Figure 4:

Database model of the central server (Fig. 3). The users are always members of a party, which can participate in multiple collaborations. Within a party, users can have different roles (e.g., an administrator is allowed to accept collaborations). For each collaboration a party takes place in, it should create a (running) node. Tasks are always part of a single collaboration and have one or multiple results. In turn, results are always part of a single task and node.