This book Object Oriented Analysis and Design with UML Patterns is designed for undergraduate and postgraduate students of Computer Science and Engineering, Information Technology, and Master of Computer Applications (MCA). Object Oriented Analysis and Design (OOAD) is a language which provides a powerful tool for building flexible and extensible software components. Software development is a team effort, and it is equally important that developers have a language for talking about analysis and designs. It is a language which is able to deal in requirements and high level design without being cluttered by the fine detail of program code. It refers to the application of object oriented modeling to the analysis of systems and designing object oriented systems fulfilling these requirements. The system may be virtually anything including an organization (e.g. a company), a business unit, a software system which exists or one for which the requirements specification are written, a data warehouse or even a hardware system.