That's probably it, but my mind is blanking on the definition of time-constant as it would apply here. howOld() is doing a simple calculation of the difference between the current time and the timestamp value that was set in statusRequested however many x seconds ago. So based on your feedback, I'm assuming the inline eval isn't seeing proper timestamp value since its last change. But the top-leve eval can. -A ________________________________ From: rules-users-bounces(a)lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Edson Tirelli Sent: Wednesday, December 10, 2008 10:45 AM To: Rules Users List Subject: Re: [rules-users] Finicky eval statements Is your inline eval() time-constant? I would guess that "howOld()" is returning different values when executed at different times. Inline evals MUST be time-constant. Top level evals can deal with non-time-constant expressions. []s Edson 2008/12/10 Bagwell, Allen F <afbagwe@sandia.gov<mailto:afbagwe@sandia.gov>> I'm puzzled over the proper use of in-line evals. I've used them successfully in some places. But it seems that on occasion something doesn't work when I think it should. First, this is a when clause that works properly using a separate eval statement. The rule activates and fires when expected: $rt : RuleTimer(uniqueName == "Hardware Status Request", timedOut == true) $hw : Hardware($activelyMonitored : activelyMonitored, command == null) AttrBoolean(this == $activelyMonitored, currentValue == true) eval($hw.getStatusRequested().howOld() > $hw.getStatusPeriod()) However, this re-write changing to an in-line eval never fires. $rt : RuleTimer(uniqueName == "Hardware Status Request", timedOut == true) $hw : Hardware($activelyMonitored : activelyMonitored, command == null, eval(statusRequested.howOld() > statusPeriod) ) AttrBoolean(this == $activelyMonitored, currentValue == true) Likewise, this re-write doesn't fire either where I sought to bind the more complex statusRequested object to a Drools variable before using it in the eval. The field statusPeriod just holds a primitive double. $rt : RuleTimer(uniqueName == "Hardware Status Request", timedOut == true) $hw : Hardware($activelyMonitored : activelyMonitored, $sr : statusRequested, command == null, eval($sr.howOld() > statusPeriod) ) AttrBoolean(this == $activelyMonitored, currentValue == true) I haven't been able to find anything in the manual that says these other two syntaxes are wrong. Furthermore, the Drools compiler has no issues with them. Thanks! Allen F. Bagwell e-mail: afbagwe@sandia.gov<mailto:afbagwe@sandia.gov> phone: 505/284-4517 fax: 505/ 844-7886 Ask your doctor if medical advice from a TV commercial is right for you. _______________________________________________ rules-users mailing list rules-users@lists.jboss.org<mailto:rules-users@lists.jboss.org> https://lists.jboss.org/mailman/listinfo/rules-users -- Edson Tirelli JBoss Drools Core Development JBoss, a division of Red Hat @ www.jboss.com<http://www.jboss.com>