Persistent Identifier

Identifiers for documents

In order to be able to reliably and permanently find, identify and cite physical, digital or abstract objects, designations have been developed that uniquely identify an object and remain the same even if, for example, the name of the object or its storage location changes. They are called "persistent identifiers".

In the field of Open Access publishing, two identifiers are important:

  • DOI: Digital Object Identifier
  • URN: Uniform Resource Name.

Note: Publications whose publication fees are to be reimbursed from the university's publication fund must have a DOI. Usually, it is assigned by the publisher or journal.

Documents published via the university's publication server OPUS are automatically assigned a URN.

Information: DOI

What is the DOI used for? How widespread is it?

A DOI is a unique identifier for physical, digital or abstract objects. In particular, it is used to identify electronic documents and link them to metadata.

The DOI is permanent: if, for example, the address (URL) of a document changes, the metadata is updated and the DOI remains valid.

DOIs are used worldwide to identify electronic publications and research data and have become an international standard for this type of document.

Who is behind the DOI system?

The leading institution in the application of the DOI system is the non-profit Internationale DOI Foundation (IDF). It is supported by DOI registration agencies whose task is to assign organisation numbers, maintain the technical infrastructure and manage the metadata of DOI publications.

An example of such an agency is DataCite e. V. As a member of DataCite, the Technische Informationsbibliothek (TIB) can act as an issuing agency for DOI names.

How does my publication get a DOI?

If you publish a document via a publisher - e.g. Springer Nature or Wiley - the publisher usually assigns a DOI to your publication (with the corresponding organisation number of the publisher).

Can Trier UAS assign a DOI?

No, not for the time being. It can only be assigned by members of the DOI agencies.

What does a DOI look like?

A DOI has the form: "10" + prefix (organisation number) + suffix (document number). As part of a URL web address, it can be used to call up the document or the associated provider information. Example:

  • 10.1007/BF01700692
  • ..ttps://
How to search with a DOI?

If you want to use a DOI to search for the corresponding publication, you can proceed as follows:

  •     Go to the DOI website and enter the DOI in the search bar (e.g. 10.1007/BF01700692).
  •     Enter the 'URL version' of the DOI in the address bar of your browser (e.g. ..ttps://

Depending on the accessibility of the publication, the search will lead you to the full text or to a page with metadata (e.g. to a publisher's page).

How do I specify a DOI when citing?

How the DOI is included in the bibliographic information of a publication depends on the citation system you have chosen. Two examples:

  • APA 7th (library guide): specification in URL form

    Deregowski, J. B., Muldrow, E. S. & Muldrow, W. F. (1972). Pictorial recognition in a remote Ethiopian population. Perception, 1(4), 417–425. ..ttps://
  • DIN ISO 690: specification in DOI form only

    DEREGOWSKI, Jan B., Elisabeth S. MULDROW und William F. MULDROW, 1972. Pictorial recognition in a remote Ethiopian population. In: Perception. 1(4), S. 417–425. Verfügbar unter: DOI: 10.1068/p010417

Note: The specification of a retrieval date is not required in either system, as the content of a DOI-tagged document should not change. Nevertheless, some citation systems may require such a date.

Information: URN

What is a URN for?

In abstract terms, a URN is an identifier that identifies a physical, digital or abstract resource uniquely, permanently and independently of location. A "resource" can be understood as anything that can be described unambiguously.

A URN is used, among other things, to give digital publications and other electronic documents (e.g. research datasets) a unique name.

Who assigns URNs?

URNs are assigned by registration agencies, in Germany for example by the German National Library. The agencies also maintain the resolving mechanism, which ensures the forwarding of a URN to a valid URL address.

If you publish a document via the publication server of Trier UAS, it automatically receives a URN.

What does a URN look like?

A URN has the following basic form:

  • urn:<namespace identifier>:<resource identifier>


  • "urn": fixed identifier for URNs (special URI type),
  • <namespace identifier>: designation of the information space or standard used for the identifier (e.g. "isbn", "issn" or "nbn"),
  • <resource identifier>: namespace-specific unique identifier of the resource (e.g. "9780465026562" for ISBN).


  • urn:isbn:9780465026562 [monograph on ISB standard],
  • urn:issn:09336451 [journal on ISS standard],
  • urn:nbn:en:bvb:91-diss20060308-1417541491 [more complex variant: dissertation via National Bibliography Number "nbn" with country number and subname-space].


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