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Re: part 2, 5.1 "the response payload is a representation of the target resource"

From: Jonathan A Rees <rees@mumble.net>
Date: Fri, 10 Feb 2012 09:28:03 -0500
Message-ID: <CAGnGFMJ_TGReBhERJh=edkQe3yzvT7FEAj1VtQuyVdA_as7U9Q@mail.gmail.com>
To: ietf-http-wg@w3.org
I think my previous email expresses the problem, but should there be
any question, I wrote up the issue in a bit more detail in a blog
post:

http://odontomachus.wordpress.com/2012/02/09/when-identification-and-representation-fight-who-wins/

Best
Jonathan

On Tue, Feb 7, 2012 at 10:08 AM, Jonathan A Rees <rees@mumble.net> wrote:
> The confusion I pointed out in 7.3.4 is also present in section 5.1. We have
>
> http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-18#section-5
>
> "1.  If the response status code is 200 or 203 and the request method
>      was GET, the response payload is a representation of the target
>      resource."
>
> If you mean "representation" in an ordinary-language sense, then the
> status code only *indicates*, it does not *imply*. So we cannot
> conclude that the payload is a representation of the target resource;
> we can only conclude that the server *says* it is a representation of
> the target resource. We would need more information, such as trust in
> the server, to conclude that it actually *is* a representation. (This
> is true even if the server is the origin server.)
>
> In the language of that section, one would say "the response payload
> is a representation *associated with* the target
>      resource [by the server]" - i.e. the server has made the
> association, and that association might be incorrect, and that's
> OK, it's up to the application to sort it all out.
>
> There is another solution to this problem besides changing 5.1 and
> 7.3.4: You could define "representation" as a term of art, making it a
> static property of HTTP exchanges, one that is decided by fiat by the
> server, not an ordinary-language word. This would be rather tricky I
> think, and again I don't think it's what you intend, but I'm not sure.
>
> Yet another solution would be to say that the identity of the
> identified resource is determined by the authoritative representations
> that are or might be transmitted, or that it must be such that those
> representations are correct. Then there would be no way for the two to
> get out of sync in the way I suggest. But I don't think that's what
> you mean, either.
>
> I checked for "representation of" throughout part 2 and didn't find
> any other difficulties with the use of this expression, so whatever
> fix you choose is likely to be quite localized. Part 1 seems OK. The
> single use in part 6 would need to be scrutinized. I didn't check the
> other parts or other phrases.
>
> Best
> Jonathan
Received on Friday, 10 February 2012 14:28:30 GMT

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