newb question regarding activerecord relationships

Hi Guys, I've tried searching for this, but haven't come up with the answers. Sorry, this is a basic question, so sorry for the newb-ness.

Ok so I'm putting together a ruby report that uses ActiveRecord. I will explain some details below:

So I have an Payment object which inherits from ActiveRecord: Payment belongs to invoice id, invoice_id, amt, date, type

Then I have 3 payment types; Initial, Recur, and Refund that inherit from Payment. The only differences are that each overrides the type field.

So my question is this the correct way in setting this up... with only a payments table with a type field?

I essentially want to do this: Initial.find(:all) and it will pull all payments with type Initial... instead of doing Payment.find(:all, :conditions...)

Thanks.

Nevermind.. found what I need to search for. STI (Single Table Inheritance).

Thanks!