The development version of the ontology is available at: https://purl.org/ontodt as well in the root folder. The folder also contains the definition of data mining specific datatypes which are used in the ontology of core data mining entities OntoDM https://github.com/panovp/ontodm-core .
This ontology is described in the paper https://link.springer.com/article/10.1007/s10618-014-0363-0 .
The ontology is also available on BioPortal https://bioportal.bioontology.org/ontologies/ONTODT