RuLa allows you to write quite complicated conditions and formulas. Here are some recipes or snippets or useful RuLa statements to use:

Check if more information than expected is missing

Let's say we expect first_payment_* information to be missing in a certain step, but nothing else. Heres a recipe how to check for exactly that:
CASE.missing_information_keys - [
) > 0
We are using CASE.missing_information_keys for Atfinity to tell us the keys of information still needed but missing in the current case. With INF.key() we then compare these keys to the keys of information we expect to be missing in the case. Finally, we use the "infix set difference operator ", the minus, to see if the list of missing_information_keys is empty after the remove all the known missing information and count the elements in this list.