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ldata.lisp
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ldata.lisp
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;; -*- Mode: Lisp; -*-
;;;; Database for LTRE
;;;; Last Edited: 4/27/94, by KDF
;;; Copyright 1986 - 1995 Kenneth D. Forbus,
;;; Northwestern University, and Johan de Kleer, Xerox Corporation.
;;; All Rights Reserved.
;;; See the file legal.txt for a paragraph stating scope of permission
;;; and disclaimer of warranty. The above copyright notice and that
;;; paragraph must be included in any separate copy of this file.
(in-package :COMMON-LISP-USER)
(defstruct (dbclass (:PRINT-FUNCTION dbclass-print-procedure))
name ; Corresponding symbol
ltre ; LTRE it is part of.
facts ; Associated facts
rules) ; Associated rules
(defun dbclass-print-procedure (r st ignore)
(declare (ignore ignore))
(format st "<Dbclass ~A>" (dbclass-name r)))
(defstruct (datum (:PRINT-FUNCTION datum-print-procedure))
counter ; Unique ID for easy lookup
ltre ; The LTRE it is part of
lisp-form ; Expression for pattern-matching
(tms-node nil) ; Pointer into TMS
dbclass ; Dbclass of the corresponding pattern
(assumption? nil) ; if non-nil, indicates informant
(plist nil)) ; local property list
(defun datum-print-procedure (d st ignore)
(declare (ignore ignore))
(format st "<Datum ~D>" (datum-counter d)))
;; Previous version used ALPHALESSP, a refuge from MACLISP that
;; compared the printed representations of any two lisp objects (as
;; defined by FORMAT. Given that we only use it for database forms,
;; exploiting the datum counter to provide a cheap ordering constraint
;; between assertions makes more sense.
(defun form< (x y) (< (datum-counter (referent x t))
(datum-counter (referent y t))))
;;;; Adding data
(defvar *connective-list* '(:IMPLIES :AND :OR :IFF :NOT :TAXONOMY))
(defun simple-proposition? (x)
(or (not (listp x))
(not (member (car x) *connective-list*))))
(defun negated-proposition? (form)
(and (listp form) (eq (car form) :NOT)
(simple-proposition? (cadr form))))
(defun assert! (fact just &optional (*LTRE* *LTRE*))
(debugging-ltre "~% Asserting ~A via ~A." fact just)
;; For assertions, simply install the clause.
(add-formula (ltre-ltms *ltre*) (build-tms-formula fact *LTRE*) just))
(defun assume! (fact reason &optional (*LTRE* *LTRE*) &aux datum node)
(setq datum (referent (if (negated-proposition? fact) (cadr fact)
fact) t)
node (datum-tms-node datum))
(debugging-ltre "~% Assuming ~A via ~A." fact reason)
(unless (or (negated-proposition? fact) (simple-proposition? fact))
;; Install clauses corresponding to the assumption, with proper
;; logical scoping
(add-formula (ltre-ltms *ltre*)
`(:IMPLIES ,node ,(build-tms-formula fact *LTRE*)) reason))
(cond ((not (datum-assumption? datum))
(setf (datum-assumption? datum) reason)
(convert-to-assumption node)
(enable-assumption node (if (negated-proposition? fact) :FALSE :TRUE)))
((eq reason (datum-assumption? datum)))
(t (error "Fact ~A assumed because of ~A assumed again because of ~A"
(show-datum datum) (datum-assumption? datum) reason)))
datum)
(defun already-assumed? (fact) (datum-assumption? (referent fact t)))
(defun quiet-assert! (fact *LTRE* &optional (just 'user))
(without-contradiction-check (ltre-ltms *LTRE*)
(assert! fact *LTRE* just)))
(defmacro rassert! (fact &optional (just 'user))
`(assert! ,(quotize fact) ,(quotize just)))
(defun build-tms-formula (formula *LTRE*)
(cond ((and (listp formula)
(member (car formula) *connective-list*))
(cons (car formula)
(mapcar #'(lambda (form)
(build-tms-formula form *LTRE*)) (cdr formula))))
(t (datum-tms-node (referent formula t)))))
;;; Retraction and "bulk assumptions"
(defun retract! (fact just &optional (*LTRE* *LTRE*) (quiet? t)
&aux datum node)
(setq datum (referent fact t)
node (datum-tms-node datum))
(cond ((not (tms-node-assumption? node))
(unless quiet?
(format t "~%~A isn't an assumption." (show-datum datum))))
((not (known-node? node))
(unless quiet?
(format T "~%The assumption ~A is not currently in." fact)))
((eq just (datum-assumption? datum))
(debugging-ltre "~% Retracting ~A via ~A." fact just)
(setf (datum-assumption? datum) nil)
(retract-assumption node))
((not quiet?)
(format t "~%~A not source of assumption for ~A"
just fact)))
node)
(defmacro rretract! (fact &optional (just 'USER))
`(retract! ,(quotize fact) ,(quotize just)))
(defun contradiction (losers *LTRE* &aux datum trues falses)
;; Here we re-cycle this procedure to indicate that a
;; conjunction of facts are contradictory.
(dolist (fact losers
(add-clause trues falses :DECLARED-CONTRADICTION))
(setq datum (referent fact t))
(if (negated-proposition? fact)
(push (datum-tms-node datum) falses)
(push (datum-tms-node datum) trues))))
(defmacro assuming (facts-to-assume *LTRE* &body body)
;; A useful abstraction for user code.
`(with-assumptions
(mapcar #'(lambda (fact &aux node datum)
(setq datum (referent fact t)
node (datum-tms-node datum))
(convert-to-assumption node)
(cons node (if (negated-proposition? fact) :FALSE :TRUE)))
,facts-to-assume)
,@ body))
;;;; Database system
(defun get-dbclass (fact &optional (*LTRE* *LTRE*) &aux dbclass)
(cond ((null fact) (error "~% NIL can't be a dbclass."))
((listp fact)
(cond ((negated-proposition? fact) (get-dbclass (cadr fact) *LTRE*))
(t (get-dbclass (car fact) *LTRE*))))
((variable? fact)
(cond ((boundp fact) (get-dbclass (symbol-value fact) *LTRE*))
(t (error "~%Dbclass unbound: ~A" fact))))
((symbolp fact)
(cond ((gethash fact (ltre-dbclass-table *LTRE*)))
(t (setq dbclass
(make-dbclass :NAME fact :FACTS nil
:RULES nil :LTRE *LTRE*))
(setf (gethash fact (ltre-dbclass-table *LTRE*)) dbclass)
dbclass)))
(t (error "Bad dbclass type: ~A" fact))))
(defun referent (fact &optional (virtual? nil) (*LTRE* *LTRE*))
(if virtual? (insert fact) (referent1 fact)))
(defun referent1 (fact &aux form) ;; Could use seperate hash table
(setq form (if (negated-proposition? fact) (cadr fact) fact))
(dolist (candidate (dbclass-facts (get-dbclass fact *LTRE*)))
(when (equal (datum-lisp-form candidate) form)
(return candidate))))
(defun insert (fact &aux datum form)
(setq datum (referent1 fact))
(cond (datum (values datum t))
(t (setq form (if (negated-proposition? fact) (cadr fact) fact))
(setq datum (make-datum :COUNTER (incf (ltre-datum-counter *LTRE*))
:LTRE *LTRE*
:LISP-FORM form
:DBCLASS (get-dbclass form *LTRE*)))
(setf (datum-tms-node datum) (tms-create-node (ltre-ltms *LTRE*) datum))
(push datum (dbclass-facts (datum-dbclass datum)))
(try-rules datum)
(values datum nil))))
(defun fetch (pattern &optional (*LTRE* *LTRE*) &aux bindings unifiers form)
(setq form (if (negated-proposition? pattern) (cadr pattern) pattern))
(dolist (candidate (get-candidates form *LTRE*) unifiers)
(setq bindings (unify form (datum-lisp-form candidate)))
(unless (eq bindings :FAIL)
(push (sublis bindings pattern) unifiers))))
(defun get-candidates (pattern *LTRE*)
(dbclass-facts (get-dbclass pattern *LTRE*)))
(defun map-dbclass (proc &optional (*LTRE* *LTRE*))
(maphash #'(lambda (name dbclass) (declare (ignore name))
(funcall proc dbclass))
(ltre-dbclass-table *LTRE*)))
;;;; Interface and display of data
(defun true? (fact &optional (*LTRE* *LTRE*) &aux r)
(when (setq r (referent fact nil))
(if (negated-proposition? fact)
(false-node? (datum-tms-node r))
(true-node? (datum-tms-node r)))))
(defun false? (fact &optional (*LTRE* *LTRE*) &aux r)
(when (setq r (referent fact nil))
(if (negated-proposition? fact)
(true-node? (datum-tms-node r))
(false-node? (datum-tms-node r)))))
(defun known? (fact &optional (*LTRE* *LTRE*) &aux r)
(when (setq r (referent fact nil))
(known-node? (datum-tms-node r))))
(defun unknown? (fact &optional (*LTRE* *LTRE*) &aux r)
(if (setq r (referent fact nil))
(unknown-node? (datum-tms-node r))
t))
(defun label-of (fact &optional (*ltre* *ltre*) &aux r)
(when (setq r (referent fact nil))
(tms-node-label (datum-tms-node r))))
(defun why? (fact &optional (*LTRE* *LTRE*) &aux r)
(cond ((setq r (referent fact nil))
(why-node (datum-tms-node r))
(if (and (known-node? (datum-tms-node r))
(datum-assumption? r))
(format t " (~A)" (datum-assumption? r))))
(t (format t "~%~A not in database." fact))))
(defun get-tms-node (fact &optional (*LTRE* *LTRE*))
(datum-tms-node (referent fact t)))
(defun view-node (d) (datum-lisp-form (tms-node-datum d)))
(defun signed-view-node (d) ;; For creating terms in clauses
(if (false-node? d) (list :NOT (view-node d))
(if (true-node? d) (view-node d)
(error "SIGNED-VIEW-NODE requires knowing label: ~A" d))))
(defun show-datum (datum) (format nil "~A" (datum-lisp-form datum)))
(defun make-node-string (node) (show-datum (tms-node-datum node))) ;; For LTMS
(defun assumptions-of (fact &optional (*LTRE* *LTRE*))
(mapcar #'view-node
(assumptions-of-node
(datum-tms-node (referent fact t)))))
(defun consequences (fact)
(unless (known? fact) (return-from consequences nil))
(show-node-consequences (get-tms-node fact)))
(defun explore (fact) (explore-network (get-tms-node fact)))
(defun clear-node-marks (&optional (init #'(lambda () nil)))
(map-dbclass
#'(lambda (dbclass)
(dolist (datum (dbclass-facts dbclass))
(setf (tms-node-mark (datum-tms-node datum))
(funcall init))))))
(defun explain (fact)
(unless (unknown? fact)
(setq *line-count* 0)
(clear-node-marks)
(explain-1 (datum-tms-node (referent fact)))))
;;;; Global interrogatives
(defun show-data (&optional (*LTRE* *LTRE*) (stream *standard-output*)
&aux counter)
(setq counter 0)
(format stream
"~%~D facts total." (ltre-datum-counter *LTRE*))
(maphash
#'(lambda (key dbclass)
(declare (ignore key))
(dolist (datum (dbclass-facts dbclass))
(incf counter)
(format stream "~%~A: ~A" (show-datum datum)
(cond ((true-node? (datum-tms-node datum)) "TRUE")
((false-node? (datum-tms-node datum)) "FALSE")
(t "UNKNOWN")))))
(ltre-dbclass-table *LTRE*))
counter)
(defun get-datum (num &optional (*LTRE* *LTRE*))
(maphash #'(lambda (key dbclass)
(declare (ignore key))
(dolist (datum (dbclass-facts dbclass))
(when (= (datum-counter datum) num)
(return-from GET-DATUM datum))))
(ltre-dbclass-table *LTRE*)))
(defun get-clause (num &optional (*LTRE* *LTRE*))
(dolist (clause (ltms-clauses (ltre-ltms *LTRE*)))
(when (= (clause-index clause) num) (return-from GET-clause clause))))
(defun fetch-global (pattern &optional (status nil) (*ltre* *ltre*)
&aux results)
(map-dbclass
#'(lambda (dbclass)
(dolist (datum (dbclass-facts dbclass))
(if (and (case status
(:TRUE (true-node? (datum-tms-node datum)))
(:FALSE (false-node? (datum-tms-node datum)))
(:KNOWN (known-node? (datum-tms-node datum)))
(:UNKNOWN (not (known-node? (datum-tms-node datum))))
(t t))
(not (eq (unify (datum-lisp-form datum) pattern) :FAIL)))
(push (datum-lisp-form datum) results)))))
results)