Wasl at KnowledgeGraphEval 2026: Multi-Head Nested BIO Tagging and Constraint-Aware Relation Classification for Arabic Knowledge Graph Construction

Salah Abdo, Faisal Muhammad Adam


Abstract
We describe Team Wasl’s systems for the KnowledgeGraphEval 2026 shared task at ArabicNLP 2026, which decomposes Arabic knowledge-graph construction into two evaluated stages: nested NER under domain shift and relation extraction between given mentions. For Subtask 1 (AdaptNER), we train a multi-head BIO tagger (one three-way O/B/I head per entity type over a shared pretrained Arabic encoder) on Wojood and combine three random seeds by span-level majority vote. For Subtask 2, forced-choice classification over the 40 WojoodRelations relation types, we fine-tune a typed-marker classifier with type-constraint decoding, ensembling five grouped folds by logit averaging. Our submissions scored 0.7483 micro-F1 on AdaptNER’s blind Konooz slice (ten unseen domains), 4th of the eight officially ranked teams and 11.8 points above the official baseline, and 0.9571 micro-F1 on relation extraction with the no-relation class masked at decoding, 2nd at the results release; re-scored by the organizers over all 41 classes, the same ensemble reaches 0.9328, 4th in the organizers’ final ranking. We analyze where the 18.6-point domain-shift tax on NER falls: chiefly on recall. We further show that type-constraint decoding and ensembling are partially redundant (+0.9 points on a single RE model, +0.1 on the ensemble) and that the surviving errors share an argument-type signature that no type constraint can separate.
Anthology ID:
2026.arabicnlp-sharedtasks.153
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:
1219–1226
Language:
URL:
https://aclanthology.org/2026.arabicnlp-sharedtasks.153/
DOI:
Bibkey:
Cite (ACL):
Salah Abdo and Faisal Muhammad Adam. 2026. Wasl at KnowledgeGraphEval 2026: Multi-Head Nested BIO Tagging and Constraint-Aware Relation Classification for Arabic Knowledge Graph Construction. In Proceedings of The Fourth Arabic Natural Language Processing Conference: Shared Tasks, pages 1219–1226, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Wasl at KnowledgeGraphEval 2026: Multi-Head Nested BIO Tagging and Constraint-Aware Relation Classification for Arabic Knowledge Graph Construction (Abdo & Adam, ArabicNLP 2026)
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PDF:
https://aclanthology.org/2026.arabicnlp-sharedtasks.153.pdf