Flex is Adobe's high-level programming environment for creating rich-client applications that run inside the Flash virtual machine. The Flex platform consists of five main components:

• A class library written in the ActionScript 3 language, which is an implementation of the EcmaScript standard, and is substantially identical to the next-generation JavaScript. ActionScript is an object-oriented, functional language, and among its unique features is support for optional static typing. The Flex API is built atop the API of the Flash virtual machine, and effectively extends Flash's API with collections, utility classes, visual effect classes, and classes that define Flex-based applications. Many UI-related classes are part of the API, too, such as validators, formatters, and data binding.
  
  
• A set of ActionScript components for creating rich graphical user interfaces. These include the standard fare of UI widgets, but also incorporate multimedia, such as easy access to the desktop's Web camera or microphone. Layouts and transition effects are included, too, as are a set of rich charting components.
  
  
• ActionScript code generators and XML schemas that make it possible to compose complex user interfaces with an XML grammar, and then have the framework automatically generate the equivalent ActionScript code. Flex's XML language, MXML, exposes component properties via XML, reducing the amount of boilerplate code developers have to write and maintain. Most Flex applications are a mix of MXML and ActionScript code.
  
  
• An ActionScript compiler that turns ActionScript into the bytecode format for the Flash Virtual Machine. The Flex compiler, in fact, performs a two-stage compilation: It first turns MXML code into ActionScript, and then compiles the ActionScript into Flash bytecode.
  
  
• A set of server-side data integration components that were previously called Flex Data Services, but were recently re-christianed to Adobe LiveCycle. The server-side part of this framework is written in Java, and can run in enterprise Java servers. The client-side part integrates with data-aware Flex components. Since Flex applications can communicate data with services in a variety of other ways, too, such as via HTTP, direct socket connections, or by invoking Web services, Adobe LiveCycle is an optional Flex component.

The Flex SDK, which Adobe made available for free in 2006, includes the first four of these components, with the exception of Flex Charting, for which the company charges a license fee. Adobe also made available last year a version of Flex Data Services that runs on a single CPU, for free.

Today, Adobe announced that it is taking the additional step of releasing the next version of the Flex SDK under the open-source Mozilla license. Artima spoke with James Ward, Adobe's Flex evangelist, and Eli Greenfield, who is principal scientist of the SDK.

When asked how Adobe envisions the community adding value to Flex, Ward noted that Flex already enjoys a healthy open-source ecosystem, with major Flex projects, such as FlexUnit, released under open-source licenses.

He also noted that with the next version of the Flex SDK, slated for final release at the end of 2007, Adobe will first make the sources available via a Subversion repository, and will, over time, migrate to a model to include committers outside of Adobe, too.

According to Ward, Adobe chose the Mozilla license because the company has already been working with Mozilla on Project Tamarin, the source code for the Flash virtual machine that also includes the next-generation JavaScript interpreter to be used in future versions of Firefox and Mozilla.

According to Ward, Adobe's business model with Flex includes building some of its own software with Flex, such as the recently released Adobe Media Player; charging a license fee for the enterprise-ready version of Flex Data Services; and selling FlexBuilder licenses to developers. FlexBuilder is an Eclipse-based IDE for visually designing, coding, and debugging Flex applications.

When asked if Adobe intends to position Flex as a direct competitor to the now open-sourced client side portions of Java SE, Ward said that that was not the case, and that his company viewed Flex and Java as complementary technologies.

How do you think the open-source Flex SDK will influence client-side Java? Do you think it will hurt, or improve, client-side Java over time?