Extract single files from issue.xml created from the Native XML Plugin in OJS 3.x. See https://docs.pkp.sfu.ca/admin-guide/en/data-import-and-export.
The file structure
extracted/
Bd. 4,1 (2018)/
47289/
41867_153991_DCO 4,1 (2018) Schubert.pdf
48489.xml
48490/
41863_153984_DCO 4,1 (2018) KrämerF.pdf
48490.xml
47289/
41868_153992_Raunig DCO (2018).pdf
47289.xml
48491/
41870_153994_DCO 4,1 (2018) Rehbein.pdf
48491.xml
48492/
41866_153990_DCO 4,1 (2018) Schilz.pdf
48492.xml
48493/
41865_153988_DCO 4,1 (2018) Bubenhofer F.pdf
48493.xml
cover_issue_3911_de_DE.jpg
3911-784-PB.pdf
source/
dco_4_1.xml
Due to limitation of filesize on github there is only one XML-file as example. Usually the DCO issue files are up to 300 MB. The plugin exports not only all relevant metadata, it includes all article files (HTML, PDF, etc.) and suplementary files embedded within the XML document in Base64 encoding.
Own XML with URLs of all published DCO issues.