Abstract. A mobile robot that interacts with its environment needs a machineunderstandable representation of objects and their usages. We present an ontology of objects, with generic shape representations obtained through formfunction reasoning. Sets of objects are associated with typical human activities, which supports context understanding. We describe an efficient ontology document storage system, which is based on stable and well-known relational databases. We first design a relational data schema appropriate for Web Ontology Language (OWL) documents, and then develop a transformation mechanism from OWL documents to the relational schema. 1 Object Recognition and Scene Interpretation To support a robot’s interaction with a typical human environment requires a machine-understandable representation of objects, including their shapes, functions, and usages. Object recognition is supported by reasoning from object shape information, while scene understanding is supported by reasonin...