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Why Microsoft's authoritative=true won't work and is a bad idea

From: Ian Hickson <ian@hixie.ch>
Date: Sat, 5 Jul 2008 07:16:15 +0000 (UTC)
To: Julian Reschke <julian.reschke@gmx.de>, HTTP Working Group <ietf-http-wg@w3.org>, "public-html@w3.org" <public-html@w3.org>
Cc: e_lawrence@hotmail.com
Message-ID: <Pine.LNX.4.62.0807050656490.13974@hixie.dreamhostps.com>

On Thu, 3 Jul 2008, Dave Singer wrote:
> 
> Next up:  a server that always adds the "I mean it" attribute, even when 
> it doesn't, and the subsequent invention of the "No, really, come on, 
> you have to believe me, scout's honor, I really truly mean it" 
> extension.

This is exactly why this won't work. Sites will use this correctly, then 
someone will set some default somewhere incorrectly, or copy and paste a 
correct site somehow, or misunderstand a tutorial or something, and deploy 
it without testing in IE8. And it will work fine in all the browsers 
except IE8, an then IE8 will be patched to make this attribute trigger a 
slightly different (and smaller) set of content-sniffing instead... except 
that the set won't be quite what was intended, because there will be some 
bug, and then there will be sites that DO test with this patched IE8, but 
end up relying on this slightly different content sniffing...

...and ten years from now we'll have four different content sniffing modes 
with four different ways of triggering it and the next generation will 
look back at 2008 and wonder what we were thinking.


The way out of this mess is containment. We define a strict set of 
Content-Type sniffing rules that are required to render the Web, and we 
get the browsers to converge on only sniffing for those.

That's what the HTML5 spec does by defining strict and precise content 
sniffing rules based on what browsers do now:

   http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#content-type-sniffing

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Saturday, 5 July 2008 07:16:58 GMT

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