## 3 Analysis of the Collaboration in AR Context
### Conceptual Framework to Define Collaboration
For example, in the SmARt city scenario, the municipality could establish a _hierarchy-based_ model over service layers to force and control specific aspects of the city management; at the same time, urban service operators working the same hierarchical level could own and control their network of resources (_ownership-based_ model), while interacting with others providers on shared resources following a _turn-based_ model. Figure 2 illustrates an example of the combination of multiple collaboration models. \begin{table}
\begin{tabular}{c c c l} \hline \hline  & **Use Case** & **Voxel-Based Prototype** & **SmARt City** \\ \hline Unconstrained & When parties coordination & A choice if every player is & Not adequate, as it is assumed that the \\  & is not needed or relies on & cupless simultaneously and & number of services service providers and \\  & human means & coordination relies on & to need at least information filtering \\  & & peer-to-peer communication & services for visualization \\ \hline Tum based & When resources need to & A choice if every player is & A choice in case two or more service \\  & be univocally controlled & empoweredto add and remove & providers share a common resource and \\  & by a single user at a given & cubes and coordination needs & may have control over it e.g. a single \\  & moment in time & to be orchestrated to avoid & pand in which alerts can be presented may \\  & & conflicts and organize interaction & be admitting new information in case the \\ \hline Layer based & When resources need to & It does not apply, as this & Layes will be in this application associated \\  & be grouped and the access & application only contains a & collection, at quality monitoring, traffic \\  & to those groups has to & single node: the terrain mesh & controlling..) Each layer will contain a set \\  & be managed & that players will modify & of nodes in it and will be secured by applying \\  & & & role-based access. Users authorized for each \\ \hline Ownership based & When a user owns one or & Not applicable, as this application & \\  & fill control over them. & only require a single resource & Applicable to determine e.g., which operators \\  & These resources could be & for common interaction: the & can access and visualize the state of specific resources. \\  & within the same layer & terrain mesh that players will modify & A hierarchical model does fit the \\  & or not & The basic application is built on & collaboration control in this application, as \\  & & players with the same role, thus & there will be users with different roles that \\  & When a hierarchy of roles & the hierarchy-based model does & depending on their role, e.g., municipality \\  & is needed to control the & not fit. In case hierarchies are & (overall control), service providers (overall \\  & different resources & implemented, it is assumed that & monitoring of the service, interaction with shared resources), service managers (actual \\  & & master) would have a subset to & decisions in service layer and over owned \\  & & approve the initiatives of the others & resources) and operators (visualization and \\  & & information generation over authorized resources) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Use cases of the collaboration models and it suitability for the voxel-based game and the SmARt city prototypes. As can be seen in Figure 2, a _layer-based_ model is present, with three managed layers: _Traffic Lights_, _Cleaning Services_ and _Air Quality Data_. Access to the _Traffic Lights_ layer is granted to a Traffic Lights Manager, which _owns_ the nodes associated with the traffic lights. At the same time, access to the _Air Quality Data_ layer is granted to multiple clients. Those clients generate and _own_ the nodes associated with different weather stations. These clients could be institutions or citizens, being the ownership associated with them. Also, at the same time, a hierarchical-based model may be used to establish the control over the elements of the _Cleaning Services_ layer.