Digital object identifier

In computing, a digital object identifier (DOI) is a persistent identifier or handle used to identify objects uniquely, standardized by the International Organization for Standardization (ISO).[1] An implementation of the Handle System,[2][3] DOIs are in wide use mainly to identify academic, professional, and government information, such as journal articles, research reports and data sets, and official publications though they also have been used to identify other types of information resources, such as commercial videos.

A DOI aims to be "resolvable", usually to some form of access to the information object to which the DOI refers. This is achieved by binding the DOI to metadata about the object, such as a URL, indicating where the object can be found. Thus, by being actionable and interoperable, a DOI differs from identifiers such as ISBNs and ISRCs which aim only to identify their referents uniquely. The DOI system uses the indecs Content Model for representing metadata.

The DOI for a document remains fixed over the lifetime of the document, whereas its location and other metadata may change. Referring to an online document by its DOI is supposed to provide a more stable link than simply using its URL. But every time a URL changes, the publisher has to update the metadata for the DOI to link to the new URL.[4][5][6] It is the publisher's responsibility to update the DOI database. If they fail to do so, the DOI resolves to a dead link leaving the DOI useless.

The developer and administrator of the DOI system is the International DOI Foundation (IDF), which introduced it in 2000.[7] Organizations that meet the contractual obligations of the DOI system and are willing to pay to become a member of the system can assign DOIs.[8] The DOI system is implemented through a federation of registration agencies coordinated by the IDF.[9] By late April 2011 more than 50 million DOI names had been assigned by some 4,000 organizations,[10] and by April 2013 this number had grown to 85 million DOI names assigned through 9,500 organizations.

Digital object identifier
DOI logo
Managing organisationInternational DOI Foundation

Nomenclature and syntax

A DOI is a type of Handle System handle, which takes the form of a character string divided into two parts, a prefix and a suffix, separated by a slash.


The prefix identifies the registrant of the identifier, and the suffix is chosen by the registrant and identifies the specific object associated with that DOI. Most legal Unicode characters are allowed in these strings, which are interpreted in a case-insensitive manner. The prefix usually takes the form 10.NNNN, where NNNN is a series of at least 4 numbers greater than or equal to 1000, whose limit depends only on the total number of registrants.[11][12] The prefix may be further subdivided with periods, like 10.NNNN.N.[13]

For example, in the DOI name 10.1000/182, the prefix is 10.1000 and the suffix is 182. The "10." part of the prefix distinguishes the handle as part of the DOI namespace, as opposed to some other Handle System namespace,[A] and the characters 1000 in the prefix identify the registrant; in this case the registrant is the International DOI Foundation itself. 182 is the suffix, or item ID, identifying a single object (in this case, the latest version of the DOI Handbook).

DOI names can identify creative works (such as texts, images, audio or video items, and software) in both electronic and physical forms, performances, and abstract works[14] such as licenses, parties to a transaction, etc.

The names can refer to objects at varying levels of detail: thus DOI names can identify a journal, an individual issue of a journal, an individual article in the journal, or a single table in that article. The choice of level of detail is left to the assigner, but in the DOI system it must be declared as part of the metadata that is associated with a DOI name, using a data dictionary based on the indecs Content Model.


The official DOI Handbook explicitly states that DOIs should display on screens and in print in the format doi:10.1000/182.[15]

Contrary to the DOI Handbook, CrossRef, a major DOI registration agency, recommends displaying a URL (for example, instead of the officially specified format (for example, doi:10.1000/182)[16][17] This URL is persistent (there is a contract that ensures persistence in the DOI.ORG domain), so it is a PURL — providing the location of an HTTP proxy server which will redirect web accesses to the correct online location of the linked item.[8][18]

The CrossRef recommendation is primarily based on the assumption that the DOI is being displayed without being hyperlinked to its appropriate URL – the argument being that without the hyperlink it is not as easy to copy-and-paste the full URL to actually bring up the page for the DOI, thus the entire URL should be displayed, allowing people viewing the page containing the DOI to copy-and-paste the URL, by hand, into a new window/tab in their browser in order to go to the appropriate page for the document the DOI represents.[19]


Major applications of the DOI system currently include:

  • Scholarly materials (journal articles, books, ebooks, etc.) through CrossRef, a consortium of around 3,000 publishers; Airiti, a leading provider of electronic academic journals in Chinese and Taiwanese; and the Japan Link Center (JaLC) an organization providing link management and DOI assignment for electronic academic journals in Japanese.
  • Research datasets through Datacite, a consortium of leading research libraries, technical information providers, and scientific data centers;
  • European Union official publications through the EU publications office;
  • The Chinese National Knowledge Infrastructure project at Tsinghua University and the Institute of Scientific and Technical Information of China (ISTIC), two initiatives sponsored by the Chinese government.
  • Permanent global identifiers for commercial video content through the Entertainment ID Registry, commonly known as EIDR.

In the Organisation for Economic Co-operation and Development's publication service OECD iLibrary, each table or graph in an OECD publication is shown with a DOI name that leads to an Excel file of data underlying the tables and graphs. Further development of such services is planned.[20]

Other registries include Crossref and the multilingual European DOI Registration Agency.[21] Since 2015, RFCs can be referenced as doi:10.17487/rfc.[22]

DOI and other special identifiers can help to unify information about references with different spelling in various language versions of Wikipedia.[23]

Features and benefits

The IDF designed the DOI system to provide a form of persistent identification, in which each DOI name permanently and unambiguously identifies the object to which it is associated. It also associates metadata with objects, allowing it to provide users with relevant pieces of information about the objects and their relationships. Included as part of this metadata are network actions that allow DOI names to be resolved to web locations where the objects they describe can be found. To achieve its goals, the DOI system combines the Handle System and the indecs Content Model with a social infrastructure.

The Handle System ensures that the DOI name for an object is not based on any changeable attributes of the object such as its physical location or ownership, that the attributes of the object are encoded in its metadata rather than in its DOI name, and that no two objects are assigned the same DOI name. Because DOI names are short character strings, they are human-readable, may be copied and pasted as text, and fit into the URI specification. The DOI name-resolution mechanism acts behind the scenes, so that users communicate with it in the same way as with any other web service; it is built on open architectures, incorporates trust mechanisms, and is engineered to operate reliably and flexibly so that it can be adapted to changing demands and new applications of the DOI system.[24] DOI name-resolution may be used with OpenURL to select the most appropriate among multiple locations for a given object, according to the location of the user making the request.[25] However, despite this ability, the DOI system has drawn criticism from librarians for directing users to non-free copies of documents that would have been available for no additional fee from alternative locations.[26]

The indecs Content Model as used within the DOI system associates metadata with objects. A small kernel of common metadata is shared by all DOI names and can be optionally extended with other relevant data, which may be public or restricted. Registrants may update the metadata for their DOI names at any time, such as when publication information changes or when an object moves to a different URL.

The International DOI Foundation (IDF) oversees the integration of these technologies and operation of the system through a technical and social infrastructure. The social infrastructure of a federation of independent registration agencies offering DOI services was modelled on existing successful federated deployments of identifiers such as GS1 and ISBN.

Comparison with other identifier schemes

A DOI name differs from commonly used Internet pointers to material, such as the Uniform Resource Locator (URL), in that it identifies an object itself as a first-class entity, rather than the specific place where the object is located at a certain time. It implements the Uniform Resource Identifier (Uniform Resource Name) concept and adds to it a data model and social infrastructure.[27]

A DOI name also differs from standard identifier registries such as the ISBN, ISRC, etc. The purpose of an identifier registry is to manage a given collection of identifiers, whereas the primary purpose of the DOI system is to make a collection of identifiers actionable and interoperable, where that collection can include identifiers from many other controlled collections.[28]

The DOI system offers persistent, semantically-interoperable resolution to related current data and is best suited to material that will be used in services outside the direct control of the issuing assigner (e.g., public citation or managing content of value). It uses a managed registry (providing social and technical infrastructure). It does not assume any specific business model for the provision of identifiers or services and enables other existing services to link to it in defined ways. Several approaches for making identifiers persistent have been proposed. The comparison of persistent identifier approaches is difficult because they are not all doing the same thing. Imprecisely referring to a set of schemes as "identifiers" doesn't mean that they can be compared easily. Other "identifier systems" may be enabling technologies with low barriers to entry, providing an easy to use labeling mechanism that allows anyone to set up a new instance (examples include Persistent Uniform Resource Locator (PURL), URLs, Globally Unique Identifiers (GUIDs), etc.), but may lack some of the functionality of a registry-controlled scheme and will usually lack accompanying metadata in a controlled scheme. The DOI system does not have this approach and should not be compared directly to such identifier schemes. Various applications using such enabling technologies with added features have been devised that meet some of the features offered by the DOI system for specific sectors (e.g., ARK).

A DOI name does not depend on the object's location and, in this way, is similar to a Uniform Resource Name (URN) or PURL but differs from an ordinary URL. URLs are often used as substitute identifiers for documents on the Internet although the same document at two different locations has two URLs. By contrast, persistent identifiers such as DOI names identify objects as first class entities: two instances of the same object would have the same DOI name.


DOI name resolution is provided through the Handle System, developed by Corporation for National Research Initiatives, and is freely available to any user encountering a DOI name. Resolution redirects the user from a DOI name to one or more pieces of typed data: URLs representing instances of the object, services such as e-mail, or one or more items of metadata. To the Handle System, a DOI name is a handle, and so has a set of values assigned to it and may be thought of as a record that consists of a group of fields. Each handle value must have a data type specified in its <type> field, which defines the syntax and semantics of its data. While a DOI persistently and uniquely identifies the object to which it is assigned, DOI resolution may not be persistent, due to technical and administrative issues.

To resolve a DOI name, it may be input to a DOI resolver, such as

Another approach, which avoids typing or cutting-and-pasting into a resolver is to include the DOI in a document as a URL which uses the resolver as an HTTP proxy, such as (preferred)[29] or, both of which support HTTPS. For example, the DOI 10.1000/182 can be included in a reference or hyperlink as This approach allows users to click on the DOI as a normal hyperlink. Indeed, as previously mentioned, this is how CrossRef recommends that DOIs always be represented (preferring HTTPS over HTTP), so that if they are cut-and-pasted into other documents, emails, etc., they will be actionable.

Other DOI resolvers and HTTP Proxies include, and At the beginning of the year 2016, a new class of alternative DOI resolvers was started by This service is unusual in that it tries to find a non-paywalled version of a title and redirects you to that instead of the publisher's version.[30][31] Since then, other open-access favoring DOI resolvers have been created, notably in October 2016.[32] While traditional DOI resolvers solely rely on the Handle System, alternative DOI resolvers first consult open access resources such as BASE (Bielefeld Academic Search Engine).[30][32]

An alternative to HTTP proxies is to use one of a number of add-ons and plug-ins for browsers, thereby avoiding the conversion of the DOIs to URLs,[33] which depend on domain names and may be subject to change, while still allowing the DOI to be treated as a normal hyperlink. For example. the CNRI Handle Extension for Firefox, enables the browser to access Handle System handles or DOIs like hdl:4263537/4000 or doi:10.1000/1 directly in the Firefox browser, using the native Handle System protocol. This plug-in can also replace references to web-to-handle proxy servers with native resolution. A disadvantage of this approach for publishers is that, at least at present, most users will be encountering the DOIs in a browser, mail reader, or other software which does not have one of these plug-ins installed.

IDF organizational structure

The International DOI Foundation (IDF), a non-profit organisation created in 1998, is the governance body of the DOI system.[34] It safeguards all intellectual property rights relating to the DOI system, manages common operational features, and supports the development and promotion of the DOI system. The IDF ensures that any improvements made to the DOI system (including creation, maintenance, registration, resolution and policymaking of DOI names) are available to any DOI registrant. It also prevents third parties from imposing additional licensing requirements beyond those of the IDF on users of the DOI system.

The IDF is controlled by a Board elected by the members of the Foundation, with an appointed Managing Agent who is responsible for co-ordinating and planning its activities. Membership is open to all organizations with an interest in electronic publishing and related enabling technologies. The IDF holds annual open meetings on the topics of DOI and related issues.

Registration agencies, appointed by the IDF, provide services to DOI registrants: they allocate DOI prefixes, register DOI names, and provide the necessary infrastructure to allow registrants to declare and maintain metadata and state data. Registration agencies are also expected to actively promote the widespread adoption of the DOI system, to cooperate with the IDF in the development of the DOI system as a whole, and to provide services on behalf of their specific user community. A list of current RAs is maintained by the International DOI Foundation. The IDF is recognized as one of the federated registrars for the Handle System by the DONA Foundation (of which the IDF is a board member), and is responsible for assigning Handle System prefixes under the top-level 10 prefix.[35]

Registration agencies generally charge a fee to assign a new DOI name; parts of these fees are used to support the IDF. The DOI system overall, through the IDF, operates on a not-for-profit cost recovery basis.


The DOI system is an international standard developed by the International Organization for Standardization in its technical committee on identification and description, TC46/SC9.[36] The Draft International Standard ISO/DIS 26324, Information and documentation – Digital Object Identifier System met the ISO requirements for approval. The relevant ISO Working Group later submitted an edited version to ISO for distribution as an FDIS (Final Draft International Standard) ballot,[37] which was approved by 100% of those voting in a ballot closing on 15 November 2010.[38] The final standard was published on 23 April 2012.[1]

DOI is a registered URI under the info URI scheme specified by IETF RFC 4452. info:doi/ is the infoURI Namespace of Digital Object Identifiers.[39]

The DOI syntax is a NISO standard, first standardised in 2000, ANSI/NISO Z39.84-2005 Syntax for the Digital Object Identifier.[40]

The maintainers of the DOI system have deliberately not registered a DOI namespace for URNs, stating that:

URN architecture assumes a DNS-based Resolution Discovery Service (RDS) to find the service appropriate to the given URN scheme. However no such widely deployed RDS schemes currently exist.... DOI is not registered as a URN namespace, despite fulfilling all the functional requirements, since URN registration appears to offer no advantage to the DOI System. It requires an additional layer of administration for defining DOI as a URN namespace (the string urn:doi:10.1000/1 rather than the simpler doi:10.1000/1) and an additional step of unnecessary redirection to access the resolution service, already achieved through either http proxy or native resolution. If RDS mechanisms supporting URN specifications become widely available, DOI will be registered as a URN.

— International DOI Foundation, Factsheet: DOI System and Internet Identifier Specifications[41]

See also


  1. ^ Other registries are identified by other strings at the start of the prefix. Handle names that begin with "100." are also in use, as for example in the following citation: Hammond, Joseph L., Jr.; Brown, James E.; Liu, Shyan-Shiang S. (May 1975). "Development of a Transmission Error Model and an Error Control Model l". Technical Report RADC-TR-75-138. Rome Air Development Center. Bibcode:1975STIN...7615344H. hdl:100.2/ADA013939.


  1. ^ a b "ISO 26324:2012(en), Information and documentation — Digital object identifier system". ISO. Retrieved 20 April 2016.
  2. ^ "The Handle System".
  3. ^ "Factsheets".
  4. ^ Witten, Ian H.; David Bainbridge & David M. Nichols (2010). How to Build a Digital Library (2nd ed.). Amsterdam; Boston: Morgan Kaufmann. pp. 352–253. ISBN 978-0-12-374857-7.
  5. ^ Langston, Marc; Tyler, James (2004). "Linking to journal articles in an online teaching environment: The persistent link, DOI, and OpenURL". The Internet and Higher Education. 7 (1): 51–58. doi:10.1016/j.iheduc.2003.11.004.
  6. ^ "How the 'Digital Object Identifier' works". BusinessWeek. BusinessWeek. 23 July 2001. Retrieved 20 April 2010. Assuming the publishers do their job of maintaining the databases, these centralized references, unlike current web links, should never become outdated or broken.
  7. ^ Paskin, Norman (2010), "Digital Object Identifier (DOI) System", Encyclopedia of Library and Information Sciences (3rd ed.), Taylor and Francis, pp. 1586–1592
  8. ^ a b Davidson, Lloyd A.; Douglas, Kimberly (December 1998). "Digital Object Identifiers: Promise and problems for scholarly publishing". Journal of Electronic Publishing. 4 (2). doi:10.3998/3336451.0004.203.
  9. ^ "Welcome to the DOI System". 28 June 2010. Retrieved 7 August 2010.
  10. ^ "DOI News, April 2011: 1. DOI System exceeds 50 million assigned identifiers". 20 April 2011. Retrieved 3 July 2011.
  11. ^ "doi info & guidelines". Publishers International Linking Association, Inc. 2013. Archived from the original on 21 October 2002. Retrieved 10 June 2016. All DOI prefixes begin with "10" to distinguish the DOI from other implementations of the Handle System followed by a four-digit number or string (the prefix can be longer if necessary).
  12. ^ "Factsheet—Key Facts on Digital Object Identifier System". International DOI Foundation. 6 June 2016. Retrieved 10 June 2016. Over 18,000 DOI name prefixes within the DOI System
  13. ^ "DOI Handbook—2 Numbering". International DOI Foundation. 1 February 2016. Retrieved 10 June 2016. The registrant code may be further divided into sub-elements for administrative convenience if desired. Each sub-element of the registrant code shall be preceded by a full stop.
  14. ^ "Frequently asked questions about the DOI system: 6. What can a DOI name be assigned to?". International DOI Foundation. 3 July 2018 [update of earlier version]. Retrieved 19 July 2018.
  15. ^ "DOI Handbook – Numbering". 13 February 2014. Section 2.6.1 Screen and print presentation. Archived from the original on 30 June 2014. Retrieved 30 June 2014.
  16. ^ "DOI Display Guidelines".
  17. ^ "New Crossref DOI display guidelines are on the way".
  18. ^ Powell, Andy (June 1998). "Resolving DOI Based URNs Using Squid: An Experimental System at UKOLN". D-Lib Magazine. ISSN 1082-9873.
  19. ^ ChrissieCW. "Crossref Revises DOI Display Guidelines - Crossref".
  20. ^ Green, T. (2009). "We Need Publishing Standards for Datasets and Data Tables". Research Information. doi:10.1787/603233448430.
  21. ^ "multilingual European DOI Registration Agency". 2003.
  22. ^ Levine, John R. (2015). "Assigning Digital Object Identifiers to RFCs § DOIs for RFCs". IAB. doi:10.17487/rfc7669. RFC 7669.
  23. ^ Lewoniewski, Włodzimierz; Węcel, Krzysztof; Abramowicz, Witold (23 September 2017). "Analysis of References Across Wikipedia Languages". Communications in Computer and Information Science. 756: 561–573. doi:10.1007/978-3-319-67642-5_47. Retrieved 6 May 2018.
  24. ^ Timmer, John (6 March 2010). "DOIs and their discontents". Ars Technica. Retrieved 5 March 2013.
  25. ^ DeRisi, Susanne; Kennison, Rebecca; Twyman, Nick (2003). "Editorial: The what and whys of DOIs". PLoS Biology. 1 (2): e57. doi:10.1371/journal.pbio.0000057. PMC 261894. PMID 14624257. open access
  26. ^ Franklin, Jack (2003). "Open access to scientific and technical information: the state of the art". In Grüttemeier, Herbert; Mahon, Barry (eds.). Open access to scientific and technical information: state of the art and future trends. IOS Press. p. 74. ISBN 978-1-58603-377-4.
  27. ^ "DOI System and Internet Identifier Specifications". 18 May 2010. Retrieved 7 August 2010.
  28. ^ "DOI System and standard identifier registries". Retrieved 7 August 2010.
  29. ^ International DOI Foundation (7 August 2014). "Resolution". DOI Handbook. Retrieved 19 March 2015.
  30. ^ a b "DOAI". CAPSH (Committee for the Accessibility of Publications in Sciences and Humanities). Retrieved 6 August 2016.
  31. ^ Schonfeld, Roger C. (3 March 2016). "Co-opting 'Official' Channels through Infrastructures for Openness". The Scholarly Kitchen. Retrieved 17 October 2016.
  32. ^ a b Piwowar, Heather (25 October 2016). "Introducing oaDOI: resolve a DOI straight to OA". Retrieved 17 March 2017.
  33. ^ "DOI System Tools".
  34. ^ "Chapter 7: The International DOI Foundation". DOI Handbook. Retrieved 8 July 2015.
  35. ^ "DONA Foundation Multi-Primary Administrators". Archived from the original on 14 January 2017. Retrieved 7 February 2017.
  36. ^ "Digital object identifier (DOI) becomes an ISO standard". 10 May 2012. Retrieved 10 May 2012.
  37. ^ "about_the_doi.html DOI Standards and Specifications". 28 June 2010. Retrieved 7 August 2010.
  38. ^ "Overviews & Standards – Standards and Specifications: 1. ISO TC46/SC9 Standards". 18 November 2010. Retrieved 3 July 2011.
  39. ^ "About "info" URIs – Frequently Asked Questions". Retrieved 7 August 2010.
  40. ^ "ANSI/NISO Z39.84-2000 Syntax for the Digital Object Identifier". Retrieved 7 August 2010.
  41. ^ International DOI Foundation (2012).

External links


1914-1918-online. International Encyclopedia of the First World War is an international, English-language online encyclopedia of the First World War. Deemed the largest research network of its kind, it officially went online on 8 October 2014. The editorial office is staffed by historians and uses Semantic MediaWiki.

The Freie Universität Berlin (FU Berlin) and the Bayerische Staatsbibliothek (Bavarian State Library) in Munich initiated the online academic reference work in the run-up to the centenary commemorations of the Great War. The project has since gained the support of several international partners, including the German Historical Institutes in London, Moscow, Paris, Rome, Warsaw as well as the Orient-Institut Istanbul (Oriental Institute in Istanbul). It has furthermore acquired eight-figure funds from the Deutsche Forschungsgemeinschaft (German Research Foundation), funding which was extended in 2016 by an “Open Encyclopedia System” follow-up grant.

The project leaders are Oliver Janz, professor of modern history at the Friedrich-Meinecke-Institut (FMI), Nicolas Apostolopoulos, director of the Center for Digital Systems (CeDiS), both at the Freie Universität Berlin, and Gregor Horstkemper from the Zentrum für Elektronisches Publizieren - ZEP (Center for Electronic Publication) at the Bavarian State Library.1914-1918-online intends to provide the most recent global research on the First World War to the academic community and the public through a multi-perspective, open-access approach. Up to 1,000 experts from over fifty different countries will be working or have worked on this ongoing project. With a goal of approximately 1,500 entries, all content is published using the Creative Commons license CC BY-NC-ND 3.0. The fully citable, Digital Object Identifier (DOI) equipped texts have been peer-reviewed (double blind) and enriched with images, maps and other related content. The encyclopedia is divided thematically and regionally, and all sections are easily accessible via search and navigation options (filter, register, timeline). Links and interfaces connect 1914-1918-online to other databases as well as information systems such as Europeana 1914-1918, CENDARI, WorldCat and Zotero.

The editorial board is composed of seven General Editors (Ute Daniel, Peter Gatrell, Oliver Janz, Heather Jones, Jennifer Keene, Alan Kramer and Bill Nasson), several Section Editors, and numerous external reviewers, a total of roughly 100 persons. The Editorial Advisory Board includes Annette Becker, Jürgen Danyel, Josef Ehmer, Gudrun Gersmann, Antonio Gibelli, Gerhard Hirschfeld, John Horne, Jürgen Kocka, Gerd Krumeich, Jürgen Osterhammel, Hew Strachan, Jay Winter and Erik-Jan Zürcher.The project made the American Library Association’s 2015 “Annual List of Best Historical Materials” and received the second prize at the 2015 Berlin Digital Humanities Awards.


The bibcode (also known as the refcode) is a compact identifier used by several astronomical data systems to uniquely specify literature references.


Connotea was a free online reference management service for scientists, researchers, and clinicians, created in December 2004 by Nature Publishing Group and discontinued in March 2013. It was one of a breed of social bookmarking tools, similar to CiteULike and, where users can save links to their favourite websites. ReadCube is a similar free service that offers storage, annotation and sharing tools specifically for scientific documents.

Connotea was aimed primarily at scientists (though the user community included other academic disciplines), and while users could bookmark any webpage they chose, it incorporated special functionality for certain academic resources. Connotea recognised a number of scientific websites and automatically collected metadata for the article or page being bookmarked, including author and publication names. It was also possible to add non-recognised webpages by manually entering information. An alternative method of adding an article was to retrieve the Connotea form and add the Digital Object Identifier (DOI) for the article. Information about the material was retrieved automatically using CrossRef, the official DOI registration point. This function meant that it was possible to quickly retrieve the reference for a print article that had an electronic counterpart with a DOI.

When saving an article to Connotea, users "tagged" the article with keywords of their choice which they could later use to find it again. By categorising articles with relevant keywords e.g. "C. elegans", the social aspect of Connotea was developed. The system recognised users who were bookmarking the same papers or using the same keywords, and alerted them to potentially-related material. Allowing completely free tagging means a folksonomy can gradually develop. By default, links posted to Connotea were publicly viewable, allowing network effects to build up rapidly, but it was also possible for users to keep selected links private, either indefinitely or until a specified date and time. Connotea also provided RSS feeds, allowing users to keep track of articles posted under interesting tags or by users with similar interests.

Connotea had the capacity to export the references in RIS format to a citation manager program. This meant that it was possible to save references when working on a computer without such bibliographic software installed and import them into this software for citing at a later stage.

In September 2005, Connotea won the Association of Learned and Professional Society Publishers Award for Publishing Innovation, and in November 2005 was shortlisted for the International Information Industry awards in the Best Scientific, Technical and Medical (STM) Product category.Connotea discontinued service on March 12, 2013. An export tool remained live until April 16, 2013 so that registered users could export their bookmarks.

Corporation for National Research Initiatives

The Corporation for National Research Initiatives (CNRI), based in Reston, Virginia, is a non-profit organization founded in 1986 by Robert E. Kahn as an "activities center around strategic development of network-based information technologies", including the National Information Infrastructure (NII) in the United States.CNRI develops the Handle System for managing and locating digital information. CNRI obtained DARPA funding for the development of JPython (Jython), a Python implementation in and for Java, initially created by Jim Hugunin.


Crossref (formerly styled CrossRef) is an official Digital Object Identifier (DOI) Registration Agency of the International DOI Foundation. It is run by the Publishers International Linking Association Inc. (PILA) and was launched in early 2000 as a cooperative effort among publishers to enable persistent cross-publisher citation linking in online academic journals.

Current injection technique

The current injection technique is a technique developed to reduce the turn-OFF switching transient of power bipolar semiconductor devices. It was developed and published by Dr S. Eio of Staffordshire University (United Kingdom) in 2007.

Data citation

Data citation is the provision of accurate, consistent and standardised referencing for datasets just as bibliographic citations are provided for other published sources like research articles or monographs. Typically the well established Digital Object Identifier (DOI) approach is used with DOIs taking users to a website that contains the metadata on the dataset and the dataset itself.A 2011 paper reported an inability to determine how often data citation happened in social sciences.2012-13 papers reported that data citation was becoming more common but the practice for it was not standard.In 2014 the Force11 Scholarly Communication Institute published a statement recommending data citation.In October 2018 CrossRef expressed its support for cataloging datasets and recommending their citation.A popular data-oriented journal reported in April 2019 that it would now use data citations.A June 2019 paper suggested that increased data citation will make the practice more valuable for everyone by encouraging data sharing and also by increasing the prestige of people who share.Data citation is an emerging topic in computer science and it has been defined as a computational problem.

Indeed, citing data poses significant challenges to computer scientists and the main problems to address are related to:

the use of heterogeneous data models and formats – e.g., relational databases, Comma-Separated Values (CSV), eXtensible Markup Language (XML), Resource Description Framework (RDF);

the transience of data;

the necessity to cite data at different levels of coarseness – i.e., deep citations;

the necessity to automatically generate citations to data with variable granularity.

Douglas Armati

Douglas "Doug" Armati (born 1950) is an Australian writer, researcher, consultant, business development executive and technical diplomat.

Doug Armati undertook research work on digital copyright issues at Murdoch University in Western Australia in 1990–91 before taking a role in international efforts to standardize the identification of digital objects.

After a speech on the importance and potential economic benefits of uniform approach to identification of digitized copyright content to the International Association of Scientific, Technical, and Medical Publishers at the Frankfurt Book Fair in October 1994 he wrote two pivotal reports in 1995 – the first for the STM group on Information Identification and the second for the Association of American Publishers on Uniform File Identifiers. Armati's work for these global publishing bodies was an important catalyst for the birth of the Digital Object Identifier Foundation.

His 1996 speech at the joint ICSU/UNESCO Electronic Publishing in Science conference in Paris on "Tools and standards for protection, control and archiving" and his book later that year on "Intellectual Property in Electronic Environments" both helped frame the legal, scientific and technical debate in the emerging field of Digital Rights Management. Armati was also part of the digital copyright experts group that worked closely with the World Intellectual Property Organization in the period leading up to the ratification of the WIPO Copyright Treaty in December 1996.

In 1996 Armati joined InterTrust Technologies, the leading company in the then nascent field of Digital Rights Management, where he was a member of the leadership group through the company's 1999 IPO until its sale to Sony and Philips in early 2003.

During his time with InterTrust, Armati was also active in international standards groups, having been a vice-chairman of the Recording Industry Association of America's international Secure Digital Music Initiative, a board member of the Open eBook Forum (now the International Digital Publishing Forum) and a significant contributor to the Moving Picture Experts Group (MPEG), particularly in the development of a standard for the management and protection of intellectual property in MPEG-4, MPEG-7 and MPEG-21.


EIDR, or the Entertainment Identifier Registry, is a global unique identifier system for a broad array of audio visual objects, including motion pictures, television, and radio programs. The identification system resolves an identifier to a metadata record that is associated with top-level titles, edits, DVDs, encodings, clips, and mash-ups. EIDR also provides identifiers for Video Service providers, such as broadcast and cable networks.

As of February, 2018, EIDR contains over 1.8 million records, including 298K movies, and 794K episodes of over 25K TV series.

EIDR is an implementation of a Digital Object Identifier (DOI).


EarthArXiv (pronounced "Earth archive") is both a preprint server and a volunteer community devoted to open scholarly communication. As a preprint server, EarthArXiv publishes articles from all subdomains of Earth Science and related domains of planetary science. These publications are versions of scholarly papers that precede publication in peer-reviewed scientific journals. EarthArXiv is not itself a journal and does not evaluate the scientific quality of a paper. Instead, EarthArXiv serves as a platform for free hosting and rapid dissemination of scientific results. The EarthArXiv platform assigns each submission a Digital Object Identifier (DOI), therefore assigning provenance and making it citable in other scholarly works. EarthArXiv's mission is to promote open access, share open access and preprint resources, and participate in shared governance of the preprint server and its policies. EarthArXiv was launched on October 23, 2017.


GigaDB (GigaScience DataBase) is a disciplinary repository launched in 2011 with the aim of ensuring long-term access to massive multidimensional datasets from life science and biomedical science studies. The datasets are diverse and include genomic, transcriptomic, and imaging data. The datasets are curated by GigaDB biocurators who are employed by BGI and China National GeneBank.

In its inception, GigaDB was designed as the supporting archive for large-scale research data submitted to the data journal GigaScience whose focus is on ensuring reproducibility and reusability of biological and biomedical research. The scope of GigaDB has broadened to include computational research objects such as synthetic data, software and workflows. Datasets hosted in GigaDB are defined as a group of files and metadata that support a specific article or study. For each published GigaDB dataset, a digital object identifier is assigned and the data are indexed and discoverable in NCBI Datamed and the Clarivate Analytics DataCitation Index. GigaDB has also collaborated with Repositive to boost the discoverability of their human datasets.

Hyper Articles en Ligne

Hyper Articles en Ligne, generally shortened to HAL, is an open archive where authors can deposit scholarly documents from all academic fields. It has a good position in the international web repository ranking.HAL is run by the Centre pour la communication scientifique directe, a French computing centre, which is part of the French National Centre for Scientific Research, CNRS. Other French institutions, such as INRIA, have joined the system. While it is primarily directed towards French academics, participation is not restricted to them.

Documents in HAL are uploaded either by one of the authors with the consent of the others or by an authorized person on their behalf. Since 2017 it's also possible to use, a tool for easy and semi-automated deposit.HAL is a tool for direct scientific communication between academics. A text posted to HAL is normally comparable to that of a paper that an investigator might submit for publication in a peer-reviewed scientific journal or conference proceedings. A document deposited in HAL will not be subjected to any detailed scientific evaluation, but simply a rapid overview, to ensure that it falls within the category defined above.

An uploaded document does not need to have been published or even to be intended for publication: It may be posted to HAL as long as its scientific content justifies it. But should the article be published, contributors are invited to indicate the relevant bibliographic information and the digital object identifier (DOI).

HAL aims to ensure the long term preservation of the deposited documents that are stored there permanently and will receive a stable web address. Thus, like any publication in a traditional scientific journal, it can be cited in other work.

The free online access to these documents provided by HAL is intended to promote the best possible dissemination of research work; the intellectual property remains that of the authors.

For physics, mathematics and other natural science topics, HAL has an automated depositing agreement with arXiv. A similar agreement exists with PubMed Central for biomedical topics.

Over 120 institutions have their own entrance to HAL, called portals. HAL hosts institutional repositories (for universities, research organisms and units) as well as subject repositories ; one example is the Arts and Humanities eprint repository, hprints.

As an open access repository, HAL complies with the Open Archives Initiative (OAI-PMH) as well as with the European OpenAIRE project.


IDF or idf may refer to:

Israel Defense Forces, the military forces of the State of Israel

Israeli Diving Federation, a non-governmental SCUBA diving training organization based in Israel

Iceland Defense Force, a military command of the United States Armed Forces from 1951 to 2006

Indian Defence Force, a part-time defence force established as part of the Indian Army in 1917

Interaction Design Foundation, a non-profit educational organization

International Diabetes Federation, a worldwide alliance of diabetes associations

International DOI Foundation, the developer of the digital object identifier

International Standard Music Number

The International Standard Music Number or ISMN (ISO 10957) is a thirteen-character alphanumeric identifier for printed music developed by ISO.

International Standard Musical Work Code

International Standard Musical Work Code (ISWC) is a unique identifier for musical works, similar to ISBN for books. It is adopted as international standard ISO 15707. The ISO subcommittee with responsibility for the standard is TC 46/SC 9.

International Standard Serial Number

An International Standard Serial Number (ISSN) is an eight-digit serial number used to uniquely identify a serial publication, such as a magazine. The ISSN is especially helpful in distinguishing between serials with the same title. ISSN are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature.The ISSN system was first drafted as an International Organization for Standardization (ISO) international standard in 1971 and published as ISO 3297 in 1975. ISO subcommittee TC 46/SC 9 is responsible for maintaining the standard.

When a serial with the same content is published in more than one media type, a different ISSN is assigned to each media type. For example, many serials are published both in print and electronic media. The ISSN system refers to these types as print ISSN (p-ISSN) and electronic ISSN (e-ISSN), respectively. Conversely, as defined in ISO 3297:2007, every serial in the ISSN system is also assigned a linking ISSN (ISSN-L), typically the same as the ISSN assigned to the serial in its first published medium, which links together all ISSNs assigned to the serial in every medium.


ResearcherID is an identifying system for scientific authors. The system was introduced in January 2008 by Thomson Reuters.

This unique identifier aims at solving the problem of author identification and correct attribution of works. In scientific and academic literature it is common to cite name, surname, and initials of the authors of an article. Sometimes, however, there are authors with the same name, with the same initials, or the journal misspells names, resulting in several spellings for the same authors, and different authors with the same spelling.

Researchers can use ResearcherID to claim their published works and link their unique and persistent ResearcherID number to these works for correct attribution. In this way, they can also keep their publication list up to date and online.

The combined use of the Digital Object Identifier with the ResearcherID allows a unique association of authors and research articles. It can be used to link researchers with registered trials or identify colleagues and collaborators in the same field of research.In April 2019, ResearcherID was integrated with Publons, a Clarivate Analytics owned platform, where researchers can track their publications, peer reviewing activity, and journal editing work. With ResearcherID now hosted on Publons researchers can keep a more comprehensive view of their research output and contributions in one place. This is particularly important for researchers in fields that predominantly use peer-reviewed conference articles (computer science) or in fields that focus on publishing books and chapters in books (humanities and disciplines in the social sciences).

ResearcherID and Publons are also integrated with Web of Science, and ORCiD, enabling data to be exchanged between these databases.ResearcherID has been criticized for being commercial and proprietary, but also praised as "an initiative addressing the common problem of author misidentification".


Zenodo is a general-purpose open-access repository developed under the European OpenAIRE program and operated by CERN.

It allows researchers to deposit data sets, research software, reports, and any other research related digital artifacts. For each submission, a persistent digital object identifier (DOI) is minted, which makes the stored items easily citeable.

International numbering standards
ISO standards by standard number


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