OpenCitations is a non-profit organization that publishes open citation data using semantic web and linked data technologies.
OpenCitations contains open, downloadable data and citation indexes in the RDF format of linked data. OpenCitations indexes contain information about the citation, citation date, and citation type. There are four indexes: the COCI index has over 1.4 billion open DOI-to-DOI citations from Crossref (as of December 2022); the DOCI index contains DOI-to-DOI citations from DataCite; the POCI index contains PMID-to-PMID citations from PubMed; and the CROCI index contains crowdsourced open citations.
The data can be queried using the SPARQL language of the Semantic Web, or via a machine-readable interface or search interface. The data enable, for example, the creation and utilization of knowledge graphs in the identification of research topics.
References:
Peroni, S., & Shotton, D. (2020). OpenCitations, an infrastructure organization for open scholarship. Quantitative Science Studies, 1(1), 428-444. doi:10.1162/qss_a_00023