To perform surgery, sufficient knowledge and experience based on clinical information are required. Also, AI-aided surgery that is expected to become widely practiced in the near future requires vast amounts of high-quality training data to continually improve accuracy. A database that stores clinical data using a real-world model is needed to meet these requirements. This chapter explains the semantic data model (SDM), an extension of semantic data modeling, which is a method for translating real-world data into a relational database. The SDM extracts clinical data from different database models in hospital information systems, transforms them into the SDM’s logical schema, and loads them into the SDM database. The features of the SDM, especially its logical schema, are described. The SDM will be a component of the information infrastructure for AI-aided surgery.