This work presents the use of ontologies as a way to tackle the problem of integration of qualification systems in order to enable the transparency and mobility of students at European level. For this, qualification systems at post-secondary non-academic levels of nine EU countries have been formalized in terms of profile, activities, competences, learning outcomes, etc., first using UML for a human-readable model and then using OWL for a machine-processable one. In addition, concrete qualification profiles have been used as a case study to check the models’ correctness.