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

At 10:57 AM +1100 11/6/01, Marcus Carr wrote:

>In the DTD, you'd need to define xml:target to cover pretty much every
>CDATA attribute then, wouldn't you? Without knowing the context that the
>instance will be used in, how can you determine whether a particular
>attribute might be useful as a unique identifier? The instance should
>scope what is a unique identifier - why get the DTD involved at all?

Simple: we need unique targets so we define an attribute that 
provides such targets in some convenient namespace, declare victory, 
and go home. The instance context really isn't considered, any more 
than it is in XLink, xml:base, or similar attribute-based 

Some people have suggested that what we really need is an attribute 
to identify the target attributes. I'm not convinced we need the 
extra layer of indirection, but if it turns out we do, it would work 
the same way.

>And everyone who may need to validate downstream from the instance being
>regarded as well-formed only will need to change their DTDs or strip out
>the invalid attributes? It sounds like a pretty hard sell to me...

No, no, no! If you need valid documents, then the DTD declares all 
attributes that are used in that document, xml:target would be 
declared in the DTD. More importantly, however, valid documents do 
have DTDs, do have ID type attributes, and do not not need to use 
xml:target. It's only for those documents that aren't valid in the 
first place that something like xml:target becomes necessary.

| Elliotte Rusty Harold | elharo@metalab.unc.edu | Writer/Programmer |
|          The XML Bible, 2nd Edition (Hungry Minds, 2001)           |
|              http://www.ibiblio.org/xml/books/bible2/              |
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