Three-Tier Indexing and Semantic Chunking for RAG
bigaiguy · x · 2026-07-11
This reply continues discussing two RAG techniques:
- Hierarchical Indexing
- The architecture uses three layers instead of a single index:
- Document summary index
- Standard chunk index
- Sentence-level fact index
- The router selects the layer based on the question type: broad questions go to summaries, specific facts go to sentences.
- Semantic Boundary Chunking
- Instead of hard-splitting by character count, split by the completion of a "single idea/argument/step."
- Fixed-length splitting often breaks sentences or concepts, causing the model to retrieve only half a concept and hallucinate the rest.
- The author notes that their library finds natural semantic breakpoints before splitting, which improved retrieval accuracy on internal benchmarks by 34%.
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