The difference is actually that the "not" in Rule1 doesn't have a "preceding pattern", and therefore Jess inserts "(initial-fact)", so that the rule won't work unless you've executed "(reset)" at the beginning of the session, as described in section 6.10 of the Jess 7.1 manual. See
http://www.jessrules.com/jess/docs/71/rules.html#not_ce On 1/6/12 8:40 AM, "Theodore Patkos" <pat...@ics.forth.gr> wrote: >Hello everyone and best wishes for the new year > >could someone please give me an explanation why the following two rules >behave in a different way, although they express the same logical >formula (i.e., not (Object ^ Pred) )? In fact, only the second rule >reaches correct conclusions, as I note below. > >(defrule Rule1 >(not > (and > ?o <- (Object (name B)) > (Pred (obj ?o)) >)) >=> >(printout t "OK1" crlf) >) > > >(defrule Rule2 >(or > (not (Object (name B))) > (and > ?o <- (Object (name B)) > (not (Pred (obj ?o))) >)) >=> >(printout t "OK2" crlf) >) > >The definition of facts could be like: >(deftemplate Object (slot name)) >(assert (Object (name A))) >(assert (Object (name B))) >(deftemplate Pred (slot obj)) > >where <obj> is the id of some Object fact, eg. > >(defrule Rule >(declare (salience 10)) >?o <- (Object (name A)) >=> >(assert (Pred (obj ?o))) >) > > >What I notice is that Rule1 behaves erroneously when the Object fact >exists in the KB, but not the Pred fact: although it is supposed to be >triggered, it is not! Rule2, on the other hand, behaves correctly all >the times. > >When both Object and Pred facts exist or when the Object does not exist, >both rules behave fine. > >So, what is wrong with the syntax of the first rule? No variable >definition is used outside the not pattern.. > >Thanks > >Theodore > > >-------------------------------------------------------------------- >To unsubscribe, send the words 'unsubscribe jess-users y...@address.com' >in the BODY of a message to majord...@sandia.gov, NOT to the list >(use your own address!) List problems? Notify owner-jess-us...@sandia.gov. >-------------------------------------------------------------------- -------------------------------------------------------------------- To unsubscribe, send the words 'unsubscribe jess-users y...@address.com' in the BODY of a message to majord...@sandia.gov, NOT to the list (use your own address!) List problems? Notify owner-jess-us...@sandia.gov. --------------------------------------------------------------------
