CS322, Fall 1997 - Solution to Midterm Exam -- Solution to question 3(a)(i)

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Solution to question 3(a)(i)

Is the arc <X,Y> arc consistent?

Arc <X,Y> is arc consistent means that for every X there exists a Y such that r(X,Y) is true.

The following table shows for each value of X a value of Y such that R(X,Y) is true:

X Y

a d

b a

c ***

d i

Note that there is no element Y in {a,d,i,r} such that r(c,Y) is true. That is there is no word starting with ca, cd, ci, or cr in the word list. c can be removed from the domain of X to make <X,Y> arc consistent.