[rules-users] Testing for non-existance of an object in list

Hi all I'm still struggling with the handling of lists and membership in the LHS of rule. I'm trying to formulate a rule that only fires if a certain object is not yet a member of a list. Here's what I currently have (Drools 5.5.0 btw): rule "R2030: UpdateDQAttribute" dialect "mvel" agenda-group "PROCESS_CHECKRESULTS" when pv : PriceViolation ( p : changedPrice.price, dqc : check ) ps : PriceSeries ( id == p.seriesId ) i : Instrument ( id == ps.instrument.id ) dqa : DQAttribute ( rootId == i.id, objectId == p.id ) not dqcv : DQCheckViolation ( check.id == dqc.id ) from dqa.checkViolations then # debug for (DQCheckViolation dqcv : dqa.checkViolations) { logger.debug("dqc: {}, dqcv: {}", dqc.id, dqcv.check.id); } end The rule fires and the log statement produces PriceCheck: dqc: 6fc6636b-9b7c-4302-bce7-1680eec57830, dqcv: 6fc6636b-9b7c-4302-bce7-1680eec57830 The ids are the same, so I would have expected that last LHS condition to avoid that the rule fires. -- CU, Joe