W3C home > Mailing lists > Public > public-xml-id@w3.org > April 2005

Re: FW: W3C XML ID ambiguity

From: Elliotte Harold <elharo@metalab.unc.edu>
Date: Fri, 22 Apr 2005 18:56:55 -0400
Message-ID: <42698137.4000108@metalab.unc.edu>
To: Chris Lilley <chris@w3.org>
CC: "Bassetti, Ann" <ann.bassetti@boeing.com>, public-xml-id@w3.org, "Bugbee, Larry" <larry.bugbee@boeing.com>, "Henry S. Thompson" <ht@inf.ed.ac.uk>, Liam Quin <liam@w3.org>, Bert Bos <bert@w3.org>, "Reid, Travis S" <travis.s.reid@boeing.com>, "Gerstmann, Jerry P" <jerry.p.gerstmann@boeing.com>, "Meadows, Joe" <joe.meadows@nobs.ca.boeing.com>

Chris Lilley wrote:

> I don't hear you calling for rescinding xml:space, xml:base and so the
> magic predeclared not remappable namespace code still needs to be in the
> parser, right? So re-using it does not seem to cause additional burden.

In practice, the special purpose code often is not in the 
parser/library. Then again sometimes it is. Often it's just left 
completely unspecified what's supposed to happen. I bring up again the 
case of //*/xml:space and //*/foo:space when xml is not mapped to 
http://www.w3.org/XML/1998/namespace and foo is. Even in the case of XML 
parsing, exactly what sort of error is it when the wrong prefix or wrong 
namespace URI is used here? Parsers/libraries are extremely inconsistent 
on these points.

Furthermore, many libraries do not need to special case xml:space and 
xml:lang at all because they do not provide any API calls that reference 
those characteristics. xml:base is a little trickier because some specs 
like DOM 3 do indeed have a getBaseURL() call or something similar, but 
a lot still don't. With xml:id we're moving deeper into territory where 
libraries actually care about what happens. DOM 2 does have 
getElementById. SAX can return the type of an attribute so it needs to 
recognize xml:id at least for that. XPath also has the notion of IDs, as 
does XPointer's shorthand syntax. xml:lang and xml:space just aren't 
that relevant most of the time, and xml:base only marginally more so. 
However, xml:id is diving right into the heart of a lot of XML 
processing. Any problems that already exist with xml:space, xml:lang, 
and xml:base are going to have much more practical impact with xml:id.

Elliotte Rusty Harold  elharo@metalab.unc.edu
XML in a Nutshell 3rd Edition Just Published!
Received on Friday, 22 April 2005 22:57:02 UTC

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