The Repository has a unique root object, which is where the Repository Browser starts its browsing. The Repository Browser displays Repository data by iterating through all of the interfaces attached to the root object, then iterating through the collections attached to those interfaces, and so on.
Each information model normally adds an interface either to the Repository root object, or to some other object that is ultimately connected to the Repository root object. The added interface is then defined to contain one or more collections that relate to other objects in that information model.