We’re happy to announce POCI, the OpenCitations Index of PubMed open PMID-to-PMID citations, an RDF dataset containing details of all the citations from publications bearing PubMed Identifiers (PMIDs) to other PMID-identified publications, harvested from the National Institutes of Health Open Citations Collection (NIH-OCC). The citations available in POCI are treated as first-class data entities, with accompanying properties including the citations timespan, modelled according to the OpenCitations Data Model.
Currently, POCI’s December 2022 release contains 717,654,703 citations from 26,024,862 bibliographic resources, and is based on the dump of NIH Open Citation Collection dated November 2022.
Each citation (i.e. an individual of the class
cito:Citation) is identified by an URL structured as follows:
Open Citation Identifiers
Each Open Citation Identifier
[[OCI]] has a simple structure: the lower-case letters “oci” followed by a colon, followed by two numbers separated by a dash (e.g. https://w3id.org/oc/index/poci/ci/01600102060800080706-016002060909030401), in which the first number identifies the citing work and the second number identifies the cited work.
For citations in which the citing and cited works are identified by PMIDs, which includes all the POCI citations, the OCI is created in the following manner, as explained more fully here. Each converted numeral part of OCI is prefixed by a
0160, which indicates that NIH is the supplier of the original metadata of the citation (as indicated at http://opencitations.net/oci).
OCIs can be resolved using the OpenCitations OCI Resolution Service.
Access to POCI data
All the data in POCI:
- can be retrieved using the POCI REST API;
- are available as dumps on Figshare in CSV, N-Triples and Scholix.
What is an Open Citation Index?
A citation index is a bibliographic index recording citations between publications, allowing the user to establish which later documents cite earlier documents. The current indexes available in OpenCitations are:
- COCI, open citations from Crossref, available at http://opencitations.net/index/coci;
- CROCI, the Crowdsourced Open Citations Index, available at http://opencitations.net/index/croci;
- DOCI, open citations from DataCite, available at http://opencitations.net/index/doci ;
- POCI, open citations from PubMed, available at https://opencitations.net/index/poci
All the OpenCitations Indexes have six characteristics in common, summarized here: https://opencitations.net/index