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Re: CACHING-6 failure message: what is an "invalid" value?

From: Jo Rabin <jrabin@mtld.mobi>
Date: Fri, 04 Sep 2009 08:01:00 +0100
Message-ID: <4AA0BB2C.9060208@mtld.mobi>
To: Francois Daoust <fd@w3.org>
CC: public-mobileok-checker <public-mobileok-checker@w3.org>
I can tell you what was in my mind when I wrote that far-from-precise 
phrase :-)

If you send Cache-Control: croque-monsieur that should be construed as 
being invalid, though it is syntactically correct. The warn serves to 
remind content authors that toasted-open-face-ham-and-cheese-sandwich is 
not widely understood as a cache control directive and is likely to have 
undesirable interoperability consequences. It is only a warn because as 
you point out, Francois, RFC2616 makes it clear that any value is in 
principle acceptable, providing it conforms to the syntax for a token.


On 03/09/2009 16:59, Francois Daoust wrote:
> Hi,
> The CACHING test defines CACHING-6 as:
>  [[ If any cache related header contains an invalid value, warn ]]
>  http://www.w3.org/TR/mobileOK-basic10-tests/#CACHING
> What exactly constitutes an "invalid" value? For instance, looking at 
> the definition of the Cache-Control header field in the HTTP RFC, I see 
> that cache-response-directive may be a cache-extension:
>  http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9
> Are such cache-extension directives considered to be invalid values? 
> I.e. are we trying to alert authors on the fact that unusual 
> cache-control directives are unlikely to be understood, or is this 
> warning only motivated by real invalid values such as: "Cache-Control: =" ?
> I'd go for the latter proposal, but the mobileOK Checker library 
> currently does the former.
> Minor bug or feature?
> Francois.
Received on Friday, 4 September 2009 07:01:47 UTC

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