INHERITANCE(GENERALIZATION): “Extracting common features of all the classes

Into a base class & inheriting original classes

From this new class”

For instance, the common attributes of patient, doctor and hospital staff are extracted into “person” class.

ABSTRACTION: “Capturing only those details about an object

That are relevant to current perspective.”

In the preceding example a person can has his height, complexion,eye color as an attribute but this is irrelevant for a patient and a doctor being an object.

OVER-RIDING: “Extending, limiting or improving the default

Behavior of the base class”

In the given class of hospital staff, the administrative duties are limited only to the admin staff & the assistance duties are limited only to the medical staff.

SUB-TYPING: Says that “The derived class is behaviorally in compatible with

The base class & can replace it”

In the given example the outdoor treatment class & the admission +treatment class have nearly the same attributes as that of the base class.

SPECIALIZATION:Says that “the derived class is behaviorally incompatible

With the base class & can’t replace it”.

In the preceding example, the patient class has a unique feature i.e. its medical history & ongoing treatment. That’s why it can’t replace the person class. Similarly, the doctors’ class has its own attributes, making it incompatible with the person class.

ONE-WAY ASSOCIATION:It’s a relationship between two objects of different classes in which one objects serves the other. As in the given example doctors serves the patients by providing treatment.

TWO-WAY ASSOCIATION:It’s a type of association in which both objects serve each other. For instance, doctor treats the patient and the patient in turn pays the doctor.

AGRREGATION:The relationship between the container & the contained object is called aggregation. Its a weaker relationship because the aggregated components can exist independently. In the given example the

equipment class and the ward/room class is aggregated into the admission class.

POLYMORPHISM: “a function having the same name but different functionalities is said to be showing polymorphism.”

For instance, the function having the name “registration in the person class performs different function in context of derived classes. In patient class it takes the input as the entry

date,time,treatment etc.while in doctors class it is concerned with doc designation, his id etc.