Question

Suppose that Prolog facts are used to define the predicates mother$\left(M,Y\right)$and father$\left(F,X\right)$which represent that Mis the mother of Yand Fis the father of X, respectively. Give a Prolog rule to define the predicate grandfather $\mathbf{(}\mathit{X}\mathbf{,}\mathit{Y}\mathbf{)}$,which represents that Xis the grandfather of Y. [Hint: You can write a disjunction in Prolog either by using a semicolon to separate predicates or by putting these predicates on separate lines.]

Short answer

grandfather $(X,Y)$: - mother $(M,Y)$, father $\left(X,M\right)$; father $\left(F,Y\right)$, father$\left(X,F\right)$

Step-by-step solution

Given information

Prolog facts are used to define the predicates mother $\left(M,Y\right)$and father$\left(F,X\right)$ which represent that M is a mother of Y and F is the father of X respectively.

Prolog rule to define the predicate sibling(X,Y)

grandfather $(X,Y)$: - mother $\left(M,Y\right)$, father $\left(X,M\right)$; father $\left(F,Y\right)$,father$\left(X,F\right)$$\left(X,F\right)$

Where, :- means define and , represents a conjunction and ; represent a disjunction.