Re: Request for Volunteers: Polyglot spec

On 04/01/2010 01:44 PM, Jonas Sicking wrote:
> On Fri, Mar 26, 2010 at 1:52 PM, Sam Ruby<>  wrote:
>> I took an action item from the TAG yesterday to convey the following
>> request:
>>     The W3C TAG requests there should be in TR space a document
>>     which specifies how one can create a set of bits which can
>>     be served EITHER as text/html OR as application/xhtml+xml,
>>     which will work identically in a browser in both bases.
>>     (As Sam does on his web site.)
>> This request requires a lot of explanation.  To start, it is recognized up
>> front that this will be a subset of the set of possible documents that can
>> be expressed as HTML5.  This is entirely OK.  For example, if it were to be
>> the case that such a subset were to entirely disallow scripts of any kind,
>> that would be acceptable as there exists a substantial class of documents
>> which do not require scripting of any kind.
> Out of curiosity, what does "work identically" encompass? Do they have
> to have the same DOM? Or just render the same when the default UA
> stylesheet is applied? Or just be semantically equivalent?
> Even if the page itself doesn't contain any scripts, if the page is
> contained in an iframe then scripts in another page might trip over
> differences if the two pages produce different DOMs.
> I believe a document served as text/html and one served as
> application/xhtml+xml will always have different DOMs since the former
> will have nodes with upper case nodeNames, whereas the latter will
> have nodes with a lower case nodeName.
> If DOMs aren't important, only rendering is, I assume that this
> document won't qualify:
> <html xmlns="">
>    <head>
>      <style>  tbody { background: green }</style>
>      <title>example document</title>
>    </head>
>    <body>
>      Integer values for true/false.
>      <table>
>        <tr><td>true</td><td>1</td></tr>
>        <tr><td>false</td><td>0</td></tr>
>      </table>
>    </body>
> </html>
> Since if this document is served as text/html the table will have a
> green background, but if served as application/xhtml+xml it will not.

I'll answer this in reverse order.

I agree that the document you cited won't qualify.  There are two ways 
to address this: treat tables without explicit tbody's as 
non-conforming, or treat style rules that produce different results 
based on the existence of tbody elements to be non-conforming.  As luck 
would have it, I had an opportunity to observe this exact discussion. 
DanC and PLH preferred it when tbody elements were included, TimBL 
preferred to not include tbody elements when they were not necessary.  I 
didn't express an opinion in that venue, but I will say that while I 
don't currently routinely use tbody elements, I do think it would be 
better approach if this document were to suggest that they were required.

I don't believe the correct question is a binary "are DOM's important: 
yes or no".  In general DOMs are important, but there may be specific 
cases where the differences are containable.

Overall I do believe that rendering (including the ability to be styled 
with stylesheets) is a primary consideration.  My biggest problem with 
Appendix C is that is makes it sound easy.  My biggest problem with the 
WHATWG wiki page on this topic is that it makes it sound darn near 

A document that states indicates that while it is possible it is more 
difficult than it would appear to be would be worthwhile.

> / Jonas

- Sam Ruby

Received on Thursday, 1 April 2010 18:18:31 UTC