You're right. It kind of depends on whether you look on the DB as a datastore, that is the DB and the Rails app are the same "system" with regards to other parts of the infrastructure, or of the database is system by itself, that provides services to other systems.
It depends on what the DB does, really - eshop app + db might be the first one, while operational data warehouse would be the second. Usually you end up with something in the middle - like the eshop app, that provides views with summarized data to be ETLed to reporting.
It depends on what the DB does, really - eshop app + db might be the first one, while operational data warehouse would be the second. Usually you end up with something in the middle - like the eshop app, that provides views with summarized data to be ETLed to reporting.