[html5] XHTML extending. id, class, style attributes support for other namespaces

[Anton Vitr]

Hello Ian!

Below:
> - Do you want this to work in environments where scripting is disabled, or do you only want this to work when your scripting library is active?
Only on environments where scripting is enable. No fallback needed.

> - Do you want it to be easy to take existing HTML and add widgets made with your library?
I think yes. 

> - Do you want it to be easy to take documents that use your library and easily remove the use of your library?
Possible, but not needed.

> - Does it need to work in old browsers, or only new ones?
Only modern: IE9+, FF, WebKit.

> The answers to these questions would help find answers to your questions.
Many javascript libraries,like jquery.ui, extjs, allow javascript-only syntax. 
Several of them, like jquery.mobile allows html syntax - which slightly more readable and can be mixed with standard html tags.
For example, jquery.mobile done this using custom tag attributes(data-role,data-enhance) on common elements(input, div, span):
<div data-role="popup" id="popupBasic">
	<p>This is a completely basic popup.<p>
</div>
I want some similar, but some more obviously than some custom attributes. 
Also, I working a while with other frameworks: java.jsp, asp.net, silverlight(xaml) which based on declarative xml - actively use custom tags and xml namespaces for extendability and structuring of big application, 
So it will be good to have some similar on client-side, possible, with IDE intellisense (if xml schema will be provided).  Possible, XForms is such example.

Make sense?

Anton.