Database Reference
In-Depth Information
Next, we move from individuals to interactions - links - among individuals,
and enter the domain of social network analysis. An extraordinary effort has
been devoted to understanding the interconnectedness of individuals, that is, the
structure of the social networks we inhabit, and how this structure influences
social phenomena, such as the importance of certain individuals or groups, the
diffusion of information, or the formation of communities. The second contri-
bution of this chapter is to provide a brief account of the key findings of network
science so far (what the distinctive features of real social networks compared
to random networks are, how the community structure of real networks mod-
els the fabric of society, what the mechanistic processes that generate realistic
networks are), to the purpose of discussing the recent results on how human
mobility shapes and impacts social relations, and the other way around. Again,
empirical laws were found that offer quantitative accounts of the intuition that
people from the same social circles tend to co-locate in space and time more
than people who are far apart in the social network. Building on this relation
among social and mobility variables, it is possible to shed more light on how
social networks (and mobile behavior) evolve over time.
We believe that the results surveyed in this chapter, about individual mobility
laws and the relations between social ties and mobility, should become basic
tools for research in various disciplines, and we envisage that the convergence of
data mining research and network science research, already apparent in some of
the works discussed here, will represent a strong trend in the near future aimed at
combining the analytical power of statistical physics and knowledge discovery.
15.1 Models of Human Mobility
We live in an era in which understanding individual mobility patterns is of
fundamental importance for epidemic preventions and urban and transportation
planning. Yet human movements are inherently massive, dynamical, and com-
plex. Indeed, on one hand, aided by modern transportation technologies, we can
now travel to any place on the globe in just a day or two. On the other hand,
while the mobility of our fellow species is mainly governed by mating needs
and food resources, human mobility is fundamentally driven by ourselves, from
job-imposed restrictions and family-related programs to involvement in routine
and social activities. Therefore, quantifying the regularities and singularities
behind human movements has remained an often elusive goal. Thanks to the
availability of large-scale data sets generated by various domains of modern
technologies, ranging from registration of dollar bills to mobile phone services
and GPS devices to location-based websites, we have witnessed a proliferation
of studies on human mobility.
In this section, we will start from the most fundamental models for motions,
dating back to the nineteenth century. We will then describe several empirical
