What is a DOI, Handle, ARK, URL, URI, ...?

Here we describe some commonly seen object identifiers. Derived from a report by the ODIN project. See https://dx.doi.org/10.6084/m9.figshare.1373669.v1 for more information.

Example - hdl:2381/12775
Non-commercial decentralized identifier resolution system, established in 1995. Operated by CNRI. Used by many other higherlevel systems, e.g. DOI.A non-commercial Handle system that is
operated by the Corporation for National Research Initiatives (CNRI)Different initiatives use commercial handle licenses to establish local handle system, such as the European Persistent Identifier Consortium (EPIC). Many existing content management systems, including institutional repositories, currently operate their own local handle system.

DOI - Digital Object Identifier
Example - doi:10.1186/2041-1480-3-9
Combines a metadata model with the Handle system as the resolution infrastructure (i.e. DOIs are handles). First introduced in 1998 with the funding of the International DOI foundation (IDF).
Became official ISO standard in 2012 (ISO 26324). The DOI system is built upon CNRI Handles. DOI Registration agencies are responsible for assigning identifiers. They each have their own commercial or non-commercial business model for supporting the associated costs. The DOI system itself is maintained and advanced by the IDF, itself controlled by its registration agency members. Using
the Handle system, there is a central free worldwide resolving mechanism for DOI names. DOI names from any registration agency can be resolved worldwide in every handle server; DOIs therefore are self-sufficient and their resolution does not depend on a single agency. A standard metadata kernel is defined for every DOI name. Assigning DOI names involves the payment of a license fee but their resolution is free.

URN - Uniform Resource Name
Example - urn:isbn:0451450523

Introduced in 1994, formalized in 1997 and is now an IETF standard. No central governance, no central resolving infrastructure. Used by major national libraries in Europe. ISBNs for books are part of the URN system.
No license costs involved for assigning URNs, but a URN registration agency needs to establish an assigning and a resolving infrastructure. The biggest initiative to harmonize URN registration in Europe is currently undertaken by the PersID project.

ARK - Archival Resource
Example - ark:/13030/tf5p30086k

Introduced in 1995.Not a formal standard but all ARKs follow the same structure and workflows. No central resolver - organisations can sign up to become Name Assigning Authority Numbers (NAANs) and run their own resolution infrastructure for ARKs. System is run by the California Digital Library with dozens of NAANs worldwide through a combined ARK/DOI infrastructure EZID.

AARCAuthentication and Authorisation for Research and Collaboration, https://aarc-project.eu/
ANDSAustralian National Data Service, http://www.ands.org.au/
APIApplication Program Interface
ARKArchival Resource Key, identifier for information objects of any type
BioCaddieBiomedical and healthCAre Data Discovery Index Ecosystem, https://biocaddie.org/
CASRAIConsortia Advancing Standards in Research Administration Information, http://casrai.org/
CERNEuropean Organization for Nuclear Research, home.cern
CrossRefAn official Digital Object Identifier Registration Agency of the International DOI Foundation, working to make content easy to find, link, cite and assess in scholarly publishing, http://www.crossref.org/
DataCiteAn organisation that develops and supports methods to locate, identify and cite data and other research objects. Specifically, DataCite develops and supports the standards behind persistent identifiers for data, and the members assign them, https://www.datacite.org
DCCDigital Curation Centre, http://www.dcc.ac.uk/
DOIDigital Object Identifier
DSpaceSoftware application to build open repositories, http://www.dspace.org/
EUEuropean Union
ECEuropean Commission
EMBL-EBIThe European Bioinformatics Institute, Part of the European Molecular Biology Laboratory, http://www.ebi.ac.uk/
EuroCRISEuropean Current Research Information Systems, http://www.eurocris.org/
ETDElectronic Theses and Dissertations
EVER-ESTEuropean Virtual Environment for Research - Earth Science Themes
EprintsOpen resource digital repository platform, http://www.eprints.org/
FedoraOpen source repository system for the management and dissemination of digital content, http://fedorarepository.org/
FORCE11Future of Research Communications and e-Scholarship: community of scholars, librarians, archivists, publishers and research funders that has arisen organically to help facilitate the change toward improved knowledge creation and sharing, https://www.force11.org/
FundrefA standard way of reporting funding sources for published scholarly research, http://www.crossref.org/fundingdata/index.html
GRIDGlobal Research Identifier Database, https://grid.ac/
HandlePrefix registration system, www.handle.net
IFLAInternational Federation of Library Associations and Institutions, http://www.ifla.org/
InvinioSoftware applications for digital libraries, http://invenio-software.org/
ISNIInternational Standard Name Identifier
JISCUK higher education, further education and skills sectors’ not-for-profit organisation for digital services and solutions, https://www.jisc.ac.uk/
JupyterWeb application that enables the creation and sharing of documents that contain live code.
KPIKey Performance Indicator
LIBERLigue des Bibliothèques Européennes de Recherche (Association of European Research Libraries), http://libereurope.eu/
NISONational Information Standards Organisation, http://www.niso.org/home/
ODINORCID and DataCite Interoperability Network, https://odin-project.eu/
OpenAIREProject that seeks to connect aggregated research publications to the accompanying research and project information, datasets and author information, https://www.openaire.eu/
OpenDreamKitOpen Digital Research Environment Toolkit for the Advancement of Mathematics, www.opendreamkit.org
ORCIDOriginal Researcher and Contributer ID, http://orcid.org
PANGAEAAn information system and data publisher for geoscientific and environmental data, https://www.pangaea.de/
PIDPersistent Identifier
PRACEPartnership for Advanced Computing in Europe, www.prace-ri.eu
Re3dataRegistry of Research Data Repositories, www.re3data.org
REFEDSResearch and Education FEDerations Group
RDAResearch Data Alliance, https://rd-alliance.org/
RinggoldOrganisation that provides unique identifiers for organisations in the publishing industry supply chain, http://www.ringgold.com/
RRIDResearch Resource Identifier
SDKSoftware Development Kit
THORTechnical and Human Infrastructure for Open Research, https://project-thor.eu/
UKSGOrganisation that aims to connect the knowledge community and encourage the exchange of ideas on scholarly communication, spanning librarians, publishers, intermediaries and technology vendors, http://www.uksg.org/
UXUser eXperience