What are the main building modules of the Entity Relationship model? Discuss each one.

What is a weak entity, and how is it represented in an E-R diagram? Give an ex.

What three (often conflicting!) database requirements must be addressed in database design?

Given the following business rules, create the appropriate E-R diagram for each of the specified relationships:

(Teacher's note: Since many relationships and cardinalities are determined by an organization's business rules, some students will produce E-R diagrams that are different from those presented here. You can use this problem to illustrate how business rules shape the database blueprint and why, therefore, the development of these business rules is a critical activity to database designers).

A company operates four departments.

Each department in part (a) employs employees.

Each of the employees in part b may or may not have one or more dependents.

Each employee in part (c) may or may not have an employment history.