Events (BPMN)

An event is something that happens during the course of a process. Events include the start and end of an activity, and any other intermediate happening (such as a change of state or receipt of a message) which will affect its sequence or timing. You can create events in collaboration, process, and choreography diagrams.

The following types of events are available:

None - Untyped events, which indicate start points, state changes, and final states.
Message - Receiving and sending messages.
Timer - Cyclic timer events, points in time, time spans, or timeouts.
Escalation - Escalating to a higher level of responsibility.
Conditional - Reacting to changed business conditions or integrating business rules.
Link - Off-page connectors. Two corresponding link events equal a sequence flow.
Error - Catching or throwing named errors.
Cancel - Reacting to cancelled transactions or triggering cancellation.
Compensation - Handling or triggering compensation.
Signal - Signalling across different processes. A signal thrown can be caught multiple times.
Multiple - Catching one out of a set of events. Throwing all events defined.
Parallel multiple - Catching all out of a set of parallel events.
Terminate - Triggering the immediate termination of a process.

Creating Events

Each type of event can be created in one or more different contexts:

Start events:
- Top-level - Create the event with its Toolbox tool.
- Event sub-process interrupting - Create the event with its Toolbox tool within an event sub-process.
- Event sub-process non-interrupting - Create an interrupting event sub-process, right-click the symbol, and select Change to Non-Interrupting.
  
  Alternately, open the event property sheet and deselect the Interrupting checkbox.
Intermediate events:
- Catching - Create the event with its Toolbox tool.
- Boundary interrupting - Right-click a sequence flow and select Add Boundary Event > Type.
  
  Alternately, open the property sheet of a sequence flow, click the Condition tab, click the Create tool to the right of the Event field, and select the appropriate type of event in the Stereotype field of the event property sheet.
- Boundary non-interrupting - Create a boundary interrupting event, right click the symbol, and select Change to Non-Interrupting.
  
  Alternately, open the event property sheet and deselect the Interrupting checkbox.
- Throwing - Create a catching event, right-click the symbol, and select Change to Throwing Event.
  
  Alternately, open the event property sheet, click the Implementation tab, and select Generate event in the Type field.
End events - Create the event with its Toolbox tool.

Event Types

The following table shows the symbols of all the types of events available in each context:

Type	Start			Intermediate
	Top-Level	Event Sub-Process		Catching	Boundary		Throwing
	Top-Level	Interrupting	Non-Interrupting	Catching	Interrupting	Non-Interrupting	Throwing
None
Message
Timer
Escalation
Conditional
Link
Error
Cancel
Compensation
Signal
Multiple
Parallel Multiple
Terminate

Events are based upon and share the properties of starts (see Starts (BPM)), processes, (see Processes (BPM)), or ends (see Ends (BPM)), as appropriate.

Note: You can change the type of an event by selecting a different stereotype from the Stereotype list on the General tab of its property sheet, or by right-clicking its symbol and selecting the appropriate Change to... command.