## 1 Introduction  
The integration of new information and automation-based technologies in industry is leading to a revolution, known as Industry 4.0, which is profoundly changing industrial processes and the workplace itself. The concept of Industry 4.0 was introduced in Germany in 2011 with the presentation of an initiative named \"Industrie 4.0\" [1]. Although there is no consensus on its definition, an important feature of Industry 4.0 is the integration of new technologies (such as the Internet of Things (IoT), cyber-physical systems (CPS), and virtual reality (VR)) into industry, enabling flexibility, robustness, and adaptability over time to cope with a changing business environment [1; 2; 3]. It is considered the fourth industrial revolution and may deeply change the future of manufacturing and production processes, leading to smart factories and interconnected industrial environments [4]. In this context, production becomes highly configurable and industrial processes change rapidly in order to adapt to changes in demand. VR is a key technology adopted in Industry 4.0 to provide an efficient and cost-effective way to model industrial processes. Research and development carried out by both the academic community and industrial companies has made VR mature, stable, and usable. This technology has proved to be effective in many industrial applications such as design, virtual prototyping, decision making, virtual assembly, training, manufacturing, ergonomics and knowledge capture, and process planning and simulation [5; 6] in different fields of engineering such as automotive, aerospace, and mechanical engineering, among others [7]. Augmented reality (AR) is rapidly evolving too. AR is a technology that allows for the overlaying of digital information on the real world and hence augmenting a real environment with computer-generated information and objects that are displayed in real-time and may be dependent on the real environment itself (context-sensitive) [8]. An example of AR in an assembly operation is a text displaying the next task that a worker has to perform and an arrow pointing to the next part to assemble. It has been used recently in many different areas of knowledge such as medicine, construction, and industry. In the last case AR is being used to support process monitoring [9], human-robot interaction/cooperation [10; 11], maintenance [12; 13; 14], and assembly [15; 16; 17]. Planning an industrial process is normally a very complex and time-consuming process. Usually it is an iterative process prone to finding problems that cannot be predicted until the entire process is implemented. Making a virtual simulation of the process first can help to identify different issues beforehand, preventing unexpected costs and time-loss in advance. This is especially true in the case of immersive process simulators that can take advantage of the feedback provided by workers or validation engineers. In Industry 4.0, a simulator has to incorporate not only the human factor, as this is of great importance in planning, testing, and improving processes [6], but also all the automation systems that interact with humans, such as collaborative robots. Contrarily to most VR-based simulations that are fixed, an industrial simulator must be flexible enough to cope with the fast-evolving needs of industry. For these reasons, there is a need for a structured way to model the industrial processes within a simulator considering three relevant factors: flexibility, to adapt to different purposes and application domains, and also to allow faster development; interaction of different actors (human and automation systems); and appropriate feedback to assist users throughout the entire process. The goal of this research is to present a new framework that focuses on modeling Industry 4.0 processes for virtual simulators.