UML Distilled: A Brief Guide to the Standard Object Modeling Language, Third Edition

Chapter 4. Sequence Diagrams

Interaction diagrams describe how groups of objects collaborate in some behavior. The UML defines several forms of interaction diagram, of which the most common is the sequence diagram.

Typically, a sequence diagram captures the behavior of a single scenario. The diagram shows a number of example objects and the messages that are passed between these objects within the use case.

To begin the discussion, I’ll consider a simple scenario. We have an order and are going to invoke a command on it to calculate its price. To do that, the order needs to look at all the line items on the order and determine their prices, which are based on the pricing rules of the order line’s products. Having done that for all the line ...