# A Categorization of Digital Twin and Model-Based System Engineering Interactions
## 2 Materials and Methods
### Search the Literature  
This step focuses on searching the literature for articles related to the topic [23]. Therefore, databases must be defined and the search formula must be written. For this review, two bibliographic databases were identified: SCOPUS and Web of Science. The selection of these databases was due to their status as the two most comprehensive repositories of publication metadata [25]. The choice to use two databases rather than a single one was made to mitigate the potential for topic-related blind spots within the databases. Considering that the topic of this review was the relationship between digital twins and model-based system engineering, both terms had to be present in the search formula. In our context, MBSE is a common means of referring to model-based system engineering and was also  
Figure 2: Methodology for the review presented in this paper. Created by the authors. included in the search formula. Finally, MBSE is a model-based approach, and it can be referred to as such. Taking these terms into account, the following search formula was constructed and used to search for article titles, abstracts, and keywords:  
(\"digital twin\"*\" AND (MBSE OR (\"model-based\" AND ((system engineering) OR approach)))). The database search was conducted on 17 September 2023, with no restrictions on the publication date or document type. The search found 724 records, of which 469 were from SCOPUS and 255 from Web of Science. The data were imported into Microsoft Excel and analyzed. After removing 230 duplicate entries, 35 records lacking author information, and 15 non-English records, 444 records remained for screening. The records were assessed based on two key metrics: the year of publication and citation frequency. Figures 3 and 4 illustrate these analyses. Figure 3 shows the growing interest in the topic over the years, with the publications increasing from 21 in 2018 to 110 in 2023. Notably, the observed decline in publications from 2022 to 2023 resulted from limiting the search to records published before September 2023. Figure 4 shows that 318 records (71.6%) had fewer than 5 citations, but 19 (4.3%) records were cited over 40 times, and one of them was cited 517 times. It also highlights that the number of records levels off beyond 10 citations. We screened the records using their titles, looking for mentions of digital twin- or MBSE-related terms. This screening resulted in the removal of 110 records from the study. The next screen focused on the records' abstracts. We read each abstract, seeking indications that the article would discuss some form of interaction between DTs and MBSE. This screening resulted in the exclusion of 262 records. The next step involved the retrieval of articles/papers, including those accessible via open access and those available through the University of Brasilia. Among the remaining 72 records, only 6 records were not available  
Figure 4: Distribution of citation counts per record. Created by the authors. Figure 3: Number of records published by year. Created by the authors. for download and had to be eliminated from the study. To ensure high quality, and based on the results from Figure 4, articles with fewer than 10 citations were excluded, resulting in the removal of 45 articles. Finally, 21 articles were considered for this review. It is worth mentioning that this selection process excluded newer research that could have been relevant but had not yet been referenced sufficiently by others; however, this work was not intended to be a comprehensive review of the topic, as stated previously. We analyzed the entirety of the remaining articles to determine their relevance to the research topic. During this evaluation, we found that five articles did not discuss any form of interaction between DTs and MBSE. Consequently, these articles were removed from the database, leaving a total of 16 articles for review. The list of selected articles is shown in Table 1, ordered by the number of citations.