Decouple the Plan Repository from the Platform

At the moment a Platform has many Plans, and a Plan belongs to a Platform. We would like to decouple the notion of a Plan Repository from a Platform. So a top-level entity (which we refer to as an Enterprise) would have zero or many Platforms, and also have zero or many Plan Repositories. A Plan Repository would have zero or many Plans (and so on through the child entities of a Plan). An Assembly would instantiate a Plan (loosely, a Plan would have zero or more Assemblies in zero or more Platforms). Then everything is back to the existing domain model.