RELOOP: Recursive Retrieval with Multi-Hop Reasoner and Planners for Heterogeneous QA

Ruiyi Yang, Hao Xue, Imran Razzak, Hakim Hacid, Flora D. Salim


Abstract
Retrieval-augmented generation (RAG) remains challenging for multi-hop question answering when supporting evidence is distributed across heterogeneous sources, including text, tables, and knowledge graphs (KGs). Existing systems often rely on modality-specific retrieval pipelines or uncontrolled iterative search, making it difficult to preserve source structure while maintaining efficient evidence acquisition. We present **RELOOP**, a structure-aware retrieval framework built on **Hierarchical Sequence (HSEQ)**, a reversible representation that maps heterogeneous sources into provenance-preserving typed segments with lightweight structural links. Operating on this unified evidence interface, a lightweight iterator selects and expands candidate evidence through structure-respecting actions, while an explicit sufficiency signal determines when the accumulated evidence is adequate for answering. A head module then synthesizes the final answer from a compact, canonicalized evidence package, with an optional refinement step when inconsistent evidence is detected. Experiments on HotpotQA, HybridQA, TAT-QA, and MetaQA show that RELOOP consistently improves answer quality over strong single-pass and iterative RAG baselines while requiring substantially fewer retrieval steps than graph-expansion approaches. These results suggest that a reversible, structure-aware evidence interface provides an effective foundation for accurate and budget-controlled retrieval across heterogeneous QA settings.
Anthology ID:
2026.findings-emnlp.1736
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
Note:
Pages:
37120–37138
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1736/
DOI:
Bibkey:
Cite (ACL):
Ruiyi Yang, Hao Xue, Imran Razzak, Hakim Hacid, and Flora D. Salim. 2026. RELOOP: Recursive Retrieval with Multi-Hop Reasoner and Planners for Heterogeneous QA. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 37120–37138, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
RELOOP: Recursive Retrieval with Multi-Hop Reasoner and Planners for Heterogeneous QA (Yang et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1736.pdf