Heyo,
On 2007-05-21 14:04:17 -0400 "Ramkumar Menon"
<
ramkumar.menon@...> wrote:
> The specification of a uniqueness constraint is incompatible with the
> optionality of the attribute.
>
> I am trying to understand the rationale of this explanation, but with
> no
> luck. :-( Maybe I am missing something here.
> Would it be possible to elaborate more on this?
It's possible that we missed something, in discussing this. We were
under the impression that optional attributes could not be used in the
selectors of unique constraints.
Further, the validation that can be done using the unique constraint,
when the target attribute is optional with defaulting rules that are
also inexpressible in WXS, is less than ideal:
<wsdl:operation> <!-- using default, so input-output -->
<wsdl:output />
<wsdl:input />
<wsdl:output messageLabel="Out" />
<wsdl:input messageLabel="In" />
</wsdl:operation>
This can't be caught with the uniqueness constraint (which is rather
the purpose of the uniqueness constraint). If we can't catch such
cases, then adding the unique constraint to the XSD is apt to suggest
that all that needs to be checked is the result of that, when in fact
it is entirely inadequate as a consequence of the optionality of the
attribute and the rules for defaulting its value when it is missing.
Note that the above fails for other reasons (not expressed in the
schema, but expressible in the assertions of the component model).
Amy!
--
Amelia A. Lewis
Senior Architect
TIBCO/Extensibility, Inc.
alewis@...
