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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:
  1. Abstraction
  2. Encapsulation
  3. Modularity
  4. Hierarchy
  5. 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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