for(int i = 0; i < node.jjtGetNumChildren(); i++) {
final Node child = node.jjtGetChild(i);
if(child instanceof ASTGroupConstraint) {
final VisualDataGenerator vdg = new VisualDataGenerator(((VisualGraphOperatorWithPrefix) this.visualGraphs.get(0)).prefix);
rdfTermToJoin.addAll((Collection<Operator>) child.jjtAccept((SPARQL1_1ParserVisitor) vdg, rdfHash));
}
else {
// it is an RDF term!
final Item item = SPARQLCoreParserVisitorImplementation.getItem(child);