May 18, 2022

An Introduction to the Crossref Open Citation Index (COCI)

From the OpenCitations Blog:

2018-07-12_16-55-39In this blog post, we introduce the Crossref Open Citation Index (COCI) [“300 million open citations created from the ‘Open’ references included in Crossref”], our first open citation index, in which we have applied the concept of citations as first-class data entities to index the contents of one of the major open databases of scholarly citation information, namely Crossref, and to render and make available this information in machine-readable RDF.


OpenCitations is a scholarly infrastructure organization dedicated to the promotion of semantic publishing by the use of semantic web (linked data) technologies, and engaged in advocacy for semantic publishing and open citations. It provides the OpenCitations Data Model and the SPAR (Semantic Publishing and Referencing) Ontologies for encoding scholarly bibliographic and citation data in RDF, and open software of generic applicability for searching, browsing and providing REST APIs over RDF triplestores. It has developed the OpenCitations Corpus (OCC) of open downloadable bibliographic and citation data recorded in RDF, and a system and resolution service for Open Citation Identifiers (OCIs), and it is currently developing a number of Open Citation Indexes using the data openly available in third-party bibliographic databases.


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About Gary Price

Gary Price ( is a librarian, writer, consultant, and frequent conference speaker based in the Washington D.C. metro area. Before launching INFOdocket, Price and Shirl Kennedy were the founders and senior editors at ResourceShelf and DocuTicker for 10 years. From 2006-2009 he was Director of Online Information Services at, and is currently a contributing editor at Search Engine Land.