## 1 Introduction  
The Internet of Things is probably one of the most challenging and disruptive concepts raised in recent years [1; 2]. It pushes systems designers to address complex aspects that are recurrent in these solutions, for instance, the heterogeneity of devices and communication interfaces that are present in the working environment, the devices' mobility and computing capability, and the interoperability of data and services. Usually a device participating in an IoT-based solution (e.g., a surveillance video-camera) could also be part of more than one solution. For instance, it can assist the security system and also the automatic fire detection systems. Although this multi-role participation of devices is highly recommended, it increases the challenges for designing IoT-based solutions. Several researchers have highlighted the need to find an agreement on the IoT concept and provide guidelines and tools to help address the design of these solutions [3]. In that sense, some reference architectures have been proposed to structure these solutions [4; 5], and also some general design guidelines have been presented [6]. However, there is no clear approach to modeling the interactions among the participating devices, allowing designers to evaluate the system behavior before implementing it. Therefore, developers must conceive their solutions using only their expertise. This design approach is risky since the IoT-based systems belong to a new development area where not much expertise has been accumulated and shared. If the system being modelled has to support a critical activity, such as military operations or emergency responses, the designers must know and inform the limitations of the solution. A late detection of these limitations (e.g., while the system is being used in a real scenario) could produce serious drawbacks to the process supported by the application. Dealing with that challenge, this paper proposes a modeling approach that uses a human-centric wireless sensor network (HWSN) [4] not only to design IoT-based systems, but also to identify their potential limitations before implementing them. This approach allows designers to assign a basic role to the components participating in an IoT-based solution and characterize the communication links between them. Thus, it is possible to evaluate, at the design time, the information generation and flow through the whole system. Designers can choose to address or assume the system limitations, but it will always be made in an informed way. This modeling approach supports the evolving development of systems designs, allowing the implementation to be done once most system behavior has been already verified. The use of this approach should contribute to reducing development risks and costs. This proposal does not address the system implementation, but it allows considering the features of the devices and communication links used to implement the solution. Therefore, we can consider this modeling approach as complimentary to the existing solutions for implementing IoT-based systems. Particularly, the nodes features and capabilities, and also the interaction protocols among them, can be set during the pre-design phase; _i.e._, when the designer defines the types of nodes and links that will be present in the new system model. Transversal design aspects, such as information security and privacy, are not formally considered in these models. However, these aspects can be addressed as capabilities related to the roles played by the participating nodes, as suggested by [PERSON] _et al_. [7]. An interesting component that helps deal with information trustworthiness, security and privacy in these networks is the nodes position, as indicated in [PERSON] _et al_. [8] and [PERSON] _et al_. [9]. Nodes' reputation [10] can also be used to address information trustworthiness and data fusion.