Re: What problem is this task force trying to solve and why?

>
>
> In particular, the RELAX NG schemas for XHTML 1.0 are available at
> http://www.thaiopensource.com/relaxng/xhtml , and they could be readily
> updated for XHTML 1.1.  These schemas will confirm that a document is
> structurally XHTML whether or not it is XML-valid.
>

The XHTML2 WG did some before they vanished:

http://www.w3.org/MarkUp/2010/xhtml-m12n-relaxng-20101216/

There are also schemas for HTML5:

https://github.com/appden/html5-syntax
http://syntax.whattf.org/