Extending the HTTP Cache-Control header (ISSUE-227)

Hi,

I mentioned on the call today that it would probably be better to define
the expected new values for the Cache-Control header as an informational
RFC rather than inside our content transformation guidelines.

As an example, Mark Nottingham has proposed 2 new values for the
Cache-Control header, as explained on his blog:
http://www.mnot.net/blog/2007/12/12/stale

The corresponding internet drafts are at:
http://www.mnot.net/drafts/draft-nottingham-http-stale-while-revalidate-00.txt
and 
http://www.mnot.net/drafts/draft-nottingham-http-stale-if-error-00.txt

While they don't concern the scope of what the content transformation
guidelines are interested in, they could serve as very good templates
should (some of) the group participants decide to pursue the IETF-way.

Dom