Formalise and verify SoS-level Digital Twin composition

Fully formalise and verify the composition of multiple Digital Twins at the Systems-of-Systems level, including the SoS-level coordination layer of the DT-enabled greenhouse architecture.

Background

The paper develops and verifies formal VDM-RT models for individual artefacts in a greenhouse System-of-Systems: the Pot Model, the Decision Service Model, and the shared Environment Digital Shadow. The architecture also includes a composed SoS-level coordination Digital Twin that aggregates water usage and enforces global resource constraints across multiple plant pots, but this coordination layer is not formalised or verified in the study.

The unresolved problem is to extend the individual-artefact quality framework to compositional verification. This requires addressing interactions among Digital Twins, including fidelity-error amplification, scope-dependent relevance, architectural compatibility and substitutability, shared-resource allocation, synchronisation overhead, scalability, and the derivation of SoS-level guarantees from constituent-level guarantees.