## 3 Literature Survey and Critical Analysis
### Summary of Critical Points Identified in the Literature Analysis  
Now that the literature falling in the intersection between energy-aware production scheduling and multi-objective metaheuristics has been described, we now summarize the main observations that emerged from the critical analysis of such works. Before proceeding further, we claim that with this critique, we did not aim to discourage the readership from performing research at these crossroads, but rather (1) to underscore realistic aspects and assumptions that are tightly coupled to real-world settings, (2) to pinpoint poor practices that should be avoided in prospective studies, and (3) to call for research efforts in directions of inherent value for the field. Such observations are exposed in what follows:  
* The first taxonomy given in Section 3.2.1 uncovered that most JSPs solved in the analyzed literature corpus addressed two or three objectives. This conforms to real-world settings, where production scheduling is often driven by a few key performance indicators. Nevertheless, we emphasize that the potential of multi-objective metaheuristics to seamlessly cope with problems comprising several objectives should be propelled by a real-world need for taking them into consideration. In this regard, most cases reported in the literature posed sophisticated mathematical problem statements without giving an explicit rationale connecting the problem statement itself to real-world circumstances, KPIs, and constraints. This not only hinders the generalization of the studies, but also questions whether the research is truly motivated by real-world problems. * The formulation of the JSP is based mainly on energy consumption and makespan. This is not an issue, but rather a consequence of the fact that in most practical settings, scheduling in industrial plants is governed mainly by production efficiency, i.e., the production of as much product as possible. The relatively low number of scientific works related to energy-aware production scheduling (slightly above 60 references) is also symptomatic of the fact that it has not been until recently when energy efficiency has become a concerning issue in real-world industries. Several reasons for this growing concern can be speculated around the sharply increasing energy costs, particularly noticeable in certain countries [96]. This fact is encouraging and should catalyze efforts brought to the area surveyed in this work;
* On the negative side, and repeating previous claims, we encountered that most types of JSPs tackled in the analyzed studies were largely specific for the use case under target in the paper, leading to a loose generalization of the results to new real-world setups. Again, this should not be considered an issue if the work at hand confined the conclusions of its experiments to the JSP variant under consideration. However, this was not the case in a subset of the references examined, wherein the novelty of the JSP problem was entangled with the proposal of a novel metaheuristic algorithm without any solid reason. This echoes the longstanding controversy about the role of the metaphor in the design of nature-inspired metaheuristics. We also noted this practice in several works resorting to new biologically inspired solvers over ad hoc JSP formulations, avoiding (1) the inclusion of well-established multi-objective algorithms in the comparisons and (2) the reproducibility of the results of the benchmark leading to the claims about the performance of the new solver. Principled and thorough performance studies should be performed in prospective works to clarify whether the performance of such solvers corresponds to a truly better search capability of their bio-inspired operators;When it comes to the realism of the formulated problem, very few papers took into account aspects that are prevalent across the production plants of a diversity of industries, such as waiting times, maintenance cycles, machine downtimes, and other aspects that impact the overall computation of the makespan.