IoT reference architecture

In this chapter we present our IoT Reference Architecture. This IoT Reference Architecture is, among others, designed as a reference for the generation of compliant IoT concrete architectures that are tailored to one's specific needs. For other usages of the IoT Architectural Reference Model see Chap. 3. The IoT Reference Architecture is kept rather abstract in order to enable many, potentially different, IoT architectures. Guidance on how to use all the parts of the IoT Reference Architecture can be found in Chaps. 5, 6, 9, 10, and 11. Both in devising this chapter and in presenting the outcomes of our deliberations, we are adhering to the framework of architectural views and perspectives, as described in the software engineering literature and standards (for more details see (Rozanski and Woods 2011)). The use of well-known concepts makes it easier for architects from other domains to feel comfortable in the IoT world and this framework was thus a rather natural choice. To be more precise, we used the definitions of views from (Woods 2008), as well as then architectural-perspective catalogue. We adopted both according to IoT-specific needs. One has to be careful though, about the definition of views and viewpoints as these differ between authors. Nonetheless, there are no conceptual differences to traditional approaches and someone with a background in designing any kind of system should not have a steep learning curve. Notice though that architectural views and perspectives were originally defined for concrete architectures and not for reference architectures. Views that are very use-case dependent, for instance the IoT Physical Entity view and the context view, are therefore not covered here. For a more detailed discussion of this aspect see Chap. 5. Furthermore, since a reference architecture covers a wide range of use cases, it is of course void of use-case-specific details (for instance usage patterns and the related interactions of the system's functional components), such aspects are not covered in the IoT Reference Architecture but have to be attended during, for instance, the architecture-generation process. The structure of the chapter is as follows: First, we give a short overview on architectural views and perspectives. We then go on with presenting views that constitute the IoT Reference Architecture. The functional view and its viewpoints are described in great detail. At the time of writing there was indeed so much information at hand that we decided to only present an overview of the functional view here and to cover, for instance, the detailed definitions of the functional components of the functional-decomposition viewpoint in Carrez et al. (2013). Next, the information view is introduced as well as the deployment and operational view. The remainder of the chapter is then devoted to architectural perspectives. We describe four architectural perspectives (evolution and interoperability; performance and scalability; trust, security, and privacy; and availability and resilience). How architectural perspectives influence the architecting process is not covered here but in Chap. 6.