omplex dynamic systems such as aircraft, power systems, and telecommunication networks present major challenges to control systems designers. Both the military and civilian sectors of our economy are demanding new and highly sophisticated capabilities from these systems that traditional controls technology is not offering. Among these capabilities are the following: • Adaptability/dynamic reconfigurability: Large-scale engineered systems must have the ability to quickly and gracefully react to a changing environment or to changes in their own configuration without compromising their operational integrity. Extreme performance dynamic systems must be able to support online switching of algorithmic components and rapid redirection of the interconnections among them, as well as changing the priorities at which information is flowing. This ability is particularly useful for hybrid control systems. • Plug-and-play extensibility: New advances are continually being made in control algorithm design, communications and sensor technology, and high-performance hardware platforms. To take full advantage of these innovations as they become available, we must be able to insert new technology into the system architecture without redesigning the components already in the system. • Interoperability: Today's control systems operate in distributed, heterogeneous environments; that is, the software components may be running on different processors, using different programming languages, hardware platforms, and network protocols, often over wireless links. Real-time communication must be provided among these distributed components while satisfying stringent constraints on bandwidth, response time, and reliability. • Openness: Reconfigurability and component interchangeability require software architectures that are flexible and that support tools and algorithms from a variety of sources and domains. This requires a shift away from traditional control system implementation, which tends to be practiced with a particular ap-June 2001 IEEE Control Systems Magazine 49