A federated product knowledge layer
PKG does not copy every catalog into one global store. It keeps a compact identity and evidence graph, resolves authoritative sources by scope, and hydrates volatile offer data when needed.
Resolution flow
query → candidates → product identity → source authority → freshness → projection → citation
Boundaries
Product, model, variant, revision and offer remain distinct entities. Manufacturer authority for specifications does not imply authority for a retailer's current price.