LOS ANGELES — Microsoft showed off publicly for the first time here at its Professional Developers Conference on Tuesday the next-generation Windows File System (WinFS) technology that is at the heart of its Longhorn operating system that is expected to ship in 2006.

WinFS is the data subsystem component of Longhorn. It is built by a team that reports to Corporate VP Gordon Mangione, who is the head of Microsoft's SQL Server product line.

Mangione delivered the second PDC keynote on Tuesday morning. He noted that data is expanding exponentially. "We are tripling the size of our hard disks every 18 months. Heaven help us if "find first/find next" is the way we are going to find data on our systems," going forward.

The three "core tenets" of WinFS are find, relate and act. "Find" is all about the new WinFS schemas and natural-language query capabilities that Microsoft is building to make finding information easier. "Relate" refers to the WinFS software that makes explicit relationships between people, systems and data. And "Act" is about the information agents that Microsoft is building into WinFS. Mangione described these agents as "inbox rules on steroids."

"Information agents put you, as an end user, back into control of the information coming into your machine," Mangione said.

WinFS is built on top of Microsoft's 15-year-old Windows file system, called NTFS.

"There is no way we are going to throw all that (NTFS) out and start over again," Mangione said. "WinFS is bound very tightly with NTFS. We had to couple together our relational engine technology with NTFS. That allows us to create very rich metadata associated with streams."

Mangione talked up WinFS' consistent programming model and consistent transaction model. These are "all available in this rich, rich file system," he told PDC attendees.

Mangione described Yukon,Microsoft's version of SQL Server due out at the end of 2004, as a "big, big, big release for SQL Server." He said that about 2,000 people have been working with beta 1 of the product for about six months.

WinFS wasn't the only database-related feature that Mangione put through its paces for PDC attendees. Mangione and SQL Server director Tom Rizzo showed how Yukon exposes all of its subsystems — including elements such as stored procedures — as Web services. By doing this, Microsoft is working to make Yukon more interoperable with other data sources in heterogeneous environments, according to company officials.

Microsoft is making an interim beta build of Yukon available to PDC attendees and to existing beta testers. The interim build is a fairly minor update that includes new features designed to take better advantage of Microsoft's Whidbey Visual Studio tool suite.