Here is the code snipet. rule "Validation" when $claim: Claim($cos: claimIdentificationInfo.categoryOfService !=null); $claimId: ClaimIdentification($cos not in ("01","03","04"), $cos.length >0); then log.info("Executing Rule: Validation ............."); end Above code works if - $cos in ("01","03","04") -$cos.length But when I put not in front of in ("not in"), it throws exception like this... Unable to build constraint as '$cos' is invalid : [Rule name='Validation']