Modelling double-shift school timetables

Creating school timetables is problematic in many schools due to the complexity of models that need to be solved. If schools do not have enough resources (rooms, teachers), they are forced to work double or several shifts. This paper deals with shift types and ways to write them in formats used by computers to generate timetables automatically. Even though many schools work in shifts, the constraint to include shifts in creating timetables is rarely discussed in literature. This paper discusses a way to formulate school shifts using the XHSST format, a way to modify a domain specific language to support shifts, and an example of a way to modify the mathematical model of integer linear programming to support working in several shifts.