XML Schema 1.1 introduces a new feature called type alternatives (aka
conditional type assignment) which allows you to do this. There's an
implementation in the current development stream of Xerces-J; still not=

quite ready for prime time, but should be available in a release soon.

Thanks.

[1] http://www.w3.org/TR/xmlschema11-1/#cTypeAlternative

Michael Glavassevich
XML Parser Development
IBM Toronto Lab
E-mail: mrglavas@c...
E-mail: mrglavas@a...

zachary.harvey@g... wrote on 12/05/2008 12:11:10 PM:

> This may be bad design, so if it is, then I guess what I'm looking
> for is an elegant alternative solution. However I don't believe the
> following to be a product of poor design, and so the following
> question should apply:
>
> I want a particular element, <widget> to force the user to define a f=
oo
> attribute, which will be an enum type of three potential values: me, =
you
or us
> . For example:
>
> <widget foo="me" />
> <widget foo="you" />
> <widget foo="us" />
>
> Would all be legal <widget> instantiations. And so I have the
> following so far in my XSD:
>
> <xs:element name="widget" minOccurs="1" maxOccurs="unbounded">
>     <xs:complexType>
>         <xs:attribute name="foo" type="xs:string" use="required=
">
>             <xs:simpleType>
>                 <xs:restriction base="xs:string">
>                     <xs:enumeration value="me" />
>                     <xs:enumeration value="you" />
>                     <xs:enumeration value="us" />
>                 </xs:restriction>
>             </xs:simpleType>
>         </xs:attribute>
>
>         <xs:sequence>
>             <!-- No definition yet ... -->
>         </xs:sequence>
>     </xs:complexType>
> </xs:element>
>
> What I am looking for is the ability to define <widget>'s sequence
> based on the value of foo.  If foo="me" I want it to contain, say,
> an <apple> element. Else if it is "you" or "us" I want it to contain
> an <orange> child element.  So for example:
>
> <widget foo="me">
>     <apple>Hello!</apple>
> </widget>
>
> <widget foo="us">
>     <orange>XSD!</orange>
> </widget>
>
> I have been pouring through the tutorials and cannot find a way to
> include this conditional functionality...=