Mental model
A query pipeline may classify, decompose, expand, or route a request, but every transformation must remain attributable to the original intent.
Learning outcomes
- Explain the mechanism and ownership boundaries behind Query Rewriting and Routing.
- Compare the main design alternatives and their operational trade-offs.
- Diagnose common failures and select evidence for a production decision.
Theory
Use deterministic normalization first, then bounded model rewriting for ambiguity or decomposition. Preserve original and rewritten queries, route confidence, policy filters, latency budget, and fallbacks. Evaluate each route independently.
Trade-offs
Rewriting can improve recall for vocabulary mismatch but can erase constraints or introduce unsupported terms. Multi-route search improves coverage while increasing cost and duplicate evidence.
Failure modes and misconceptions
Dropping negation; rewriting identifiers; routing on sensitive attributes; hiding transformations from traces; no fallback; and evaluating only the final merged list.
Decision scenario
A user asks for a policy exception using an internal acronym. Decide when to expand, decompose, route, or ask for clarification.
What information must be preserved so a rewritten retrieval query remains auditable?
Primary sources
information-retrieval-bookrag-paper