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Re: Using the term "representation" bidirectionally [was Re: the mistake I made! ]

From: Jonathan Rees <jar@creativecommons.org>
Date: Fri, 4 Mar 2011 13:49:27 -0500
Message-ID: <AANLkTinzuyB8BMByv8uXFG5FUFdT0yJB9-Ea8EZ8wvd6@mail.gmail.com>
To: nathan@webr3.org
Cc: David Booth <david@dbooth.org>, AWWSW TF <public-awwsw@w3.org>
Right. I find Roy's new HTTPbis world view kind of silly, but I think
it's consistent so I won't complain about it too much.

When a PUT is transmitted the request contains a representation of
some resource, just usually not the one named by the request URI.
(This is just like the 404 case, where the response carries a
representation of some resource, just not the one requested.) If the
server decides to alter the resource in response to the request, then
the PUT request's representation may *become* a representation of the
resource, as a result. I presume that's what a 2xx response would
mean.

I don't see how this would confuse us or lead to sloppy thinking, as
long as we understand it, and I don't think that's too hard.

Jonathan

On Fri, Mar 4, 2011 at 1:32 PM, Nathan <nathan@webr3.org> wrote:
> David Booth wrote:
>>
>> Sorry, I'm a little behind on these messages, but trying to catch up.
>> Comments below.
>>
>> On Tue, 2011-03-01 at 08:01 -0500, Jonathan Rees wrote:
>>>
>>> On Tue, Mar 1, 2011 at 5:13 AM, Nathan <nathan@webr3.org> wrote:
>>
>> [ . . . ]
>>>>
>>>> Why reflects? well it's reflects because in the case of GET
>>>> representations
>>>> can be conneg'd, subject to the capabilities of the agent, over
>>>> language,
>>>> auth*, or media type or suchlike - hence "which are equivalent" - and in
>>>> the
>>>> case of PUT, it's reflects because you may PUT a jpeg but the server
>>>> will be
>>>> able to send back the same image in gif or png or a different size.
>>
>> In HTTP-bis Roy is using the word "representation" both as something
>> that comes *from* a resource and as something that can be sent *to* a
>> resource (e.g., in a PUT request).  I first noticed this a few months
>> ago and it made me uncomfortable because I think it is easier to talk
>> about representations as things that you GET from (information)
>> resources, but not the other way around (PUT).
>
> Ahh, there are two forms of "representation"
>  - "representation" (content+meta, bound to an anonymous resource)
>  - "resource representation" (content+meta, bound to the identified
> resource)
>
> s/bound to/associated with.
>
>   A "representation" is information in a format that can be readily
>   communicated from one party to another.  A "resource representation"
>   is information that reflects the state of that resource, as observed
>   at some point in the past (e.g., in a response to GET) or to be
>   desired at some point in the future (e.g., in a PUT request).
>
> see here http://webr3.org/http-combinations.txt for a list of when the
> "representation" is a "resource representation"
>
> do keep going though, there's a bit to catch up on, possibly worth reading
> in the reverse direction (newest first)
>
>
Received on Friday, 4 March 2011 18:50:05 GMT

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