## 6 Conclusions  
### Summary of the Results  
In the context of the logistical management of the sparing use of resources and the increased transport and traffic volume, the need for coupling real and virtual worlds has increased in recent years, as this interaction promises new business innovations and the optimization potential. In addition to the virtualization of realities, rail transport is becoming increasingly important as it enables resource-saving transport and traffic. To successfully meet the challenges described regarding German rail transport, the federallyowned railway group DB has adopted the group strategy _strong rail_. For this strategy, digitalization and technology have become the decisive key, which justifies the relevance of DB's digital and technology strategy. In the context of science and practice, the potential of the DT concept was recognized, which should help to solve operational challenges. As this is a new concept, there are many challenges, such as the way in which DT is implemented, which need to be solved to realize its full potential. Therefore, the goal and research question of this work was to develop a strategy that would serve as a reference for the future implementation of DTs. The systematics of this work was based on the DSRM research methodology shown in Figure 3, which serves the successful development of representation models in information systems. As a result of the work, the following aspects can be summarized, which furthermore fathom the answer to the research question:  
* _GIS_: target-oriented behavior and combination of measures for the generally valid implementation of DTs; focus on forward engineering as well as plan-controlled process steps. * _DT understanding_: the virtual system platform is a physically correct digital representation with very high fidelity of the physical system platform; the overarching goal is the concrete provision of services in the DT environment which serve the operational optimization of the asset under consideration along its life cycle. * _Theoretical foundations_: use of the SE approach and its life cycle processes according to IEEE Standard 2015:15288; integration of a socio-technical systems focus. * _Validation of the GIS_: conducting qualitative expert interviews in a single-case study design on the application of the GIS; reviewing the specially developed GIS requirements and evolution based on the findings
* _Model approach_: inclusion of four life cycle phases within the GIS; in the narrower sense the inclusion of design and development and in the broader sense the operation and decommissioning; focus on assets that already exist and the DT and its environment in the context of the socio-technical system focus. * _Components_: 15 dedicated technical process steps in the process model; nine in the narrower and six in the broader sense of GIS; plan-driven relationships and coupling of real and virtual (environment) world. The results obtained demonstrate the validity of the assumptions made as well as the practical applicability of the developed GIS. Furthermore, this work has provided important and novel insights as well as practical implications for the promising use of DTs (e.g., see Figures 6 and 7 and Table 2). In this context, for the practical success of DTs, it is particularly important to emphasize that the DT must solve a specific use case for which it represents the operationally optimal solution. The definition of data requirements must be application-oriented and pragmatic, as data are a key challenge in the implementation of DTs. For example, indiscriminately collecting data in real time to optimize operations and maintenance was identified to be not goal-oriented or operationally optimal (see Table 2). Furthermore, it can be generally stated that the interoperable exchange of different DTs requires a cross-company approach to develop and establish standardized or self-learning interfaces as well as open organizational structures.