CRC cards record Class Responsibility Collaboration information for the class. Stereotype refers to a particular application. Templates are parametrised classes. LectureCourseOptions is a class giving course options for a particular lecturer. AddACourseOffering is a class that deals with adding a new course for a Lecturer. Course is a class representing the course. CourseOffering is a class that deals with different parts of a course. LecturerCourseManager is a class to manage courses offered by a lecturer. LecturerInformation: class containing details of a team. StudentInformation: class containing details of students. Objects are items of a running system; objects get manipulated during the run. Real objects are represented by system objects. Class provides the type of its objects and determines the characteristics of an object. Instantiation creates an object of the class. A variable is to type as an object is to class. While type operations need no implementation class methods need implementations. Inheritance simplifies class implementations in system development. Problem domain Objects are realized by classes in the system. System software classes are files, windows, icons, ... Information system classes are customer, invoice, asset, quote, ... Technical system classes are engine, sensor, display, buttons, ...