## 1 Introduction
### Definitions
#### 1.2.5 Cloud-Based CPPS  
The cloud-based concept has now some applications in different sectors such as agriculture, food processing, automotive industry, machinery and tool industry, semiconductor industry, environmental monitoring, and security surveillance, among others. The interest in integrating cloud resources into CPSs has increased in recent years, which reflects the emergence of new fields like Cloud Robotics, Sensor Clouds, and Vehicular Clouds [18]. Nowadays CPSs are implemented as small nodes incorporated in larger systems. These nodes have limited computing capabilities and low storage available, but almost always, they have some kind of network interface. With the rise of IoT and CC, several new perspectives have appeared for those CPSs, to extend their resources by taking advantage of cloud resources [18; 19]. In Industry 4.0, CPS is one of the main technologies and usually is connected through the Internet. Recently, the concept of cloud was applied to CPS resulting in cyber manufacturing. Using real-time connectivity on the connection between physical machines and by using CC, cyber manufacturing is capable of realizing true-sense CPS with multiple functions in one closed loop. Cloud-based cyber manufacturing can be described as an integrated CPS that can provide on-demand manufacturing services, digitally or physically using efficient manufacturing resources distributed across several locations [13]. According to [PERSON] et al. [18], there are three core requirements for cloud-based CPS: offloading intensive computation; storing and analyzing large amounts of data; and seamless access through virtual interfaces. Knowing these requirements, CC represents a possible suitable solution since it addresses all of these three challenges. When CPS is used with a high-bandwidth connection, CC can provide both storage and computing resources to back-end CPS and allows easier integration of CPS by virtualizing access to them through Web Services Interfaces. A cloud-based CPPS is, in fact, an extension of a CPS: it includes a flexible stack of CC services taking advantage of the computing power, storage, and software services in a scalable and cost-effective way. Cloud-based CPPS can support and improve manufacturing processes since it provides new capabilities for data collection, storage, analysis, and transmission. Figure 5 shows a comparison of conventional, web-based, and cloud-based robot cells. In a conventional robot cell, the application and service modules, control system, and physical components are locally integrated. Also, in this integration, all the data and knowledge remain. In a web-based robot cell, the physical system is independent of the control system and is operated remotely over the network. Information, services, and control are deployed in remote servers. This approach has some technical drawbacks since some issues can arise, such as difficult synchronizations, loss of real-time control, and/or stability risks. A hybrid solution is proposed with the cloud-based robot cell that balances the need for heavy computing and real-time local control. Data sharing, processing, and analyses can be performed remotely in the cloud, and physical applications can be created and maintained in virtual cloud services [20]. Some works with the use of cloud-based systems in conjunction with manufacturing challenges such as increasing product quality and decreasing production costs can be found in the literature. Some examples are as follows:  
* [PERSON] et al. in 2014 suggested a PaaS approach for reconfigurable product lines based on cloud robotic applications. With this approach, end-users do not need to worry about low-level decisions when a line is reconfigured since the configuration of the robot is managed at a different level on the distributed system to the robot level in the cloud level [21];
* [PERSON] et al.