Microsoft has revealed ambitious plans for the next version of its Silverlight browser plug-in technology for rich Internet applications, including faster startup times and software development improvements as well as more capabilities for running applications outside of a browser.

Dubbed Silverlight 4, a beta release of the upgrade was made available for download on Wednesday. A final release is due in the first half of next year. Silverlight 4 was discussed at the Microsoft Professional Developers Conference (PDC) in Los Angeles.

Silverlight 4 features a 30-percent faster startup time and new profiling support, said Scott Guthrie, corporate vice president of the Microsoft .Net Developer Platform. Version 4 will support the same OSes and browsers as in previous releases as well as the Google Chrome browser.

"We're improving startup by more than 30 percent for common scenarios, sometimes up to 80 percent," Gutrhie said.

HTML hosting capabilities are included in Silverlight 4. "You can actually now host HTML as a control within your applications," Guthire said. The upgrade also features other new controls and extends controls based on user requests.

With Silverlight 4 and .Net Framework, an assembly can be compiled once and run on both technologies.

Out-of-browser improvements for Silverlight 4 include Windows APIs and notification popup support. Trusted applications can be run outside the Silverlight 4 sandbox on Windows and Mac systems, with a user consent dialog featured.

Other capabilities in Silverlight 4 include data-binding improvements, UDP (User Datagram Protocol) and multicast support. REST enhancements are featured along with improvements pertaining to Windows Communication Foundation and rich Internet applications.