There's a lot of talk about open data right now, with governments and international institutions releasing datasets large and small as open data. Charities and media outlets have also been getting involved, publishing data and making use of open datasets in planning or reporting.

A lot of organisations put data on their websites, or make data public in documents and reports regularly. So what is special about open data?

Most definitions of open data focus on three elements, asking, is the data:

Accessible - can it be easily and freely accessed (i.e. without payment, and through channels such as the Internet);

Machine readable - published in standard computer formats that allow anyone to load up the data, manipulate and explore it - without needing expensive or proprietary software, or having to manually copy tables of data into more flexible formats.

Re-useable - shared under licences (or placed into the public domain) to allow the data to be combined, explored and re-used in commercial and non-commercial ways.

World Wide Web inventor Tim Berners-Lee has been a strong advocate of open data, and there are a growing number of development sector datasets available.

Image Credit: Melanie Chernoff.