Rich Internet Applications

RIAs bring fast, dynamic interaction to previously static Web pages.

Definition

Rich Internet applications (RIA) are Web-based applications that have some characteristics of graphical desktop applications. Built with powerful development tools, RIAs can run faster and be more engaging. They can offer users a better visual experience and more interactivity than traditional browser applications that use only HTML and HTTP.

Early Internet users mostly exchanged text-based electronic mail messages. Then along came HTML and the World Wide Web, and soon people were looking at graphically enhanced Web pages designed by specialists and served up on demand. All these applications mainly involved reading text on-screen and dealing with material that was preformatted and essentially static.

To do tasks like manipulate data and interact with sophisticated business logic, users relied on specialized software on their computers and networks. Then someone thought about providing applications through standard Web pages that people could access with their browsers.

That this was even possible was a tribute to the power of the Web, but the underlying technology was also a terrible limitation. The static, stateless nature of HTTP meant that interaction was one-sided and disconnected, relegated to an asynchronous style reminiscent of green-screen mainframe applications from the 1970s.

These days, we are doing much better.

Today, programmers can embed almost any functionality they want inside a Web-based graphical interface, making it look and act as if it were traditional, shrink-wrapped software.

With modern tools, developers can create complex application screens using a variety of mixed media such as multiple fonts, bit-map and vector graphic files, animations, online conferencing, audio and video. Those applications offer functionality that goes far beyond mere reading and browsing, and they can be served up over the Web. We call these rich Internet applications.

RIA Characteristics

A number of key features differentiate RIAs from traditional Web applications.

Direct interaction: In a traditional page-based Web application, interaction is limited to a small group of standard controls: checkboxes, radio buttons and form fields. This severely hampers the creation of usable and engaging applications. An RIA can use a wider range of controls that allow greater efficiency and enhance the user experience. In RIAs, for example, users can interact directly with page elements through editing or drag-and-drop tools. They can also do things like pan across a map or other image.

Partial-page updating: Standard HTML-based Web pages are loaded once. If you update something on a page, the change must be sent back to the server, which makes the changes and then resends the entire page. There's no other way to do it with HTTP and HTML. With traditional Web-based apps, network connectivity issues, processing limitations and other problems require users to wait while the entire page reloads. Even with broadband connections, wait times can be long and disruptive.

But RIAs incorporate additional technologies, such as real-time streaming, high-performance client-side virtual machines, and local caching mechanisms that reduce latency (wait times) and increase responsiveness. A number of commercial development tools (see below) permit this partial-page updating.

Better feedback: Because of their ability to change parts of pages without reloading, RIAs can provide the user with fast and accurate feedback, real-time confirmation of actions and choices, and informative and detailed error messages.

Consistency of look and feel: With RIA tools, the user interface and experience with different browsers and operating systems can be more carefully controlled and made consistent.

Offline use: When connectivity is unavailable, it might still be possible to use an RIA if the app is designed to retain its state locally on the client machine. (Developments in Web standards have also made it possible for some traditional Web applications to do that.)

Performance impact: Depending on the application and network characteristics, RIAs can often perform better than traditional apps. In particular, applications that avoid round trips to the server by processing locally on the client are likely to be noticeably faster. Offloading such processing to the client machines can also improve server performance. The downside is that small, embedded and mobile devices -- which are increasingly common -- may not have the resources necessary to use such apps.

Kay is a Computerworld contributing writer in Worcester, Mass. You can contact him at russkay@charter.net.

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