Open data is defined as structured data that is machine-readable, freely shared, used and built on without restrictions.

The key things to remember about open data are:

• #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.
• #Re-use and redistribution#: the data must be provided under terms that permit re-use and redistribution including the intermixing with other datasets.
• #Universal participation#: everyone must be able to use, re-use and redistribute. There should be no discrimination against fields of endeavour or against persons or groups. For example, 'non-commercial' restrictions that would prevent 'commercial' use, or restrictions of use for certain purposes (e.g. only in education), are not allowed.