A system model is developed where the criterion to partition the world into a system and a rest is based on the functional relation between its states. This approach implies that the gestalt of systems becomes very dynamic. Especially interactions between systems may create temporary super systems "on the fly". The reference to the function notion establishes the link to computation. Based on the distinction between the intended determinism versus nondeterminism of the interaction, two classes of system interactions are distinguished: composition and cooperation. Composition means that by interaction super systems are created and the interacting systems become subsystems. Cooperation means that systems sensibly interact loosely without creating any identifiable super system function and therefore without super system creation from the perspective of the interacting systems. Cooperative system interactions are described with the help of the protocol notion based on shared states, interpreted as the stateful exchange of characters via Shannon channels between roles - the projection of systems onto the interaction channels. It is shown that roles can be internally coordinated by a set of rules, leading to a very flexible process notion which unfolds its full potential only in a new type of execution environment capable of executing spontaneous transitions. The system model has immediate implications for componentization which can be viewed as an attempt to either hide functional recursion and provide only functionality whose composition behavior is easy to understand, or to provide loosely coupled interactions via protocols. To be complete, component models should therefore at least support three general classes of components: one for loose coupling, one for hierarchical composition, and one for pipes.
In his excellent book ''Principles of Cyber-Physical Systems'' @cite_33 Rajeev Alur distinguishes between functional and reactive components in the tradition of David Harel and Amir Pnueli.
@cite_33
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A cyber-physical system consists of a collection of computing devices communicating with one another and interacting with the physical world via sensors and actuators in a feedback loop. Increasingly, such systems are everywhere, from smart buildings to medical devices to automobiles. This textbook offers a rigorous and comprehensive introduction to the principles of design, specification, modeling, and analysis of cyber-physical systems. The book draws on a diverse set of subdisciplines, including model-based design, concurrency theory, distributed algorithms, formal methods of specification and verification, control theory, real-time systems, and hybrid systems, explaining the core ideas from each that are relevant to system design and analysis.The book explains how formal models provide mathematical abstractions to manage the complexity of a system design. It covers both synchronous and asynchronous models for concurrent computation, continuous-time models for dynamical systems, and hybrid systems for integrating discrete and continuous evolution. The role of correctness requirements in the design of reliable systems is illustrated with a range of specification formalisms and the associated techniques for formal verification. The topics include safety and liveness requirements, temporal logic, model checking, deductive verification, stability analysis of linear systems, and real-time scheduling algorithms. Principles of modeling, specification, and analysis are illustrated by constructing solutions to representative design problems from distributed algorithms, network protocols, control design, and robotics.This book provides the rapidly expanding field of cyber-physical systems with a long-needed foundational text by an established authority. It is suitable for classroom use or as a reference for professionals. In this paper, we design a secure, robust and resilient cyber-physical wind energy system (WES) from a cross-layer perspective. We establish a system-of-systems framework for the large-scale wind farm which includes the cyber and physical components. For the cyber layer, we use a game-theoretic model to capture the strategic behaviors of the network defender and the cyber attacker, and compute its mixed strategy Nash equilibria. For the physical layer, we design a robust and resilient switching controller using a Markov jump linear system model. Due to the interdependence between the cyber and physical systems, their performances are coupled and need to be designed in a holistic manner. To address this challenge, we propose an iterative algorithm to study the system-of-systems performance under the equilibrium design which jointly takes the cyber and physical layers into account. Case studies are provided to illustrate the interdependent design principles of cyber-physical WES. Cyber-physical systems are networked, component-based, real-time systems that control and monitor the physical world. We need software architectures that limit fault-propagation across unreliable components. This paper introduces our simplex reference model which is distinguished by: a plant being controlled in an external context, a machine performing the control, a domain model that estimates the plant state, and the safety requirements that must be met. The simplex reference model assists with constructing CPS architectures which limit fault-propagation. We present a representative case study to highlight the ideas behind the model and our particular decomposition. Technology, science, and engineering continue to redefine physical world capabilities. Take mobility of humans, for example. In the 20th century, transportation systems moved us to unimaginable distances, speeds on earth and made us set foot on the Moon. Star Trek popularized teleportation, a fictitious technology that instantly allows us to "go where no person has gone before." Before end of the century, Internet and wireless networking helped to create the parallel "cyber world," virtually "teleporting" us great distances to interact with remote objects, people, and places. In the new millennium, our restless society's need for such ground-breaking capabilities in time and space has never been greater. Cyber-physical system (CPS) is a promising new class of systems that deeply embed cyber capabilities in the physical world, either on humans, infrastructure or platforms, to transform interactions with the physical world. Advances in the cyber world such as communications, networking, sensing, computing, storage, and control, as well as in the physical world such as materials, hardware, and renewable "green" fuels, are all rapidly converging to realize this class of highly collaborative computational systems that are reliant on sensors and actuators to monitor and effect change.Tomorrow's CPS is expected to enrich cyber-physical interactions by intimately coupling assets and dynamics of the physical and engineered systems with the computing and communications of cyber systems, at grand scales and depths from nanosystems to geographically dispersed systems-of-systems. It must be able to adapt rapidly to anomalies in the environment and embrace the evolution of technologies while still providing critical assertions of performance and other constraints.