Earlier this year, Ginny posted an exciting update on Crossref’s progress with adopting ROR, the Research Organization Registry for affiliations, announcing that we’d started the collection of ROR identifiers in our metadata input schema. 🦁
The capacity to accept ROR IDs to help reliably identify institutions is really important but the real value comes from their open availability alongside the other metadata registered with us, such as for publications like journal articles, book chapters, preprints, and for other objects such as grants.
Event Data is our service to capture online mentions of Crossref records. We monitor data archives, Wikipedia, social media, blogs, news, and other sources. Our main focus has been on gathering data from external sources, however we know that there is a great deal of Crossref metadata that can be made available as events. Earlier this year we started adding relationship metadata, and over the last few months we have been working on bringing in citations between records.
Tl;dr: Metadata for the (currently 26,000) grants that have been registered by our funder members is now available via the REST API. This is quite a milestone in our program to include funding in Crossref infrastructure and a step forward in our mission to connect all.the.things. This post gives you all the queries you might need to satisfy your curiosity and start to see what’s possible with deeper analysis. So have the look and see what useful things you can discover.
Update on the outage of October 6th. In my blog post on October 6th, I promised an update on what caused the outage and what we are doing to avoid it happening again. This is that update.
Crossref hosts its services in a hybrid environment. Our original services are all hosted in a data center in Massachusetts, but we host new services with a cloud provider. We also have a few R&D systems hosted with Hetzner.
The collective power of our members’ metadata is available to use through a variety of tools and APIs—allowing anyone to search and reuse the metadata in sophisticated ways.
Members register content with us to let the world know it exists. They send us information called metadata which we collect and store in a standard way. The metadata includes a Digital Object Identifier (DOI) in each record, which links to the content even if it moves to a new website. We make this metadata openly available via our APIs, which means people and machines can incorporate it in their research tools and services. Metadata does not include the full-text of the content itself. While we collect and distribute metadata, we do not change members' metadata. Learn more about the metadata each member is depositing with us using our Participation Reports.
Manuscript tracking services, search services, bibliographic management software, library systems, author profiling tools, specialist subject databases, scholarly sharing networks - all of these (and more) incorporate scholarly metadata into their software and services. They use our free APIs to help them get the most complete, up-to-date set of metadata from all of our publisher members. And of course, members themselves are able to use our free APIs too.
Watch the introductory animation in your language:
If you’d like to share a case study for how you use Crossref metadata, and be featured on our blog, please contact us.
Using content negotiation
The APIs listed here provide metadata in a variety of representations (also known as output formats). If you want to access our metadata in a particular representation (for example, RDF, BibTex, XML, CSL), you can use content negotiation to retrieve the metadata for a DOI in the representation you want. Content negotiation is supported by a number of DOI registration agencies including Crossref, DataCite, and mEDRA.
Obligations and fees for metadata retrieval
It is important that members understand that metadata is used by other software and services in the Crossref community. We encourage members to submit as much metadata as possible so that our APIs can include and deliver rich contextual information about their content.
If you’re using the public REST API, it is optional but encouraged to include your email address in header requests as this puts your query into the “polite” pool which has priority processing. Learn more about our REST API etiquette.
Simple Text Query is a tool designed to allow anyone to look up DOIs for multiple references. As such it’s particularly useful for members who want to link their references. Members can even use this tool to add linked references to their metadata.
How to participate - APIs for machines
We have a number of APIs for accessing metadata. There is one general-purpose API and several specialized ones. The specialized APIs are designed for our members so that they can manage their metadata or they are APIs based on standards that are popular in the community.
This API outputs in XML and uses a standard popular in the library community to harvest metadata. The OAI-PMH API is optimized to return a list of results matching the query parameters (such as publication year). The OAI-PMH API is included in the Metadata Plus service.
We support a range of tools and APIs to help you get metadata (and identifiers) out of our system. Some query interfaces will return only one match, and only if fairly strict requirements are met. These interfaces may be used to populate citations with persistent identifiers. Other interfaces will return a range of results and may be used to retrieve a variety of metadata records or match metadata when metadata, DOIs, or other identifiers (such as ORCID iD, ISSN, ISBN, funder identifier) are provided.
Metadata Search - any results containing the entered search terms will be returned. Search by full citation, title (or fragments of a title), authors, ISSN, ORCID, DOI (to retrieve metadata) and more.
Simple Text Query - cut-and-paste your reference list into the form and retrieve exact DOI matches.
REST API - a RESTful API that supports a wide range of facets and filters. By default, results are returned in JSON, and returning results in XML is an option. This API is currently publicly available (no account or token required), but there is a paid Metadata Plus service available on a token for those who require guaranteed service levels
XML API - the XML API will return a DOI that best fits the metadata supplied in the query. This API is suitable for automated population of citations with DOIs as the results are accurate and do not need evaluation. This API is available to members, or by supplying an email address.
OpenURL - used mostly by libraries but also available to members, or by providing an email address. Learn more about OpenURL access.
OAI-PMH - as well as a free public list option, we provide a subscription-only OAI-PMH interface that may be used to retrieve sets of metadata records (subscribers only)
GetResolvedRefs - retrieve DOIs matched with deposited references (members only)