Sequence Diagram

Tags

modelling

Is a UML time-view diagram that illustrates the [see page 15, flow] of messages between object roles (rather than specific instances).

The flow of time in a sequence diagram is downwards, with messages being passed between roles. Rectangles indicate which role has focus and where the box ends there's an explicit return to the previous/calling role. At the start of the diagram there's a focus of control into the first role.

You can attach a [see page 19, loop guard] such as [i < n] to have control loop within a specific sequence.

Sequence diagrams have full procedural semantics meaning they can show sequence, selection, iteration and parallel processing. But their laborious to construct and vulnerable to change. It's often much easier to write code directly and visualise the sequence flow using code-visualisation tools.