Ray Ozzie proposed his concept of Simple Sharing Extensions back in 2005, and then more or less went silent. Until now!

Another Live Labs technology preview release arrived this week. It's called FeedSync and it is the current incarnation of the concept Ozzie developed to allow data sharing over web protocols like RSS.

The initial specification is available as version 1.0 at the time of this writing. It extends both the Atom and RSS specifications to incorporate item sharing which Microsoft defines as "bi-directional, asynchronous synchronization of new and changed items amongst two or more cross-subscribed feeds".

(Hmmm, calendar sharing anyone?)

The samples in the specification deal with a fictional task list example. Here is the code (emphasis added) for the sample RSS feed.

<?xml version="1.0" encoding="utf-8"?>
<rss version="2.0" xmlns:sx="http://feedsync.org/2007/feedsync">
 <channel>
  <title>To Do List</title>
  <description>A list of items to do</description>
  <link> http://example.com/partial.xml </link>
  <sx:sharing since="2005-02-13T18:30:02Z"
    until="2005-05-23T18:30:02Z" >
   <sx:related link="http://example.com/all.xml" type="complete" />
   <sx:related link="http://example.com/B.xml" type="aggregated" 
    title="To Do List (Jacks Copy)" />
  </sx:sharing>
  <item>
   <title>Buy groceries</title>
   <description>Get milk, eggs, butter and bread</description>
   <sx:sync id="item_1_myapp_2005-05-21T11:43:33Z" updates="3">
    <sx:history sequence="3" when="2005-05-21T11:43:33Z" by="JEO2000"/>
    <sx:history sequence="2" when="2005-05-21T10:43:33Z" by="REO1750"/>
    <sx:history sequence="1" when="2005-05-21T09:43:33Z" by="REO1750"/>
   </sx:sync>
  </item>
 </channel>
</rss>

Notice the namespace reference sx=http://feedsync.org/2007/feedsync the "sx" prefix is the one designated in the spec.

FeedSync supports multi-master topologies which means it can be used to send and receive data to multiple clients. An example topology is shown below, (image from Microsoft's web site.), as you can see clients can be bi-directional or pull only.

The possibilities are many, I am already thinking about using this technology to allow calendar syncing between Google Calendar, and Outlook. Another thought that jumped to mind would be to allow sharing appointment data for a centralized calendar among a group of subscribers on a project I am working on.

Best of all, the technology has been released and licensed under a Creative Commons license which means the technology is likely to be extended.

The best place to start looking for developers is the FeedSync For Developers page.

Have fun! Share with me your observations and ideas!

Cheers,

Robert Porter