final DRLLexer lexer = new DRLLexer( charStream );
final TokenStream tokenStream = new CommonTokenStream( lexer );
final DRLParser parser = new DRLParser( tokenStream );
try {
final DeclarativeInvokerDescr declarativeInvoker = parser.from_source( fromSource );
fromSource.setDataSource( declarativeInvoker );
} catch ( final RecognitionException e ) {
throw new SAXParseException( "<" + localName + "> must have a valid expression content ",
this.xmlPackageReader.getLocator() );
}