Mozilla has a blog post today indicating that WebRunner, the XUL-based application which just released version 0.7 and was meant as a way to give web applications their own window/desktop presence, has become Prism. Prism looks like it will enable greater desktop functionality much like Adobe AIR. The Mozilla labs blog has the mission of Prism:
Mozilla Labs is launching a series of experiments to bridge the divide in the user experience between web applications and desktop apps and to explore new usability models as the line between traditional desktop and new web applications continues to blur.
This is a pretty huge deal and it shows a trend that I've been preaching/tracking all along; that the desktop isn't dead at all and that a hybrid approach is a successful way to go. Currently Prism looks and feels a lot like WebRunner. It's feature set, being able to display a web application in its own window and integrating them into things like the start menu, are some things WebRunner did. One of the new features that is very compelling is the possible integration with Firefox itself. The blog mentions an extension in development that would let you take any web application, click a button, and turn it into a Prism app for your desktop.
Currently there is no support for an offline scenario or some of the other things that make an application a true desktop application (File system access, notifications) but the blog post mentions that as part of this initiative Mozilla is "working to increase the capabilities of those apps by adding functionality to the Web itself, such as providing support for offline data storage and access to 3D graphics hardware."
In the past Mozilla seems to have struggled with the "desktop" issue with Mitchell Baker outlining some issues of the future of XULRunner (section 4 provides the most applicable info). Taken in that context this approach makes a lot of sense. This is very much a browser-driven approach to desktop applications that you would expect from someone who builds a browser. AIR is more of a web-centric desktop approach I think so the two solutions come at the problem from very different and in some ways complimentary ways.
I'm stoked about Prism and can't wait to see what Mozilla does with it. More excitement and interest in the desktop is going to end up helping us get to that perfect browser-desktop blend more quickly. Mark Finkle, a guy I have tremendous respect for, is the project lead so I have high hopes for Prism.