Statements storeded in a DBI interface will have their resources also stored in the DB. If you say that a specific class is a subClassOf another class, this means that the URI subClassOf is stored in the DB, even if it is primarly handled by the RDFS interface.
The node will point to a model and that model will hold information about the origin of the information and then it was last updated. The agent will be the URI for the server and the source will be the URI of the interface. The details of this has not been developed.
The object in the cache will be marked with the interface that handles its storage/retrievel. Other modules could offer methods for the object.
A search for a resource will use the range/content of the object. The find method for a model will search its contents, a find for a interface will search the interface and a find for the RDF::Service object will search all connected interfaces.
It's one thing to be the owner or home interface of a node, and antoher thing to say something about the node or with the node. If we want to know everything said about a thing, we will have to search all interfaces that could give a part of the answer. But if we only want to know whats said from a limited number or sources, we can restrict the search to the interfaces that handles the models owned by the source we are intrested in.