Re: Until HTTP header when the representation will disappear in the future

[Karl Dubost <[e-mail]>]

Amos Jeffries [2013-06-12T16:12]:
> A combination of Expires (and/or max-age=N) and Cache-Control:must-revalidate serve this purpose.


Example:

HTTP BIS semantics spec, in the content has a "Expires: August 27, 2013"
http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-22

But if I do:

→ http HEAD http://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-22

HTTP/1.1 200 OK
Accept-Ranges: bytes
Content-Encoding: gzip
Content-Location: draft-ietf-httpbis-p2-semantics-22.html
Content-Type: text/html; charset=UTF-8
Date: Wed, 12 Jun 2013 07:55:45 GMT
ETag: "186e6bd-4b989-4dbc6c4497a80;4def056fb837d"
Last-Modified: Fri, 03 May 2013 02:04:10 GMT
Server: Apache/2.2.22 (Debian)
TCN: choice
Vary: negotiate,Accept-Encoding


And the spec             
Hypertext Transfer Protocol (HTTP/1.1): Caching
http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-22#section-7.3
says about Expires.


   The "Expires" header field gives the date/time after which the
   response is considered stale.  See Section 4.1 for further discussion
   of the freshness model.

   The presence of an Expires field does not imply that the original
   resource will change or cease to exist at, before, or after that
   time.


It doesn't have the same semantics. Caching vs Information on the representation.  Just asking maybe HTTP is not the right place to express it, though in case of an image it is difficult to do without HTTP. 


-- 
Karl Dubost
http://www.la-grange.net/karl/