Latest blog posts
Martyn Rittman
2024 November 15

Research Integrity Roundtable 2024

For the third year in a row, Crossref hosted a roundtable on research integrity prior to the Frankfurt book fair. This year the event looked at Crossmark, our tool to display retractions and other post-publication updates to readers. Since the start of 2024, we have been carrying out a consultation on Crossmark, gathering feedback and input from a range of members. The roundtable discussion was a chance to check and refine some of the conclusions we’ve come to, and gather more suggestions on the way forward.

...Find out more
Dominika Tkaczyk
2024 November 06

How good is your matching?

In our previous blog post in this series, we explained why no metadata matching strategy can return perfect results. Thankfully, however, this does not mean that it’s impossible to know anything about the quality of matching. Indeed, we can (and should!) measure how close (or far) we are from achieving perfection with our matching. Read on to learn how this can be done! How about we start with a quiz? Imagine a database of scholarly metadata that needs to be enriched with identifiers, such as ORCIDs or ROR IDs.

...Find out more
Kornelia Korzec
2024 October 28

Update on the Resourcing Crossref for Future Sustainability research

We’re in year two of the Resourcing Crossref for Future Sustainability (RCFS) research. This report provides an update on progress to date, specifically on research we’ve conducted to better understand the impact of our fees and possible changes. Crossref is in a good financial position with our current fees, which haven’t increased in 20 years. This project is seeking to future-proof our fees by: Making fees more equitable Simplifying our complex fee schedule Rebalancing revenue sources In order to review all aspects of our fees, we’ve planned five projects to look into specific aspects of our current fees that may need to change to achieve the goals above.

...Find out more
Lucy Ofiesh
2024 September 24

Meet the candidates and vote in our 2024 Board elections

On behalf of the Nominating Committee, I’m pleased to share the slate of candidates for the 2024 board election. Each year we do an open call for board interest. This year, the Nominating Committee received 53 submissions from members worldwide to fill four open board seats. We maintain a balanced board of 8 large member seats and 8 small member seats. Size is determined based on the organization’s membership tier (small members fall in the $0-$1,650 tiers and large members in the $3,900 - $50,000 tiers).

...Find out more
  • Menu
search

Documentation

OAI-PMH

We operate an OAI-PMH service for the distribution of metadata in XML. This system is based on the OAI-PMH version 2 repository framework and implements the interface as documented here.

The service interface can be used in different ways by public metadata users, Metadata Plus subscribers, and Crossref members.

  • Public metadata users: we allow public access to two OAI verbs, ListSets and ListIdentifiers, which allow for discovery of available information.
  • Metadata Plus subscribers: access to OAI verbs GetRecord and ListRecords require a subscription to our Metadata Plus service. Users of this service are provided with tokens to identify them. Tokens are placed in HTTPS Authorization headers as:
Crossref-Plus-API-Token: Bearer FullTokenHere
  • Crossref members may also use OAI-PMH to retrieve their deposited metadata using our deposit harvester using their member account.

Set hierarchy

We support selective harvesting according to sets defined by the hierarchy of publisher and title. Setspecs are formatted as follows:

  • record type:prefix:pubID (learn more about publication IDs) (for example: J:10.1002:4 = Journal content by the publisher Wiley, journal title Applied Organometallic Chemistry)
  • record type:prefix (for example: J:10.1002, journals owned by publisher Wiley)

The from and until dates in a request capture when a record was deposited or updated, not the published date of the item. This means a request for records from yesterday through today will return all records added or changed between then and now, regardless of the publication dates included in the records.

Set record types are:

  • J for journals
  • B for books, conference proceedings, dissertations, reports, and datasets
  • S for series

The default set for both ListIdentifiers and ListRecords is J (journals). A set (B for books or conference proceedings, S for series) must be specified to retrieve non-journal data.

With the ListSets request the set parameter is optional. Leaving off the set parameter will return only journal data which includes a list of publishers, their journal titles, and each year of publication for which we have metadata records.

With the ListIdentifiers request the set, from, and until parameters are optional. The from and until parameters are used to specify dates when the DOIs were registered with us and not the publication date.

Examples of requests

Request a list of DOIs registered since 2010-08-11:

https://0-oai-crossref-org.libus.csd.mu.edu/oai?verb=ListIdentifiers&metadataPrefix=cr_unixsd&from=2010-08-11

Request all journal sets:

https://0-oai-crossref-org.libus.csd.mu.edu/oai?verb=ListSets&set=J

Request all sets with record type ‘B’:

https://0-oai-crossref-org.libus.csd.mu.edu/oai?verb=ListSets&set=B

Request records for title ‘98765’ with prefix 10.1234 registered or updated on 2017-07-06:

https://0-oai-crossref-org.libus.csd.mu.edu/oai?verb=ListRecords&metadataPrefix=cr_unixsd&set=J:10.1234:98765&from=2017-07-06&until=2017-07-06

Best practice for performance

We allow 3 concurrent initial OAI-PMH requests per user. There is no concurrency limit for follow-on requests (requests made with a resumption token). Due to the size of the repository, it is highly discouraged to perform a ListRecords action for the entire collection.

The best possible performance is had by requesting the changes made to one publication on a given date, such as:

https://0-oai-crossref-org.libus.csd.mu.edu/oai?verb=ListRecords&metadataPrefix=cr_unixsd&set=J:10.1234:98765&from=2017-07-06&until=2017-07-06

If you are harvesting a large amount of data and run up against our 3 concurrent initial request limitation, it is recommended that you request data by prefix for a short time-frame (days to a week). For example, this request will give you all journal records owned by prefix 10.1234 registered or updated between 2017-07-06 and 2017-07-09 :

https://0-oai-crossref-org.libus.csd.mu.edu/oai?verb=ListRecords&metadataPrefix=cr_unixsd&set=J:10.1234&from=2017-07-06&until=2017-07-09

Using resumption tokens with OAI-PMH

Many OAI requests are too big to be retrieved in a single transaction. If a given response contains a resumption token, you must make an additional request to retrieve the rest of the data. Resumption tokens remain viable for 48 hours.

The resumption token includes an expiry date of 48 hours:

<resumptionToken expirationDate="2015-10-28T00:00:00">c6cafedc-ef48-42a3-847c-b682dc58b617</resumptionToken>

The token should be appended to the end of the next request:

https://0-oai-crossref-org.libus.csd.mu.edu/oai?verb=ListSets&set=J:10.1007&resumptionToken=c6cafedc-ef48-42a3-847c-b682dc58b617

Snapshots - part of our Metadata Plus service

Metadata Plus snapshots provide access to our 160,104,382-plus metadata records in a single file, providing an easy way to retrieve an up-to-date copy of our records. Snapshots are available for Metadata Plus service users.

The files are made available via a /snapshots route in the REST API which offers a compressed .tar file (tar.gz) containing the full extract of the metadata corpus in either JSON or XML formats.

OAI-PMH example files

An example application for harvesting Crossref OAI data

Example ListIdentifiers, ListSets, and ListIdentifiers responses

Page owner: Patrick Polischuk   |   Last updated 2020-April-08