Ontological engineering is an innovative theory and technology to help people build shareable and reusable models/systems in the computer. I have been involved in ontological engineering more than ten years aiming at developing methodologies for uncovering underlying conceptual structures in domains. After a brief introduction to my view of ontological engineering, I concentrate on the functional ontology we have developed and explain the key concepts and a layered ontology for representing functional structure of artefacts. If time allows, I would like to mention our latest achievement on an ontology of learning and instructional theories and its applications to a theory-aware authoring tool.