Last friday, I had the next situation. In drools 4.0.7 I had the expression: new double[]{-1, 1} And it worked. But in Drools 5.0 I had to erase the blank space (before "1" and after ","), because I was getting a warning message, during knowledge base building : "line 29:114 extraneous input '1' expecting RIGHT_CURLY" and an exception, during rule execution : "org.drools.runtime.rule.ConsequenceException: java.lang.IndexOutOfBoundsException" So the working expression for Drool 5.0 was: new double[]{-1,1} -- Luis Enrique Silva Valdivieso