Supercedes: header

The invalidatation mechanism in 6.1 Location: headers and spoofing of 
http://ftp.digital.com/%7emogul/draft-mogul-http-caching-02.txt 
sparked the following thought:

In order to help caches trim themselves, I propose a Supercedes: 
header.

   Supercedes: URI

A cache in receipt of a supercedes header could schedule the 
referenced URI for early retirement.  It may not be instantly 
obsolete as users may currently be displaying pages which reference 
it, but it would likely not be useful to retain the entry for days.  
The authority to issue this header could be limited to the 
corresponding host to discourage malicious usage, but I wouldn't 
bother. Such usage could not cause semantic transparency problems as 
the URI is already exposed to being purged from the cache at any time 
by the cache's replacement algorithm.

This would allow caches to respond well to pages that are updated by 
referring to new content (different URI) rather than just changing 
the referred to content itself.

This technique allows users that are on old copies of a page to 
navigate to other content without surprises while new visitors to the 
page see the most current references.  A news headlines page would be 
a candidate for such usage.

Duane

Received on Friday, 5 April 1996 17:10:19 UTC