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But in 98% of the cases, folks will make do with the default set of
(standard ISO 4217) currency codes provided for in the "off-the-shelf"
set of UBL schemas. In another 1.9% of the cases, they will want to
restrict the codes to currencies they "understand" or trade in - and
would want the parser to intercept the "unsupported" currencies.
Extending the list is even rarer.
Personally, I think this is spurious logic; it seems much easier to
have the schema serve only as a general purpose syntax "gate-keeper" -
and to enforce the use of particular currencies (e.g., USD, CAD, GBP and
EUR) within the application. And if I were intent on allowing the use
of a currency not yet in the "authorized" list, I'd just intercept the
parser exception and check for the one or two unusual codes.
This insistence on "override" code lists must be a hold-over from the
days of EDI. Nonetheless, it does provide an interesting problem to
explore and to see if the XML schema specification provides an elegant
way to do code list extensibility.
William J. Kammerer
Columbus, OH 43221-3859 . USA
+1 (614) 487-0320
----- Original Message -----
From: "Michael Kay" <firstname.lastname@example.org>
To: "'William J. Kammerer'" <email@example.com>; "'XML Developers
Sent: Sunday, 06 March, 2005 06:49 PM
Subject: RE: [xml-dev] Is there a way to reuse and extend an enumeration
in XML schema
> I can't speak to Kenneth Stephen's requirements, but I'm pretty sure
> that UBL wants to give users some way of extending (and restricting)
> currency codes (inter alia) without modifying any of the
> distributed UBL schemas.
Surely the right way to tackle this is for the "distributed UBL schemas"
to impose no restrictions on the list of currency codes, and for user
schemas to impose an enumerated list by restricting the "standard" one?