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Re: URIs for Concepts: Best Practices

From: David Menendez <zednenem@psualum.com>
Date: Fri, 23 Apr 2004 01:51:36 -0400
To: Kal Ahmed <kal@techquila.com>
Cc: "Miles, AJ (Alistair)" <A.J.Miles@rl.ac.uk>, "'public-esw-thes@w3.org'" <public-esw-thes@w3.org>, "'public-esw@w3.org'" <public-esw@w3.org>
Message-id: <r02000200-1033-48E506C394EA11D8AF23000393758032@[]>

Kal Ahmed writes:

> On Mon, 2004-04-19 at 22:22, David Menendez wrote:
> > 
> > It would be confusing for a URI to identify a thesaurus concept and
> > an RDF file. The key, as I see it, is the idea that the response to
> > an HTTP Get is a representation of the resource, not the resource
> > itself. The fact that <http://xmlns.com/wordnet/1.6/Dog> returns an
> > RDF/XML document, doesn't mean that it identifies that particular
> > document. If, for some reason, you wanted to talk about that
> > RDF/XML document instead of the word "Dog", you would need to use a
> > blank node or a different URI.
> > 
> It is certainly true that content negotiation gives you the problem of
> talking about the descriptive resource as opposed to the described
> thing. That is a strong argument against content negotiation for RDF /
> XTM resources.

I've always felt content negotiation was more of an opportunity than a
problem. :-)

If I'm reading you right, in the case of
<http://xmlns.com/wordnet/1.6/Dog>, the "described thing" is the class
"Dog", and the "descriptive resource" is the RDF/XML document returned
if you do an HTTP Get.

The REST view, as I understand it, is that the URI denotes the class
"Dog". Since you can't actually transmit a class over the internet, any
attempt to GET that URI will result in (1) a 404 or similar error, or
(2) a representation of the class "Dog", which could be one of many
possible electronic documents which is selected according to
negotiation. All of these representations are themselves distinct
resources, even if they have no explicit URI (that is, they are blank
nodes). Some versions of HTTP include a Content-Location header, which
gives a URI for the particular representation being returned.

In that case, I would actually recommend content negotiation for RDF
terms. If I put <http://xmlns.com/wordnet/1.6/Dog> into my web browser,
I'd rather get a human-readable HTML document than a bunch of RDF. If my
RDF software GETs the same URI, it should get an RDF document.

In both of those cases, the goal is to find information about the class
"Dog". We don't care as much (or at all) about the representation which
conveys that information.

> > Not everyone agrees with this position.
> > 
> I don't think that a position can ever be established which everyone 
> will agree with :-)

I think we'd all agree to that. :-)
David Menendez <zednenem@psualum.com> | "In this house, we obey the laws
<http://www.eyrie.org/~zednenem>      |        of thermodynamics!"
Received on Friday, 23 April 2004 01:51:43 UTC

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