Relation | Label | Visualization | Semantics |
Sequence | seq (default: no label) |
| An Activity and the result of an Activity are interchangeable: its Outcome does not need to be modeled explicitly. An exception to this is when the Outcome of an Activity is used in another Activity: then Outcome must be modeled explicitly, adding “produces” or “consumed by” relations to the label of the arrow. Note that the Outcome can be used as a synchronization mechanism: the Outcome can be consumed only if it has been produced. |
Parallel | par, join |
| Activity B and C are executed concurrently. After both activities have ended, execution continues with activity D. |
Synchronization | sync |
| The sync relation is used to indicate that two parallel activities are synchronized. In this process, information can be exchanged between the two activities. Activity B is temporarily on hold until the sync signal is or has been received from activity A. |
Guard | [conditional expression] |
| [Conditional expression]: path may be taken if the expression evaluates to true. The guard is used as a prefix for the other temporal relations. |