mjn:
I'm fine with your two methods....I also need a way of getting at the
lists stored in the graph without knowing that the graph class exists (I
thought the data manager was supposed to encapsulate the graph, so I think
datamanager should have

ObjectList getObjects() { graph->getObjects()) }
ConnectionList getConnections ....etc...)

di:
As mjn said, we need to be able to get the list of objects and list of
connections from here. I don't think those belongs in the graph