## 3 Research Stream Analysis
### RS2: MC Technologies and Methods  
The second research stream collects papers proposing practical technologies and methods, useful to manage variety in different phases of the product lifecycle, from the customer demand collection, through the design of product variants, to the final product manufacturing. These three main phases are used to further classify the papers belonging to RS2, constituting three sub-streams: \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Author(s)** & **Year** & \begin{tabular}{c} **Personalization** \\ **Approach** \\ \end{tabular} & \begin{tabular}{c} **Implementation** \\ **Context** \\ \end{tabular} & \
\begin{tabular}{c} **Performance** \\ **Evaluation Metrics** \\ \end{tabular} &
\begin{tabular}{c} **Sustainability-** \\ **Oriented MC** \\ \end{tabular} \\ \hline
[85] & 2023 & & & & & ✓ \\
[86] & 2023 & ✓ & & & ✓ \\
[87] & 2024 & & & ✓ & ✓ \\ \hline  & 63 & 15 & 14 & 17 & 20 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._RS2.1: MC technologies and methods for customer-manufacturer interaction RS2.2: MC technologies and methods for product design RS2.3: MC technologies and methods for production architecture  
3.2.1. RS2.1: MC Technologies and Methods for Customer-Manufacturer Interaction  
The 26 papers falling into this sub-stream, reported in Table 2, concern the possible methodologies used by companies to predict or identify customer requirements, supporting customer integration in the product design phase. Customer co-design is widely recognized as a key element of MC, considered a distinctive feature [93], a core aspect [57], or even a prerequisite [90] to address individual needs. [PERSON] and [PERSON] [49] emphasize customer involvement through a model structured in four phases: need analysis, service design and modularization, co-creation, and satisfaction evaluation. Similarly, [PERSON] et al. [107] identify four roles customers may assume in MC processes--co-design, co-production, co-configuration, and co-construction--depending on their level of engagement. Effective customer-manufacturer interaction helps reduce \"misfit costs\" [104], while co-creation fosters innovation and faster market adaptation [100]. Despite its value, acquiring customer requirements remains one of the most challenging aspects of MC [91]. The complexity of options can overwhelm customers--a problem known as \"mass confusion\" [63]--while some customers may struggle to articulate their needs. To support decision making and mitigate confusion, recommender systems using \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Author(s)**} & \multirow{2}{*}{**Year**} & \multicolumn{2}{c}{**Customer Co-Design**} & \multicolumn{2}{c}{**Decision Support Tools**} & \multirow{2}{*}{
\begin{tabular}{c} **I4.0 Technologies** \\ **for Interaction** \\ \end{tabular} } & \multicolumn{2}{c}{**Customer Preference**} \\  & & \multicolumn{2}{c}{**Mechanism**} & & & & **Prediction Models** \\ \hline
[88] & 2011 & & & & ✓ & \\
[89] & 2012 & & & & ✓ & & ✓ \\
[90] & 2013 & ✓ & & ✓ & & & \\
[91] & 2013 & & & & ✓ & & ✓ \\
[92] & 2013 & & & & & ✓ & \\
[93] & 2013 & & & & ✓ & & \\
[94] & 2013 & ✓ & & & ✓ & & \\
[49] & 2014 & ✓ & & & & & \\
[95] & 2014 & & & ✓ & & & ✓ \\
[96] & 2014 & & & ✓ & & & ✓ \\
[97] & 2016 & & & & ✓ & & ✓ \\
[98] & 2016 & & & & ✓ & & \\
[57] & 2016 & ✓ & & & & ✓ & \\
[99] & 2017b & & & ✓ & & & \\
[100] & 2017 & ✓ & & & & & \\
[101] & 2017 & & & & ✓ & & \\
[63] & 2017 & & & ✓ & & & \\
[102] & 2018 & & & & ✓ & & \\
[103] & 2018 & & & & & & ✓ \\
[104] & 2020 & ✓ & & & & & ✓ \\
[105] & 2020 & ✓ & & & & ✓ & \\
[106] & 2020 & & & & & & ✓ \\
[107] & 2020 & ✓ & & & & & ✓ \\
[84] & 2023 & & & & ✓ & & \\
[108] & 2024 & ✓ & & & ✓ & & \\
[109] & 2024 & & & ✓ & & & \\ \hline  & 26 & 9 & 5 & 11 & 6 & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Classification of the contributions related to RS2.1. data mining, e.g., [90], and mobile apps incorporating AR for product visualization [96; 99] have been developed.