CCAligned: A Massive Collection of Cross-Lingual Web-Document Pairs
Written for the Research library (claude-opus-5-5) from the paper text. Original — aclanthology.org/2020.emnlp-main.480.pdf
Summary
Finding web pages that translate one another is valuable for machine translation and other cross-lingual NLP work. Labeling such pairs by hand is costly, because the number of candidate pairs grows quadratically, and it is especially difficult for low-resource languages. El-Kishky et al. use weak supervision from URLs instead. They deduplicate 68 Common Crawl snapshots, tag each page's language with FastText, and pair URLs that become identical once language markers (such as "en-gb" or "lang=fr") are removed. A pair is kept only if the removed marker agrees with the detected language of the page.
The resulting dataset, CCAligned, is a URL-level collection of document pairs. Human annotators judged it highly precise, though the URL rules sacrifice recall. The authors also provide a benchmark subset and baselines that align documents using embeddings of their content. Sentences mined from the English-paired documents train NMT models whose quality is comparable to models trained on ParaCrawl. CCAligned therefore greatly extends multilingual coverage, particularly for low-resource and non-European language pairs.
Key points
- Scale: The source was 169.4B raw documents from 68 Common Crawl snapshots (2013–2020). Deduplication reduced this to about 29.6B documents from 107.8M domains, an 83% cut.
- Output: Over 392M aligned document pairs across 8144 language pairs and 138 languages. About 100M pairs include English (137 English pairs) and 292M do not.
- Human evaluation: Annotators checked 180 URL pairs, 30 each for German, Chinese, Arabic, Romanian, Estonian and Burmese. Each pair was rated by three people.
- Average majority-vote precision was 84.4%.
- Precision adjusted for experimental error was 94.5%.
- Krippendorff's α was 0.70.
- Benchmark set: 121K documents from 450 web domains, containing 17.5K URL-aligned pairs, for testing content-based alignment methods.
- Downstream MT:
- LASER with margin-based filtering mined over 1B unique parallel sentences.
- fairseq transformer models were trained on these sentences and tested on TED talk test sets.
- BLEU was roughly on par with ParaCrawl v6 and higher than WikiMatrix.
- The URL lists and code are released at statmt.org/cc-aligned.
Cited by
- Findings of the 2021 Conference on Machine Translation (WMT21)
- Tower: An Open Multilingual Large Language Model for Translation-Related Tasks
- IndicTrans2: Towards High-Quality and Accessible Machine Translation Models for all 22 Scheduled Indian Languages
- Findings of the WMT24 General Machine Translation Shared Task: The LLM Era Is Here but MT Is Not Solved Yet
- Findings of the WMT25 General Machine Translation Shared Task: Time to Stop Evaluating on Easy Test Sets
- Quality at a Glance: An Audit of Web-Crawled Multilingual Datasets
- Samanantar: The Largest Publicly Available Parallel Corpora Collection for 11 Indic Languages
Cite
@inproceedings{elkishky2020ccaligned,
title = {{CCAligned: A Massive Collection of Cross-Lingual Web-Document Pairs}},
author = {El-Kishky, Ahmed and Chaudhary, Vishrav and Guzmán, Francisco and Koehn, Philipp},
booktitle = {Proceedings of the 2020 Conference on Empirical Methods in Natural Language Processing (EMNLP)},
year = {2020},
doi = {10.18653/v1/2020.emnlp-main.480},
url = {https://doi.org/10.18653/v1/2020.emnlp-main.480}
}References
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