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外文翻译 Dynamic Web Documents So far, the model we have used is that of Fig. 6-6: the client sends a file name to the server, which then returns the file. In the early days of the Web, all content was, in fact, static like this (just files). However, in recent years, more and more content has become dynamic, that is, generated on demand, rather than stored on disk. Content generation can take place either on the server side or on the client side. Let us now examine each of these cases in turn. Server-Side Dynamic Web Page Generation To see why server-side content generation is needed, consider the use of forms, as described earlier. When a user fills in a form and clicks on the submit button, a message is sent to the server indicating that it contains the contents of a form, along with the fields the user filled in. This message is not the name of a file to return. What is needed is that the message is given to a program or script to process. Usually, the processing involves using the user-supplied information to look up a record in a database on the servers disk and generate a custom HTML page to send back to the client. For example, in an e-commerce application, after the user clicks on PROCEED TO CHECKOUT, the browser returns the cookie containing the contents of the shopping cart, but some program or script on the server has to be invoked to process the cookie and generate an HTML page in response. The HTML page might display a form containing the list of items in the cart and the users last-known shipping address along with a request to verify the information and to specify the method of payment. The steps required to process the information from an HTML form are illustrated in Fig. 7-33. Figure 7-33. Steps in processing the information from an HTML form. The traditional way to handle forms and other interactive Web pages is a system called the CGI (Common Gateway Interface). It is a standardized interface to allow Web servers to talk to back-end programs and scri