# Systematic Literature Review of MBSE Tool-Chains
## 3 Findings
### Techniques of MBSE Tool-Chains  
**RQ 3** aims to identify the techniques of MBSE tool-chains. Life-cycle properties are defined as systems properties that often manifest themselves after a system has been put to initial use during the life-cycle [16]. To investigate which life-cycle properties were captured by the papers, each life-cycle property was searched as a keyword. The results in Figure 6 demonstrate that both _safety_ and _reliability_ were the most frequently mentioned life-cycle properties. The studies were surveyed to understand the purpose of the models, as perceived by each author. Ultimately, when reviewing such papers, multiple purposes emerge; however, the results demonstrate that _understanding problems at an abstract level_ is the most important modeling purpose, as shown in Figure 7.  
Figure 6: Life-cycle properties related to the studies. Figure 7: Modeling purposes in the studies. Each study was analyzed to investigate which perspectives of system artifacts are formalized, including requirements, function, behavior, logic, physical architecture, interface definition, and verification & validation. Moreover, three types of formalisms were considered: (1) models; (2) mathematics; and (3) text. The results shown in Figure 8 demonstrate that system artifacts were formalized as specific models rather than text or mathematics. The requirements were the most frequently mentioned perspective formalized using models. Modeling and programming languages were also investigated in these papers. From the results in Figure 9, SysML was found to be the most widely used language in the tool-chains proposed in the studies. In addition to modeling languages, modeling methods (i.e., how to model) were investigated. Figure 10 shows that meta-modeling was the most widely used approach. Apart from modeling methods, simulation methods were also investigated. Among simulation methods, Figure 11 shows that the numerical simulation method was more general than other methods. Figure 8: Formalisms mentioned in the studies. Figure 9: Languages used in the studies. Modeling tools were investigated to understand how the authors developed and implemented models in MBSE tool-chains. In Figure 12, MATLAB and Simulink are shown as the most frequently used tools. In addition, MBSE tools were classified from the perspective of how to support life-cycle activities. As shown in Figure 13, system modeling was the most frequent life-cycle activity support. In order to understand how to support integrated verification, we investigated the integrated simulations and their solutions in these papers. Figure 14 shows the integrated simulation based on commercial tools, Modelica, and commercial tools for co-simulation; these were found to be the three main solutions used by the tool-chains. We found that more than half of the papers did not support integrated simulation  
found to be integrated using proprietary exchange rule data exchange based on standards, as shown in Figure 16.  
Figure 14: Integrated simulation used in the studies. Figure 12: Modeling tools in the studies. Figure 13: Tools classification. Tool-chain assessment is always a significant challenge when developing tool-chains [20]. Thus, in this paper, metrics were investigated for assessing MBSE tool-chains and were proposed based on standardized terminologies [21]:  
* Integrated capability, means the degree of combining software components, hardware components, or both into an overall system to constitute a tool-chain. * Interoperability, means the degree of two or more systems or components to exchange information and use the information that has been exchanged in tool-chains. * Traceability, means the degree to which a relationship can be established between technical recourse, system information, system development processes, and social networks. * Dependency, means the capability of disposing of the determinant of technical recourse, system information, system development processes, and social networks.