Assertion followed by retraction leads to error state...

I am experimenting with default truths and retraction...



STELLA> (presume (person jim))   ; assume that jim is a person

|p|(PERSON JIM)

STELLA> (ask (person jim))

TRUE

STELLA> (assert (not (person jim)))  ;; we are told
specifically that jim is not a
person             


|P|(NOT (PERSON JIM))



STELLA> (ask (person jim))          ; ok

FALSE



STELLA> (retract (not (person jim)))  ;; retract

|P?|(PERSON JIM)



STELLA> (ask (person jim))

UNKNOWN                                    
;; wrong, we still have the presume

                                                     
;; so by adding and retracting a fact we wound up

                                                     
;; at a different state from where we started



What I would like to happen is that new facts should be able to
override old facts for cases where something can either be true or
false...Since jim is either a person or not a person, I should not have
to remember that I asserted that jim was not a person, and have to
retract it before asserting the new knowledge that jim is in fact a
person..From a maintenance perspective, this simplifies life a lot if
we can assert new knowledge and have it simply replace prior (default)
knowledge.



I tried to use presume above to achieve this goal..but it doesnt seem to work.



Thanks

Srini







Thanks

Srini

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