Sharing Cabinets

It occurred to me last night that I can restrict Roles (specificly Drawers, Folders and Pages) from being under (in) more than one Cabinet at the same time. Then I can easily support the sharing of Cabinets--the edge conditions are eliminated.

Cabinets also seems to be a good level for restricting access. So I'm inclined to disallow Pages, Folders and Drawers at the Ark level as well.

I'll note that sharing remains out-of-scope for CompStrm1--due to problems with list and destroy operations. But I might as well put these restrictions into CompStrm1, rather than try to impose them later.