## 3 Development of the Generic Implementation Strategy
### Generic Implementation Strategy in the Narrower Sense
#### 3.2.1 Phase 1: Design Phase
Aspects of safety, health, insurance, or the environment may be relevant here. To enable a later verification of the defined requirements, the requirements are checked for their meaningfulness and specific evaluation criteria are defined. They serve the subsequent validation of the DT. Based on the defined requirements, systems or services are derived that are necessary for the further implementation process (see Figure 12). Building on the previous process steps, the third process aims at defining the concrete requirements for the DT. For this purpose, the requirements defined by the stakeholders and user-centered approach are translated into technical specifications. This procedure is performed with the help of the operational concept and context of use defined in the previous step. Relevant requirements can be interfaces, data, data quality, system boundaries and components [17; 28; 49; 50; 54]. In addition to the requirements, constraints that could influence or hinder the implementation must also be recorded [17]. To enable a verification of the implemented DT solution at a later point, the requirements are also checked for their plausibility and corresponding evaluation criteria are introduced in this step. After the fields of action have been carried out and final DT requirements have been defined, an iteration with the identified stakeholders takes place to validate the requirements and subsequently select necessary systems and services (see Figure 12). To meet the requirements, the DT architecture must be designed in the following process. Hereby, it may be necessary to develop different levels of detail regarding the architecture for different stakeholders [15]. To prepare the architecture design, the first step is to identify the critical drivers of the architecture, as they have a significant influence on the architecture itself [54]. This identification can be performed based on internal and external research and analysis. In addition, it is necessary to capture other constraints on the architecture. These constraints can be identified through stakeholders. Before the final architecture is defined, different architecture variants are designed and evaluated against each other. For this purpose, evaluation criteria are first defined and necessary systems and services for the design are determined. This process is followed by a design of different views of the architecture, which are used to identify possible architecture frameworks and models. These are rationalized and tailored to the context in which the necessary system context is defined in terms of interfaces and interactions of the DT with its environment [49]. The defined architecture units are adapted and tailored to the identified possible architectures. A connection of the architecture with possible DT designs follows [54]. For this, the final interfaces, and interactions of the DT with its environment are defined and the DT elements are connected to the architecture units to identify design characteristics. These characteristics are addressed in the fifth process. After the possible DT architectures have been designed, they are evaluated against the defined evaluation criteria to identify the architecture that best meets the requirements already defined. Once the best possible DT architecture is identified, the final views, models and descriptions of the architecture are defined. The core components and decisions of this process are recorded for management of this definition. Based on this, the explicit agreement of the stakeholders with the architecture is obtained to enable a later valid and verified implementation (see Figure 12). In the following, the DT and its elements are further specified, in line with the architectural units defined in the previous process. To enable a successful implementation, design characteristics and enablers of the individual DT elements are identified and defined what includes the identification of necessary DT technologies and supporting services or systems.