Pattern matching, symbolic matching, expert systems, etc leaded to diagnosing, matching patterns, need experts to match patterns, etc.
List of conclusion from certain premises that is run by some system. If the list is long enough it´ll look like AI. Eg diagnosis by computers. Its a symbolic system approach that may fall into the combinatory explosion.
Combinatory Explosion makes difficult to create robust expert lists. All almost dissapeared in the late 90s. Seems they could have a come back.