test.dl

parent("Lasse", "Carsten").
parent("Lasse","Grethe").
parent("Peter", "Carsten").
parent("Heidi", "Carsten").
parent("Peter", "Grethe").
parent("Heidi", "Grethe").
male("Carsten").
male("Lasse").
male("Peter").
male("Verner").
female("Heidi").
female("Grethe").
brother("Grethe","Verner").

father(Child,Dad) :- parent(Child,Dad),
                     male(Dad).
mother(Child,Mom) :- parent(Child,Mom),
                     female(Mom).

brother(X,Y) :- parent(X,Z),
                parent(Y,Z),
                parent(X,H),
                parent(Y,H),
                male(Y), 
                X!=Y.

sister(X,Y) :- parent(X,Z),
               parent(Y,Z),
               parent(X,H),
               parent(Y,H),
               female(Y),
               X!=Y.

uncle(X,Y) :- male(Y),
              brother(Z,Y),
              parent(X,Z).

aunt(X,Y) :-  female(Y),
              sister(Z,Y),
              parent(X,Z).


coloredge("A","B","Blue").
coloredge("B","C","Red").
coloredge("C","D","Blue").

bluePath(X,Y) :- coloredge(X,Y,"Blue").
redPath(X,Y) :- coloredge(X,Y,"Red").

colorPath(X,Y) :- bluePath(X,Y).
colorPath(X,Y) :- redPath(X,Y).

colorPath(X,Z) :- bluePath(X,Y),
                  redPath(Y,Z).

colorPath(X,Z) :- redPath(X,Y),
                  bluePath(Y,Z).


evenEdge("A","B").
evenEdge("B","C").
evenEdge("C","D").
evenEdge("D","E").


evenPath(X,Z) :- oddPath(X,Y),
                 oddPath(Y,Z).

evenPath(X,Z) :- evenPath(X,Y),
                 evenPath(Y,Z).

oddPath(X,Z) :- evenEdge(X,Z).

oddPath(X,Z) :- evenPath(X,Y),evenEdge(Y,Z).