>Hi,
>
>I am looking to re-write one of my applications, currently written in VFP6, and would like to take some time to consider the design of the new version. What i'm really looking for is a good reference book\site for writing n-tier solutions which can help me make a decision.
>
>What I would really like to have at the end is an application that can run on either Oracle\SQL Server with a front end that acts more like a skin which can be changed quite quickly and without having to re-write all the business rules. At the moment I havent decided what technology this will be written in, that sort of depends on the research that I'm doing now. From what I've described I can see that the Business rules will sit in between the Front End and Database but really want to see some basic examples of how this could be put into practice.
>
>One of the reasons I am asking this is because I have seen an application written in VB.Net which uses a web services for pretty much exactly that reason. The application was clumsy and very slow and far to much code seemed to be held in the client appplication, therefore making changing the front end far more difficult. I'm not saying that this is a slow technology just that the way it was implemented for this application seemed to be ill thought out and I would like to avoid making the same mistakes.
>
>Any links to good references would be much appreciated or any general comments on past experiences of doing something similar would be great.
>
>Blimey, this is the longest message I've ever posted, if you've got this far without falling a sleep then your a better person than me!!

If VFP is still an option, my understanding is that some of the current commercial frameworks such as Visual FoxExpress, CodeMine etc. support multi-tier development, different back-end DBs etc. Some of them used to have 30-day free trial periods as well.