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At 02:54 PM 8/4/2002 -0700, Joshua Allen wrote:
>(Not that anyone here is advocating this, but just in case...)
>
>Regular expressions that enforce syntactic patterns for particular units
>of measure are fine, but I would strongly caution against trying to assign
>schema constraints based on the actual values (other than range
>constraints to specify valid values, which I would classify as regular
>expressions anyway). Even worse are co-occurence constraints on the
>values, and worst of all are constraints that involve UOM translations.
>
>These types of constraints tend to fall into the realm of "business
>rules", and in no way belong in a data schema language. I am aware that
>some people advocate this, but I think anyone who has experience with UOM
>processing in systems like EAP, BOM, Financials, and so on will agree that
>to do so is just begging for sorrow. It's one of those "nice in theory,
>if you don't know the theory very well" things.
Attempts to solve UOM (you do mean units of measure, I hope?) globally are
likely a horrible mistake. (Think WXS date/time types.) However, building
systems which make it possible to solve UOM locally makes a lot more sense
to me than "well, it's an int, but who the hell knows how many of what it
represents?"
Local representation for local information makes a lot more sense to me
than any effort to globalize the representation by converting everything to
a common format. People who insist on building centralized arbiters of
information probably think differently, but since I find the centralized
arbiter model repulsive in itself, I don't think it's particularly
interesting. (Nor do I care what SAP and Baan and PeopleSoft find convenient.)
Simon St.Laurent
"Every day in every way I'm getting better and better." - Emile Coue
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