simple prolog vs BKO example

Just a comparison between some prolog on wikipedia, and the BKO equivalent.

First the prolog:

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

Now in BKO:

|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>          -- this being the BKO equivalent of: sibling(X, Y) :- parent_child(Z, X), parent_child(Z, Y) 
sibling-of |*> #=> clean drop (child parent |_self> + -|_self>)

now put it to use:

sa: sibling |sally>
|sally> + |erica>

sa: sibling |erica>
|sally> + |erica>

sa: sibling-of |sally>
|erica>

sa: sibling-of |erica>
|sally>

Finally, we can ask the question: "is X a sibling of Sally?"

sa: is-a-sibling-of-sally |*> #=> do-you-know mbr(|_self>, sibling-of|sally>)

sa: is-a-sibling-of-sally |erica>
|yes>

sa: is-a-sibling-of-sally |george>
|no>

And I guess that is enough.

Update: perhaps we should tweak our operator names to a little closer to English and NLP?

mother-of |sally> => |trude>
child-of |trude> = > |sally>

father-of |sally> => |tom>
child-of |tom> => |sally>

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

father-of |tom> => |mike>
child-of |mike> => |tom>

parents-of |*> #=> mother-of |_self> + father-of |_self>
siblings-of |*> #=> clean drop (child-of parents-of |_self> + -|_self>)