//response type = text/xml
//no caching and no timeout if possible!
ExternalContext externalContext = _facesContext.getExternalContext();
externalContext.setResponseContentType("text/xml");
externalContext.addResponseHeader("Pragma", "no-cache");
externalContext.addResponseHeader("Cache-control", "no-cache");
//under normal circumstances pragma should be enough, IE needs
//a special treatment!
//http://support.microsoft.com/kb/234067
externalContext.addResponseHeader("Expires", "-1");