# Smart Platform for Monitoring and Control of Discrete Event System in Industry 4.0 Concept
## 2 Preliminaries and Problem Formulation
### Development of a Mixed Reality Application
#### 3.4.5 Appearance of the Application  
Since the application was developed for the MS HoloLens 2 device, the appearance of the application was designed according to the MRTK design. The components from the MRTK templates library were used and modified according to our needs. The application contains a main menu with the option of activating and deactivating communication with the MQTT broker, displaying the active production line, and debugging buttons for activating individual production lines. Since it is a mixed reality application, it was not possible to use common practices, like web or mobile applications. The menu is therefore realized by following the user with the possibility of opening and closing, as it occupies a large area when open. The menu is animated upon interaction. Each of the lines provides multiple panels, and when a production line is recognized an initial panel is displayed with the option of redirecting to all panels that the production  
Figure 17: Three-dimensional visualization of the button. concept enables a new object to be added (device, machine, production line) with minimal effort, including its visualization. The proposed solution meets all requirements in terms of interoperability and scalability, due to the use of the OPC UA protocol and the use of configuration files for generating the content of individual devices and their functionalities in the application. The contributions of the developed smart platform can be summarized as follows:  
1. The design and implementation of an original smart platform for monitoring and controlling discrete event systems using intelligent technologies As part of the proposed solution, a software application system was designed and implemented to support the monitoring, diagnostics, and control of discrete event systems. The developed platform is based on modern smart technologies and concepts such as the Internet of Things, augmented reality, computer vision, and cloud computing. These are key technologies for the digitalization of production processes in practice and are included in the concept of Industry 4.0. 2. The implementation of a system for monitoring and controlling discrete event systems on a headset for augmented reality The application was implemented on the currently most advanced headset for augmented/mixed reality, Microsoft HoloLens 2, using the Mixed Reality Toolkit library. Conventional solutions use mobile devices, such as smartphones or tablets. The use of a headset thus brings many advantages, especially the fact that the operator's hands remain free when using the application system. We can consider the developed solution not only within the framework of Industry 4.0 but also as a human-centric solution, which is one of the pillars of the Industry 5.0 concept. 3. The use of industrial standards and industrial hardware components in the designed smart platform The application uses the industrial communication standard OPC UA and a PLC, which makes it different from other solutions that are often based on common communication protocols that can only be used in the consumer IoT and prototyping electronics, such as Arduino and the like. 4. The modification and expansion of the concept of definition schemes for the dynamic generation of a GUI in augmented reality, its implementation, and its verification significant result of the work is the modification and expansion of the concept of definition schemes for the dynamic generation of graphical user interfaces for augmented reality systems presented in the work. The modification and expansion consist of the use of the MS HoloLens 2 augmented reality visualization device and extended options for setting and visualizing objects. 5. The verification of the designed and implemented smart platform on two laboratory production lines The developed original smart platform has been tested and verified on two laboratory discrete event systems--production lines: 1. A laboratory model of the production line with optical sensors, position sensors, conveyors, and two machining tools; 2.