====== ER - exercises ======

We want to design data model of university. There are persons. We register the
name of person, address, date of birth, and a comment for every person.
Students, teachers and staff are persons. We register the date of beginning of
study, the semestr and the department for every student. We register position,
specialization and salary for avery teacher. We register salary and competence
for staff.

There are departments on university. Every department has name, abbreviation
and description. Departments offer courses. We register the name, abbreviation and
description for every course.

Student can subscribe many courses. Course can be subscribed by many
students.

Teacher can teach many courses, but course can be tought by only one teacher.

Teachers work on department. Every teacher can work on one department. Some
teachers are the chiefs of particular departments. Department can be managed
byone teacher and teacher can manage at most one department.

There are laboratories on university. Laboratory has its name, abbreviation and
description. Staff is responsible for laboratories. One person working as staff
can be responsible for many laboratories. One laboratory can be managed by
many staff persons.

Teacher can be a manager of staff person too. Teacher can be manager of many
staff persons, but staff person is nanaged by at most one teacher.
There are a seminar rooms on university. Seminar room belongs to department. It
has its number, capacity and description. Seminar room is identified by its
number. But this number is unique only on the scope of department.