Question

Extend the program by adding rules for the following family relationships (add more facts as you need ).

Rules

father(X.Y) >

Father (z,w)

where X is Y's father

father(X,Y):>male(X),Parent(X, Y).

brother(X, Y):

where X is Y's brother brother(X,Y):-male().praent(X,Y).

Brother (y.w)

sister(X,Y):-famale(X),praent(X, Y).

sister(X,

Y):

where X is Y's sister

Sister(w.y)

son(X, Y)>

son(X,Y):-male(X), praent(Y,X).

where X is Y's son

Son(y.z)

daughter(X, Y) :- Daughter (w,x)

where X is Y's daughter daughter(X,Y):-famale(X), praent(Y.X).

where X and Y are sibling Sibling(X, Y):-praent(X,Y), praent(X, Y).

Sibling(X.Y): Sibling(w.y)

hint) Solved example:

female(mary).

Facts

male(joe).

parent(mary, joe).

mother(MX)- female(M). parenx(M, X)

Rule

Question →

?-mother (mary. joe).

Answer

True.

(hint) draw a family tree if you need.

Answer 1

Most of the input from the terminal to the prompt "?-" are queries.

Question →

?-mother (mary. joe).

This query may be read "Is mary mother of Joe?" Queries end with a period.

Rules

?- [user].

child(X,Y) :- parent(Y,X).

% X is a child of Y if Y is a parent of X. %

mother(X,Y) :- parent(X,Y), female(X).

% X is a mother of Y if X is a female parent of Y
father(X,Y) :- parent(X,Y), male(X).

% X is a father of Y if X is a male parent of Y

son(X,Y) :- child(X,Y), male(X).

% X is a son of Y is X is a male child of Y

son(X,Y) :- child(X,Y), male(Y).

% X is a son of Y if X is a male child of Y.

So it is true that Mary is the mother of Joe

• Multiple rules

given Sibling(X.Y): Sibling(w.y)

?- [user].

sibling(X,Y) :- parent(Z,X), parent(Z,Y).

   // A sibling is someone with the same parent

close-relation(X,Y) :- child(X,Y).

close-relation(X,Y) :- sibling(X,Y).

close-relation(X,Y) :- parent(X,Y).

// A close relation is either a child, or a sibling, or a parent.

When more than one rule is given for a goal, Prolog tries the various rules in the given order.

?- close-relation(anne,charles).

TRUE, so the second rule succeeds

· To extend program

?- close-relation(X,charles).

X = william ;

X = harry ;

X = charles ;

X = charles ;

X = anne ;

X = anne ;

X = andrew ;

X = Mary ;

X = Joe ;

FALSE

Prolog first goes through the answers given by the "child" rule, then the answers given by the "sibling" rule, then the answers given by the "parent" rule.The goal "sibling(charles,X)'' succeeds twice for each sibling of Charles as well as for himself, once for their common parent Mary and once for their common parent Joe.

• Recursion      

?- [user].

ancestor(X,X).

ancestor(X,Y) :- parent(X,Z), ancestor(Z,Y).

The ancestor relationship is defined recursively in two rules:

Base case: Every man is his own ancestor.

Recursive case:If X is a parent of an ancestor of Y, then X is an ancestor of Y.

A literal with variables and no body, such as "ancestor(X,X)"is a statement that the form is true for all values of the variable ie, for any X "ancestor(X,X)" is true.

?- ancestor(charles,charles).

yes

The query matches the base rule "ancestor(X,X)".