Below is a very simple rule that binds a variable to a map value... rule "how many times is map.get() called?" when p:Parameter( $value:tags[1]==1, $value == 1, $value != 2, $value != null, $value in ("1","2") ) then System.out.println("value=" + $value); end The problem is map.get() is called 6 times when executing this rule using a Stateless session. To test this I implement a mock Map that the get(key) simply returns the key. So in this example tags[1] return 1. And in the get() I simply print a test message to see how many times it's been called. Here is the sequence... 1x = tags[1] 2x = tags[1] == 1 3x = $value == 1 4x = $value != 2 5x = $value != null and most surprisingly none for $value in ("1","2") but 6x == System.out.println("value="+$value) Is this a bug? It's a huge problem for my application since the call to get() is expensive for my map implementation. Thanks --ming