This blog post is from Lettie Conrad and Michelle Urberg, cross-posted from the The Scholarly Kitchen.
As sponsors of this project, we at Crossref are excited to see this work shared out.
The scholarly publishing community talks a LOT about metadata and the need for high-quality, interoperable, and machine-readable descriptors of the content we disseminate. However, as we’ve reflected on previously in the Kitchen, despite well-established information standards (e.g., persistent identifiers), our industry lacks a shared framework to measure the value and impact of the metadata we produce.
When Crossref began over 20 years ago, our members were primarily from the United States and Western Europe, but for several years our membership has been more global and diverse, growing to almost 18,000 organizations around the world, representing 148 countries.
As we continue to grow, finding ways to help organizations participate in Crossref is an important part of our mission and approach. Our goal of creating the Research Nexus—a rich and reusable open network of relationships connecting research organizations, people, things, and actions; a scholarly record that the global community can build on forever, for the benefit of society—can only be achieved by ensuring that participation in Crossref is accessible to all.
In August 2022, the United States Office of Science and Technology Policy (OSTP) issued a memo (PDF) on ensuring free, immediate, and equitable access to federally funded research (a.k.a. the “Nelson memo”). Crossref is particularly interested in and relevant for the areas of this guidance that cover metadata and persistent identifiers—and the infrastructure and services that make them useful.
Funding bodies worldwide are increasingly involved in research infrastructure for dissemination and discovery.
Preprints have become an important tool for rapidly communicating and iterating on research outputs. There is now a range of preprint servers, some subject-specific, some based on a particular geographical area, and others linked to publishers or individual journals in addition to generalist platforms. In 2016 the Crossref schema started to support preprints and since then the number of metadata records has grown to around 16,000 new preprint DOIs per month.
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 lĂngua original, que passa a ser o inglĂŞs</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/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/</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/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.
