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BiCon-Gate: Consistency-Gated De-colloquialisation for Dialogue Fact-Checking

Paper · 2026 · Hyunkyung Park and Arkaitz Zubiaga

Summary

Dialogue fact-checking breaks down when response claims are informal. Contractions, missing punctuation, lowercase text and pronouns that point to earlier turns make claims weak retrieval queries and shaky hypotheses for the verifier. Rewriting a claim so it stands on its own can raise recall, but it risks semantic drift (for example, a pronoun mapped to the wrong entity), which damages verification. Park and Zubiaga study this IR–FV trade-off on the DialFact benchmark.

They build a cautious rewrite in cumulative stages: contraction expansion, punctuation restoration, true-casing, and pronoun resolution restricted to the claim itself. They compare it with a one-shot rewrite by a decoder LLM. BiCon-Gate scores each rewrite using bidirectional NLI entailment and contradiction plus embedding similarity. It keeps the rewrite only above a task-specific threshold and otherwise reverts to the original claim.

Surface normalisation proves largely neutral, while scoped pronoun rewriting helps document retrieval. Gating yields the best FV-only results (especially on SUPPORTS) and the best top-1 E2E scores. One-shot LLM rewrites often hurt verification. The work shows that conservative, controlled rewriting is a safer component for retrieve–verify pipelines.

Key points

  • Across DialFact, 42.1% of claims include one or more in-claim pronouns (39.7% of validation claims, 44.3% of test claims), which motivates the focus on in-claim anaphora.
  • The rewrite variants are cumulative: R1 adds apostrophes and expands contractions, R2 restores punctuation, R3 applies true-casing and R4 resolves in-scope pronouns. R5 is a single-pass de-colloquialisation by a decoder LLM.
  • The gate score is α·ent + β·sim + γ·(1 − cnt). It uses thresholds of τ_IR = 0.50 for retrieval and τ_FV = 0.70 for verification, falling back to R0 below them.
  • Effects are separated through IR-only, FV-only (gold evidence) and E2E evaluations. The E2E setting uses a fixed BM25 → E5 → BGE-CE retriever stack and a single top-1 Wikipedia passage as evidence.
  • Ungated coreference rewrites can improve retrieval yet lower E2E verification, echoing earlier findings by Chamoun et al. (2023). The study is limited to English DialFact, and the thresholds may need retuning under distribution shift.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Institutions

 Fields, topics and concepts

Cite

Cite as Hyunkyung Park and Arkaitz Zubiaga. 2026. BiCon-Gate: Consistency-Gated De-colloquialisation for Dialogue Fact-Checking. Proceedings of the Ninth Fact Extraction and VERification Workshop (FEVER).

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/2026.fever-1.5

@inproceedings{park2026bicon,
  title = {{BiCon-Gate: Consistency-Gated De-colloquialisation for Dialogue Fact-Checking}},
  author = {Hyunkyung Park and Arkaitz Zubiaga},
  booktitle = {Proceedings of the Ninth Fact Extraction and VERification Workshop (FEVER)},
  year = {2026},
  doi = {10.18653/v1/2026.fever-1.5},
  url = {https://doi.org/10.18653/v1/2026.fever-1.5}
}

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