Re: Unexpected Powerloom truth maintenance behavior....

Hi Hans





Can do...Will assert types explicitly.





I am experiening the following issue:


With following definitions:


(defconcept person (?x))

(defrelation alive (?x))



(defconcept live-person (?x person)

  :<=> (alive ?x)

  )

(defrelation spouse ((?x person) (?y person))

  :axioms (symmetric spouse))





;; (defrelation married ((?x person) (?y person))

;;    :<=> (and (spouse ?x ?y) (live-person ?x) (live-person ?y) ))



(assert (spouse jack jill))

(assert (and (alive jack) (alive jill)))





I get the following correct response;


STELLA> (retrieve all (married ?x ?y))

There are 2 solutions:

  #1: ?X=JILL, ?Y=JACK

  #2: ?X=JACK, ?Y=JILL

STELLA> (retract (alive jack))

|P?|(ALIVE JACK)

STELLA> (retrieve all (married ?x ?y))

No solutions.





But by changing the definition of married as follows:


(defrelation married ((?x live-person) (?y live-person))


    :<=> (and (spouse ?x ?y) ))





I get an erroneous answer


STELLA> (retrieve all (married ?x ?y))

There are 2 solutions:

  #1: ?X=JACK, ?Y=JILL

  #2: ?X=JILL, ?Y=JACK

STELLA> (retract (alive jack))

|P?|(ALIVE JACK)

STELLA> (retrieve all (married ?x ?y))

There are 2 solutions:

  #1: ?X=JACK, ?Y=JILL

  #2: ?X=JILL, ?Y=JACK

STELLA> (retrieve all (married ?x ?y))

There are 2 solutions:

  #1: ?X=JACK, ?Y=JILL

  #2: ?X=JILL, ?Y=JACK



Just to check


STELLA> (ask (live-person jack))

UNKNOWN






Explanations not helpful:


STELLA> (set-feature justifications)

|l|(:JUSTIFICATIONS :EMIT-THINKING-DOTS :JUST-IN-TIME-INFERENCE)

STELLA> (retrieve (married ?x ?y))

There is 1 solution so far:

  #1: ?X=JACK, ?Y=JILL

STELLA> (why)

|kv|(<|i|@PRIMITIVE-STRATEGY,|i|@EXPLANATION-INFO>)

1 (MARRIED JACK JILL)

    follows





Nor does this:


STELLA> (set-feature trace-subgoals)

|l|(:TRACE-SUBGOALS :JUSTIFICATIONS :EMIT-THINKING-DOTS :JUST-IN-TIME-INFERENCE)

STELLA> (retrieve (married ?x ?y))

There is 1 solution so far:

  #1: ?X=JACK, ?Y=JILL



PATTERN: [F,F]

| GOAL: (MARRIED ?x ?y)

| SUCC: ?X=JACK ?Y=JILL truth=T






This is a bit disappointing since the ability of PL to classify
dynamically and have rules being applicable based on that dynamic
classification is very useful. In the above example, it does not seem
that the dynamic classification is happening.





I tried to force re-evaluation just in case the reevaluation of married needed a trigger:


STELLA> (process-definitions)

COMMON-LISP:NIL

STELLA> (retrieve (married ?x ?y))

There is 1 solution so far:

  #1: ?X=JACK, ?Y=JILL





but that didnt work...





Thanks


Srini

--- On Thu, 8/21/08, Hans Chalupsky <[email protected]> wrote:
From: Hans Chalupsky <[email protected]>
Subject: Re: [PowerLoom Forum] Unexpected Powerloom truth maintenance behavior....
To: [email protected]
Cc: "Thomas Russ" <[email protected]>, [email protected]
Date: Thursday, August 21, 2008, 4:09 PM

Yes, we have to see how to improve this.  Currently, the type
assertions inferred from the domains of a relation are handled by a
special mechanism if *type-check-policy* is
:AUTOMATICALLY-FIX-TYPE-VIOLATIONS (the default).  They are asserted
in the top-level module and not the inference cache, and we can't
blindly remove them, since they might have been asserted explicitly or
be the result of other assertions as well.  We only want to assert
them if we have to, which is why they are handled somewhat differently
from other inferred information.

One way to work around this for now is to set *type-check-policy* to
:REPORT-TYPE-VIOLATIONS and then assert all types explicitly, in which
case it is your responsibility to assert and retract them, but at
least you won't be surprised by PowerLoom doing things behind the
scenes.

Hans

>>>>> Thomas Russ <[email protected]> writes:

> On Aug 21, 2008, at 9:31 AM, Srini Ram wrote:

>> (defmodule "TEST"
>> :includes ("PL-USER"))
>> (in-module "TEST")
>> 
>> ;(clear-module "TEST")
>> (reset-features)
>> 
>> (defconcept person (?x))
>> (defrelation spouse ((?x person) (?y person))
>> :axioms (symmetric spouse))
>> 
>> (assert (spouse jack jill))  ; expect (person jack) (person jill) to  
>> be also asserted because of  domain of  person
>> 
>> (ask (person jack))
>> TRUE                                      ;; as expected
>> 
>> (retract (spouse jack jill))          ;; expect (person jack) to  
>> also be retracted by truth maintenance system
>> 
>> (ask (person jack))
>> TRUE                                     ;; unexpected
>> 
>> Am I missing something.

> No.  PowerLoom is missing something.
> This is a bug.

> I'm not sure about how to fix it, though.

> _______________________________________________
> powerloom-forum mailing list
> [email protected]
> http://mailman.isi.edu/mailman/listinfo/powerloom-forum

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