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Re: WGLC #353: Multiple Values in Cache-Control headers

From: Mark Nottingham <mnot@mnot.net>
Date: Mon, 11 Jun 2012 21:57:57 +1000
Cc: "ietf-http-wg@w3.org Group" <ietf-http-wg@w3.org>
Message-Id: <EC5286A1-C4C3-4509-8C93-683899470E4A@mnot.net>
To: Julian Reschke <julian.reschke@gmx.de>

On 08/06/2012, at 8:15 PM, Julian Reschke wrote:

> On 2012-06-08 12:06, Mark Nottingham wrote:
>> 
>> On 08/06/2012, at 7:57 PM, Julian Reschke wrote:
>> 
>>> On 2012-06-08 09:30, Mark Nottingham wrote:
>>>> Revised proposal, based upon discussion:
>>>> 
>>>>> Add a note to <https://svn.tools.ietf.org/svn/wg/httpbis/draft-ietf-httpbis/latest/p6-cache.html#calculating.freshness.lifetime>:
>>>>> 
>>>>> """
>>>>> When there is more than one value present for a given directive (e.g., two Expires headers, multiple Cache-Control: max-age directives), it is considered invalid. Caches SHOULD consider responses that have invalid freshness information to be stale.
>>>>> """
>>>> 
>>>> 
>>>> Any further comments? Otherwise we'll close and incorporate.
>>>> ...
>>> 
>>> Would it make sense to have generic text in the definition of Cache-Control about this?
>> 
>> Don't think so, because...
>> 
>>> Does the "must have a single value" rule apply to all directives?
>> 
>> No; I've seen examples that use multiple values (can't remember what ATM)
> 
> If that is the case, we probably need to spend some more time on clarifying this, as this different from similar header fields.

How so? I thought we'd agreed we don't have shared microsyntax / model for our existing headers...



>>> Can the definition of error recovery diverge per directive?
>> 
>> I imagine so.
> 
> Which makes it sound as if we should define it for all directives defined in this spec (as bad as this sounds)...


If someone wants to point out specific instances where they believe it's important for security and/or interoperability, and it doesn't fall afoul of our stance on error handling, by all means.

--
Mark Nottingham   http://www.mnot.net/
Received on Monday, 11 June 2012 11:58:25 GMT

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