Microsoft is sacrificing some features it planned for Longhorn as it works to deliver its first beta of the next Windows client next year, according to a company spokesperson.

Microsoft set out an ambitious vision for Longhorn last October at its Professional Developers Conference.

The company announced that the operating system would offer major improvements over Windows XP in the way it handles graphics, files, and communications. Microsoft has forecast a 2006 release.

"What we told developers at PDC is the essence of Longhorn," says Greg Sullivan, lead product manager for Windows.

"We are now determining the core work that we absolutely need to do and what the areas are where we can do some shaping around the edges so we do get the product in the hands of customers."

Microsoft is not cutting back on its vision, according to Sullivan. Instead, it is clipping features and functionality, without removing core improvements it promised, so the product can ship in a reasonable time frame.

Longhorn is a major new Windows release, a "big bet" for Microsoft, Chairman and Chief Software Architect Bill Gates said last year. Gates has described Longhorn as a "big breakthrough release" and the most significant release of Windows since Windows 95.

Sullivan declines to detail which parts of the Longhorn plans won't make it to the final product.

Microsoft has to trim the Longhorn feature set to be able to deliver the product, says Michael Cherry, a lead analyst at Directions on Microsoft.

"Microsoft has talked about a lot of features and functionality for Longhorn, and as it starts to talk about shipping the product it is quite natural that some features get postponed or cut," Cherry says.

"In fact, it is almost a good sign that they are starting to be realistic about the amount of work they can get done in a defined period of time."

Until today, Microsoft basically said it could do almost anything with Longhorn and presented it as a panacea for all Windows headaches, according to Cherry.

One part of Longhorn where Microsoft might trim its ambitions is WinFS, the new unified storage system that Gates referred to at PDC as a "holy grail." WinFS promises to make it easier for users to find data such as documents and email messages.

Microsoft may decide to limit the functionality of WinFS to users' computers and not extend it to file-sharing servers in a corporate network, according to sources familiar with Microsoft's development plans. Details on the changes to Longhorn were first reported earlier on Friday by BusinessWeek Online.

WinFS is one of three core components of Longhorn. The other two are Avalon and Indigo, code names for a presentation subsystem and communication technologies, respectively. The components sit on top of a layer of "fundamentals" that includes security and technology to make sure applications and drivers don't conflict.

All those components and the fundamentals will be in Longhorn when it ships, according to Sullivan.

Longhorn and its beta release have slipped since they were first discussed. Microsoft last year set 2005 as Longhorn's release year and planned a beta for 2004, but the company has backed away from that timeline.

Microsoft has a spotty record in meeting release targets. In March, the company delayed the release of two major updates, its SQL Server 2005 database and Visual Studio 2005 developer tools, until 2005. Both were due in the second half of 2004, and both products are tied to the new technologies coming in Longhorn.