When Microsoft first introduced Silverlight a few years ago, it was with the stated promise of becoming a truly cross-platform development system for graphic interactivity and video. The full extent of that promise is still being delivered, in ways that many at the time hadn't really anticipated. The latest such crossover was previewed yesterday: a release candidate for an open source development toolset for the Eclipse development environment -- which itself is available in free and commercial versions -- that enables programmers to build applications that use Silverlight front-ends without having to rely on Visual Studio or Expression Studio.

Up to now, Silverlight has been considered a UI toolset that's made to be developed using Visual Studio. Now, Eclipse4SL from Soyatec -- a company that has received funding from Microsoft for this project -- gives developers tools for creating and deploying Silverlight panels, including the accompanying C# functionality and XAML interface code, that are very similar to their counterparts in Microsoft's commercial Visual Studio versions. All this in an environment that's better known as the IDE of choice among Java and JavaScript developers.

"Soyatec's Eclipse4SL is a plug-in that works with the Eclipse Integrated Development Environment (IDE) and Eclipse Rich Client Platform (RCP) to enable both Silverlight development and better interoperability between Silverlight and existing Java investments in Web sites and Web services," Microsoft Senior Vice President S. Somasegar posted last Friday to his blog. "Soyatec is releasing Eclipse4SL under the Eclipse Public License Version 1.0 on SourceForge, and has submitted it to the Eclipse Foundation as an open Eclipse project."

It's not exactly the same as making Silverlight answerable to Java -- though Eclipse developers will appreciate staying inside their home base, they'll still have to learn C#, at least to make Silverlight 2.0 apps (Silverlight 1.0 apps only rely upon JavaScript). And they'll need to learn to at least understand and interpret XAML, the XML-based language Microsoft created for laying out controls on panels and attaching code to their events.

But for those Eclipse developers who rely on Java Web services, they'll be delighted to learn that Eclipse4SL makes Silverlight apps play by the rules of REST. As long as existing Web services appropriately bind application and resource classes to URIs that correctly map to hosts, Eclipse4SL can enable Web applications that place calls in the standard format for "restlet" Web services, using Silverlight for their front end.

Eclipse4SL is fully documented online, and Soyatec's schedule for final release remains on schedule for later this spring.