# Geo-Spatial Context Provision for Digital Twin Generation
## 3 A Digital Twin Architecture Linking CPS Behavior and Produced Operational Data
### Integrating the Introduced Concepts  
The overall proposed approach to the creation of digital (process) twins, whose key concepts and elements were introduced in the previous sub-sections, is presented in Figure 9 in an integrated form. The graphic delineates the different involved elements, from the initial models depicting a number of business-relevant, technology-supported processes, to the created instances and their assigned cyber-physical behavior carriers producing event data. The event data is used to keep instances up-to-date with the state of the real-world processes. Is is furthermore processed and integrated with the originally modeled processes to create different visualizations of the operational environment at different points in time, depending on stakeholder needs. For the realization of the introduced architecture, we furthermore propose a number of development steps, intended to serve as a general guideline. This methodology is based upon the general subject-oriented approach discussed in Section 3.1 and extends it towards incorporating the necessary steps to implement the architecture. It is also used as a framework to point out some of the challenges and considerations related to the required technology and design decisions. The basic assumption is that the system for which the architecture should be implemented is already known and specified to a certain degree. Figure 9: The proposed concept for the creation of digital (process) twins built on ideas from subject-oriented business process management to link behavior with geo-spatial context information. First, it is necessary to determine the set of organizational processes for which the twin could be implemented. Candidates are all processes that are, at least partially, enacted/supported by cyber-physical components. * Next, it will be necessary to determine the overall goal and the envisioned use cases of the digital twin. This involves gathering stakeholder needs and requirements. These are used as input for the following steps and will determine various aspects of the final twin, such as behavior specification granularity and the data that needs to be gathered from the twinned system. Already, some attention should be given to the technical capabilities of components with regard to the provision of data (performance, network capabilities). Based on this information, processes are chosen from the candidate list. * Subsequently, it is required to create the subject-oriented specification of the selected processes. The processes are already put in place and are executed as part of the organizational environment. Thus, if certain process documentations are already present (even if the used notation is not subject-oriented), they can be used as input. An example would be a natural language description, such as the illustration case outline that was used as input for creating the sample model variants in Section 3.2. Similar artefacts, such as documentations of control software and system models, can be used to gain knowledge about the behavior of cyber-physical components. There also exist techniques for the elicitation of stakeholder knowledge with regard to business processes. Due to the heterogeneous nature of CPS, this step will require inputs from many different domain experts to specify the process. This constitutes a major challenge that one needs to be aware of during architecture implementation. Once sufficient knowledge about the processes has been gathered (sufficiency will depend on many factors, such as the required level of process granularity), the modeling can start. Generally, one of the first steps of subject-oriented process modeling is to determine the subjects and the messages that they exchange. This is a question of decomposing a system and finding the appropriate level of abstraction. With regard to CPS, this entails that choices need to be made with regard to representing different components through their relevant behavior. Once subjects have been determined, their individual behavior is detailed in the form of an SBD.