HIRAG: Hierarchical-Thought Instruction-Tuning Retrieval-Augmented Generation

Yihan Jiao, Zhehao Tan, Dan Yang, Duolin Sun, Jie Feng, Yue Shen, Jian Wang, Peng Wei


Abstract
Retrieval-augmented generation (RAG) has become a fundamental paradigm for addressing the challenges faced by large language models in handling real-time information and domain-specific problems. Traditional RAG systems primarily rely on the in-context learning (ICL) capabilities of the large language model itself. Still, in-depth research on the specific capabilities needed by the RAG generation model is lacking, leading to challenges with inconsistent document quality and retrieval system imperfections. Even the limited studies that fine-tune RAG generative models often lack a granular focus on RAG tasks or a deeper utilization of chain-of-thought processes. To address this, we propose that RAG models should possess three progressively hierarchical abilities (1) Filtering: the ability to select relevant information; (2) Combination: the ability to combine semantic information across paragraphs; and (3) RAG-specific reasoning: the ability to further process external knowledge using internal knowledge. Thus, we introduce our new RAG instruction fine-tuning method, Hierarchical-Thought Instruction-Tuning Retrieval-Augmented Generation (HIRAG) incorporates a “think before answering” strategy. This method enhances the model’s open-book examination capability by utilizing multi-level progressive chain-of-thought. Experiments show that the HIRAG training strategy significantly improves the model’s performance on datasets such as RGB, PopQA, MuSiQue, HotpotQA, and PubmedQA.
Anthology ID:
2025.findings-emnlp.274
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2025
Month:
November
Year:
2025
Address:
Suzhou, China
Editors:
Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
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Pages:
5111–5130
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URL:
https://aclanthology.org/2025.findings-emnlp.274/
DOI:
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Cite (ACL):
Yihan Jiao, Zhehao Tan, Dan Yang, Duolin Sun, Jie Feng, Yue Shen, Jian Wang, and Peng Wei. 2025. HIRAG: Hierarchical-Thought Instruction-Tuning Retrieval-Augmented Generation. In Findings of the Association for Computational Linguistics: EMNLP 2025, pages 5111–5130, Suzhou, China. Association for Computational Linguistics.
Cite (Informal):
HIRAG: Hierarchical-Thought Instruction-Tuning Retrieval-Augmented Generation (Jiao et al., Findings 2025)
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https://aclanthology.org/2025.findings-emnlp.274.pdf
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