KASHAF: A Hierarchical Resource and Pipeline for Arabic Interpretable Semantic Textual Similarity

Fahad AlGhamdi, Abdelati Hawwari, Abdulrahman Alosaimy, Rawan Nasser Almatham, Asma Al Wazrah


Abstract
We introduce KASHAF, to our knowledge the first interpretable Semantic Textual Similarity (iSTS) resource and end-to-end system for Arabic: a corpus of 7,811 human-annotated sentence pairs (inter-annotator κ=0.83κ= 0.83 κ=0.83 on a doubly-annotated subset) under a three-level hierarchical schema (sentence, phrase, and word), together with a modular pipeline that produces this layered analysis plus a composite similarity score, the KASHAF Hierarchical Similarity Score (KHSS), calibrated to the ordinal SEM scale. On a held-out cross-batch test split (1,002 pairs, disjoint from training and dev), KASHAF reaches macro-F1 =0.659= 0.659 =0.659 (±0.016±0.016 ±0.016, 5 seeds) and Spearman ρ=0.6715ρ= 0.6715 ρ=0.6715; a rule-based antonym/negation polarity gate provides an empirical score-capping rule for high-similarity contradictions, and the MARBERTv2 backbone leads three alternative Arabic encoders. As an off-the-shelf diagnostic rather than a fine-tuned comparison, four contemporary LLMs under matched prompting reach at most macro-F1 0.215 (standard prompting) and 0.336 (chain-of-thought), a 32–44-point gap that reflects systematic over-prediction of SEM-PARA at the expense of the dominant SEM-PARTIAL class. We release the schema, guidelines, code, models, and a reproducibility pipeline; the corpus is available from KSAA on request.
Anthology ID:
2026.arabicnlp-main.31
Volume:
Proceedings of The Fourth Arabic Natural Language Processing Conference
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:
444–461
Language:
URL:
https://aclanthology.org/2026.arabicnlp-main.31/
DOI:
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Cite (ACL):
Fahad AlGhamdi, Abdelati Hawwari, Abdulrahman Alosaimy, Rawan Nasser Almatham, and Asma Al Wazrah. 2026. KASHAF: A Hierarchical Resource and Pipeline for Arabic Interpretable Semantic Textual Similarity. In Proceedings of The Fourth Arabic Natural Language Processing Conference, pages 444–461, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
KASHAF: A Hierarchical Resource and Pipeline for Arabic Interpretable Semantic Textual Similarity (AlGhamdi et al., ArabicNLP 2026)
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PDF:
https://aclanthology.org/2026.arabicnlp-main.31.pdf