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

From: Mark Nottingham <mnot@mnot.net>
Date: Fri, 4 Jan 2002 16:21:36 -0800
To: Jonathan Borden <jborden@mediaone.net>
Cc: Tim Berners-Lee <timbl@w3.org>, www-rdf-interest@w3.org
Message-ID: <20020104162135.B30252@mnot.net>

As I understand it, opacity is important to ensure that third parties
like protocol designers and application vendors don't impose
structure or semantics onto Web publishers' URI namepaces, and also
so that resource metadata wouldn't be conflated with the resource
identifier.

However, as Tim points out, there are situations where the authority
for a resource can infer things about it, based on characteristics of
a URI; this is very useful. Otherwise, how would a Web server know
that the URI http://www.example.com/images/foo.gif should be mapped
to the file at /www/example/htdocs/images/foo.gif. Similarly, the Web
server needs a mechanism to decide what Content-Type to send with the
representation; an efficient way to do this is to look up the
filename extension in a local map. In both cases, the namespace is
fully under the control of the authority; they're using the structure
they've defined as a convenience.

Allowing RDF to peek inside URIs will allow publishers to makes
statements about their URIs without enumerating each and every
resource that they publish (difficult, if not impossible, considering
things like queries). Of course, I could abuse this facility and make
statements about *your* resources, but determining trust is fairly
straightforward, at least for URLs. ;)

Cheers,



On Fri, Jan 04, 2002 at 03:30:48PM -0500, Jonathan Borden wrote:
> Would this break your "opacity axiom"?
> 
> http://www.w3.org/DesignIssues/Axioms.html#opaque
> 
> Axiom: Opacity of URIs
> The only thing you can use an identifier for is to refer to an object. When
> you are not dereferencing you should not look at the contents of the URI
> string to gain other information.
> 
> 
> Jonathan
> 
> > 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
> >
> 
> 

-- 
Mark Nottingham
http://www.mnot.net/
 
Received on Friday, 4 January 2002 19:21:38 GMT

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