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> Ahh, good point, and one for the validation decision tree: Use a > Schema/DTD and XML-level validation to enforce constraints that are > universal across applications that use a specific data format. Use > application logic (procedural code?) to enforce constraints that specialized > applications know about. For (a quickly contrived) example, a bookstore > site might need some specialized module that knows about ISBNs and how to > validate them against a database; most other modules just need to ensure > that the ISBN value doesn't get lost and "trust" that nobody mucks with the > value. So, what schemas can capture are the constraints common to all apps. How about the following possibilities? (a) Each app (in the worst case) may use a slightly different schema to validate a given XML document. That is, each schema can capture any special constraints local to the app. I see that this contradicts the common notion that schemas are global. However, when it is accepted that each app can use its own logic to verify the data, why not extend the same to schemas? (b) In the above example, each app has a slightly different set of constrtaints for the same data. Can we not extend this argument to say that each app has its own view (both structure and constraints) for a given document. In this case, each schema may specify only a subset of the structure/constraints. I see that the current validating parsers won't tolerate this, but how does this sound in theory? Subbu
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