Homework 2
CS422, Summer 2005


Due: Saturday, July 16

Please upload your solutions using the online turnin server. Note that file uploading will be disabled automatically after 11:59PM of the due date, so please turn in your work on time.


[Reading]
[Exercises]

1. (10pt) Figure 2.15 in the textbook shows a 4-way relationship about Births. Assume that a mother can give birth to more than one baby, and there could be more than one doctor and/or nurse present at the birth, discuss why the 4-way relationship is a bad design. [HINT: use your knowledge about how ER relationships are translated into relations, and how we determine whether a relation schema is good or not.]

2. (20pt) Exercise 3.6.1 (c) (e)

3. (20pt) Exercise 3.7.3 (b) (d)

4. (20pt) For a relation R(A, B, C, D), prove or give a counter-example of the following:
(a) If AB ->-> BC, then AB ->-> B and AB ->-> C
(b) If A ->-> BC, then A ->-> B and A ->-> C

5. (20pt) Exercise 5.2.4 (e) (f) (g) (h)

6. (10pt) Exercise 5.5.1 (c) (e)