Transitive properties in a toy triple store using Clojure's core.logic.

logic-triples.clj

(defrel triple ^{:index true} s ^{:index true} p ^{:index true} o)

(facts triple [[:Berlin  :is-a    :city]
               [:city    :is-a    :permanent-settlement]
               [:Berlin  :part-of :Germany]
               [:Germany :part-of :EU]
               [:EU      :part-of :Eurasia]
               [:Eurasia :part-of :Earth]])

(run* [q] (triple q :is-a :city))
;; => (:Berlin)

(defne transitivo [x p y]
  ([x p y] (triple y p x))
  ([x p y] (fresh [z]
                  (triple z p x)
                  (transitivo z p y))))

(run* [q] (transitivo q :is-a :Berlin))
;; => (:city :permanent-settlement)

(run* [q] (transitivo q :part-of :Berlin))
;; => (:Germany :Eurasia :EU :Earth)