From Topical Relevance to Answerability: Entailment Distillation for Conversational Retrieval

Shuai Qin, Guojia An, Weikang Guo, Pei Ke, Jiwei Wei, Yang Yang, Jie Zou


Abstract
Existing conversational retrievers commonly treat topical relevance as a proxy for answerability. However, a passage that closely matches the dialogue context is not necessarily the one that supports the correct answer. We identify this mismatch as a systematic answerability gap. To address this issue, we propose CLEAR, a framework that shifts conversational retrieval from topical relevance to answerability. The core of CLEAR is entailment distillation, which transfers answer-passage entailment supervision into a cross-encoder reranker so that the reranker discriminates answer-supporting passages from topical distractors at inference time, without requiring answers. CLEAR is complemented by a passage-centric abductive recall module that brings low-similarity yet answerable passages into the candidate pool by inferring answerable queries from passages with an LLM. Across TopiOCQA, QReCC, and out-of-domain TREC CAsT datasets, CLEAR consistently improves top-ranked precision over strong query-rewriting and dense-retrieval baselines, with the largest gains observed in conversations involving heavier topical noise. Moreover, applying our reranker on top of an LLM-driven query rewriter yields further gains.
Anthology ID:
2026.findings-emnlp.802
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
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SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
16989–17003
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URL:
https://aclanthology.org/2026.findings-emnlp.802/
DOI:
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Cite (ACL):
Shuai Qin, Guojia An, Weikang Guo, Pei Ke, Jiwei Wei, Yang Yang, and Jie Zou. 2026. From Topical Relevance to Answerability: Entailment Distillation for Conversational Retrieval. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 16989–17003, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
From Topical Relevance to Answerability: Entailment Distillation for Conversational Retrieval (Qin et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.802.pdf