Why namespaces?

[Arjun Ray]

On Thu, 2 Sep 1999, Edd Dumbill wrote:
> On Thu, Sep 02, 1999 at 02:58:54AM +0100, Mark Birbeck wrote:
> > [James Tauber:]

> > > Namespaces (by my reading of the spec) are for distinguishing
> > > element/attribute vocabularies *within an instance*.
> > 
> > Not so. [...]  Namespaces (by my reading of the spec) are for
> > distinguishing element/attribute vocabularies *within the whole world*.

The first view is a straightforward reading of the first two paragraphs of
the XML Namespace spec's "Motivation and Summary".  The second view is a
straightforward reading of the third paragraph.  The basic problem is that
the statement "document constructs should have universal names" is a
(IMHO, whopping) non-sequitur. 
 
> The namespace URI reference identifies the namespace.  So, yes,
> namespaces can be used to distinguish vocabularies globally, put
> prefixes can't. 

Yes, except for the unstated agendas for reserved names that might be
lurking:)

> Therefore implementations shouldn't assume anything from a prefix, 

Something tells me that, unfortunately, this is precisely what some
implementors would like to do, and therefore some implementations will
wind up doing.

> It is clearly a goal of XHTML to allow inclusion of other XML namespaces
> in a document, therefore XHTML ought to define the namespace within
> which it sits.  

But why now?  What's the rush?

> So, if a namespace does indeed == a schema then we need three of them.
> 
> The implication of this to me seems to be nothing less than the ultimate
> replacement of the DTD declaration by the namespace declaration.

A lot of this - actually, to my mind, all of this - seems to be the cart
before horse.  Personally, I consider XML-ization of HTML a bad idea, so I
really don't care how many angels have to dance on the head of this pin. 
But it was my understanding that modularization of HTML was an integral
part of the XML-ization, so I can't see why that activity - important in
its own right - has been shunted into the background for the sake of an
ill-defined, easily-misunderstood will-o'the-wisp add-on.

Put it this way: who are the implementors who have declared that no
immediate decision on namespaces is a show-stopper?


Arjun




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