Abstract: Recent literature on the architectures of real-time systems reveals striking similarities among designs used in many different domains, including avionics, satellites, process control, signal processing, power generation, and manufacturing. This paper presents an architecture style that can be used for a large class of real-time event processing systems. It gives the common requirements of these systems, the major design patterns shaping the architecture, and the rationale leading from the requirements to the chosen patterns. Although most of the design patterns could be used individually to define stand-alone architecture styles, collectively the requirements and design patterns have many interrelationships that make this an architecture style worth documenting and studying. The paper ends with brief discussions of three previously published systems that have similar architectures