## 3 Development of the Generic Implementation Strategy
### Methodological Fundaments of the Development
#### 3.1.1 Structure and Rationale of the Approach
The central statement is that \"to [their] knowledge, this aspect, which is crucial for a successful DT development, has never been identified and described by any state-of-the-art work\" [17]. Due to the high system complexity of DTs, a socio-technical approach is essential for its realization. The inclusion of all relevant stakeholders of a DT, from experts to designers and decision-makers, is indispensable already during the development of the DT idea. This involvement must be continuous, collaborative and as early as possible in the design process. Along the life cycle, the process can adapt to changing requirements in advance, or to integrate aspects that are not yet known at the initial design of the DT at a later point in time. The socio-technical and collaborative approach can thus meet the diverse and complex requirements in the realization of DT projects. In this regard, [PERSON] et al. underline: \"The need to find new strategies to support such collaboration therefore becomes an open challenge\" [17]. It can be concluded from this that there a current lack of GIS to realize this. From this qualitative comparison of the research papers, it could be concluded that all papers use plan-driven processes of forward engineering to describe or implement a DT (see Figure 4). All works show similarities and parallels to the SE approach. Within the functional requirements for the GIS, the works are characterized by a strong focus on the technical design and development of a DT. Hereby, only one work on the application area of logistics and a few works on the recording, analysis and inclusion of the implementation environment and the stakeholders. This leads to the assumption that the existing papers have a rather specific character, which consider the implementation of a DT as an isolated technical process, as they do not include the socio-technical implementation environment. The non-use of socio-technical design can lead to the result of the implementation not serving the needs of the stakeholders and ultimately the users of the DT. For this reason, the usage is recommended, as it involves stakeholders along the development process in a collaborative and iterative way. This implementation aspect is also mentioned in the work by [PERSON] (2018) as well as IEEE (2015). Likewise, the papers show gaps in a possible procedural alignment of the approach within the (non) functional requirements as well as the presence of an iterative and generic approach. Regarding the overall agreement of the categories of the category system, it can also be seen that a large proportion of the papers only have an agreement of 40 to 50 percentage points. The minimum is 35 percentage points and the maximum 53 percentage points. The weightings within the categories should also be seen as a reference and a benchmark for the development of the GIS. In summary, it can be emphasized that no approach for a DT GIS was identified, that specializes in logistics application or the German rail transport. This research need further justifies the relevance of this work. To guarantee an accurate GIS development in Step 3 of Figure 3, the functional and non-functional categories of Figure 4 were evaluated in greater depth since they form the requirements for the successful GIS development. For this purpose, the following characteristics are considered: _adequacy, completeness, consistency, comprehensibility, uniqueness_ and _testability_[55]. The defined requirements from Figure 4 are based on a comprehensive analysis of existing research on the implementation of a DT, and thus, completeness and adequacy can be concluded. Consistency is fulfilled by the clear separation into non-functional and functional as well as the individual description of all requirements. By embedding the theoretical foundations, and therefore creating necessary foundations for understanding, comprehensibility is fulfilled as well. The partly detailed description of the requirements and the theoretical foundations ensure that the requirements are unambiguous.