Exercise ER-4

Draw an ER diagram to represent the following entity types and the natural relationships among them (Focus on Supertypes and Subtypes): Vehicle, Land-vehicle, Air-vehicle, Water-vehicle, Ocean-vessel, River-raft, Helicopter, Rail-vehicle, Road-vehicle, Car, Airplane, Bicycle.

Exercise ER-5

Consider the following diagram:

1. What are the minimum and maximum number of Cs that can be associated with any one A? This is the same as asking What are the existence and cardinality for the C to A relationship?
2. Substitute A:person and B:manage and C:project in the above ER diagram. Suppose that someone told you that the following three facts are true. Are these consistent with the diagram? Answer yes or no for each of the three facts. If your answer is no, then explain why it is inconsistent.
   1. Mackenzie manages the Town project.
   2. Lindsey manages the City and International projects.
   3. Joe doesn't manage any projects.

Exercise ER-7

The following facts make up all of the leads relation between person and project:

• Jennifer leads the Southpark project.
• Jennifer leads the Briarwood project.
• Don leads the Eastgate project.

You do not know whether or not there are any other people or any other projects. Which diagram(s) that is (are) consistent with this set of three facts. For example, you might answer 1, 4 if both 1 and 4 are consistent with the above facts.

1

2

3

4