Mechanisms for catching exceptions in BPMN

BPMN provides two mechanisms for catching exceptions—the boundary event and the event sub-process. The semantics of these two mechanisms are quite different, and they should be used in different circumstances.

Boundary events

The boundary event can be attached to an activity or to an embedded sub-process. It provides a mechanism to capture an event, message, or signal if it occurs while the activity or sub-process that the boundary event is attached to is being executed. Boundary events can be defined as interrupting or non-interrupting .

When an event is caught by an interrupting boundary event, the task or sub-process execution is suspended, and execution continues with the first task attached to the default flow from the boundary event. When an event is caught by a non-interrupting boundary event, then the task or sub-process execution continues and a new thread of execution starts from the activity after the boundary event.

Interrupting boundary...