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Re: [httpRange-14] empiricism was Re: resources and URIs

From: Dan Connolly <connolly@w3.org>
Date: 21 Jul 2003 10:17:30 -0500
To: Jonathan Borden <jonathan@openhealth.org>
Cc: pat hayes <phayes@ihmc.us>, www-tag@w3.org, Pat Hayes <phayes@ai.uwf.edu>
Message-Id: <1058800650.618.29.camel@jammer.dm93.org>

On Wed, 2003-07-16 at 21:49, Jonathan Borden wrote:
> Dan Connolly wrote:
> >
> > On Tue, 2003-07-15 at 18:20, pat hayes wrote:
> > > Gentlemen, I would like to ask you to please clarify the meaning of
> > > the terms 'resource' and 'representation' in
> > > http://www.w3.org/TR/2003/WD-webarch-20030627/.
> >
> > It seems to me that your request is pretty much a request
> > to resolve the httpRange-14 issue.
> >   http://www.w3.org/2001/tag/ilist#httpRange-14
> Yup. Since we are talking about the Web as it currently exists, I wonder if
> we can look at some URIs and see what resources they identify.
> http://www.w3.org/1999/XSL/Transform
> http://www.w3.org/2000/svg
> http://www.w3.org/2001/XMLSchema
> Now we have 3 URIs created by the W3C over the course of 3 years. The
> representations obtained on dereferencing the URIs state that these are
> intended to be "XML Namespaces"
> Is it reasonable to say that the resources identified by these URIs are "XML
> Namespaces"?

yes, though the terminology is a little awkward.

> ...
> >
> > >  Other examples abound,
> > > eghttp://chandra.harvard.edu/photo/2003/ngc1068/index.html  is in
> > > clearly about a galaxy containing a supermassive black hole, which is
> > > also not something one would expect to find as part of an networked
> > > information system, given the likely physical constraints on network
> > > architecture.
> >
> > I think that particular identifier refers to a document about
> > a galaxy, not the galaxy itself; if you want to refer to
> > the galaxy itself, you should use a URI with a # in it.
> > [folks with other opinions on httpRange-14 disagree,
> > I believe.]
> >
> I understand this position, you are saying that all HTTP URIs identify
> *documents*, that is to say all resources which are directly 'on the web'
> and who are identified by HTTP URIs are documents.
> How do I reconcile this position with the empirical evidence that some URIs
> identify resources whose representations claim that they are XML Namespaces?
> I just can't reconcile this by accepting that an 'XML Namespace' is a type
> of 'document'.

Why not? It's a little awkward, but as you point out, emperically,
the conclusion follows.

e.g. in the SVG case, when you visit that URI, you're looking
at a representation of a document; it says
  "This is an XML namespace defined in ..."

>  Do you think that the XML Namespaces REC ought be modified to
> deprecate namespace names which are not URI references?

Hmm... you mean suggest that they should have used
http://www.w3.org/2000/svg# as the namespace name?
I hadn't thought of that. I'm not (yet?) convinced
that's the best outcome.

Some thinking out loud...

I'm somewhat persuaded by the argument (from Tim Bray, originally?)
that namespace declarations aren't so much pointers into the information
space as they are a sort of parameter, ala HTML <base> or xml:base
for use in computing URIs... so in order to use them as pointers
into the web, you need some more info about how to compute a URI
from the namespace name; e.g. with xml:base, you use it with
a relative URI reference; in RDF. you concatenate a localname;
and then you have a pointer that somebody meant for you to follow;
i.e. a use, rather than a mention, of a URI.

This is closely connected, in my mind to the Qname->URI mapping issue

My favorite solution to that issue is: to compute a URI from
a namespace name n and a localname l:
  if n.endsWith("#"): uri = n + l
  else: uri = n + '#' + l

But there are more details to fill in for namespaces like XML Schema
that have lots of kinds of local names. My preference is: if you
have a clash, that's too bad. Don't use the same name for two different
top-level constructs.

>  Do you believe the
> Web Architecture ought be documented based on its empirical existence or
> based on a grander design?

Hmm... I kinda think the existence is grander than the design.
But I think Web Architecture ought to be based on both.

Case in point: do you think the HTML 4 spec, published
in 1997, should have encouraged the use of the <font> tag?
After all, emperically, that was the most straightforward
way to get font changes onto PC screens. But there was
a design, present in the code all the way back to 1990,
for using stylesheets. That design is now reasonably
widely deployed, and I think the Web is better for it.

> Jonathan

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Monday, 21 July 2003 11:17:43 UTC

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