Logic-based Yin-Yang ontology and top-level design for integrating traditional Chinese and Western medicine

<bold>Objective</bold> The theory of Yin-Yang and the Five Elements is a core theory of ancient Chinese philosophy and forms the foundation of traditional Chinese medicine（TCM）.Ontology，which originates from Western philosophy（particularly metaphysics），is considered “first philosophy，” and logic-based ontology is often regarded as the source and foundation of science.Proceeding from philosophical ontology，ontology in the informatics era is defined as a set of structured and controlled terms that represent the entities and relations among the entities in reality as a human- and computer-understandable way，which greatly supports contemporary knowledge representation in artificial intelligence.The purpose of this study is to use logic-based ontology to formalize the Yin-Yang and Five Elements theory and to support the top-level integration of Chinese and Western medicine（including veterinary medicine），which would guide more specific theoretic research and applications in the future. <bold>Method</bold> The Basic Formal Ontology（BFO）is used as the primary upper-level ontology to design the “Yin-Yang Ontology”（YYO），which expresses key terms in the Yin-Yang and Five Elements theory，as well as further expresses fundamental theories of TCM.Concrete case were developed to demonstrate how ontology-based integration of Chinese and Western medicine operates. <bold>Result</bold> Entities related to Yin-Yang can be categorized into different types of ontological entities，including material entities，processes，and Yin and Yang properties possessed by material or process entities.The five main parts in TCM（namely，Heart，Liver，Spleen，Lung，and Kidney）are regarded as five types of material entities，each having five Yin-Yang properties（namely，great Yang-Fire characteristic-Firing，young Yang-Wood characteristic-Growing，chaos-Earth-Fusing，young Yin-Gold characteristic-Infusing，and great Yin-Water characteristic-Infiltrating，respectively）.These different types of entities and their subclasses are explicitly and logically defined in the YYO.Additionally，the YYO defines relationships in the Yin-Yang and Five Elements theory such as “<italic>engenders</italic>”（Sheng）and “<italic>counteracts</italic>”（Ke）.Through these definitions，YYO is used to explain the fundamental TCM content as well as to illustrate certain predictions and applications that extend from traditional Chinese medicine.Taking the Kidney in TCM as an example，YYO is used to provide ontological-level arguments and further extensions for TCM-derived methods such as treating chronic kidney disease by strengthening the Spleen and Stomach to benefit the Kidney. <bold>Conclusion</bold> Logic-based ontology is used to standardize and formalize the Yin-Yang and Five Elements theory and traditional Chinese medicine（including veterinary medicine），thereby achieving a top-level design for the integration of Chinese and Western medicine.The Yin-Yang Ontology（YYO）ontologizes the Yin-Yang and Five Elements theory and traditional TCM theories，an example of the prevention and treatment of the kidney and kidney diseases in traditional Chinese medicine is given to illustrate the feasibility and application of YYO in the top-level integration of traditional Chinese and Western medicine.