Re: [xml-dev] Re: determining ID-ness in XML

[Rick Jelliffe <ricko@allette.com.au>]

From: "Henry S. Thompson" <ht@cogsci.ed.ac.uk>

> It's precisely because IDness is orthogonal to type-validity that
> xml:id is the _wrong_ solution -- it doesn't allow me to combine
> IDness with e.g. being an NMToken or CDATA or in integer or . . .

Well then what about

     xml:id
     xml:key

where id is an ID and key can be any string?  
 
Then we can use our schema language to further constrain the datatype of 
the xml:key (or xml:id) for each element as required.  Or we can
constrain the datatype of the key according to the element which refers
to it (we can do that, can't we?)

No-one has ever demonstrated (that I have seen) that ID is not
a really useful mechanism for many kinds of XML documents.
In many cases it is trivial to munge a text key into a useful ID,
and this separation of data values from IDs prevents potential
problems with duplicate keys which could not occur in tables
but could occur with trees (if the keys are also data values).

Cheers
Rick Jelliffe