Abstract. This research aims at promoting sharing of knowledge about functionality of artifacts among engineers, which tends to be implicit in practice. In order to provide a conceptual viewpoint for modeling and a controlled vocabulary, we have developed an ontological framework of functional knowledge. This framework has been successfully deployed in a manufacturing company. This paper firstly discusses an ontological definition of the concept of function from a device-centered viewpoint. Then, other types of function are discussed in order to place our definition in the related concepts in the literature. Next, as an application of the ontologies, we propose a metadata schema based on the functional ontologies for functional annotation in the Semantic Web. The functional metadata annotated to technical documents show designers intentions behind the documents and contribute to efficient retrieval of the documents. Moreover, task-oriented transformation and interoperability with other...