- From: Zhong Yu <zhong.j.yu@gmail.com>
- Date: Wed, 31 Oct 2012 10:30:01 -0500
- To: Julian Reschke <julian.reschke@gmx.de>
- Cc: Martin Thomson <martin.thomson@gmail.com>, Dan Winship <dan.winship@gmail.com>, HTTP Working Group <ietf-http-wg@w3.org>
On Wed, Oct 31, 2012 at 2:13 AM, Julian Reschke <julian.reschke@gmx.de> wrote:
> On 2012-10-30 21:40, Zhong Yu wrote:
>>
>> Got it. In the spec,
>> http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-21#section-8.2
>>>
>>> Additional header fields define metadata about the selected
>>> representation, which might differ from the representation included in the
>>> message for responses to some state-changing methods
>>
>>
>> So if the current representation has ETag=v1, and PUT sends a new
>> representation to which the server assigns ETag=v2, the response to
>> PUT may contain ETag of the old representation. (This was not in
>> RFC2616)
>> ...
>
>
> Why would it contain the old ETag?
According to the same section in the spec
>We use the term "selected representation" to refer to the the current representation of a target resource that would have been selected in a successful response if the same request had used the method GET and excluded any conditional request header fields.
In my example, the request is
PUT /resource HTTP/1.1
If the same request had used the method GET
GET /resource HTTP/1.1
the current representation with ETag=v1 would have been selected.
Thereforev1 is the selected representation. If the response contains
ETag header, it is a metadata about the selected representation, i.e.
v1.
Zhong Yu
Received on Wednesday, 31 October 2012 15:30:29 UTC