TEMPORALLY-FIXED-JOB-CLASS denotes a job whose assignment to a time range is predefined.
(<=> (Temporally-Fixed-Job-Class ?Class)
(And (Class ?Class)
(Subclass-Of ?Class Job)
(Slot-Cardinality ?Class Assigned-Time-Range 1)))
(Slot-Cardinality ?Class Assigned-Time-Range 1) (Class ?Class)
(<= (Subclass-Of $X Job) (Temporally-Fixed-Job-Class $X))
(<=> (Temporally-Fixed-Job-Class ?Class)
(And (Class ?Class)
(Subclass-Of ?Class Job)
(Slot-Cardinality ?Class Assigned-Time-Range 1)))