[aria impl] platform mappings, and role vs state

Hi All,

This is a browser implementation topic.

What about adding a section to
http://www.w3.org/WAI/PF/aria-implementation/  about conflict resolution
between role and state for platform a11y mapping? This, in addition to
inlining specific heuristics where necessary.

For example consider the checkable state (which is different from checked).
<span role="checkbox" aria-checked="undefined">

Now remember, "undefined is special" as it tells us treat the attribute
as missing or "". The role tells us that the object is checkable, and
the aria-checked="undefined" would normally indicate the object is not
checkable.  I think a good general rule is to give the role more mapping
power and to expose the checkbox with a checkable state. What do others
think? These are somewhat unusual cases (strange aria markup really), so
I don't want to make a huge deal about it.

cheers,
David