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Re: In defence of 404 Re: INSEE releases OWL ontology and RDF data ?for geographical?entities

From: Dan Connolly <connolly@w3.org>
Date: Fri, 04 Aug 2006 17:39:01 -0500
To: Bernard Vatant <bernard.vatant@mondeca.com>
Cc: semantic-web@w3.org, Eric van der Vlist <vdv@dyomedea.com>, Franck Cotton <franck.cotton@insee.fr>
Message-Id: <1154731141.30621.105.camel@dirk.w3.org>

On Fri, 2006-08-04 at 23:53 +0200, Bernard Vatant wrote:
> And actually, this should be the general situation in SW publication :
> there is no authoritative, definitive, complete, description of a
> resource, packaged in one file, with a single access point.

Yes, there are authoritative descriptions in the Semantic Web.
Perhaps not complete definitions, but for a URI such
any document you get back by doing an http GET
of http://www.w3.org/2000/01/rdf-schema
is authoritative. That's how the web works: we all agree
that if you lease/buy a domain name, you get to say what
the URIs starting with http:// and that domain mean, and
we agree that if you run a web server and serve up
documents there, they are authoritative w.r.t. the meanings
of those URIs.

Anybody else is free to say things about rdfs:subClassOf,
but the document that W3C serves up at
http://www.w3.org/2000/01/rdf-schema says that rdfs:subClassOf
is an rdf:Property, and is some other document 
says that it's not an rdf:Property, that other document should
be considered in error.

>  So, the best an URI can do, when its referent is not an accessible
> thing, and that its main purpose is identifying the resource in
> distributed descriptions, if one wants to make sense of it through
> http protocol - since it's an http URI after all - is to get acces
> some information like : "Sorry, what you try to access by this URI is
> not an accessible resource. But its description can be found in RDF
> files X, Y, Z, ...".

That's not the best we can do.
If you use URIs of the form DOC#TERM for non-information
resources, then the information resource DOC can
say things like { <#TERM> rdf:type geo:City }.

>  And the more I think about it, the more I think that the 404 page
> that you get through http://rdf.insee.fr/geo/COM_80078 is close to
> that. Agreed, the current message displayed on the page is suboptimal,
> independently of the fact that it is in French, but replace it by the
> quote I suggest above, and it makes much more sense that any fragment
> identifier. 

Really? It doesn't appeal to me at all.

> Maybe in contradiction with what I wrote in a previous message, where
> I suggested that maybe we could have kept the # namespace for the
> ontology, I think now that this argument holds for ontology elements
> as well. Granted, we have now published a single ontology file
> containing a description of e.g., http://rdf.insee.fr/geo/Commune. But
> next year we can have another version, or another ontology defining
> the same entity, with the same URI, at another level of detail, and
> which the publisher would not like to see merged with the previous
> one.

Hmm... I can't imagine why not. Care to elaborate?

>  There again, packaging considerations naturally lead to define
> several files containing partial descriptions of the same resource.

It seems very unnatural to me to use anything other than a single
static file for the case of an ontology with just a few dozen terms.
Maybe a handful of content-negotiated static files. But not more than

> I'm well aware this is highly controversial and certainly not in tune
> with the TAG recommendation on httpRange14 issue. 
> Bernard
> [1]
> http://www.ibiblio.org/hhalpin/irw2006/presentations/HayesSlides.pdf

Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Friday, 4 August 2006 22:39:07 UTC

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