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From "Justin Erenkrantz" <jus...@erenkrantz.com>
Subject Re: Wrong etag sent with mod_deflate
Date Fri, 08 Dec 2006 23:40:20 GMT
On 12/8/06, Henrik Nordstrom <hno@squid-cache.org> wrote:
> A strong ETag must be unique among all variants of a given URI, that is
> all different forms of entities that may reside under the URI and all
> their past and future versions.
>
> A weak ETag may be shared by two variants/versions if and only if they
> can be considered semantically equivalent and mutually exchangeable at
> the HTTP level with no semantic loss. For example different levels of
> compression, or minor changes of negligible or no importance to the
> semantics of the resource (hit counter example in the specs).

I think we all (hopefully) agree that a weak ETag is ideally what
mod_deflate should add.  But, the specs simply dropped the ball here
as doing that breaks conditional requests.  If we could issue a weak
ETag and have it work for conditional requests, this would be easy and
be done by now.

We can't, so I would much prefer that we don't break conditional
requests just because mod_deflate is in use.  I also don't believe we
can come up with a reversible ETag semantic without rewriting big
chunks of code or introducing butt-ugly hacks.  Apache has always
treated the ETag as opaque (except for "W/") - to do otherwise is to
bust large assumptions.  -- justin

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