  In this paper we present a publicly-available maintenance ontology
(Iof-maint). Iof-maint is a modular ontology aligned with the Industrial
Ontology Foundry Core (IOF Core) and contains 20 classes and 2 relations. It
provides a set of maintenance-specific terms used in a wide variety of
practical data-driven use cases. Iof-maint supports OWL DL reasoning, is
documented, and is actively maintained on GitHub. In this paper, we describe
the evolution of the Iof-maint reference ontology based on the extraction of
common concepts identified in a number of application ontologies working with
industry maintenance work order, procedure and failure mode data.
