  OpenCitations is an infrastructure organization for open scholarship
dedicated to the publication of open citation data as Linked Open Data using
Semantic Web technologies, thereby providing a disruptive alternative to
traditional proprietary citation indexes. Open citation data are valuable for
bibliometric analysis, increasing the reproducibility of large-scale analyses
by enabling publication of the source data. Following brief introductions to
the development and benefits of open scholarship and to Semantic Web
technologies, this paper describes OpenCitations and its datasets, tools,
services and activities. These include the OpenCitations Data Model; the SPAR
(Semantic Publishing and Referencing) Ontologies; OpenCitations' open software
of generic applicability for searching, browsing and providing REST APIs over
RDF triplestores; Open Citation Identifiers (OCIs) and the OpenCitations OCI
Resolution Service; the OpenCitations Corpus (OCC), a database of open
downloadable bibliographic and citation data made available in RDF under a
Creative Commons public domain dedication; and the OpenCitations Indexes of
open citation data, of which the first and largest is COCI, the OpenCitations
Index of Crossref Open DOI-to-DOI Citations, which currently contains over 445
million bibliographic citations and is receiving considerable usage by the
scholarly community.
