Vivek Jhaveri explains how at the WinFS Team Blog:
As some of you may have discovered there is a set of applications on the WinFS CD. Some of these are officially “unsupported”, but are included because they demonstrate some of the capabilities of the WinFS platform.
I’m going to describe Microsoft Rave, which is one such application. A little background – I work on WinFS Synchronization, and last year was tasked with building an application that the WinFS team could use to “self host” the sync features. Self-hosting is what product development teams do by internally deploying our code so that we have a day-to-day feel for the product. The idea is to have the product team go through the experiences a customer is likely to encounter, and so help ship a better product.
Microsoft Rave is designed to make it easy to synchronize your data using WinFS. You can synchronize between multiple computers running WinFS, and also between different users, while granting access to only those you want to synchronize your data with. WinFS has the ability to synchronize any of your data (Contacts, Email, Documents, Photos etc) regardless of which application created it. Rave allows you to select your data using Windows Explorer, and set it up for synchronization. You can then invite your friends and colleagues who have also installed WinFS to synchronize your data. Thus, you can share out your photos, contacts, and documents easily and have changes to them automatically replicated to others.
When I consider what it would take to develop a peer-to-peer application like Rave in the absence of a powerful storage platform like WinFS, I think “several years” rather than the several months that it actually took. Hopefully this post helped describe why – no other general purpose store or file system provides the synchronization support, data change notifications, and security that WinFS does. Implementing a peer-to-peer data synchronization application like Rave in absence of these services would have been a daunting undertaking indeed.
WinFS as described at the 2003 PDC had a number of game changers and synchronization is one of them.