What is, exactly, Public Data? A definition that is accepted almost implicitly is  "data that is of  
public interest, that belongs to the whole community, data that every citizen is surely entitled to  
know and use" . This definition is so generic that accepting it together with the assumption that all  
such data should be open as preached by the Open Data movement (online, as soon as possible, in  
machine  readable  format  with  an  open license  etc...)  doesn't  create  any  particular  problem  or 
conflict. 
Real problems however start as it has happened all too often so far, whenever we assume more or  
less consciously that "Public Data" in the sense defined above and data directly produced by  
Governments  and  Public  Administrations,  that  is  what's  normally  called  PSI  (Public  Sector 
Information) are the same thing. 
There is no doubt that Governments and Public Administrations produce huge quantities of Public  
Data. But this is an age of privatization of many public services, from transportation to healthcare,  
energy and water management. This is an age in which many activities with potentially very serious  
impacts on whole communities, like processing of hazardous substances or toxic waste, happen  
outside Public Administrations. The paradox is that, as Sasaki put it , this increased privatization is  
happening in the very same period in which " we are observing a worldwide diffusion of access to  
information laws that empower citizens to hold government agencies accountable." 
In such a context, "Public Data"is critical just because it is a much bigger set of data than what  
constitutes traditional, official PSI. "Public Data" includes all that information plus the much bigger 
amount  of  data  describing  and  measuring  all  the  activities  of  private  companies,  from  bus 
timetables  to  packaged  food  ingredients,  aqueducts  performances  and  composition  of  fumes 
released in the atmosphere, that have a direct impact on the health and rights of all citizens of the  
communities affected by the activities of those companies. 
Are such data "Public" today, in the sense defined at the beginning of this paragraph, that is  
something every citizen has the right to know without intermediaries or delegates, or not? Should  
they be public? If yes, shouldn't law mandate that all such data be Open (that is, published online as  
soon as possible, in machine readable format with an open license etc...) just like, for example, the  
budget of some Ministry? Answering these questions may be one of the biggest challenges for the  
Open Data community, and for society as a whole, in the next years. 
Here are, in order to facilitate reflection on this issue, a few recent, real world examples of "Public  
Data" that are not PSI, and of the impacts of their lack of openness. 
24/34
Copyright  2011 LEM, Scuola Superiore Sant'Anna. This work is released under a Creative Commons attribution license (http://creativecommons.org/licenses/by/3.0/)