What Is a Knowledge Graph — and Why It Matters

Significant progress in healthcare is attributed to structured knowledge, which can be understood as a modern knowledge graph. A knowledge graph is a layered system composed of an ontology that defines classes and relationships, controlled vocabularies that catalog specific instances, and observational data that provides evidence. These layers connect entities like pathogens, diseases, and drugs, enabling reasoning to infer new facts, such as a drug's potential to treat a specific disease. Healthcare leads in this field because it has spent decades refining causal models, meticulously cataloging entities, and conducting standardized, empirical experiments. This foundational work has solved major challenges in areas like search, discovery, and decision support.