Today's post on the Building Windows 8 blog concerns what Steven Sinofsky calls the "Metro style user interface" that Microsoft previously showed off--the new Start Screen--and how that, combined with the classic Windows desktop, provides both "a reimagined Windows" as well as a "no compromises" version of Windows that does it all.

Right up front, Sinofsky mentions that there are "two different elements of the Windows 8 design": The previously shown Metro style UI and the more familiar (i.e. legacy) Windows desktop. One of the criticisms critics offered at the Start Screen unveiling was that switching between these two UIs was "jarring."

"This is a balancing act," he admits. "Having both of [sic] user interfaces together harmoniously is an important part of Windows 8."

Sinofsky notes that the goal from the beginning--i.e. summer 2009, two years ago--was that Microsoft would "reimagine Windows" with this release. That includes rethinking "even the most basic elements of the user model, the platform and APIs, and the architectures we support.  Our goal was a no compromise design."

According to Sinofsky, Metro is much more than just a shell on top of Windows, or a "thing on a thing," as Windows was once described with regards to MS-DOS. "As we show you more [of the new UI] in the coming months you will see just how deeply we have reimagined Windows," Sinofsky writes. "Metro style is much more than the visual design as we shall see ... it involves tools, APIs, languages, UI conventions, and even some of the most basic assumptions about a PC."

Of course, having two separate UIs, and thus two separate environments, is, by design, a compromise. And while I appreciate Microsoft's need to support backwards compatibility, switching between simple and beautiful Metro style UIs and more functional but older-looking classic Windows desktops apps is going to be, by nature, somewhat jarring.

Here's how that's explained.

"The role of the Windows desktop is clear," Mr. Sinofsky notes."The things that people do today on PCs don’t suddenly go away just because there are new Metro style apps. The mechanisms that people rely on today (mice, physical keyboards, trackpads) don't suddenly become less useful or 'bad' just because touch is also provided as a first-class option. These tools are quite often the most ergonomic, fast, and powerful ways of getting many things done. You can't just flip a bit overnight and turn all of that history into something new."

So to Microsoft, "no compromise" means that it cannot simply start over with a clean slate, and redesign all of Windows as a Metro environment because that would harm backwards compatibility. "No compromise" means the old and the new, working together.

In Windows 8, "you [will] get a beautiful, fast and fluid, Metro style interface and a huge variety of new apps to use," Sinofsky explains. "These applications have new attributes (a platform) that go well beyond the graphical styling (much to come on this at Build). If you want to stay permanently immersed in that Metro world, you will never see the desktop—we won’t even load it (literally the code will not be loaded) unless you explicitly choose to go there!  This is Windows reimagined."

[That last bit of emphasis was mine.]

"But if you do see value in the desktop experience," he continues, "those capabilities are right at your fingertips as well. You don't need to change to a different device. If you do want or need this functionality, then you can switch to it with ease and fluidity because Windows is right there. Essentially, you can think of the Windows desktop as just another app."

"You don't have to compromise!"