Exercises 2.2 and 2.3 from Ramakrishnan & Gehrke, reproduced here for your convenience, and due September 10.

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2.2  A university database contains information about professors (identified by social security number, or SSN) and courses (identified by courseid). 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). 

[Note: each of the six situations needs a separate ER diagram -- pld]

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

2. 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.)

3. Every professor must teach some course.

4. Every professor teaches exactly one course (no more, no less).

5. Every professor teaches exactly one course (no more, no less), and every course must be taught by some professor.

6. Now suppose that certain courses can be taught by a team of profesors jointly, but it is possible that no one professor in a team can teach the course. Model this situation, introducing additional entity sets and relationship sets if necessary.

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2.3  Consider the following information about a university database:

* Professors have an SSN, a name, an age, a rank, and a research specialty.

* Projects have a project number, a sponsor name (eg NSF), a starting date, an ending date, and a budget.

* Graduate students have an SSN, a name, an age, and a degree program (eg MS or PhD).

* Each project is managed by one professor (known as the project's principal investigator).

* Each project is worked on by one or more professors (known as the project's co-investigators).

* Professors can manage and/or work on multiple projects.

* Each project is worked on by one or more graduate students (known as the project's research assistants). 

* When graduate students work on a project, a professor must supervise tehir work on the project. Graduagte students can work on multiple projects, in which case they will have a (potentially different) supervisor for each one.

* Departments have a department number, a department name, and a main office.

* Departments have a professor (known as the chair) who runs the department.

* Professors work in one or more departments, and for each department theat they work in, a time percentage is associated with their job.

*Graduate students have one major department in which they ar e working on their degree. 

* Each graduate student has another, more senior graduate student (known as a student advisor) who advises him or her on what courses to take.

Design and draw an ER diagram that captures the information about the university. Use only the basic ER model here; that is, entities, relationsihps, and attributes. Be sure to indicate any key and participation constraints.