Abstract. Sharing data from various systems such as sensor networks, time and motion study data, and text data is important. To process and manage the collected data, the authors have proposed a database framework called the COTO database. As described in this paper, the authors propose a COTO-ontology as the basis of the COTO database. The COTO-ontology was developed based on the data collected by DANCE, which is an evaluation tool of quality of care, from the real settings. It will be applied as a platform for the evaluation of robotic devices used for nursing care.