# A Resilience Engineering Approach for the Risk Assessment of IT Services
## 2 Materials and Methods
### Research Approach  
The migration of an IT system is considered a high-risk process because only when the process is almost completed is it possible to understand the relationships between the data managed and the related trade-off between the cost, effort, risk, and time on the one hand and the value creation on the other [43]. More in detail, in cloud computing, six main types of migration strategies are recognized [44], which are named the \"6 Rs\" and can be schematized as follows:  
1. Re-hosting (lift-and-shift)
2. Re-platforming (lift-tinker-and-shift)
3. Re-purchasing (move to a different product)
4. Refactoring
5. Retiring
6. Retaining. These strategies provide different levels of optimization, requiring, at the same time, different efforts in terms of implementation costs and resources. Accordingly, the analysis of the supply chain related to the migration process and the supplier selection process are key elements for a successful migration. More specifically, the system supply chain in the case of cloud migration is composed of the following activities, which can be carried out by internal or external actors (i.e., the organization's technicians or the suppliers, namely):  
1. Connectivity and webserver of the Hosting service (external);
2. Hosting service configuration (internal);
3. Provision of applications for the management of the Hosting service (external);
4. Configuration of the Hosting platform (internal);
5. Domain name transfer/registration (external);
6. Domain name transfer/registration (internal); \begin{table}
\begin{tabular}{c c c c} \hline
**Fu** & **Precise** & **Acceptable** & **Imprecise** \\ \hline T & Improbable & Normal & Improbable \\ M & Possible & Possible & Possible \\ O & Improbable & Probable & Possible \\ \hline \end{tabular}
\end{table} 
Table 2: Criteria suggested for the evaluation of the variability in the FRAM method. Domain Name System (DNS) service (external);
* Domain Name System (DNS) configuration (internal);
* Provision of applications for the system migration (external);
* Management of customers and access to data (internal). As can be seen in the above list, half of the activities are provided by external actors; this shows the criticality of both the suppliers' selection and the management of the whole migration process. Another critical issue in the supplier selection process relies on the satisfaction of customer needs and expectations [45; 46]. To deal with this, the CTQ technique can be used to gain information about customer needs and preferences. Such a tool requires a survey among customers to determine their point of view on the quality of both the products and the related services, including customer care services [47]. A general scheme of this method is illustrated in Figure 2, where QDs represent the quality drivers and PRs represent the performance requirements. The output of this analysis allows the definition of the key requirements for customers, viz., the system's critical-to-quality features [48]. Based on the above considerations, the FRAM approach was used to analyze the risks related to the migration process of an IT platform, which includes the transfer of data and software and is usually articulated into three main phases: plan, execution, and validation. The use of FRAM was integrated with the application of two different tools aimed at improving its effectiveness:  
* The 6 Rs approach to defining the proper strategies for IT system migration: in order to decide the proper strategy, the decision tree model proposed by Lloyd [43] was used. * The Critical-to-Quality (CTQ) technique was used by means of a survey among the IT platform customers. In addition, it must be noted that technical standards, such as ISO 22316 [49] and ISO 28000 [50], were used both in the planning phase (to verify the system requirements and the suppliers' features) and in the validation phase (to verify the conformity of the new system). Overall, the scheme of the proposed approach is illustrated in Figure 3, where the main activities are summarized.