In recent years, in the world of urban planning, much has been written about the Smart City concept, a source of much controversy. Today, the emerging consensus of opinion seems to be that there is no single definition of it: in a way, it is also tempting to say that there are almost as many models as there are towns and cities. As indicated by Carlo Ratti, the architect, another finding is that no link has been established between the Smart City concept and architecture, i.e. it is unlikely that we will witness the birth of an architectural model that would apply to almost all towns and cities. The concept is applicable to both new towns in South Korea and the ancient towns and cities of Europe. For some people, it is based, above all, on interaction with citizen residents, whereas for others it is a technological solution to the problem of managing oversized metropolitan areas. Yet, in spite of these differences of opinion, the concept relies on converging objectives and component parts. Among these, as emphasized by Antoine Picon in his interview1, what truly characterizes the Smart City is the quest for more effective use of information technologies, in whatever form. This quest may focus on a great variety of topics: mobility, housing, energy, sustainable development, urban administration, services to inhabitants and citizen participation, etc.
Highly intensive use of technology
The second point of convergence of all Smart Cities seems to be their highly intensive use of technology. Indeed, all smart cities feature a set of infrastructures that make up what could be described as a "digital base" made up of dense high-performance telecom networks, be they wired or free-to-air, including optical fibre networks, coaxial cables, ADSL, WI-Fi, bluetooth, mobile telephone networks, etc. These networks are many and their performance levels and technologies are continually changing. Among the other components of this base are sensors of all kinds, fixed or embedded, cameras and connected objects, all of which cover urban areas and take their pulse in real time by monitoring road traffic, air or sound pollution, security and safety, etc. These urban sensors are also continually changing and multiplying. Their flows interconnect and even clash, because their sources are becoming complex and sometimes compete with each other. Today, it is possible to measure urban traffic using the traditional method featuring sensors embedded in the asphalt, or cameras, or so-called connected vehicles, or the smartphones of vehicle drivers or their passengers. In a completely different area, we can measure, for example, flows of tourists using the geo-tracking function on our mobile phones. Sensors are massively spreading across the urban fabric, a trend which is only beginning. The first generation of fixed urban sensors , whose deployment was slow and expensive albeit planned, is now complemented or even rivalled by the new generations. Smartphones with their geo-tracking feature represented the first wave. The imminent arrival of a very large number of connected objects known more specifically as the "Internet of Things" (IoT) will be the second wave. Data are indeed the lifeblood of the Smart City, the third convergence. Whatever its shape and objectives, the Smart City is based on a continuous flow of data. These data may come in many different forms because they are complex, heterogeneous, unstructured and ever more voluminous, which explains why they are now called "big data". The exponential growth in sensor data combined with the increase in computing power is making it easier and easier to measure, analyze, anticipate and, in short, to model the ever more secret pace of the Smart City.
