Investigating Invalid DOIs in COCI v2
Authors: Shahidzadeh Nooshin , Cioffi Alessia , Moretti Arianna , Coppini Sara 
Published: April 2021

A preliminary note This protocol illustrates the workflow adopted within a scholarly research that operates within the OpenCitations environment, which is an independent infrastructure organization for open scholarship dedicated to the publication of open bibliographic and citation data by the use of Semantic Web (Linked Data) technologies. COCI is the OpenCitations Index of Crossref open DOI-to-DOI citations. Purpose The purpose of this research is to find the publishers responsible for the missing citations in COCI by sending incorrect metadata to Crossref, the publishers to whom such invalid citations point to and the number of previously invalid citations which are currently valid. The ultimate aim would be of contributing to the resolution of this type of problem in order to insert the citations now valid in COCI, and correct those still invalid always in order to increase the number of open citations available and indexed in the OpenCitations project. Study design/methodology In the beginning, we use an already generated CSV file, containing the valid citing DOIs and the invalid cited DOIs, which is available from Peroni, S. (2021). Citations to invalid DOI-identified entities obtained from processing DOI-to-DOI citations to add in COCI (1.0). Zenodo. https://doi.org/10.5281/ZENODO.4625300. These citations to invalid DOIs have been retrieved while processing Crossref data for adding open citations in COCI, but they have not been added in COCI since they point to a non-resolvable cited document. Two REST API services can be of help: the DOI REST API to check if the invalid cited DOI is now valid; and the Crossref REST API to retrieve the publisher from the prefix of the DOI, both for the cited publications and the citing ones. Findings In addition to collecting the names of the publishers involved in these missing citations, either as the publisher of the citing article or as the publisher of the cited article, which was sufficient to answer our research questions, we have decided to collect additional information that can help us to get a better picture of the situation. As regards the JSON file, we found for each individual publisher 1) the number of incorrect given citations metadata sent, and 2) the number of invalid citations received. On the other hand, as required by the initial research questions, we also extracted the total number of invalid citations that have since been corrected. Originality/value The results of this research may point us to publishers who generally send out incorrect citation metadata and, inversely, those who generally receive invalid citations. These findings can first of all raise awareness of the accuracy of certain publishing houses in managing their metadata (or lack thereof). Moreover, finding these trends and showcasing the labor of the corrections may lead to increasingly valid citations if the proper measures are taken. Research limitations/implications Based on the available data for the COCI, there may be a slight bias in our sample, causing some publishers to be incorrectly represented. Minimal bibliography on related projects Heibi, I., Peroni, S. & Shotton, D. Software review: COCI, the OpenCitations Index of Crossref open DOI-to-DOI citations.Scientometrics 121, 1213–1228 (2019). https://doi.org/10.1007/s11192-019-03217-6. Silvio Peroni, David Shotton (2020). OpenCitations, an infrastructure organization for open scholarship. Quantitative Science Studies, 1(1): 428-444. https://doi.org/10.1162/qss_a_00023. Peroni, S. (2021). Citations to invalid DOI-identified entities obtained from processing DOI-to-DOI citations to add in COCI (1.0). Zenodo. https://doi.org/10.5281/ZENODO.4625300.