This Persistent Identifier reference website has been created in cooperation with the Dutch partners of the parties – PersID, DataCite and EPIC – that support the use of PIDs as well as the PID users Meertens Institute, Digital Heritage Netherlands, and CATCHPlus. The purpose of this website is to provide information for data managers who need to implement persistent identifiers for the purpose of their research or cultural heritage communities.

Some of the information provided is based on the JISC repository net factsheet “Persistent Identifiers“ (used with permission).

What is a Persistent Identifier (PI)?

A Persistent Identifier is a permanent and unique label assigned to a digital object – a text document, audiovisual file, database, etc. – independently of where it is stored. The unique label is registered at an agreed location. The unique label ensures that the object can always be found on the Internet, even if the name of the object or its storage location changes. The object can therefore always be located and referred to unambiguously.

Why is a PI important?

In the context of the Internet, we consider the URL to be the identifier of a digital object. However, we are all familiar with broken or dead links that point to web pages that are permanently unavailable. An URL (Uniform Resource Locator) may change in the course of time due to server migrations and other technical reasons, with unwanted consequences for links and citations within scholarly communication. A “persistent identifier” is therefore needed with which a digital object is permanently associated. This persistent identification number always refers to the digital object to which it has been assigned, regardless of the underlying locator technology or protocol used to access it (at the moment these are web addresses; in the future, however, an object’s location may be completely different).

How does a Persistent Identifier work?

The PI can be compared to the International Standard Book Number (ISBN), a unique numerical code allocated to a particular edition of a work. There are international agreements as to how ISBNs must be allocated and by whom, and a central record is kept of which number belongs to which work.

When an object receives a Persistent Identifier, the PI number and details of the object are recorded centrally. The location of the object is also registered. As soon as there is a change in the name or location, the central record is updated by adding a reference to the new location. The PI therefore always refers to the most recent location of the object.

An important aspect of persistence is organisational policy, not just the adoption of technical solutions. In essence, the persistence of an object is only effective if the organisation maintains and manages that persistence. In this way, even an URL can be considered persistent as long as it is maintained by some administrative service.

Advantages for the end user

The system means that the end user is always able to find digital objects that have been allocated a Persistent Identifier, even if the name or storage location have changed. This prevents dead links and means that references remain valid.

The PI can be compared to the International Standard Book Number (ISBN), a unique numerical commercial book identifier developed in the world of paper publishing. Each edition and variation (except for reprints) of a book is given an ISBN.

Advantages for the data manager

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Funding organisations demand permanent access

The European Commission and organisations that fund research – for example the Wellcome Trust, NWO, OCW and DFG – demand that the digital objects concerned should be permanently accessible. This means that the pointer to the digital object should remain valid over time, and the digital object remain readable or reachable over time. Alliances such as the Alliance for Permanent Access are being founded, creating awareness of the demand for Permanent Access. Permanent access requires open standards and a reliable governance structure. Permanent access policies also demand that each participant in this chain should take on a specific responsibility. Persistent Identifiers can be branded as “very reliable”; only accredited organisations with long-term preservation strategies for their digital objects are allowed to create Persistent Identifiers.

Accessibility

Persistent Identifiers are mainly used for objects that are stored in institutional repositories. They link up the material found by search engines and access to that material in repositories. The search results consist of metadata, which can contain an Identifier that refers to the location of the object at the point when the search takes place.

Enhanced resource management

Identifiers can be used to model complex relationships between resources and make it possible to manage compound resources and distributed copies of a resource, to distinguish between different versions of a resource, and to help decide which is the most appropriate copy or version for a user.

Rights management

Identifiers can be used to associate rights information with resources. They can also be used to track the relationship between a resource and derived works.

Most common Identifier systems in the Netherlands

Persistent Identifiers include ARK, DOI, Handle, ISBN, ISSN, PURL, URI, URL, and URN. A complete list can be found at http://repinf.pbworks.com/Persistent-identifiers.

The identifier systems that are used most frequently in the Netherlands are listed below. They are managed by separate organisations that have Dutch partners.

Literature