A Node_Ptr in the RFG is made visible in a view.
The Insert_Edge Methode sends a "Child_Added" Message to the observers of the view.
The RFG_View_Node_Model in OpenCAGE receives this message, creates a new RFG_Node_Model, adds it to its children, attaches an observer to it and sends a "Child_Added" Message to its own observers.
The GDC receives the message, creates a new Node_Display, adds it to its children, attaches a Object_Display_Observer to it and draws it.