## 7 Smart City Modeling: Related Work  
This manuscript has offered a UAN modeling and evaluation framework. In this section we review literature work in two main areas relevant to this manuscript: (i) Smart City conceptual modeling; and (ii) technical ICT Smart City component modeling.  
Several works have attempted to model the Smart City concept from a comprehensive perspective [57, 58, 12, 59]. Authors in [12] identify the following eight elementary components which represent a smart city framework: management and organization, technology, governance, policy context, people and communities, economy, built infrastructure, and natural environment. Other researchers state that there exist six Smart City dimensions agreed by the scholar community, namely: people, government, economy, mobility, environment and living [57]. Another work defines that a cityis _smart_ when investment in human and social capital, transport and ICT infrastructure produces economic and life quality benefits, while making an efficient use of resources and involving citizen participation in the city government [59]. A recent work introduces the Sensing as a Service (SaaS) model for the Smart City, highlighting the convergence of the IoT and Smart City spaces, while recognizing the aforementioned six Smart City dimensions [34]. Authors in [13] provide a methodology based on the definition of use cases, which can be expanded by so called integration profiles, which provides a systematic way to model the elements involved in a Smart City and their interactions. For example, the UAN model described in our paper could be structured following a similar approach.  
Regarding the technical ICT components that enable the Smart City, generic architectures for supporting heterogeneous Smart City applications have been devised [3, 7, 60]. Such architectures comprise sensor/actuator networks, connectivity means, big data processing and storage platforms, as well as application interfaces. Focusing on the sensor/actuator subsystem, researchers have aimed attention at how sensing technology is applied to enable various Smart City applications [6], as well as on networking aspects, such as the requirements for routing in low-power and lossy networks in urban environments, although the different approaches that emanate from different UAN classes have not been considered [4]. Several works present the development of and/or provide experimental results from Smart City testbeds and pilot projects in various cities such as Santander, Padova, Barcelona, Beijing and Oulu [3, 5, 8, 9, 10, 11]. Remarkably, the architecture of the 20,000-IoT-device test facility developed in the SmartSantander EU project is described in [3]. A more recent work introduces the IoT-based Smart City architecture deployed in Padova [5]. The main focus in these works is demonstrating the feasibility of Smart City concepts by means of sensor network deployments.  
We conclude from the literature review that while significant efforts have been devoted to modeling the Smart City from a conceptual point of view, and even though technical descriptions of the ICT infrastructure that supports Smart Cities exist as well, to our best knowledge, a comprehensive UAN model and evaluation such as the one presented in this paper has not been published as of the writing.