[whatwg] Pre-defined classes and conformance

[Henri Sivonen]

Quoting the spec:
> Conformance checkers must use the information given on the WHATWG  
> Wiki ClassExtensions page to establish if a value not explicitly  
> defined in this specification is defined, and if so, whether it is  
> being used on the right elements.

This is problematic as previously conforming documents would be made  
non-conforming when a class name is registered and doesn't apply to  
all elements (then the previously conforming documents use it  
elements for which it doesn't apply according to the registration).

> When an author uses a new class name not defined by either this  
> specification or the Wiki page, conformance checkers may offer to  
> add the value to the Wiki, with the details described above, with  
> the "proposal" status.

It has been pointed out to me that the offers would drive developer  
crazy.

-- 
Henri Sivonen
hsivonen at iki.fi
http://hsivonen.iki.fi/