Negative Obligation
Needed as a restraint on actions which is subject rather than target based
O- tutors {TellResults} students when date < FinalExamMeeting
O- x:schedulers {assign} WorkPool when x.state = standby
Notes:
Used where targets do not wish to be protected from subject actions
Staff are permitted to talk to students - impractical to implement as a normal authorisation policy
Schedulers must restrain action based on local state - ie in standby mode
They are authorised to assign jobs to computers in WorkPool