Open data is the idea that certain data should be freely available to everyone to use and republish as they wish, without restrictions from copyright, patents or other mechanisms of control [Auer, 2007].
The goals of the open data movement are similar to those of other "Open" movements such as open source, open hardware, open content, and open access. When data can be freely accessed, used, modified and shared for any purpose and by anyone, the term Open Data is appropriate.
In particular, the Open Knowledge Foundation principles, called Open Definition, can be taken into account. The key features of openness are briefly summarized as follows:
Availability and access: the data must be available as a whole and at no more than a reasonable reproduction cost, preferably by downloading over the internet. The data must also be available in a convenient and modifiable form
Reuse and redistribution: the data must be provided under terms that permit reuse and redistribution including the intermixing with other datasets. The data must be machine-readable
Universal participation: everyone must be able to use, reuse and redistribute — there should be no discrimination against fields of endeavour or against persons or groups
Open Data implies data from all possible areas, not just Open Government Data. The directive on public access to environmental information, which states that “[i]ncreased public access to environmental information and the dissemination of such information contribute to a greater awareness of environmental matters, a free exchange of views, more effective participation by the public in environmental decision-making and, eventually, to a better environment”.