Re: Increasing precision of Last-Modified header to allow sub-second granularity?

Adrien de Croy <adrien@qbik.com> Tue, 31 January 2012 21:42 UTC

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Date: Wed, 01 Feb 2012 10:41:38 +1300
From: Adrien de Croy <adrien@qbik.com>
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To: Julian Reschke <julian.reschke@gmx.de>
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Subject: Re: Increasing precision of Last-Modified header to allow sub-second granularity?
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On 1/02/2012 10:08 a.m., Julian Reschke wrote:
> On 2012-01-31 19:31, David Booth wrote:
>> Not sure where to ask this, but . . .
>>
>> Has there been any thought or discussion of allowing the Last-Modified
>> header to (optionally) carry more precision that one second, for the
>> benefit of clients that wish to reliably detect when a server has
>> changed its output faster than once per second?  For example:
>>
>>    Last-Modified: Fri, 27 Jan 2012 20:21:10.011483 GMT
>
> I don't think this has been mentioned so far.
>
>> Note that it is possible to get around the current one-second limitation
>> using ETags, but it would be nice if finer precision could be indicated
>> directly in the Last-Modified header.
>
> Not sure what this buys you compared to an ETag?

the ability to compare against other previous Last-Modified headers.  
That allows the client to know whether a version supercedes another, 
rather than having to defer to the server.

I'd be in favour.

It would have been nice if the definition for ETag could have allowed 
for comparison (required monotonic increase), such as a revision number.


>
>> I'm assuming that this is out of scope for the current HTTPbis charter,
>> so I'm mostly asking this regarding potential future work.  But the
>> "Potential Work" page is almost empty, and hasn't been updated in 16
>> months:
>> http://trac.tools.ietf.org/wg/httpbis/trac/wiki/PotentialWork
>>
>> Has this been discussed?  If not, does the suggestion belong?
>
> I think the Wiki page is a good pace to record this as proposal.
>
> Best regards, Julian
>
>

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