Hiya JimB

>
>Not necessarily. My business tier may have data driven rules enforcement and the only change required is the meta data for the business tier.

I have found that you can avoid a lot of problems if you standardize messaging between objects. I try like heck to avoid relying on custom object properties and methods (even though it's impossible to totally avoid). So, my apps "know" that to check a bizrule violation in an object, they need to check an Alert property for the violation.

In short, I try to pack base functionality into a superclass where possible. My subclasses are actor specific and have certain behavior.