; FILE: acme-infer.lisp
; PURPOSE: analogical transfer of propositions
; PROGRAMMER: Paul Thagard, adapting Eric Melz's work on Copying with Substitution and Generation
; CREATED: 5/14/98
; UPDATE: 12/1/98. broad-infer fixed to handle emotional analogies.
; Analogical inference involves transfer of information from
a source to a
; target. This can be broad or specific:
; 1. Broad: What does the source tell you about the target?
; - do full CWSG as in Melz, but make transfer more focused
; on the source and target, not on *all-propositions*.
; 2. More specific: What does the source tell you about particular
; aspects of the target, e.g. predicates and/or objects.
; BROAD-INFER expands the target as fully as possible using all
; source propositions not already mapped to a target proposition.
; SPEC-INFER adds to the target only one proposition.
; The result of both kinds of inference is that a proposition in
; the target is positively linked to the proposition that
; was used to generate it. Analogical inference can be both novel
; and routine. Novel: a new proposition is constructed in the target.
; Routine: an already existing proposition in the target is linked
; to its analog in the source.
; For system mappings, where the propositions are related as part of
; the same causal structure, the links should be much stronger
; than ordinary similarities.
; Forging new activation links should automatically enable transfer
; of valences too, modeling emotional analogies. Inference with
; multiple analogies will also be automatically be modeled, since
; propositions from different source analogs can all be linked to
; a single proposition in the target.
; New variables
(defvar *propn-number* 0)
(defvar *arg-number* 0)
(defvar *min-match-activation* .6) ; matches have to be this good
(defvar *ana-assn* .5) ; analogical association in absence of mapping hypothesis
(defvar *hypotheses-generated* nil) ; new hypotheses generated
; SPEC-INFER makes possible inference of a single proposition
in the target
; supported by its analog in the source. If the proposition to be inferred already
; exists, then all SPEC-INFER does is link it to its analog. Otherwise, it uses
; CWSG to produce a new proposition and link it to its analog.
; Here propn-to-infer is a pair of (propn-from-source propn-from-target)
(defun spec-infer (source target predicate 1-or-more-objects)
(let ((propn-to-infer (find-propn source target predicate 1-or-more-objects)))
(unless propn-to-infer ; if it doesn't exist
(setf propn-to-infer ; make it by cwsg
(make-propn-to-infer source target predicate 1-or-more-objects)
(associate-ana (first propn-to-infer) (second propn-to-infer)) ; link the analogs
(my-print "Making inferential connection: " propn-to-infer)
; ASSOCIATE-ANA associates two analogous propositions, the
first from the source,
; the second from the target. The strength of the association is based on how
; good the mapping is, i.e. on the activation of the unit that represents a
; mapping between the two propositions.
(defun associate-ana (sprop tprop)
(associate sprop tprop (or (get (catname sprop tprop) 'activation) *ana-assn*))
; FIND-PROPN looks in a target structure to see if there is
a proposition involving
; a given predicate and 1 or more objects. If so, it returns a list
; of the the name of the analogous proposition in
; the source, if it exists and the proposition name. Otherwise, it returns nil.
(defun find-propn (source target predicate 1-or-more-objects)
(do ((propns (get target 'propositions) (cdr propns))
((null propns) nil) ; return
(if (propn-matches (list predicate 1-or-more-objects)
(get (car propns) 'message)
(return (list (or (best-match-in-struc source (car propns))
(find-propn-unmapped source (car propns))
; FIND-PROPN-UNMAPPED handles the case where there is no best-match-in-struc
; because the proposition is newly created by another analogy.
; NOTE: this may not be the best match, but it would rarely matter.
(defun find-propn-unmapped (source propn)
(do ((propns (get source 'propositions) (cdr propns)))
((null propns) nil)
(if (propn-matches (get propn 'message)
(get (car propns) 'message)
(return (car propns)) ; found
; PROPN-MATCHES determines if two messages have a similar
; predicate and at least some of the same arguments.
(defun propn-matches (mess1 mess2)
(and (or (equal (car mess1) (car mess2))
(similar? (car mess1) (car mess2))
(intersection (second mess1) (second mess2))
; BEST-MATCH-IN-STRUC is like BEST-MATCH in acme.lisp, except
; should make sure, for the sake of multiple analogies, that the match found
; is from the specified structure. This works with predicates, objects,
; and propositions. Using the constructed-matches property, it
; checks for matches that have been constructed by generation.
(defun best-match-in-struc (struc el)
(let (bm bm2 best-unit other-good-units)
(setq best-unit (highest-l (constraints-for-structure struc el)
(cond ((null best-unit) nil) ; nothing matches
((match-generated struc el) (match-generated struc el))
; else do all of these:
; ADD remove matches from other structures - NOT YET implemented
(if (listp best-unit)
(setq best-unit (car (setq other-good-units best-unit)))
(setq bm (other-from-pair el (get best-unit 'concerns)))
(my-print "Best mapping of " el " in " struc " is " bm ". "
(get best-unit 'activation)
(do ((units (cdr other-good-units) (cdr units)))
((null units) nil)
(setq bm (other-from-pair el (get (car units) 'concerns)))
(my-print " tied with " bm2 ".")
(if (> (get best-unit 'activation) *min-match-activation*)
bm ; return best match if it has high enough activation
; otherwise return nil
) ; end t
) ; end cond
) ; end let
; MATCH-GENERATED looks for a match that has been previously
; by make-propn-to-infer using make-arg
(defun match-generated (struc ele)
(cdr (assoc ele (get struc 'generated-matches)))
; CONSTRAINTS-FOR-STRUCTURE (struc el) returns a list of all
; for an element - object, predicate, or proposition -
; that are relevant to the given structure. This is for multiple
; analogies, where different mappings can co-exist.
(defun constraints-for-structure (struc el)
(do ((constraints (get el 'constraint-hyps) (cdr constraints))
((null constraints) result)
(if (constraint-relevant struc (car constraints))
(push (car constraints) result)
; CONSTRAINT RELEVANT returns T if the given constraint appertains
; a given source structure.
(defun constraint-relevant (struc constraint)
(member (car (get constraint 'concerns))
; ELEMENTS-FROM-STRUCTURE returns a list of all the predicates,
; propositions from a structure.
(defun elements-from-structure (struc)
(do ((propns (get struc 'propositions) (cdr propns))
((null propns) result)
(union-list (list (car propns)
(pred-from-propn (car propns))
(args-from-propn (car propns))
; MAKE-PROPN-TO-INFER uses information in the source to produce
a new proposition
; in the target to infer. The predicate in the new proposition is the
; same as in the source, but the arguments are completed by either
; subsitution (using the best match) or generation of a new argument.
; The predicate must have a corresponding predicate in the source.
; Should there be a similar check for objects?
; Returns a pair of (propn-from-source propn-from-target)
(defun make-propn-to-infer (source target pred object-lst)
(let ((new-message nil)
(new-propn (gen-target-propn target pred))
(source-propn (find-source-propn source pred))
(if (null source-propn) ; no source proposition found
(progn (my-print "No source analog found for " pred " and " object-lst)
nil ; return nothing
; else construct the message
(do ((arguments (reverse (new-args-from-propn source-propn)) (cdr arguments))
((null arguments) ; exit: construct new message
(setf new-message (list pred new-arguments new-propn))
(setf (get new-propn 'message) new-message)
(push new-message (get target 'all)) ; ADD more specific field
(push new-propn (get target 'propositions))
; store match with source:
(setf (get source 'generated-matches)
(acons source-propn new-propn (get source 'generated-matches))
(process-cause new-propn) ; provide input to ECHO if causal
(list source-propn new-propn) ; return pair
; repeat construction of arguments
(setq new-arguments (push (make-arg source (car arguments)) new-arguments))
; NEW-ARGS-FROM-PROPN is slightly different from the original
in ACME which
; has an additional screening function.
(defun new-args-from-propn (propn)
(second (get propn 'message))
; FIND-SOURCE-PROPN makes sure that there is a source proposition
; provide information about the target predicate. The source proposition has
; to have the same predicate as the predicate to be inferred about.
; This takes the first occurrence - ideally it should make more than
; one possible inference.
(defun find-source-propn (source pred)
(do ((propns (get source 'propositions) (cdr propns)))
((null propns) nil); exit - nothing found
(if (equal pred (car (get (car propns) 'message)))
(return (car propns))
; MAKE-ARG takes the analogous object if there is one, and
; a new one ARG-NEW-# if there isn't.
; If the argument is a list, as in (CAUSE (CAUSE1 CAUSE2 ...) EFFECT),
; need to iterate.
(defun make-arg (source arg)
(let ((new-arg nil))
(if (listp arg) ; argument is a list
(make-all-args source arg)
; else argument is is an object
(or (best-match-in-struc source arg)
(match-generated source arg)
(progn (incf *arg-number*)
(setf new-arg (concat-2 (concat-2 arg '-new-) *arg-number*))
(setf (get source 'generated-matches)
(acons arg new-arg (get source 'generated-matches))
; MAKE-ALL-ARGS makes an argument consisting of a list of objects.
(defun make-all-args (source arg)
(do ((args (reverse arg) (cdr args))
((null args) result)
(setq result (push (make-arg source (car args)) result))
; GEN-TARGET-PROPN generates a new proposition to be part of a target
(defun gen-target-propn (target pred)
(let ((new nil))
(setf new (concat-2 (concat-2 pred '-new- ) *propn-number*))
(push new (get target 'propositions))
(proposition new "Hypothesis")
(my-print "New proposition " new " made for " target)
(push new *hypotheses-generated*)
new ; return name of proposition
; CONCAT-2 makes a new atom out of two given atoms; cf. CATNAME
; CONCAT in acme.lisp combines any number of atoms.
(defun concat-2 (atm1 atm2)
(read-from-string (coerce (append (coerce (princ-to-string atm1) 'list)
(coerce (princ-to-string atm2) 'list)
; PROCESS-CAUSE takes a newly generated proposition and produces
; to ECHO if appropriate. To be added: other predicates for ECHO and DECO.
(defun process-cause (propn)
(cond ((equal (pred-from-propn propn) 'cause)
(explain (first (new-args-from-propn propn))
(second (new-args-from-propn propn))
; MY-SORT alphabetizes
(defun my-sort (lst) (sort lst #'string-lessp))
; BROAD-INFER does full pattern completion on a source, generating
; new propositions for every source proposition that lacks an analogous
; target proposition. This function is analogous to Melz's TRANSFER.
; But it also creates links to make inferences. For each
; proposition of the source, it either finds the most analogous
; proposition of the target, or else creates a new one.
; BUGS 12-1-98: slight redundancy in making of propositions and associations.
; 3-19-99: need to reverse proposition list to ensure causes get
; processed last.
(defun broad-infer (source target)
(do ((propns (reverse (get source 'propositions)) (cdr propns))
(ana-prop nil) ; analogous proposition
(my-print source " applied to " target " yields: " )
(my-print "Making inferential connections: " pairs-to-connect)
(associate-pairs pairs-to-connect) ; link the analogs
(setf message (get (car propns) 'message))
(my-print "Transferring " message)
(setf ana-prop (best-match-in-struc source (car propns)))
(if ana-prop ; a good match already exists
(push (list ana-prop (car propns)) pairs-to-connect)
; else make a new proposition to infer
(push (make-propn-to-infer source target (car message) (second message))
; ASSOCIATE-PAIRS takes a list of pairs and establishes a positive
; between each pair.
(defun associate-pairs (lst)
(do ((pairs lst (cdr pairs)))
((null pairs) (my-print "Inferences made."))
(associate-ana (caar pairs) (second (car pairs)))
; ACTIVATE-PROPOSITIONS initializes all propositions for further inference.
(defun activate-propositions ()
(mapcar #'activate-prop *all-propositions*)
(defun activate-prop (prop)
(put prop 'activation *init-activ*)
(put prop 'valence *init-activ*)