The domain relationship diagram: a mapping framework for digital twin design in complex cyber-physical ecosystems

The ability to reduce risk and uncertainty in the operation and performance of complex adaptive systems is highly desirable across a range of applications and sectors, especially when the correct operation of those systems is critical. Recently, digital twins have delivered this capability for cyber-physical systems by combining modelling with real/relevant-time information flows. Increasingly, however, critical national infrastructure which were previously isolated networks (such as transport and energy networks) are accelerating their levels of integration, forming cyber-physical ecosystems (CPES) and creating new design challenges for digital twins. One fundamental challenge lies in synthesizing information from multiple sources in order to understand the ecosystem as a whole. In this paper, we propose a novel mapping framework to meet this need: the ‘domain relationship diagram’, which balances flexibility and interpretability with sufficient rigour to support model-based design. After establishing the method, we illustrate its usage through two use cases, both motivated by priority research in critical CPES: (i) flooding resilience in northern England and (ii) energy infrastructure at the Port of Dover. We also tie this approach into other crucial topics in digital twins for CPES, including ownership, ontologies and communication, and trust and resilience.