code: @Override
      public void writeDTD(String rootName, String systemId, String publicId,
                           String internalSubset)
          throws XMLStreamException
      {
          /* Alas: although we can create a DocumentType object, there
           * doesn't seem to be a way to attach it in DOM-2!
           */
          if (mCurrElem != null) {
              throw new IllegalStateException("Operation only allowed to the document before adding root element");
          }
          reportUnsupported("writeDTD()");
      }
docs: public void writeCData(char[] text, int start, int len)