Coreference Resolution across Corpora: Languages, Coding Schemes, and Preprocessing Information
What it is about
The paper shows that a coreference score says as much about the corpus as about the system. The same entity-based system, CISTELL, is trained and tested under three corpus choices: language (English against Spanish, using OntoNotes and AnCora, both news), coding scheme (ACE against OntoNotes on the same 100,000-word TDT portion), and preprocessing (gold against automatic parses). The system uses four basket-growing strategies (head match, strong match, best match, weak match) and a memory-based classifier. The scores are MUC, B3 and CEAF. The rankings of the strategies disagree across the metrics: MUC rewards weak match most, B3 rewards head match most, and CEAF is split between super-strong and best match. In both datasets about 85% of entities are singletons and 15% have two or more mentions, with 3.9 mentions per multi-mention entity in AnCora and 3.5 in OntoNotes. The authors conclude that system comparison is only meaningful when corpus parameters match exactly.
Ideas
- I1. Run Mova's sieve on the same text with two annotation schemes (for example, with and without appositives and predicate nominals as coreferent) and report the change in each score. A change that appears only under one scheme is a scheme effect, not a system effect.
- I2. Put the metric disagreement into
coref/src/eval.rs: a table of MUC, B3 and CEAF for each variant of the sieve, and a rule that a claim of improvement needs the same ranking in at least two of the three metrics. - I3. Mention-type table for Spanish-English contrast: the paper shows zero subjects change the mention distribution. Mova's English-only setting can measure the same kind of shift on a set of sentences with pronoun-dropped and full-subject variants, as a check of the pronoun rules in languages/en/12-pronouns-determiners-numerals.md.
For Mova
Code: coref/src/eval.rs (three metrics side by side), coref/src/sieve.rs (variants as separate configurations), coref/src/corefud.rs (scheme conversion). Chapter: languages/en/35-reference-and-coreference.md. Measure: the sieve under two scheme settings and three metrics, with the rankings printed; run twice and compare the output files byte for byte.
Library summary
Written for the Research library (claude-opus-5-5) from the paper text, in our own words: the license "CC BY-NC-SA 3.0 (ACL Anthology, before 2016)" does not allow redistributing the text itself. Original — aclanthology.org/P10-1144.pdf
Summary
The paper asks how much a coreference resolver's reported score depends on the corpus rather than on the system. Recasens and Hovy keep a single system fixed: CISTELL, an entity-based resolver that grows "baskets" of attributes for discourse entities and uses a TiMBL memory-based pairwise classifier. They then vary three corpus parameters one at a time. Language is varied by comparing English with Spanish (AnCora). Annotation scheme is varied by comparing ACE and OntoNotes on a shared 100k-word TDT portion. Preprocessing is varied by comparing gold-standard and automatic linguistic information. Every configuration includes three baselines and four clustering models, all run on true mentions and scored with MUC, B3 and CEAF. Scores shift substantially with each parameter, and the three metrics show systematic biases that often rank the models in contradictory orders. The authors conclude that two systems can be compared fairly only when they use the same corpus, the same preprocessing and the same measures, and all measures agree. This matters for anyone who benchmarks coreference systems or builds annotated corpora.
Key points
- Setup: There are three baselines (ALL SINGLETONS, HEAD MATCH, HEAD MATCH + PRON) and four CISTELL models (STRONG, SUPER STRONG, BEST and WEAK MATCH). SUPER STRONG MATCH accepts a link only when the TiMBL distance is below 0.09. English uses 29 pairwise features; Spanish uses 34, partly to handle zero subjects.
- Aligned data: The ACE/OntoNotes aligned portion has 297 training and 33 test documents, about 80.8k and 9.1k words respectively.
- Preprocessing effect: On ACE, automatic preprocessing lowered scores by roughly 3% compared with gold OntoNotes information. Dropping the noisy grammatical-function feature then raised results by about 2–3%.
- Metric biases:
- MUC is too forgiving of spurious links.
- B3 is inflated when a corpus contains many singletons.
- CEAF disagrees with both.
- In one table, the model B3 ranks highest is the one MUC ranks lowest.
- External support: In SemEval-2010 Task 1, even the strongest systems struggled to beat the all-singletons baseline.
Cite
@inproceedings{recasens2010coreference,
title = {{Coreference Resolution across Corpora: Languages, Coding Schemes, and Preprocessing Information}},
author = {Recasens, Marta and Hovy, Eduard},
booktitle = {Proceedings of the 48th Annual Meeting of the Association for Computational Linguistics},
year = {2010},
url = {https://aclanthology.org/P10-1144/}
}References
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