Abstract. The article discusses the development of an ontology designed to formalize and support the process of teacher professional development in the context of digital transformation of education with an emphasis on STEM-based approaches. The relevance of the research is determined by the need for a systematic presentation of the professional competencies of teachers of the 21st century and ensuring their measurability in digital educational environments. The aim of the work is to create an ontological model that ensures the integration of STEM methods, competencies, indicators of their formation, assessment tools and forms of control in a single information structure. The study used methods of ontological modeling, formal description of knowledge using OWL, as well as SPARQL queries for data analysis and extraction. As a result, an ontology has been developed that implements the “STEM-method – competence – indicators – tools – forms of control” compliance matrix and supports automated monitoring of teachers’ professional development. The scientific novelty of the work lies in the comprehensive formalization of the professional development process based on an ontological approach. The practical significance is determined by the possibility of using ontology in digital professional development platforms, decision support systems and quality analysis of teacher education.

Keywords: STEM education, teacher training, professional competencies, digital transformation of education, STEM methods, methodological model, competence assessment.