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- From: james anderson <James.Anderson@mecomnet.de>
- To: XMLDev list <xml-dev@ic.ac.uk>
- Date: Wed, 05 Jan 2000 20:24:44 +0100
hmm..., the thread is becoming rather tenuous, but, if you concur, that
{"","a",""}, which is descibes <... xmlns="" ... > is not the same as {
undeclared, "a", valid-prefix }, then how does the notion of nonconformance
enter into the question re
> > > {"", "a", ""} == {"", "a", "html"}
?
David Brownell wrote:
>
> james anderson wrote:
> >
> > i had understood
> > {"","a",""},
> > from the example, to denote a name in a namespace for which there would have
> > been a declaration, namely a binding such as
> >
> > <... xmlns="" ... >
> >
> > for the ignominious "null" namespace. how does this come to correspond to
> >
> > { undeclared, "a", valid-prefix } ?
>
> It doesn't. Namespace URIs clearly have three kinds of values, not that
> it's specified in the namespace spec very clearly (and I suspect DOM L2
> may need tweaking to get this right):
>
> - Undeclared (null?)
> - Declared as no-value (empty string, "")
> - Some URI (the case folk focus on).
don't they have four?
- Undeclared (not "null"; that term already has a different meaning
in the REC)
- Declared as "no namespace": xmlns=""
- Declares as the empty string: xmlns:html=""
- Some URI (the case folk focus on).
>
> The distinction between "undefined" and "empty" will be familiar to folk
> in the database world (maybe with different terms). SAX2 will have to be
> clear on how it exposes this.
>
> One more edge case for applications to trip over!
>
> - Dave
>
> > i agree that an "==" implementation needs to account for this, but didn't
> > think it was nonconformant.
> >
> > David Brownell wrote:
> > >
> > > David Megginson wrote:
> > > >
> > > > Clark C. Evans writes:
> > > >
> > > > > On Sun, 26 Dec 1999 uche.ogbuji@fourthought.com wrote:
> > > > > >
> > > > > > {"http://www.w3.org/1999/xhtml", "a", ""} ==
> > > > > > {"http://www.w3.org/1999/xhtml", "a", "html"}.
> > > > >
> > > > > {"","a",""} != {"","a","html"}
> > > >
> > > > As I understood it, the suggestion was that
> > > >
> > > > {"", "a", ""} == {"", "a", "html"}
> > >
> > > Actually I think the namespace spec defines
> > >
> > > { undeclared, "a", valid-prefix }
> > >
> > > as "namespace-nonconformant", AKA some kind of error which they
> > > neglected to describe well enough to support portable APIs.
> > >
> > > Meaning that any application choosing to use such a "Name"
> > > class (which IMHO is a fine notion) needs to treat this value
> > > with care ... IEEE floating point math has a variety of sorts
> > > of "NaN" values, perhaps useful models can be found there.
> > > I'd suggest that most "==" tests against such a Name ought to
> > > fail, and ordering tests should cause exceptions.
> > >
> >
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