数据库系统基础教程第四章答案

c)

d)

4.7.3

4.7.4

4.7.5

Males and Females subclasses are complete. Mothers and Fathers are partial. All subclasses are disjoint.

4.7.6

4.7.7

4.7.8

We convert the ternary relationship Contracts into three binary relationships between a new entity set Contracts and existing entity sets.

4.7.9 a)