  We present a research roadmap of a Planetary Nervous System (PNS), capable of
sensing and mining the digital breadcrumbs of human activities and unveiling
the knowledge hidden in the big data for addressing the big questions about
social complexity. We envision the PNS as a globally distributed,
self-organizing, techno-social system for answering analytical questions about
the status of world-wide society, based on three pillars: social sensing,
social mining, and the idea of trust networks and privacy-aware social mining.
We discuss the ingredients of a science and a technology necessary to build the
PNS upon the three mentioned pillars, beyond the limitations of their
respective state-of-art. Social sensing is aimed at developing better methods
for harvesting the big data from the techno-social ecosystem and make them
available for mining, learning and analysis at a properly high abstraction
level.Social mining is the problem of discovering patterns and models of human
behaviour from the sensed data across the various social dimensions by data
mining, machine learning and social network analysis. Trusted networks and
privacy-aware social mining is aimed at creating a new deal around the
questions of privacy and data ownership empowering individual persons with full
awareness and control on own personal data, so that users may allow access and
use of their data for their own good and the common good. The PNS will provide
a goal-oriented knowledge discovery framework, made of technology and people,
able to configure itself to the aim of answering questions about the pulse of
global society. Given an analytical request, the PNS activates a process
composed by a variety of interconnected tasks exploiting the social sensing and
mining methods within the transparent ecosystem provided by the trusted
network.
