Uniqueness only for some attribute value

[kate]

Hi,

I want to add uniqueness constraint for an attribute, but only for a
certain value, for example, the attribute can be 'true' or 'false' or
none, I want to allow only one 'true' value. How should I do? I tried
to use like this:
<xs:key name="attributeKey">
<xs:selector xpath="./MyElement[@myAttribute = 'true']"/>
<xs:field xpath="@myAttribute"/>
</xs:key>

but this gives validation error in xsd.
Any help is appreciated.

Thanks.

[Oleg Tkachenko [MVP]]

kate wrote:

I want to add uniqueness constraint for an attribute, but only for a
certain value, for example, the attribute can be 'true' or 'false' or
none, I want to allow only one 'true' value. How should I do? I tried
to use like this:
<xs:key name="attributeKey">
<xs:selector xpath="./MyElement[@myAttribute = 'true']"/>
<xs:field xpath="@myAttribute"/>
</xs:key>

AFAIK XSD doesn't allow that. It only supports very limited subset of XPath.
--
Oleg Tkachenko [XML MVP, XmlInsider]
http://blog.tkachenko.com

[kate]

> AFAIK XSD doesn't allow that. It only supports very limited subset of XPath.

Thanks for reply.

And do you know how I can use conditions in xsd? For example, I would
like to restrict some element or attribute under a certain condition,
like when an attribute is some value. Thanks in advance.

[Oleg Tkachenko [MVP]]

kate wrote:

And do you know how I can use conditions in xsd? For example, I would
like to restrict some element or attribute under a certain condition,
like when an attribute is some value. Thanks in advance.

I'm afraid it's the same anser - you cannot. XSD Schema doesn't support
co-occurence constraints. Try different schema language (such as
schematron or relaxng) to validate such constraints.

--
Oleg Tkachenko [XML MVP, XmlInsider]
http://blog.tkachenko.com