W3C home > Mailing lists > Public > www-rdf-interest@w3.org > August 2000

Re: [Fwd: xmlns, uri+name pairs or just uris..? Clarification needed.]

From: Dan Brickley <Daniel.Brickley@bristol.ac.uk>
Date: Fri, 11 Aug 2000 10:56:01 +0100 (BST)
To: Pierre-Antoine CHAMPIN <champin@bat710.univ-lyon1.fr>
cc: "McBride, Brian" <bwm@hplb.hpl.hp.com>, www-rdf-interest@w3.org
Message-ID: <Pine.GHP.4.21.0008111037010.25066-100000@mail.ilrt.bris.ac.uk>
On Fri, 11 Aug 2000, Pierre-Antoine CHAMPIN wrote:

> "McBride, Brian" wrote:
> > In that case I would be troubled about what the URI Ref that
> > names a property actually names.  Does it name the property
> > or does it name the document/document fragment that describes
> > the property.  The foundation of the web is that URI's denote
> > one resource;
> 
> That is exactly the point, IMO :
> the document/document fragment describing a property is *not* the property, and they should not be mandated to have the same URI (though I admit this is a very practical way of naming properties...)

This used to bother me a lot, until I came to a more abstract view of
what something like http://www.w3.org/Icons/w3c_main is a name for.
Or something like http://example.com/xmlns-evocab/v1. 

It's a 'thing known to the Web' that can expose different renderings of
itself according to contextual circumstance. Eg. if I send it a 'GET'
HTTP message today, with a certain bundles of
content-negotiation preferences, authentication information etc., it'll
respond with a mime-typed bunch of bytes that presents one view of
itself. You never get the actual Web thing itself, only
views/renderings of it. Conceptually, the Web thing
http://www.w3.org/Icons/w3c_main isn't
intrinsically a PNG, GIF, JPEG or SVG, but can render these views of
itself when asked. 

I believe the same point holds for Web data vocabularies, whether
they're XML, RDF, PICS or P3P data schemas. They have a name on the Web,
and typically (dereferencing being a privilege not a right...) they'll
present useful views of themselves in response to HTTP 'GET' messages.

The Namespace URI then names the property in the abstract, but when we
send a 'GET' to the Web service that knows authoritatively about that
URI, we'll get back a (possibly content-negotiated) document that
presents some view of the abstract resource. Just like doing a GET to
the Web service that knows authoritatively about some 'visual image'
resource.


So, having come to this view, I'm now only a bit bothered by
the apparent wierdness. Semantics of '#' still concern me though (in
general, not just for RDF). 

Dan


ps. the old HTTP-NG work describes this issues quite nicely:
http://www.w3.org/TR/WD-HTTP-NG-interfaces/

When we think of the Web today, the idea of a 'resource' comes to
mind. In general, a resource is an Object that has
some methods (e.g. in HTTP, Get Head and Post) that can be invoked on
it. Objects may be stateful in that they
have some sort of opaque 'native data' that influences their
behavior. The nature of this native data is unknown to
the outside, unless the object explicitly makes it known somehow. [Any
stateful object may or may not have some
means by which it stores persistent state across activations, but that's
not really part of our concern here.] 
Received on Friday, 11 August 2000 05:56:38 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:51:43 GMT