## 2 Related Work
### Shared vs. Non-Shared View and Control  
Shared views and interaction (or control) for multiple users play an important role in collaborating within a VR environment. [PERSON] et al. [48] presented preliminary ideas toward a vision of personalized views in immersive collaborative analytics systems. The different separate views in a system developed by [PERSON] et al. [49] caused confusion in their participants, especially when they wanted to communicate with each other what they saw in the virtual environment. Their results indicate that an appropriate interface should have a component that allows participants to share their views to help maintain proper coordination of activities and group analytical efforts. [PERSON] et al. [11] suggested that a shared view of the workspace activity and the ability to interact and build upon others' work facilitates the process of developing ideas during collaboration. [PERSON] et al. [50] presented the CoMotion application to allow group sharing. When working together with CoMotion, the shared frame remains active even if the original user's workspace is closed, providing both synchronous and asynchronous collaboration. However, their research is for desktop displays, not for VR. Besides, [PERSON] et al. [32] added a broadcasting function where users can obtain a shared view of the workspace with another user. For the research above, only one study mentioned the user study [11]. Others, however, did not report any experiments with users.  
On the flip side, [PERSON] and [PERSON] [6] have argued that shared views and manipulation could be detrimental to users' explorations because they can be distracted by other users' actions and can lead to the unawareness of any changes to their own representations. [PERSON] et al. [51] looked at the role of specialized views in their projection-based VR system. They concluded that these specialized views might be effective for reducing information overload or balancing the boundary between public and private spaces. One aspect that they did not explore is whether the non-shared (private) views would enhance collaboration compared with having the shared (public) views only. [PERSON] et al. [5] explored collaboration modes using a volumetric rendering application with three modes: loose coupling, tight coupling, and master/slave coupling. They, however, presented only limited results and without showing clear patterns of three collaboration modes. In addition, they did not have an entirely noncoupled mode and pointed out another important limitation: their users were not totally aware of which parts of the system were synchronized in the different collaboration modes.  
In summary, most research has only explored how users interacted with their own workspace or with the same space together, as a group. However, the above research points to the fact that there is still very little work that has thoroughly investigated the effects of shared and non-shared interaction and view on collaborative exploration of visualizationsin VR environments. In addition, little exploration has been carried out with tools that can support users in freely switching between public and private workspaces. Our research aims to fill these important yet under-explored aspects of VR environments.