One of the main - and somewhat unsung -- features of Microsoft's next version of Silverlight is its support for running applications outside the browser.
Microsoft officials slipped in a mention of Silverlight 3's planned out-of-the-browser support during keynotes and sessions at the Mix '09 conference on March 18. On March 18, Microsoft made the one and only planned beta of Silverlight 3 available for download today and said the final release is slated for later in 2009.
Officials said the out-of-browser support will allow Silverlight apps to run on Windows or Mac clients and provide users with online, offline or intermittently connected access to their Silverlight apps and content.
Many Mix attendees understndablly equated the planned Silverlight 3 out-of-browser support to Adobe's AIR -- the runtime that allows Flash and other rich Internet apps to run outside the browser. But Microsoft officials claimed there will be advantages that Silverlight 3 offers over AIR -- starting with the fact that developers and users won't need to download an additional runtime in order to get Silverlight out-of-the-browser support like they need to do with AIR.
"AIR is a separate download from Flash," said Brad Becker, a Microsoft Group Product Manager for User Experience and Tools. "And already Silverlight (for which Microsoft claims there have been 350 million installations worldwide to date) has many times more users than AIR."
AIR also is a lot bigger, byte-size-wise, than Silverlight, Becker said.
Some Mix attendees also wondered aloud (on Twitter) whether Silverlight's new out-of-browser support will end up killing off Windows Presentation Foundation -- the Windows interface technology from which Silverlight was spawned.
Becker said that won't be the case. Instead, Microsoft is hoping to provide developers and users a continuum, allowing them to run their Web apps how and where they want. Unlike WPF apps, which are fully integrated with the desktop and hardware, Silverlight apps run in a protected sandbox environment that isolates them from the base OS, he said.
I asked Becker about Microsoft's plans to support Silverlight 3 on Linux clients. He said if and when that support happens, it will most likely come from Novell, which created the Silverlight port to Linux, known as Moonlight.
I also asked him how and when Microsoft would support Silverlight out-of-browser on mobile devices. Becker said Microsoft had nothing to announce about that kind of support at this time.
What do you think: Is Silverlight 3's out-of-browser support going to be a killer feature for the next version of Microsoft's browser plug-in? I'm wondering when and if Microsoft might make its Office 14 Web applications Silverlight-based, myself. Any apps you can envision being well suited to take advantage of Silverlight's out-of-browser support?