  % necessary
    [     sc(valuable_item,Valuable_item,[protected(Valuable_item),protected_by(Valuable_item,Trigger)]=>[not_protected(Valuable_item),protected_by(Valuable_item,Trigger)]),
     sc(burglar,Burglar,[casing_joint(Burglar),expertise(Burglar,Trigger)]=>[found_goods(Burglar),expertise(Burglar,Trigger)])],
    % conditional
    []).
operator(spend(Valuable_item,Trigger,Burglar),
    % prevail
    [     se(valuable_item,Valuable_item,[gone(Valuable_item),protected_by(Valuable_item,Trigger)])],
    %