* Parses a RELAX NG grammar into an annotated grammar.
*/
private Model loadRELAXNG() throws SAXException {
// build DOM forest
final DOMForest forest = buildDOMForest( new RELAXNGInternalizationLogic() );
// use JAXP masquerading to validate the input document.
// DOMForest -> ExtensionBindingChecker -> RNGOM
XMLReaderCreator xrc = new XMLReaderCreator() {