in src/main/java/org/apache/sling/scripting/xproc/xpl/XplBuilder.java [51:58]
public Step build(Reader xplReader) throws Exception {
XMLReader xMLReader = XMLReaderFactory.createXMLReader();
XplHandler xplHandler = new XplHandler();
xMLReader.setContentHandler(xplHandler);
InputSource inputSource = new InputSource(xplReader);
xMLReader.parse(inputSource);
return xplHandler.getRootStep();
}