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Eric van der Vlist <vdv@dyomedea.com> writes:
> On Fri, 2003-10-03 at 12:42, Max Chappell wrote:
>
>> Does anybody have any comments on the validity of the above?
>
> The IBM Schema Quality Checker is right...
>
> If you have several "Person" elements in your instance document, a
> schema processor can't immediately tell if they belongs to the first
> sequence, to the xs:element that follows or to the second sequence and
> that's violating the restrictions of W3C XML Schema.
>
> Furthermore, your schema is not capturing "they want any element of the
> three elements in any order, as many or as few times as they want" :-)
> ...
>
> The usual way to translate "any element of the three elements in any
> order, as many or as few times as they want" in WXS is through
> xs:choice:
>
> <xs:choice minOccurs="0" maxOccurs="unbounded">
> <xs:group ref="tns:GenericElements"/>
> <xs:element name="Person" type="tns:Person"/>
> <xs:element name="Location" type="tns:Loc"/>
> </xs:choice>
>
> That doesn't capture the fact that "they also want at least one
> person element to be present every time" but I don't see how you can
> capture this using WXS alone.
Sure, it's easy -- you want the schema equivalent of
<!ELEMENT x ((a|b)*,c,(a|b|c)*)>
<xs:sequence>
<xs:choice minOccurs="0" maxOccurs="unbounded">
<xs:group ref="tns:GenericElements"/>
<xs:element name="Location" type="tns:Loc"/>
</xs:choice>
<xs:element name="Person" type="tns:Person"/>
<xs:choice minOccurs="0" maxOccurs="unbounded">
<xs:group ref="tns:GenericElements"/>
<xs:element name="Person" type="tns:Person"/>
<xs:element name="Location" type="tns:Loc"/>
</xs:choice>
</xs:sequence>
ht
--
Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
Half-time member of W3C Team
2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
Fax: (44) 131 650-4587, e-mail: ht@cogsci.ed.ac.uk
URL: http://www.ltg.ed.ac.uk/~ht/
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