>Hmm..would an N-Tier design that had 3 layers be about the same as a 3-tier design? N-Tier indicates any number of tiers...but why would you need more than 3? Just wondering what the conceptual differences are here.
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>If you were designing a system that could be accessed through a VFP, Visual C++, or HTML frontend and local or remote data on the back-end this would be a good candidate for an n-tier design, no? In this example I suppose you would create an active-x server for your middle tier containing your bizobjs which would then request the data from the backend and serve it up to the frontend. You would perhaps have bizobj subclasses specific to the type of data you need to return. For example you would need a bizCustomer bizobj that could return data to a VFP f.e and another one that could format for HTML, etc. Am I on target at all here?
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>Well, enough rambling for one post.
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>Cheers!

Michael,

The N in N-Tier represents any number 3 or larger. Additional tiers that might be part of the design can be Operating system interface, communications interface, etc. There was a series of articles in teh Communications of the ACM about a year ago. One of these described a frmaework for the banking industry where the "middle" tier objects were layered.

This system had a middle tier object for each department in the bank and an object for each division in the bank and one for the whole bank. The premiss was that for the bank an account had certain universal properties, and within a division there were more properties of an accoutn that were universal for the division, at the department level it was possible to even further sepcialize the account object.

So they build a framework that stacked the bus objs, the department object talks to the division object that talked to the bank object that talked to the database.

So, in answer to yoru question, N-Tier and 3-Tier are the saem thing, only 3-Tier is more specific.