RSS

RSS (Rich Site Summary, RDF Site Summary, Really Simple Syndication) is a popular XML-based format (or, rather, group of formats) for providing feeds of content such as news articles, blog posts, podcasts, or, really, anything that can be distributed on the web which has updates for which an audience wishes notification. Unfortunately, there is a bewildering array of not-quite-compatible versions of RSS, and a good deal of squabbling over which version is the "real" one and who should be considered the "official" entity in charge of its development and standardization.

History
RSS was originated at Netscape in the late 1990s for use on its "portal" page, my.netscape.com. (This was in the era when just about every website was trying to be a "portal", with everything under the sun from weather reports to stock quotes embedded right into the front page, and user-customizable.) The idea was that sites could make their headlines and article descriptions, with links to the full article in the original site, available in a standardized format so they could be included on the portal page. The format was initially adapted as a variety of RDF, which in turn was XML-based. With Netscape promoting it, a number of sites began using it, and some tools for dealing with RSS feeds were produced by independent developers.

However, in 2001, Netscape pulled the rug out from under the RSS world by abruptly dumping all support for the format. By then they had been acquired by AOL (gag, vomit, retch), and whatever the heck the business model was for Netscape under this management, it apparently didn't include providing a standardized format for outside sites to put their content in a Netscape portal.

But by then there was enough third-party use of RSS that it kept on going even without corporate support. However, there was no clear line of succession to any "official" developer, since Netscape was pretending RSS never existed, and not making any sort of arrangements to hand it off to somebody else who actually cared about it. Two different groups stepped into the void by developing their own RSS standards, independently of one another and of Netscape. One was led by Dave Winer (who had created some RSS tools previously for UserLand Software), and the other, the RSS-DEV Working Group, was a non-profit coalition involving a number of individuals (including the late Aaron Swartz). Each of these groups has released a series of versions of the RDF standard, making two major "forks" (usually regarded as "1.x" for the RSS-DEV version and "2.x" for the Dave Winer version due to the version numbering used). The original Netscape versions were numbered in the 0.9 sequence, and a few more 0.9 versions were released as part of what eventually became the "2.x" fork, just to confuse things even more.

Yet another version, the proposed RSS 1.1 spec, is a draft not actually produced or endorsed by any of the organizations involved in the tangled history of RSS.

These versions differ in all sorts of details: whether or not they support RDF features, whether HTML tags are legal within various elements, and if so, should they be rendered as HTML or displayed as raw code, what set of character entities are supported, and so on. However, there are extension mechanisms by which developers are able to "port" their favorite features from one version into RSS code for another. RSS implementations end up supporting some sub- or superset of the various features without necessarily having any standards-based coherence. It's a mess.

To get away from the mess, some have championed an alternative feed format called Atom.

Standards

 * RSS 0.90 Specification
 * RSS 0.91 Specification
 * RSS 1.0 Specifications
 * RSS 2.0 Specification

Other links

 * Wikipedia article
 * History of the RSS Fork (Mark Pilgrim)
 * The myth of RSS compatibility