Rich Internet Applications (RIA) are a cross between browser-based Web applications and traditional desktop applications, transfering some of the processing to the client end.

RIA's typically:

• run in a web browser, not requiring installation.
• run locally in a secure environment called a sandbox
• can be "occasionally connected" wandering in and out of hot-spots or from office to office

The term "Rich Internet Application" was introduced in a Macromedia whitepaper in March 2002.

Comparison to Standard Web Apps

Traditional web applications centered all activity around a client-server architecture with a thin client. Under this system all processing is done on the server, and the client is only used to display static (in this case HTML) content. The biggest drawback with this system is that all interaction with the application must pass through the server which requires that data be sent to the server, the server to respond, and the page to be reloaded on the client with the response. By using a client side technology which can execute instructions on the client's computer, RIAs circumvent this slow loop. It should be noted that Internet standards have evolved slowly and continually over time to accomodate these techniques, so it is hard to draw a strict line between what constitutes an RIA and what does not. Usually what can be done in an RIA is limited by the the capababilites of the system used on the client.

Because RIAs take advantage of the client's CPU, they offer real-time user-interface options that are not possible with the standard HTML widgets available to browser-based Web applications. This richer functionality may include anything which is implementable in the sytem being used on the client side (see below), including "drag and drop," using a slider to change data, calculation that happens on the client (e.g., an insurance rate calculator) and do not need to be sent back to the server, etc.

Justifications

Although developing applications to run in a web browser is a much more limiting, difficult, and intricate a process than developing a regular desktop application, the efforts are often justified because:

• installation is not required -- updating and distributing the application is an instant process
• users can use the application from any computer with an internet connection
• as web usage increases, computer users are becoming less willing to go to the trouble of installing new software if a browser-based alternative is available

This last point is often true even if this alternative is slower or not as feature-rich. A good example of this is phenomenon webmail.

Methods

Javascript

The first major client side language and technology available with the ability to run code and installed on a majority of web clients was JavaScript. Although its uses were relatively limited at first, combined with layers and other developments in DHTML it has become possible to piece together an RIA system without the use of a unified client-side solution. Ajax is a new term coined to refer to this combination of techniques and has recently been used most prominently by Google for projects such as Gmail and Google Maps. However, creating a large application in this framework is very difficult, as many different technologies must interact to make it work, and browser compatibility requires a lot of effort.

Macromedia Flash Player

Macromedia is one vendor in this area, whose Macromedia Flash technology includes Flash Communications Server , Central , Breeze and Flex, all of which are run in viewers' browsers within the Macromedia Flash Player which has a 98% penetration with current internet users.

Laszlo is an open source platform for rich Internet applications, originally developed by Laszlo Systems which also produce SWF files to be played at runtime in the Macromedia Flash Player.

Future Techniques

Microsoft's next user interface description Language (called XAML) is supposed to combine more seamlessly client-side scripting, and SVG—a W3C standard—which will allow richer GUIs. The Mozilla Foundation supports a standard with broadly similar goals called XUL.

See Also

• Thick vs Thin clients

External links

• IDC report on RIAs (requires registration)

Original March 2002 requirements for Rich Internet Applications: ( 500K PDF or HTML abstract )