I think you have misunderstood (or at least one of us has!) The "transaction consistency" rule consists of four patterns:- 1 - Transaction ( $id : id) pattern. 2 - The "$credit : Double() from..." pattern 3 - The "$debit : Double() from..." pattern 4 - eval( ! $credits.equals( $debits ) ) The rule will only be activated when all patterns match. IMO, I think of "accumulate" as a nested rule: the "action" will fire when the pattern following the "accumulate (..." matches. Therefore pattern 2 above is matched when the "accumulate" returns - i.e. it is always matched. The same for patterns 1 and 3. Pattern 4 is only matched when the credits and debits don't equal. So for 100 Transaction facts and 10 TransactionEntry facts per each of 10 unique id's the rule will be activated once per pattern 4 match. Pattern 1 always matches; pattern 2 always matches and pattern 3 always matches. Although pattern matches 100 times, pattern 2 matches 10 times per id and pattern 3 matches 10 times per id. I think it is different to consider pattern matches versus rule activations. I hope this helps!??! - or I'm completely wrong ;-) Cheers, Mike -----Original Message----- From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Olenin, Vladimir (MOH) Sent: 22 February 2007 14:52 To: Rules Users List Subject: RE: [rules-users] accumulate / collect behaviour question - another stupid question >So, you are right: action will be executed 10 times for each id and > > eval >will be executed 1 time for each id. > > Hmm... So, the 'action' part of the _rule_ (NOT of the accumulate statement) will be called 100 times? How should the rule be modified for the action to be called only 10 times? (once per each unique transaction id). Basically the idea is to do smth if all debit operations are not balanced with credit operations within the same transaction id.... Or have I misunderstood -----Original Message----- From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Edson Tirelli Sent: 21 February 2007 17:19 To: Rules Users List Subject: Re: [rules-users] accumulate / collect behaviour question - another stupid question Vlad, Inside an accumulate CE, the action code will be executed once for each match of the given pattern (TransactionEntry in this case). Eval CEs are executed once for each tuple that matches all previous patterns. So, you are right: action will be executed 10 times for each id and eval will be executed 1 time for each id. To understand better how forward rule engines work, there are some books and articles listed in JBoss Rules project page. I can personally recomend "Expert Systems..." by Gary Riley. And don't worry about asking. Usually people ask a lot in the begining and then when they feel confident, they start to answer more than ask. :) []s Edson Olenin, Vladimir (MOH) wrote: >Hi, > >Edson quoted the following sample rule some time ago: > >rule "transaction consistency" > >when > >Transaction( $id : id ) > >$credits: Double( ) > >from accumulate( TransactionEntry( id == $id, operation == "credit", >$amount : amount ), > >init( double balance = 0 ), > >action( balance += $amount ), > >result( new Double( balance ) ) ); > >$debits: Double( ) > >from accumulate( TransactionEntry( id == $id, operation == "debit", >$amount : amount ), > >init( double balance = 0 ), > >action( balance -= $amount ), > >result( new Double( balance ) ) ); > >eval( ! $credits.equals( $debits ) ) then > >// inconsistency for transaction $id > >End > >If there are 100 transactions overall and only 10 unique transaction >ids (eg, id = 1..10), so that we have on average 10 Transaction facts >per id, > >- how many times will 'eval' be called? > >- how many times will the action be called, assuming 'eval' always >returns 'true'? > >I guess the answer for the above should be '10 times', once per each >id? What if I put another eval statement like "eval($id == 1)" after >existing 'eval'? Would that be evaluated 100 times (for all >Transaction facts) or only 10 times (once per unique id)? > >I think I'm missing quite significant piece on how tuples are selected > > >in DROOLS and how 'eval' and new 'from accumulate' features work.... > > Any >pointers would be greatly appreciated! (would some general literature >on rule engines help to clear up this types of questions?...) > >Thanks, > >Vlad > >PS: sorry for posting so many questions and answering so few..... > >----------------------------------------------------------------------- > > - >_______________________________________________ >rules-users mailing list >rules-users(a)lists.jboss.org >https://lists.jboss.org/mailman/listinfo/rules-users > > > >