Activity diagrams - Introduction

Activity diagrams allow us to represent sequences of events or activities. It also allows us to represent parallel and conditional operations. It is not based on the class diagram so it is commonly used to represent use case’s in detail. The parallel and conditional parts are the most important ones to consider. Before we look at these we can look at a simple example of washing a dog.

Each box represents an activity which must be done. The two circles represent the start and end points of the activity diagram. These are the exact same symbols as used in a state diagram. The arrows show the order of the activities. There is no stipulation on the layout but most diagrams will go downwards rather than snake across the page.