This year, metadata development is one of our key priorities and we’re making a start with the release of version 5.4.0 of our input schema with some long-awaited changes. This is the first in what will be a series of metadata schema updates.
What is in this update?
Publication typing for citations
This is fairly simple; we’ve added a ‘type’ attribute to the citations members supply. This means you can identify a journal article citation as a journal article, but more importantly, you can identify a dataset, software, blog post, or other citation that may not have an identifier assigned to it. This makes it easier for the many thousands of metadata users to connect these citations to identifiers. We know many publishers, particularly journal publishers, do collect this information already and will consider making this change to deposit citation types with their records.
Every year we release metadata for the full corpus of records registered with us, which can be downloaded for free in a single compressed file. This is one way in which we fulfil our mission to make metadata freely and widely available. By including the metadata of over 165 million research outputs from over 20,000 members worldwide and making them available in a standard format, we streamline access to metadata about scholarly objects such as journal articles, books, conference papers, preprints, research grants, standards, datasets, reports, blogs, and more.
Today, we’re delighted to let you know that Crossref members can now use ROR IDs to identify funders in any place where you currently use Funder IDs in your metadata. Funder IDs remain available, but this change allows publishers, service providers, and funders to streamline workflows and introduce efficiencies by using a single open identifier for both researcher affiliations and funding organizations.
As you probably know, the Research Organization Registry (ROR) is a global, community-led, carefully curated registry of open persistent identifiers for research organisations, including funding organisations. It’s a joint initiative led by the California Digital Library, Datacite and Crossref launched in 2019 that fulfills the long-standing need for an open organisation identifier.
We began our Global Equitable Membership (GEM) Program to provide greater membership equitability and accessibility to organizations in the world’s least economically advantaged countries. Eligibility for the program is based on a member’s country; our list of countries is predominantly based on the International Development Association (IDA). Eligible members pay no membership or content registration fees. The list undergoes periodic reviews, as countries may be added or removed over time as economic situations change.
Last year, we introduced linking publication metadata to associated data and software when registering publisher content with Crossref Linking Publications to Data and Software. This blog post follows the “whats” and “whys” with the all-important “how(s)” for depositing data and software citations. We have made the process simple and fairly straightforward: publishers deposit data & software links by adding them directly into the standard metadata deposit via relation type and/or references. This is part of the **existing Content Registration ** process and requires no new workflows.
Relationships
Data & software citations are a valuable part of the “research article nexus”, comprised of the publication linked to a variety of associated research objects, including data and software, supporting information, protocols, videos, published peer reviews, a preprint, conference papers, etc. For all of these resources, we use relation types in the metadata deposit to “anchor” the article in the article nexus and link to it.
description of dataset or software. *Additional identifier types beyond those used for data or software are also accepted, including ARXIV, ECLI, Handle, ISSN, ISBN, PMID, PMCID, and UUID.
Crossref maintains an expansive set of relationship types to support the various resources linked in the research article nexus. For data and software, we recommend “isSupplementedBy” and “references” as relationship types in the metadata. Use the former if it was generated de novo as part of the research results. For those generated by another project and then reused, we recommend applying “references” in the relationship type. These were selected in consultation with DataCite and data working groups. They will provide the level of specificity requested by the community.
To illustrate how to represent the link within the metadata deposit, we offer two examples from two popular dataset identifiers, one for each of the relationship types.
Dataset
Snippet of deposit XML containing link
Dataset with DOI: Data from: Extreme genetic structure in a social bird species despite high dispersal capacity. Database: Dryad Digital Repository DOI:https://doi.org/10.5061/dryad.684v0
<program xmlns="http://www.crossref.org/relations.xsd"> <related_item> <description>Data from: Extreme genetic structure in a social bird species despite high dispersal capacity</description> <inter_work_relation relationship-type="isSupplementedBy" identifier-type="doi">10.5061/dryad.684v0</inter_work_relation> </related_item> </program>
Dataset with accession number: NKX2-5 mutations causative for congenital heart disease retain functionality and are directed to hundreds of targets Database: Gene Expression Omnibus (GEO) Accession number: GSE44902 URL:https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE44902
<program xmlns="http://www.crossref.org/relations.xsd"> <related_item> <description>NKX2-5 mutations causative for congenital heart disease retain and are directed to hundreds of targets</description> <inter_work_relation relationship-type="references" identifier-type="Accession">GSE44902</inter_work_relation> </related_item> </program>
In the examples above, the Dryad dataset was generated as part of the research published in an article. Hence, it contains the “isSupplementedBy” relationship type. The GEO dataset was reused by and referenced in a scholarly article published separate from the project that generated this dataset. Hence, it contains the “references” relationship type.
Both Crossref and DataCite employ this method of linking. Data repositories who 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).
References
Another mechanism for depositing data and software citations is to insert it into the manuscript’s references. Publishers then deposit it as part of the article’s references. To do so, publishers follow the general process for depositing references. (Visit Crossref’s Support page for step-by-step instructions.)
Publishers can deposit the full data or software citation as a unstructured reference. <citation key="ref=3"> <unstructured_citation>Morinha F, Dávila JA, Estela B, Cabral JA, Frías Ó, González JL, Travassos P, Carvalho D, Milá B, Blanco G (2017) Data from: Extreme genetic structure in a social bird species despite high dispersal capacity. Dryad Digital Repository. http://dx.doi.org/10.5061/dryad.684v0</unstructured_citation\> </citation> </citation_list>
Or they can employ any number of reference tags currently accepted by Crossref. Most do not readily suit datasets and software as the suite was originally established to match article and book references. This leaves out substantial metadata needed to identify and describe the dataset, however, if the resource does not have a DOI. <citation key="ref2"> <doi>10.5061/dryad.684v0</doi> <cYear>2017</cYear> <author>Morinha F, Dávila JA, Estela B, Cabral JA, Frías Ó, González JL, Travassos P, Carvalho D, Milá B, Blanco G</author> </citation> We are exploring the JATS4R recommendations while we consider expanding the current collection. We welcome additional suggestions from the community.
Precise, accessible links
Crossref’s infrastructure is setup to facilitate the flow of information about scholarly works across the research network. We maintain a fair degree of flexibility both in the structure and completeness of metadata deposited. The aim, though, is to make the links rich in metadata, accurate in associating literature to corresponding resource, and available to both human and machine consumers as per Principle #5 and #7 in the Joint Declaration of Data Citation Principles.
As with the other associated resources in the article nexus, we recommend depositing data/software links in the publication metadata via relationships. Publishers are free to do this on top of or independent of references. Relationship metadata offer a high degree of precision. References are a hodgepodge of various resources cited by the publication, including articles, books, media, blogs, reference materials, etc. and data citations are hard to isolate. Furthermore, the unstructured, “spaghetti string” text is difficult for systems to parse and extract specific information.
With relationship metadata, data and software resources are expressly designated. We obtain a more accurate link that specifies identifier type and explicitly identifies data generated as part of the research shared in the paper or as reuse of existing data). The richer metadata contained here enables consumers to conduct powerful queries based on different attributes (identifier type, description, relationship), taking data discovery and mining to the next level.
Furthermore, relationships are important for achieving full accessibility of data and software citations. Access to references is based on publisher permission so not all data citations can be shared (excluding DataCite DOIs). In contrast, all links deposited via relationships are publicly available.
Publishers play an important role in supporting research validation and reproducibility. Data & software citation is a basic part of of this practice, and instrumental in enabling the reuse and verification of these research outputs, tracking their impact, and creating a scholarly structure that recognizes and rewards those involved in producing them. For the full scoop of how to deposit (i.e., technical details and more), we encourage you to reference the Crossref Data & Software Citations Deposit Guide and contact us (support@crossref.org) with questions or feedback.
