## 5 Discussion
### Limitations of Collaborative VR in Documentation Review and Risk Assessment  
Some limitations still exist in fully using VR for maintenance documentation review and risk assessment processes. Most of the user test participants noted that reviews in VR would be good for early drafts and early risk assessments. However, the 3D model might not be always ready and available in very early phases of product development. Further focus needs to be given, therefore, to integrating the early creation of 3D models to the product development process. Additionally, as the 3D model is often updated during the product development cycles, it would also be essential to easily update the VR model when there are changes in the 3D model. Additionally, it would be beneficial if the VR environment would be able to indicate the changes made in the 3D model so that recent changes can be easily noticed.  
The quality of immersion and sense of presence improve the ability to identify risks. The modelling of tools and animating the movement of objects proposed in the results of this study agree well with other studies [40]. One problem for risk assessment in VR is that the environment is typically 'clean', with no odors, no noise, no temperatures, or equivalent. Hazard identification is based only on the visual observation of environment [41]. Therefore,people performing risk assessment need to be aware of and competent enough to identify hidden hazards.  
To improve the situation, we propose the following to enhance VR hazard identification: objects must have hazard-related metadata attached to them. This data can be made visible as an additional visualization layer that can be switched on and off. For example, objects connected to voltage sources could have a blue aura or shimmering, objects with chemical hazards a yellow aura, and hot objects a red aura. Different visualization, or audio feedback, if available, could be given similarly to any hazard, be it of mechanical origin, irradiation, pressure and so on.  
Even though the concept of the DocPanel was rated positively, its implementation had its limitations. For the DocPanel to be an efficient tool, enhancements and additions would be needed especially in navigation and annotation tools. As people are used to the current navigation and commenting functionalities of common office tools, such as Adobe Acrobat and MS Word, replicating those in DocPanel would lower the learning curve for the users of COVE-VR. From a multiuser collaboration point of view, a pointer tool would be essential. Maintenance method developers, documentation experts and risk assessment experts discuss details when reviewing instructions and assessing risks, and many times need to point out a small detail. In real life, with access to real equipment, this would be carried out with a finger, and all the participants looked for a way of pointing a detail or component to others in VR. In addition, drawing tools would further enhance the collaboration features of COVE-VR. The development of the DocPanel and the related tools and their usefulness to the processes described in this paper would offer an interesting further research area.