1) What is a data model? What is the relational data model?

2) What is physical data independence? Please explain.

3) A university database contains information about professors (identified by emp_id) and courses (identified by course_id). Professors teach courses. Each of the following situations concerns the Teaches relationship set. For each situation, draw an ER diagram that describes it (assuming no further constraints hold).

a) Professors can teach the same course in several semesters, and each offering must be recorded.

b) Professors can teach the same course in several semesters, and only the most recent such offering needs to be recorded. (Assume this condition applies in all subsequent questions.)

c) Every professor must teach some course.

d) Every course is taught by exactly one professor (no more, no less).

e) Every professor teaches exactly one course (no more, no less), and every course must be taught by at least one professor.

f) Suppose that certain courses can be taught by a team of professors jointly. Model this situation by introducing additional entity sets and relationship sets if necessary. Here, we assume that only the latest semester of a course offering needs to be recorded.

4) A company database needs to store information about employees (identified by emp_num, with position, salary and phone as attributes), departments (identified by dept_num, with dept_name and budget as attributes), and children of employees (with name and age as attributes). Employees work in departments; each department is managed by an employee; a child must be identified uniquely by name when the parent (who is an employee; assume that only one parent works for the company) is known. We are not interested in information about a child once the parent leaves the company.

Draw an ER diagram that captures the above information.