Cyber-Physical Systems (CPSs) are large-scale complex systems that monitor and control physical processes by using computer algorithms tightly integrated with networking and their users. Monitoring and controlling the physical environment is a hot topic for today's researchers and engineers in academia and industry. Within this realm, an important feature of current and future Information and Communications Technology (ICT) systems is self-adaptation-yet there is a shortage of information

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... ng on this characteristic in the literature, particularly as it relates to CPSs. Here, we investigate current state-of-the-art research on CPSs from this perspective, and evaluate the main self-adaptive approaches proposed in the literature, along with their results, strengths, and weaknesses. We also discuss appropriate techniques for enabling self-adaptation capabilities within CPSs at different architectural layers. Overcoming the challenges associated with designing and implementing self-adaptive mechanisms in CPSs will provide a path for bolstering a new generation of CPSs with greater robustness and reliability. INDEX TERMS Adaptive systems, cyber-physical systems, self-adaptation. 171126 This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see http://creativecommons.org/licenses/by/4.0/ VOLUME 7, 2019