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Re: If-Range and cache validation using Last-Modified

From: Yves Lafon <ylafon@w3.org>
Date: Mon, 18 Jul 2011 04:40:15 -0400 (EDT)
To: Matthew Cox <macox@microsoft.com>
cc: "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
Message-ID: <alpine.DEB.1.10.1107180428330.31208@wnl.j3.bet>
On Fri, 3 Jun 2011, Matthew Cox wrote:

Hi Matthew,

> Part 5 section 5.3 If-Range has the following text in the case that the response has no etag and only Last-Modified.
>   If a client wishes to perform a sub-range retrieval on a value for
>   which it has only a Last-Modified time and no opaque validator, it
>   MAY do this only if the Last-Modified time is strong in the sense
>   described in Section 2.1.2 of [Part4].
>
> Section 2.1.2 in Part 4 has this text:
>   o  The validator is about to be used by a client in an If-Modified-
>      Since or If-Unmodified-Since header field, because the client has
>      a cache entry for the associated representation, and
>
>   o  That cache entry includes a Date value, which gives the time when
>      the origin server sent the original response, and
>
>   o  The presented Last-Modified time is at least 60 seconds before the
>      Date value.
>
> This seems to exclude If-Range which is strange since the If-Range text 
> pointed to this section.  Is it possible to add If-Range to the text in 
> the first bullet point, or make the text more generic such that it 
> doesn't exclude other methods that use the Last-Modified time?

It is always better to avoid cross-refs between optional parts, but in 
that case there is already a mention of If-Range in p4 (3.5), so yes, the 
best option would be to mention If-Range in p4 2.1.2.

Old text:
>   o  The validator is about to be used by a client in an If-Modified-
>      Since or If-Unmodified-Since header field, because the client has
>      a cache entry for the associated representation, and 
New text:

Section 2.1.2 in Part 4 has this text:
    o  The validator is about to be used by a client in an If-Modified-
       Since, If-Unmodified-Since or If-Range header field, because the
       client has a cache entry for the associated representation, and

-- 
Baroula que barouleras, au tiéu toujou t'entourneras.

         ~~Yves
Received on Monday, 18 July 2011 08:40:17 GMT

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