This figure shows 5 boxes with 6 lines connecting them: 1) an arrow from a Publisher (Agent) box to a Topic (Subject Channel) box, 2) a "receive notification/message" arrow from the Topic to a Subscriber (Agent) box, 3) a "register" arrow from the Subscriber to the Topic, 4) a "subscribe" arrow from the Subscriber to the Topic, 5) a line between the Topic box and a Subscriptions box, and 6) a line between the Topic box and a Rules box.