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On Wed, 20 Feb 2002, Tim Bray wrote:
> At 04:03 PM 20/02/02 +0200, Patrick Stickler wrote:
> >Take XHTML for instance. We can talk about the Strict
> >vocabulary, or the Transitional Vocabulary or the
> >Frameset Vocabulary. These are separate functional
> >vocabularies.
>
...
> I think that there are always going to be variations
> and dialects and versions and so on at increasingly
> fine levels of granularity, but by design and for
> the kinds of practical purposes that programmers care
> about, namespaces label vocabularies.
>
> To *completely* identify a markup vocabulary for the purposes
> of every conceivable application would require combining a large
> number of pieces of metadata - talk to anyone who's ever maintained
> processing filters in a complicated publishing application. The
> key finding around namespaces is that for a large number of
> practical purposes, namespaces provide a course-granularity
> way of asserting "this is HTML" or "this is SVG". One
> application of something like RDDL would be to give information
> about different versions and flavors of the vocabulary... hmmm.
>
> >Thus, the XHTML namespace does not equate to a single
> >vocabulary
>
> I think it does, in practical terms.
>
> >Thus, a namespace is not equivalent to a vocabulary. I.e.
> >
> > Namespace != Vocabulary
>
> A namespace doesn't equal a vocabulary, but its primary usage
> is to label one.
>
> >Is that clearer?
>
> Yes, but I don't buy it. -Tim
I came at this issue a while back, trying to understand if it made sense
to use changing namespaces to identify different versions of XML messages
-- I was looking for a best-practice way of tracking message syntax
versions. The consensus was that this was a bad idea -- that doing so with
namespace names would mean massive change managment problems with things
like XSLT transforms, schemas, etc.
There was no clean answer to this question ... RDDL might be one way to do
so, but wouldn't work if you weren't in a position to resolve the namepace
URI....
Ian
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