Swimlanes
Containers that organize who does what: Pools (participants), Lanes (internal roles) and black-box Pools (external participants).
- Pool
The rectangular container representing a participant — an organization, system or role. A Pool contains one process (or is a black box) and talks to other Pools only through Message Flows.
- Lane
A subdivision inside a Pool that organizes activities by role, department or system. Sequence flows cross lanes freely — lanes assign responsibility, not communication boundaries.
- Black Box Pool
A Pool drawn empty: the participant exists and exchanges messages, but its internal process is hidden or unknown.