Microsoft has given a sneak peek at Longhorn's file navigation and search capabilities.

Group vice president for platforms Jim Allchin said the embedded search technology is aimed squarely at products such as X1's search technology - and others. "This goes beyond search. What we're trying to do is provide visualisation," he said.

Longhorn, due late 2006, will add keywords to files, to create "virtual folders", document "stacking" and a List Pane. Like desktop search tools, Longhorn's search function will include a preview window where users can view and cut-and-paste content without opening the file, Allchin said.

The Windows Explorer folder approach remains in place, but the folders are now run vertically and appear to be open like a book with its pages partially exposed. Inside, instead of seeing generic icons for files such as a Word document, Longhorn presents snapshots of the first page in each document. Double-click on the folder and you can see thumbnails for each file that can be magnified by enlarging the window. Using this method, users can navigate to documents based on what they look like.

Users can also create their own virtual folders with a point-and-click interface. In Windows XP, the "My Documents" folder includes only the files physically located in that folder but in Longhorn "My Documents" can collect all documents on the computer into a single virtual folder view, regardless of location.

Microsoft has also added a concept it calls "stacking", which presents documents grouped by keyword. Instead of folders, documents appear in a stack that can be opened and navigated by double clicking on it. The List Pane feature allows a user to assemble groups of files by dragging them into the list. Lists can be saved and viewed along with other documents.

Allchin said application programming interfaces will allow software developers to take full advantage of these features, which leverage keywords and other user editable metadata.

"Tagging is a big thing now for everybody. What we've been doing is building a system natively in the OS for that," he said. While users can add keywords and other metadata through a properties dialog, Allchin said third-party vendors could develop tools to do that for the user. "It would be easy to add filters so that smart programs could look over the documents, look at the interesting things about it and populate the keyword field automatically," he said.

Meanwhile, the long-delayed object-based file system WinFS - originally slated to debut in Longhorn - will be in beta by the time Longhorn ships and will add more-powerful query capabilities, Allchin said.

WinFS will allow more-complex queries, Allchin said. "If you wanted to form a relationship between a contract, a case and an appointment, and you want a program to do those links and to do a query on that, we can't do that here. We need WinFS. But we can do a lot here," he said.

Longhorn is on track for shipment by "holiday 2006", according to Allchin, with the first beta due by this summer. The shipping schedule for WinFS is less certain, and Allchin emphasized that the file system will be available to independent software vendors for use in their products before it appears in Windows itself. WinFS would then appear in a future release of Windows.

After Longhorn, users can expect to see major releases of Windows every three to four years, with minor releases in the intervening years, Allchin said.