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   Re: [xml-dev] Restrictions on existence of attributes?

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> Howard Bartel wrote:
>> On Jun 27, 2006, at 07:57, Rick Jelliffe wrote:
>> How do I specify that an element MUST have ONLY ONE of a set of  
>> possible
>> attributes?
>> I understand that there is a "choice" option but it seems that  
>> this only
>> applies to elements, not attributes within an element.
> If you are using XML Schemas, then look at the "enumeration"  
> "facet" of "datatypes". Your element must be a "complex type".

I don't think that'll solve Howard's problem since he wants only one  
of a set of attributes, not only one of a set of attribute values.  
Presumably this can always be remodelled with some indirection (e.g.  
having a @name attribute which is an enumeration, and an @value which  
would give its value), but that might not be an option.

My XML Schema is getting very rusty since I don't get to use it much  
anymore, but I don't think it can be done (or if it can it involves  
dark magic). In RelaxNG it's just a <choice> of <attribute> elements,  
easy as ¹.

-- 
Robin Berjon
    Senior Research Scientist
    Expway, http://expway.com/






 

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