# Industry 4.0 Roadmap: Implementation for Small and Medium-sized Enterprises
## 2 Methodology
### Literature Review
#### 2.1.2 Industry 4.0 Technologies  
The analysis of different Industry 4.0 technologies was carried out by reviewing some European guidelines; for instance, those proposed by the Mechanical Engineering Industry Association (VDMA) and the compilation of practical examples created by this association since 2019 [24; 25]. Additionally, benchmarking was performed through Internet research to obtain a preliminary view of the top Industry 4.0 performers. Best practices have been identified in companies such as Volkswagen, Amazon, Siemens, etc. [26; 27; 28; 29]. There is extensive literature about technologies related to Industry 4.0 [7; 9; 16; 24; 30]. Industry 4.0 can be implemented in every industrial sector, from shipbuilding to aerospace and medical devices. Transformation to Industry 4.0, however, means different things for each company in these sectors, and requires different approaches to be achieved. At the same time, every company needs to understand the different components and tools offered in order to determine the correct business strategy [31]. Considering the large number of technologies related to Industry 4.0, the authors have selected four of these technologies to perform a deep dive into the literature review: Cloud Computing, the IoT, Digital Transformation (DT) and VR. Some authors consider the IoT and Cloud Computing to be the key technologies of Industry 4.0 [16]; others cannot imagine a transition to the Fourth Industrial Revolution without considering several Industry 4.0 pillars at the same time [32]. Several authors highlight the advantages that Cloud Computing offers; for instance, it saves costs and delegates liabilities to third-party providers [33]. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Enterprise Category** & **Employees** & **Turnover** \\ \hline Micro SME & 0 to \textless{}10 & \textless{}€2 million \\ Small SME & 10 to \textless{}50 & \textless{}€10 million \\ Medium-sized SME & 50 to \textless{}250 & \textless{}€50 million \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Commission recommendation concerning the definition of SMEs. Moreover, the development of the IoT is a crucial moment in the history of humanity because it is changing our mindset, culture and the way we live or manufacture. As with the Internet age, there will be a pre-IoT world and a post-IoT world. The IoT era will not be an instantaneous transition, but a gradual and continuous shift during which evolution will never stop [34]. Sensor technologies, which are a key element of the IoT, have experienced rapid development in recent times and still face some challenges, such as proper standardization [35]. This development has been driven by the advent of high-speed and low-cost electronic circuits, a change in the way we approach signal processing and corresponding advances in manufacturing technologies [36]. Additionally, there are some research works and conference proceedings that have stated the belief that VR will greatly support the accessibility of smart manufacturing [37; 38; 39]. Based on the abovementioned literature review, the authors came to the following conclusions:  
* The IoT has experienced a tremendous cost reduction in the past few years, and the offered technologies have multiplied. * DT is very generic and includes too many technologies and components; thus, it is not suitable for further analysis in this paper. * Cloud Computing is now a well-established technology that is offered at a low price. * VR is a very flexible technology that can be implemented in several areas of production. Figure 1 shows the interconnection between the different components of these four technologies, with some branches (inner circle) replicated in some stems/leaves (outer circle). This is a positive aspect because the implementation of one technology will provide access to other technologies. The outlook for the coming years, according to data extracted from the European Patent Office [40] in Figure 2, shows that changes are still ongoing.