Glossary · Systems engineering and MBSE
Activity diagram
German: Aktivitätsdiagramm
In SysML and UML, an activity diagram is a behavior diagram that shows the flow of actions, control and objects (material, energy, data) through a process, including decisions, parallel paths and the elements responsible for each action.
- Systems engineering
In one sentence
An activity diagram shows the flow of actions, control and material or data through a process, including decisions and parallel paths.
Example
An activity diagram of a tool change shows the steps from 'request tool' to 'confirm clamping', with a decision branch for a missing tool and parallel coolant shut-off.
How it applies
- Engineering: Activity diagrams describe functional flows before they are allocated to blocks; swimlanes (partitions) show which element performs each action.
- Automation: They are a common way to sketch sequences that later become Sequential function chart (SFC) or state logic in the controller.
- Documentation: Activity diagrams map well to procedures; the documentation team can derive task topics and flowcharts from reviewed diagrams, provided the model is the released version.
Activity diagram vs. state machine diagram
An activity diagram shows a flow of actions; a State machine diagram shows the states an element can be in and the events that move it between them. Operating modes are usually better modeled as states, procedures as activities.