BPMN event

A BPMN event in a business process diagram refers to something that happens and affects the flow of process. There are three types of events to use in business process modeling: Start, intermediate and end.

Start, intermediate and end events with different kinds of triggers and results

Start event

A start event indicates the place where and possibly why a process start. Since start event is used for initiating a process, it does not have any incoming sequence flow.

You can define a trigger for start event, to show the condition(s) that will cause a process to initiate.

Trigger name Representation Description None The none start event does not have a defined trigger. Message This trigger starts the process by receiving a message from a participant. Timer This trigger starts the process in a specific time-date or a specific cycle (e.g. every Friday). Error This trigger starts an in-line event sub-process when an error occurs. Note that this trigger can only be used with an event-sub-process. Escalation This trigger starts or not to start an in-line event sub-process when the constraint specified is not satisfied. Note that this trigger can only be used with an event-sub-process. Compensation This trigger starts an in-line event sub-process when an compensation occurs, which requires undoing some steps. Note that this trigger can only be used with an event-sub-process. Conditional This trigger starts the process when a specific condition becomes true. Signal This trigger starts the process when a signal broadcasted from another process has arrived. Note that signal is different from message in the sense that it has a specific target for message. Multiple This means that there are multiple triggers of the process. Any one of them can cause the process to start. Parallel Multiple This means that there are multiple triggers of the process. All of the triggers must be triggered in order to start the process. Link This trigger provides a means to connect the end result of one process to the start of another.

Different types of start event trigger

Defining a trigger

To define a trigger on an event, right click on the event and select Trigger, then click on the type of trigger from the popup menu.

To define a start event trigger

If you want to edit the properties of the trigger, such as the condition of a conditional trigger, right click on the event and select Open Specification... from the popup menu. Then, click on the ... button next to the drop down menu of Trigger to edit its properties in the popup dialog box.

Interrupting or Non-interrupting event sub-process

Start event can be attached to the border of an event sub-process to initiate the sub-process inline. You can define this kind of trigger as either interrupting or non-interrupting, which means to interrupt its containing process or not to interrupt its containing process respectively. To set a trigger to be Interrupting or Non-Interrupting, right click on the event and select/de-select Triggers > Interrupting from the popup menu.

Interrupting (left) and Non-Interrupting (right) events

Intermediate event

An intermediate event indicates where something happens in between the start and end event of a process. You can use an intermediate event to show where messages are received or sent, show the necessary delay, perform exception handling and show the need of compensation. You can place an intermediate even in two places: Attaching the boundary of task/sub-process, Normal flow (i.e. connected from a flow without attaching to an activity).

Trigger name Representation Description None The none intermediate event does not have a defined trigger. It is used to indicate change of state in the process. You can only use a none intermediate event in a normal flow. Message This trigger represents either a send or receive of message Timer This trigger acts as a delay mechanism on a specific date-time or cycle (e.g. every Friday). You can only use a timer intermediate event in a normal flow. Error This trigger reacts to a named error or to any error if no name is specified. Escalation The trigger indicates where an escalation is raised. You can only use an escalation intermediate event in a normal flow. Cancel This trigger will be fired when a cancel end event is reached within the transaction sub-process. It also shall be triggered if a Transaction Protocol "Cancel" message has been received while the Transaction is being performed. Compensation The trigger indicates the need of compensation. Conditional The event will be triggered when the condition specified become true. Link This trigger is used for linking two sections of a process. You can use it to mode a looping of flow or to avoid having long sequence flow connectors appear on diagram. You can only use a link intermediate event in a normal flow. Signal This trigger indicates the sending or receiving of signals, which is for general communication within and across process levels, across pools, and between business process diagrams. Multiple This means that there are multiple triggers defined. Any one of them can cause the event to be triggered. Parallel Multiple This means that there are multiple triggers defined. All of the triggers must be triggered in order to trigger the multiple event.

Different types of start event trigger

Defining a trigger

To define a trigger on an event, right click on the event and select Trigger, then the type of trigger from the popup menu.

To define an intermediate event trigger

If you want to edit the properties of the trigger, such as the condition of a conditional trigger, right click on the event and select Open Specification... from the popup menu. Then, click on the ... button next to the drop down menu of Trigger to edit its properties in the popup dialog box.

Throw and catch

You can set an event to be catch or throw. Catch means to react to a trigger, while throw means to create a trigger. To set, right click on an event and select Trigger, then either Catching or Throwing from the popup menu.

A catch event (left) and a throw event (right)

Interrupting or Non-interrupting event

Intermediate event can be attached to the border of an activity. You can set an event to interrupt or not to interrupt the activity to which it is attached. To set a trigger to be Interrupting or Non-Interrupting, right click on the event and select/de-select Triggers > Interrupting from the popup menu.

Interrupting (left) and Non-Interrupting (right) events

End event

As an opposite of start event, end event indicates where a process will end. Since end event is used for terminating a process, it does not have any outgoing sequence flow.

You can define a result for end event, to show what will happen when reaching the end.

Trigger name Representation Description None The none end event does not have a defined result. Message This result ends the process by sending a message to a participant. Error This result indicates the generation of a named error when the process ends. Escalation This result indicates the trigger of escalation when the process ends. Cancel This result indicates that the transaction should be cancelled. Compensation This result indicates the need of compensation, which require undoing some steps. Signal This result indicates that a signal will be broadcasted when the process ends. Note that signal is different from message, which has a specific target for message. Terminal This result indicates that all activities in the process should be immediately ended. Multiple This result indicates that there are multiple consequences of ending the process. Link This result provide a means to connect the end result of one process to the start of another.

Different types of end event result

Defining a result

To define a result on an event, right click on the event and select Result, then the type of result from the popup menu.

To define an end event result

If you want to edit the properties of the result, such as the message produced by a message result, right click on the event and select Open Specification... from the popup menu. Then, click on the ... button next to the drop down menu of Result to edit its properties in the popup dialog box.

Related Resources

The following resources may help you to learn more about the topic discussed in this page.

• BPMN tutorials that teaches you how to operate with the BPMN tools
• What is BPMN? - An introductory guide to BPMN
• Visual Paradigm on YouTube
• Contact us if you need any help or have any suggestion