public void validate() throws XPathException {
select = typeCheck("select", select);
try {
RoleLocator role =
new RoleLocator(RoleLocator.INSTRUCTION, "sql:column/select", 0);
select = TypeChecker.staticTypeCheck(select,
SequenceType.SINGLE_ATOMIC,
false, role, makeExpressionVisitor());
} catch (XPathException err) {