Borland® Delphi™ 6 Developer's Guide

Classic Mistakes

The most common mistake in creating a multitier application is introducing unnecessary knowledge of the data tier into the presentation tier. Some validation is more suitable in the presentation tier, but it's how that validation is performed that determines its suitability in a multitier application.

For example, if you're passing dynamic SQL statements from the client to the server, this introduces a dependency for the client application to always be synchronized with the data tier. Doing things this way introduces more moving parts that need to be coordinated in the overall multitier application. If you change one of the tables' structures on the data tier, you must update all the client applications that send dynamic SQL ...