What is Expert System?
An expert system is a computer program that emulates the decision-making ability of a human expert in a narrow domain by applying a collection of if-then rules to known facts.
It is built around two core components: a knowledge base that stores domain facts and production rules, and an inference engine that chains those rules together to reach conclusions or recommendations.
Unlike data-driven machine learning models, expert systems rely on explicitly encoded human knowledge rather than patterns learned from examples, making their reasoning transparent and easy to audit.
They typically include an explanation facility that can trace which rules fired, helping users understand why a particular conclusion was reached.
Example
MYCIN was an early medical expert system that used about 600 rules to diagnose bacterial infections and recommend antibiotics based on patient symptoms and lab results.
Why it matters
Although largely replaced by machine learning for many tasks, the rule-based, explainable approach of expert systems still influences modern decision-support tools, regulatory compliance systems, and efforts to make AI reasoning more interpretable.
Frequently asked questions
Expert systems use hand-crafted rules and facts provided by humans, while machine learning learns patterns automatically from data.
Related terms
Artificial General Intelligence (AGI) is a type of AI that can understand, learn, and apply knowledge across any intellectual task at a human level or beyond, rather than being limited to narrow specialties.
Artificial Intelligence (AI) is the field of computer science focused on creating machines that can perform tasks typically requiring human intelligence, such as learning, reasoning, and decision-making.
Computer Vision is a field of AI that enables computers to interpret and understand visual information from images and videos, similar to how humans see.
Image segmentation is a computer vision technique that partitions an image into multiple regions or segments by assigning a label to every pixel, typically to identify and isolate objects or areas of interest.
Narrow AI, also called Weak AI, is artificial intelligence built to perform one specific task or a narrow range of tasks at a high level.
Object detection is a computer vision task that finds and identifies multiple objects in an image or video. It both classifies what the objects are and locates them using bounding boxes.