RE: [xml-dev] IDs considered harmful or why keys might be better than IDs...

["Evan Lenz" <elenz@xyzfind.com>]

John Cowan wrote:
> Jonathan Borden wrote:
>
>
> > The only reason that I see the need for something really
> lightweight like
> > "xml:id" is that internal subsets are not well handled by
> common software
> > (e.g. SAX),
>
>
> Actually, SAX is able to report the types of attributes.  There is
> nothing in XML 1.0 requiring XML processors to make this information
> available, however.

I didn't realize that attribute types were not required to be reported, but
that certainly does seem to be the case[1].

> It would be interesting to know which XML processors don't report
> attribute type information for attributes declared in the internal
> subset.

XPath won't work properly with any XML processor that doesn't, so that would
indeed be interesting. It's good to know that SAX provides access to this
information.

Perhaps instead of adding something like xml:id, the next version or errata
or xml-dev RDDL-like effort just needs to tighten up the requirements about
what to report from the internal subset (that would be a short spec for
sure).

Evan Lenz
XYZFind Corp.

[1] "Definition: While they are not required to check the document for
validity, they are required to *process* all the declarations they read in
the internal DTD subset and in any parameter entity that they read, up to
the first reference to a parameter entity that they do not read; that is to
say, they must use the information in those declarations to normalize
attribute values, include the replacement text of internal entities, and
supply default attribute values." (emphasis in original)
http://www.w3.org/TR/REC-xml#proc-types