Question

1. Give examples of 1:1, 1:N, and N:M relationships (other than those presented in chapter 5). Draw two E-R diagrams for each of your examples: one using the traditional diamond notation and one using IE Crow’s Foot notation.

2. Describe the relationship between the structure of forms and reports and the data model.

3. Explain the difference between IS-A and HAS-A relationships.

4. Explain why the data modeling process must be iterative. Use the Highline University example.

Answer 1

Solution 1:-

Solution 3:-

An IS-A relationship is inheritance. The classes which inherit are known as sub classes or child classes. On the other hand, HAS-A relationship is composition.

In OOP, IS-A relationship is completely inheritance. This means, that the child class is a type of parent class. For example, an apple is a fruit. So you will extend fruit to get apple.

On the other hand, composition means creating instances which have references to other objects. For example, a room has a table. So you will create a class room and then in that class create an instance of type table

A HAS-A relationship is dynamic (run time) binding while inheritance is a static (compile time) binding. If you just want to reuse the code and you know that the two are not of same kind use composition. For example, you cannot inherit an oven from a kitchen. A kitchen HAS-A oven. When you feel there is a natural relationship like Apple is a Fruit use inheritance.

Solution 4:-

Please like the answer if you are satisfied.

Your appreciation really matters to me.

Thanking you Sir/Madam.