This figure shows a typical event-driven system. At the center of this system is a real-time, even-driven application. The application accesses an analytical engine and datastores. The application subscribes to ordinary events from data sources such as sensors, devices, and data feeds such as news wire services. The application publishes notable events to data sinks such as user consoles (dashboards), event subscribers (other applications), and to a back-end cloud. A human operator executes queries on the application to address ad hoc, real-time issues such as: currency cross-rate calculation, detection of clustered stock movement, best-effort stock trading, and climate control.