Mozilla's Prism entered public beta testing on Friday, a milestone marking the software's readiness for general use and the convergence of local computing with the cloud.Prism is a Firefox plug-in, and a stand-alone application, that allows users to generate desktop versions of Web applications.

With the plug-in, Firefox users can select the "Convert Website to Application" command from the Tools menu and immediately convert a Web app like Google Docs into a stand-alone application.

The result is a Google Docs icon can be used to launch the application from the quick launch bar or to launch the application automatically at start-up. Generated Web apps of this sort can also be associated Web link actions, thus allowing mailto: links to launch a Prism version of Gmail rather than, say, a traditional desktop app like Outlook.

While it might seem that Prism accomplishes nothing more than opening a new browser window and calling it an application, there's more to it than that. Under Windows (it also works on the Mac OS X and Linux), a stand-alone app created by Prism runs its own firefox.exe process in the Windows Task Manager, one that appears to be substantially more memory efficient than the full Firefox browser, at least upon launch.

One good reason to use Prism is to avoid crashes in Firefox. As the Prism site notes, "A single faulty app or Web page can no longer take down everything you are working on." True for Firefox, though not if each Web page/tab runs in separate processes, has happens in Google Chrome.

Although Prism generates apps that are functionally distinct from the Firefox browser, it doesn't change the way Web apps look or their interface. Developers that work with the Prism APIs have the option to customize their Web apps, but those attempting interface redesigns may also want to consider Adobe AIR, which provides similar HTML, JavaScript, CSS support to build local versions of Web apps.

Prism appears to be the Mozilla community's answer to AIR. Though Adobe AIR supports open Web standards, many in the open source community remain suspicious of Adobe because its Flash platform isn't open source, and because Adobe charges a lot of money for its professional graphics applications.

Prism still has a ways to go. It doesn't, for example, generate offline storage capabilities -- you still need Gears or similar technology for that. But future iterations of Prism, in conjunction with Web apps that use HTML 5 technology, should change that.

As a beta, it's worth trying out. And in subsequent iterations, it should be even more interesting.