Aggregate

DDD tactical pattern for core subdomain business logic: value objects (immutable, identified by values), entities, aggregates (consistency boundary, one-per-transaction rule, aggregate root, OCC), domain events, domain services; Evans elaborations on associations, entity identity, context-dependent entity/VO classification, service partitioning, modules as model elements

Evans' REPOSITORY pattern: in-memory collection illusion over aggregate roots; hides persistence technology; only for roots needing direct access; transaction control left to client; factory/repository complementarity