See http://en.wikipedia.org/wiki/Expert_system
I had some great MentalMasturbation messing around with a commercial ES product (student version) in the early 90's. I couldn't make anything practical out of it, but it's fun tweaking with logic rules and their weights to see what the result is. It did shape some of my views on TableOrientedProgramming, and BusinessRulesMetabase techniques. Good times, except for the "C" I got on the project because I was suppose to extract rules from somebody else's head, not mine. I'm too annoying of a person, nobody wants to talk to me that long ;-P -t
Hong Kong's subway repair scheduling & allocation system: http://www.newscientist.com/article/mg22329764.000-the-ai-boss-that-deploys-hong-kongs-subway-engineers.html#.VAFnsmPBjb0
See also BusinessRulesMetabase