Itgan at AraSeg Shared Task 2026: Diversify, Don’t Curate – Learned Ensemble Combination for Arabic Sentence Segmentation

Ibrahim Almajai


Abstract
We describe our submissions to the four subtasks of the AraSeg 2026 shared task in both tracks. Our components are conventional word-level boundary taggers, and our contribution is a measurement of what combining them is worth. Averaging 21 members gains +0.89 F1 over the best single model, and replacing the uniform probability average with a learned logistic combiner adds a further +0.23 (+1.12 in total), reaching significance only on the two subtasks that lack punctuation. Both are smaller than the encoder swap (+1.82). What the combiner buys is freedom from curation. Added to the base encoder, each of six different pretrained encoders helps under the combiner (+0.12 to +0.72, mean +0.34), whereas under averaging three of the six are harmful, by as much as 0.62. Another seed of an existing encoder is worth nothing under either rule; members should therefore be diversified rather than curated, provided the weights are learned. We also report three null results for inference-time structure, including a semi-Markov CRF whose failure we trace to a length prior that is uninformative at corpus level. Our closed-track systems placed fifth and seventh where ranked. In the open track, pretraining on 3.2M tokens of silver boundaries from Arabic Wikipedia before fine-tuning on the gold training split is worth +0.58 F1, and two of the closed-track findings reproduce on that external data.
Anthology ID:
2026.arabicnlp-sharedtasks.122
Volume:
Proceedings of The Fourth Arabic Natural Language Processing Conference: Shared Tasks
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Muhammad Abdul-Mageed, Tamer Elsayed, Houda Bouamor, Samhaa El-Beltagy, Hend Al-Khalifa, Ahmed Abdelali, AbdelRahim Elmadany, Abdellah El Mekki, Kareem Darwish, Sakhar Alkhereyf, Hamzah Luqman, Salam Khalifa, Samar Magdy, Zaid Alyafeai, Injy Hamed, Wajdi Zaghouani, Imed Zitouni
Venue:
ArabicNLP
SIG:
SIGARAB
Publisher:
Association for Computational Linguistics
Note:
Pages:
995–1003
Language:
URL:
https://aclanthology.org/2026.arabicnlp-sharedtasks.122/
DOI:
Bibkey:
Cite (ACL):
Ibrahim Almajai. 2026. Itgan at AraSeg Shared Task 2026: Diversify, Don’t Curate – Learned Ensemble Combination for Arabic Sentence Segmentation. In Proceedings of The Fourth Arabic Natural Language Processing Conference: Shared Tasks, pages 995–1003, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Itgan at AraSeg Shared Task 2026: Diversify, Don’t Curate – Learned Ensemble Combination for Arabic Sentence Segmentation (Almajai, ArabicNLP 2026)
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PDF:
https://aclanthology.org/2026.arabicnlp-sharedtasks.122.pdf