Data Validation Should Occur at Multiple Tiers within an N-Tier Architecture

Data can be represented in many forms, including EDI streams, XML documents, and SOAP messages. Validation in these scenarios should occur before data are sent across the network. This reduces errors within a distributed architecture and can increase performance in many situations. For example, if a GUI-based application captured user-entered data in a data entry screen, this can be corrected before data are written to the database. In a distributed environment, it may be more efficient to validate the data within the GUI instead of it having to travel through multiple and geographically dispersed systems, only for it to be rejected by a database constraint.

For best practices on validation in the presentation layer, see Chapter 9, Presentation Tier Architecture.