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Re: Subgroup to handle semantics of HTTP etc?

From: Xiaoshu Wang <wangxiao@musc.edu>
Date: Mon, 22 Oct 2007 15:56:13 +0100
Message-ID: <471CBA0D.9020102@musc.edu>
CC: Alan Ruttenberg <alanruttenberg@gmail.com>, Dan Connolly <connolly@w3.org>, "Booth, David (HP Software - Boston)" <dbooth@hp.com>, Jonathan A Rees <jar@mumble.net>, "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>, Tim Berners-Lee <timbl@w3.org>, W3C-TAG Group WG <www-tag@w3.org>

noah_mendelsohn@us.ibm.com wrote:
> Xiaoshu Wang writes:
>> Hmm.. not really.  I think AWWW's opinion is that for some resource,
>> i.e., the information resource, T=R.
> If that were the case, then why would we allow content negotiation 
> based on media-type, language (French, English, Chinese, etc.)?  
> Furthermore, I think it's pretty well accepted that a 200 is an 
> acceptable status code for a GET to a clock resource.  With such a 
> resource we can see that the same URI (http://example.com/clock)  
> returns different representations each time it's accessed.   I find 
> that a useful example to motivate the distinction between an 
> information resource and its representation(s).
Honestly, after httpRange-14, I don't think that many people will 
consider it O.K. to 200 back a "clock" anymore.  Just like we, I 
included, are trying to tell people that it is not O.K. to 200 back a 
string of letters for a protein's URI.
> Furthermore, to reiterate the point about content negotiation, I think 
> it would be quite acceptable for that clock to return a string like 
> "10:03 AM EDT October 23, 2007" if asked for text/plain, but to return 
> the image of a suitable clock face if asked for image/jpeg.  All of 
> these illustrate the lack of one-to-one relationship between an 
> information resource and its representations, at least in the general 
> case.
I think from this wording in AWWW - "The distinguishing characteristic 
of these resources is that all of their essential characteristics can be 
conveyed in a message", the implication, at least for me, is that "from 
the representation of an information resource, we can *fully* understand 
the resource".

The point that I want to stress is: from a particular representation, 
you can only know *a part* of what the URI identifies and we cannot tell 
how big the part is from its URI or its network response code.

This, in my opinion, makes the distinction between IR and non-IR 
pointless. Because as you said, the relationship between representation 
and an information resource is not one-to-one. Thus, if we cannot tell 
how much the "representation" represents the "information resource", 
then how to differ an IR from a non-IR? Then, who should get 303 and who 
should not?

Received on Monday, 22 October 2007 14:56:54 UTC

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