Europe's digital library Europeana has been described as the 'jewel in the crown' of the sprawling web estate of EU institutions.

It aggregates digitised books, paintings, photographs, recordings and films from over 2,200 contributing cultural heritage organisations across Europe - including major national bodies such as the British Library, the Louvre and the Rijksmuseum.

Today Europeana is opening up data about all 20 million of the items it holds under the CC0 rights waiver. This means that anyone can reuse the data for any purpose - whether using it to build applications to bring cultural content to new audiences in new ways, or analysing it to improve our understanding of Europe's cultural and intellectual history.

This is a coup d'etat for advocates of open cultural data. The data is being released after a grueling and unenviable internal negotiation process that has lasted over a year - involving countless meetings, workshops, and white papers presenting arguments and evidence for the benefits of openness.

Why does this matter? For one thing it will open the door for better discovery mechanisms for cultural content.

Currently information about digital images of, for example, Max Ernst's etchings, Kafka's manuscripts, Henry Fox Talbot's catotypes, or Etruscan sarcophagi is scattered across numerous institutions, organisations and companies. Getting an accurate overview of where to find (digitised) cultural artefacts by a given artist or on a given topic is often a non-trivial process.

To complicate things even further, many public institutions actively prohibit the redistribution of information in their catalogues (as they sell it to - or are locked into restrictive agreements with - third party companies). This means it is not easy to join the dots to see which items live where across multiple online and offline collections.

Opening up data about these items will enable more collaboration and innovation around the discovery process.

For example, imagine institutions started to contribute to shared pools of descriptive data, which the public could also update and add to (as per several successful experiments on Flickr Commons, Wikimedia Commons and the Open Library) - and which could be linked to relevant content from across the web. Today's release is an important step towards realising the Library of Congress's vision of world in which cultural data is "collaborative, decentralized, and international".

Or imagine the energy and imagination that currently goes into creating social discovery services for music or films (a la Spotify, Last.fm or Netflix) were applied to similar services for paintings or literary works ("if you liked X and Y, you might also like Z" or "you are within 5 miles of a Paolozzi sculpture you'll probably enjoy").

And think of how data about cultural artefacts could be used in teaching and research. Students and scholars could curate and interact with customised collections of content relevant to them, explore items using maps or timelines, or use the data to analyse relations of influence between authors and texts. (The DM2E project will soon be launching a series of scholarships to encourage innovative digital humanities projects building on the Europeana data - so if you're interested in this area, then watch this space.)

Europeana describe today's release as "by far the largest one-time dedication of cultural data to the public domain". Hopefully this will help to establish a precedent for other galleries, libraries, archives and museums to follow - which will in turn help to bring us that bit closer to a joined up digital commons of cultural content that everyone is free to use and enjoy.

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