The Open Definition
"The Open Definition, created in 2005, is the main international standard for open data and open data licences, providing principles and guidance for all things “open”. In essence: Open data is data that can be freely used, shared and built on by anyone, anywhere, for any purpose. The “standard” provided by the Open Definition – common requirements that must be met if a data is to be called “open” – is crucial because much of the value of open data lies in the ease with which different sources of open data can be combined – practically every app or insight made with data requires combining several pieces of data. For example, you need to know the bus timetable and have a map showing bus stops to be able to reach your destination on time.
The Open Definition prevents this fragmentation – and resulting destruction in value – by ensuring a common standard for all “open” data. Evidence for the practical success of the effort can be found in the reuse of the definition key principles and language in other important areas including UK and US government policy, and include the transition in terminology from “public sector information” to “open government data”.
The expert-governed licence conformance process and recommendations for conformance have strengthened licences around the world, for example, in the revision of the UK Government’s internationally influential “Open Government Licence”.
The Open Definition has also influenced and steered other communities of practice in the open movement, including open access to publicly-funded research, open hardware, and more."