CARE: A Coverage-Aware Retrieval Ensemble for Isolated Sign Language Recognition

Nguyen Tu Nam, Hiroki Takahashi


Abstract
Isolated sign language recognition is commonly formulated as supervised classification, but this formulation is challenging when nearly every target gloss has only one labeled video. We study the Isolated Sign Language Recognition track of the WSLP 2026 Shared Task on Indian Sign Language Processing, a predominantly one-shot target setting with 4,398 training videos spanning 4,361 glosses, over 99% of which are singletons. We introduce CARE, a Coverage-Aware Retrieval Ensemble that augments a complete local visual dictionary with a CISLR reference bank covering a subset of the target vocabulary. A frozen Video-Swin encoder ranks all target labels locally, while frozen I3D and SignRep encoders provide external retrieval evidence for lexically matched labels. CARE estimates orthogonal Procrustes mappings from shared-class centroids, retains both raw and aligned representation geometries, and preserves external videos as individual nearest-neighbor references. Query-wise score standardization and a deterministic coverage mask restrict external evidence to supported labels. The method requires neither target-specific backbone fine-tuning nor a large-vocabulary classification head. CARE obtains 74.31%/76.15%/76.15% Top-1/5/10 accuracy on the WSLP 2026 validation split and 65.59%/67.11%/68.25% on the official test split. The 8.72% Top-1 gap warrants caution when interpreting performance on the small 109-query validation split used for model selection.
Anthology ID:
2026.wslp-1.14
Volume:
Proceedings of the Second Workshop on Sign Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Sanjeet Singh, Abhinav Joshi, Pokala Dattatreya, Keren Artiaga, Khushi Jaydeep Pujara, Tomáš Železný, Ivan Gruber, Jakub Honzík, Sabyasachi Kamila, Facundo Manuel Quiroga, Marek Hrúz, Mohammed Hasanuzzaman, Ashutosh Modi
Venues:
WSLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
141–146
Language:
URL:
https://aclanthology.org/2026.wslp-1.14/
DOI:
Bibkey:
Cite (ACL):
Nguyen Tu Nam and Hiroki Takahashi. 2026. CARE: A Coverage-Aware Retrieval Ensemble for Isolated Sign Language Recognition. In Proceedings of the Second Workshop on Sign Language Processing, pages 141–146, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
CARE: A Coverage-Aware Retrieval Ensemble for Isolated Sign Language Recognition (Nam & Takahashi, WSLP 2026)
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PDF:
https://aclanthology.org/2026.wslp-1.14.pdf