I would have thought using some rule like this would solve your problems? Rule "identify non-overlapping intervals" When $i: Interval() not exists Interval( ( this.intersects($i) ) ) Then //Add $i to database End Rule "identify overlapping intervals" When $i: Interval() $ii: Interval( ( this.intersects($i) ) ) Then //$i intersects $ii End "This" is only available in v4, but I'm confident these rules can be written in v3 syntax too. Perhaps I have misunderstood your requirement. With kind regards, Mike -----Original Message----- From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Aeternitas Sent: 26 June 2007 16:14 To: rules-users(a)lists.jboss.org Subject: [rules-users] how to return additional information from method in'eval' Hello. I have the following problem: Let's imagine we have type like this - public class Interval{ private long start; private long end; private int usage; ... } Now I need to insert in DB new Interval, but before doing it I have to check, whether DB doesn't have any interval, which intersects new one and satisfies some rules (e.g. rules for summ of usage...). I use eval for it - I have method, which can check it using DB services etc. But... eval can return only boolean... I want to know also why I can't insert this interval (e.g. which intervals prevent to do it). For me it will be comfortable to do something like this: when ... # $intervals - collection of intervals, which intersects new interval $intervals : eval(newInterval) #<check whether size of intervals is great than 0> then # We can insert such interval and using global variable we inform about it. 'error' it is collection of # mistakes error.add("new interval can't be inserted because of " + <some information from $intervals> ); But it will not work (or maybe new engine, version 4, will allow such 'eval' using ?). Could you advice anything? (Method, which I use in eval have no access to the working memory, so I can't use global variables. Also I don't want to fire such method again in "then" section to know "why I can't insert new interval")... I hope I have described my problem clearly. Thanks in advance Maxym -- View this message in context: http://www.nabble.com/how-to-return-additional-information-from-method-i n-%27eval%27-tf3982935.html#a11307462 Sent from the drools - user mailing list archive at Nabble.com. _______________________________________________ rules-users mailing list rules-users(a)lists.jboss.org https://lists.jboss.org/mailman/listinfo/rules-users