The top Node_Model
throws Unknown_Node_Exception .
This abstract class represents a root node model. It is an extended Node_Model, which has some special stuff only required once, in the root. It extends Simple_Node_Model, because there is the Attach, Detach, Notify stuff.
Returns a node for the given name. If the name is not known (i.e. Is_Known_Node retuns False for the given name), an Unknown_Node_Exception is thrown.
Returns True if the given name is a known node, False otherwise.