Event-based systems are increasingly gaining widespread attention for applications that require integration with loosely coupled and distributed systems for time-critical problems such as closed loop decision-making on operative levels with low latency. In this paper, we present the event processing language EAExpression for concisely defining event stream operations, such as filter conditions or formulas for calculating scores or measures. EAEx-pression is an expressive and easy-to-understand language for accessing and evaluating events both during the design phase (e.g. validating application artifacts such as rules, formulas and queries) as well as during the runtime of an event processing application. The language design aims particularily at business users by offering a user-friendly syntax and a comprehensive set of user functions. We demonstrate examples for typical applications of the language in various event processing components, such as in event-driven rules and business intelligence applications. © 2011 IEEE.