Towards Benchmarking Old Church Slavonic Lemmatization

Usman Nawaz, Marianna Napolitano, Iris Karafillidis, Liliana Lo Presti, Marco Cascia


Abstract
Lemmatization is an important preprocessing step in Natural Language Processing (NLP); however, annotated resources for medieval languages such as Old Church Slavonic (OCS) are limited in scope, size, and diversity. This paper presents the annotated resources for OCS lemmatization, including annotation process, design choices and non-standard Unicode related issues. The annotated corpus is used to evaluate existing lemmatization tools (Stanza and UDPipe-2 models trained on the UD 2.12 treebank, and a dictionary-based approach) both in cross-dataset and on a corpus obtained by merging the new annotations with existing UD V2.12 OCS data. Pretrained models perform poorly (≈ 15–16%), below a dictionary baseline (≈ 38%), while retraining on the new data improves performance (up to ≈ 51%) and shows different cross-dataset generalization. Experiments in cross-dataset and on the combined corpus demonstrate that lemmatization performance depends strongly on dataset similarity, annotation conventions, and orthographic mismatch. Overall, the findings show the value of the newly annotated resources and the importance of extending OCS lemmatization benchmarks for historical Slavic NLP.
Anthology ID:
2026.brigap-1.9
Volume:
Proceedings of the Third Workshop on the Bridges and Gaps between Formal and Computational Linguistics (BriGap-3)
Month:
July
Year:
2026
Address:
Paris, France
Editors:
Timothée Bernard, Emmanuele Chersoni, Giulia Rambelli
Venues:
BriGap | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
82–93
Language:
URL:
https://preview.aclanthology.org/ingest-brigap/2026.brigap-1.9/
DOI:
Bibkey:
Cite (ACL):
Usman Nawaz, Marianna Napolitano, Iris Karafillidis, Liliana Lo Presti, and Marco Cascia. 2026. Towards Benchmarking Old Church Slavonic Lemmatization. In Proceedings of the Third Workshop on the Bridges and Gaps between Formal and Computational Linguistics (BriGap-3), pages 82–93, Paris, France. Association for Computational Linguistics.
Cite (Informal):
Towards Benchmarking Old Church Slavonic Lemmatization (Nawaz et al., BriGap 2026)
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PDF:
https://preview.aclanthology.org/ingest-brigap/2026.brigap-1.9.pdf