SWISH -- SWI-Prolog for SHaring

/* Same facts as the non-recursive version. */
executive(alice).
director(bob).
human_resources(danny).
read_compensation(danny).
manager(alice, bob).
manager(bob, charlie).
manager(charlie, danny).
manager(charlie, ellen).

/* Helper fucntions need to change to accommodate recursive logic. */
is_in_manager_chain(Manager, Managee) :- manager(Manager, Managee).
is_in_manager_chain(Manager, Managee) :-
    manager(Manager, Intermediate), is_in_manager_chain(Intermediate, Managee).
is_in_manager_chain_or_hr(Manager, Managee) :- is_in_manager_chain(Manager, Managee).
is_in_manager_chain_or_hr(Hr, _) :- human_resources(Hr), read_compensation(Hr).

/* Same remaining rules as the non-recursive version. */
violates_executive_privilege(Violator, Violatee) :-
    executive(Violatee), not(executive(Violator)).
violates_director_privilege(Violator, Violatee) :-
    director(Violatee), not(director(Violator)).

authorized(Principal, Action, Entity) :-
    Action == read_compensation,
    Principal == Entity.

authorized(Principal, Action, Entity) :-
    Action == read_compensation,
    is_in_manager_chain_or_hr(Principal, Entity),
    not(violates_executive_privilege(Principal, Entity)),
    not(violates_director_privilege(Principal, Entity)).