Early in the development of FitNesse, we drew a boundary line between business rules and databases. That line prevented the business rules from knowing anything at all about the database, other than the simple data access methods. That decision allowed us to defer the choice and implementation of the database for well over a year. It allowed us to try the file system option, and it allowed us to change direction when we saw a better solution. Yet it did not prevent, or even impede, moving in the original direction (MySQL) when someone wanted it.
