Appendix A. An Introduction to UML

A number of the lessons in this book use Unified Modelling Language (UML) diagrams to illustrate the relationships between classes, the interactions between objects, and other types of relationships and events. If you don't know the UML, this appendix offers an accelerated introduction to the UML and the essentials of creating models using the UML. Alternatively, if you do know the UML, you will find this appendix offers a quick reference to the most commonly used elements of the language—the ones used throughout this book.