body element and global aria attributes

[scottaohara]

As a follow on to #447

Should any global attributes be allowed on the body element, or if they are still allowed, should they not be accompanied with a warning that the attribute is either likely to do nothing, or potentially be problematic? A note or an authors should not might be sufficient... i don't want to make errors if the attribute doesn't do anything at all.

aria-atomic (arguably useful to mitigate one's problematic use of aria-live)
aria-busy (potentially problematic)
aria-controls (seems useless here)
aria-current (the current body one is interacting with if... say... there are iframes?)
aria-describedby (described by its contents?)
aria-details (are detailed by its contents?)
aria-dropeffect (someone going to pick up the body and drop it somewhere?)
aria-flowto (hmm...)
aria-grabbed (someone going to grab the whole body?)
aria-keyshortcuts (hmm...)
aria-live (never seen this used where it wasn't a problem)
aria-owns (it's the body... it already owns everything...)
aria-relevant (re: aria-atomic comment)

aria-label, aria-labelledby and aria-roledescription are prohibited on generics
aria-hidden=true is now disallowed on the body