[aapi] Changing a role attribute

In Tuesday's meeting, we discussed the FAQ in section 5.6 that deals with
changing a role attribute. [1]

The UAIG currently says that changing a role is considered "incorrect
practice" per the WAI-ARIA spec. But it goes on to say that the UA should
handle this condition by firing events that invalidate the element and add
a new one with the new role. We said in the meeting that "adding" an aria
role to an element seems reasonable but changing an existing aria role is
an error. [2]

In the WAI-ARIA spec, it's not quite as strongly worded as "incorrect
practice". It says that user agents should update the role mapping when the
role attribute changes. It further states that authors are responsible for
"deleting the associated element and its children and replacing it with a
new element with the appropriate role." so that assistive technologies will
process the change.

In the UAIG, should we say that the User Agent's responsibility is just to
update the mapping but not fire any events and leave it to the author to be
responsible to delete the element and add a new one?

[1] http://www.w3.org/WAI/PF/aria-implementation/#error-handling_roles
[2] http://www.w3.org/2009/09/29-aapi-minutes.html#item03
[3] http://www.w3.org/WAI/PF/aria/#role_model

Thanks,
Andi