We’re excited to introduce DOCI, the OpenCitations Index of Datacite open DOI-to-DOI citations, a new tool containing citations derived from publications bearing DataCite DOIs to other DOI-identified publications, harvested from DataCite. The citations available in DOCI are treated as first-class data entities, with accompanying properties including the citations timespan, modelled according to the OpenCitations Data Model.
Currently, DOCI’s December 2022 release contains 169,822,752 citations from 1,753,860 citing resources, and is based on the last dump of DataCite dated 22 October 2021 provided by the Internet Archive.
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://opencitations.net/index/doci/ci/080010504060836132137200707121027-080010504060836161221130313.html), 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 DOIs, which includes all the DOCI citations, the OCI is created in the following manner, as explained more fully here. Each case-insensitive DOI is first normalized to lower case letters. Then, after omitting the initial
doi:10. prefix, the alphanumeric string of the DOI is converted reversibly to a pure numerical string using the simple two-numeral lookup table for numerals, lower case letters and other characters presented at https://github.com/opencitations/oci/blob/master/lookup.csv. Finally, each converted numeral is prefixes by a
080, which indicates that DataCite 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 DOCI data
All the data in DOCI:
- can be queried by means of the OpenCitations Indexes SPARQL endpoint;
- can be retrieved by using the DOCI REST API;
- are available as dumps on Figshare in CSV, N-Triples and Scholix.
More information is available at https://opencitations.net/index/doci.
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 .
All the OpenCitations Indexes have six characteristics in common, summarized here: https://opencitations.net/index