## 4 Results and Discussion
### Impact on Generic Maintenance Program
Two main aspects influenced the emergence of the concept of prescriptive maintenance: (1) having a reliable prediction model for the prescribed scenarios and (2) designing prescribed mechanisms like redundancy. Simulation modeling technology such as agent-based simulation enables prescriptive maintenance by building prediction models for the prescribed scenarios. The most obvious mindset in Table 10 is the \"Design for It\" mindset. Corrective and preventive maintenance concepts do not require physical modification of the assets during the design phase. Adapting condition-based, predictive, and prescriptive maintenance requires physical attachments and cyber infrastructures, which requires considering and \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Aspect** & **Case 1** & **Case 2** & **Case 3** & **Case 4** & **Case 5** & **Case 6** & **Case 7** \\ \hline Installation Type & Midstream & Topside & Topside & Topside & Subsea & Drilling & Wind Farm \\ Equipment Type & Rotating & Rotating & Rotating & Static & Safety & Safety & Rotating & Rotating \\ \hline IoT and Cloud Services & X & X & X & X & X & X & X \\ Machine Learning and AI & X & X & X & X & X & X & X \\ Simulation Modeling & X & X & X & X & X & X & \\ Digital Twins and MBSE 1 & & & & X & X & & \\ VR and AR & & & & & & & X \\ Additive Manufacturing & & & X & & & & X \\ Autonomous Vehicles & & & & X & X & & X \\ Modular Replace Mindset & & & X & & & & X \\ Unmanned Mindset & & & X & X & X & & X \\ “Design for it” Mindset & X & X & X & X & X & X & X \\ CbM 2 & X & X & X & X & X & X & X \\ PdM 3 & X & X & X & & & X & X \\ PsM 4 & & X & X & & & & \\ \hline \hline \end{tabular}  
* Model-based systems engineering, 2 condition-based maintenance, 3 predictive maintenance, 4 prescriptive maintenance.  
\end{table} 
Table 10: The summary of the involved technology(s), mindset(s), and maintenance concept(s). designing them by specialized engineering analysis that determines the required technical specifications. Other mindsets that appear in some case studies are unmanned and modular replacements. The unmanned mindset is driven by the value to be gained from maintaining assets remotely and through longer maintenance intervals. This value is related not only to maintenance expenses but also to the safety and environmental impact associated with maintenance campaigns. The modular replacement mindset gains the value of reducing offshore or on-site maintenance time by replacing the entire module and repairing it later in the workshop without affecting the production time. With respect to asset type, it is clear that asset type and its consequence or value class have significantly influenced the selection of the cost-effective maintenance concept. In addition, asset configuration at the system level also influences the ability to offer prescriptive maintenance. Even though most of the emerging practices observed in the case studies are related to the Industry 4.0 transformation, there are some emerging practices driven by the green transition. There are several emerging practices, partially driven by green transition: (1) equipment electrification which has created a new challenge and emerging practices to engineer and manage its maintenance plan and program, (2) the unmanned and long-term maintenance intervals were not only driven by cost saving but also emission cut-down for maintenance vessels, and (3) spare parts inventory and supply where new concepts have emerged like shared spare parts, digital warehousing, and on-demand manufacturing (mainly depending on additive manufacturing) to enable local manufacturing and supply and cut down emissions due to long-distance supply. In addition, emerging sustainability reporting and emission credit initiatives have reinforced the environmental consequence in the risk matrix, which is used to classify equipment, spare parts, and prioritize corrective and preventive maintenance work orders.