What is an activity diagram in software development

Chapter 3: The activity diagram

The all-round diagram of the behavior diagrams

As beautiful and illuminating as activity diagrams may be, they are only tools to get an overview of complex processes before programming. You cannot avoid programming these processes. Many developers therefore have difficulties getting used to the UML: It seems like doing everything twice. First you record processes in activity diagrams, then you have to create them again in a programming language.

The UML activity diagram is an aid to show processes step-by-step and clearly. However, that does not mean that you should now display everything you can find in activity diagrams. If you are clear about certain processes even without an activity diagram, then of course you do not need to create an activity diagram. However, if you have illustrated and thought through all the complicated processes using activity diagrams before entering the first line of the source code, all you need to do when programming is to translate your activity diagrams into the programming language. All problems and difficulties have already been resolved beforehand.

In fact, activity diagrams offer many more building blocks than can be presented in this book - building blocks that are very reminiscent of control structures used in many programming languages. The goal is one day to translate processes that are mapped in an activity diagram into source code at the touch of a button. We are still a long way from achieving this goal. Nowadays, a direct translation of diagrams into source code is actually only possible with class diagrams. You will learn about class diagrams in Chapter 4, The class diagram know the code generation - i.e. the creation of source code at the push of a button on the basis of class diagrams - in Chapter 5, Code generation.