Section IV. Please answer three of the following questions in 5-6 lines (100 words) (7X3 = 21 points)

a. What is data integrity, and what is the significance of a lack of data integrity?

b. What is the difference between controlled and uncontrolled redundancy?

c. What is the difference between logical and physical data independence?

d. Why is it useful to know all the candidate keys of a relation schema?

e. What is the difference between a desirable and an undesirable functional dependency? Describe the nature of the problems caused by undesirable functional dependencies. What prevents us from simply ignoring undesirable functional dependencies?