Persistent identifiers: DOI
Persistent identifiers ensure that online references remain accessible in the future. The Digital Object Identifier, DOI, can be assigned to digital objects, such as data or publications. By using the DOI you can make sustainable citations of and references to digital sources.
Online resources can generally be accessed by making use of a web address or a URL. Such web addresses may change, however, for a number of different reasons. The name of a server may change, web resources may be migrated to different systems, or the filenames of objects can change. When URLs of objects change, the original references to these objects often cease to function correctly. As has been shown in a number of studies, such as 'The decay and failures of web references', more than half of the online resources used as references in academic publications can no longer be accessed after a period of nine years.
The problem that URLs do not offer permanent access to resources can be addressed relatively easily by making use of persistent identifiers (PIDs). They are permanent codes which can continue to refer to online resources, even when their URLs change. A PID is managed by an organisation that links a persistent identification code with the most recent URL. This association is updated whenever the URL changes. Different PID systems are currently in use. Well-known examples include the Handle, URN/NBN and the DOI.
Academic journals often assign DOIs to publications. DOIs are used increasingly by repositories, to refer to objects and to metadata. DOI has been an ISO standard since 2012. In the Netherlands, DOIs are managed by DataCite Netherlands.