Asynchronous Decentralized Real-Time Computer Systems

A new generation of real-time computer systems performs physically and logically decentralized mission management—such as semi-autonomous entities collaboratively performing manufacturing, maintenance, combat, etc. These entities must robustly accommodate significant run-time uncertainties in their application environment and system resource state, by being dynamically adaptive. In particular, such systems have mission-critical time constraints which must be satisfied acceptably—as specified by the application—given the current application and system circumstances. Thus, they violate the static, deterministic, synchronous premises on which most conventional real-time computing concepts and techniques are founded. We are developing a different and more appropriate paradigm for timeliness in asynchronous (aperiodic), decentralized, real-time mission management computing systems. It is scaleable to encompass a wide spectrum of real-time “hardness” and “softness” in a unified way, and permits the use of best-effort resource management algorithms. The progenitor of this timeliness paradigm was publicly introduced in the Alpha decentralized real-time OS kernel; and its current incarnation is being incorporated into a new real-time version of the Mach 3 kernel.

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