BPMN Elements :: Events


An event is a signal that something happened, and BPMN lets you say how the process should respond.

The Events can occur at:

  • the beginning of the process – Start Events
  • the end of the process – End Events
  • in the middle of the process – Intermediate

Catching and Throwing Events

  • Catching Events ask for data objects from “a container”.
  • Throwing events launch data objects to “a container”.

Boundary Events

Some events can happen on the Boundary of an activity.
This indicates that the event can interrupt the activity, and will divert the sequence flow from the “normal” flow to another flow.
Boundary events are catching events that are attached to an activity (a boundary event can never be throwing). This means that while the activity is running, the event is listening for a certain type of trigger. When the event is caught, the activity is interrupted and the sequence flow going out of the event are followed.
The following picture depicts a process of ordering some products which includes a Start event, an Intermediate message event, a Boundary Timer event, and End events.

Full Set of BPMN Events:

Start Events

A Start Event indicates where a particular process starts. Start Event starts a flow of a process, and cannot have any incoming flows.
When a Start Event is owned by an Event SubProcess, it can be:

  • Interrupting.The Start Event interrupts the process contained in the Event SubProcess.
  • Non-Interrupting.The Start Event does not interrupt the process contained in the Event SubProcess and starts parallel flow.

Interrupting / Non-Interrupting symbols example:

Start Events:

Intermediate Events:

End Events:


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