Please guide me to implement following rule.
I would like to found out the city where absence of either Male or Female
found for same age. I also need to have ref to those Men and Female of that
city in collection to use it RHS. Also there will be max of one male &
female for same age.
$city : City( name == "paris" )
not Person( age == 25, sex == "female", city == $city )
For the other Qs look into collect and accumulate.