Thanks David.
> If the input is validated (against xsd or relax or schematron or any
> other schema language of choice) the user will get specific error
> message about missing or incorrectly typed values at an earlier
stage,
> before the calculation has been attempted.
Doesn't that presuppose a certain environment: the XPath is running in
an environment where the data has already been checked?
Ah, you are bringing up an excellent point: how do we design an XPath
statement that gracefully degrades when the expected schema checking is
absent?
/Roger
