Re: Datalog With Only Binary Relations Is Too Weak

> [Drew]
> If we want all backward chaining we express the skolemized form as
>
> (<-- (grandparent ?a ?c)
>      (and (parent ?a ?b) (parent ?b ?c)))
>
> (<-- (parent ?a (f ?a ?c))
>      (grandparent ?a ?c))
>
> (<-- (parent (f ?a ?c) ?c)
>      (grandparent ?a ?c))

fully agreed with that
is there a difference between <-- and <= ?

> Any backward-chaining algorithm will solve this one.

I would expect so

--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/