Graig,

>I come back to my stance that a middle-tier is not much good as a class dropped onto a form. One of the advantages of doing things in n-tiers is that you can change one tier without affecting the other. As a VFP class droppped on the form, if you change the biz class, you then have to recompile the form....thus changing it. You now have to redistribute a new EXE to every desktop. IMO, there aren't lots of advantages doing things that way.

I've been hearing such argument for a long time and I still don't get it.
1. If your middle tier changes, you'll have to replace the middletier software.
2. If the front tier changes, you'll have to replace the front-end software.

With both you've:
- got to interrupt the system, and get everyone out.
- got to replace the software

We all know the mechanism where a client searches the network for a new version of the front end executable, so distribution of both would be simular.

With the one (or two)-tier approach (IOW there is no middletier) replacing the executable might be even simpler: Just drop it on the network and it will be picked up by each client when it starts the next time. IF no data structures has been changed this approach would not require anyone leaving the database system when the new executable is installed,

Sure N-tier has its place, but not many do seem to understand what N-tier exactly means. Everyone thinks in terms of frontend data storage and business rules, etc. But when you look at the model you use with Crystal Reports you'll discover that you're doing N-tier also. For the same reason:

Mailmerge (of a DBF, TXT, CSV datafiles) with word via automation = 3 tier.
Automating MS access = 3 tier
Automating MS Excel = 3 tier

Now look at my application, that uses VFP databases exclusively, but uses automation to MS office and Crystal Reports. Is it N-tier ? Is this 2-tier ?

I guess many would say 2-tier. O.K. lets take the following step: Attach a SQL server database to Crystal Reports and make reports out of it. Is this 2 Tier or 3 tier ? The point is that an application can both be 1 or 2 tier and N-tier depending from what angle you look at it.

If you look at it this way the characteristics of N-tier becomes more clear than talking about business classes, SQL server etc. However if you look at the differences between building middle tiers for a database and the automation servers (e.g. of office) you'll see that the automation servers are a part of a product that also has a life outside the tiers. For the database N-tier approach it has not; it's goal is to be a middle tier exclusively. To me this is a reason, to question the need of the N-tier. Of course if you need the users to be shielded from the datasource, or you need to instantiate objects (tiers) on other remote computers (e.g. internet etc) the N-tier is an attractive appraoch. If this is not the case (and you see it will not be in the future) then the N-tier will likely be more of a overhead than it will help you.

Walter,