Re: [rules-users] Locating facts via slot values

Hi Wolfgang, Is it the number of instances or how often they are modified that makes the difference? I am just wondering why it is better. Best Regards, Michal 2009/4/3 David Sinclair <dsinclair(a)chariotsolutions.com&gt; Here you go WolfGang > > rule shoot-3 > when > $h : Hunter( $target : target) > Animal(this == $target) > then > $h.shoot( $a ); > retract( $a ); > end > > 2009/4/3 Wolfgang Laun <wolfgang.laun(a)gmail.com&gt; > >> Given a working memory containing a large number of rather static facts >> which are from several subclasses (Ape, Bear, Crocodile,...) of some base >> class (Animal) and a single fact of class Hunter with a field target of type >> Animal, the shooting of an animal might be written with a rule like this: >> >> rule shoot-1 >> when >> ?h : Hunter( ?target : target ) >> ?a : Animal() >> eval(?target == ?a) >> then >> ?h.shoot( ?a ); >> retract( ?a ); >> end >> >> Avoiding eval (which is said to be inefficient), it could also be written >> as >> >> rule shoot-2 >> when >> ?a: Animal() >> ?h : Hunter( target == ?a ) >> then >> ?h.shoot( ?a ); >> retract( ?a ); >> end >> >> This, however, places the pattern with many instances up front, which is >> (AFAIK) not so good in a Rete implementation. >> >> Which one is to be preferred in Drools? >> >> Ideally, one might want to write >> >> rule shoot-3 >> when >> ?h : Hunter( ?target : target ) >> ?a == ?target : Animal() ### not valid DRL >> then >> ?h.shoot( ?a ); >> retract( ?a ); >> end >> >> This avoids eval, has the single instance fact up front, but it isn't >> available. >> >> -W >> >> >> >> >> _______________________________________________ >> rules-users mailing list >> rules-users(a)lists.jboss.org >> https://lists.jboss.org/mailman/listinfo/rules-users >> >> > > _______________________________________________ > rules-users mailing list > rules-users(a)lists.jboss.org > https://lists.jboss.org/mailman/listinfo/rules-users > > _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users