A basic goal in Finnish school timetabling is to construct a one-week schedule, which is repeated the whole season. A timetable consists of lessons of subjects. A lesson is a predefined combination of a student group, a teacher, a room and the duration of the lesson.
In Finnish high schools, every student belongs to one base group and most of her lessons are scheduled based on this group. In addition, she belongs to a number of optional groups, which are constructed based on students’ choices. For example, one student prefers to take optional courses in Science and in Sports and the other in Art and Music. Every lesson is assigned to one and only one group, either base or optional. Base and optional groups define a matrix, which in turn determines which groups can and cannot have lessons at the same time.
In all Finnish school levels teachers are preassigned to lessons. Typically also rooms are preassigned to (most of the) lessons. This is because a teacher prefers to teach the given subject in some specialized room or she prefers to have most of her lessons in the same room.
A typical curriculum of a Finnish high school student consists of ten subjects and each subject is taught two to six hours each week. Lessons of a subject can take either one or two hours and only in uncommon cases three hours. Hence, most of the subjects are taught either in two, three or four days each week.
Compact scheduling for students (student groups) is necessary and breaks are either strictly prohibited or highly inappropriate. Teacher breaks are allowed, but still unappreciated. Several teachers also prefer not to teach more than a given number of hours in a day.
An additional problem is that some of the subjects/lessons may last the whole season while the others last only part of the season. Some of these part-season-lessons must precede others, that is, some lessons cannot start until all the lessons of a particular subject have been given.
Preassignment of teachers and rooms, a somewhat complicated structure of student groups and the demand for compact scheduling make Finnish School Timetabling Problem a challenge for both a manual solver and a computer software.