[rules-users] Using from

I have the following class structure. Class GrandFather { List<Father> fathers; public List<Father> getFathers() {return fathers;} } Class Father { int age; List<Son> sons; public int getAge() {return age;} public List<Son> getSons() {return sons;} } Class Son { int age; public int getAge() {return age;} } I'd like to write a rule that finds all the Fathers who have age > 45 and have Sons where the son's age is greater than 5. But I can't figure out how to use "from" to iterate over father first and then over son. Any help will be greatly appreciated. Thanks, --Aziz