{
GraphPattern parentGP = graphPattern;
graphPattern = new GraphPattern(parentGP);
node.jjtGetChild(0).jjtAccept(this, null);
TupleExpr leftArg = graphPattern.buildTupleExpr();
graphPattern = new GraphPattern(parentGP);
node.jjtGetChild(1).jjtAccept(this, null);
TupleExpr rightArg = graphPattern.buildTupleExpr();
parentGP.addRequiredTE(new Union(leftArg, rightArg));
graphPattern = parentGP;
return null;