Authority files
Authority files for unique identification are assigned to individuals, institutions, research funders, and much more. This fascilitates for example the search of people regarding name similarity and the unique assignment for search engines. They include:
Open Researcher and Contributor ID (ORCID, http://orcid.org): The ORCID is an (alpha) numeric 16-digit code and uniquely identifies persons (authors or contributors) comparable to a DOI for resources. The ORCID registration is free of charge.
Integrated Authority File (German: Gemeinsame Normdatei, GND, https://www.dnb.de/EN/Professionell/Standardisierung/GND/gnd_node.html): the GND serves mainly the cataloguing of literature in libraries, but is also increasingly adopted for other types of use. The German National Library and other institutions lead the GND cooperatively. Participation is possible either via the German-speaking library consortia or by direct contact with the German National Library.
International Standard Name Identifier (ISNI, ISO 27729, http://www.isni.org): The ISNI is a 16-digit code to identify persons involved in a publication. The ISNI is a standard of the International Organization for Standardization (ISO) and comparable to the ORCID.
Virtual International Authority File (VIAF, http://www.viaf.org): VIAF is an international authority file for personal data and is hosted and run by the Online Computer Library Center (OCLC) in Dublin, Ohio (United States). Authority files of GND and ISNI are both part of VIAF and there added to data of other national authority files.
Funder Registry (https://www.crossref.org/services/funder-registry/): An identification service for research funders. With the Funder Registry ID for example publications, but also research data can be associated to a specific funding project and research funders.
Research Organization Registry (ROR, https://ror.org): ROR is designed to provide a persistent and unique identification for research organizations worldwide. ROR is currently being developed within a project and its results address the affiliation problems of many research institutions.
VIAF as well as ORCID or other identifiers of a person can be used for example during the DOI registration process to achieve unique identification of authors and contributors (e.g. project leader).