Object-oriented design

Object-oriented design is the process of planning a system of interacting objects for the purpose of solving a software problem. It is one approach to software design.
Overview.
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 that are built into the programming language. These features are often referred to by these common names: