Tasks

A Task is an atomic activity that is included within a process. A task is used in a BPMN diagram if the process can not be specified on a finer level of process model detail.
Generally, an end-user and/or an application are used to perform the task when it is executed.

As already mentioned above, tasks are atomic from business point of view. However, from an execution point of view, this is not generally true. Actually, it is only true, if the task corresponds to a synchronous service call.
In all other situations the task has to wait for a signal that the task has been done. Thus, the beginning of a task corresponds generally to a state waiting for a signal. At state entry, the task has to be triggered, i.e. by sending a notification.
A task is mapped in a state with an entry handler and, depending on the task type, a signal with a signal handler. Signal and signal handler are indicated on the transition by (...)/(...).

The handler of the state entry just calls an operation <task name>Begin.
This operation logs the event of the beginning of this task. It is overridable so that own handling can be implemented.

The signal handler calls an operation <task name>End when leaving the state.
The task may deliver new data as result. These data are transmitted by the signal in the attribute 'message' of type Any.
As before this operation logs the event of leaving this task. It is overridable so you can implement your own handling.

The abstract <<PersistentState>> class contains the overridable operations that are invoked by each of the handlers.