolution
Summary
Coreference resolution groups text mentions that point to the same entity. The strongest current systems call large language models many times per document, which is too costly for large-scale information extraction. Word-level coreference (WL-coref) is much cheaper. A single pass of roberta-large produces word embeddings, a light scorer links coreferent words, and full spans are then recovered around those words. The authors trace a recurring weakness to how WL-coref turns span-annotated OntoNotes into word-level training data. Each span gets one head-word from the dependency parse, so a coordinated mention like "Tom and Mary" shares its head with "Tom". This causes conflicting links, and one of them must be discarded. It also makes span extraction for nested mentions ambiguous. Their fix is to treat the coordinating conjunction as the head-word of such spans, detected using POS tags and dependency depth. Retraining with unchanged hyperparameters yields CAW-coref. It raises OntoNotes test F1 without adding model complexity and becomes the strongest efficient coreference model reported.
Key points
- On the OntoNotes 5.0 English test set, CAW-coref reaches 81.6% average F1, compared with 80.7% for the rerun WL-coref baseline (+0.9). This closes 34.6% of the gap to the SOTA link-append system, which scores 83.3% using a 13B mT5-XXL model.
- Both WL-coref and CAW-coref need just a single forward pass through roberta-large (355M) and have O(n²) complexity. Autoregressive methods such as link-append, ASP and corefqa need at least O(n) LM passes per document.
- The new head-word rule works as follows. A coordinating conjunction (and, or, plus) found via OntoNotes POS tags becomes the head-word if it lies less than two dependency steps from the span's original head. About 1.17% of spans in the train and dev splits are conjoined entities.
- CAW-coref also beats LingMess (81.4%), the best span-based model, which relies on ensembling. The code is available at github.com/KarelDO/wl-coref.
- Some limitations remain. Chained conjunctions like "Tom and Mary and David" have more mentions than words, so they cannot be fully handled. Conjunctions expressed with commas or hyphens are also not detected.
Cited by
- CorefInst: Leveraging LLMs for Multilingual Coreference Resolution
- Findings of the Fourth Shared Task on Multilingual Coreference Resolution: Can LLMs Dethrone Traditional Approaches?
Cite
@inproceedings{doosterlinck2023caw,
title = {{CAW-coref: Conjunction-Aware Word-level Coreference Resolution}},
author = {D'Oosterlinck, Karel and Bitew, Semere Kiros and Papineau, Brandon and Potts, Christopher and Demeester, Thomas and Develder, Chris},
booktitle = {Proceedings of the Sixth Workshop on Computational Models of Reference, Anaphora and Coreference (CRAC 2023)},
year = {2023},
doi = {10.18653/v1/2023.crac-main.2},
eprint = {2310.06165},
archivePrefix = {arXiv},
url = {https://doi.org/10.18653/v1/2023.crac-main.2}
}References
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- Model Step Prediction Correct WL-coref WL-coref CAW-coref CAW-coref word span word span Tom and Anna are talking. They are talking. Tom and Anna are talking. They are talking. Tom and Anna are talking. They are talking. Tom and Anna are talking. They are talking. Yes No Yes Yes WL-coref WL-coref CAW… find
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