# Prescriptive Maintenance: A Systematic Literature Review and Exploratory Meta-Synthesis
## 2 Methodology
### Systematic Literature Review  
The search strings are defined per the proposed RQs (Table 1). Only primary (original) studies are included to respect the PRISMA-SLR protocol. Since PsM is implemented in various industrial applications (e.g., manufacturing, aerospace, energy), there were no limitations in terms of determining the search strings. However, we specifically targeted industrial maintenance, and did not cover facility, infrastructure, and building maintenance. Given the research settings, we considered the PCC (Population-Concept-Context) framework (Table 1) as the most suitable option for constructing search strings. Given the topic's rise and to avoid missing essential studies, we set the following search strings: \"_prescriptive maintenance_\". The search strategy was limited to titles, abstracts, and keywords to avoid excessive and irrelevant papers. This approach aimed to exclude studies that only cite or reference prescriptive maintenance, ensuring that our studies explicitly address the concept of prescriptive maintenance. In addition, a search alert was \begin{table}
\begin{tabular}{c c c} \hline \hline
\begin{tabular}{c} Includes applications, tools, \\ methods, actions, etc. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The PCC question framework defines the focus of the research question. Figure 1: Research framework describing the analytical procedure of study retrieval, data acquisition, and meta-synthesis. The framework consists of six modules. set on Google Scholar and SCOPUS for the search string \"prescriptive maintenance\" in case new articles emerged during the analysis and writing of the paper. The PRISMA flow diagram (Figure 2) explains the process of study retrieval. Firstly, the search was performed using Harzing's Publish or Perish software (Windows GUI Edition, v. 8.9.4554.8721) to ensure replicability and transparency. Given that Web of Science and SCOPUS APIs (Application Programming Interfaces) could not be obtained, the search within these index bases was performed manually. The eligibility criteria used for the research are explained in Table 2.  
The rationale for proposing FTP's IC (Isolation Criteria) is to include all relevant articles. This includes peer-reviewed original journal articles, conference papers, and book \begin{table}
\begin{tabular}{c c c} \hline \hline
**Criteria** & **Sub Criteria** & **Description of Criteria** \\ \hline Isolation Criteria (IC) & Full-Text Papers (FTP). & Editorials, posters, or similar \\  & English Language (ENG). & records are excluded. \\  & Only Original (OR) studies. & Only articles written in English. \\  & Time Frame-Abstract & Only primary (not review) \\  & (TF-ABS) & The time frame spans 2013–2024. \\ Exclusion Criteria (EC) & Loosely Related (LR). & Theoretical, opinion, or roadmap. \\  & Partially Related (PR). & Only refers to PsM and lacks \\  & Non-Related (NR). & Not industrial (e.g., facility, \\  & & buildings). \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Eligibility criteria for selection and study retrieval. Figure 2: PRISMA flow diagram. chapters. However, we covered reports and theses if they were deemed valid in rigour by the review panel. Studies written in English were included to avoid misunderstandings in reporting findings. Only primary (original) studies were included, meaning that review (theoretical, systematic, or scoping) studies were excluded. The time frame and abstract criteria consider using only studies from 2013 to capture the evaluation of the Industry 4.0 era. Also, we limited the search to 2024 for the sake of completeness. Lastly, considerable efforts were dedicated to studies conflating PsM with PdM maintenance unless they explicitly address prescriptive actions (e.g., decision-making, optimisation). The initial search through the index bases resulted in 580 records. After extracting the records and inputting them into Mendeley, we performed duplicate removal on 390 studies.