Before an assignor can pair referees with matches, the schedule of matches must be defined. This function is performed by the leagues. Teams are subdivided into competitive groups by gender, age, and competitive expectations. Scheduling criteria can include travel distance, home and away alternation, and head to head competition balancing concerns in the scheduling algorithm. In the end there is a master schedule indicating which two team play at what location at what time for every match of the schedule.
Availability is the first step in assignment.
The assignor contacts the pool of prospective referees and inquires about their availability on the dates and times of matches that the assignor must cover. The individual availabilities are returned to the assignor who uses this as another discriminating factor in pairing officials with games. Some assignors using this information assign referees only for the coming week's matches and basically perform assigning on an ongoing weekly basis for the duration of the season. Other assignors designate the referee assignments for the entire season and provide each referee with the season assignment they are expected to fulfill. The assignor must then handle each of those turn backs before the scheduled match time.