The present study, is the outcome of the project: “Technological Educational Institute of Athens Library: Development of Digital Services” funded by the EU Digital Plan 2009-2013 programme. One of the programme's mandates was the digital organization of the university archives within the collections of the institutional repository. Key element of the process was to secure subject access to archival data. This obligation led us to explore the potentials of ontologies. The domain of technological education was selected, as our institution is technological in nature and our archival material corresponded to the aforementioned subject area. Similar existing ontologies were examined and ideas on classes, subclasses and properties were taken into account. However, the complex structures of these ontologies with multiple calls on other existing controlled vocabularies did not accommodate our needs. As a result, a customized structure was designed and classes, subclasses and properties were defined. Subdomain analytical description and visualization are also part of this paper. Finally, discussion on ontology development issues and further research follow.