## 2 Literature Review on FJSS and Smart Manufacturing
Other studies develop a heuristics model and algorithm to optimize and support scheduling flexible job-shop systems [26; 27; 28; 29; 30]. In 2017, a heterarchical approach based on intelligent products was analyzed by [PERSON] et al. [31]. [PERSON] with [PERSON] and [PERSON] [32] developed a model of job shop scheduling in a customized manufacturing process. A simulation approach was proposed in some studies such as by [PERSON] et al. [33] that simulate a flexible manufacturing system for producing aircraft. A novel approach based on Machine to Machine (M2M) was well argued by [PERSON] et al. [34]. From our point \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multirow{2}{*}{**No. Articles**} & \multicolumn{3}{c}{**Documents by Type**} \\ \cline{3-4}  & & **Conference Paper** & **Article** \\ \hline
2020 & 3 & / & 3 \\ \hline
2019 & 9 & 5 & 4 \\ \hline
2018 & 2 & 1 & 1 \\ \hline
2017 & 4 & 3 & 1 \\ \hline
2016 & 1 & 1 & / \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Documents by year and type (source: Scopus). Figure 3: Publication volume and citations in the literature (source: Scopus). of view, it was also important to analyze the keywords in common with the selected documents and the most used ones. In this regard, Table 2 shows a classification of documents by keywords. The analysis of the literature review pointed out that the selected documents are very heterogeneous with each other. Most of them propose traditional methods for solving scheduling problems. Some of them highlight the importance of communication technologies as the key tool that enables the interconnection among a priori isolated business processes. Among them, [PERSON] et al. [35] analyzed the use of 5G and [PERSON] et al. [36] investigated the use of the Internet of Things, as they enabled manufacturing enterprise information systems to solve scheduling problems. Already in 2010, [PERSON] et al. [37] proposed a hybrid algorithm for production scheduling integration in holonic manufacturing systems. It is also clear that in modern competitive companies, the scheduling problem is also associated with correct maintenance, as pointed out by some authors [38; 39]. In addition, it is important to note that, although several studies on FJSS have been published, the integration of a decision tool based on MCDA is not treated to solve the flexible job shop scheduling problem. However, it is clear that in a dynamic and complex environment such as the modern smart factories, the use of multi-criteria decision-making methods could represent an opportunity from a practical and problem-solving point of view, as stated by several authors [40; 41; 42]. In this way, more perspectives can be considered. It is a fundamental management strategy from a smart manufacturing perspective in which many factors must be taken into consideration. In fact, scheduling is a \"form\" of decision-making, which consists in allocating finite resources in such a way that a given goal is optimized. A scheduling problem contains the following information: (1) the decision variable and (2) the criterion by which the decision variables are evaluated (performance measure). In other words, a solution to a scheduling problem consists in identifying the optimal decision in the sense specified by the particular criterion adopted. As -making methods definitely represent a very effective tool in modern factories from a managerial point of view, our research aims to cover the literature gap.