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RE: Restrictions on existence of attributes?

• To: "Robin Berjon" <robin.berjon@e...>,"Rick Jelliffe" <rjelliffe@a...>
• Subject: RE: Restrictions on existence of attributes?
• From: "Chiusano Joseph" <chiusano_joseph@b...>
• Date: Tue, 27 Jun 2006 09:51:22 -0400
• Cc: "Howard Bartel" <hbartel@c...>,<xml-dev@l...>
• Thread-index: AcaZ2QJd+FhZKazmT8aGCe6gvRojxAAF7F5Q
• Thread-topic: Restrictions on existence of attributes?

Perhaps a reference to an attribute group, with a minOccurs and maxOccurs of 1? 

Joe

Joseph Chiusano
Associate
Booz Allen Hamilton
 
700 13th St. NW, Suite 1100
Washington, DC 20005
O: 202-508-6514  
C: 202-251-0731
Visit us online@ http://www.boozallen.com

-----Original Message-----
From: Robin Berjon [mailto:robin.berjon@e...] 
Sent: Tuesday, June 27, 2006 6:59 AM
To: Rick Jelliffe
Cc: Howard Bartel; xml-dev@l... Developers
Subject: Re:  Restrictions on existence of attributes?

> 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 &pgr;.

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



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