retrieval.clj

(def foo {:bar 1 :moo {:event {:_value 2} :ter {:_value 1} :ber {}}
          :floors [{:area {:_value 10} :height {}} {:area {} :height {:_value 5}}]
          :roofs [{:area {}}]})

(defn parse [cursor]
  (clojure.walk/postwalk (fn [m]
                           (if-let [v (:_value m)]
                             v
                             (cond
                              (and (map? m) (empty? m)) nil
                              (map? m)                  (into {} (remove (comp nil? second) m))
                              :else                     m)))
                         cursor))

;; (parse foo) returns:
;;
;; {:bar 1, :moo {:event 2, :ter 1}, :floors [{:area 10} {:height 5}]}