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On introducing a fallback attribute

From: Shane McCarron <shane@aptest.com>
Date: Fri, 27 May 2005 16:25:36 -0500
Message-ID: <42979050.60504@aptest.com>
To: "Justin Wood (Callek)" <116057@bacon.qcc.mass.edu>
CC: w3c-html-wg@w3.org, www-html-editor@w3.org, Jim Ley <jim.ley@gmail.com>, xhtml2-issues@aptest.com

Note:  I have changed the subject because I am forwarding this into the 
issue tracking system as a separate proposal.

Justin Wood (Callek) wrote:

>> Note, however, that in a hybrid document type that merged SVG with 
>> XHTML, this would be a little counter-intuitive for content 
>> developers.  I appreciate that you have identified a situation where 
>> you would not want the content to be rendered.  I could show many 
>> many examples where I would want it to be rendered.  The book is not 
>> closed on this issue, but at this time the Working Group has no ready 
>> solution that will satisfy both camps.  We would certainly welcome a 
>> proposal to that end, if you have one.
> In my opinion using src="" is _not_ the solution for a mixed namespace 
> document and fallback mechanics.

It was just an example.  In a mixed namespace document that was written 
in a markup language defined using the rules in XHTML Modularization, 
you might do something different.

> That said, may I ask what the harm would be in, for example, an 
> attribute in the xhtml namespace, |fallback="no"| which specifies 
> whether fallback content should be used or not, and given that at 
> least both me and you can agree that the most frequent use would 
> dictate that fallback="yes" leave that the default.

Sure.  And the working group has discussed this several times.  There 
was never consensus on introducing it.  Also, there was some concern 
that it would introduce special semantics that are not definable using 
standard mechanisms.  For example, you can express the semantics of the 
"src" attribute using HLink.  We have been trying to avoid introducing 
new elements or attributes with special semantics.  Regardless, I will 
again raise this as an issue and see if there is support for it in the 
working group.

> This will not specify if content should be rendered (display can 
> likely handle that in some way), but if the "use" of a tag be unknown 
> to a UA, should the UA then try and utilize underlying content, such 
> as that svg example.
> In my opinion, a real-world-example of why fallback content is bad, is 
> enough to warrant at the least a toggle.
> You are free to present this as a formal issue, or simply converse 
> with me (on the [public] list) regarding it prior to raising the issue.
> ~Justin Wood (Callek)
> [Let me note here, incase this is raised as a formal issue; should 
> this e-mail address fail to work, Callek@gmail.com will continue (I 
> have yet to migrate these lists over to that)]

Shane P. McCarron                          Phone: +1 763 786-8160 x120
Managing Director                            Fax: +1 763 786-8180
ApTest Minnesota                            Inet: shane@aptest.com
Received on Friday, 27 May 2005 21:25:55 UTC

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