# Systematic Literature Review of MBSE Tool-Chains
## 2 Research Methodology
### Research Questions  
The objective of our study was to investigate the current state of the art pertaining to MBSE tool-chains. In particular, peer-reviewed literature was used to characterize and synthesize available contributions with respect to the investigated research topics, research types, research methods, contribution types, and research gaps in the context of MBSE tool-chains. The main research question driving this research and reflecting our objective was as follows (four research questions were posed, each of which addresses a particular aspect of MBSE tool-chains):  
1. **RQ 1**: What is the intensity of the research on MBSE tool-chains? This research question was designed to identify the scope of research topics associated with MBSE tool-chains. The investigated views are summarized in Table 1.
2. **RQ 2**: What are the most frequently investigated research areas related to MBSE tool-chains? Furthermore, what application areas have they been used in? This research question was used to analyze how MBSE tool-chains support researchers' work in systems engineering and to capture which domains they are in. It was analyzed by the given information about application domains and functionalities of MBSE tool-chains, as illustrated in Table 1.
3. **RQ 3**: What are the most frequently applied research types and research methods? This question was used to understand which techniques can be used to construct MBSE tool-chains. Four aspects were considered: social perspective, process, information, and technical perspective based on the SPIT framework for tool-chain development [3]: * The social perspective refers to an explicit network of stakeholders related to system development as well as environmental constraints and policies regarding MBSE tool-chain development and implementation. We focused on identifying stakeholders, referring to authors and their relevant studies. * The process aspect refers to development processes of the target systems developed using MBSE tool-chains. For this survey, we focused on the development phases in which the tool-chains are implemented. * The information refers to system artifacts of complex systems. We focused on understanding the life properties from a system engineering perspective, which the MBSE tool-chains aim at. The life properties were selected based on [PERSON]'s definitions [16], including: (1) quality; (2) reliability; (3) safety; (4) flexibility; (5) robustness; (6) durability; (7) scalability; (8) adaptability; (9) usability; (10) interoperability; (11) sustainability; (12) testability; (13) modularity; (14) resilience; (15) extensibility; (16) agility; (17) manufacturability; (18) repairability; and (19) evolvability. * The technical perspective refers to the related technologies for constructing MBSE tool-chains. We expected to understand the contents related to: (1) modeling purposes; (2) modeling languages; (3) modeling methods; (4) simulation methods; (5) modeling tools; (6) solutions for integrated verification; (7) tool integration; (8) testing; (9) process modeling; (10) process control and management; (11) model checking; and (12) optimization [17].
4. **RQ 4**: What contributions are provided by research related to MBSE tool-chains? This question was used to clarify the authors' contributions. We summarized the authors' contributions from the papers, including: (1) framework/method/technique; (2) guidelines; (3) lessons learned; (4) models; (5) tools; (6) surveys; and (7) tool-chain architectures. Moreover, metrics accessing MBSE tool-chains were surveyed from the literature reviews, which included: (1) dependency; (2) interoperability; (3) traceability; (4) integrated capability; (5) reusability; (6) design efficiency; and (7) scalability.