问题
Suppose I have the below code in my familyTree.pl file:
male(tom).
male(bob).
female(lisa).
female(emily).
parent(tom, bob).
parent(lisa, bob).
morethanfriends(emily, bob).
father(X,Y) :- male(X), parent(X,Y).
mother(X,Y) :- female(X), parent(X,Y).
girlfriend(X,Y) :- female(X), (morethanfriends(X,Y); morethanfriends(Y,X)).
boyfriend(X,Y) :- male(X), (morethanfriends(X,Y); morethanfriends(Y,X)).
Now, I want to get the answer to the questions like:
What is the relationship between Tom and Bob ?
What is the relationship between Lisa and Emily ?
How can I ask the above questions to prolog?
The only solution I could come up with was to iterate over the known relation types giving (Tom, Bob) or (Lisa, Emily) as paremeter and check which one returns true. But; this solution seems to be a waste of time, when the number of known relation types are more than a few and/or there is a chain relation between the given two people (i.e.: Lisa and Emily: Lisa is Emily's boyfriend's mother).
回答1:
I have come up with this solution (not checked thoroughly but it seems to be ok):
relations(What, Name1, Name2):-
relation_facts(Facts, Name1, _),
relations1(Facts, [], Name2, What1),
atomic_list_concat(What1, What).
relations1(Facts, Forbidden, Name2, What):-
member(Relation, Facts),
call(Relation),
relations2(Relation, Forbidden, Name2, What).
relations2(Relation, Forbidden, Right, [Left, ' ', is, ' ', Right, '''s ', Name]):-
Relation =.. [Name, Left, Right],
Forbidden \= Right.
relations2(Relation, Forbidden, Name2, [Left, ' ', is, ' '| What]):-
Relation =.. [Name, Left, Right],
relation_facts(Facts, Right, _),
Forbidden\=Right,
relations1(Facts, Left, Name2, [_,_,_,_, NRight|What1]),
append([NRight|What1], ['''s ', Name], What).
% Here goes the relations you want to check for:
relation_facts([father(X,Y), mother(X,Y), girlfriend(X,Y), boyfriend(X,Y)], X, Y).
Test cases:
?- relations(Relation,lisa,emily).
Relation = 'lisa is emily\'s boyfriend\'s mother' ;
?- relations(Relation,lisa,bob).
Relation = 'lisa is bob\'s mother' ;
?- relations(Relation,_,_).
Relation = 'tom is bob\'s father' ;
Relation = 'tom is emily\'s boyfriend\'s father' ;
Relation = 'lisa is bob\'s mother' ;
Relation = 'lisa is emily\'s boyfriend\'s mother' ;
Relation = 'emily is bob\'s girlfriend' ;
Relation = 'bob is emily\'s boyfriend' ;
回答2:
This program, a simplified version of above program, will work for direct relations present in the database.
Query: qus(Y,how,is,a1,related,to,b3).
Facts
/*facts*/
father(a1,a2).
father(a1,a3).
father(a1,b3).
father(a1,b3).
father(a3,a4).
father(a2,b4).
father(a5,b8).
father(a8,b7).
father(a6,a7).
mother(b1,a2).
mother(b1,a3).
mother(b1,b2).
mother(b1,b3).
mother(b2,a5).
mother(b3,b5).
mother(b4,a6).
mother(b6,a7).
mother(b8,b7).
male(a1).
male(a2).
male(a3).
male(a4).
male(a5).
male(a6).
male(a7).
male(a8).
female(b1).
female(b3).
female(b3).
female(b4).
female(b5).
female(b6).
female(b7).
female(b8).
Rules
/*rules*/
parent(X, Y) :-
father(X,Y); mother(X,Y).
child(X, Y) :-
parent(Y, X).
sister(X, Y) :-
female(X),
parent(Z, X), parent(Z,Y),
X \= Y.
brother(X, Y) :-
parent(Z, X), parent(Z, Y),
male(X),
X \= Y.
partner(X, Y) :-
father(X,Z),mother(Y,Z);
father(Y,Z),mother(X,Z).
sibling(X, Y):-
parent(Z, X), parent(Z,Y).
chacha(X, Y) :-
brother(X, Z),
father(Z, Y).
mama(X, Y) :-
brother(X, Z),
mother(Z, Y).
bua(X, Y) :-
sister(X, Z),
father(Z, Y).
mosi(X, Y) :-
sister(X, Z),
mother(Z, Y).
nani(X, Y) :-
mother(X, Z),
mother(Z, Y).
nana(X, Y) :-
father(X, Z),
mother(Z, Y).
dadi(X, Y) :-
mother(X, Z),
father(Z, Y).
dada(X, Y) :-
father(X, Z),
father(Z, Y).
cousin(X, Y) :-
parent(Z, X),
parent(W, Y),
sibling(W, Z),
\+sibling(X, Y),
X \= Y.
secondcousin(X, Y) :-
parent(A, B),
parent(B, X),
parent(C, D),
parent(D, Y),
sibling(C, A),
\+sibling(X, Y),
X \= Y.
Program
qus(Y,how,is,Person1,related,to,Person2):-
database_relations(Relations, Person1, Person2),
find_relation(Relations, Person2, X),
atomic_list_concat(X, Y).
qus(Y,who,is,Person1,of,Person2):-
database_relations(Relations, Person1, Person2),
find_relation(Relations, Person2, X),
atomic_list_concat(X, Y).
find_relation(Relations, Person2, X):-
member(Query, Relations),
call(Query),
write_answer(Query, Person2, X).
write_answer(Relation_in_list, Person2, [Person1, ' ', is, ' ', the, ' ',RelationalAnswer,' ', of, ' ', Person2]):-
Relation_in_list =.. [RelationalAnswer, Person1, Person2].
database_relations([chacha(X,Y),mama(X,Y),bua(X,Y),mosi(X,Y),nani(X,Y),nana(X,Y),dadi(X,Y),dada(X,Y),father(X,Y), mother(X,Y),brother(X,Y),sister(X,Y),parent(X,Y),partner(X,Y),cousin(X,Y),secondcousin(X,Y)], X, Y).
来源：https://stackoverflow.com/questions/4518040/query-the-relation-between-two-people-in-a-prolog-family-tree