[rules-users] Ask for help on rule authoring

Hi, I got the following rule problem. The rule is like : 1. | rule "Rule1" 2. | dialect "mvel" 3. | when 4. | ad : ApplicationData( age == "null" , age.size() == 0) 5. | then 6. | ad.setReturnMsg( "age should not be null or empty" ); 7. | end where setReturnMsg is a method of ApplicationData Fact(); However, I got the validation error : [Rule1] [ERR 101] Line 4:49 no viable alternative at input ')' in rule "Rule1" in pattern ApplicationData [Rule1] [ERR 102] Line 4:51 mismatched input '==' expecting ')' in rule "Rule1" in pattern ApplicationData Please help what the problem is. Thanks