Digital object identifier

A digital object identifier, or DOI, is a unique label for a computer readable object (text document, electronic image, video, etc.) on the World Wide Web. Use of a DOI link, as opposed to the direct URL where an object currently resides, is the preferred way to linking to scholarly journal articles on the web, because web URL's can change over time but the DOI will always be kept updated to point to the current location of the article.

A DOI link is actually a URL calling a web service provided by https://www.doi.org/. The characters tacked onto the end of the URL are a unique identifier for that specific digital object. When the user clicks on a DOI link, the web service is invoked and it does a lookup in the DOI central database and then redirects the user to the current web URL of the object being requested. The DOI name stays with the object even when the digital object is transferred to another owner and/or another website.

An object can be identified at any level of composition. For instance, a DOI name can identify a journal, an individual issue of a journal, an individual article in a journal, or a single figure in an article. Metadata can be added to or updated over time to further describe the object identified.

The structure of the DOI name is 10.xxxx/yyyy, where part of the prefix (10.) indicates that a DOI name is following. The remaining part of the prefix, the digital string xxxx, identifies the publisher that assigned the DOI name and put the object on the web. The suffix yyyy is arbitrary, both of length and content, and can be chosen freely by the publisher. In particular, yyyy may contain identifiers, such as the ISBN of an existing book.

A digital object can be retrieved from the web by the URL:  /dx.doi.org/10.xxxx/yyyy. The website /dx.doi.org/ resolves the DOI name 10.xxxx/yyyy, that is, it finds the location of the object and determines what is to be done with it. For instance, if the object is video it will play it, if it is a web page it will redirect the browser, etc.

A publisher (registrant, identified by the string xxxx) must be registered by a DOI registration agency (RA). An RA is appointed by the International DOI Foundation (IDF), which was created in 1998 as a non-profit organization. An RA is responsible for:

• issuing DOI numbers to the publishers;
• maintaining the database that stores DOI names;
• ensuring that the database remains interconnected with the databases maintained by other RAs.

The number of objects with a DOI name is growing quickly, 40 million objects were registered at the end of June 2009.

Examples

• The DOI^® Handbook can be retrieved from http://dx.doi.org/10.1000/182.
• An article (arbitrarily picked for this example) from Science Magazine is retrieved by http://dx.doi.org/10.1126/science.318.5856.1571.

CZ template

The Citizendium cite book template has an entry doi. For example,

{{cite book
  | last = Mumford
  | first = David
  | authorlink = David Mumford
  | title = The Red Book of Varieties and Schemes
  | publisher = [[Springer-Verlag]]
  | series = Lecture notes in mathematics 1358
  | year = 1999
  | doi = 10.1007/b62130
  | isbn = 354063293X }}

The in-line expansion of this template:

Mumford, David (1999). The Red Book of Varieties and Schemes. Springer-Verlag. DOI:10.1007/b62130. ISBN 354063293X. 

gives a clickable link to the digital object with DOI name: 10.1007/b62130.