# Generic Digital Twin Architecture for Industrial Energy Systems
## 3 Proposed Generic Digital Twin Architecture  
In this section, we present our proposed GDTA which targets the applications of DTs during the operational phase of an asset. The architectural model of the GDTA is depicted in Figure 2. The architecture is aligned with the IT layers of RAMI 4.0 to structure the specified components. The hierarchy levels of RAMI 4.0 are not taken into account because a DT can be located at various levels, depending on its application or the physical entity for which it is designed for. Thus, a DT can potentially cover all hierarchy levels of RAMI 4.0. As mentioned before, our DT architecture targets the \"instance-phase\" of the RAMI \begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Name** & **Target Domain** & **Structure** & **Main Parts** & **Level of** \\  & & & & **Abstraction** \\ \hline
3D-DT [8] & Life-cycle & component-based & 3 components & high \\  & Management & component-based & 5 components & high \\
5D-DT [13] & Manufacturing & component-based & 5 components & high \\
5C Architecture [11] & CPS in manufacturing & layer-based & 5 layers & high \\ Intelligent DT [14] & Production Systems & component-based & 4 interfaces \& 9 components & low \\ Ref. Framework for DT [6] & CPS in general & component-based & 4 main components & low \\ COGNITWIN [15] & Process Industry & components \& layers & 5 layers \& 19 components & low \\ Conceptual DT Model [16] & CPS in general & layer-based & 6 layers & medium \\ ASS [17] & Manufacturing & only meta-model & ongoing work & — \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of concepts, architectures, and frameworks for Digital Twins (DT). 4.0 life-cycle. Thus, only the IT layer dimension of RAMI 4.0 is shown in Figure 2 and the architecture is structured based on this dimension. The GDTA is based on the introduced 5D-DT concept and inspired by the 5C architecture for CPSs, because both concepts have a sufficient level of abstraction, which means they provide a more conceptual view than a concrete architecture. However, they are still useful to identify key components and functionality for DT. The proposed GDTA defines the basic structure and components of a DT without specifying or binding it to certain technologies. For realizing a DT based on the GDTA, various existing technologies and frameworks can be used to implement its functionality on different layers. The specified components of the DT are explained in more detail regarding their associated RAMI 4.0 layer in the following paragraph. Asset Layer--The physical representation of the DT is located at the Asset Layer and corresponds to the Physical Entity of the 5D-DT concept. It holds the physical parts of the CPS. Integration Layer--At the integration layer, Run-time Data as well as Engineering Data can be distinguished. Run-time Data are generated by sensors or events and represent the current state of  
Figure 2: Generic Digital Twin Architecture (GDTA) model. the physical entity. They are usually time-series data. These data are very dynamic, so the underlying infrastructure has to follow application-specific requirements, like big data processing or real-time reaction. Archives, e.g., special time-series databases, can be used to store these data for diagnosis and model identification purposes. Engineering Data are usually static data, which means they will not often change over time. Examples are the plant topology or information about a physical component inside a plant. This information is mostly available in analog formats, like drawings of pipe and instrumentation diagrams, and has to be digitized. Even if the information is already available in machine-readable form, the information has to be transformed and integrated into the DT as contextual information. Communication Layer--Industrial communication or Industrial Internet of Things (IIoT) protocols can be applied within the Communication Layer of the DT. The concrete protocol depends on the requirements of the application, e.g., real-time capabilities or publication/subscription support.