# Cyber-Physical-Social Frameworks for Urban Big Data Systems: A Survey
## 2 Background of Cyber-Physical-Social Systems  
Figure 2 shows the development of the CPSS paradigm, depicting the relevant background concepts and technological disciplines on which it is based. Moving from the bottom to the top of the inverted triangle in the figure represents increased levels of abstraction and increasing data volume. Studies on CPS development [44; 48] trace the beginning of its evolution to mechatronic systems [49], which combine the disciplines of mechanical, control and electrical engineering in industrial processes. Examples of mechatronic systems include drive train and vehicle vibration analysis study [50]. In terms of abstraction, at this level, the design processes are well-defined and support the translation of the designed procedures into the physical systems [44]. In embedded systems, the focus is on the computational system embedded within a physical system (where the execution of the code takes place), example being a thermostat. CPS frameworks, which are designated to be successors of embedded systems [34], integrate computing with communication technology, together with control methodology. CPS are typically concerned with the sensing and control of physical phenomena through networks of interconnected devices to achieve defined goals. The field, which started from an engineering perspective, deals with the control and monitoring of physical environments through a tightly coupled distributed system of sensors and actuators [7]. Such systems have been geared towards disseminating the data sensed by mobile CPS with minimal delay to provide real-time services [51]. Examples of CPS implementation include adaptive air ventilation systems [52] and the MediaCup [53], which detects the temperature of the contents and warns users if it is too hot. In terms of abstraction and the relationship between the physical and cyber parts, it is defined by function [44]. The concept of IoT is closely linked with that of CPS in recent studies, with disparate views on the similarities and distinctions between the two concepts. Some studies [46] assert that while CPS focus on bridging the physical and cyber worlds, IoT is concerned with the unique identification of heterogeneous devices and smart objects and their connectivity to the Internet. Some authors [4] state that while there are similarities between CPS and IoT, i.e., device cooperation to reach defined goals, IoT has a horizontal view comprised of hardware components interacting with each other, whereas CPS takes a vertical approach encompassing networked hardware, computational processes and control mechanisms. Other studies [45], while acknowledging the difference in system architectures of CPS and IoT, refer to them interchangeably. An increased level of abstraction in IoT is attributed to a large number of undefined factors, which are known only in terms of contribution to the system operation [44]. Figure 2: Evolution of CPSS. In contrast to classical CPS, recent studies have recognized the importance and possibility of human-in-the-loop (HiTL) CPS which involve control loops with humans interacting as inherent actors in it. Such HiTL systems are mainly individual-centric in that the focus is to learn the human state, including physical, emotional and physiological condition, through brain-computer systems, enabling adaptability to human needs. In such systems, \"humans need to be instrumented and be an integral part of the system\" [46], which is recognized as infeasible and undesirable in urban computing scenarios [46]. HiTL systems have applications in areas such as assisted living, brain-computer systems and factory settings with a human in the control center. Studies surveying HiTL systems include a survey of the field by [PERSON] et al. [7], and by [PERSON] et al. for medical CPS [54]. Finally, CPSS integrate the various data originating from the physical, cyber and social spaces through fusion techniques to provide human-understandable abstractions and inferences.