private GuiService getGuiService(String pack, Element elem) throws Exception {
if (ConfigFile.Output.Child.XML.equals(elem.getName()))
return new XmlFile(elem, defaultLang, defaultLocal);
if (ConfigFile.Output.Child.CALL.equals(elem.getName()))
return new Call(elem, pack, appPath);
throw new IllegalArgumentException("Unknown GUI element : " + Xml.getString(elem));
}