Software Architect's Handbook

Event stream processing (ESP)

ESP involves analyzing streams of event data and then taking any necessary action based on that analysis. Events are screened based on various conditions and then either an action may be taken for the event or the event may be ignored. This type of processing is ideal for real-time flows in which decisions are also involved.

An example is a stock trading system in which an event takes place and enters an event stream when a stock ticker reports a change in price. Based on the price, an algorithm determines whether a buy or sell order should be created, and notifies the appropriate subscribers, if necessary.