## 2 Research Background  
### Understanding of the Generic Implementation Strategy  
With reference to the research area of implementation derived in Section 1, it can be stated that an implementation can be holistically differentiated into functional and institutional anchoring. Institutional anchoring comprises the totality of all persons involved in the implementation, whereas functional anchoring describes the activities necessary for it [19]. The focus of this work is a functional design of the GIS.  
The term _strategy_ is in the entrepreneurial manner understood as a long-term behavior and combination of measures for the realization of long-term goals [20]. The term _implementation_ focusses on \"the process of translating a design into hardware components, software components, or both [and] the result of that process\" [21]. It transforms the defined requirements, architecture, design and interfaces of the design phase through process activities and is carried out according to a defined implementation strategy, which contains constraints as well as defined procedures [21; 22]. In a broader sense the activities of implementation are supplemented with testing and acceptance as well as maintenance and operation [23]. The term _implementation strategy_ is an amalgamation of strategy and implementation. It is the purposeful behavior and combination of measures of the enterprise towards its environment, for the realization of an implementation of systems. In the context of IT systems, it includes the process of implementation and production, tools, and equipment as well as tolerances of implementation and uncertainties of verification. The processes are defined more precisely if the system under consideration is to be implemented several times and repeatedly. This serves to ensure consistent and uniform production and implementation [22].  
There are different procedural models of an implementation strategy. A distinction is made between forward- and reengineering, whereby _reengineering_ refers to implementation strategies that serve to transform a legacy system into a new target environment, i.e., a reuse of an existing system [24; 25]. Within _forward engineering_, a system is either functionally further developed on the basis of a system specification, newly created or acquired [22]. To implement this, there are various models, so-called process paradigms, which represent the structure of necessary processes, whereby a distinction is made between plan-driven and agile processes [25]. _Plan-driven_ implementation strategies represent procedures in which all development process activities are planned. In _agile_ implementation strategies the development process does not follow a strict plan made in advance. However, there is no universal process model. This is because the requirements of stakeholders and the environment in which the system is to be used have a significant influence on the process [25]. Regarding the understanding of the term GIS, _generic_ means that the property or designation of an object or concept is to be understood in a generally valid sense and not specific [26]. In the context of DTs, this generality is of particular importance (see Sections 5.1 and 5.2) to avoid isolated systems and secure the interoperable and standardized communication of multiple DTs [15; 23; 27]. Industry and business have also recognized this need and are therefore dedicated to the standardization of DTs with multi-layered consortia such as the _Industrial Digital Twin Association_ or the _Digital Twin Consortium_. In the context of this work, a GIS of DTs is, therefore, defined as the targeted behavior and combination of measures that serves the generally valid implementation of the DT concept.