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Re: Uniform access to descriptions

From: Xiaoshu Wang <wangxiao@musc.edu>
Date: Fri, 11 Apr 2008 14:26:07 +0100
Message-ID: <47FF66EF.3030409@musc.edu>
To: noah_mendelsohn@us.ibm.com
CC: Jonathan Rees <jar@creativecommons.org>, Phil Archer <parcher@icra.org>, Pat Hayes <phayes@ihmc.us>, "Williams, Stuart (HP Labs, Bristol)" <skw@hp.com>, "www-tag@w3.org WG" <www-tag@w3.org>

noah_mendelsohn@us.ibm.com wrote:
> Xiaoshu Wang writes:
>> HTTP protocol is a transportation protocol.
>> Hence, the semantics of HTTP should be ALL about delivering 
>> message and its parsing and it should have nothing to do with 
>> judging its content. 
> Hmm.  I would have said that HTTP is an application-level protocol. 
> Otherwise, why distinguish PUT from POST or DELETE?  What they transport 
> isn't much different, except that with delete there is seldom need for 
> much information beyond the identifier of the resource.  If it were just a 
> transportation protocol, then all we would need is well typed messages, 
> and we could encode operations in those messages if we wished to.  I'm not 
> sure I'd use your phrase "judging its content", but HTTP operations are 
> applied to Web resources, and the status codes properly reflect 
> information about that interaction.  The fact that certain operations 
> cannot be successfully performed on certain classes of resources, and that 
> the status codes therefore (if properly used) allow one at times to infer 
> information about the nature of the resources, all seem fine to me.  If we 
> were talking about TCP, I would for the most part agree with you.
I think this is the essential issue of all argument is.  As Stuart 
warned me not to loop the concepts again and again.  Let's reformulate 
the argument into a multiple choice question.

Question 1: Is there a difference between Representation and Resource?
(1a): Yes.  Representation -> Resource; (here let's name "->" as identify).
(1b): No.  Representation = Resource.

Question 2: Can one resource has multiple Representation?
(2a) Yes.  So Representation -> Resource but Representation != Resource.
(2b) No.  (Then explain or drop Conneg)

Question 3: What does a URI denote?
(3a): Resource.
(3b): Representation
(3c): Both.

Question 4: Is an HTTP-URI =  HTTP+URI?
(4a): No.  (Hence, HTTP-URI = Resource, HTTP+URI = Representation.)
(4b): Yes.

My answer is all (a), which is consistent and without any ambiguity.  If 
someone propose any model other than (a), then find a model to make them 
all consistent.  It is their burden to model it consistently, not mime.

All other questions, such as what is the meaning of "description" should 
be answered based on the answers of the above four questions.  I think 
they summarize different attitudes toward the architecture of the web.


Let's settle this first and then with some terminology.

Received on Friday, 11 April 2008 13:26:56 UTC

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