Before RSS, several similar formats already existed for syndication, but none achieved widespread popularity or are still in common use today, and most were envisioned to work only with a single service. For example, in 1997 Microsoft created Channel Definition Format for the Active Channel feature of Internet Explorer 4.0. Another was created by Dave Winer of
UserLand Software. He had designed his own XML syndication format for use on his Scripting News weblog, which was also introduced in 1997
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RDF Site Summary, the first version of RSS, was created by Dan Libby of Netscape in March 1999 for use on the My Netscape portal. This version became known as RSS 0.9. In July 1999 Netscape produced a prototype, tentatively named RSS 0.91, RSS standing for Rich Site Summary, this was a compromise with their customers who argued the complexity introduced (as XML namespaces) was unnecessary. This they considered a interim measure, with Libby suggesting an RSS 1.0-like format through the so-called Futures Document
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Soon afterwards, Netscape lost interest in RSS, leaving the format without an owner, just as it was becoming widely used. A working group and mailing list, RSS-DEV, was set up by various users to continue its development. At the same time, Winer posted a modified version of the RSS 0.91 specification - it was already in use in their products. Since neither side had any official claim on the name or the format, arguments raged whenever either side claimed RSS as its own, creating what became known as the RSS fork.
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The RSS-DEV group went on to produce RSS 1.0 in December 2000. Like RSS 0.9 (but not 0.91) this was based on the RDF specifications, but was more modular, with many of the terms coming from standard metadata vocabularies such as Dublin Core. Nineteen days later, Winer released RSS 0.92, a minor and (mostly) compatible revision of RSS 0.91. The next two years saw various minor revisions of the Userland branch of RSS, and its adoption by major media organizations, including The New York Times.
Winer published RSS 2.0 in 2002, emphasizing "Really Simple Syndication" as the meaning of the three-letter abbreviation. RSS 2.0 remained largely compatible with RSS 0.92, and added the ability to add extension elements in their own namespaces. In 2003, Winer and Userland Software assigned ownership of the RSS 2.0 specification to his then workplace, Harvard's Berkman Center for the Internet & Society.