How aria-multiselectable applies to TreeViews

I am curious how it is imagined that the "aria-multiselectable" and "aria-selected" properties apply to a TreeView control?  The ARIA spec indicates that the "aria-multiselectable" property can be used with the the "tree" role, and the "aria-selected" state with "treeitem".  However, the "aria-selected" state only accepts a boolean.  How should developers indicate parent nodes in a partially selected stated - some tree items selected, some not.  And how is a screen reader supposed to announce the partially selected state of a parent node?

I've yet to find any ARIA TreeView examples that make use of "aria-multiselectable", but considering the spec indicates that it applies to trees and the ARIA Authoring Practices specifies keyboard shortcuts for supporting multiple selection on trees, I figured some thought must have been given to this use case.

Any insight would be greatly appreciated.

Thanks,
Todd

Received on Saturday, 27 November 2010 00:19:14 UTC