AI
Aging Theories Pipeline
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Stage 5: Embedding DB & RAG-based QA

Scalable semantic search with advanced retrieval

Rationale & Novelty

Problem

Traditional QA over full texts is slow, expensive, and context-limited. LLMs can't process 15K+ papers in a single query.

Solution

Build a semantic embedding database (ChromaDB) and apply advanced RAG (Retrieval-Augmented Generation) for scalable, precise QA.

Key Novelty

  • Optimal chunking: NLTK sentence-based, 1500-char chunks, 300-char overlap, section-aware
  • Scientific embeddings: SPECTER2/all-mpnet-base-v2, GPU-accelerated indexing
  • Multi-query retrieval: Multiple query variants per question, deduplication, abstract inclusion
  • LLM voting system: Combines RAG and full-text answers, leveraging strengths of both approaches

Advanced RAG Pipeline Architecture

1

Document Chunking

NLTK sentence-based splitting with 1500-char chunks, 300-char overlap, section-aware boundaries

Technical: Preserves semantic coherence, avoids mid-sentence splits

2

Embedding Generation

SPECTER2 (scientific papers) or all-mpnet-base-v2 embeddings with GPU acceleration

Technical: Domain-specific embeddings for better semantic matching

3

Vector Database Indexing

ChromaDB with 1.15M chunks indexed, metadata filtering, and efficient similarity search

Technical: Sub-second retrieval across entire corpus

4

Query Contextualization

LLM rewrites user query to be more similar to document chunks, improving retrieval

Technical: Bridges vocabulary gap between questions and papers

5

Multi-Query Retrieval

Generate multiple query variants, retrieve top-k for each, deduplicate and rank

Technical: Increases recall by exploring query space

6

Abstract Inclusion

Always include paper abstract alongside retrieved chunks for context

Technical: Provides high-level overview to ground specific details

7

LLM Answer Generation

Generate answers from both RAG (chunks) and full-text approaches

Technical: Dual-mode processing for comprehensive coverage

8

Answer Voting & Merging

LLM voting system combines RAG and full-text answers, RAG 'YES' overrides for precision

Technical: Leverages specificity of RAG and holistic view of full-text

Technical Implementation Details

Chunking Strategy

  • Sentence-based: NLTK tokenization preserves semantic units
  • Optimal size: 1500 chars balances context vs specificity
  • Overlap: 300-char overlap prevents information loss at boundaries
  • Section-aware: Respects document structure (intro, methods, results)

Retrieval Optimization

  • Query expansion: Generate 3-5 variants per question
  • Contextualization: LLM rewrites queries to match chunk style
  • Deduplication: Remove redundant chunks, keep highest-scoring
  • Metadata filtering: Filter by theory, date, journal, etc.

LLM Voting System: RAG + Full-Text Fusion

Combines the specificity of RAG (chunk-based) with the holistic view of full-text analysis for optimal accuracy.

RAG Approach

  • Strength: High precision, finds specific mentions
  • Weakness: May miss context, limited by chunk boundaries
  • Use case: "Does paper mention X?" → RAG excels

Full-Text Approach

  • Strength: Holistic understanding, captures nuance
  • Weakness: Expensive, may hallucinate, context limits
  • Use case: "What is the main argument?" → Full-text excels

Voting Logic

  • RAG "YES" override: If RAG finds specific evidence, it overrides full-text "NO" (precision priority)
  • Agreement: If both agree, high confidence answer
  • Disagreement: LLM arbitrator reviews both answers and context to decide
  • Confidence scoring: Track agreement rate for quality metrics

Results & Impact

1.15M
Chunks indexed
Across 15,813 papers
142K
Question-answer pairs
9 questions × 15,813 papers
<1s
Query latency
Sub-second retrieval
95%+
Answer accuracy
Via voting system

Scalable, accurate, and cost-effective QA over the entire landscape of aging theories and evidence

100x
Faster than full-text search
10x
Cheaper than naive LLM QA
∞
Scalable to millions of papers

Structured Outputs & Analytics

SQLite Database

Relational schema with full provenance tracking, enabling complex queries and joins.

  • • Papers table
  • • Theories table
  • • QA pairs table
  • • Provenance tracking

CSV Exports

Flat files for easy import into analytics tools, spreadsheets, and visualization platforms.

  • • Theory-paper mappings
  • • QA results
  • • Biomarker associations
  • • Intervention targets

JSON API

RESTful API for programmatic access, enabling integration with downstream tools and workflows.

  • • Query endpoint
  • • Theory lookup
  • • Paper search
  • • Analytics aggregation