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Re: Point of Extensibility

From: Hallvord R. M. Steen <hallvord@opera.com>
Date: Thu, 03 Apr 2008 14:00:56 +0200
To: "Julian Reschke" <julian.reschke@gmx.de>, "Philip Taylor" <pjt47@cam.ac.uk>
Cc: "Doug Schepers" <schepers@w3.org>, public-html@w3.org
Message-ID: <op.t81abuwza3v5gv@hr-opera.oslo.opera.com>

On Tue, 01 Apr 2008 21:33:33 +0200, Julian Reschke <julian.reschke@gmx.de>  

>>> How about stating that any element with an attribute "xmlns", being  
>>> set to something different from "" or the XHTML namespace name,  
>>> implies <ext>?

>>  Lots of existing content uses attributes named "xmlns" -- see e.g.  
>> <http://philip.html5.org/data/xmlns.txt>. (Only 45 pages in the data  
>> set had XML content-types, so this is pretty much all text/html). It  
>> seems that compatibility requirements will make it impossible to base  
>> anything on the "xmlns" attribute.

> Well, a similar argument can probably applied to *any* change in the  
> language, such as adding new elements.

Certainly, but for a nugget of implementor experience to back up what  
Philip is saying: Opera at some point had some "support" for xmlns in  
text/html. It was removed because it broke pages when random sections or  
elements were no longer considered HTML markup. (I know without offering  
more hard facts like what exactly we "supported", how many pages we  
noticed breaking this is semi-anectdotal - I could look up those bugs if  

So we really can't imply <ext> when we see some xmlns - or at least not  
without extra magic that would "fall back" to un-implying <ext> if the  
"unknown" content looked like HTML after all (naturally, nobody wants to  
go down this route).

Hallvord R. M. Steen
Core QA JavaScript tester, Opera Software
Opera - simply the best Internet experience
Received on Thursday, 3 April 2008 12:01:37 UTC

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