# 程序代写代做代考 CS430/630 – Homework 6

CS430/630 – Homework 6

50 points

Due May 08 BEFORE CLASS

Instructions: Please submit paper copies (either typeset or hand-written copies are fine, as long as the

hand writing is clear).

Question 1 (15 points)

Suppose you are given a relation R with four attributes ABCD and the following set of FDs: AB→C, BC→D.

a. Identify the candidate key(s) for R (recall that keys must be minimal)

b. Determine if R is in BCNF, 3NF, or none of the above. If it is not in BCNF, decompose it into a

set of BCNF relations.

Question 2 (15 points)

Suppose you are given a relation R with four attributes ABCD and the following set of FDs: BC→A, AB→C,

C→DA.

a. Identify the key(s) for R (recall that keys must be minimal)

b. Determine if R is in BCNF, 3NF, or none of the above. If it is not in BCNF, decompose it into a

set of BCNF relations.

Note: For both questions, recall that it is not sufficient to consider the set of FDs that are given, but also

its closure.

Question 3 (20 points)

Show the grant diagrams after steps 7 and 8 of the sequence of actions below, where A owns the relation

on which the privilege p is assigned. Can C still exercise privilege p after step 8? What about E?

Step Executed by Action

1 A GRANT p TO B

2 A GRANT p TO C WITH GRANT OPTION

3 C GRANT p TO D WITH GRANT OPTION

4 A GRANT p TO D WITH GRANT OPTION

5 D GRANT p TO B WITH GRANT OPTION

6 B GRANT p TO C

7 D GRANT p TO E

8 A REVOKE p FROM C CASCADE