A DOI (digital object identifier) is a permanent identifier given to a Web file or other Internet document so that if its Internet address changes, users will be redirected to its new address. You submit a DOI to a centrally-managed directory and then use the address of that directory plus the DOI instead of a regular Internet address. The DOI system was conceived by the Association of American Publishers in partnership with the Corporation for National Research Initiatives and is now administered by the International DOI Foundation. Essentially, the DOI system is a scheme for Web page redirection by a central manager.
Initially, the only central directory is the one maintained by the DOI Foundation. It's envisioned, however, that other directories might be created and maintained, perhaps by each major industry. Here's what a typical DOI might look like:
10.1002/ISBNJ0-471-58064-3In this example, the "10.1002" identifies the directory and the part after the "/" is the rest of the DOI - in this case, the ISBN number of a particular book that has been published. The "-3" indicates a specific part or chapter in the book.
The DOI would be associated with a specific Web page or Uniform Resource Locator in the directory. If you wanted to link to the document in a Web page, you would link to this URL:
http://www.doi.org/10.1002/ISBNJ0-471-58064-3Here, "www.doi.org" happens to be the current and only directory manager. A user clicking on this link would be linking to the directory page which in turn would locate and send back the URL associated with the DOI. Assuming the directory was up-to-date, the page owner and the user could both be sure that the latest page would be returned.
Early users of the DOI system are principally major publishers with thousands of documents to keep track of, many available on the Web. Relocating files from time to time for such a large number of documents would require many link changes on the publisher's site and perhaps a redirection page for users. With the DOI system, any future location change will require only updating the central directory and will not affect other site's links (if they also use the DOI in their link).