Semi-supervised Fine-grained Approach for Arabic dialect detection task
Paper · 2020 · Nitin Nikamanth Appiah Balaji and Bharathi B
Summary
This paper describes the TRY NLP team's entry to the NADI 2020 shared task on Arabic dialect identification from tweets. The task has two fine-grained levels: 21 country labels and 100 province labels. The training data is small and heavily imbalanced, so the authors first compared several text representations, each topped with an added classification layer: TF-IDF, AraVec, multilingual BERT and an Arabic FastText model. FastText worked best with only the labelled data. Its subword pieces cope well with the many unfamiliar tokens in tweets, and an Arabic-specific pretrained version exists, while BERT is only available as a general multilingual model. The authors then added self-training. They downloaded the roughly 10 million unlabelled tweets provided as IDs, labelled them with the FastText model, kept only the most confident predictions, and retrained, repeating this several times. On the dev set this raised country-level macro F1 from 0.1890 to 0.2232. The work shows that cheap pseudo-labelling of in-domain raw text can help a low-resource, many-class task more than switching to a larger pretrained model.
Key points
- Data: 21,000 labelled training tweets, 4,957 dev and 5,000 test tweets. There were also 10 million unlabelled tweet IDs, and about 92% of those tweets could still be fetched through the Twitter API.
- Preprocessing kept only Arabic text, removing links, hashtags, numbers, English and special characters.
- Dev macro F1 at country level was TF-IDF 0.1522, AraVec 0.1159, multilingual BERT 0.1175, FastText 0.1890 and semi-supervised FastText 0.2232. At province level the same models scored 0.0442, 0.0213, 0.0275, 0.0437 and 0.0483.
- The FastText setup used Common Crawl and Wikipedia Arabic vectors of dimension 300 (CBOW, character n-grams of length 5, window 5, 10 negatives), loaded through the Magnitude library.
- On the test set, the submitted semi-supervised FastText model reached macro F1 0.2004 for country level and 0.0403 for province level. Confidence cut-offs of the top 1%, 5% and 10% were tried for selecting pseudo-labels.
Interesting ideas
- I1. Self-training adds only a thin top slice of the model's most confident predictions in each round (1/5/10%), rather than all pseudo-labels, which limits how much error leaks back into training.
- I2. With pseudo-labelling, country-level macro F1 rose while plain accuracy dipped slightly (0.3752 → 0.3674), so the gains landed on smaller classes that accuracy hides.
- I3. A plain TF-IDF model fitted on the task's own corpus beat AraVec and multilingual BERT, and roughly matched FastText at province level, which makes it a strong cheap reference point.
- I4. Character n-gram embeddings, plus a lookup that gives repeated unseen words a consistent vector, handle noisy social-media vocabulary that word-level models miss.
For Mova
How these ideas could serve Mova, our small open language model — its files, stages and tests:
- I1 (learn): Silver parses agreed by witness parsers could be added in small, high-agreement slices per round, with retraining between rounds, instead of in one large batch.
- I2 (learn): Evaluations should report per-class or macro scores next to overall accuracy, so that improvements or regressions on rare relations or labels stay visible.
- I3 (learn): A simple in-domain baseline can act as a negative control, so a costly new component counts as a win only if it clearly beats this baseline.
- I4 (tokens): Subword-based fallback features could stabilise tagging and lemma guesses for out-of-vocabulary or misspelled English words.
Fields, topics and concepts
📚 Shelves 4The field of science this work belongs to (OpenAlex fields).Computer Science · 16,667 worksArtificial Intelligence · 16,194 worksArts and Humanities · 16,039 worksLanguage and Linguistics · 15,891 works
🧭 Topics 2Research subjects and languages the work is about.Semitic languages · 2,908 worksMultilingual & cross-lingual NLP · 828 works
Cite
Cite as Nitin Nikamanth Appiah Balaji and Bharathi B. 2020. Semi-supervised Fine-grained Approach for Arabic dialect detection task. Proceedings of the Fifth Arabic Natural Language Processing Workshop.
@inproceedings{balaji2020semi,
title = {{Semi-supervised Fine-grained Approach for Arabic dialect detection task}},
author = {Nitin Nikamanth Appiah Balaji and Bharathi B},
booktitle = {Proceedings of the Fifth Arabic Natural Language Processing Workshop},
year = {2020},
url = {https://aclanthology.org/2020.wanlp-1.25/}
}References
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