a. What is a trigger? How can triggers be used to enforce required children?
b. Explain why the enforcement of M-M relationships is particularly difficult.
c. Explain the need for each of the design decisions in Figure 6-33.
d. Explain the implications of each of the minimum cardinality specifications in Figure 6-38.
e. Explain the rationale for each of the entries in the table in Figure 6-40.
