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Re: [httpRange-14] What do HTTP URIs Identify?

From: Dan Connolly <connolly@w3.org>
Date: 31 Jul 2002 16:42:48 -0500
To: Tim Berners-Lee <timbl@w3.org>
Cc: Aaron Swartz <me@aaronsw.com>, www-tag@w3.org
Message-Id: <1028151769.21237.2081.camel@dirk>

On Wed, 2002-07-31 at 15:35, Tim Berners-Lee wrote:
[...]
> > > * The HTTP headers
> >
> > Most HTTP headers, as I believe I pointed out in the Expires: example,
> > apply to the entity or representation, not the Resource. I believe those
> > that apply to the Resource work just fine with it being a donkey.
> 
> See section 2.4.  This is the two-level apporach to
> dividing propoerties into those which refer to the web page
> and those which refer to the donkey.

I don't think so. I think that if you want to look at Expires:
as an RDF property, its subject is the response message,
not the resource referred to by the request URI.
i.e. it's not as though he's saying "whenever you
see http:expires, its relationship to it subject
is special/magic". It's just that, when you look
at an HTTP response as a logical formula, the protocol
itself says that the header fields apply to various things.

i.e. if you GET <someDoc>, then you evoke a reponse,
:someReponse. If the response includes a
	Expires: 2002-12-31
header field, then we'd have

  :someResponse http:expires "2002-12-31".

not

  <someDoc> http:expires "2002-12-31".

because if you make <someDoc> the subject of the expires,
then you come back on Jan 1 2003, and you get
	Expires: 2003-02-01

and then you have
  <someDoc> http:expires "2002-12-31", "2003-02-01".
wich is silly/useless. What's useful is to know:

  :someResponse http:expires "2002-12-31";
     http:requestFor <someDoc>.

  :someOtherResponse http:expires "2003-02-01";
     http:requestFor <someDoc>.


the http:date header works that way too.

The http:content-length can be applied to
the response message or, perhaps more usefully,
to its content:

  :someResponse http:date "2002-07-31";
     http:expires "2002-12-31";
     http:requestFor <someDoc>;
     http:body [ http:content-length "4567"].

  :someOtherResponse http:date "2003-01-01";
     http:expires "2003-02-01";
     http:requestFor <someDoc>;
     http:body [ http:content-length "4987"].

But again, it's not useful to apply the
content-length field to the requested resource,
or you get:

  <someDoc> http:content-length "4567", "4987".

which is, again, silly/useless.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
see you in Montreal in August at Extreme Markup 2002?
Received on Wednesday, 31 July 2002 17:42:24 GMT

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