Pelagios 3 is a Linked Open Data initiative, in which independent online resources are linked together by annotating common references to places (currently ancient Greek and Rome, but soon to be expanded) as defined in a URI-based gazetteer. These annotations can then be aggregated either by member projects or third parties for a variety of purposes, including search, contextualisation and visualisation. Pelagios 3 encourages open access wherever possible although its only  requirements are that annotations conform to the Open Annotation  specification and use a URI-based gazetteer. Pelagios 3 also offers a demonstrator API for the purposes of facilitating interaction between projects but makes no claims regarding ownership or responsibility for the content of Pelagios 3 partner projects or the quality of annotations produced by them. Pelagios 3 is led by the University of Southampton, the Open University and the AIT Austrian Institute of Technology, but maintains a strong ethos of collaborative development and the development of specifications for ‘Pelagios-compliance’ and recommendations for Best Practice are usually developed in consultation with partners.

Pelagios cooperate in the framework of Tast 2.3 “Content harmonisation guidelines, including GIS and terminologies” in order to specifically in order to:

• contribute to a useful and seamless harmonization of data about places by aggregation, linking and annotation
• Exchange and elaborate best practices for networking and enhancing data value via LOD practices.
• explore ways in which to associate further resource
• maximise useful interaction among digital projects dealing with the ancient world
• activate a valuable network of specific projects to guarantee maximum quality.