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

From: Mark Baker <distobj@acm.org>
Date: Fri, 1 Mar 2002 14:53:36 -0500 (EST)
Message-Id: <200203011953.OAA01546@markbaker.ca>
To: mnot@mnot.net (Mark Nottingham)
Cc: tbray@textuality.com (Tim Bray), www-tag@w3.org (TAG)
> > >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.

I agree with TimBL, but judging by his example, it appears as though
TimB may have misunderstood it.  Negotiating between an XML Schema,
Relax, and DTD representation is an excellent use of conneg, IMO,
because each can be used to represent a resource that defines some
syntactic constraints on an XML document.

> 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 can't see any problem with that.  More below.

> 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.

Oops, should have read this first.  Right.

> 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.

I don't believe "information contained" is a good criterion.  Some
content formats are very general (e.g. most image formats, HTML), others
very specific (e.g. MathML, HRXML).  I think that in general, most
resources can only be represented by one "class" of specific
representation, but by an arbitrary number of general formats.  For
example, a formula could be represented by MathML and any MathML-like
format, but also any general format like images (the formula as a
picture), HTML or plain text (the formula as prose), etc..

Mark Baker, Chief Science Officer, Planetfred, Inc.
Ottawa, Ontario, CANADA.      mbaker@planetfred.com
http://www.markbaker.ca   http://www.planetfred.com
Received on Friday, 1 March 2002 14:49:54 UTC

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