[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] FW: Fallacies of Validation ... RE: Are people reall
I am forwarding an excellent message from Mary Holstege: -----Original Message----- From: Mary Holstege [mailto:holstege@m...] Sent: Wednesday, August 25, 2004 9:44 AM To: Roger L. Costello Subject: Re: Fallacies of Validation ... RE: Are people really using Identity constraints specified in XML schema? Roger L. Costello writes: > It would be very useful if we could have a simple example that shows how > several schemas might be employed, rather than a single schema. Could > someone provide an example? Here's a really quick example: support all you care about in some phase of processing is picking up the IDs in a document. Then you define a minimal schema where everything is open with the appropriate ID attributes. Maybe you're going to generate an index. In another phase of processing all you care about is checking that dates are in the right date range. So you have another minimal schema that only pays attention to dates. Or to take another example, you have a broad dispatch schema that really just wants to figure out whether you have a foo or a bar, but everything else is left loose, because once you dispatch to the foo-branch or the bar-branch you can put in place a tight schema that will help you clean your data. Alternatively, you let go of what I consider the number one schema fallacy: * validation is a pass/fail operation Not so, although lots of people are still stuck in that way of thinking, including, alas, a lot of the vendors. The schema design goes to great pains to make it possible to do things like this, for example: * validate a document against a tight schema, and then ask questions of the result such as "show me all the item counts that failed validation because they were too high" That is why there is the PSVI, that is why UPA is so important (how do I know which item count failed validation if I can't figure out which element matched which particle? or failed to match?) //Mary btw: xml-dev is a read-only medium for me at the moment, which is why I am responding privately.
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