Re: [rules-users] Can only reason over sub-objects if you use the FromConditional Element

Hello, Mike, The behavior is identical whether I update the sub-object or not -- the "good" rule always works as long as I update the root person object AND the "bad" rule will not work even if I explicitly update the sub-object as you've suggested. This leads me to interpret the engine behavior as: 1) An update() to a root object is enough to communicate to the rules engine that the entire object graph has (potentially) changed 2) The engine will properly reason over sub-objects only if you use the From conditional element (but not if you use MVEL sub-property expressions) So if (1) is the intended behavior of the engine, then my question is still this... is (2) a necessary constraint? Shouldn't the engine be able to reason over MVEL sub-property expressions without requiring the From conditional element? If so, it makes for a more direct syntax to allow MVEL sub-property expressions in the LHS, doesn't it? Thanks in advance for any help on this! Aaron On Mon, Mar 17, 2008 at 4:08 AM, Anstis, Michael (M.) <manstis1(a)ford.com&gt; wrote: > IMO, you have not informed the engine\RETE network that details have changed > in your first example. > > This would probably be a better example:- > > > rule "30 is the new 20" > when > person : Person( $d : details.age == 30 ) > > then > person.getDetails().setAge(20); > System.out.println( "Now 20 : " + person ); > update( person ); > update( $d ); > end > > The From works because it gets external data rather than using that already > in the engine\RETE network. > > IMO, I think the rules are working correctly; it's just a misunderstanding > of how the engine\RETE network function. > > I hope this helps. > > Thanks, > > Mike > > > > -----Original Message----- > From: rules-users-bounces(a)lists.jboss.org > [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Aaron Dixon > Sent: 14 March 2008 20:51 > To: Rules Users List > Subject: [rules-users] Can only reason over sub-objects if you use the > FromConditional Element > > It appears that you MUST use the From Condition Element to reason over > sub-objects. > > I have a Person class. Person::getDetails() returns a Details > instance, which has the name and age of the person. (This is a > contrived example to demonstrate the issue.) > > My rules are: > > rule "30 is the new 20" > when > person : Person( details.age == 30 ) > then > person.getDetails().setAge(20); > System.out.println( "Now 20 : " + person ); > update( person ); > end > > rule "Older than 20 - Good" > salience -100 > when > person : Person( ) > Details( age > 20 ) from person.details > then > System.out.println( "Older than 20 (good) : " + person ); > end > > rule "Older than 20 - Bad" > salience -100 > when > person : Person( details.age > 20 ) > then > System.out.println( "Older than 20 (bad) : " + person ); > end > > I assert Abe, Bob, Cat, Don, and Eve with ages of 10, 20, 30, 40, and > 50, respectively. The output is as follows. > > Now 20 : Person(Details(Cat,20)) > Older than 20 (good) : Person(Details(Eve,50)) > Older than 20 (bad) : Person(Details(Eve,50)) > Older than 20 (good) : Person(Details(Don,40)) > Older than 20 (bad) : Person(Details(Don,40)) > Older than 20 (bad) : Person(Details(Cat,20)) > > > You can see that the "Bad" rule is more concise but it does not use > the From Conditional Element and therefore it doesn't work properly > (Cat is determined to be older than 20 when she is not.) > > Why does Drools allow the "Bad" rule to be written and compiled when > it does not behave properly? > > Thanks, > Aaron > _______________________________________________ > 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