Test parent-child retrieval for context and precise evidence

Define the expansion contract

Azure describes document-to-chunk indexing patterns and structure-preserving chunking. In a parent-child design, a smaller unit may determine the match while a larger unit supplies generation context. Specify the relationship explicitly: document ID, revision, parent section, child offsets, and permission metadata. A successful child match is not sufficient if the parent lookup returns an obsolete version or a broader document with different access rules. Evaluate expansion as its own transformation.

Evidence: Chunk large documents for RAG and vector search [1]Document Layout skill [2]

Build a parent-version trap

Author a handbook section whose child paragraph states a delivery deadline and whose parent heading limits the rule to domestic orders. Create a revised parent with a different international exception. Ask one domestic and one international question. A child-only result may omit the scope; the correct parent supplies it. A mismatched parent revision produces a plausible but incorrect rule. The acceptance criterion requires the child and parent to belong to the same intended source revision and eligibility scope.

Measure what expansion contributes

For each retrieved child, save its rank, supporting span, parent ID, parent revision, and expanded context length. Score whether expansion restores required qualifiers and whether it displaces other necessary sources under a fixed total budget. Count parents returned repeatedly from several child hits only once when measuring distinct evidence. Inspect whether a single large parent dominates the context even though another source is required. Separate a child retrieval miss from a failed parent lookup or an overly broad expansion.

Choose an evidence-bounded expansion policy

Prefer the narrowest parent that restores the question’s required context. Test section-level expansion against full-document expansion rather than assuming more context is always useful. Reject expansion when lineage or eligibility cannot be established, and expose that failure to the application instead of silently substituting a nearby document. Keep a control question whose child already contains the complete rule; it reveals whether expansion adds unnecessary cost or distractors without improving answer acceptance.

Measure expansion failures independently from answer failures so missing parents remain visible.

Account for shared parents before budgeting context

Several matching children can point to the same parent section. Resolve those links before assigning context slots so repeated parent expansion does not crowd out another required document. Retain which child hits justified including the parent even when its text appears only once. That lineage helps explain why a large section was selected and whether the matched evidence was actually present. Add a fixture with three child hits from one parent and one hit from an independent exception document; the acceptance rule still requires the exception to survive final context assembly.

Common questions