Library prosa.analysis.definitions.service
Consider any kind of jobs and any kind of processor state. 
Consider any arrival sequence ... 
... and any schedule. 
The set of jobs served at time t can be obtained by filtering
      the set of all jobs that arrive at or before time t. 
  Definition served_jobs_at (t : instant) :=
[seq j <- arrivals_up_to arr_seq t | receives_service_at sched j t].
[seq j <- arrivals_up_to arr_seq t | receives_service_at sched j t].