Design Space of Tree-Based Search
uses the document's own hierarchy
machine builds the hierarchy (summaries · learning)
score-based traversal
word overlap · semantic sim · 0 LLM calls per query
LLM-guided traversal
reads and reasons its way, per query
HiKEY
the only multimodal one
today's paper
TreeRAG
PageIndex
RDR2
trains the traversal
RAPTOR
MemWalker
score-based traversal
LLM-guided traversal
TIMELINE
MemWalker
arXiv 2023
RAPTOR
ICLR 2024
PageIndex
open-source 2025
TreeRAG
ACL Findings 2025
RDR2
EMNLP 2025
HiKEY
ACL 2026
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