# Industrial Cyber-Physical System Evolution Detection and Alert Generation
## 2 Use Case: Press Line Domain  
One of our partners designs and manufactures mechanical and hydraulic press machines, complete stamping systems, transfer presses, robotic lines, etc. Considering the manufacturing production lines designed and developed by our partner are based on press machines, we refer to them as press lines. The automotive world is a sector that is in constant movement and where technological developments require a continuous technological renovation. The Hot Stamping of Boron Steels is a recent creation technology that is settling in the sector and which the processes are in constant evolutions, changes, and improvements. For example, a hot forming manufacturing line for boron steels consists of 3 fundamental machines, each one tied to the other:  
* Destacker: It is the component responsible for (1) unstacking previously cut formats and (2) introducing the format in the furnace. * Furnace: Inside this component, the material remains for a minimal time until it reaches a completely austenitic structure and finally achieves a diffusion of the coating in the substrate. Currently, our partner used different furnace types: (I) Roller furnaces, (II) Multilevel furnaces, and (III) Furnace \"carousels\". * Press Machine: Once the format is heated, the press machine changes the shape of a workpiece with pressure. The main characteristic of this machine is that, unlike the trajectory that is necessary in the forming of cold steels, in the Hot Stamping, the press has to approach the mold as quickly as possible. Notice that different press lines exist. Depending on the customer's needs, the quantity and type of machines that constitute a press line are different, e.g., three different types of furnaces are used by our partner; thus, depending on customers needs, one or the other would be used. In turn, each machine within the press line is composed of different devices. These devices are also variable; they depend on customers needs, since the customer is the one who decides what to monitor inside the press lines, e.g., the temperature of the clutch break inside the press machine. In order to collect quantitative information in addition to getting information about their daily work, we conducted interviews with our industrial partner. For example, we realized that three different sizes of press machines can be used inside a press line: large, medium, and small (see Table 1). Though the number of devices is incremental to the size of the machine, the incidences (i.e., machine breakdowns) occurring per week are similar in all press machine sizes and are resolved in 1 to 2 days. Additionally, due to machine maintenance, retrofitting, etc., a press machine can evolve, i.e., new devices can be introduced or existing ones can be removed or replaced, and these changes affect between 40% and 59% of the machine. The data captured for each press machine varies, e.g., depending on installed devices. A customer decides what s/he wants to monitor, and the customers' requirements keep on evolving, resulting in several types of changes. Thus, the variability within a press machine exists, since depending on its purpose, the customer may decide what s/he wants to monitor. Therefore, in a press line, several machines can be found, each tied to one another. Each machine has a different objective, and therefore, the characteristics of each one are different. Additionally, note that each machine (e.g., press machine), as such, can be different (e.g., devices can be from different providers and the mechanism of the machine can be different). This implies that, in the same press line, variability exists. Therefore, each machine can evolve, since each machine is independent. This evolution is known as retrofitting. New requirements usually have an impact on the devices inside each machine, having to insert new devices (e.g., new elements of an industrial domain need to be