## 2 Related Literature  
### AR Assistance in Processes  
In the most recent decade, XR seems to be one of the most developing and studied technologies for supporting systems and processes. There is a wide range of AR applications reported in the scientific literature. Their main goal is to assist human capabilities to improve the speed and the efficacy of supported processes [2]. This aim becomes especially significant in processes where, even though machines and digital systems are engaged, a person is still necessary to carry out a process or parts of a process. The increasing interest of scientists and practitioners and the promising results of AR applications in various domains inspired the premise to conduct the research presented in the paper. An example of a typical domain where XR is implemented is education. The technology is used there to increase the human capability to learn by experiences provided by virtual and immersive reality [13]. Training by XR tools has become a part of the typical training of high-expertise professions like medicine, driving, piloting, firefighting and the emergency management of cases of earthquakes, floods, thunderstorms and radiation, but XR tools also help in understanding e.g., geometry, etc. [13; 14; 15]. Other processes assisted by XR technologies which are often studied in the literature include logistic processes [1; 2; 16; 17], visual quality control, e.g., maintenance or the structural health monitoring of a building or material structure [18; 19; 20; 21], navigation systems [22] and the planning of urban development [4; 23]. Among the benefits of AR advantages, [PERSON] at al. [19] point out that AR tools improve comfortability, reconfigurability and flexibility of operations in service and production processes. AR can also be a practical tool for enhancing a human's perception during visual inspections and can generate real-time information based on computer picture analysis [18]. The use of AR technology lets an operator of a process be immersed in a natural environment and enriches their perception at the same time. The operator's awareness of additional support can reduce their psychological discomfort in regard to making a mistake [17], and it can also improve the perception of monotonous and repetitive tasks [14]. On the other hand, there are a few drawbacks mentioned in the literature, such as technological issues, e.g., device's limited computational resources (especially after longer periods of work) or battery consumption, which limits the operational time of AR tools, and psychological issues, e.g., the continuous monitoring of virtual objects could negatively influence human cognition and can lead to motion sickness [24]. The literature review presented in [25] confirms that the use of the AR technology in warehouse operations has numerous advantages, e.g., the reduction in their cost and the improvement of the efficiency of warehouse processes. However, the results described in the literature also indicate the negative impacts of the long-term use of AR tools, such as visual fatigue, headaches, dizziness, discomfort and cause of distraction [25]. Reviews of AR use in different domains can be found in [3; 4; 15; 19; 20; 21]. Refs. [26; 27] report the results of an AR study conducted in a manufacturing assembly line where workers could use paper-based and AR-enhanced instructions presented on screens. The completion time, the error rate and the essential workload in the case of the AR application have been improved. The same effect has been observed in [28; 29], and the authors conclude that the improvement effect increases if the complexity of the tasks rises. Improvements in logistic processes' efficiency and productivity have also been reported in [14; 24]. A leading area of AR application in logistics is the order-picking process [30], which is particularly prone to human error. For this reason, AR tools are used to support determining the right path to the correct location, picking the right goods and choosing the correct quantities [31; 32; 33; 34].