Rank4Gen: RAG-Preference-Aligned Document Set Selection and Ranking

Yongqi Fan, Yuxiang Chu, Zhentao Xia, Xiaoyang Chen, Jie Liu, Haijin Liang, Jin Ma, Ben He, Yingfei Sun, Jie Zhai, Dezhi Ye, Tong Ruan


Abstract
In the RAG paradigm, document ranking determines the evidence available to downstream generators. Through controlled analysis, we identify two phenomena underexplored by existing rankers: (i) downstream response quality depends not only on relevance but also on the composition and ordering of selected documents, and (ii) such preferences differ systematically across generators. However, existing rankers are trained purely on query–document relevance, leaving both phenomena unmodeled. To close this gap, we construct PRISM, a bilingual preference-aligned dataset built through a four-stage pipeline that compresses the combinatorial subset-and-ordering space by roughly four orders of magnitude and produces response-quality preference supervision conditioned on seven downstream generators. On a 13k-query subset of PRISM, we train Rank4Gen, a generator-aware ranker that performs joint document set selection and ordering. Experiments on five challenging RAG benchmarks show that Rank4Gen improves downstream QA quality on most evaluated generators, with per-generator F1 gains of up to +2.08 over the strongest set-selection baseline. Code is available at https://github.com/JOHNNY-fans/Rank4Gen.
Anthology ID:
2026.findings-emnlp.942
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
19847–19875
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URL:
https://aclanthology.org/2026.findings-emnlp.942/
DOI:
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Cite (ACL):
Yongqi Fan, Yuxiang Chu, Zhentao Xia, Xiaoyang Chen, Jie Liu, Haijin Liang, Jin Ma, Ben He, Yingfei Sun, Jie Zhai, Dezhi Ye, and Tong Ruan. 2026. Rank4Gen: RAG-Preference-Aligned Document Set Selection and Ranking. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 19847–19875, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Rank4Gen: RAG-Preference-Aligned Document Set Selection and Ranking (Fan et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.942.pdf