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Re: aboutEachPrefix? was Re: Namespaces wihtout "#" Was: Few CWM Bugs

From: Mark Nottingham <mnot@mnot.net>
Date: Wed, 26 Dec 2001 13:42:16 -0800
To: Jonathan Borden <jborden@mediaone.net>
Cc: Tim Berners-Lee <timbl@w3.org>, Dan Brickley <danbri@w3.org>, "Sean B. Palmer" <sean@mysterylights.com>, Dan Connolly <connolly@w3.org>, www-rdf-interest@w3.org
Message-ID: <20011226134209.A20346@mnot.net>

I've been playing with a means of deconstructing URIs so that one can
define rules about them in a much more fine-grained manner. Roughly,
what you'd like to do might look like:

{ ?x log:uri [ uri:scheme "http" ] }
  log:implies
  { ?x a :Document } .

(there's some thought of pointing at the list of URI schemes at
w3.org, rather than a literal, to identify the scheme, but you get
the idea, hopefully).

I have a CWM module that does uri:scheme. It gets more interesting
when you can break down the path into segments, etc., and test for
properties of the authority, but it's not there yet.

Cheers,



On Wed, Dec 26, 2001 at 01:41:01AM -0500, Jonathan Borden wrote:
> It seems to me that in order to say something like this in RDF we
> really do need the "aboutEachPrefix" construct, in which case one
> can:
> 
> <rdf:Description rdf:aboutEachPrefx="http:">
>     <rdf:type rdf:resource="...#Document">
> </rdf:Description>
> 
> unfortunately it has been removed from the current RDF syntax. Can
> one state this using the current RDF? What I am looking for is an
> unambiguous, machine processable, mechanism for knowing types and
> other properties of URI subspaces (now that URIs are not opaque --
> which is fine)
> 
> Jonathan
> 
> 
> > True.  A resource for a non-HTTP space can be whatever that URI
> > space says it is.  It is just HTTP which really creates a world
> > of documents.
> >
> > mailto:  for example, defines a space of mailboxes which are not
> > documents. I should have limited what I said to the http: space.
> >
> > Tim
> >
> > ----- Original Message -----
> > From: "Jonathan Borden" <jborden@mediaone.net>
> > To: "Tim Berners-Lee" <timbl@w3.org>; "Dan Brickley" <danbri@w3.org>
> > Cc: "Sean B. Palmer" <sean@mysterylights.com>; "Dan Connolly"
> > <connolly@w3.org>; <www-rdf-interest@w3.org>
> > Sent: Saturday, December 22, 2001 10:39 AM
> > Subject: Re: Namespaces wihtout "#" Was: Few CWM Bugs
> >
> >
> > > Tim Berners-Lee wrote:
> > > > >
> > > > > > The second issue is more significant.   In my worldview,
> > > > > > (which I claim to be (a) consistent and (b) useful)
> > > > > > http://example.org/x is a document.  You can't reuse its
> > > > > > URI for an abstract thing without a change to HTTP.
> > > > >
> > > > > In-principle plausible, although _please_ define "document".
> > > >
> > > > I uyse the term "document" because unfortunately "resource"
> > > > has been used differently in URI and RDF specs.  I mean by
> > > > "document" "resource" as in URI.  DAML uses the term "Thing"
> > > > to mean what RDF terms a resource.
> > >
> > > This is really helpful, yet when I read the RFC 2396 definition
> > > of a resource I don't see how a resource can be _limited_ to
> > > only things which are documents:
> > >
> > > "A resource can be anything that has identity. Familiar
> > > examples include an electronic document, an image, a service
> > > (e.g., "today's weather report for Los Angeles"), and a
> > > collection of other resources. Not all resources are network
> > > "retrievable"; e.g., human beings, corporations, and bound
> > > books in a library can also be considered resources. "
> > >
> > > This language clearly states, to my very best reading, that a
> > > _document_ is a subClass of a _resource_ and a _human being_ is
> > > another subClass of
> > > _resource_. This is why I cannot understand why a plain old URI
> > > (i.e. without fragment identifer) cannot identify a person.
> > > Perhaps you are saying that the _type_ of resource is indicated
> > > by the URI scheme? i.e. that people would be indicated e.g.
> > >
> > > person://smith/joe
> > >
> > > >
> > > > When the content-type is RDF or N3, then a document can be
> > > > used to describe people and planes and ideas.  These can be
> > > > identified (in N3) by using the localname of concept within
> > > > the document as a fragment identifier.  (I think the same
> > > > should be true of RDF/XML).
> > >
> > > Ok, I buy this. Here you say that people, places and things can
> > > be identified by URI References. This still does not solve the
> > > problem that RFC 2396 says what URIs themselves may identify...
> > > >
> > > > >.The distinction is only useful if it can be defined clearly
> > > > > enough to implement to.
> > > >
> > > > Well,  you certianly can't return a person across the net, so
> > > > the distinction is not that fine ;-)
> > >
> > > Again, RFC 2396 explicitly does not limit resources to things
> > > that are network retrievable, so I need more guidance here.
> > >
> > > Perhaps the problem is that many people treat RFCs as axioms
> > > and in trying to understand how 'logic on the Web' will work in
> > > practice, inconsistencies are problematic.
> > >
> > > Jonathan
> > >
> >
> >
> 

-- 
Mark Nottingham
http://www.mnot.net/
 
Received on Wednesday, 26 December 2001 16:42:22 GMT

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