he Enhanced Entity Relationship Model contains all the features of the Entity Relationship model. In addition to all that, it also contains features of Subclasses, Superclasses and Inheritance.
All of these in detail are as follows −
A subclass is a class derived from the superclass. It inherits the properties of the superclass and also contains attributes of its own. An example is:
Car, Truck and Motorcycle are all subclasses of the superclass Vehicle. They all inherit common attributes from vehicle such as speed, colour etc. while they have different attributes also i.e Number of wheels in Car is 4 while in Motorcycle is 2.
A superclass is the class from which many subclasses can be created. The subclasses inherit the characteristics of a superclass. The superclass is also known as the parent class or base class.
In the above example, Vehicle is the Superclass and its subclasses are Car, Truck and Motorcycle.
Inheritance is basically the process of basing a class on another class i.e to build a class on a existing class. The new class contains all the features and functionalities of the old class in addition to its own.
The class which is newly created is known as the subclass or child class and the original class is the parent class or the superclass.