You can use Pools and Lanes to show division of responsibilities or categories for processes and tasks.
Pools
A Pool is a graphical container for partitioning a set of processes and tasks from other pools, usually in the context of B2B situations. It is drawn as a square-cornered rectangle that is drawn with a solid single line. To help with the clarity of the diagram, a pool extends the entire length of the diagram, either horizontally or vertically. However, there is no specific restriction to the size and or positioning of a pool: pools do not have to be adjacent to one another; you can place space between adjacent pools.
The name of the pool is placed as a banner on the left side (for horizontal Pools) or at the top (for vertical Pools) with a line separating the name from the flow objects in the Pool.
“Black box” and “white box” pools
You can detail process flow within a Pool or choose to represent it as a “black box,” with no details shown. When you show details within the pool, you can consider it to be a “white box,” or open to inspection.
Even if you have not modeled any process flow details within a pool (and have a “black box” pool), you can still model how the pool interrelates to the outside world by drawing Message Flow lines from and to its borders, as shown in the figure below.
Pool definitions
A Pool is represented by a Definition of BPMN Participants. Through the Participant definition, you can specify that the Pool represents any of the following items:
•Application
•Function
•Organizational Unit
•Location
•Class
•Entity
Lanes
A Lane is a sub-partition within a Pool and extends the entire length of the Pool either vertically or horizontally. Lanes are used to organize and categorize activities within a Pool.
Lane definitions
A Lane is represented by a definition of BPMN participants: see Definition of BPMN Participants. Through the participant definition, you can specify that the Pool represent any of the following items:
