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Re: recommend Accept in preference to User-Agent to determine formats

From: Dan Connolly <connolly@w3.org>
Date: Tue, 12 Dec 2006 09:30:16 -0500
Message-Id: <6171f76674162d7a01e098be989957ed@w3.org>
Cc: public-bpwg-comments@w3.org
To: "Charles McCathieNevile" <chaals@opera.com>

On Dec 12, 2006, at 12:05 AM, Charles McCathieNevile wrote:
> On Wed, 29 Nov 2006 14:59:01 +0530, Dan Connolly <connolly@w3.org> 
> wrote:
>> Regarding...
>> "To determine what formats a device supports, Web sites may use any
>> combination of device profile information such as the HTTP User-Agent
>> header, HTTP Accept headers and UAProf."
>>  -- http://www.w3.org/TR/mobile-bp/ (2 November 2006)
>> The HTTP accept header is specifically designed for this purpose;
>> web sites SHOULD use it.
> The problem is, given the cost (in terms of battery consumption, 
> latency, bandwidth, ...) of sending data from a device, it makes no 
> sense at all for reasonably capable devices to be sending the 1kb or 
> so of data that would make this feasible.

1kb? where do you get that? I don't see anything in the draft or 
elsewhere that leads to that conclusion.

And what alternative takes significantly less bandwidth?

The way the draft currently reads re-specifies HTTP. I suggest that's 
beyond your charter.

>> It's OK to say that they MAY use other stuff, but it doesn't
>> make sense to say that User-Agent is just as good as Accept
>> for figuring out what format the client wants.
> In practical terms it does. The standard might say otherwise, but 
> unfortunately there are real problems engendered in actually 
> implementing it, which is why browsers don't

Which browsers don't? All browsers I know of send reasonable Accept: 

>  (as far as I know the only browsers that are accurate are those which 
> only accept a couple of formats anyway, and Lynx which sends a 
> monstrous amount of data).
> cheers
> Chaals

Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Tuesday, 12 December 2006 14:30:44 UTC

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