throw cxml::Error ("unrecognised root node " + _node->get_name() + " (expecting " + _root_name + ")");
} else if (_root_name.empty ()) {
_root_name = _node->get_name ();
throw cxml::Error ("unrecognised root node " + _node->get_name() + " (expecting " + _root_name + ")");
} else if (_root_name.empty ()) {
_root_name = _node->get_name ();