|context> => |context: prolog example>

mother |sally> => |trude>
child |trude> = > |sally>

father |sally> => |tom>
child |tom> => |sally>

father |erica> => |tom>
child |tom> +=> |erica>

father |tom> => |mike>
child |mike> => |tom>


parent |*> #=> mother |_self> + father |_self>
sibling |*> #=> child parent |_self>
sibling-clean |*> #=> drop (child parent |_self> + -|_self>)


exit sw
http://en.wikipedia.org/wiki/Prolog

Has this prolog, lets convert it to BKO.



mother_child(trude, sally).
 
father_child(tom, sally).
father_child(tom, erica).
father_child(mike, tom).
 
sibling(X, Y)      :- parent_child(Z, X), parent_child(Z, Y).
 
parent_child(X, Y) :- father_child(X, Y).
parent_child(X, Y) :- mother_child(X, Y).

This results in the following query being evaluated as true:

 ?- sibling(sally, erica).
 Yes