Conclusion

In many ways, the Open/Closed Principle is at the heart of object-oriented design. Conformance to this principle is what yields the greatest benefits claimed for object-oriented technology: flexibility, reusability, and maintainability. Yet conformance to this principle is not achieved simply by using an object-oriented programming language. Nor is it a good idea to apply rampant abstraction to every part of the application. Rather, it requires a dedication on the part of the developers to apply abstraction only to those parts of the program that exhibit frequent change. Resisting premature abstraction is as important as abstraction itself.