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Re: If-Modified-Since No Longer Cool?

From: Inigo Lopez <ilopez@fundesco.es>
Date: Tue, 08 Oct 1996 10:26:37 +0200
To: Henrik Frystyk Nielsen <frystyk@w3.org>
cc: Ari Luotonen <luotonen@netscape.com>, jjames@firstfloor.com (John W. James), www-talk@w3.org
Message-ID: <4834.844763197@indy.fundesco.es>
En fecha/On Mon, 07 Oct 1996 16:57:49 -0400  Henrik Frystyk Nielsen 

> Hopefully, etags will be the preferred way to validate caches in HTTP/1.1
> applications. That way, we avoid the resolution being 1 sec, millions
> of different date/time formats, the 2000 problem, time zones, and lack of
> time synchronization.

I haven't read about etags yet, but I still think using If-Modified-Since
doesn't have the problems you mention:

- resolution being 1 sec: seems good enough for me, taking into account 1 sec
is a lot less than the average time between document modifications.

- millions of different date/time formats: there are *only* three date formats
allowed in HTTP (for compatibility issues), and *only* one is encouraged

- the 2000 problem: it is not a problem if you use the suggested time format,
defined in RFC 822 (updated by RFC 1123) which uses a 4 digit year.

- time zones: the only time zone allowed is GMT

- lack of time synchronization: there is no need for it. The client must use
date values returned by the server, even if they don't match its internal
clock. This date is interpreted in the server´s understanding of time.

I just liked the simplicity of the Last-Modified/If-Modified-Since mechanism
for cache implementation.


    O      Iñigo López Cía                 ilopez@fundesco.es
   o O     Fundesco - Dpto. Redes
  . o O    Plaza de la Independencia, 6    Tel: +34-1-3300735
   . o     28001 Madrid                    Fax: +34-1-3300675
    .      Spain
Received on Tuesday, 8 October 1996 04:30:00 UTC

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