This should haven after#1454 lands, as that removes the term "required owned element".

There are many uses of "owned elements" which should probably be reconsidered. For example, inspinbutton:

Authors MAY create a spinbutton with children or owned elements, but MUST limit those elements to atextbox and/or twobuttons.

Should we simply say "with accessibility children" or "with children" or (maybe) "with owned elements"?

Additionally, "owning element" is not used in the spec, except intooltip where it's meaning is not even the definition of "owning element":

The tooltip typically becomes visible, after a short delay, in response to a mouse hover, or after the owning element receives keyboard focus