CSE4/563: Knowledge Representation Recitation November 15, 2010

1. CSE4/563: Knowledge RepresentationRecitation November 15, 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

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

3. SNePSLOG: andor • andor(x,y){P_1, …, P_n} • 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

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

5. 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

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

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

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

9. 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!