Here are more clues about Microsoft's XML emphasis from an insider.
Bosworth on the Browser (Thursday, February 19, 2004 7:26 PM/EST)
Bea's Chief Architect (and former Microsoft XML maven) Adam Bosworth shares some interesting insights on where Microsoft's going with its XAML markup language — and with the whole concept of a "browser" in Longhorn. Bosworth should know. He used to be head of Microsoft's Webdata unit, which is focused on Microsoft's long-term XML strategy.
The interview is entitled "The World Needs Simpler Java," and is worth reading:
I built IE [Internet Explorer] 4 and built the DHTML and built the team that built it. And when we were doing this we didn't fully understand [that] people use the browser as much because it was easy to use as almost anything else.
Now, Longhorn I think is conflicted about this....
....you can think of IE as a component within something. IE is very well designed to be a component. Look at AOL. AOL uses it as a component today. Some of the Outlook stuff uses it. InfoPath was actually built on top of IE as a component. So I think what you may see is people building stuff that uses IE as a component. So the rendering is still rendering. You use the browser as you do today, but the communication on the back end is richer. That's what I think is likely to happen, but it's hard to say. You'd have to ask whose going to do this. And the only way I see it happening is in the open source community.
Given those last remarks, strange is their omission of Mozilla XUL (demo gallery and a third-party comparison with Longhorn). XUL is open source and runs on Windows, Mac, and Linux sans Microcruft(tm) and Microlockin(tm). It all begs the question of why Microsoft wishes to reinvent Mozilla and call the result innovation.