Dr. Rangarajan began his career as a Chartered Accountant and took up MBA from the University of Berkley, USA. At the age of 30, his career took a turn when he realised he prioritised involvement and satisfaction in helping people in a constructive way.
Thus Sundaram Medical Foundation was born!
Dr. Rangarajan’s vision was to establish “a hospital, providing quality health care, which is cost-effective and community-centered, in an environment which is clean, caring and responsive to the needs of the patient”. His vision resulted in the creation of everything SMF is today, which serves as a ‘Role Model’ of health care delivery system in India.
Dr. S. Rangarajan
|Known for||Living By His Vision|
The book started at a birds of a feather (BoF) session at OOPSLA ’90, “Towards an Architecture Handbook”, run by Bruce Anderson, where Erich Gamma and Richard Helm met and discovered their common interest. They were later joined by Ralph Johnson and John Vlissides. The original publication date of the book was October 21, 1994 with a 1995 copyright, hence it is often cited with a 1995-year, despite being published in 1994. The book was first made available to the public at the OOPSLA meeting held in Portland, Oregon, in October 1994. In 2005 the ACM SIGPLAN awarded that year’s Programming Languages Achievement Award to the authors, in recognition of the impact of their work “on programming practice and programming language design”. As of March 2012, the book was in its 40th printing.
Chapter 1 is a discussion of object-oriented design techniques, based on the authors’ experience, which they believe would lead to good object-oriented software design, including:
- “Program to an interface, not an implementation.” (Gang of Four 1995:18)
- Composition over inheritance: “Favor ‘object composition‘ over ‘class inheritance‘.” (Gang of Four 1995:20)
The authors claim the following as advantages of interfaces over implementation:
- clients remain unaware of the specific types of objects they use, as long as the object adheres to the interface
- clients remain unaware of the classes that implement these objects; clients only know about the abstract class(es) defining the interface
Use of an interface also leads to dynamic binding and polymorphism, which are central features of object-oriented programming.
The authors refer to inheritance as white-box reuse, with white-box referring to visibility, because the internals of parent classes are often visible to subclasses. In contrast, the authors refer to object composition (in which objects with well-defined interfaces are used dynamically at runtime by objects obtaining references to other objects) as black-box reuse because no internal details of composed objects need be visible in the code using them.
The authors discuss the tension between inheritance and encapsulation at length and state that in their experience, designers overuse inheritance (Gang of Four 1995:20). The danger is stated as follows:
The create objects, rather than having to instantiate objects directly. This gives the program more flexibility in deciding which objects need to be created for a given case.
- Abstract factory groups object factories that have a common theme.
- Builder constructs complex objects by separating construction and representation.
- Factory method creates objects without specifying the exact class to create.
- Prototype creates objects by cloning an existing object.
- Singleton restricts object creation for a class to only one instance.
These concern class and object composition. They use inheritance to compose interfaces and define ways to compose objects to obtain new functionality.
- Adapter allows classes with incompatible interfaces to work together by wrapping its own interface around that of an already existing class.
- Bridge decouples an abstraction from its implementation so that the two can vary independently.
- Composite composes zero-or-more similar objects so that they can be manipulated as one object.
- Decorator dynamically adds/overrides behaviour in an existing method of an object.
- Facade provides a simplified interface to a large body of code.
- Flyweight reduces the cost of creating and manipulating a large number of similar objects.
- Proxy provides a placeholder for another object to control access, reduce cost, and reduce complexity.