private void addBorderNodes(AbstractDNode abstractNode, Collection<DNode> result) {
   final Iterator<DNode> itBorder = abstractNode.getOwnedBorderedNodes().iterator();
   while (itBorder.hasNext()) {
     final DNode borderNode = itBorder.next();
     result.add(borderNode);
     addBorderNodes(borderNode, result);
   }
 }