To date, most of the fault-tolerant, real-time systems have been implemented in embedded settings, and there is an urgent need to open up this type of computing technology to a larger number of people who use heterogeneous distributed computing environments. Today's transportation, manufacturing, and communication systems require the integration of multiple embedded real-time control systems with standard distributed computing environments in a predictable fashion. Humboldt University has developed the concept of composite objects as a filtering bridge between standard middleware platforms and software frameworks providing services with certain quality-of-service (QoS) guarantees. Current research focuses on the Common Object Request Broker Architecture (CORBA) middleware platform; however, composite objects are also applicable to platforms like the Distributed Component Model (DCOM) and distributed computing environments (DCEs). Key concepts in Humboldt's approach are analytic redundancy, noninterference, interoperability, and ADAptive abstraction. These concepts originated in SEI work on the Simplex architecture and have been reapplied to extend the reach of commercial off-the-shelf (COTS) software technologies into demanding application settings (such as those found in military and industrial applications). Here, we discuss building blocks and techniques for fault-tolerant, real-time applications based on CORBA.

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