One thing I am having a hard time wrapping my head around is how to reliably integrate business logic into a system like this. Just hook up my Rails models etc. and have it use those?

Let’s say I’ve got a “widgets” table and I want the system to tell me how many “deprecated widgets” there are, but there is no convenient “deprecated” flag on the table—it’s defined as a Rails scope on the model or something (business logic).

The DB schema might make it possible to run a simple query to count widgets or whatever, but I just don’t have a good mental model of how these systems might work with “business logic” type things.