conformance levels [was: Re: alt crazyness ...]

Olivier GENDRIN reminded us of
http://www.w3.org/TR/WCAG20/#conformance-claims

and Smylers wrote:
> That has two levels of conformance, with a 'partial
> conformance' exception for included external content.
> Are you suggesting something similar for HTML 5?

Yes; there has been resistance in the past to multiple levels of
conformance, but this does provide a pathway.

>   2 This webpage completely conforms to the
> HTML 5 standard.

>  1 This webpage conforms to the HTML 5 standard
> except that it includes unknown images from
> external sources for which we are unable to
> provide alterternative text.

> Except that ...

[various reformulations that eventually end up suggesting alt-less is
good enough in general, and a fully conforming with-alt document is
above and beyond.]

We do not want accessibility to become an above-and-beyond that must
be called out separately.  The longer and non-default formulation
should be used for the exceptional case, which should be the less
accessible.

    "This webpage conforms to the HTML 5 standard
     except that ..."

is precisely the formulation to use, and

    "... it includes images for which the author has
     failed to provide alt attributes."

is a good example, which might be worth formalizing.  (Maybe even
better than the <font> for WYSIWYG, since it is clearly an author fix
instead of a tool fix.)


And note that this conformance claim is orthogonal to whether alt
should always be required, or should become optional under certain
circumstances, such as when a (possibly implied) aria-describedby
provides the information in another manner.

-jJ