DDD is first of all about extracting our domain into separate block that does not depend on anything. It describes our business logic, using building blocks according to Evans. So, but what about dependencies between different domains and how to maintain them.

For example, I have two domain entities: Ship and Container
Each container belongs to the certain ship. Finally, in DB (RDB) we can set it like FK: container.shipId (FK) -> Ship.id (PK). But when I am trying to get data (for example, findOne(shipId)) from repository (for instance, ORM returns me the whole information I can only receive: ShipDbEntity that even has an array of ContainerDbEntity ) I do not know how to map it in Ship domain entity. On one side, one domain does not have to know about the details of another one. And on the other hand we should respect that dependency between two entites.

P.S.: Do not tell me about Aggregates. I know that this example is good for this concept, but imagine we have entities that are truly equal.