A Monolingual Approach to Contextualized Word Embeddings for Mid-Resource Languages
Written for the Research library (claude-opus-5-5) from the paper text. Original — aclanthology.org/2020.acl-main.156.pdf
Summary
Contextualized language models need large amounts of raw text. For many mid-resource languages, the usual source, Wikipedia, is small and covers only one encyclopedic genre. The authors ask whether a much larger but noisier web corpus can make up for its lower quality. They train ELMo embeddings for Bulgarian, Catalan, Danish, Finnish and Indonesian twice: once on complete Wikipedia dumps and once on the matching OSCAR subcorpora. OSCAR was built from Common Crawl through fastText language identification, line-length filtering and deduplication, and no limit is placed on the amount of training text. Each embedding set is attached to UDPipe 2.0 and tested on POS tagging and dependency parsing across six UD treebanks. The OSCAR-based models beat the Wikipedia-based ones in every case and match or exceed the previous state of the art, which was mostly held by multilingual BERT systems. The study suggests that size and variety in a well-filtered crawl can outweigh both textual cleanliness and the benefits of cross-lingual models. This is encouraging for languages whose curated resources are limited in volume or genre.
Key points
- Corpus sizes: OSCAR subcorpora are much larger than the Wikipedia corpora. OSCAR ranges from about 4.3 GB (Catalan) to 16 GB (Indonesian), while Wikipedia ranges from 338 MB (Danish) to 1.1 GB (Catalan). OSCAR comes from the November 2018 Common Crawl snapshot.
- OSCAR pipeline: It follows Grave et al. (2018) and uses a fastText classifier covering 176 languages. One change was made to the filter: lines must contain at least 100 UTF-8 characters rather than 100 bytes, so languages written in non-ASCII scripts are not penalized. Duplicate lines are removed.
- Results: With UDPipe 2.0, the OSCAR-based ELMo models set new state-of-the-art POS tagging and LAS-style parsing results on all 6 treebanks. They outperform mBERT-based systems and differ from the HIT-SCIR ELMo models (CoNLL 2018), which were trained on at most 20 million words.
- Training epochs: Running more epochs tends to improve the embeddings, even when the training corpus is as small as the Wikipedia data.
- Compute and release: The models were trained in France, where grid emissions were about 51 g CO2/kWh, and the total footprint is estimated at about 216.78 kg CO2e. Each OSCAR model accounts for roughly 18–66 kg, compared with about 1.3–4.6 kg for each Wikipedia model. All ten ELMo models are published at oscar-corpus.com.
Cited by
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- Multilingual Sequence-to-Sequence Models for Hebrew NLP
- LCHAIM - Investigating Long Context Reasoning in Hebrew
- The Interplay of Variant, Size, and Task Type in Arabic Pre-trained Language Models
- Quality at a Glance: An Audit of Web-Crawled Multilingual Datasets
- HeBERT & HebEMO: a Hebrew BERT Model and a Tool for Polarity Analysis and Emotion Recognition
- AlephBERT: A Hebrew Large Pre-Trained Language Model to Start-off your Hebrew NLP Application With
- HeRo: RoBERTa and Longformer Hebrew Language Models
- OBELICS: An Open Web-Scale Filtered Dataset of Interleaved Image-Text Documents
- When Being Unseen from mBERT is just the Beginning: Handling New Languages With Multilingual Language Models
- CulturaX: A Cleaned, Enormous, and Multilingual Dataset for Large Language Models in 167 Languages
- ParaShoot: A Hebrew Question Answering Dataset
Cite
@inproceedings{suarez2020monolingual,
title = {{A Monolingual Approach to Contextualized Word Embeddings for Mid-Resource Languages}},
author = {Suárez, Pedro Javier Ortiz and Romary, Laurent and Sagot, Benoît},
booktitle = {Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics},
year = {2020},
doi = {10.18653/v1/2020.acl-main.156},
url = {https://doi.org/10.18653/v1/2020.acl-main.156}
}References
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