Aggregates are Blackboxes

Aggregates encapsulate Domain Elements, Business Rules (Business Invariants) and data. They represent a Domain Concept in entirety and don't leak any detail into other Aggregates. They are entirely responsible for processing an intention.

The linkages between domain elements enclosed with Aggregates are only known to the Aggregate and are not exposed to the outer world. An external party should not be able to traverse (or even understand) the information graph enclosed within the Aggregate.