Frame Language in Clojure - three basic functions

Frame-language-1.clj

;; this gist contain the CLojure code for the blog post:
;; http://highorderdysfunctions.blogspot.it/2014/02/frame-language-in-clojure-part-1.html
(ns employees.core)

(def Henry {:is-a {:value 'system-analyst} 
            :working-at {:value 'unit-i} 
            :recruitment-date {:value "14/03/2010"} 
            :gross-salary {:value 3000,00}})

(defn fget [frame slot facet]
  (get-in frame [slot facet]))

(defn fput [frame slot facet v]
  (assoc-in frame [slot facet] v))

(defn fremove [frame slot facet]
  (dissoc-in frame [slot facet]))

; dissoc-in was once part of clojure.contrib.core, and is now part of core.incubator

(defn dissoc-in
  "Dissociates an entry from a nested associative structure returning a new
  nested structure. keys is a sequence of keys. Any empty maps that result
  will not be present in the new structure."
  [m [k & ks :as keys]]
  (if ks
    (if-let [nextmap (get m k)]
      (let [newmap (dissoc-in nextmap ks)]
        (if (seq newmap)
          (assoc m k newmap)
          (dissoc m k)))
      m)
    (dissoc m k)))