code: public void startPrefixMapping(String prefix, String uri)
            throws SAXException
    {
  
      if (DEBUG)
        System.out.println("TransformerHandlerImpl#startPrefixMapping: "
                           + prefix + ", " + uri);
  
      if (m_contentHandler != null)
      {
        m_contentHandler.startPrefixMapping(prefix, uri);
      }
    }
docs: Filter a start Namespace prefix mapping event.
  
  @param prefix The Namespace prefix.
  @param uri The Namespace URI.
  @throws SAXException The client may throw
  an exception during processing.
  @see org.xml.sax.ContentHandler#startPrefixMapping