BPMN pools and lanes
A pool is a participant, usually a whole organisation or system. A lane subdivides a pool into roles. Between pools you can only send messages, which is exactly right: you cannot control another company's process.
That constraint is the single most useful thing about BPMN.
#When it matters
Cross-organisation processes.
Any process where the handoffs are the interesting part.
#The symbols
Symbol | Means |
|---|---|
Pool | A participant. Contains a whole process, or is drawn as a black box. |
Black box pool | Collapsed, with no internal detail. The usual way to show a customer. |
Lane | A role or system inside a pool. |
Message flow | The only connection allowed between two pools. |
#A few things that catch people out
Draw external participants as black box pools. You do not know their internal process, and pretending you do is misleading.
One process per pool. Two processes in one pool is a modelling error.
Lanes are organisational, not technical. They do not change execution.
#Related
Sequence flow stays inside the pool.
