XML ids and XSL keys

Leigh Dodds ldodds at ingenta.com
Tue Oct 19 15:09:30 BST 1999


I've been working on a DTD recently, and rejected the use of 
ID and IDREF definitions for cross-referenced attributes largely 
because of the reasons outlined in the XSL spec (12.2 Keys) - 
IDs just don't seem to be flexible enough for all purposes.

XSL defines the xsl:key element which mitigates these 
limitations by providing links between elements which 
are not defined as ID/IDREF pairs.

My questions then (if anyone has the time to answer them :) are 

1. what are the historic reasons for the current definition of 
ID/IDREF/IDREFS attributes?

2. are there ever likely to be any plans to allow the definition 
of attributes in a similar way to XSL keys - i.e. 'ensure that 
this attribute has a unique value within the set of elements having 
that attribute in the document'.

3. or is it that no-one has so far need this kind of functionality 
at the document validation level - is it in fact something which should 
be dealt with at the application level?

4. or have I missed something along the way in RDF/Schemas/...?

Thanks for any responses.


    "Never Do With More, What Can Be Achieved With Less"
				---William of Occam
Leigh Dodds                             Eml:  ldodds at ingenta.com
ingenta ltd                             Tel:  +44 1225 826619
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