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;

Very good basic advice of how to write rules for a rete engine can be found in this place <http://www.jessrules.com/jess/docs/71/rete.htm>;. You'll also find a discussion of the technical details in the Drools Expert part of the manual. -W 2009/4/3 Michal Bali <michalbali(a)gmail.com&gt;

Quinn, Dan wrote: no, after a query the memory should return to before the query was executed. If it's not, then there is a memory leak, maybe the retracting of the query driver is not happening. If you look at the query method, it just inserts a DroolsQuery object and retracts it and gathers up the results inbetween. If you have jprofiler you can have a good idea if the DroolsQuery object is getting GC'd, or if they are building up. Mark

Mark, We were using JRockit's Mission Control to monitor memory. The working memory footprint just kept growing even though we were only querying working memory and weren't adding new facts. I'm new to the Mission Control application and couldn't figure out how to configure it to verify queries were causing the footprint to grow. I just made that assumption since we were only querying working memory and not adding new facts. I will look into it more today, and use JProfiler to verify queries are causing the footprint to grow. If I verify that, I will put together a use case that demonstrates the problem. Thanks for looking into this for me. Thanks, Dan Daniel Quinn Fedex - Custom Critical Software Specialist I 234.310.4090(x2586) ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Mark Proctor Sent: Thursday, April 30, 2009 9:13 PM To: Rules Users List Subject: Re: [rules-users] queries in Drools 5.0 Quinn, Dan wrote: We are writing an app which has a large number of facts. This app also needs to make lots of queries against working memory. Our memory footprint seems to be expanding at an undesirable rate due to the number of queries made against working memory. It is increasing at a rate where after a couple of days the app will consume all the resources on the machine. This app is stateful and needs to stay up for a long duration. Rebooting it every couple of day to clean up working memory would not be acceptable. It seems to me that the queries are being added to working memory as facts, but the query is not retracted after its result is returned. Is that true? Is there something I need to do so query facts are removed after the results are returned to keep the size of working memory down? Has this behavior changed since Drools 4.0.7. I don't recall seeing this issue running against the older version of Drools. no, after a query the memory should return to before the query was executed. If it's not, then there is a memory leak, maybe the retracting of the query driver is not happening. If you look at the query method, it just inserts a DroolsQuery object and retracts it and gathers up the results inbetween. If you have jprofiler you can have a good idea if the DroolsQuery object is getting GC'd, or if they are building up. Mark Thanks, Dan Daniel Quinn Fedex - Custom Critical Software Specialist I 234.310.4090(x2586) ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of David Sinclair Sent: Friday, April 03, 2009 3:20 PM To: Rules Users List Subject: Re: [rules-users] Locating facts via slot values 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