Model-driven development is considered to improve productivity and quality in software application development. The increasing complexity in models and the number of modeling methods used requires new approaches for knowledge management to make the handling of models easier both during design and run-time. Modeling in MDD shares characteristics with ontology development. This paper discusses UML based models used in MDD and their relationship to OWL ontologies. A concept is proposed how to create ontologies corresponding to these models and how they can be used concurrently in supporting the application development. The main principle of the approach is the distinct separation of knowledge in the domain model and model instances. As a result the instance model transformations can be kept simple and corresponding ontology representations of application models can be used to support the development. Applications of the approach to model-driven development and engineering of industrial control applications are also discussed.