Re: pragma no-cache -- Can we make it more useful?

Roy T. Fielding (fielding@simplon.ICS.UCI.EDU)
Thu, 14 Jul 1994 07:57:41 +0200

> What might be useful, in lieu of my notion about modifiying pragma
> no-cache is to have a header line which indicates the data/time at
> which the copy in the cache was snapshotted from the authoritative
> server.
> In a situation in which there are a cascade of caches, this date/time would
> be the same for all.

This has been discussed before on www-talk, e.g.


The relevent bit being a new header --

should reflect the date/timestamp of last comparison with the original
(i.e. the Date: header returned by the source document's HTTP server
in that comparison). Note that this should not be changed by cache
managers more than once-removed from the origin. This is because the
act of checking the cache consistency with the original document is
equivalent to getting a new copy of that document, but the act of
checking cache consistency with a higher-level cache is only equivalent
to copying that cache.

Has anyone implemented this?

...Roy Fielding ICS Grad Student, University of California, Irvine USA
<A HREF="">About Roy</A>