The handle system is used to manage (abstract) globally unique namespaces. For repositories it enables the persistent identification and localization of digital information on the World Wide Web. The handle system is used in the Phaidra repository at the University Library of Vienna. Handle IDs are automatically assigned there for each digital object.

Digital Object Identifiers are primarily used for online articles in scientific journals, publications in open access repositories and for the citability of research data. DOI is an application of the handle system. You can apply for a Digital Object Identifier (DOI) for digital objects such as publications, supplementary materials for these publications or research data.

A Uniform Resource Name (URN) is another identifier for electronic objects, which is mainly used in the library sector in the form of the NBN (National Bibliography Number). At the Vienna University Library, URNs are automatically used for all academic theses are awarded in the E-Theses repository and for books in Phaidra.