[EN] The aim of this work is to help university applicants in their transition phase from high-school to tertiary education starting with their first life-long decision concerning their choice of the field of study. The construction of the decision support system has evolved into an ontology-based model. The model, as well as the decision making rules, have been formulated based on the research study of the cohort of 69000 students of the University of Alicante between 2010 and 2018. The educational and psychological processes have been studied in order to identify the pivot moments and the factors that may lead to an adequate decision making or to an objectively wrong decision which eventually ends up in a drop-out of studies. Analysing the existing methods of occupational and educational choice assistance, the method of John L. Holland on “A Psychological Classification of Occupations” has been selected as the most viable and convenient for this purpose. The Holland Codes have been adopted as a lingua franca of this ontology-based model. As a result, the ontology-based decision support system provides assistance in decision making using the Holland Code terminology and practically unlimited complexity of the object and data properties of and ontological presentation of knowledge. ; This work made use of the methods and models developed under the RFBR Grant 18-00-00238 "Methods and models of the intellectual decision support in innovative project management on the basis of knowledge of engineering". ; Startseva, E.; Grimaylo, A.; Chernyahovskaya, L.; Llopis Pascual, F. (2019). Ontology rules application for efficient career choice. En HEAD'19. 5th International Conference on Higher Education Advances. Editorial Universitat Politècnica de València. 1179-1186. https://doi.org/10.4995/HEAD19.2019.9251 ; 1179 ; 1186