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Object-oriented design (OOD) is the process of planning a system of interacting objects for the purpose of solving a software problem. It is a method for software design. By defining classes and their functionality for their children (instantiated objects), each object can run the same implementation of the class with its own state.


An object contains encapsulated data and procedures grouped together to represent an entity. The 'object interface' defines how the object can be interacted with. An object-oriented program is described by the interaction of these objects. Object-oriented design is the discipline of defining the objects and their interactions to solve a problem that was identified and documented during object-oriented analysis.

What follows is a description of the class-based subset of object-oriented design, which does not include object prototype-based approaches where objects are not typically obtained by instantiating classes but by cloning other (prototype) objects. Object-oriented design is a method of design encompassing the process of object-oriented decomposition and a notation for depicting both logical and physical as well as state and dynamic models of the system under design.

Object-oriented design topics

Input (sources) for object-oriented design

The input for object-oriented design is provided by the output of object-oriented analysis. Realize that an output artifact does not need to be completely developed to serve as input of object-oriented design; analysis and design may occur in parallel, and in practice the results of one activity can feed the other in a short feedback cycle through an iterative process. Both analysis and design can be performed incrementally, and the artifacts can be continuously grown instead of completely developed in one shot.

Some typical input artifacts for object-oriented design are:

Object-oriented concepts

The five basic concepts of object-oriented design are the implementation-level features built into the programming language. These features are often referred to by these common names:

Designing concepts

Output (deliverables) of object-oriented design

A sequence diagram shows, as parallel vertical lines, different processes or objects that live simultaneously, and, as horizontal arrows, the messages exchanged between them, in the order in which they occur.

Some design principles and strategies

See also


  1. ^ a b Design Patterns: Elements of Reusable Object-Oriented Software. Addison-Wesley. 1995. ISBN 0-201-63361-2.
  2. ^ "What Is Object-Oriented Design?". Object Mentor. Archived from the original on 2007-06-30. Retrieved 2007-07-03.
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