layers. Moreover, because of inherent interdependence, the layers must communicate a lot. To handle these challenges CERBERO approach leverages on two main pillars:• a model-centric approach to the scenario and system definition, where all the functional, physical, and network components as well as the environment are kept into consideration along with the properties that have to be addressed. • a multi-layer runtime adaptation strategy for CPS, embodied within a high-level self-adaptation engine capable of reacting to external stimulus and autonomously adapting to the evolution of the scenario or constraints. These two pillars, presented in Sect. II-A and Sect. II-B, respectively, contribute to determine the CERBERO continuous design and operational framework for highly interconnected systems presented in Sect. II-C.
A. Model-Centric ApproachComputational, physical and communication layers within CERBERO are going to be cross-optimized, taking into consideration that they are intrinsically concurrent, among each other and internally. To answer the current lack of a comprehensive modeling strategy for heterogeneous CPS, CER-BERO intends to implement a component-oriented approach, with dedicated model-to-model mapping and synchronization interfaces with feedback loops. This strategy is meant to concurrently handle time-continuum and event-driven models that need to coexist, since they are representative of both the physical and the computing aspects of the system, while asynchronous, partially-ordered discrete actions or clock-driven time slots describe the communication layer. In order to reconcile these divergent models, and ensure interoperability and communication between components, we plan to incorporate the following elements in the CERBERO framework: 1) Functional and non-functional requirements management:Generic requirements (e.g., security, energy, dependability) and highly application-specific ones (e.g., the availability of charging points on EV network) are handled. By studying and defining adequate description languages and by providing a generic library of reusable Key Performance Indicators (KPIs) models, we intend to tackle adaptivity in different scenarios and models re-use in consecutive design and operational cycles. Such KPIs also offer an objective and quantitative analysis of the system.
2) Entity/components cross-optimization and validation:Dataflow Models of Computation (MoCs) provide precise semantics to express and, consequently, exploit the intrinsic computing problem parallelism. As demonstrated in literature [8], they are extremely suitable to model both hardware (HW) and software (SW) components at a high level of abstraction, and to perform trade-off analysis and components cross-optimization. On the other hand, state based stochastic algebraic and differential inequalities are suited to represent a large class of dynamic systems. The combination of these models is meant to input effective design space exploration (DSE) and multi-objective