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

From: Tim Berners-Lee <timbl@w3.org>
Date: Wed, 26 Dec 2001 17:56:59 -0500
Message-ID: <028d01c18e60$a0c898b0$f8061812@CREST>
To: "Mark Nottingham" <mnot@mnot.net>, "Jonathan Borden" <jborden@mediaone.net>
Cc: "Dan Brickley" <danbri@w3.org>, "Sean B. Palmer" <sean@mysterylights.com>, "Dan Connolly" <connolly@w3.org>, <www-rdf-interest@w3.org>
cwm has  string:startsWith  which you can combine with log:uri to get this
effect for that example

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


Yes, a full URI parsing would of course be very interesting - kutgw Mark.
For example, it would allow one to write the rules for
a web server, or write rules to interpret the httpd.conf file or equivalent.

Tim

----- Original Message -----
From: "Mark Nottingham" <mnot@mnot.net>
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>
Sent: Wednesday, December 26, 2001 4:42 PM
Subject: Re: aboutEachPrefix? was Re: Namespaces wihtout "#" Was: Few CWM
Bugs


>
> 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 17:57:22 GMT

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