COMET: A Neural Framework for MT Evaluation
What it is about
The paper asks how to score a machine translation against human judgement more reliably than n-gram metrics such as BLEU. COMET encodes the source, the hypothesis and the reference with one cross-lingual pretrained encoder, pools the layers into one vector per segment, and regresses a quality score from combined features of those vectors. Two architectures are offered: an estimator trained on a quality score (DA, HTER or MQM), and a ranking model trained with a triplet loss that pulls a better hypothesis towards both the source and the reference. The authors train three models on QT21, WMT DA data and an internal MQM corpus. On the WMT 2019 metrics data, the ranking model gives the highest Kendall-type correlation on most English-source pairs. Dropping the raw source vector cost little; the source helped mainly through pair features.
Ideas
- I1. An anchored score for the translator's normal mode: judge each candidate against the source reading and the reference by counting concept overlap, not by embeddings. Compare it with exact match and chrF on the Bible pairs, and run it twice before any claim.
- I2. Pairwise training in count form: from the verse-aligned corpora, collect (better, worse) variants of one verse and fit a weight per feature by counting how often each feature orders the pair correctly. Keep the tables in BTreeMap order.
- I3. Repeat the paper's feature ablation: does the source side add anything beyond the product and difference terms? The meta-world keeps the source words, so this is a cheap control.
- I4. Report the ordering accuracy separately for close author pairs and distant ones, so that a scorer which only works for near pairs is visible.
For Mova
The neural encoder is not for Mova: the SLM has no pretrained cross-lingual model. The transferable parts are the two anchors (source and reference both judge the candidate) and the pairwise objective. The places are tools/translate (measure.rs, the normal-mode score) and the author-delta selection in tools/translate (meta.rs), where open problem 2 asks for a merge to stay only if it lowers the bits.
Cite
@inproceedings{rei2020comet,
title = {{COMET: A Neural Framework for MT Evaluation}},
author = {Rei, Ricardo and Stewart, Craig and Farinha, Ana C and Lavie, Alon},
booktitle = {Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP)},
year = {2020},
doi = {10.18653/v1/2020.emnlp-main.213},
eprint = {2009.09025},
archivePrefix = {arXiv},
url = {https://doi.org/10.18653/v1/2020.emnlp-main.213}
}References
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