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Re: TWO Change proposals for ISSUE-41 : Distributed Extensibility

From: Maciej Stachowiak <mjs@apple.com>
Date: Tue, 16 Mar 2010 22:15:16 -0700
Cc: Jonas Sicking <jonas@sicking.cc>, "Ennals, Robert" <robert.ennals@intel.com>, Ian Hickson <ian@hixie.ch>, HTMLwg <public-html@w3.org>
Message-id: <1BAB5CFA-6612-4D38-932B-729565018424@apple.com>
To: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>

On Mar 16, 2010, at 8:48 PM, Leif Halvard Silli wrote:

> Maciej Stachowiak, Tue, 16 Mar 2010 18:18:24 -0700:
>
>> I think Microdata and RDFa are good examples of standardized
>> extensions. However, as a browser engine developer, I would like the
>> ability to do vendor extensions (either experimental or not intended
>> for public Web content) without stepping on valuable shared
>> namespace. We have a decent way to do that with CSS properties using
>> the vendor prefix convention(*). It would be nice to have something
>> similar at the HTML level. It seems like Rob's proposals (either X or
>> Y) would provide ways to do that.
>
> Rob states in proposal X that
>
> ]]Any document that parses correctly in both XML and HTML is  
> guaranteed
> to parse to the same DOM tree.[[

I think this statement is true, even with Robert's proposal. Here is a  
trivial counter-example:

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
   <head>
     <title>hi</title>
   </head>
   <body>
     <table><tr><td>there</td></tr></table>
   </body>
</html>

This parses correctly and indeed is fully conforming as both XML and  
HTML, but does not produce the same DOM

> And the same seems to me to be the case w.r.t. vendor prefixes in  
> HTML:
> If e.g. <div -webkit:attribute=""> is something that only Webkit
> understands, then it means that it is treated differently by Webkit
> compared to how other browsers treat it, probably because Webkit uses
> an internal namespaces which attach meaning to the -webkit prefix.
>
> And hence, can we justifiably say that Webkit sees the same DOM as the
> other browsers see?

Yes we can. The DOM tree is the same. The processing of that DOM may  
be different.

> I am not against Rob's proposal because of *this*. I just think that  
> we
> should realize that it is not a realistic requirement to says that all
> browsers should see the exact same DOM. And so, I think we should take
> into account, when defining distributed extensibility, that there must
> be some leeway in this regard. Both with regard to legacy browser
> support and with regard to cross-browser support.

All browsers seeing the same DOM is different from XML and HTML  
parsing producing the same DOM. The former is essential, and separate  
from any differences in processing that DOM. The latter will not be  
achieved by Robert's proposal and is probably not practical for  
various edge case reasons.

Regards,
Maciej
Received on Wednesday, 17 March 2010 05:15:50 UTC

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