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Persistent Identifiers

Information on the internet can easily get lost, for example when files change name or are stored at a different location. So-called persistent identifiers can be used to minimize this risk of information loss. DANS is involved in the design and implementation of an infrastructure that makes use of persistent identifiers. In this development, DANS cooperates with organizations like SURF and the National Library of The Netherlands (Koninklijke Bibliotheek - KB).

 
Frequently Asked Questions (FAQ)
 
1.      What is a persistent identifier?
A persistent identifier is a unique code that is linked to a digital object, such as a publication in PDF format. This unique code identifies the object and makes it possible to locate it (via a so-called resolver), also when the object is moved to a different location.

2.      What is a resolver?
A resolver is a system that creates the link between a persistent identifier and the current location of the associated object. It is somewhat comparable to the way in which telephone numbers are linked to handsets. The resolver ensures that the phone number stays with the person, for example after moving house or after the purchase of a new mobile telephone. In conjunction with SURF, DANS has set up such a resolver.

3.       What type of object can I couple a persistent identifier with?
A persistent identifier can be associated with any digital object. This may be a complete e-book, but also an individual chapter or even every individual sentence in the book. The type of application determines the choice for the scale at which persistent identifiers are linked to digital objects. Condition for creating such a durable link is that both object and the party that manages that object are durable:

  • The object should not undergo any changes; a change will result in a new object with a new persistent identifier. The older object must also be maintained.
  • The organization has a realistic objective of long-term commitment to these objects and will update the resolver when an object changes location.

4.      How can I link a persistent identifier to an object?

  • Step 1. Determine which digital object of parts of an object should have a unique, durable code. How can this object or its parts be accessed? How will changes to these objects be dealt with? How many objects of parts of objects are there in total?
  • Step 2. Determine how and why your organization wants to and should have a long-term commitment to these objects.
  • Step 3. Contact DANS to discuss these issues and request your own so-called namespace. This namespace is the start of your persistent identifiers and guarantees that your persistent identifiers will differ from those of other organizations.
  • Step 4. Put an OAI-PMH interface in place and ensure that you implement the SURFshare standards for its use; see http://purl.org/REP/standards/.

5.      Which tools are available for linking persistent identifiers to objects?
Assigning and updating persistent identifiers for your objects can be done in your own system. You can then make these data available to the resolver via an OAI-PMH interface as defined within SURFshare http://purl.org/REP/standards/
 
6.      Where can I find more information about persistent identifiers?
The resolver is accessible at http://www.persistentidentifier.nl. For Dutch scientific institutions, more information regarding persistent identifiers can soon be found at http://info.persistent-identifier.nl. General information about persistent identifiers is available on the Web, for example at: http://www.ariadne.ac.uk/issue56/tonkin/
 
7.      What are the costs associated with the use and application of persistent identifiers?
Registration and support are free. For the time being, limited use by scientific organizations is still free.
 
8.      Will objects linked to persistent identifiers remain accessible forever?
DANS guarantees long-term access to the resolver. Support is guaranteed for the next few years. Structural means are available for maintenance and technical support of the resolver. DANS will provide a reliable successor in the event that this support becomes threatened. As owner of an object, you will be responsible for keeping this object accessible and updating the resolver when the object’s location changes.
 
9.      What can DANS do for me if I want to use persistent identifiers?
DANS has set up a durable infrastructure for assigning persistent identifiers to digital objects that are important for scientific research. Access to this infrastructure is free of charge.

10.  Where can get more information about persistent identifiers?
Send an e mail to maarten.hoogerwerf at dans.knaw.nl.
The web site http://info.persistent-identifier.nl will soon have more background information.