Unified Modelling Language is a visual language for representing various aspects of a software solution. A very large and comprehensive language which would take considerable study to master. Here we walk though a general introduction.

We can use UML to model out current version of Spacebook. This model will show the classes in the Model package and their relationships. We are building this model after we have already the classes, however we could have composed the model before or concurrent with the implementation of the classes.

Taking the Spacebook application we have just modelled, we explore the introduction of the Commenting feature. We use UML to represent the design of the new class and its relationship to the existing classes.