uva-irlab-conv at SemEval-2026 Task 8: Multi-Turn RAG with Learned Sparse Retrieval and Listwise Reranking

Simon Lupart, Kidist Mekonnen, Zahra Abbasiantaeb, Mohammad Aliannejadi


Abstract
This report describes our participation in SemEval-2026 Task 8 on multi-turn retrieval and question answering. The task evaluates conversational systems across four domains (finance, cloud documentation, government, Wikipedia), and includes unanswerable queries where the available collection does not contain sufficient evidence to produce a complete response. We propose a multi-turn retrieval-augmented generation pipeline that combines learned sparse retrieval with LLM–based reranking and generation. Using sparse retrieval as the primary retrieval method, we leverage its strong generalization across domains. In addition, we make use of the long-context capabilities of LLMs for conversational query rewriting, pointwise and listwise reranking, and generating the final response, each conditioned on the full conversational history. This multi-step design enables effective integration of conversational context throughout retrieval and generation, improving robustness across domains.
Anthology ID:
2026.semeval-1.373
Volume:
Proceedings of the 20th International Workshop on Semantic Evaluation (2026)
Month:
July
Year:
2026
Address:
San Diego, California, USA
Editors:
Ekaterina Kochmar, Debanjan Ghosh, Kai North, Mamoru Komachi
Venues:
SemEval | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
2972–2980
Language:
URL:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.373/
DOI:
Bibkey:
Cite (ACL):
Simon Lupart, Kidist Mekonnen, Zahra Abbasiantaeb, and Mohammad Aliannejadi. 2026. uva-irlab-conv at SemEval-2026 Task 8: Multi-Turn RAG with Learned Sparse Retrieval and Listwise Reranking. In Proceedings of the 20th International Workshop on Semantic Evaluation (2026), pages 2972–2980, San Diego, California, USA. Association for Computational Linguistics.
Cite (Informal):
uva-irlab-conv at SemEval-2026 Task 8: Multi-Turn RAG with Learned Sparse Retrieval and Listwise Reranking (Lupart et al., SemEval 2026)
Copy Citation:
PDF:
https://preview.aclanthology.org/ingest-acl-workshops/2026.semeval-1.373.pdf
Supplementarymaterial:
 2026.semeval-1.373.SupplementaryMaterial.zip