This page is a legacy page (not linked anymore from the official website) that describes CROCI. Since October 2023, all the citation data collected previously in different OpenCitations Indexes have been moved (and deduplicated) in the new citation collection, i.e. the OpenCitations Index.
CROCI, the Crowdsourced Open Citations Index, is a new OpenCitations Index containing citations deposited by individuals, identified by ORCiD identifiers, who have a legal right to publish them under a CC0 public domain waiver. These citations are treated as first-class data entities, with accompanying properties including the citations timespan, modelled according to the OpenCitations Data Model. For an in-depth description of CROCI, see:
Ivan Heibi, Silvio Peroni, David Shotton (2019). Crowdsourcing open citations with CROCI - An analysis of the current status of open citations, and a proposal. In Proceedings of the 17th International Conference on Scientometrics and Informetrics (ISSI 2019). http://arxiv.org/abs/1902.02534
CROCI was first created and released on 3 March 2019.
Each citation (i.e. an individual of the class cito:Citation) is identified by an URL structured as follows: https://w3id.org/oc/index/croci/ci/[[OCI]].
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/croci/ci/05001000106361937321411281422370200010237000837000001-050010008073602000009020002), 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 COCI 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 050
, which indicates that CROCI 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.
All the data in CROCI:
can be queried by means of the OpenCitations Indexes SPARQL endpoint;
can be retrieved by using the CROCI REST API;
can be searched by using the OpenCitations Indexes Search Interface.