public Object visit(final ASTFilterConstraint node, final Object data) {
final SPARQLParserVisitorImplementationDumper filterDumper = new SPARQLParserVisitorImplementationDumper();
final String filterExpr = node.jjtGetChild(0).accept(filterDumper);
final Filter filterOp = new Filter(this.prefix, filterExpr);
return filterOp;
}