## 5 Demonstration Use-Case
### The Experimental Scenario  
The use-case scenario presented here addresses the production (assembly and delivery) of ball-valves and thermometers in one of the MESS premises. The physical components of the pilot system participating in the use-case scenario are shown in Figure 8. The layout of the realized MESS, the sequence of HRC dynamics, and the involved logistics for the material handling (noted with \(a1\_a3\), \(b1\_b2\), \(c1\_c3\) routes) are depicted in Figure 9.  
The main steps of the use-case scenario can be summarized as follows:  
* Request of an AGV at the warehouse, where the human operator loads the pieces needed at the box handling cell;
* In parallel, another AGV is dispatched to the warehouse for the necessary ball-valve assembly pieces;
* AGVs deliver the materials to the docking positions indicated;
* The box-handling robot picks up the pieces, orders them, and releases the box by positioning it onto the AGV;
* At the ball-valve station, the human operator picks up the pieces, places them on the fixture, checks position and tools, and acknowledges back. Calibration and assembly operations then follow. When completed, the human operator loads the assembled ball-valve onto the AGV, which delivers it to the warehouse;
* The human operator at the warehouse unloads the manufactured pieces and stores them. The AGV is then released;  
Figure 9: Realized MESS layout: involved CPSs, human activity, and implemented logistics. * At a certain time, another AGV is requested to the factory line #1, which is operating on the thermometers;
* When completed, the robot from factory line #1 will load the fixture containing thermometers onto the AGV, which will finally deliver them to the warehouse;
* As in point 6;
* AGVs are finally released and sent to the docking station for charging. The list of targets and relative services implemented via OPC UA for each CPS in the demonstrated use-case scenario is reported in Table 5, whilst the graph in Figure 10 illustrates the concatenation of CPS services in the form of a schematic operation graph (routing), with their execution preconditions (precedences between nodes). The previously mentioned _Process Plan Editor_ provided by the MESS GUI is where, similarly to the schematic graph, the graph of a process plan can be created by selecting the available operations and connecting them with arrows to form precedence constraints. The process plan for this use-case scenario is shown in Figure 11. Additional information is available for every node derived from the common service model by clicking the info button, as shown in the blue box. The created plan can be executed and its status can be tracked continuously on the _Process Manager_ tab of the MESS GUI. The status of the execution can be visualized by the coloring of each individual task based on their own statuses. This is a quick and easy to understand approach to report on the overall status of the process. The coloring is the following: (i.) grey displays the task is waiting for start signal, (ii.) yellow means the task is under execution; meanwhile, (iii.) the green indicates that the task is finished and (iv.) the red color represents the error status. Except for the error status, the other three can be observed in Figure 12. The communication which reports on the shown status change is visible inside the box in the middle of the figure. The message contains the most necessary data to update the information model of the system: type of the message, process identifier,