LOCAL
     the_reverse : oriented_open_shell;
   END_LOCAL;
   IF ('TOPOLOGY_SCHEMA.ORIENTED_OPEN_SHELL' IN TYPEOF (a_shell) ) THEN
     the_reverse := dummy_tri ||
                  connected_face_set (
                      a_shell\connected_face_set.cfs_faces) ||
                  open_shell () || oriented_open_shell(
                    a_shell\oriented_open_shell.open_shell_element,
                      (NOT (a_shell\oriented_open_shell.orientation)));
   ELSE
     the_reverse := dummy_tri ||
                 connected_face_set (
                     a_shell\connected_face_set.cfs_faces) ||
                 open_shell () ||  oriented_open_shell (a_shell, FALSE);
   END_IF;
   RETURN (the_reverse);