CS480/580: Introduction to Artificial Intelligence
Fall 2009
(Lecture: R 1620-1900)
Homework #1
Points: 20
Solution
Question 1 [Points 3] Exercise 3 (Chapter 2 - Cawsey)
(a) Semantic Network
likes
swimming
eats
grass
Hippopotamus
instance
size
lives in
small
herbert
Edinburgh_zoo
(b) Predicate logic:
∀ X hippo(X) →likes(X, swimming)
∀ X hippo(X) →eats(X, grass)
hippo(herbert)
size(herbert,small)
lives(herbert, edinburgh_zoo)
Question 2 [Points 3] Exercise 5 (Chapter 2 - Cawsey)
(a) See below
invest_stocks
R2
savings_adequate AND
R3
NOT has_children
income_adequate
R4
has_partner AND
partner_has_job
(b)
(R5) IF income_huge THEN ADD income_adequate
(R6) IF no_income AND buy_house THEN DELETE savings_adequate
(R7) IF more_kids and partner_low_income THEN DELETE income_adequate
Question 3 [Points 14] Download the movies.pl file and open it in SWI-Prolog using
the consult/1 predicate. This file defines a database of facts of the following
format (NB. Anything following '%' is treated as a comment in Prolog):
% movie(M,Y) <- movie M came out in year Y
movie(american_beauty, 1999).
% director(M,D) <- movie M was directed by director D
director(american_beauty, sam_mendes).
% actor(M,A,R) <- actor A played role R in movie M
actor(american_beauty, kevin_spacey, lester_burnham).
% actress(M,A,R) <- actress A played role R in movie M
actress(american_beauty, annette_bening, carolyn_burnham).
Write queries to answer the following questions (NB. Press ; after
each answer to see if there are any more answers in the database):
1.
% In which year was the movie American Beauty released?
movie(american_beauty, X).
2.
% Find a movie that was released before 2000?
movie(X, Y), Y < 2000, write(X), nl, fail.
3.
% Find an actor who has appeared in more than one movie?
actor(M1,A,_), actor(M2,A,_), \+ M1=M2, write(A),
nl, fail.
4.
% Find an actor or actress who has also directed a
movie? % (Hint: to do this in a single query you will need to
use disjunction (semicolon) as well as conjunction (comma).
(actor(M1,A1,_),director(M2,A1));
(actress(M3,A2,_),
director(M4,A2)).
Write a definition in Prolog for each of the following predicates:
5.
% released_since(M,Y) <- movie M was released after year X
released_since(M,Y) :- movie(M,X), X>Y.
6.
% released_between(M,Y1,Y2) <- movie M was released
between year X and year Y inclusive
released_since(M,Y1,Y2) :- movie(M,X), X>=Y1, X =< Y2.
7.
% cast_member(A,M) <- person A was an actor or actress
in movie M (Give as a two predicates)
cast_member(A,M) :- actor(M, A, _).
cast_member(A,M) :- actress(M,A,_).
8.
% cast_member2(A,M) <- person A was an actor or actress
in movie M(Give as a single predicate using the ; disjunction
predicate)
cast_member2(A,M) :- actor(M, A, _); actress(M,A,_).
9.
% directed_by(X,Y) <- person X has been in a movie
directed by Y % (Hint: re-use your cast_member/2 predicate)
directed_by(X,Y) :- cast_member2(X,M), director(M,Y).
Test your definitions by checking all answers to the appropriate query
relation(X,Y). In some cases you will find unwanted answers of the
form relation(X,X), but don't worry about these for now.
What's the difference between these queries?
10.
11.
12.
13.
?- actor(M1,D,_),actor(M2,D,_).
?- actor(M1,D,_),actor(M2,D,_),M1\=M2.
?- actor(M1,D,_),actor(M2,D,_),M1@<M2.
10---D acted at least in one movie
11---D acted in at least two movies; both (Mi, Mj) as well
as (Mj, Mi) pairs are selected---duplicate pairs selected.
12--- Same as 11 except that it avoids duplicate pairs
being selected.
Why do these queries return answers multiple times?
14.
?- director(_,D),actor(_,D,_).
Because same male may have directed one or more
movies and acted in one or more movies.
15.
?- director(_,D),actress(_,D,_).
Because same female may have directed one or more
movies and acted in one or more movies.