## 2 Results and Discussion
### Scope of Application  
The natural area of application of this matrix would fit into what we call today \"Smart Cities\". Before moving forward, though, it is necessary to define what a Smart City is, especially since there are so many different definitions. A number of experts in this field have defined a Smart City as the following:  
* \"a city that uses information and communications technologies to make its critical infrastructure, its components and public services more interactive, efficient and visible to citizens\" [9];
* \"a digital platform on which a complex ecosystem of multiple agents (including administrations, companies and citizens) is developed, equipped with sensors and capable of offering, through the processing of all the information acquired by the sensor network, the best services possible at every moment\" [10];
* \"a city in which Information and Communication Technologies play a role in one or more sectors\" [11];
* \"investments in human and social capital and traditional (transport) and modern (ICT) communication infrastructure fuel sustainable economic growth and a high quality of life, with a wise management of natural resources, through participatory governance.\" [12];
* \"a common framework and to highlight the growing importance of Information and Communication Technologies (ICTs), social and environmental capital in profiling the competitiveness of cities\" [13].  
As can be seen in this small sample, the definitions are many and varied. This explains why, if we browse the vast majority of smart-city initiatives found online, we can find a great variety of charts and graphs (Figure 1) describing factors such as relationships, connectivity, sensing elements, interaction, and data centers. However, rarely does the role adopted by citizens or environmental impact appear on these graphs. Here are just a few examples:  
Figure 1: A few schemes of Smart Cities found online, in which people do not appear. **(a)** “Smart Cities Big Data Cycle” [14]; and **(b)** “Smart Cities: a System of Systems of Systems” [15].  
Increasingly, publications, companies and initiatives have begun to appear that incorporate people into their schemes of work (Figure 2). This is a hopeful development. We must see if just as mere users or if they really take into account their needs and how to meet them:  
As can be observed, there are several elements and different criteria in the definition of Smart Cities, as well in the graphic representation of a Smart City. Then, in searching for the definition of a Smart City we need to remember two things first:  
1. What is a city?  
* From antiquity, a place for exchange, both social and economic;
* At present, a system of systems that generates and promotes these relations and trading, but that occurs partly in real environments and partly in virtual spaces.
2. What is intelligence?
* The ability to understand and comprehend, for which it is first necessary to perceive;
* The ability to solve problems, based on memory and experience.  
Therefore, we can advance a more comprehensive definition of a Smart City as:  
_\"A space for coexistence among people who, based on the available technologies, can thrive and develop, while taking into account economic, social and environmental sustainability.\"_  
These technologies, in order to act intelligently, should have the ability to perceive (via sensors and cameras), store, and process data (using servers and data centres), and solve problems (programming and information for decision-making). This should all be done in an energy-efficient way that serves the people. Also crucial for smart cities is combining the cloud and the sensors, so that the sensing data can be stored or processed. However, it is expected that people must have a certain level of skill in order to understand and use these systems [18].  
Figure 2: In recent years, finally the citizen is on these schemes. (**a**) “Infrastructures, operations, people” [16]; and (**b**) “Smart Cities need smart citizens” [17].