Fractionated Software for Networked Cyber-Physical Systems: Research Directions and Long-Term Vision
An emerging generation of mission-critical systems employs distributed, dynamically reconfigurable open architectures. These systems may include a variety of devices that sense and affect their environment and the configuration of the system itself. We call such systems Networked Cyber-Physical Systems (NCPS). NCPS can provide complex, situation-aware, and often critical services in applications such as distributed sensing and surveillance, crisis response, self-assembling structures or systems, networked satellite and unmanned vehicle missions, or distributed critical infrastructure monitoring and control.
In this paper we lay out research directions centered around a new paradigm for the design of NCPS based on a notion of software fractionation that we are currently exploring which can serve as the basis for a new generation of runtime assurance techniques. The idea of software fractionation is inspired by and complementary to hardware fractionation — the basis for the fractionated satellites of DARPA’s F6 program. Fractionated software has the potential of leading to software that is more robust, leveraging both diversity and redundancy. It raises the level of abstraction at which assurance techniques are applied. We specifically propose research in just-in-time verification and validation techniques, which are agile — adapting to changing situations and requirements, and efficient — focusing on properties of immediate concern in the context of locally reachable states, thus largely avoiding the state space explosion problem. We propose an underlying reflective architecture that maintains models of itself, the environment, and the mission that is key for adaptation, verification, and validation.
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