Source-Grounded Semantic Reinforcement Learning for Low-Resource Target-Language Generation

Zeli Su, Ziyin Zhang, Pan Zewei, Zhou Liu, Dingcheng Huang, Dehan Li, Zhankai Xu, Longfei Zheng, Xiaolu Zhang, Jun Zhou, Wentao Zhang


Abstract
Low-resource target-language generation is often limited by scarce parallel data, while high-resource source-language monolingual data is abundant but difficult to use with standard supervised fine-tuning. We propose Source-Grounded Semantic Reinforcement Learning (SG-SRL), a resource-utilization framework that converts source-language monolingual data into cross-lingual semantic supervision. SG-SRL performs reference-free reinforcement learning (RL) on source-language data with a cross-lingual semantic reward, followed by lightweight supervised recovery. Although direct reward optimization induces verbosity-based reward hacking, recovery restores fluency, conciseness, and task format without erasing the learned semantic alignment. On Chinese-to-Thai generation, SG-SRL outperforms cold-start SFT, source-only continued pretraining, and synthetic-data SFT; human preference and training-independent metrics corroborate the gains. Recovery ablations further show that semantic retention and form restoration are jointly controlled by recovery data and intensity. An in-domain Chinese-to-Tibetan experiment shows that the reward interface can use a contrastively trained encoder when a capable multilingual reranker is unavailable, while also delimiting the framework’s dependence on reward-model discrimination.
Anthology ID:
2026.emnlp-main.674
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
15521–15534
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URL:
https://aclanthology.org/2026.emnlp-main.674/
DOI:
Bibkey:
Cite (ACL):
Zeli Su, Ziyin Zhang, Pan Zewei, Zhou Liu, Dingcheng Huang, Dehan Li, Zhankai Xu, Longfei Zheng, Xiaolu Zhang, Jun Zhou, and Wentao Zhang. 2026. Source-Grounded Semantic Reinforcement Learning for Low-Resource Target-Language Generation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 15521–15534, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Source-Grounded Semantic Reinforcement Learning for Low-Resource Target-Language Generation (Su et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.674.pdf