Hi Jim,

Just juimping in here -- seems like a good place -- to point out that the notion of business rules in OO systems is deep and there are no universal answers, and possibly no suitable answers, to most general BR design questions.

Ron Ross, who is Mr Business Rules au Max, has said:

  "Objects are fine for non-persistent things, like GUIs and service 
   providers, but anything that has to do with knowledge and persistence, 
   objects are not the right answer. Business rules are the Achilles' heel 
   of object orientation for business database applications".

I think all we can really do is point out that there are many types of business rules, see http://www.guide.org/ap/apbrules.htm and that it's not yet even clear what it's all really about, see http://www.adtmag.com/pub/mar97/softeng.htm.

Which is not to say that the ongoing debates aren't interesting, see for example http://c2.com/cgi/wiki?TooMuchGuiCode

ANyway I see no evidence anywhere to support the notion that all business rules should run on a middle tier. It sounds logical, and it's a reasonable presumption, and probably a decent rule of thumb, but it's never been practically demonstrated one way or another.