Members of Microsoft's Developer Network got a sneak peek at Microsoft's Avalon windowing elements technology last week. Avalon, which will make the user interface much more than just a browser window, is slated to appear in Microsoft's Longhorn Windows release due out in 2006. Network members paid a fee for the Friday briefing.

Avalon will be used by developers to build a new generation of Web and intranet applications that Microsoft says will be more user friendly than today's page-by-static-page versions. "A lot of Web applications have run out of juice," says John Montgomery, director of product management in Microsoft's Developer Division. Competitive companies are looking for more ways to improve their customers' experience at their Web sites than the browser window currently allows.

"They're looking at ways to use smarter clients," Montgomery says, comparing today's browser window to the mainframe's "dumb" terminal. Unlike dumb terminals, at least browser windows can display graphics, but like its dim-witted cousin, the browser window can only show what a server tells it to. A smart client, also referred to as a "rich" client for the depth of the user interface, can take what a server sends it and work with it locally, using resources already resident on the PC.

To make the Windows PC and laptop smarter, however, is going to take a lot of work.

When it arrives in mid-2006 with Longhorn, Avalon will include a smarter rendering engine. The rendering engine knows how to paint the screen in response to an application, and Avalon's will know whether the PC or laptop on which it's running has the extra memory needed to help run video, as many of today's PCs do. This will make it easier for developers to include a splice of video in an application, Montgomery says.

Avalon will include XAML, an XML-based markup language that "will be for the smart-client applications what HTML is to Web applications," Montgomery says. XAML will define the display of a smart-client application, but unlike HTML, it may be combined with any Microsoft .Net programming language.

As a markup language, HTML has few provisions for interaction with the user. The most common is a "form," calling for specific types of data from the user such as name and E-mail address, which is captured and sent to an Internet server. Limited forms of activity can be supplied by embedding JavaScript or dynamic HTML in the page, but animated objects and more ambitious movement-oriented displays typically rely on the Flash Player, an add-on to the Windows browser from Macromedia Inc. Avalon will make it easier for C# or Visual Basic .Net programmers to add actions to their Web pages that interact with users. Rich clients typically let a user click on a subject of interest, then add to the options available displayed at that subject. They literally expand that part of the window and populate it with information and options.

Such rich clients are already available through Java-based suppliers such as Nexaweb Technologies Inc. Others use the nearly ubiquitous Flash Player to build rich clients. Macromedia launched a Flex set of tools and components in March. Laszlo Systems Inc., another rich-client supplier, stages rich-client features inside the Flash Player by combining XML page layout with small Actionscript programs, its proprietary scripting language.

What Microsoft showed developers Friday was how they'd be able to make use of similar elements in Web applications by using Avalon. It will come with a set of user-interface elements, such as resizing windows, buttons, menus, and dialogue boxes that can be activated in response to an application, issuing directions from an Internet server.

Avalon will provide a smart client that knows what other Windows resources are available on a given machine, Montgomery says. If Microsoft Office is available, for example, it will make use of the spell checker in Word rather than referring a user to a spell checker Web site.

Avalon will also be smarter about what the user wants to do, he said. If a user is filling out a form and goes from one page to the next, the first page is typically lost if the user hits the back button to go back to where he started. Avalon will track issues of session and state, meaning it will know how to reconstruct a previous session with the server and re-create the first page of that form, Montgomery says.

Says Montgomery, "We'll have a very different looking Web in five years."