Namespace URI address resources

[David Brownell]

Murray Maloney wrote:
> 
> At 09:17 AM 6/14/99 -0700, David Brownell wrote:
> >That'd be true if the URI in namespaces were used for any purpose
> >other than being a unique identifier.  But it isn't; there's no (!!!)
> >requirement that the URI point to anything, and any code that tries
> >to associate the namespace with the results of resolving that URI is
> >going beyond what the XML Namespace spec allows.
> 
> Beyond Namespaces. Catchy title. Good idea.

Necessary!  The namespaces spec solves only one of the
many problems that need solving ... ;-)


> The 'Namespaces in XML' quite rightly limited itself to identifiers.
> 
> There is nothing preventing another spec -- say XML Schema -- from
> leveraging namespace identifiers and adding mechanisms to allow
> resolution of associated resources, is there?.

Subject to some constraints -- nothing prevents that.  For example it'd
be fine for one schema system to be able to to a say which namespace
identifiers point to additional information ... but it'd be wrong
(conflicting with the namespace spec!) to do so for any namespaces
that's not explicitly declared to work that way.  Example:

    <mydoc xmlns="URI-1">
      <schema xmlns="URI-2" fetch-from="URI-1"/>
      <otherstuff xmlns="URI-3">
	...
      </otherstuff>
      ...
    </mydoc>

The semantics of the "URI-2" namespace URI would define what that
"schema" element, and its "fetch-from" attribute, means.  It could
declare that its "fetch-from" attribute value (URI-1 in this example)
associates resources withsome namespace URI.  But that wouldn't apply
in the case of URI-3, unless the URI-1 schema declared that's how the
URI-3 namespace worked.

Yes, I'm assuming a multiplicity of schema systems ... and even that
many schemas would allow for mixing content they don't control.  I
think both are inevitable/essential.

- Dave

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