The paper presents a project management competencies model, using an ontological approach. The ontology, named PMCatalog, was developed in the framework of the project CONTO, financed by Romanian through the grant 91-037/2007. PMCatalog is consistent with the competence definition and PM competence elements included in the International Competence Baseline, the competency standard of the International Project Management Association. The main PMCatalog's use cases for commercial activities in sustainable development projects are described. Ontology was developed using the Protege editor.