The trend towards the use of object-oriented methods for software systems development has made it necessary for the use of object-oriented approaches in object-oriented software systems development. Class diagrams represent an essential component in any object-oriented system design. The development of such class diagrams in a systematic way is very crucial in an object-oriented development methodology. The main principles used in obtaining these class diagrams in a systematic way are described. Class diagrams are very essential in object-oriented development practice.