Mozilla has released an early preview of their Prism project for Mac and Linux developers. Launching the Prism application opens up a new blank browser window, with a dialog to create a shortcut to the application. You enter in a URL and a name for the "application", and then select whether or not you want shortcuts created on your desktop, taskbar etc... Prism then sets up the application for you.

I noticed a bunch of things that were very different from Adobe AIR. First of all, currently you can only run one Prism application at a time - because it actually runs the Prism application, and then opens up the URL in that window. (For example, I setup two Prism "applications", one for GMail and one for Yahoo Mail, but I can only run one of them at a time. When you run one on the Mac, the Menu item says "Prism"). In contrast, you can run as many Adobe AIR applications at one time as you like - and they run as their own applications - the menu items are the application name, and they each have their own icon in the dock or taskbar.

Secondly, once you delete the shortcuts that Prism creates, there's no way to run the "applications". In contrast, Adobe AIR adds the applications to your Program Files (Win) or Applications (Mac) directory, so even if you delete shortcuts to those applications, you can still run the applications themselves.

Mozilla is thinking about adding in adding functionality that is currently available in Adobe AIR, such as: "allowing web applications to register to handle particular content types; drag-and-drop support for uploading files to web applications; support for running applications offline (local storage, offline/online event notifications, caching of application components, etc.)." Those would be welcome additions - especially the ability to work offline (which is already available in Adobe AIR). If the application is a true desktop application, people are going to expect desktop like functionality, and that means drag and drop support, application specific content types and offline functionality.

Its great to see Mozilla looking to move web applications to the desktop - this is something I've been pushing for for a long time - from around the time that I started the Mozilla Calendar Project. However, I think they need to do a few things to improve on this initial release. Number one, obviously, would be to allow as many Prism "applications" to launch at a single time. (Not sure if this is related to separating out the profiles for each, but it might be.) Secondly would be to install the "applications" into an Applications folder. If they're applications, they should be put in the same place as other applications. Then I would start to incorporate all the features that they talk about above - drag and drop support, offline storage, etc... At that point, I think they'd have something pretty compelling for developers to build on. For now, I think AIR is probably the best option for hybrid web / desktop applications.

(Via Ryan Stewart)