5.5 Assigning DOIs to different formats (work vs. manifestation)
DOIs can be assigned to any type of intellectual property in any medium.
As a matter of current policy, the CrossRef DOI identifies the work, not its various potential
manifestations. This means separate DOIs are not assigned to each format of a given article. The print,
PDF, and HTML versions of the same article all share the same DOI. Different formats of the same article
can be pointed to from the response page to which the DOI resolves.
As the DOI and CrossRef systems develop -- for example to handle multiple resolution -- CrossRef's
policies will change accordingly.
5.6 Assigning multiple DOIs to republished works
CrossRef only permits registration of DOIs for Definitive Works
(or Versions of Record
, if not formally
) but not for Duplicative Works
, as defined in the CrossRef Glossary
. This means that only
original scholarly material, for which there is no actual DOI at the time of submission, and no expected
duplication in future, is admissible for CrossRef DOI registration. CrossRef does not permit multiple DOIs
to be assigned to certain closely related versions of a work, and hence does not support assignment of
DOIs to Pre-prints
of Definitive Works
or to the Personal Version
or a Self-archived Copy
. For the same reasons, materials for which DOI duplication can be reasonably
anticipated, such as an Authors Original Draft
of a work being prepared for publication, are not admissible
for CrossRef DOI registration.
CrossRef recognizes that a work may be legitimately republished, for example an article is published in a
topical journal and later in an annual summary. In such cases where the work may be cited in more than
one publication and the metadata for each appearance sufficiently differentiates them from one another,
multiple DOIs may be assigned where each DOI points to the different location. This approach maintains a
consistent linking experience for the reader who expects to find the cited item in a specific location. This
condition may apply in the following metadata differences:
Publication title and ISSN or ISBN must be different (language is a sufficient difference in
Volume/issue/page should be different with allowances for pure coincidence
Article number if used must be different
5.7 DOIs are not derivable
A DOI must not be considered derivable. That is, although a DOI may have been generated by the
registering publisher according to a formula or algorithm, a content item’s DOI must not be ‘reverse
engineered’ by re-constructing it according to the perceived algorithm. The CrossRef database is the
definitive reference for looking up DOIs registered by its members.
5.8 Allowed characters in a CrossRef DOI
According to the DOI specification, ANSI/NISO Z39.84- 2005, the suffix may be any alphanumeric string
However, experience has shown that certain characters cause difficulty when encountered by browsers.
Therefore CrossRef limits a DOI to only using the following characters:
"a-z", "A-Z", "0-9" and "-._;()/"
This rule was put into effect on January 1, 2009 and affects only the creation of new DOIs. Any DOI
created prior to this date will remain active and the CrossRef system will permit updates to the metadata for
6 CrossRef DOI deposit rules
6.1 Timely DOI deposit
DOIs must be deposited with CrossRef as soon as possible after online publication of the content.
While a DOI may have been created and assigned prior to publication, it is extremely important for the
reliability of the CrossRef resolution system that pre-publication DOIs remain for internal use only, and
that they are not displayed online or in print or distributed to secondary publishers prior to online
availability of the content.
Until a DOI and its metadata are deposited with CrossRef, the DOI will not work and the user will get an
error message. CrossRef regularly receives error reports of users trying to resolve DOIs that have not been
registered with CrossRef. If DOIs are not registered, they will not function.
It is not necessary to register DOIs separately with the IDF since this will be done automatically as part of
the CrossRef metadata submission process. For technical details on the metadata submission process,
please read the CrossRef Help Documentation - http://www.crossref.org/help/
6.2 Content published online ahead of print
Some providers publish DOIs to articles that are not yet published in print.
If content items are published online ahead of print publication, both versions must use the same DOI. The
DOI must be submitted to CrossRef as soon as possible after the content is published online. For this reason
a DOI suffix structure which includes pagination information in the DOI suffix could not be used reliably.
NOTE: the pagination information is a FIELD in the metadata. When the journal becomes available in
print, the DOI must be updated to include the additional metadata identifying the pagination.
One possible solution used by the American Physical Society is to do away with conventional pagination
and use an article identifier (APS uses a six digit number*) that appears in print and online in place of page
number. Other publishers may use the manuscript number of the article or a sequential number. Please refer
to the sample DOIs below.
* Page/article numbers with greater than 6 digits may be incompatible with some library systems.
6.3 The response page
When metadata and DOIs are deposited with CrossRef, the publisher must have active response pages in
place so that they can resolve incoming links.
As soon as metadata and DOIs are deposited in CrossRef, other users of the system will be able to retrieve
the DOIs and create links.
A minimal response page must contain a full bibliographic citation displayed to the user. A response page
without bibliographic information should never be presented to a user. Additionally, this response page
must display some mechanism by which the user can gain access to the full text. Access is completely
controlled by the publisher.
Most CrossRef publishers take users to the abstract page and permit authenticated users to access the full
text automatically. If the full text is available at no charge, users can access it immediately. Many
publishers also present unauthenticated users with pay-per-view options.
6.4 Multiple Resolution
Some CrossRef publishers offer access to their content through two or more resources. For example,
Wolters-Kluwer Health offers content to its journals through Ovid Web Gateway for institutional users, and
through its journal web sites for its society and individual members. CrossRef’s multiple resolution can be
managed in as follows :
1) The DOI link goes to an interim page that displays the link choices available for that DOI. The
Interim page must contain metadata describing the article.
Additional information on implementing multiple resolution can be found in CrossRef’s help
6.5 Metadata accuracy and updates
Metadata deposited with CrossRef must parse per a currently accepted XML schema
should abide by our Metadata Guidelines (http://www.crossref.org/02publishers/metadata_guidelines.html
Metadata should also pass semantic tests using a tool like the CrossRef data conformance checker at
. A general purpose parser that tests XML for being well
formed and valid is available at http://www.crossref.org/02publishers/55InstructionsForNewSchema.html
It is the responsibility of the publisher who owns a DOI to maintain the accuracy of its metadata and URL
in the CrossRef system. When a DOI is first created the publisher associated with the DOI’s prefix is
established as its owner. Unless an owner transfer process is performed the DOI remains owned by this
publisher even if the journal title is transferred to another publisher.
There is no charge for sending updates or revisions to previously submitted records or for performing
ownership transfers. Updates or revisions are complete replacements of metadata. Previously submitted
metadata for the record is not retained.
6.6 Further information
Rules about depositing content and what DOIs resolve to can be found in the Membership Qualifications
and Rules - http://www.crossref.org/08downloads/memberrules.pdf - and the PILA Membership
Agreement - http://www.crossref.org/08downloads/CR_MembershipAgreement.pdf.
7 Use and Display of DOIs
Every DOI is registered with at least one standard web URL. With the implementation of multiple
resolution, multiple URLs may be registered with each DOI. In the future, other data types may also be
registered with each DOI.
The core functionality of the DOI system is to resolve a DOI to the registered URL.
A DOI should be preceded by a lowercase "doi:". For example, the DOI 10.1006/jmbi.1998.2354 would be
displayed as doi:10.1006/jmbi.1998.2354. Using the lowercase DOI follows the URI specification
http://www.ietf.org/rfc/rfc2396.txt where FTP and HTTP are written as "ftp:" and "http:".
7.1 Resolution via the DOI Proxy
The DOI Proxy server - http://dx.doi.org/ - resolves DOIs. To resolve a DOI via a standard web hyperlink,
the DOI number itself should be attached to the address for the proxy server. For example, the DOI
10.1006/jmbi.1998.2354 would be made an active link as http://dx.doi.org/10.1006/jmbi.1998.2354.
The DOI Proxy is the definitive resolution service for DOIs and should be used for all DOI links. Although
websites provided by CrossRef members may resolve DOIs directly, this is not a recommended approach
as the DOI would cease to resolve if the content item is transferred to another location or publisher. By
using the DOI proxy, the DOI proxy will continue to resolve the DOI once its associated metadata is
updated with the new location.
7.2 HTTP encoding of DOIs
It is important to note that in this example of a URL, the DOI number 10.1006/jmbi.1998.2354
incorporated in a URL and transported by the HTTP protocol and therefore has to follow guidelines for
URIs. The syntax for URIs (a URL is a URI - http://www.ietf.org/rfc/rfc2396.txt) is much more restrictive
than the syntax for DOIs and some characters are reserved and will need encoding. For information on the
DOI Syntax and character issues see the NISO DOI Syntax standard -
In the future HTTP may no longer be the dominant protocol and systems will handle DOIs natively. This
means that doi:10.1006/jmbi.1998.2354 could be automatically resolved without the addition of the
http://dx.doi.org/. However, at the present time a DOI should be displayed as doi:10.1006/jmbi.1998.2354
and the DOI identifier itself can be an active link as in http://dx.doi.org/10.1006/jmbi.1998.2354.
7.3 Display of DOIs
The primary purpose of DOIs in the CrossRef system is to create persistent links to publishers’ content,
notably as reference links in electronic journal articles. DOIs for article references are retrieved from
CrossRef and added to references lists. How the links are actually added depends on the publisher's online
system. However, DOIs should be considered part of the basic bibliographic information for an article.
A DOI for a piece of content (article, book chapter, conference proceeding) should also be displayed in the
header information for the online AND print versions of the content (see Figure 2). The DOI can also be
used for citing the content. For example, many publishers instruct readers to use a DOI to cite an online
article published without a volume, issue or page number.
Figure 2 - DOI in Bibliographic Header
7.3.1 Displaying DOIs in print
A DOI assigned to the electronic version of an article should also be included in the header for the print
version of that article.
To make the DOI system transparent for readers, we recommend listing the DOI -- for example, as above in
Figure 2 -- as "doi:10.1006/jmbi.1998.2354". In order to show users how to resolve a DOI, it is possible to
have the DOI followed by: "available via http://dx.doi.org/". This will take users to a form where the DOI
can be entered and resolved
7.3.2 DOIs in citations
DOIs do not replace traditional bibliographic citations but are a very useful addition, especially if articles
are published online with volume, issue, and page numbers.
Further information for including DOIs in a variety of citation formats is available in the CrossRef
Reference Guidelines available at http://www.crossref.org/02publishers/guidelines.html
7.3.3 DOIs in citation export services
CrossRef has prepared separate documentation for publishers on how to integrate DOIs into their
"Download Citation"/"Export References" services. See
7.3.4 DOI as a reference link
CrossRef recommends that "CrossRef" be used as the display text for reference links. Some publishers use
"Article" or make the actual journal citation the link.
More information on this can be found in the "CrossRef Branding Guidelines"
7.3.5 Instructions for Authors
Publishers should include information about using DOIs in their instructions for authors.
For example, Nature has information for authors for its Advanced Online Publication
where articles are published online before
being assigned volume, issue, and page numbers.
Springer provides information to its authors on Online First http://www.springerlink.com
. Articles in
Online First are published before being assigned volume, issue, and page numbers, and DOIs are used to
cite the articles
DOIs, along with volume, issue and page numbers, should be part of the standard bibliographic
metadata for an article
DOIs should be displayed in bibliographic headers for online AND print articles
In citations, DOIs should be presented as doi:10.1038/35016083 (doi should be lowercase and no space
should be between the doi: and the start of the DOI string)
Wherever possible, the DOI should be an active link but the http://dx.doi.org/ need not be displayed
In a reference link to full text, CrossRef recommends that "CrossRef" be used as the display text for
the link. More information on this can be found in the "CrossRef Branding Guidelines"
8 CrossRef as an IDF Registration Agency
The IDF (International DOI Foundation) appoints Registration Agencies (RAs) to accept deposits of DOIs,
URLs, and metadata for a given Community of Interest.
CrossRef is an IDF RA for scholarly publishers and accepts deposits for journals, conference proceedings
and books. CrossRef holds the metadata associated with DOIs and deposits the DOIs and URLs in the
central DOI system. CrossRef also provides a retrieval system for the DOIs it registers.
CrossRef works with the IDF on general DOI policy and technical issues. Many CrossRef members are
also members of the IDF in order to participate in general DOI developments, however, CrossRef
membership is all that is necessary to deposit and retrieve DOIs. Separate IDF membership is not necessary
but does provide important support for the DOI system.
9 Examples of DOI structure
Crossref publishers have established many varying schemes for creating their DOI suffixes. Here is a list of
sample DOIs for some current CrossRef publishers:
Journal article 10.1006/jmbi.1998.2354
Four letter code for
journal, year of
acceptance and a
American Institute of
Journal article 10.1063/1.125173
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