$6\mathrm{.}7$ Consider the following logic puzzle: In five houses, each with a different color, live five

persons of different nationalities, each of whom prefers a different brand of candy, a different

drink, and a different pet. Given the following facts, the questions to answer are "Where does

the zebra live, and in which house do they drink water?"

$5$ Ginsberg et al$.(1990)$ discuss several methods for constructing crossword puzzles. Littman et al$.(1999)$ tackle

the harder problem of solving them.

The Englishman lives in the red house.

The Spaniard owns the dog.

The Norwegian lives in the first house on the left.

The green house is immediately to the right of the ivory house.

The man who eats Hershey bars lives in the house next to the man with the fox.

Kit Kats are eaten in the yellow house.

The Norwegian lives next to the blue house.

The Smarties eater owns snails.

The Snickers eater drinks orange juice.

The Ukrainian drinks tea.

The Japanese eats Milky Ways.

Kit Kats are eaten in a house next to the house where the horse is kept.

Coffee is drunk in the green house.

Milk is drunk in the middle house.

Discuss different representations of this problem as a CSP$.$ Why would one prefer one repre$-$

sentation over another?