NUST Alpha at RIRAG 2025: Fusion RAG for Bridging Lexical and Semantic Retrieval and Question Answering

Muhammad Rouhan Faisal, Muhammad Abdullah, Faizyaab Ali Shah, Shalina Riaz, Huma Ameer, Seemab Latif, Mehwish Fatima


Abstract
NUST Alpha participates in the Regulatory Information Retrieval and Answer Generation (RIRAG) shared task. We propose FusionRAG that combines OpenAI embeddings, BM25, FAISS, and Rank-Fusion to improve information retrieval and answer generation. We also explores multiple variants of our model to assess the impact of each component in overall performance. FusionRAG strength comes from our rank fusion and filter strategy. Rank fusion integrates semantic and lexical relevance scores to optimize retrieval accuracy and result diversity, and Filter mechanism remove irrelevant passages before answer generation. Our experiments demonstrate that FusionRAG offers a robust and scalable solution for automating the analysis of regulatory documents, improving compliance efficiency, and mitigating associated risks. We further conduct an error analysis to explore the limitations of our model’s performance.
Anthology ID:
2025.regnlp-1.12
Volume:
Proceedings of the 1st Regulatory NLP Workshop (RegNLP 2025)
Month:
January
Year:
2025
Address:
Abu Dhabi, UAE
Editors:
Tuba Gokhan, Kexin Wang, Iryna Gurevych, Ted Briscoe
Venues:
RegNLP | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
79–84
Language:
URL:
https://aclanthology.org/2025.regnlp-1.12/
DOI:
Bibkey:
Cite (ACL):
Muhammad Rouhan Faisal, Muhammad Abdullah, Faizyaab Ali Shah, Shalina Riaz, Huma Ameer, Seemab Latif, and Mehwish Fatima. 2025. NUST Alpha at RIRAG 2025: Fusion RAG for Bridging Lexical and Semantic Retrieval and Question Answering. In Proceedings of the 1st Regulatory NLP Workshop (RegNLP 2025), pages 79–84, Abu Dhabi, UAE. Association for Computational Linguistics.
Cite (Informal):
NUST Alpha at RIRAG 2025: Fusion RAG for Bridging Lexical and Semantic Retrieval and Question Answering (Faisal et al., RegNLP 2025)
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https://aclanthology.org/2025.regnlp-1.12.pdf