It is often desirable or even necessary to execute things in parallel. For this purpose, BPEL offers the flow activity.
(Note that besides the flow activity, the parallel variant of forEach activity and event handlers allow multiple instances of its child activity to run in parallel.)
A link can have a transition condition associated with it which influences its status. If no transitionCondition is specified, the status of the link is true. If a transitionCondition is specified, it will set the status of the link.