W3C home > Mailing lists > Public > uri@w3.org > January 2002

Re: Some recent Internet Drafts relating to URIs

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Thu, 17 Jan 2002 10:47:24 +0200
To: URN <urn-ietf@lists.netsol.com>, URI <uri@w3.org>
Message-ID: <B86C5C3C.BBD6%patrick.stickler@nokia.com>
On 2002-01-16 16:31, "ext Michael Mealling" <michael@neonym.net> wrote:

> ... The thing that has become clear is that
> a given URI's characteristics have more to do with how it is used than
> what its scheme says.

I hardly consider that something that is "clear" or true.

Take the simple example of the identity of a thing versus
the identity of the representation of a thing, where that
thing itself is not a digital resource, e.g. a car.

The "use 'http:' URLs for everything' approach suggests
that a given URL can be used both to denote the thing
(the car) as well as be dereferenced to retrieve a
representation of that thing (e.g. a photo, or technical
specs, etc.) 

Yet, a SW application which is trying to "understand"
a given statement such as

   <rdf:Description rdf:about="http://foo.com/freds_car/">

cannot tell whether Fred is the creator of the car itself
or of the digital resource retrievable from the URL.

Likewise, if the URL is intended only to be a URT -- i.e.
to be a non-dereferencible identifier of a non-digital
resource (just the car), an application has no way of
knowing if a 404 error is a true error (i.e. it *should*
resolve to "something") or just a side effect of the use
of a URL as a URT.

This degree of chaos in the interpretation of URIs is
IMO completely unacceptable and will greatly hinder the
advancement and deployment of useful SW applications.

Far better would be

   <rdf:Description rdf:about="http://foo.com/freds_car.jpg">
      <rdfs:description>Picture of Fred's Car</rdfs:description>

   <rdf:Description rdf:about="voc://foo.com/freds_car">
      <rdfs:description>Fred's Car</rdfs:description>
      <rdfs:seeAlso rdf:resource="http://foo.com/freds_car.jpg"/>

and an application knows, based on the defined semantics of
'http:' URLs that it should get "something" when it dereferences
the URL and knows, based on the defined semantics of 'voc:'
URTs that it should not dereference one but use it simply as a
global identifier.



Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Thursday, 17 January 2002 03:46:36 UTC

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