# A Methodology for the Design of Application-Specific Cyber-Physical Social Sensing Co-Simulators
## 1 Introduction  
Cyber-Physical Social Sensing (CPSS) systems [1] are ubiquitous mobile wireless sensor networks where intelligent terminals equipped with various sensors are integrated. These terminals perceive human social information such as the environment or the social activities. CPSS include also a central server where the information is uploaded and from which users are provided with data services (see Figure 1). The final objective of CPSS is to enrich human-to-human, human-to-object, and object-to-object interactions in the physical world, human society, as well as in the virtual world [1]. As can be deducted from the previous description, CPSS are intrinsically concurrent. Various domains (such as the social, physical or cyber) coexist in time, evolve together and influence each other [2] (see Figure 1). In CPSS, the social world includes all people sharing the same space (as large as wanted) and time, including their individual and group physical and physiological state and all human-to-human interactions among the habitants (affective or physical) [3, 4]. Many specialized works on sociology and group psychology have studied these issues [5, 6, 7, 8]. The physical world includes all physical phenomena and third-party devices and objects which are relevant to the CPSS operation [9]. The physical world also includes all the processes and object-to-object interactions developed by the elements which compose it. The temperature evolution in closed rooms [10], or the traditional industrial systems [11], belong to the physical world. The impact of the physical world in the social world has been exhaustively studied in the context of the so-called social environment [12; 13; 14; 15], but always from a narrative point of view (never with practical applications). Finally, the cyber world includes all the intelligent terminals [16], sensors and mobile wireless networks used to sense the social information. The relation between the cyber world and the physical world is probably the most studied. The term cyber-physical systems (CPS) [17] (which refers to the intersection of the physical and cyber worlds) is nowadays one of the most popular terms in research. On the other hand, the field of social sensing [18] (the union of the cyber and social worlds) are also turning more important day by day (with concepts such as the Social Internet-of-Things [18; 19]), although it continues to be less popular than CPS. The novelty of CPSS, then, is to consider the three subsystems (sometimes together with other domains such as the mental world [20]) evolving together, formalizing some ideas which have started to appear very recently (such as the union of CPS and social sensing) [21]. Table 1 summarizes the relations among the different subsystems as described above. Figure 1: Cyber-Physical Social Sensing (CPSS) scheme. As a current technological paradigm, CPSS present some common characteristics with other recent proposals such as the Internet-of-Things (IoT). However, while IoT solutions are focused on the global interconnection of \"things\" (daily living objects provided with embedded computers), CPSS are primary designed to perceive human social information including the environment, transportation and social activities [22]. In both cases, a heterogeneous hardware platform with a high density of devices is considered. Nevertheless, IoT systems consider people as users and things as the main element in the systems, while in CPSS the human factor is the basic information source and sensors (usually integrated into intelligent devices) are only the medium through which obtain that information. Technically, CPSS may be understood as an extension of IoT systems, were human factors are combined with traditional devices. As an evolution of Cyber-Physical Systems [23], CPSS use to define feedback control loops, where social information is processed and returned to social world in order to generate a certain effect. On the other hand, IoT services do not have restrictions and may be based on the simple data acquisition.