[rules-users] LHS Conditional Syntax for drl - date comparison with objects

I'm having a hard time understanding the syntax in the conditional or left hand side of the DRL. Is it acceptable to use dot notation in the LHS? Is there a better way to compare fields on different objects? In the example below, I get an error "Unable to find class $d1. What limitations are there syntactically on the left hand side? Any help would be greatly appreciated. I have looked at all the examples and have googled the problem and don't seem to find the answer. package com.rules #list any import classes here. import com.validate.Date1 import com.validate.Date2 import java.util.Date #declare any global variables here rule "Your First Rule" when $d1 : Date1() $d2 : Date2() $d2 : Date2(beginDate > $d1.getEndDate) then #actions System.out.println("do something"); end Best regards, Robert Costello