FeedSync for Atom and RSS, previously Simple Sharing Extensions, are extensions to RSS and Atom feed formats designed to enable the bi-directional synchronization of information by using a variety of data sources.
The scope of FeedSync for Atom and RSS is to define the minimum extensions necessary to enable loosely cooperating applications to use Atom and RSS feeds as the basis for item sharing – that is, the bi-directional, asynchronous synchronization of new and changed items amongst two or more cross-subscribed feeds.
There are several examples of "real world" use of FeedSync feeds to synchronize data between applications.
FeedSync feeds were used extensively at the Strong Angel III exercise in August 2006 as a lightweight middle-ware to link applications from Microsoft, Google, ESRI and others on desktops and mobile devices.
Mesh4x, an open-source set of libraries, tools, applications and services for mesh-based applications, uses FeedSync as the versioning standard, and implements a Feedsync-inspired packet-based protocol to synchronize data over SMS text messages.