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Re: Documents, Cars, Hills, and Valleys

From: Mark Nottingham <mnot@mnot.net>
Date: Wed, 10 Apr 2002 12:57:43 -0700
Cc: <www-rdf-interest@w3.org>, Tim Berners-Lee <timbl@w3.org>
To: "Sean B. Palmer" <sean@mysterylights.com>
Message-Id: <38547E76-4CBD-11D6-B12D-000A27836A68@mnot.net>
My .02 -

I'm on the Car side. The URI identifies a thing, whether it be document, 
car, or doomsday device. You manipulate and view it with things that you 
might call 'documents' (although I prefer Jeff Mogul's attempt [1] at a 
more precise terminology).

Otherwise, what are CGI/ASP/JSP/CFM/PHP/XSLT/etc. scripts? They're 
clearly not just identifying documents; they're interpreted on the 
server, and involve state that often doesn't reside in those "documents."

People are a bit more difficult, yes, but some form of gateway should do 
the trick, even if it only involves levers, lights and food pellets.

[ As such, gateways act as a form of information hiding; when you access 
them, you're accessing a constrained interface to the identified thing, 
rather than the thing itself. I don't think this introduces a problem, 
though, because HTTP itself is a constraining interface. ]

All of this said, I think it generally bad practice to say
   <http;//www.mnot.net/> a :Person .
but instead, it's better to say
   [ :homepage <http://www.mnot.net/> ] a :Person .

Because AFAIK all homepages *are* documents or scripts or some other 
form of machine-based state, not gateways to people (counterexamples 
gratefully accepted). This situation, however, shouldn't be used to 
justify a restrictive characterisation of the resources which happen to 
be identified with the scheme 'http'.

It may be interesting to look at other schemes and see how they restrict 
what is identified. From what I can see, schemes which can be 
dereferenced - whether it be imap, ftp or tel - tend to restrict how you 
access something, rather than define what something is. A 'tel' URI 
might identify a person, an answering machine, or dial-a-date.

On that point, I'm a bit surprised that TBL advocates the document view 
(or perhaps I just misunderstand the framing of the issue). The axiom of 
universality [2] dictates that "The Web works best when anything of 
value and identity is a first class object." Part of the test of 
independent invention [3] says that it should be possible to gateway new 
systems into old ones (e.g., the Person Identity Protocol into HTTP). 
Taken together, these arguments evoke more than 'document.'

2. http://www.w3.org/DesignIssues/Axioms.html#uri
3. http://www.w3.org/DesignIssues/Evolution.html#ToII

Mark Nottingham
Received on Wednesday, 10 April 2002 15:57:45 UTC

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