The event trace description is captured in a system event/trace diagram, which shows interactions in terms of messages, or information transfers, between system nodes that are arranged in time sequence.

The event/trace diagram shows the system nodes involved in the scenario by vertical dashed lines, which are called system node event timelines. Horizontal line symbols between the system node event timelines represent the messages, or system events, that pass between the system nodes. The system events are drawn chronologically from the top of the diagram to the bottom; the horizontal placing or spacing of objects is arbitrary.