for (int index = children.size(); --index >= 0; ) {
Expression child = children.get(index);
// The child expression is not a JOIN expression
if (!isValid(child, JoinBNF.ID)) {
addProblem(child, IdentificationVariableDeclaration_InvalidJoin, child.toActualText());
}
// Validate the JOIN expression
else {
child.accept(this);
}