## 2 Theoretical Fundamentals and State of the Art
This risk is further increased by principles such as Bring Your Own Device (BYOD) or Choose Your Own Device (CYOD), which exposes networks to a higher risk of infiltration, e.g., due to a lower level of standardization by a higher degree om heterogeneity of used devices [82]. Therefore, data should be classified according to their confidentiality, integrity and availability (CIA) to prevent unauthorized access and data manipulation [83; 84; 85; 60; 81]. Manipulation or corruption of data could lead to malfunctions, miscalculations, misinterpretation and thus to wrong decisions in the upper two layers of the automation pyramid, the Manufacturing Execution System (MES), and the superordinate Enterprise Resource Planning (ERP) system. As stated by [81], another security risk is the age of the infrastructure, as there is a frequent replacement of equipment over time, making constant planning and updating of security measures necessary. Therefore, a multi-layer architecture approach with multiple safety layers should be implemented, dividing and analyzing the signal flow of each CPPS and cross-validating the signals with those of corresponding CPPS [81]. Other security measures as stated by [81], such as Side-Channel Analysis [86; 87] or Post-Production Analysis, can further enhance operational security despite the challenges they pose. A further approach, as mentioned by [88], would be a standardized certification into embedded systems themselves letting those systems check for their security by themselves. Furthermore, [89] proposes that RAMI 4.0 should take greater account of safety and human factors. Another weakness in security planning was pointed out by [90], as stated that a lack of recovery planning in the case of disaster is persistent in I 4.0. Other security measures, as noted by [88; 91], include the implementation of a firewall and a private network (VPN) that can only be accessed by devices with authorized IP addresses. Table 1 summarizes the most important key factors for the implementation of a digitalized metal processing value chain. Based on the theory elaborated, the authors propose the following hypothesis:  
**Hypothesis 1 (H1). **_When developing a digitalized supply chain within the metal processing environment which is horizontally interconnectable, the 5V condition and therefore the existence of Big Data is automatically fulfilled._Digitalization and Development of a Metal Processing Value Chain: Framework and Corresponding Case Study for SMEs  
The presence of SMEs in a value chain varies among the considered industry segment and country. In the case of Austria, 99.7% of the industry consist of SMEs [99], whereas 18.1% of Austria's industry concern the field of manufacturing [100]. Consequently, it is most likely that SMEs are involved within a metal processing value chain. This is particularly evident in the manufacturing sector of the automotive and aerospace industry, where many specialized SMEs supply big enterprises with components that have to fulfill high quality standards and require specific production related expertise [101; 102; 103; 104]. To be able to support SMEs within this environment, this section describes the further concretization of the RAMI 4.0 framework for the development of a simplified digitalized value chain for the metal processing industry, that especially considers the additional restrictions SMEs face. The resulting concretized framework is put into operation by a smaller-scale use case at the Montanuniversitat Leoben. This use case, which is part of the MUL 4.0 project, does not only serves as a practical testing of the stated hypothesis but pursues to contribute to as a fundament for the state-of-the-art engineering education for future experts in the manufacturing field [105; 106]. According to [105], the two main cooperating instances of MUL 4.0 can be characterized as follows: the Chair of Metal Forming (MF) with 15 employees represents a small enterprise, whereas the Chair of Non-Ferrous Metallurgy (NFM) with 72 employees can be seen as a medium enterprise.