On 15/09/2010 1:35 AM, Heitke.Chris wrote:
360A1674FFC73B42BFD657060941DBF3146115E2@FG200201EVS.ftb.ca.gov"
type="cite">
I have been asked what data type should be
used for a
website address element in a schema?
At first I thought the anyURI type would be
appropriate. Maybe
would insure the data is valid address. Whereas the string
type might not…
problem is, validation tests show that the anyURI type allows
virtually
anything, just like the string type… So why use anyURI as a
base data
type? It does not appear to provide any greater assurance that
the data will be
better qualified than what would be gotten from a string?
Christopher A. Heitke
State
of California, FTB
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The road to xs:anyURI was paved with good intentions. The XSD 1.0
spec is notoriously vague about what validation rules should be
applied to it (it contains the notorious phrase "This definition
imposes only very modest obligations on ·minimally conforming·
processors", while failing to say clearly what those obligations
are) and in consequence many implementations allow anything (or
almost anything). In XSD 1.1 the WG admitted defeat and changed the
spec so the lexical space is exactly the same as xs:string. The
XQuery and XSLT specifications also treat xs:anyURI more-or-less as
equivalent to xs:string.
So should you use xs:anyURI? Well, it provides a bit of
documentation of your intent, and it might give you better bindings
to data types in other languages. It has a bit more semantics than
xs:string, though it's all very implicit. But the fact that
something is present in a spec doesn't mean you have to use it.
Michael Kay
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