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Object-oriented Programming in C#
Specialization, Extension, and Inheritance
The extension of class specialization

The extension of a specialized class B is a subset of the extension of the generalized class A


The extension of a class A is narrowed when the class is specialized to B

  • The is-a relation

    • A   B-object   is an   A-object

    • There is a is-a relation between class A and B

The is-a relation forms a contrast to the has-a relation

The is-a relation characterizes specialization

The has-a relation characterizes aggregation