## 6 Conclusions  
Modern systems must simultaneously guarantee security and safety to provide continuous and accurate execution of crucial roles and services. Since security and safety depend on each other, they must be collectively applied to acquire the root cause assessment of noticeable issues. Therefore, numerous methods are developed to integrate security and safety; however, BN and GT are considered in this SLR, due to their extensive usage in various applications. This SLR includes 64 studies, and given below are concluding points:  
1. It is observed that from the 64 included studies, 51 used BN models, 10 utilized GT models, and the remaining 3 were based on united BN and GT. 2. Most development scenarios utilized 40 nodes for performing experiments to observe unintentional failures or risks for GT and BN models. 3. It has been emphasized that approximately one-third of BN and GT models were evaluated in real-time; however, others were either based on simulation analysis or theoretical concepts. 4. There were two types of data sources (EK and ED) used for developing BN and GT models for different applications. 5. The key performance validation mechanisms for the included studies were statistical analysis, expert evaluation, and sensitivity analysis. The future research directions for safety and security integration were the following:  
1. There is a need to develop a generic tool or method or standard to combine security and safety, which can be helpful for different applications, since the significance of integrating both measures was demonstrated in this SLR, and a generic approach may offer feasibility and flexibility. 2. It is observed that there are various validation methods for evaluating BN or GT. A more extended investigation is necessary to estimate the accuracy and efficiency of validation mechanisms, in order to find the optimal option. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Study** & **Pros** & **Cons** \\ \hline [PERSON] et al. [101] & To efficiently recognize and respond to risks in maritime piracy. & There is a need for an ontology for proper usability. \\ \hline [PERSON] [102] & Correctly demonstrate the network safety situation and improve the safety of the system. & Heavily integrated with its system; therefore, difficult to use outside of network security analysis. \\ \hline [PERSON] et al. [103] & Efficiency in analyzing vulnerabilities in smart grid. & The developed model is more methodological than practical. \\ \hline [PERSON] et al. [104] & The developed BN model plays a significant role in reducing fire risks. & The testing is not entirely performed before winter games. \\ \hline [PERSON] et al. [105] & Providing a better quality of life and more prolonged survival of patients. & The threat actors are not specified. \\ \hline \hline \end{tabular}
\end{table} 
Table 6: _Cont._* Moreover, there is a need to research to acquire information about the suitable number of nodes to ensure reliable and accurate performance for ensuring safety and security based on BN or GT models. * Further research could improve Bayesian analysis based on the Metropolis-Hastings algorithm and Gaussian distributions [107]. [PERSON], [PERSON] and [PERSON] designed the study theme and conducted the literature study. [PERSON] and [PERSON] examined the data from different databases and performed initial data screening. [PERSON] interpreted the results and wrote the paper. [PERSON] and [PERSON] analyzed data, verified the results, and revised the paper. [PERSON] assisted in supervising the activities and study's well-organized procedure. All authors have read and agreed to the published version of the manuscript. This research received funding from the Research Council of Norway through (a) the CybWin (Cybersecurity Platform for Assessment and Training for Critical Infrastructures-Legacy to digital twin), project no. 287808; and (b) the SFI Norwegian Centre for Cybersecurity in Critical Sectors (NORCICS), project no. 310105. Not applicable.