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Michael Kay on data constraints

Seen on xml-dev:

"I tend to be a little wary of constraints myself. Many of those you see in student textbooks are misguided. If I see a schema (XML or RDB) with the constraint that employees must be over 16, I ask myself what the IT department would do if the business decided to hire someone under 16. If there's a rule that an employee's manager must themselves be an employee, I ask what would happen when someone is told that they now report to a contractor. 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). A guideline I use is that constraints should be there only to protect the IT system itself from data that it cannot handle."

August 13, 2004 12:48 PM


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