Open data is the concept that there should be some data that is freely and openly available to the entire public to access, use and share, as long as it doesn't contravene national security or privacy concerns.

In order to be truly open, a dataset needs to be clearly licensed as open to use and share - legally open - as well as technically open, in that it is easily machine readable and available in bulk. Open datasets tend to be available for free, or at a nominal charge.

The UK has long been at the forefront of the Open data movement through government initiatives like and organisations like the Open Data Institute.

Any individual or organisation can open their data up via an open license, from governments to universities to corporations. Data science competitions on the site Kaggle are reliant on organisations like the US Department of Homeland Security opening up their data for its community to work on.

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Closed data is only available to people within organisations, such as proprietary business information, data related to national security and your mobile phone usage data, for example.

Open data in action

One example of the benefits of open data is the case of popular mobile app Citymapper. The London-based startup used a whole range of recently open-sourced data sets from Transport for London (TfL) back in 2011 to power its free mobile app, providing a public service by giving users real time routing information around London, and now more cities.

Read next: London’s Citymapper capitalises on “decade of data”

The National Health Service (NHS) is an active proponent of open data, "to improve the quality of care, lower healthcare costs, and facilitate patient choice."

"This allows us to shine a light on the variation and unacceptable practice and bring about a revolution in transparency and support patients and citizens to actively participate in the design and quality of their local health services."

Read next: How NHS Digital is using data science to cut down on A&E visits

The possibilities of innovative companies or individuals doing the same with health data, to spot the early onset of disease, for example, or with financial data to help users manage their money better, are just two examples of where open data could benefit the public as information becomes more freely available.

Open Data today

Globally, the G8 committed to an Open Data Charter back in 2013, and the USA increasingly committed to the policy under the Obama administration with the Open Government Initiative. Open data is key to a growing appetite for governments to increase transparency levels when engaging with the public.

For example, the Digital Accountability and Transparency Act (DATA) of 2014 comes into full effect in the USA in 2017, imposing requirements on federal agencies to report on their spending in an open way.

Joel Gurin, president and founder at the Center for Open Data Enterprise in the USA believes there have been three waves in the lifecycle of Open Data since being popularised in 2010.

Speaking to Techworld, he explained: "I think Open Data is alive and well and has gone from being a new concept to more and more mainstream.

The first wave was awareness in the importance of open data and transparency. Then from 2013 to the present there has been a continuation of that and applying that to business.

"The third wave will be institutionalising this," with Gurin pointing towards the G8 Open Data Charter and the DATA Act as key milestones in this third wave.

Gurin also sees the third wave as being characterised by greater adoption of Open Data by large corporations, not just smaller, innovative companies.

"We see more corporations using Open Data, combined with their proprietary data to deliver value," he said. "All kinds of companies are using census data to understand their customers, to target marketing to figure out where to build the next store, in a much more sophisticated way than five years ago," for example.

Privacy concerns

The benefits of open data are clear to see, but privacy concerns always loom over the subject. In 2011, one year after was released to the public, Cabinet Office minister Francis Maude said: "It is my intention that no personal data will be shared with any third party as part of this initiative."

Most Open Data is heavily anonymised to protect the privacy of citizens. However, as the Open Rights Group points out: "One of the key issues relate to anonymised personal data, such as census extracts, which in a controlled environment can be considered safe to a point, but which once it is placed online could be open to reidentification by combining it with other datasets."

Read next: Sir Tim Berners-Lee tells governments to follow UK open data strategy

However, Gurin argues the opposite is true. As he wrote in The Guardian in 2014: "Paradoxically, opening up this sensitive data, in a specific and controlled way, may actually make it more secure.

"The problem now is not only that government agencies and some businesses are collecting personal data about all of us; it's also that we as individuals don't know what's being collected and don't have access to the information about ourselves. If we knew more, we could control more."