W3C home > Mailing lists > Public > http-caching-historical@w3.org > April 1996

Re: Variant-ID proposal

From: Roy T. Fielding <fielding@avron.ICS.UCI.EDU>
Date: Thu, 18 Apr 1996 17:50:49 -0700
To: Koen Holtman <koen@win.tue.nl>
Cc: mogul@pa.dec.com, http-caching@pa.dec.com
Message-Id: <9604181750.aa20528@paris.ics.uci.edu>
> - for cache refreshing: the contents of the Cval header (in this case
>   "3212419" can be put in the If-Invalid header sent to
>   the origin server.  A typical if-Invalid header sent, if 3 variants
>   are caches, would be
>      If-Invalid: "3212419", "453232", "756456"
>   (Note that the origin server must ensure that all opaque validators
>   for the three variants are indeed different, because there is no
>   variant-id attached to disambiguate them.)

No, it can't do that.  It needs to either include a variant-id of
some kind or not use this mechanism at all.  That is, as I recall,
why I started with variant-id being a MUST even for transparently
negotiated URIs.  There is absolutely no difference between having
an origin server ensure that all opaque validators are unique across
variants, and having an origin server always include a variant-id;
in fact, the latter is much simpler.

Received on Friday, 19 April 1996 01:30:18 UTC

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