RE: [xri] comments on Expires

["Scott Cantor" <cantor.2@osu.edu>]

Nika Jones wrote on 2010-01-13:
> ...  A resolver MUST NOT use an XRD after the time stated here ... If the
> HTTP transport caching semantics specify an expiry time earlier than the
> time expressed in this [element], then a resolver MUST NOT use this XRD
> after the expiry time declared in the HTTP headers per section 13.2 of
> [RFC2616] ...
> 
> I think that says it all.

Except that cache control != validity, and XRD Expires is about validity.
 
> I suggest that anytime after the <Expires /> date has past, that the XRD
> MUST NOT be used, regardless of HTTP caching. Because as you mentioned the
> same document should be served up (hence cache.)

It's nothing to do with HTTP, it's just that if it's Expired, it isn't valid
any more and you're basically using it at your own risk. Normally specs stop
short of saying MUST NOT use. Usually it's phrased more as the data in the
XRD has no presumed validity past that time.

The HTTP caching layer, if in fact HTTP is used, just controls the
conditions under which a new copy might or might not be obtained, and at the
end of the process, you either have a valid XRD or an expired one.

-- Scott