Crossref is a membership organisation, and it’s the global community of members that creates the Research Nexus together. Meeting our community locally is a highlight and an important learning experience. This year, we started by connecting with a growing community in Accra, Ghana - our first in-person event in the country included in our GEM program. From 14 members in 2023 to 31 in 2025, our community in Ghana is blooming.
At its core, Crossref Accra 2025 was about showing up for the community in Ghana - listening, learning, and building together. On the 20th of March, we welcomed 66 participants: journal editors, university staff, librarians, and researchers. People who are doing the real work of making scholarly publishing happen in the region.
In 2022, we set out to update our DOI display guidelines with the intention to adopt the proposals in 2025. It’s important to note from the outset that we are not mandating any immediate changes to the DOI display guidelines. Instead, we are working with our community to co-create a solution that addresses the diverse needs of all users, rather than imposing technical changes that may not suit everyone.
Sponsors make Crossref membership accessible to organizations that would otherwise face barriers to joining us. They also provide support to facilitate participation, which increases the amount and diversity of metadata in the global Research Nexus. This in turn improves discoverability and transparency of scholarship behind the works.
We are looking for an organization to perform an audit of, and propose changes to, the structure and information architecture underlying our website, with the aim of making it easier for everyone in our community to navigate the website and find the information they need.
Proposals will be evaluated on a rolling basis. We encourage submissions by May 15, 2025.
We maintain an expansive set of relationship types to support the various content items that a research object, like a journal article, might link to. For data and software, we ask you to provide the following information:
identifier of the dataset/software
identifier type: DOI, Accession, PURL, ARK, URI, Other (additional identifier types are also accepted beyond those used for data or software, including ARXIV, ECLI, Handle, ISSN, ISBN, PMID, PMCID, and UUID)
relationship type: isSupplementedBy or references (use the former if it was generated as part of the research results)
description of dataset or software
We and DataCite both use this kind of linking. Data repositories which register their content with DataCite follow the same process and apply the same metadata tags. This means that we achieve direct data interoperability with links in the reverse direction (data and software repositories to journal articles).
The possible relationship types between content items can be as varied as the items themselves. We use a controlled vocabulary to define these relationships, in order to construct an orderly mapped network of content.
This is achieved by (i) an implicit approach where the relation type is a function of a specific service and is declared in the structure of the deposited XML, and (ii) in an explicit approach where the relation type is selected as a value within the deposited metadata.
Reference linking and Cited-by: implicitly creates cites and isCitedBy relationships between a content item and the items in its bibliography
Crossmark: explicit creation of update relations between an item and other items that materially affect it (for example, a retraction)
Funding data: implicit creation of isFundedBy and hasAward relationships between an item and the funding source that supported the underlying research
Linked clinical trials: implicit creation of a belongsTo relationship between and item and a registered clinical trial
Components: implicit creation of a isChildOf relationship between an item and its elemental parts that are assigned their own DOI (limited parent relation typing)
General typed relations: explicitly typed relation between an item with a Crossref DOI and an item with one of several possible identifiers.
Relationship types for associated research objects: intra-work (within a work)
Description
Reciprocal relationship types
Expression
isExpressionOf, hasExpression
Format
isFormatOf, hasFormat
Identical
isIdenticalTo
Manifestation
isManifestationOf, hasManifestation
Manuscript
isManuscriptOf, hasManuscript
Preprint
isPreprintOf, hasPreprint
Replacement
isReplacedBy, Replaces
Translation
isTranslationOf, hasTranslation
Variant
isVariantFormOf, isOriginalFormOf
Version
isVersionOf, hasVersion
Relationship types for associated research objects: inter-work (between works)
Description
Reciprocal relationship types
Basis
isBasedOn, isBasisFor
Comment
isCommentOn, hasComment
Continuation
isContinuedBy, Continues
Derivation
isDerivedFrom, hasDerivation
Documentation
isDocumentedBy, Documents
Funding
finances, isFinancedBy
Part
isPartOf, hasPart
Peer review
isReviewOf, hasReview
References
references, isReferencedBy
Related material, such as a protocol
isRelatedMaterial, hasRelatedMaterial
Reply
isReplyTo, hasReply
Requirement
requires, isRequiredBy
Software compilation
isCompiledBy, compiles
Supplement, such as a dataset generated as part of research results
isSupplementTo, isSupplementedBy
General typed relations
This service allows for the creation of a typed relationship between an item with a Crossref DOI and another content item. The other item may be represented by another Crossref DOI, a DOI from some other Registration Agency, or an item not identified with a DOI. When DOIs are used, the deposit process will fail if the DOI does not exist. Non-DOI identifiers are not verified.
When DOIs are used, a bidirectional relation is automatically created by us when a relation is created in the deposit of one item in a pair. The DOI with metadata creating the relation is said to be the claimant, the other item does not need to have its metadata directly contain the relationship.
Example: translated article
A single journal article is published in two languages with each being assigned its own DOI. In this example, both are published in the same journal. The original language instance has metadata that contains no indication of the translation instance. The alternative language instance includes in its metadata a relation to the original language instance. Here is a screenshot of the relevant section in the code. Please refer to the code snippet below to see it in context.
<journal_article publication_type="full_text">
<titles>
<title>Um artigo na lÃngua original, que passa a ser o inglês</title>
<original_language_title language="en">An article in its original language which happens to be English</original_language_title>
</titles>
<contributors>
<person_name sequence="first" contributor_role="author">
<given_name>Daniel</given_name>
<surname>Stepputtis</surname>
<ORCID authenticated="true">http://orcid.org/0000-0003-4824-1631</ORCID>
</person_name>
</contributors>
<publication_date media_type="online">
<month>02</month>
<day>28</day>
<year>2013</year>
</publication_date>
<program xmlns="https://www-crossref-org.turing.library.northwestern.edu/relations.xsd">
<related_item>
<description>Portuguese translation of an article</description>
<intra_work_relation relationship-type="isTranslationOf" identifier-type="doi">10.5555/original_language</intra_work_relation>
</related_item>
</program>
<doi_data>
<doi>10.5555/translation</doi>
<resource>https://www-crossref-org.turing.library.northwestern.edu/</resource>
</doi_data>
</journal_article>
Example: book review
This example has a book review published as an article in the journal The Holocene. The article’s title, taken from the publisher’s site is “Book Review: Understanding the Earth system: compartments, processes and interactions” where this book has the DOI https://doi-org.turing.library.northwestern.edu/10.1007/978-3-642-56843-5.
A: The current metadata for the review article gives no indication of the actual book being reviewed:
An article with a Crossref DOI identifies that data represented by a DataCite DOI was used in the research and was mentioned in the article’s acknowledgment section.
