According to developer sources, Microsoft is cutting back Longhorn client's planned feature set so as to be able to make its current delivery targets: Beta 1 by next year and final release some time in 2006.

Check Out Our Updated Story on Longhorn Cuts Here

Microsoft is expected to announce officially later on Friday its future roadmap for the desktop version of Longhorn. And while developers and customers who expected they'd be required to rewrite their applications to take advantage of Longhorn may be happy with Microsoft's roadmap changes, others who were banking on promised Longhorn features, such as the next-gen Windows File System, will be far less so.

The end result? Longhorn is going to be a lot more of an evolutionary than a revolutionary Windows release.

"Longhorn is going to stop being a whole new thing and more of an XP with a lot of good new stuff," said one developer close to Microsoft, who requested anonymity.

Microsoft officials declined to comment on the pending announcement, other than to say it will happen on Friday and will involve Longhorn.

As outlined at the Microsoft Professional Developer Conference (PDC) in the fall of 2003, Longhorn was to be comprised of four key pillars: The Windows File System (WinFS); the Avalon presentation subsystem; the Indigo communications subsystem; and the "Fundamentals" pillar, consisting of application programming interfaces (APIs) designed to provide core power management, driver management, application installation/deployment, digital rights management and other basic tasks. These pillars were designed to plug into a new programming model designed to replace Win32, known as WinFX.

Microsoft distributed to PDC attendees a pre-alpha version of Longhorn that included rudimentary versions of most of these subsystems. A true alpha release had been expected this fall.

But Microsoft has decided its initial set of Longhorn features was too ambitious, sources said. Executives are chopping away at the planned feature set. The resulting Longhorn is expected to consist primarily of incremental, core improvements — better performance, power management and the like.

Since this spring, Microsoft has been trimming the technologies it hoped to include in each pillar. But officials have insisted that the cuts were fairly limited and would not result in many changes to the Longhorn code that it has been distributing to developers since 2003.

On Friday, however, Microsoft is expected to admit that in order to get Longhorn out the door, the Windows team needs to take more far-reaching measures, developer sources said.

For More Details on Exactly What Microsoft Is Gutting, Go to Page 2

("Microsoft Guts Longhorn" Page 2)

Microsoft is expected to announce that it will cut WinFS from Longhorn, sources said. WinFS was slated to ride atop the Windows' NT file system (NTFS). WinFS is designed to allow users to store and find their data in an easier, quicker way. Many had considered WinFS the crux of Microsoft's next major release of Windows.

"Microsoft now realizes WinFS needs to be available in full and simultaneously on both the (Windows) client and server," said another source, who requested anonymity.

It's not clear when or via which Windows release(s) Microsoft will deliver the WinFS functionality, developer sources said.

Microsoft also is expected to admit on Friday that it is "decoupling" its Avalon presentation system from Longhorn so that it can run on one or more existing versions of Windows.

Since last fall, Microsoft has said it was decoupling its Indigo communications subsystem from Longhorn by making it available on older versions of Windows, as well as on Longhorn. Despite Microsoft officials' statements to the contrary earlier this year, Microsoft is now set to undertake a similar strategy with Avalon, sources said.

"Basically it looks like most of Avalon is going to get the ax. And most of WinFS is going to get axed," said a developer who asked not to be named.

At press time, it was unclear whether some or all of the Avalon and Indigo subsystems are still likely to be included in Longhorn when it ships in 2006. But as a result of Microsoft's decision make these technologies available on older versions of Windows, developers won't be required to upgrade to Longhorn in order to take advantage of them, sources said.

Microsoft isn't expected to make the decoupled versions of Avalon or Indigo available before 2006, however, developers noted.

Avalon is meant to replace the USER/GDI graphics application programming interfaces (APIs) that are part of the current Win32 programming model. And Indigo, the communications subsystem of Longhorn, is a communications technology catch-all for Web services plumbing (COM+, MSMQ, and ASP.NET Web services), as well as instant-messaging, voice-messaging, video messaging, collaboration and content distribution technologies.

Microsoft's decision to make its Longhorn technologies available to users of older versions of its software is not unprecedented. Microsoft's Office team opted for a similar strategy, by designing the next major release of Office (Office 12, due out as part of the "Longhorn Wave" of technologies) able to run on older versions of Windows, in addition to Longhorn. Originally, Office 12 was set to be a Longhorn-specific release.