A Note on Object Oriented System Development

Object oriented system development consists of

Object Oriented Analysis
Object Oriented Information Modeling
Object Oriented Design
Prototyping and Implementation
Testing, Iteration and Documentation

Five major elements of Object Model:

Abstraction
Encapsulation
Modularity
Hierarchy
Inheritance

Image Courtesy Codeproject

Abstraction

Abstraction is one of the fundamental elements of object model.

Three types of abstraction are- Entity Abstraction, Virtual machine abstraction, Coincidental abstraction.

Encapsulation

Encapsulation is the process of compartmentalization the elements of an abstraction that constitutes its structure and behavior and serves to separate the contractual interface of abstraction and its implementation.

Modularity

Modularization consists of dividing a program into modules which can be compiled separately , but which have connection with other modules.

The connections between modules are the assumption which the modules make about each other.

Cohesion is the interdependency within a module and coupling is the dependency between modules.

Good design stipulates 'high cohesion and low coupling'.

Languages and modules:

-C++ has separately compiled files like .h,.cpp with dependencies through #include

-Java supports packages

-.NET has namespaces

Hierarchy

Set of abstractions forms a hierarchy and by identifying hierarchies , we simplify the understanding of our problem.

Hierarchy is the ordering of abstractions.

Inheritance

Inheritance is an important "is-a" hierarchy and defines relationships among classes, wherein one class shares the structure and behavior defined in another class.

Subclasses inherit from one or more superclasses .

A subclass typically redefines or augments the existing structure and behavior of its superclasses.

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