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   RE: [xml-dev] Are people really using Identity constraints specified in

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> 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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