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.