## 5 Discussion
### Industrial Use Cases for Asymmetric VR  
Supporting the previous studies [2,8,16,17], we argue that VR technology is a game-changer for industrial processes and one of the most important production tools to supplement and optimize product and related services design and development processes in line with Industry 4.0.  
Particularly answering **RQ1**, our case study demonstrated the value of asymmetric VR settings to support the collaboration of multinational departments in two key ways: (1) _to design maintenance methods_ and (2) _to draft technical documentation_. Design for maintainability requires an understanding of how maintenance can be done efficiently (e.g., Can the technician reach something? or Is there enough space for performing maintenance tasks?). Hence, it is critical to correctly perceive the scale of the space. One shortcoming of exploring 3D CAD models on a 2D computer screen is lack of understanding of the real spatial dimensions. Therefore, one of the major tasks for these use cases is to accommodate 3D model exploration tasks in VE on a 1:1 scale among geographically distributed experts. In addition to improving the spatial understanding of the VR-users [57,66], our expert study showed that the spatial understanding of the Teams-users was also improved with the asymmetric settings. The possibility to communicate verbally while observing and guiding VR-users (and their avatars) to interact with the 3D model in virtual space improved their understanding of the scale. Furthermore, the use of virtual tools for content creation (e.g., Textbox or Camera tools) enables easy capture of digital materials that can be utilized for compiling draft versions of documents and further supporting the communication process.  
Interaction with 3D CAD models is an important task in many industrial contexts [4,34,49] which may be performed throughout the product development lifecycle in other use cases. The asymmetry for this task can be applied to boost scalability and include users with no access to HMDs in the collaboration process, thus addressing existing challenges of industrial maintenance, such as the lack of understanding of the real scale when developing maintenance methods. The asymmetry in both use cases can be dynamically arranged to enable appropriate knowledge transfer, depending on team composition, and requires only one VR-user to manipulate a 3D model and demonstrate it to remote users.  
Expert insight also showed the value of the asymmetry between VR-users and non-interactive desktop users for other industrial use cases, such as (3) _global training_ and (4) _virtual maintenance assessment_. Asymmetry in the training process is based on knowledge transfer from experts to novice learners in a simulated safe environment [7]. In this scenario, an expert (knowledge owner) would participate as the VR-user, whose point-of-view would be streamed to learners via traditional conferencing tools. This way, learners may follow the educational materials from any physical location and any platform. Similarly, as described by [PERSON] et.al., [59], another use case for asymmetric VR settings in industry is in virtual maintenance assessments. In this case, the asymmetry is reversed. The maintenance expert (knowledge owner) would be a desktop user, who would follow a technician's actions in VR and evaluate the efficiency of the maintenance method. Performing both use cases mentioned in a real industrial context might be dangerous or even impossible. Hence, applying asymmetric VR to enable global training and virtual maintenance assessment could improve the company's overall accessibility and sustainability by granting access to flexible simulated environments and, consequentially, reducing travel costs. Therefore, distributed asymmetric VR in the industry can prompt agility in the processes by reducing travelling times to training or testing sites [67] while increasing access for users that do not have HMD hardware available [35].