The use of ontologies in information systems for engineering applications calls for ontologies representing experts’ knowledge in a principled and robust manner. The work we present in the paper brings together, on the one hand, two ontologies developed for the engineering domain, namely PPDRC and MIRC and, on the other hand, the DOLCE foundational ontology. The former two have been developed by taking DOLCE as reference model for distinguishing between the high-level entities they quantify over. However, the relation with DOLCE calls for improvements. The ultimate purpose of the paper is to show how the conceptual transparency of domain ontologies can be enhanced by (properly) using a foundational ontology.