RTCORBA.PriorityMappingPolyORB provides different implementations of this specification:
RTCORBA.PriorityMapping.Direct maps CORBA priorities
directly to native priorities. If the CORBA priority is not in
System.Priority'Range, then the mapping is not possible.
RTCORBA.PriorityMapping.Linear maps each individual
native priority to a contiguous range of CORBA priorities, so that the
complete CORBA priority range is used up for the mapping. See
rtcorba-prioritymapping-linear.adb for more details.