Crossref & Unpaywall

This section describes the procedure used to integrate the contents from Crossref and Unpaywall in the OpenAIRE Graph.

Data acquisition

The dataset containing all the Crossref records is obtained via a complete data dump on a monthly basis. The Unpaywall dataset is no longer updated anymore but its latest snapshot (Dec 2021) is used to enrich the Crossref contents.

Process

In the following we describe the process applied to the Crossref & the Unpaywall contents.

Crossref filtering

Records in Crossref are ruled out according to the following criteria

• have blank title, examples:
  • 10.1093/rheumatology/41.7.837
  • 10.1093/qjmed/95.7.430
  • 10.1371/journal.pone.0171434.g005
• have one of the following publishers: "Test accounts", "CrossRef Test Account"
  • Examples from https://api.crossref.org/works?query.publisher-name=%22Test%20accounts%22
    • 10.1007/bf00344543
    • 10.1007/bf00186154
    • 10.1306/64ed947a-1724-11d7-8645000102c1865d
• have authors matching the following invalid names: ",", "none none", "none, none", "none &na;", "(:null)", "test test test", "test test", "test", "&na; &na"
  • Examples for "none" author from https://api.crossref.org/works?query.author=%22none%22
    • 10.4007/annals.2016.184.3.11
    • 10.4007/annals.2012.176.1.6
    • 10.2172/6393585
  • Examples for "test" author from https://api.crossref.org/works?query.author=%22test%22
    • 10.5116/ijme.54ca.a5ae
    • 10.5755/j01.ss.71.2.544
    • 10.5755/j01.ee.22.2.319
• have "Addie Jackson" as author and "Elsevier BV" as publisher (empirically we say they are test records)
  • Examples from https://api.crossref.org/works?query.author=Addie+Jackson&query.publisher-name=%22Elsevier%20BV%22
    • 10.2139/ssrn.2082156
    • 10.2139/ssrn.2202300
    • 10.2139/ssrn.2255657
• have not one of the following values in the field type : "book-section", "book", "book-chapter", "book-part", "book-series", "book-set", "book-track", "edited-book", "reference-book", "monograph", "journal-article", "dissertation", "other", "peer-review", "proceedings", "proceedings-article", "reference-entry", "report", "report-series", "standard", "standard-series", "posted-content", "dataset",
  • Example:
    • 10.1371/journal.pone.0171434.g005
    • 10.7554/elife.21052.049
    • 10.1371/journal.pcbi.1005379.s006

Records with type=dataset are mapped into OpenAIRE research products of type dataset. All others are mapped as OpenAIRE research products of type publication.

Mapping Crossref properties into the OpenAIRE Graph

Properties in OpenAIRE research products are set based on the logic described in the following table:

OpenAIRE Research Product field path	Crossref path(s)	Notes
id	doi	id in the form doi_________::md5(doi)
dateofcollection	indexed.datetime
lastupdatetimestamp	indexed.timestamp
type	type	Using the dnet:result_typologies vocabulary, we look up the instance.type synonym to generate one of the following main entities: publication dataset
originalId	doi, clinical-trial-number, alternative-id
pid		The scheme tells the type of PID, the value contains the actual value
pid.scheme		Default value: doi
pid.value	doi	The doi is normalised and lower-cased
maintitle	title
subtitle	subtitle
author	author	if available the sequence is mapped to rank and the ORCID is also mapped
author.name	author.given
author.surname	author.family
author.fullname	author.given author.family
author.rank		based on the order, starts from 1
author.pid		only if the ORCID is available
author.pid.id.scheme		Default 'pending_orcid' (meaning that it is not an id confirmed by ORCID)
author.pid.id.value	author.ORCID
author.pid.provenance.provenance		Default 'Harvested'
author.pid.provenance.trust		Default '0.9'
description	abstract
subject	subject	with classid='keywords', i.e. no controlled vocabularies for Crossref subjects
publicationdate	issued.datetime or, if not available, created.datetime
publisher	publisher
source	source	only if the record is not of type book
source	concatenation of container-title.head + "ISBN: " + ISBN.head	only if the record is of type book
container		It is set only for publications with information about the journal it was published in.
container.name	container-title.head
container.issnOnline	issn-type.value	if issn-type.type='electronic'
container.issnPrinted	issn-type.value	if issn-type.type='print'
container.vol	volume
container.sp	page	before '-'
container.ep	page	after '-'
instance		One instance is created with the DOI URL
instance.accessright		Values in instance.accessright.code and instance.accessright.label are set based on license and dateofacceptance: - UNKNOWN: if the license is blank - OPEN ACCESS: if the license is a CC license or an ACS license or an APA license (considered OPEN also by Unpaywall, see Unpaywall FAQ for details) or if OUP license, but only after 12 months from the publication date - EMBARGO: OUP license, before 12 months from the publication date - CLOSED: if there is a license not covered by the previous cases
instance.accessright.code		Code from the COAR vocabulary for access right
instance.accessright.label		One of: OPEN, RESTRICTED, CLOSED, EMBARGO
instance.accessright.scheme		Scheme that defines the code and label, i.e. the URL to the COAR vocabulary for access right
instance.accessright.openAccessRoute		only if instance.accessright.value = 'OPEN ACCESS'. Default is hybrid. The route is fixed in subsequent phases of DOIBoost, namely when intersecting with Unpaywall and patching the hostedby via DOAJ and the Gold-ISSN list.
instance.license	license.URL	If there is a license.content-version='vor', then this is used. Otherwise the first license entry is used.
instance.pid		The scheme tells the type of PID, the value contains the actual value
instance.pid.scheme		Default value: doi
instance.pid.value	doi	The doi is normalised and lower-cased
instance.publicationdate	issued.datetime or, if not available, created.datetime
instance.refereed		set to peerReviewed only if relation.has-review.id is not empty, UNKNOWN otherwise.
instance.type	subtype	mapped using the OpenAIRE vocabulary for research products typologies
instance.url	doi	Full URL of the DOI

All other fields of the Json schema not mentioned in the table contain empty values.

All the records from Crossref are related to the datasource with name=Crossref and id=openaire____::081b82f96300b6a6e3d282bad31cb6e2

Possible improvements:

• map clinical-trial-number and alternative-id in alternateIdentifiers?
• Verify if Crossref has a property for language, country, container.issnLinking, container.iss, container.edition, container.conferenceplace and container.conferencedate
• Different approach to set the refereed field and improve its coverage?

Map Crossref links to projects/funders

Links to funding available in Crossref are mapped as funding relationships (ResearchProduct -- isProducedBy -- Project) applying the following mapping:

Funder	Grant code	Link to
DOI: {10.13039/100010663, 10.13039/100010661, 10.13039/501100007601, 10.13039/501100000780, 10.13039/100010665} or name: 'European Union’s Horizon 2020 research and innovation program'	series of 4-9 digits in award	Link to H2020 project
DOI: {10.13039/100011199, 10.13039/100004431, 10.13039/501100004963, 10.13039/501100000780}	series of 4-9 digits in award	Link to FP7 project
DOI: 10.13039/501100000781 OR name: 'European Union's'	series of 4-9 digits in award	Link to FP7 or H2020 project
DOI: 10.13039/100000001	award	Link to NSF project
DOI: 10.13039/501100001665 OR name: {'The French National Research Agency (ANR)', 'The French National Research Agency'}	award	Link to ANR project
DOI: 10.13039/501100002341	award	Link to Academy of Finland project
DOI: 10.13039/501100001602	award, removing the initial 'SFI' if present	Link to SFI project
DOI: 10.13039/501100000923	award	Link to ARC project
DOI: 10.13039/501100000038	award ignore: we cannot map the project codes in Crossref to project codes in OpenAIRE	Link to NSERC (unidentified project)
DOI: 10.13039/501100000155	award ignore: we cannot map the project codes in Crossref to project codes in OpenAIRE	Link to SSHRC (unidentified project)
DOI: 10.13039/501100000024	award ignore: we cannot map the project codes in Crossref to project codes in OpenAIRE	Link to CIHR (unidentified project)
DOI: 10.13039/501100002848 OR name :'CONICYT, Programa de Formación de Capital Humano Avanzado'	award	Link to CONICYT project
DOI: 10.13039/501100003448	series of 4-9 digits in award	Link to GSRT project
DOI: 10.13039/501100010198	award	Link to SGOV project
DOI: 10.13039/501100004564	series of 4-9 digits in award	Link to MESTD project
DOI: 10.13039/501100003407	award	Link to MIUR project. Since OpenAIRE has a small subset of MIUR projects, a link to the MIUR funder (unidentified project) is also generated
DOI: {10.13039/501100006588, 10.13039/501100004488}	award, removing 'Project No' and 'HRZZ' prefix, if present	Link to HRZZ or MZOS project
DOI: 10.13039/501100006769	award	Link to Russian Science Foundation project
DOI: 10.13039/501100001711	award after '_' and before '/'	Link to SNSF project
DOI: 10.13039/501100004410	award	Link to TUBITAK project
DOI: 10.10.13039/100004440 or name: Wellcome Trust Masters Fellowship	award	Link to Wellcome Trust specific project and to the unidentified project.

Intersect Crossref with UnpayWall by DOI

The fields we consider from UnpayWall are:

• is_oa
• best_oa_location
• oa_status

The records of Crossref that intersect by DOI with UnpayWall records are enriched with one additional instance with the following properties:

OpenAIRE Research Product field path	Unpaywall field path	Notes
instance		created only if is_oa and a best_oa_location is available
instance.accessright		default value Open Access: we do not add instances if UnpayWall says there is no open version
instance.accessright.code		Open Access code from the COAR vocabulary for access right
instance.accessright.label		Always OPEN
instance.accessright.scheme		Scheme that defines the code and label, i.e. the URL to the COAR vocabulary for access right
instance.accessright.openAccessRoute	oa_status
instance.url	best_oa_location
instance.license	best_oa_location.license
instance.pid		The scheme tells the type of PID, the value contains the actual value
instance.pid.scheme		Default value: doi
instance.pid.value	doi	The doi is normalised and lower-cased

For the definition of UnpayWall's oa_status refer to the Unpaywall FAQ

The record will also feature a relation to the UnpayWall data source: name="UnpayWall", id=openaire____::8ac8380272269217cb09a928c8caa993.