I have a question regarding order of operations in the consequence of a rule when using the mvel dialect. When executed the Drl below provides Right =30.0 and Wrong =140.0. The only difference is the parens around the multiplying expressions, which shouldn't be necessary given order of operations. Is this a problem with the drools/mvel interaction or is it completely an issue with mvel? Is the general expectation that all expressions must be completely scoped by parens when using mvel? package test; dialect "mvel" rule "test 11" when then double rightVal=((10-5)2) + (5(8-4)); double wrongVal=(10-5)2 + 5(8-4); System.out.println("Right ="+rightVal); System.out.println("Wrong ="+wrongVal); End After execution: Right =30.0 Wrong =140.0 Thank you for all of your help. We are using drools 4.0.4. Joe Also, I haven't figured out how it arrives at 140. The following format also produces 140, which seems a little more strange. double wrongVal=10-5*2 + 5*8-4;