@inproceedings{raya-rios-etal-2026-iimas,
title = "{IIMAS}-{RAG} at {S}em{E}val-2026 Task 8: Hybrid Sparse-Dense Retrieval and Answerability-Conditioned Generation for Multi-Turn {RAG}",
author = "Raya-Rios, Vania and
Gomez-Adorno, Helena and
Hecht, Leon and
V{\'a}zquez-Osorio, Pedro and
Fabi{\'a}n-Sandoval, Erick and
V{\'a}zquez-Osorio, Jes{\'u}s and
Hern{\'a}ndez-Bustamante, Diego",
editor = "Kochmar, Ekaterina and
Ghosh, Debanjan and
North, Kai and
Komachi, Mamoru",
booktitle = "Proceedings of the 20th {I}nternational {W}orkshop on {S}emantic {E}valuation (2026)",
month = jul,
year = "2026",
address = "San Diego, California, USA",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.semeval-1.345/",
pages = "2744--2753",
ISBN = "979-8-89176-414-9",
abstract = "This paper presents IIMAS-RAG, our system for SemEval-2026 Task 8 on evaluating multi-turn retrieval-augmented generation. Our approach combines LLM-based query rewriting, hybrid sparse-dense retrieval with SPLADE and Voyage-3-large fused via Reciprocal Rank Fusion, and answerability-conditioned generation with GPT-4.1. The system ranked 4th out of 38 teams in Subtask A (Retrieval) and 13th out of 29 teams in Subtask C (Full RAG). Our results show that query rewriting is the most impactful retrieval component, while generation remains challenging in low-context and partially answerable scenarios."
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<abstract>This paper presents IIMAS-RAG, our system for SemEval-2026 Task 8 on evaluating multi-turn retrieval-augmented generation. Our approach combines LLM-based query rewriting, hybrid sparse-dense retrieval with SPLADE and Voyage-3-large fused via Reciprocal Rank Fusion, and answerability-conditioned generation with GPT-4.1. The system ranked 4th out of 38 teams in Subtask A (Retrieval) and 13th out of 29 teams in Subtask C (Full RAG). Our results show that query rewriting is the most impactful retrieval component, while generation remains challenging in low-context and partially answerable scenarios.</abstract>
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%0 Conference Proceedings
%T IIMAS-RAG at SemEval-2026 Task 8: Hybrid Sparse-Dense Retrieval and Answerability-Conditioned Generation for Multi-Turn RAG
%A Raya-Rios, Vania
%A Gomez-Adorno, Helena
%A Hecht, Leon
%A Vázquez-Osorio, Pedro
%A Fabián-Sandoval, Erick
%A Vázquez-Osorio, Jesús
%A Hernández-Bustamante, Diego
%Y Kochmar, Ekaterina
%Y Ghosh, Debanjan
%Y North, Kai
%Y Komachi, Mamoru
%S Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
%D 2026
%8 July
%I Association for Computational Linguistics
%C San Diego, California, USA
%@ 979-8-89176-414-9
%F raya-rios-etal-2026-iimas
%X This paper presents IIMAS-RAG, our system for SemEval-2026 Task 8 on evaluating multi-turn retrieval-augmented generation. Our approach combines LLM-based query rewriting, hybrid sparse-dense retrieval with SPLADE and Voyage-3-large fused via Reciprocal Rank Fusion, and answerability-conditioned generation with GPT-4.1. The system ranked 4th out of 38 teams in Subtask A (Retrieval) and 13th out of 29 teams in Subtask C (Full RAG). Our results show that query rewriting is the most impactful retrieval component, while generation remains challenging in low-context and partially answerable scenarios.
%U https://aclanthology.org/2026.semeval-1.345/
%P 2744-2753
Markdown (Informal)
[IIMAS-RAG at SemEval-2026 Task 8: Hybrid Sparse-Dense Retrieval and Answerability-Conditioned Generation for Multi-Turn RAG](https://aclanthology.org/2026.semeval-1.345/) (Raya-Rios et al., SemEval 2026)
ACL
- Vania Raya-Rios, Helena Gomez-Adorno, Leon Hecht, Pedro Vázquez-Osorio, Erick Fabián-Sandoval, Jesús Vázquez-Osorio, and Diego Hernández-Bustamante. 2026. IIMAS-RAG at SemEval-2026 Task 8: Hybrid Sparse-Dense Retrieval and Answerability-Conditioned Generation for Multi-Turn RAG. In Proceedings of the 20th International Workshop on Semantic Evaluation (2026), pages 2744–2753, San Diego, California, USA. Association for Computational Linguistics.