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In the scholarly communications environment, the evolution of a journal article can be traced by the relationships it has with its preprints. Those preprint–journal article relationships are an important component of the research nexus. Some of those relationships are provided by Crossref members (including publishers, universities, research groups, funders, etc.) when they deposit metadata with Crossref, but we know that a significant number of them are missing. To fill this gap, we developed a new automated strategy for discovering relationships between preprints and journal articles and applied it to all the preprints in the Crossref database. We made the resulting dataset, containing both publisher-asserted and automatically discovered relationships, publicly available for anyone to analyse.

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 are delighted to announce the formation of a new Advisory Group to support us in improving preprint metadata. Preprints have grown in popularity over the last few years, with increasing focus brought by the need to rapidly disseminate knowledge in the midst of a global pandemic. We have supported metadata deposits for preprints under the record type ‘posted content’ since 2016, and members currently register a total of around 17,000 new preprints metadata records each month.

As part of our blog series highlighting some of the tools and services that use our API, we asked Michael Parkin—Data Scientist at the European Bioinformatics Institute—a few questions about how Europe PMC uses our metadata where preprints are concerned.

“Pre-prints” are sometimes neither Pre nor Print (c.f. https://doi-org.turing.library.northwestern.edu/10.12688/f1000research.11408.1, but they do go on and get published in journals. While researchers may have different motivations for posting a preprint, such as establishing a record of priority or seeking rapid feedback, the primary motivation appears to be timely sharing of results prior to journal publication.

So where in fact do preprints get published?

The Crossref graph of the research enterprise is growing at an impressive rate of 2.5 million records a month - scholarly communications of all stripes and sizes. Preprints are one of the fastest growing types of content. While preprints may not be new, the growth may well be: ~30% for the past 2 years (compared to article growth of 2-3% for the same period). We began supporting preprints in November 2016 at the behest of our members. When members register them, we ensure that: links to these publications persist over time; they are connected to the full history of the shared research results; and the citation record is clear and up-to-date.

Over the past few months we have been adding to the metadata and functionality of our REST API, Crossref’s public machine interface for the metadata of all 90 million+ registered content items. Much of the work focused on a review and upgrade of the API’s code and architecture in order to better support its rapidly growing usage. But we have also extended the types of metadata that the API can deliver.

We began accepting preprints as a new record type last month (in a category known as “posted content” in our XML schema). Over 1,000 records have already been registered in the first few weeks since we launched the service.

By extending our existing services to preprints, we want to help make sure that:

• links to these publications persist over time
• they are connected to the full history of the shared research
• the citation record is clear and up-to-date.

We’re excited to say that we’ve finished the work on our infrastructure to allow members to register preprints. Want to know why we’re doing this? Jennifer Lin explains the rationale in detail in an earlier post, but in short we want to help make sure that:

• links to these publications persist over time
• they are connected to the full history of the shared research results
• the citation record is clear and up-to-date

Doing so will help fully integrate preprint publications into the formal scholarly record.

We’re putting the final touches on the changes that will allow preprint publishers to register their metadata with Crossref and assign DOIs. These changes support Crossref’s CitedBy linking between the preprint and other scholarly publications (journal articles, books, conference proceedings). Full preprint support will be released over the next few weeks.