xml-dev - Re: Namespace URI address resources

[David Brownell <david-b@pacbell.net>]

"W. Eliot Kimber" wrote:
> 
> Didier PH Martin wrote:
> 
> > Didier says:
> > Exactly. A URI represent something. It is a U_niform R_esource I_dentifier.
> > It provides identitity to a resource.
> 
> No, a URI does *not* provide identity to a resource--it *identifies* a resource,
> but it does not provide identity for the resource. That is, given two different
> URIs, you cannot know, from the URIs alone, whether they identify the same
> resource or a different resource. 

True enough ...


> Unless the URI *is* the resource, it does not establish identity of the resource
> it addresses.

Which is the case in XML namespaces, by reading from me and others.  There
is explicit language in the specification saying that "It is not a goal
that it be directly usable for retrieval of a schema (if any exists)."
Any resource identified by the URI doesn't matter at all.

The only characteristics required of that URI are "uniqueness and
persistence" ... NOT ability to actually retrieve a resource it may
identify (largely disclaimed by the non-goal quoted above) or to be
equated with some other URI for comparison purposes (which may be a
fine idea but isn't required by the spec).


> And note that identity can only be truly established at a specific point in
> time. The same URI resolved at two different points in time may resolve to
> provably different resources.

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.

- Dave

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