Microsoft making RSS a two-way street

Microsoft is creating extensions for the RSS syndication format to make it multidirectional.

Microsoft is extending the popular RSS 2.0 Web syndication format to make it "multidirectional," allowing it to be used for synchronizing information such as contacts and calendar entries across different applications, the company said.

RSS 2.0 is best known as a way to let Internet users subscribe to content from Web sites that support RSS (Really Simple Syndication) feeds. When content on a site is updated, the RSS feed informs the subscriber, often with a summary of the updated content and a link to it.

Microsoft is developing a set of extensions to RSS so that it can be used for exchanging and synchronizing content that is updated by two or more parties. Its goal is to take what is essentially a one-way publishing mechanism and make it multidirectional.

The company published version 0.9 of the specification, called Simple Sharing Extensions (SSE) for RSS 2.0, on its Web site earlier this month and is seeking feedback for a final version.

To understand what the extensions hope to achieve, imagine two PC users who wish to share and coedit a list of items using an RSS feed. Both people publish their lists using RSS with the sharing extensions, and both also subscribe to the other's feed.

Whenever either of the two updates their list, the changes are added to their feed and incorporated into the list of the other subscriber.

The extensions "enable feed readers and publishers to generate and process incoming item changes in a manner that enables consistency to be achieved," Microsoft said. "In order to accomplish this, SSE introduces concepts such as per-item change history (to manage item versions and update conflicts) and tombstones (to propagate deletions, and un-deletions)."

The specification could be used to keep contact lists synchronized across a user's various devices, such as a PC, PDA (personal digital assistant) and mobile phone. Or it could be used by family members (or co-workers) to synchronize entries they wish to share from their personal calendars, explained Ray Ozzie, Microsoft's recently hired chief technical officer, in a posting on his blog.

Ozzie's involvement in SSE is no surprise -- he created Lotus Notes, which lets workers update and synchronize calendars, documents and other files with each other. Notes was part of the inspiration for SSE, Ozzie said.

After joining Microsoft he met with some of its product teams, including Exchange and Outlook, and thought about ways of synchronizing information among Microsoft products, as well as with those of other companies, he wrote. Soon after, SSE was born.

"In just a few weeks time, several Microsoft product groups ... built prototypes and demos, and found that it works and interoperates quite nicely," Ozzie wrote. It's too early to say which Microsoft products will use SSE, and code won't be released until version 1.0 is ready at a future, unspecified date, he said.

Microsoft has a checkered past when it comes to "extending" technologies it does not own, raising inevitable questions about its intentions with RSS 2.0. Sun Microsystems, for example, sued Microsoft for extending Sun's Java technology in a way that prevented some Java applications from running properly on Microsoft's software.

"Microsoft is notorious for developing what it calls 'standards' that are actually 'Microsoft standards,'" said Chris Harris-Jones, a principal analyst with U.K. research company Ovum.

Still, Microsoft said its aim is to define "the minimum extensions (to RSS) necessary" to achieve its goal. It released the specification under the Creative Commons license, which is also the license used for RSS 2.0, and it said it is not aware that it owns any patents related to SSE. If it finds any, it said, it will offer a royalty-free patent license on "reasonable and non-discriminatory terms."

Ovum's Harris also wondered why Microsoft picked RSS 2.0 rather than a similar syndication format, Atom. RSS is far more widely used, but Harvard University, which currently owns RSS 2.0, has said it does not plan to update that specification any further, according to Harris. "RSS 2.0 is frozen; it's not going anywhere," he said.

Atom, on the other hand, was submitted this year to the Internet Engineering Task Force for standardization, Harris said. "It would be nice if Microsoft would support Atom, and then submit SSE for standardization alongside it, so it all becomes part of an internationally recognized standard," he said.

"Otherwise -- and I'm being very cynical here -- you might end up with Microsoft's RSS, which only Microsoft uses, and Atom, which everyone else uses. So you end up with two standards, one for Microsoft and one for everyone else. But then maybe that's too cynical, even for an analyst," he said.

Microsoft said it picked RSS in part because it is a very simple technology. The SSE extensions could be used with Atom "in principle," the company said, although the version developed does not support it.

The SSE specification can be used with the OPML (Outline Processor Markup Language) format, used for creating hierarchical lists such as categorized music playlists, Microsoft said.

A FAQ about SSE, including an explanation of how it works, is here:

The SSE efforts are distinct from Microsoft's other RSS work, it said, such as the planned support for RSS within Vista, and Simple List Extensions to RSS, which can be used to let Web sites publish lists, such as photo albums or music playlists.

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