CSE4/563: Knowledge Representation Recitation November 17, 2010 “There is a popular cliche…which says that you cannot get out of computers any more than you have put in…, that computers can only do exactly what you tell them to, and that therefore computers are never creative. This cliché is true only in a crashingly trivial sense, the same sense in which Shakespeare never wrote anything except what his first schoolteacher taught him to write—words. ” –Richard Dawkins, "The Blind Watchmaker"  quoted by Stan Franklin  "Artificial Minds," 1997

HW8 Questions/Concerns? http://www.cse.buffalo.edu/~shapiro/Courses/CSE563/2010/Homeworks/hw8.pdf

SNePSLOG: andor andor(x,y){P_1, …, P_n} See Chapter 8 slide 438 At least x and at most y Can be equivalent to and (x=n, y=n) or (x=1, y=n) nand (x=0, y=n-1) nor (x=0, y=0) xor (x=1, y=1) See Chapter 8 slide 438

SNePSLOG: thresh thresh(x,y){P_1, …, P_n} See Chapter 8 slide 440 Less than x or more than y iff{} is one abbreviation of it (x=1, y =n-1) See Chapter 8 slide 440

SNePSLOG: nexists nexists(i,j,k)(x1,…,xn)(P: Q) k sequences of ground terms satisfying every p in P Of those, at least i and at most j also satisfy every q in Q. See Chapter 8 slides 444-445

nexists Example Example: nexists(2,2,4)(y)[{person(y), inFirstFamily(y)} :{isParent(y)}].

nexists Example Example: nexists(y)(2,2,4)[{person(y), inFirstFamily(y)} :{isParent(y)}]. There are 4 terms matching y in P

nexists Example Example: nexists(2,2,4)(y)[{person(y), inFirstFamily(y)} :{isParent(y)}]. Of those, 2 and only 2 match y in Q

nexists Example Example: nexists(2,2,4)(y)[{person(y), inFirstFamily(y)} :{isParent(y)}]. So, of the 4 people in the first family (Barack, Michelle, Malia, and Sasha), 2 and only 2 of them are parents (Barack and Michelle). It would be a contradiction if more of them were!