# Taxonomy of Scheduling Problems with Learning and Deterioration Effects
## 4 Discussion
These approaches generally are accompanied by the use of any metaheuristic. Despite significant progress in these areas, many research opportunities can still be identified. Table 2 provides an overview of the opportunities and challenges. Additionally, they are described in depth below. * The current results show that the literature is oriented toward the development of models, the analysis of complexity, and the design and implementation of a solution method, instead of representing the real conditions more accurately. This encourages multidisciplinary collaboration to integrate scheduling theory with human factors, experts, ergonomics, psychological issues, etc. * There are few published articles dealing with the balance between economic and sustainable criteria (particularly as regards social orientation). It might be helpful to propose the study of scheduling problems with learning and deteriorating effects in which multiple criteria are evaluated, including social criteria. * There are opportunities for developing studies that address the estimation of parameters such as learning, deterioration or truncation. In general, the values of these parameters are based on the literature benchmark. However, there are few articles that are strictly dedicated to estimating parameters adjusted to the problem in question. * Every learning and deterioration model is based on one principle, such as job position or time. However, in the real world, there are other types or variables that could impact human behavior (e.g., environment, cognition, worker abilities, difficulty of work) [10; 50]. The development of multivariate models for predicting worker performance, which may be incorporated into scheduling problems, is therefore relevant. * As few articles include variables such as previous experience and task complexity in learning models [50], there is the possibility to deepen the topic to integrate these variables in models based on the position and the sum-of-processing-time. With regard to the approaches pertaining to deterioration, there is evidence of the need to integrate fatigue by addressing it through the inclusion of physiological variables, as pointed out in the literature [12]. There is likewise a need to study the effect that rest periods or rate-modifying activities (RMA) may have on performance. * Most of the works evaluate modeling and solution approaches using theoretical problems, while few papers provide case studies [2; 49; 71; 85]. Verification of the proposed assumptions and models for addressing the learning and deterioration effect in real-life production environments is an interesting area of research [13]. Thus, for example, collaboration with a business stakeholder makes it possible to study \begin{table}
\begin{tabular}{c c} \hline \hline
**Opportunities** & **Challenges** \\ \hline Approach the problem through complex considerations (e.g., flowshop, hybrid flowshop, flexible shop). & To manage and resolve real instances of the problem in situations of high computational complexity. Capitalize on the few articles that consider complex configurations from the theoretical perspective and bring them closer to reality. \\ \hline Incorporate novel criteria into objective functions. & Look at the industrial partners and identify the objectives they aim to optimize. Go back to articles that integrate increasingly important social and environmental objectives. Create collaborative relationships with industrial stakeholders. \\ \hline Develop models of learning and deterioration effects closer to real human behavior. Accurate estimation of the parameters included in these models. & Carry out multidisciplinary work that aims to incorporate human factor-related tools into scheduling problems. \\ \hline Devise and develop methods of solutions, to resolve the problem within a reasonable time. & Human characteristics may not necessarily be determining factors. Therefore, the integration of methods that address the problem and address uncertainty will be required. \\ \hline \hline \end{tabular}
\end{table}