022: Bus Driver Scheduling

language ESSENCE 1.2.0
$ prob022.essence: Bus Driver Scheduling
$ Problem details available at http://www.csplib.org/Problems/prob022/
$ 05 September 2007
$

given Tasks new type enum,
      shifts : set of set of Tasks

find sched : partition from Tasks

minimising |parts(sched)|

such that forAll s in parts(sched) . s in shifts