He referenced the idea of code-locality when talking about associations in the model.
das-0036-what-goes-in-active-records#thin-layer-over-activerecord1 Often his goal when adding a method to a Active Record class is to add a thin layer over the database stuff. The goal of that later is to provide terminology that is more of a match for the application logic than the underlying database table and row names. das-0036-what-goes-in-active-records#thin-layer-over-activerecord1
His rule of thumb for wrapper methods in Active Record is that they do not introduce logic, but wrap a single (or possibly composite multiple) attributes.
His policy is that he will not call the #where_method outside the Active Record class because it couples him to the database field names, etc.
He talks about creation-methods that function a lot like factory methods. I just wanted to make note of the naming convention.
A list of what he likes to have in AR is: