I have been an outspoken critic of several aspects of W3C XML Schema. It
allows you to do arbitrary blasphemies against logic like this: (01)
<xs:element name="MyElement">
<xs:complexType>
<xs:choice>
<xs:element name="Choice1" type="xs:string" minOccurs="1"/>
<xs:element name="Choice2" type="xs:string" minOccurs="1"/>
</xs:choice>
</xs:complexType>
</xs:element> (02)
Note the conflicting logic. This is a primary example of what happens when
people design schemas without modeling. The semantics of choice state that
you must chose one of the items within the choice block, but not more than
one. This conflicts with the minOccurs="1" flag on both children which has
semantics meaning that each one must occur a minimum of once. (03)
While this could be handled with some overarching cascading scope of logic,
it is sadly not in the last version of W3C schema. How can anyone write a
standard parser for this? (04)
The answer of course is that most people use one of a handful of parsers
(mostly xerces for Cpp and Java) which leads to consistent behavior in
handling based on some group of people's arbitrary choice about how to
handle this. (05)
:( (06)
Duane (07)
On 8/6/07 9:40 AM, "Randall R Schulz" <rschulz@xxxxxxxxx> wrote: (08)
> On Monday 06 August 2007 09:27, Duane Nickull wrote:
>> On 8/3/07 3:25 PM, "Randall R Schulz" <rschulz@xxxxxxxxx> wrote:
>>> I wonder if you think of schema notations other than W3C Schema are
>>> acceptable in this context? Say, RELAX-NG?
>>
>> Randall:
>>
>> Why would RELAX NG not be acceptable? It is of course the far
>> superior schema format.
>
> That is my opinion, as well, but I'm not an XML expert and don't claim
> to know or understand all the issues, especially for very large-scale
> systems. I just know I've had some exposure to both and RELAX NG is far
> more preferable to work with. It does seem tool support still favors
> W3C Schema.
>
>
>> ;-)
>
>
> Randall Schulz
>
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