## 1 Introduction
To enable manufacturing companies to process the increasing data gathered, useable models providing sustainable solution alternatives must be developed [11]. Until recently, there has been no modeling method or methodology which can be used to model, analyze, and design complex manufacturing systems completely or support most phases of these complex systems. Most available modeling methods are simply static graphical representations and are not well defined. Modeling requires a method that is simple and able to support different levels of abstraction. Analysts and designers need to model basic manufacturing operations as well as relevant management decisions and information systems. Most authors agree that no one technique can model the functional, information, dynamic behavior, and decision aspects of systems [12]. Furthermore, at the moment of writing this paper, no function-based concept has been published for modeling manufacturing organizations. As a result, the novelty of the paper relies on the development of a function-based model for manufacturing organizations. Moreover, the conceptual model develops its application for the identification of improvement potentials and for the diagnosis of malfunctions based on failure mode and effect analysis (FMEA) for manufacturing functional areas. Furthermore, the model enables its application as a digital model by simulating the different functional developments over history. In this context, historically, researchers and practitioners have often failed to consider organizations as a sum of functions leading to a set of capabilities that produce a product that can serve society's needs. Furthermore, functions have increased with the development of industrial revolutions. This has occurred in all areas from technical manufacturing processes to maintenance management passing by quality and logistics management. Although possibilities to enhance functions as well as to increase their effectiveness, efficiency, and scope have developed over time, many manufacturing organizations have not realized their potential, as can be explained when new companies overplay existing players in relatively short-time periods as they are able to utilize all the new functions available enabling greater competitiveness in global markets. As a result, many industrial organizations do not know why, where, and when the existing functions and projects for implementing new functions fail. Moreover, with the advent of Industry 4.0, the connection of the physical and digital world has led to cyber-physical systems and digital twins. However, in most cases, the focus of these research and practical applications relies on the operative levels of the main functions of manufacturing organizations, i.e., manufacturing process, maintenance monitoring, quality control for products, and processes. In this context, the tactical and strategic functions of a manufacturing organization are commonly overseen. Thus, the aim of this research was to propose a holistic approach for manufacturing organizations in order to model their functions enabling the assessment of the organization's performance and identifying improvement potentials. For this purpose, a conceptual model was developed based on the evolution of functions along with the industrial revolutions in order to identify an integral generic set of functions relevant to the assessment of any manufacturing organization. Moreover, using the conceptual model, manufacturing organizations can be modeled, considering all common organizational functions in the respective areas of production, maintenance, and quality, etc., in the three planning horizons--strategic, tactical, and operative. As a result, the models serve as a basis for the integral management and control of manufacturing organizations, since they can be applied for the design, management, and control of operations as well as for identifying and quantifying potential improvements.