When to Add a Graph to RAG: Design a Relationship-Question Pilot

Add a graph to RAG when a demonstrated question depends on explicit relationships that your current retrieval path fails to supply reliably. Do not start with a target number of nodes or a goal to make every document part of a graph.

A useful pilot is small enough that you can inspect each relationship and its evidence. It should show whether graph-assisted retrieval improves the answers that motivated the work.

Choose questions with an explainable path

A question such as “Which services depend on the component affected by this incident?” may require following dependency links. A question asking for the component's definition may be answered by one passage.

Include both kinds in the fixture. The graph should improve the relationship questions without making direct lookups slower or less reliable for no benefit. The graph-versus-vector guide explains that distinction.

Build only the relationships the pilot needs

Define a small set of entity and relation types. Preserve source IDs, relevant time, and access scope on the evidence supporting each edge. If an extraction model proposes the edge, validate identifiers and relation direction before accepting it.

A missing edge and a nonexistent relationship are different states. The answer should not claim that two services are independent merely because the current graph lacks a path.

Bound expansion at query time

Limit allowed relation types, depth, and returned evidence. Fetch source passages that support the selected path rather than giving the answer model a large unlabeled neighborhood.

Apply permissions throughout traversal and source retrieval. A permitted starting node does not imply permission to reveal every connected entity.

Compare with the original retrieval path

Run the same questions against passage retrieval and the graph-assisted route. Measure supporting-path validity, answer support, maintenance work, and latency. Include an outdated edge, a corrected source, and an unanswerable relationship question.

The vector-versus-graph query guide helps decide whether each pilot question needs similarity, explicit relationships, or both.

The small graph tutorial provides a testable starting shape. If the requirement concerns relationships between remembered facts rather than a custom domain graph, review Supermemory's graph-memory model and evaluate it on the same cases.