Models That Don't Work
Interactive models are difficult to implement in the web environment. Server-side scripts are impractical for this task, since an HTTP request and response is required to validate each field that's entered. This is usually unacceptable, because the user is required to submit the data after entering each field, response times are likely to be slow, and the server load high.
Client-side scripts can implement an interactive model. However, validation on the client should not be the only method of validation because-as we emphasized in Chapter 5-the user can passively or actively avoid the client-side processes. We discuss the partially interactive solution of including client-side scripts with an HTML <form> later in this chapter.