## 3 Methodology  
Cooperation between research partners and the chosen methodological approach was set as a combination of an in-depth literature review, conceptual development, and simulation techniques in a specific case study. The study refers to manufacturing companies with a production network, plant, or group of machines with a certain capacity to serve a specific market.  
The method used to reach the goal of matching market demand started from analyzing the structure to develop the conceptual model. For this purpose, the viable system model (VSM) was selected. The VSM is a cybernetic model that was developed by [PERSON] throughout his life [10]. The viable system model is a reference model that can be applied to describe, diagnose, and design management models in organizations [11]. [PERSON] deduced the VSM from cybernetics, and from the central nervous system of the human being, in order to deal with complex systems [12]. Through the analysis of the central nervous system, the minimum requirements that a system must meet to ensure that it is viable were derived [13]. In this way, each sub-system has one of the nervous system's functions. The nervous system is composed of units that execute actions, such as the spine, muscles, and organs (System 1),the spinal cord (System 2), the brain stem (System 3), the diencephalon (System 4), and the cerebral cortex (System 5) [11]. Analogous to the planning levels of a company, the structure of the VSM can be divided into three levels. Therefore, Systems 1-3 (including System 3*) are assigned to the operational level. System 4, in turn, represents the level of strategic planning and stabilizes the entire system thanks to its interaction with the environment. System 5, finally, represents the level of normative planning [11].  
Moreover, in order to determine which policies should be used to control the behavior over time and how these policies should be designed and implemented in order to have a robust response against change [14], system dynamics was chosen. Vensim, a software package enabling system dynamics modeling, was selected for this project. Vensim is a software program that allows for the simulation of highly complex and dynamic systems that involve a lot of integrated decision-making. Vensim (Vensim is a registered trademark of Ventana Systems Inc.) provides a high degree of rigor for writing model equations. It adds features for tracing feedback loops. Vensim also provides very powerful tools for the optimization of multi-parametric simulation results, which allows the analysis to validate results and the model's structure, as well as to determine the most convenient policy options by parameterizing these policies.  
The innovative approach relies on a combination of the following, in order to generate a decision-making support concept and model in Vensim for balancing supply and demand over time for a specific production system including economic influences:  
* The viable system model as a framework for developing the conceptual model;
* System dynamics for designing and controlling the production system's behavior;
* Statistical process control for demand pattern monitoring;
* Forecasting methods for calculating a demand forecast per period.  
Once the methods were set, an in-depth literature review of demand planning, capacity planning, and adaptability, along with key indicators for capacity-related decision-making, was performed. As a result, the basis for the conceptual model development was built. It is an integrated model created for all kinds of manufacturing organizations. Later, the generic conceptual model was extrapolated and proven for the case study of an OEM plant. A simulation was programmed in Vensim using assumptions, and validation with extreme values was performed. Finally, different scenarios and decisions were simulated in order to test the hypothesis previously defined.