RE: Are people really using Identity constraints specified in
> In discussing these problems, two categories of validation > were identified: > > 1. "Syntactical" or "structural" validation > 2. "Semantic" or "business rule" validation > > "Syntactical" or "structural" validation is useful in > eliminating a certain > number of mechanical data entry errors, such as leaving out > required items > or putting strings in fields that require numbers (e.g. phone numbers, > dates, etc.) I was under the impression US phone numbers could be alphabetic? I am not convinced that the distinction you are making is a real one. In the end, all the rules are essentially social rules. > If you are going to validate, then validate! In Problem #2 > the user was > forced to enter a 2-character state code, despite being from the UK. > Several people noted that the problem was not with too much > validation, but > with not enough validation. If the system had been doing a good job > validating then "ZZ" would not have been allowed for the state code. > Further, full validation would have determined that if the > country code is > UK then no value is required for the state code. > This is a classic addictive response. If validation is harming me, do more of it. The strategy assumes that you know better than your customers what constitutes a valid address. Let's face it, you don't, and you never will. A much better strategy is to let them express their address in their own terms. After all, that's what they do in old-fashioned paper correspondence, and it seems to work quite well. Michael Kay
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