# A Methodology for the Design of Application-Specific Cyber-Physical Social Sensing Co-Simulators
## 2 State of the Art
### Recent Proposals on CPSS  
CPSS is an acronym which may refer various proposals: from Cyber-Physical Social Sensing to Cyber-Physical Social Systems [36]. Furthermore, it is not clear if all these proposals refer to the same reality or present some differences [22]. However, in both cases, CPSS represents the deep integration of traditional technological systems (such as the Internet of Things or Cyber-Physical Systems) with human and social factors, such as people behavior, social opinions or the user mental world [20].  
In that way, there is not a unique manner to understand Cyber-Physical Social Sensing. Some works reviewing the different approaches may be found [37].  
Some proposals understand that, in CPSS, traditional sensors (present in IoT/CPS scenarios) are substituted by user surveys or user interfaces, which are displayed on mobile smart devices [24]. In that way, people opinion is sensed, creating a kind of collaborative of participative platform for relevant data sharing, in the same way as current social networks [38]. Historically, this approach is, probably, the first one to appear. With this view, systems to predict the bus arrivals [25] or to share information among people in the context of smart cities [39] have been reported. Even, in this kind of proposals, it is very necessary to design (and have been proposed) techniques to protect user personal information (as collaborative platforms require creating a user profile) [40]. Methodologies to design CPSS in an effective way have been also reported [41]. In relation to the promising Industry 4.0 paradigm [42], proposals about new manufacturing paradigms including social networks, social businesses and other similar technologies may be found [43].  
On the other hand, other works defend the proposal that CPSS are made of traditional sensors, but being able to stablish ad hoc connections in order to share relevant information with other nodes, as people do in social networks. Proposals related to social robots [26], social techniques for information dissemination in sensor networks [44], social ad hoc networks [45] and social routing protocols [46; 47] have been reported around this topic.  
Finally, some works describe CPSS, but deal with the problem of sensing the human behavior in a passive and non-intrusive way. It is probably the most recent and popular approach nowadays. In relation to Industry 4.0, the concept of social sensor has been proposed [48]. It consists of a virtual entity acquiring information and statistics in a proactive way from the applications and sensors in the user smartphones. Moreover, works about privacy protection, in order to anonymize the acquired data from users are also common [49; 50]. Sampling algorithms in order to collect information from users in an unobtrusive way have been also proposed [51]. Frameworks and architectures focused on collecting and processing information about human behavior [27; 28] may be also found. Service composition techniques [36], efficient wireless data transmission [52], etc., for CPSS following this last approach have been also investigated.