MSDN has posted an article on the WinFS file storage system
One of the monumental problems organizations face today is aggregating information that's stored in disparate formats. Knowledge workers have long wanted to be able to search for content independent of format. The next version of the Windows operating system, code-named "Longhorn," boasts a new storage subsystem that makes that task easier. That subsystem, code-named "WinFS," allows the user to perform searches based on the metadata of the stored item, regardless of what type of file it is or which application created it. This article covers the basic architecture of WinFS and explains how to use the WinFS managed API.Read more
