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RE: Re: determining ID-ness in XML

• From: Michael Brennan <Michael_Brennan@A...>
• To: xml-dev@l...
• Date: Mon, 05 Nov 2001 15:59:46 -0800

Is there any reason why XLink labels cannot be used for this? If you want to
use a simple name in a fragment identifier, why not treat the referenced
element as a resource and give it an xlink:label attribute, and modify
XPointer to permit use of XLink label names as fragment identifiers as an
alternative to IDs?

> -----Original Message-----
> From: Elliotte Rusty Harold [mailto:elharo@m...]
> Sent: Monday, November 05, 2001 1:51 PM
> To: xml-dev@l...
> Subject: RE:  Re: determining ID-ness in XML
> 
> 
> At 4:24 PM -0600 11/5/01, Bullard, Claude L (Len) wrote:
> >Isn't the point to use a means the XML processor
> >isn't free to ignore per specification?  That is
> >why the concept of "reliability" was introduced
> >although one could say "efficiency" and mention
> >the cases of XPointers and serialization.
> >
> 
> No. That's not the point. It never has been. The XML processor is 
> most certainly free to ignore the semantics of xml:id, just like 
> today it ignores the semantics of xml:base. In fact, I would be very 
> surprised if an XML processor did recognize anything special about an 
> xml:id attribute. The client application that receives data from the 
> XML processor would impart certain semantics to xml:id, though even 
> there it would be free to ignore the standard semantics and apply 
> local processing rules instead, or simply ignore the attribute 
> completely, if that's what made sense to the people using the client 
> application. Of course this is exactly how every other specification 
> is implemented in practice today. Local client apps can always do 
> whatever they need to do.
> 
> People keep getting confused with what we're really asking for 
> because ID has a certain meaning in the context of XML 1.0, but none 
> of that's necessary or even relevant here. We are *not* talking about 
> XML 1.0 or schema ID attributes. All we're asking for is  name we can 
> link to. This could be done purely within the XPointer specification 
> without touching XML core. This reminds me a little of the type 
> debate a month ago, so let's steal a march from that flame war and 
> change the vocabulary so we stop getting confused.
> 
> I officially withdraw my request for a standard xml:id attribute for 
> XML documents.
> 
> I issue a new request for a standard xml:target attribute. This would 
> provide a unique name for XPointers to link to. It would have no 
> necessary type. It would have no affect on validity. The documents in 
> which it appears may or may not have DTDs, may or may not be valid, 
> and may or may not declare this attribute with any particular type. 
> Whether such a document was valid would be determined exactly 
> according to the rules of XML 1.0. If xml:target (and everything else 
> in the document) were properly declared the document would be valid. 
> If xml:target were not properly declared, the document would not be 
> valid. No parsers would change. The definition of validity would not 
> change. The only necessary change would be to XPointer and other 
> client specifications that needed to pay attention to this attribute. 
> Everybody else can ignore it.
> 
> A few people seem to think that the xml: prefix is more special than 
> it is. The only thing that's special about it is that the namespace 
> doesn't have to be declared; but if that bothers you we can revise 
> this. Instead of using the xml: prefix we can use the xptri prefix 
> mapped to the http://www.w3.org/2001/xpointer-instance namespace URI. 
> As always the prefix can change as long as the URI remains the same.
> 
> >One extends the system vocabulary precisely because
> >it extends the requirement for the XML processor.
> >If all you need is a convention, a PI or an
> >alternative namespace are equally ignorable.
> >Otherwise, we could just go on as is:  "if you
> >need an ID, spec a DTD and cite it in the
> >contract for the communication when using
> >well-formed files.  This is only as reliable
> >as your partners are diligent."
> >
> 
> I'm not quite sure where you draw the line on what is and is not the 
> system vocabulary. I could implement the xptri scheme in my own 
> software today without stepping on anyone's toes. That's what the X 
> in XML is all about. But it would probably be easier if we all agreed 
> on using the same thing for the same job.
> 

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