Datasheet

Figure 1-2
Gmail
Gmail, Google’s free e-mail service, has been raved about as a marvel of client-server interaction in the
age of Ajax. When you first log in to Gmail, a user interface engine is loaded into one of the few iframes
the application uses. All further requests back to the server occur through this user interface engine
through an XMLHttp object. The data being transferred back and forth is JavaScript code, which makes
for fast execution once downloaded by the browser. These requests serve as instructions to the user
interface engine as to what should be updated on the screen.
Additionally, the Gmail application uses several frames and iframes to manage and cache big user inter-
face changes. The extremely complicated use of frames enables Gmail to function properly with the Back
and Forward buttons, which is one of the advantages of using frames or iframes instead of or in conjunc-
tion with XMLHttp (discussed later in the book).
The biggest win for Gmail is its usability. The user interface, as shown in Figure 1-3, is simple and
uncluttered. Interaction with the user and communication with the server is all seamless. Once again,
Google used Ajax to improve on an already simple concept to provide an exceptional user experience.
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