Sequence Diagram - Drive Black Box

The Sequence diagram is a type of Interaction diagram and describes the way the Driver interacts with the vehicle in a particular context. The elements that participate are, by convention, listed from left to right on the horizontal access of the diagram, and time proceeds vertically in the diagram. The dotted lines that emanate from the objects are called lifelines and represent the time the elements are in existence.

This diagram uses a type of element called a Reference, which acts as a place holder for another Sequence Diagram. Enterprise Architect conveniently allows these diagrams to be opened by double-clicking on the 'ref' element in the diagram.

The diagram utilizes a Parallel (par) Combined Fragment to specify that the Control Speed and Steering interactions occur at the same time (in parallel). The diagram also uses a Combined Fragment with a designation of Alternative (alt) which specifies a number of (alternative) ways that the driver can control the speed.

Enterprise Architect allows the Sequence Diagram to be defined as a child of the 'Drive the Vehicle' Use Case making it easy for a modeler to access the diagram and view it in the context of the goal the Driver is wanting to achieve with respect to the vehicle.