Digital object identifier

A digital object identifier, or DOI name, is a unique label for a computer readable object (text document, electronic image, video, etc.) that can be found on the World Wide Web. 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.

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, over 50 million objects were registered at the end of June 2011.

Examples

 * The DOI&reg; 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.