W3C home > Mailing lists > Public > public-html@w3.org > July 2008

Re: ISSUE-41: Decentralized extensibility

From: Erik Dahlström <ed@opera.com>
Date: Thu, 24 Jul 2008 17:07:31 +0200
To: "Ian Hickson" <ian@hixie.ch>, "Doug Schepers" <schepers@w3.org>
Cc: "HTML WG" <public-html@w3.org>
Message-ID: <op.uesxmtd4gqiacl@gnorps.linkoping.osa>

On Tue, 22 Jul 2008 07:26:35 +0200, Ian Hickson <ian@hixie.ch> wrote:

> On Mon, 21 Jul 2008, Doug Schepers wrote:


>> You cite a few cases of strange mixed-namespace content.  You don't show
>> how this content would break the site as dramatically as you claim in
>> your scenario.  Please draw the connection, if one exists, between your
>> evidence and your conclusion.
> I'm assuming you are really asking "how would a particular proposal fail
> when exposed to the existing content?".
> Well for instance if a page looks like the following (I'm doing this from
> memory but this is quite similar to some of the pages I saw in some of my
> research):
>    <html>
>     <head>...<head>
>     <svg xmlns="http://www.w3.org/2000/svg">
>     <p>Hello world
>    </html>
> ...then in today's browsers, the page would just say "Hello world". Now if
> we instead use the proposal that the SVGWG has put forward, for instance,
> the page would no longer say "Hello world", it would instead either show a
> blank page or say something like "tml>" or "html>", depending on exactly
> how we define where the XML parser fails. 

This is an example where the author clearly wanted to use svg, even if it is authored in a broken way (or in this case to specifically be broken I suppose). I don't think it's possible to avoid breaking at least some broken examples :)

Try replacing the <p> in the example above with <a>. Now how would you expect it to be handled (svg:a or html:a)? Or if it was preceeded by an element <metadata xmlns="http://myown.com/data">? The SVG WG proposal says let it be treated as part of the SVG fragment, which in the above example means that the <p> element by default will be in the svg namespace.

Now, when an svg fragment is broken, the SVG WG proposal says do your best to recover, but alas it's not possible to repair each and every case of breakage. Not in this proposal, and not in the the previous proposal made by the HTML WG.

Furthermore, the number of valid svg:s that will break if XML namespaces are not supported when SVG is inline in HTML should greatly exceed the number of examples that use a broken mix of HTML and SVG.

> That's an example of this
> proposal "breaking" a page -- the page would look significantly different
> in a browser that implemented the proposal than in a browser that did
> not, despite the page being written before the proposal existed.

Right, but so would pages that would suddenly become correct with either proposal. Would you consider that to be "breaking" a page too?


Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog: http://my.opera.com/macdev_ed
Received on Thursday, 24 July 2008 15:06:14 UTC

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