------------------------------------------------------------------------ Subject: Application of Predicate Logic to AI ------------------------------------------------------------------------ Here's an application of predicate logic to artificial intelligence (AI). In the late 1950s, one of the founders of AI, John McCarthy, proposed a computer program to be called "the advice taker", as part of a project that he called "programs with common sense". (This is a project that he is still actively working on at the age of >= 80, by the way!) (McCarthy is famous for at least the following things: He came up with the name "artificial intelligence", he invented the programming language Lisp, and he invented time sharing. For more information on him, link to our "Logic" webpage at: http://www.cse.buffalo.edu/~rapaport/191/S09/logic.html Then scroll down to: "John McCarthy's research on knowledge representation using FOL:" and click on his name.) The idea behind the advice taker was that problems to be solved would be expressed in a predicate-logic language (only a little bit more expressive than first-order predicate logic), then a set of premises or assumptions describing required background information would be given, and finally the problem would be solved by logically deducing it from the assumptions. He gave an example: getting from his desk at home to the airport. It begins with premises like at(I,desk) meaning "I am at my desk", and rules like AxAyAz[(at(x,y) ^ at(y,z)) -> at(x,z)] which expresses the transitivity of the "at" predicate, and slightly more complicated rules (which go slightly beyond the expressive power of FOL) like: AxAyAz[(walkable(x) ^ at(y,x) ^ at(z,x) ^ at(I,y)) -> can(I, go(y,z,walking))] i.e., if x is walkable, and y and z are at x, and I am at y, then I can go from y to z by walking. The proposition to be proved from these (plus lots of others) is: want(at(I,airport)) To see it all worked out, take a look at his article: McCarthy, John (1959), "Programs with Common Sense", in D.V. Blake & A.M. Uttley (eds.), Proceedings of the ["Teddington"] Symposium on Mechanisation of Thought Processes (London: HM Stationary Office). There's a link to an online version at our Logic webpage: http://www.cse.buffalo.edu/~rapaport/191/S09/logic.html