Exception Flow

Intro

In BPMN, an exception flow is a sequence path that starts from a boundary intermediate event attached to an activity. It matters because it makes interrupt handling explicit and predictable.

Key points:

• Activates only when the boundary event is triggered.
• Separates normal flow from exception handling logic.
• Common use cases: cancellation, error recovery, timeout handling.
• Pitfall: missing completion paths from exception branches.

Examples:

• Timeout on data load routes to rollback steps.
• Error event on payment task routes to retry queue.
• Cancellation message routes to customer notification.

In practice:

Attach boundary events to the correct scope and ensure exception branches rejoin or complete cleanly.

Related terms: boundary-event; intermediate-event; compensation-flow

FAQs:

Q: Does an exception flow always interrupt the task?
A: Interrupting boundary events do; non‑interrupting variants do not stop the task.

Q: Can there be multiple exception flows on one activity?
A: Yes; each boundary event can define a separate exception path.

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