>>If you want strict compliance of the "defined once" rule, the front-end can query the middle tier for all field sizes, etc. However, this kind of information is usually duplicated for practical purposes (avoid extra trips to the server, and simplify development)
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>Thanks for the reply. My problem with 3-Tier is the strict non-dupliating rule. I don't know if I break the rules if I add size code to my presentation layer and also to my middle layer. I want to do the best I can for this project and to get as close to a 3-tier app as I can. So I want to avoid pitfalls if possible.

In real world 3-Tier apps, there are many compromises (abstract "perfection" vs. complexity & performance) which require common sense to find the right point. No matter how hard you try, there's always SOME degree of duplication: i.e. both the presentation tier and the middle tier need to know, in a redundant way, which are the fields, their name and type, etc.

In this particular case, I dont think knowledge of the maximum length adds a significant risk to the app maintenance; again others can disagree.

The main point I want to make is... IMO there's no such thing as a "perfect" 3-tier application (if you want it delivered some day, with some acceptable performance); you'll have to negotiate on several issues.

Regards,