ItsNatStfulDocumentImpl itsNatDoc = getItsNatStfulDocument();
Document doc = itsNatDoc.getDocument();
// Elementos que implementan ElementDocContainer: <object>, <iframe> y <embed>
NodeConstraints rules = new NodeConstraints()
{
public boolean match(Node node, Object context)
{
return (node instanceof ElementDocContainer); // <iframe> y <object>
}