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Re: [namespaceDocument-8] 14 Theses, take 2

From: Tim Berners-Lee <timbl@w3.org>
Date: Mon, 4 Mar 2002 16:14:48 -0500
Message-ID: <01f001c1c3c1$9e00c6c0$84001d12@w3.org>
To: "Mark Nottingham" <mnot@mnot.net>, "Tim Bray" <tbray@textuality.com>
Cc: "TAG" <www-tag@w3.org>

----- Original Message ----- 
From: "Mark Nottingham" <mnot@mnot.net>
To: "Tim Bray" <tbray@textuality.com>
Cc: "TAG" <www-tag@w3.org>
Sent: Thursday, February 28, 2002 4:44 PM
Subject: Re: [namespaceDocument-8] 14 Theses, take 2


> 
> On Thu, Feb 28, 2002 at 11:26:24AM -0800, Tim Bray wrote:
> > >6. Where content negotiation is used, it should only be used to
> > >negotiate between documents which really are equivalent - they
> > >basically say the same thing in a different language.  For
> > >example, it would not be appropriate to give and RDF schema and
> > >XML schema for a namespace because they really contain different
> > >information, and a machine or human would be fooled into thinking
> > >it knew the import of a document, when really it had been given
> > >something different.
> > 
> > Good catch.  I had envisioned people saying "get me a schema"
> > and saying whether they wanted XSD or Relax or DTDs via 
> > content-negotiation.  I guess that would be unsound.  -Tim
> 
> I'd be interested to hear TBL's (and maybe MarkB's; think resource
> modeling ;) response to this; it seems a little closer to a (somewhat
> fuzzy) line.
> 
> jpg vs. gif is clearly appropriate for conneg; I don't think many
> would dispute text/plain vs. text/html (in most cases). What about
> jpg vs. gif vs. SVG? 
> 
> I agree that there's a clear distinction between RDF Schema and XML
> Schema; I'm less sure that there is between XSD, Relax and DTD.
> 
> I think the overriding principle, from a URI perspective, is to give
> each thing that needs identity a URI. One can do conneg when there
> are a number of roughly equivalent (in information contained). These
> are somewhat orthoganal; one can do conneg and have only one URI,
> one can do conneg as well as have many URIs for the different
> representations, and one can just have a bunch of URIs.

Well summarized.  The only thing I would add is that it
is up to the publisher, who owns and allocated the URI,
to say, idealy with metadata, what sort of identity holds
for it.  This is why groups getting W3C URIs for namesapces have to
chose and commit to a persistent policy. For generic URIs,
metada can be used to express the invariants one can expect.
For semantic web documents,one can actually express that
the semantics of one might be a subset of the semantic of the
other, of course.

> Back to the immediate subject, though, using a directory format is
> basically doing agent-driven negoatiation anyway.

Yes ... with the extra turnaround time whose avoidance
 was originlly an HTTP requirement.

> Mark Nottingham
> http://www.mnot.net/
>  
> 
Received on Monday, 4 March 2002 16:16:00 GMT

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