Step-by-Step Mastery: Enhancing Soft Constraint Following Ability of Large Language Models

Qingyu Ren, Jie Zeng, Qianyu He, Jiaqing Liang, Yanghua Xiao, Weikang Zhou, Zeye Sun, Fei Yu


Abstract
It is crucial for large language models (LLMs) to follow instructions that involve multiple constraints. In real-world scenarios, user instructions often contain soft constraints, which are semantically related and cannot be rule-based verified, posing challenges for LLMs. To enhance the soft constraint following ability of LLMs, we initially design a pipeline to construct datasets with high-quality outputs for instructions containing soft constraints automatically. Additionally, to fully utilize the positive and negative samples generated during the data construction process, we choose Direct Preference Optimization (DPO) as the training method. Furthermore, taking into account the difficulty of soft constraints indicated by the number of constraints, we design a curriculum learning training paradigm based on the constraint quantity. We experimentally evaluate the effectiveness of our methods in improving LLMs’ soft constraint following ability and analyze the factors driving the improvements.
Anthology ID:
2025.findings-acl.1004
Volume:
Findings of the Association for Computational Linguistics: ACL 2025
Month:
July
Year:
2025
Address:
Vienna, Austria
Editors:
Wanxiang Che, Joyce Nabende, Ekaterina Shutova, Mohammad Taher Pilehvar
Venues:
Findings | WS
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Publisher:
Association for Computational Linguistics
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Pages:
19581–19596
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URL:
https://preview.aclanthology.org/ingestion-acl-25/2025.findings-acl.1004/
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Cite (ACL):
Qingyu Ren, Jie Zeng, Qianyu He, Jiaqing Liang, Yanghua Xiao, Weikang Zhou, Zeye Sun, and Fei Yu. 2025. Step-by-Step Mastery: Enhancing Soft Constraint Following Ability of Large Language Models. In Findings of the Association for Computational Linguistics: ACL 2025, pages 19581–19596, Vienna, Austria. Association for Computational Linguistics.
Cite (Informal):
Step-by-Step Mastery: Enhancing Soft Constraint Following Ability of Large Language Models (Ren et al., Findings 2025)
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https://preview.aclanthology.org/ingestion-acl-25/2025.findings-acl.1004.pdf