[10076] in www-talk@info.cern.ch
Re: HTTP HEAD requests for Last-Modified info
daemon@ATHENA.MIT.EDU (Larry Masinter)
Thu Jun 20 15:33:49 1996
To: marc@ckm.ucsf.edu
Cc: www-talk@w3.org
In-Reply-To: "Marc Salomon"'s message of Thu, 20 Jun 1996 10:30:10 PDT <9606201030.ZM7466@home.ckm.ucsf.edu>
From: Larry Masinter <masinter@parc.xerox.com>
Date: Thu, 20 Jun 1996 11:38:04 PDT
Resent-From: www-talk@w3.org
> Caching can't function to its potential if servers don't advertise L-M whenever
> possible. Caching is essential to HTTP scalability in the near-term. Server
> authors: N.B. above.
Actually, caching can work without Last-Modified, as long as the
origin server sends Expires and an ETag.
Expires is actually what lets a cache do its work: give the cache
permission to hold on to something. And the ETag lets the cache use
If-None-Match instead of If-Modified-Since with date stamps, since
dates are unreliable in some systems which might otherwise be able to
use cache validators.
Larry
