Constraints, business rules, and don't forget the Schematron
by Uche Ogbuji
There's an interesting discussion in progress on XML-DEV (besides the above URL, look out for other August subject lines with "constraint"), including this insightful entry by Mike Kay. The memorable kernel of his point is: "It's not the job of computers to limit what people are allowed
to do (or the job of the IT department to regulate the business)." The only problem with this thread is that everyone seemed to forget The Schematron: on the road to ISO standardization, increasingly well-implemented, and just what the doctor orders for constraints. Also don't forget Jeni Tennison's Datatype Library Language.