IS-A Relationship and attribute inheritance in EER modeling

IS-A relationship supports attribute inheritance and relationship participation.In the EER diagram, the subclass relationship is represented by IS-A relationship. Attribute inheritance is the property by which subclass entities inherit values for all attributes of the superclass.

Importance of attribute inheritance:

This important property makes it unnecessary to include supertype attributes redundantly with subtype that is

1. It is easy to identify supertype and subtype entities.

2. The unique attributes are related with only subtype entities.

 

In the above EER diagram the supertype (or) super class has two subtypes or sub-classes which form a parent and child relationship. It is transformed as IS-A relationship. That is by means of attribute inheritance is a relationship can be achieved. The circle indicates IS-A relationship.