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;; Copyright (c) Jeffrey Straszheim. All rights reserved. The use and
;; distribution terms for this software are covered by the Eclipse Public
;; License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) which can
;; be found in the file epl-v10.html at the root of this distribution. By
;; using this software in any fashion, you are agreeing to be bound by the
;; terms of this license. You must not remove this notice, or any other,
;; from this software.
;;
;; seminaive.clj
;;
;; A Clojure implementation of Datalog -- Semi Naive Evaluation
;;
;; straszheimjeffrey (gmail)
;; Created 5 March 2009
(ns clojure.contrib.datalog.seminaive
(:use clojure.contrib.datalog.util
clojure.contrib.datalog.database
clojure.contrib.datalog.literals
clojure.contrib.datalog.rules
clojure.contrib.datalog.magic)
(:use [clojure.set :only (union intersection difference)])
(:use [clojure.contrib.seq-utils :only (indexed)])
(:require [clojure.contrib.graph :as graph]))
;;;; WORK IN PROGRESS !!!
;;; Delta Rules
(defn- compute-delta-rules*
"Perform the delta computation of a rule, where i-rules is the set
of intensional predicates."
[r i-preds]
(let [head (:head r)
head-negated (negated-literal head)
delta-head (delta-literal head)
body (:body r)
build-body (fn [left lit right]
(assoc r :head delta-head
:body (concat left
[(delta-literal lit)]
right
[head-negated])))
new-rules (loop [lit (first body)
left []
right (next body)
results []]
(if (nil? lit)
results
(let [new-results (if (-> lit literal-predicate i-preds)
(conj results (build-body left lit right))
results)]
(recur (first right)
(conj left lit)
(next right)
new-results))))]
(if (empty? new-rules)
[(assoc r :head delta-head :body (conj (vec body) head-negated))]
new-rules)))
(defn- compute-delta-rules
"Compute the delta rules of a rules set, where i-rules is the set of
intensional predicates."
[rs i-preds]
(-> (mapcat #(compute-delta-rules* % i-preds) rs) set make-rules-set))
(defn- compute-basic-delta-rule
"Given a rule, return its basic delta rule form"
[r]
(let [head (:head r)
delta-head (delta-literal head)
cols (literal-columns head)
new-bindings (into {} (for [col cols]
[col (gensym "?var_")]))]
(assoc r :head (assoc head :term-bindings new-bindings)
:body [(assoc delta-head :term-bindings new-bindings)])))
(defn- compute-basic-delta-rules
"Given a rules set, return the basic delta rules set"
[rs]
(-> (map compute-basic-delta-rule rs) set make-rules-set))
;;; Work Plan
(defstruct semi-naive-work-plan
:delta-rules
:basic-rules
:query)
(defn make-semi-naive-work-plan
[rs q]
(let [adorned-q (adorn-query q)
adorned (adorn-rules-set rs adorned-q)
magic (conj (magic-transform adorned)
(seed-rule adorned-q))
i-preds (all-predicates magic)
delta (compute-delta-rules magic i-preds)
basic (compute-basic-delta-rules magic)]
(struct-map semi-naive-work-plan
:delta-rules delta
:basic-rules basic
:query adorned-q)))
;;; Eval
(defn- semi-naive-operator
[deltas basics [delta-db db]]
(trace-datalog (println)
(println)
(println "=============== Begin iteration ==============="))
(let [new-deltas (apply-rules-set (database-merge [db delta-db]) deltas)
new-db (apply-rules-set (database-merge [db new-deltas]) basics)]
[new-deltas new-db]))
(defn run-semi-naive-work-plan
([wp db] (run-semi-naive-work-plan wp db {}))
([wp db binds]
(let [query (:query wp)
deltas (:delta-rules wp)
basics (:basic-rules wp)
seed (seed-predicate-for-insertion query)
seeded-db (project-literal db seed [binds] is-query-var?)
state [empty-database seeded-db]
fun (partial semi-naive-operator deltas basics)
equal (fn [[delta-1 db-1] [delta-2 db-2]]
(and (= (database-counts db-1) (database-counts db-2))
(= (database-counts delta-1) (database-counts delta-2))))
[_ new-db] (graph/fixed-point state fun nil equal)
pt (build-partial-tuple query binds)]
(select new-db (literal-predicate query) pt))))
(comment
(def db-base
(make-database
(relation :employee [:id :name :position])
(index :employee :name)
(relation :boss [:employee-id :boss-id])
(index :boss :employee-id)
(relation :can-do-job [:position :job])
(index :can-do-job :position)
(relation :job-replacement [:job :can-be-done-by])
;(index :job-replacement :can-be-done-by)
(relation :job-exceptions [:id :job])))
(def db
(add-tuples db-base
[:employee :id 1 :name "Bob" :position :boss]
[:employee :id 2 :name "Mary" :position :chief-accountant]
[:employee :id 3 :name "John" :position :accountant]
[:employee :id 4 :name "Sameer" :position :chief-programmer]
[:employee :id 5 :name "Lilian" :position :programmer]
[:employee :id 6 :name "Li" :position :technician]
[:employee :id 7 :name "Fred" :position :sales]
[:employee :id 8 :name "Brenda" :position :sales]
[:employee :id 9 :name "Miki" :position :project-management]
[:employee :id 10 :name "Albert" :position :technician]
[:boss :employee-id 2 :boss-id 1]
[:boss :employee-id 3 :boss-id 2]
[:boss :employee-id 4 :boss-id 1]
[:boss :employee-id 5 :boss-id 4]
[:boss :employee-id 6 :boss-id 4]
[:boss :employee-id 7 :boss-id 1]
[:boss :employee-id 8 :boss-id 7]
[:boss :employee-id 9 :boss-id 1]
[:boss :employee-id 10 :boss-id 6]
[:can-do-job :position :boss :job :management]
[:can-do-job :position :accountant :job :accounting]
[:can-do-job :position :chief-accountant :job :accounting]
[:can-do-job :position :programmer :job :programming]
[:can-do-job :position :chief-programmer :job :programming]
[:can-do-job :position :technician :job :server-support]
[:can-do-job :position :sales :job :sales]
[:can-do-job :position :project-management :job :project-management]
[:job-replacement :job :pc-support :can-be-done-by :server-support]
[:job-replacement :job :pc-support :can-be-done-by :programming]
[:job-replacement :job :payroll :can-be-done-by :accounting]
[:job-exceptions :id 4 :job :pc-support]))
(def rules
(rules-set
(<- (:works-for :employee ?x :boss ?y) (:boss :employee-id ?e-id :boss-id ?b-id)
(:employee :id ?e-id :name ?x)
(:employee :id ?b-id :name ?y))
(<- (:works-for :employee ?x :boss ?y) (:works-for :employee ?x :boss ?z)
(:works-for :employee ?z :boss ?y))
(<- (:employee-job* :employee ?x :job ?y) (:employee :name ?x :position ?pos)
(:can-do-job :position ?pos :job ?y))
(<- (:employee-job* :employee ?x :job ?y) (:job-replacement :job ?y :can-be-done-by ?z)
(:employee-job* :employee ?x :job ?z))
(<- (:employee-job* :employee ?x :job ?y) (:can-do-job :job ?y)
(:employee :name ?x :position ?z)
(if = ?z :boss))
(<- (:employee-job :employee ?x :job ?y) (:employee-job* :employee ?x :job ?y)
(:employee :id ?id :name ?x)
(not! :job-exceptions :id ?id :job ?y))))
(def wp-1 (make-semi-naive-work-plan rules (?- :works-for :employee '??name :boss ?x)))
(binding [*trace-datalog* true]
(run-semi-naive-work-plan wp-1 db {'??name "Albert"}))
(time (dotimes [_ 100]
(run-semi-naive-work-plan wp-1 db {'??name "Albert"})))
(def wp-2 (build-work-plan rules (?- :employee-job :employee '??name :job ?x)))
(binding [*trace-datalog* true]
(run-work-plan wp-2 db {'??name "Li"}))
(def wp-3 (build-work-plan rules (
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