An expert system is software that uses a knowledge base of human expertise to solve problems or clarify uncertainties that would normally require human experts. It works by creating a knowledge base through gathering knowledge from subject matter experts, and representing it in a structured format. Once developed, the expert system can be used in real world problem solving similar to a human expert. Examples of expert systems include CaDet, a clinical decision support system for early cancer detection, and other medical expert systems that help with cancer risk evaluation and early detection.