Using a sledgehammer to crack a nut? Lexical diversity and event coreference resolution
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Summary
This paper asks whether the EventCorefBank (ECB), a widely used benchmark for within- and cross-document event coreference resolution, reflects the variety found in real news streams. To test this, the authors built a baseline that links event action mentions only when their lemmas match, using NLTK tools and the WordNet lemmatizer. Despite having no entity, syntactic or anaphora information, the baseline scored close to published machine-learning systems. When matching was limited to mentions inside the same topic, precision went up sharply. The authors conclude that most ECB topics cover only one seminal event, so the task largely collapses into topic classification. They also find little lexical variation within coreference chains. To fix this, they collected 502 new news texts describing a second instance of each event type already present in the 43 ECB topics. They then annotated the event components (action, time, location, human and non-human participants) and their coreference. The resulting ECB+ corpus is harder and more realistic, because systems must tell apart different events of the same type. It is freely available.
Key points
- The original ECB has 43 topics and 482 GoogleNews texts. ECB+ adds 502 texts, bringing the total to 982.
- The cross-topic lemma-match baseline reached 54.04 MUC F, 59.54 B3 F, 40.00 CEAFm, 56.91 BLANC F and 52.52 CoNLL F1. Restricting matching to within-topic pairs raised CoNLL F1 to 64.76 and B3 precision to 92.75.
- Annotation used 30 fine-grained tags grouped into 5 main event-component classes. Annotators did cross-document linking in the CROMER tool.
- Inter-annotator agreement (Cohen's Kappa, topics 1–4, 55 texts) was 0.74 for all 30 tags and 0.79 for the 5 main classes. Counting only tokens tagged by at least one annotator gave 0.63 and 0.68. Cross-document coreference agreement was 0.76.
- ECB+ can be downloaded from the NewsReader project site (newsreader-project.eu).
Cited by
Cite
@inproceedings{cybulska2014using,
title = {{Using a sledgehammer to crack a nut? Lexical diversity and event coreference resolution}},
author = {Cybulska, Agata and Vossen, Piek},
booktitle = {Proceedings of the Ninth International Conference on Language Resources and Evaluation (LREC'14)},
year = {2014},
url = {https://aclanthology.org/L14-1646/}
}References
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