A user (person) is permitted to act on an object if there is a path (series of permission Links) from the acting user to the object in which
-* Every intervening object is a Group or a User, and
+* Every intervening object is a Group, and
* Every intervening permission Link allows the current action
+Special case: A permission path can also include intervening User objects if the links _to_ the Users are "can_manage" links.
+
Each object has exactly one _owner_, which can be either a User or a Group.
* If the owner of X is A, then A is permitted to do any action on X.