I. Introduction
A knowledge graph (KG), which describes knowledge in the form of“Subject-Predicate-Object” triple [1], is one of the most popular approaches for representing knowledge on the current Web [2]. In the health sciences, biomedical knowledge graphs (BMKGs) link biomedical entities (such as diseases, proteins, and drugs) through certain defined relationships. They are important tools to computationally analyze the comprehensive body of biomedical knowledge. BMKGs have been widely applied in multiple tasks, such as extracting disease biomarkers [3], identifying disease mechanisms [4], and predicting health benefits (i.e., efficacy) of a drug over a placebo [5], which could further facilitate precision medicine and clinical decision support.