An AI system that uses expert rules and facts to make decisions.
An expert system is like a picky school nurse in a computer. If you have spots and a fever, it flips its rule cards.
People used them for medical diagnosis and bank rules. They can explain why, but keeping the rules fresh is hard work.
Symbolic AI
Expert systems are a classic Symbolic AI way to solve problems with rules.
KR
Expert systems use KR to turn expert knowledge into machine-ready rules.
Production
Production often uses if-then rules to drive expert system reasoning.
MYCIN
MYCIN is a classic early medical expert system.