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Re: The range of the HTTP dereference function

From: Aaron Swartz <me@aaronsw.com>
Date: Tue, 19 Mar 2002 10:25:43 -0600
To: Tim Berners-Lee <timbl@w3.org>
CC: <www-tag@w3.org>
Message-ID: <B8BCC2A7.2A0C4%me@aaronsw.com>
[ sorry... mail client sent instead of pasted...aaargh!]

On 2002-03-19 8:50 AM, "Tim Berners-Lee" <timbl@w3.org> wrote:

> Here is my argument the HTTP URIs (without "#") should be understood as
> referring to documents, not cars.

Just looking for trouble, eh? ;-)

I'd be interesting to see quotes from the HTTP spec to support this, because
everything I've read indicates otherwise.

[on using HTTP URIs to represent things like cars]
> - This is not what people do at the moment.

To the contrary, people say things like:

Who's <http://www.w3.org/People/Berners-Lee/>?
Oh, that's Tim, he's Director of the W3C.

What's at <http://www.apple.com/imac/>?
Oh, that's the new iMac.
 
> - The properties of HTTP are useful to know, and to be able
> to infer things from.  For example, if I ask
> { <telnet://telnet.example.org> log:contents ?x } -> { ?x a :Interesting }.
> then software would be allowed to infer, from the fact that a telnet URI is
> involved that there will be no defined contents.

Sure, perhaps this is true of generic telnet URIs, but the HTTP spec makes
very clear that an HTTP URI can identify anything.
 
> Why do you want to extend the range of http URI dereference to cars?

We don't want to extend it -- it already is that way!
 
> http2://www.w3.org/foo could be defined to have return codes
> "Here is the contents of x which is a document" and "Here is some
> information about x"
> so that as a superset of HTTP it could provide a space in which
> abstract objects existed.
> 
> But http1.1 does not have that and that fact is a useful one to record, I
> think

No, it does. Take for example the 200 code:

"""
10.2.1 200 OK

   The request has succeeded. The information returned with the response
   is dependent on the method used in the request, for example:

   GET    an entity corresponding to the requested resource is sent in
          the response;
""" - http://www.ietf.org/rfc/rfc2616
      R. Fielding, J. Gettys, J. Mogul. H. Frystyk, L. Masinter, P. Leach,
      T. Berners-Lee

Now, we can argue what "corresponding" means, but Roy Fielding has been
pretty clear on the subject:

"""
The early Web architecture defined URI as document identifiers. [...]
However, this definition proved to be unsatisfactory for a number of
reasons. 
[...]
REST [fixes] this by defining a resource to be the semantics of what the
author intends to identify, rather than the value corresponding to those
semantics at the time the reference is created. It is then left to the
author to ensure that the identifier chosen for a reference does indeed
identify the intended semantics.
""" -http://www.ics.uci.edu/~fielding/pubs/dissertation/evaluation#sec_6_2_1
     R. Fielding
 
> In this way, Resource in URI and Resource in RDF can be similarly anything,
> but we have an important concept of a <part of the Web information space>
> <document?> or whatever.

I'm not sure really how important this concept is. Do you have a clear
definition of it, and how it differs from things like cars?

All the best,
-- 
[ "Aaron Swartz" ; <mailto:me@aaronsw.com> ; <http://www.aaronsw.com/> ]
Received on Tuesday, 19 March 2002 11:25:45 GMT

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