**5. Data ownership sharing**

Data ownership sharing is the main mechanism for data consistency in managing multiuser interaction. Its aim is to ensure the transfer of virtual content among multiple users/players in real time [46]. Ownership of virtual content is applicable at the level of any application architecture. However, it can be effectively described, especially with the client–server architecture (**Figure 11**). The process of data ownership sharing consists of the following points:

**Figure 11.**

*Scheme of the data ownership sharing model.*


The acquisition of ownership depends on the collaboration logic associated with the context of the shared virtual game environment. In general, when a user/player interacts with a shared virtual object, he becomes its owner. The same principle is used in the case of the creation of one's own virtual object by some of the users/players. When ownership is acquired, the centralized virtual environment is automatically modified and the change is replicated to other users/players. The following rule applies in virtual environment sharing: In concurrent collaboration, one user/player can own a group of objects, but one object cannot have more than one owner at a time [47].

The ownership transferring occurs when a user/player transfers his own object to one of the other users/players. In this case, there is a modification of the transfer of ownership to the centralized virtual environment and subsequently to a specific user/player. Other users/players of the collaborative group are also informed about the ownership transfer. These receive replication about the status of the ownership transfer to a particular user/player.

The ownership leaving occurs when one of the users/players relinquishes the virtual object and he leaves it in a centralized virtual environment. Subsequently, the availability of the object is replicated to all users/players. Then, the object is available to players and it can be acquired.

Data ownership sharing can be also affected by specific collaboration or game rules. An example is the division of users/players into individual hierarchical levels. Then, the whole strategy of ownership acquiring and transferring changes according to these levels. The examples are the systems for training or instruction in a gamified form. In them, the users/players are most often divided into groups of editors, instructors, collaborators, or observers. In such systems, there are possibilities for ownership enforcement. This ability is usually available to users/players at the highest hierarchical level. Through ownership enforcement, it is possible to acquire a virtual object without it being transferred or left by its owner in advance.
