What is it?
Before Ajax, Rich Internet applications (RIAs) meant Flash. The first use of the term may have been in a 2002 paper on Flash MX, by Macromedia's Jeremy Allaire.
The Flash platform has a number of advantages over Ajax, since it consists of a suite of purpose-built technologies designed to work together, and the Flash Player is almost ubiquitous - Macromedia's owner Adobe claims it is installed on over 98% of internet-connected computers.
There are some drawbacks too, however. The Flash platform includes some proprietary technologies, and there is a limit to what you can do without buying some Adobe products. But Adobe has been steadily open sourcing parts of the platform, and there are a number of open source initiatives to create Flash-compatible alternatives. Both Adobe and the wider community have also provided bridges between the Flash-based version of Ajax, Flex, and Ajax itself. Adobe is also making its AIR runtime for desktops available free.
Flex has grown from a way of adding simple interactive components to web applications, to a framework for RIAs which will run either in the browser using Flash or on the desktop using AIR. Adobe is now working to extend Flex to all browsers and operating systems, including mobile phones.
Where did it originate?
Macromedia released Flash in 1997.
What's it for?
Although Flex, Flash, AIR and other elements of the platform are downloadable free, you will probably need to buy the Eclipse-based Flex Builder to improve your productivity. Flex can be downloaded from the Open Source Flex SDK project.
What makes it special?
Adobe's Open Screen Project initiative aims to make Flash-based RIAs run on all devices, regardless of browser and operating system. Partners include Cisco, Intel, LG Electronics, Motorola, Nokia, NTT DOCOMO, Sony Ericsson, Toshiba, MTV and the BBC.
How difficult is it to master?
Adobe promises to teach you Flex in a week using the video lessons on its website.
Where is it used?
IT companies using Flex for online or packaged applications include SAP, HP and Google. IBM has a Flex plug-in for WebSphere Studio.
Rates of pay
Flex developers earn £30,000 to £35,000.
As well as Learn Flex in a Week, Tour de Flex is a desktop application which introduces the core Flex components, Adobe AIR and data integration, and a variety of third-party components. Adobe also offers the Flex Developer Centre for getting started with Flex and Ajax. IBM's slant on integrating Flex into Ajax applications can be viewed on its website.