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ToR-RAG: A Tree-of-Retrieval-based Retrieval-Augmented Generation for Complex Question Processing

  • Journal of The Korea Society of Computer and Information
  • Abbr : JKSCI
  • 2025, 30(10), pp.23~31
  • Publisher : The Korean Society Of Computer And Information
  • Research Area : Engineering > Computer Science
  • Received : September 11, 2025
  • Accepted : October 1, 2025
  • Published : October 31, 2025

Hee-Kyong Yoo 1 Nammee Moon 1

1호서대학교

Accredited

ABSTRACT

Large Language Models have advanced natural language understanding, yet remain limited in handling complex multi-hop queries requiring integration across multiple documents. Traditional Retrieval-Augmented Generation adopts a linear query-retrieval-generation pipeline, which often causes error propagation, incomplete evidence coverage, and reduced reliability. To overcome these issues, this study proposes a Tree-of-Retrieval based RAG (ToR-RAG). ToR-RAG decomposes queries into binary sub-queries via LLM prompting, performs retrieval and partial answer generation at each branch, and evaluates outputs using an LLM-as-a-Judge module. Branches below a quality threshold are pruned, ensuring efficiency. An MMR-based retrieval strategy (λ=0.75) with top-k=5 selection balances relevance and diversity. Experiments on the MultiHop-RAG dataset show that ToR-RAG improves Exact Match by +6.42 and F1 by +6.04 compared to Non-RAG, Native-RAG, and CoR-RAG. Performance peaked at Depth=3, while Depth=4 caused degradation from excessive branching and token usage. These results demonstrate that ToR-RAG enhances both accuracy and reliability in multi-hop reasoning, suggesting applicability in domains such as policy analysis, medical decision-making, and financial risk assessment.

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