After reading the transcript of Craig Berntson's n-Tier lecture last Wednesday (which was very informative and useful), I have a number of philosophical questions about n-tier design, and I was hoping some of you had some experience or ideas that could guide me and others like me in n-tier development.

1) Messaging between tiers - This is my biggest issue. How do I communicate data changes between my interface tier and my business logic tier? I've played around with a number of ideas, like binding UI controls directly to biz tier properties. That doesn't feel quite right - it assumes to much interdependence between the UI and the business tier.

I've also played with a SETVAL method in the business tier, so that every time there's a change in the UI, it calls this SETVAL method and tells oBiz of the change. This combined with a GETVAL method to retrieve the values of other properties in oBiz works pretty well, but it comes with it's own set of problems.

And finally, what about populating grids in the UI? Sometimes a user might change a value, which affects a bunch of values in the grid. Assuming oBiz handles the logic, how does one best handle the changes to the cursor or table which populates the grid? So far, I've been passing datasessionid's to the biz object so it can update the cursor in the appropriate form, but something feels a little off about this.

2) There was some discussion in Craig's lecture about what the middle tier should be. I think COM was the consensus. But Mike Helland asked a great question - why? Why do people think it should be that way? What's wrong with a separate class library that's just your business tier, and compiling them all into one app? In fact, especially if all the data is VFP, I can't see why one wouldn't do it this way. All my apps work this way, and frankly, it works great. I have no interest in using many of the MS tools available to me (i.e. MTS, ADO, etc.), because for me, they change RAD to SAD (Slow Application Development).

3) Finally, I'm sure there must be some books/articles which generically discuss n-Tier design, and the associated patterns/anti-patterns. I've found a few patterns books, but they're so *$^#&$ dry that I have trouble getting through them. Anyone have any advice on where to find good discussions of this topic.

Thanks in advance for your thoughts.