15.7. Basic Sequence Diagram Notation

Links

Unlike collaboration diagrams, sequence diagrams do not show links.

Messages

Each message between objects is represented with a message expression on an arrowed line between the objects (see Figure 15.17). The time ordering is organized from top to bottom.

Figure 15.17. Messages and focus of control with activation boxes.

Focus of Control and Activation Boxes

As illustrated in Figure 15.17, sequence diagrams may also show the focus of control (that is, in a regular blocking call, the operation is on the call stack) using an activation box. The box is optional, but commonly used by UML practitioners. ...

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