Definitions

The cyber-physical microservice is defined as the key construct for the modeling of cyber-physical systems.

A cyber-physical microservice (CPMS) implements its functionality by a close integration of physical and cyber artefacts. It offers a specific and narrowly defined physical functionality, such as heat and mix, enriched by cyber artifacts and is deployed on the plant platform as an independent service but within the context defined by the constraints imposed by its mechanical part. We discriminate microservices into primitive and composite microservices.

Primitive cyber-physical microservice (p-CPMS) is the microservice that encapsulates a physical artefact by adding intelligence on it and transforming it to a smart entity that is able to either process, or transport, or store energy, material, parts, sub-products and products. Typical examples of p-CPMSs are the smart silo and smart pipe of the Liqueur Plant case study and the three Robot arms and the two workbenches of the Gregor chair case study. Primitive CPMSs operate on physical objects, e.g., assembly parts, and transform their state. A p-CPMS ) has its own dedicated mechanical part, that is completely under its control.

Composite cyber-physical microservice (c-CPMS) is the microservice that offers its functionality by utilizing (directly or indirectly) the functionality of at least one p-CPMS. Composite CPMSs implement functionality for either processing, and/or transporting, and/or storing material, parts, sub-products and products. The operation of composite cyber-physical MSs depends on the availability of the utilized primitive cyber-physical MSs with which it is coupled in time, that is another differentiation from software microservices. Typical example of c-CPMSs are plant processes as for example the liqueur generation processes of the Liqueur Plant case study.