rss (file format)

RSS is a family of XML file formats for web syndication used by news websites and weblogs. It stands for one of the following standards:

Rich Site Summary (RSS 0.9x)
RDF Site Summary (RSS 0.9 and 1.0)
Really Simple Syndication (RSS 2.x)

Usage

RSS is used to provide items containing short descriptions of web content together with a link to the full version of the content. This information is delivered as an XML file called RSS feed, RSS stream, or RSS channel. An orange rectangle with the letters XML is often used as a link to a site's RSS feed. In 2004 and 2005, use of RSS spread to many major news organizations, including Reuters and the Associated Press, after several years of use by weblogs, technology publications and other early adopters. The first online news site to use RSS feeds was Variety.com in June of 2002. Under various usage agreements, providers allow other websites to incorporate their "syndicated" headline or headline-and-short-summary feeds. RSS is widely used by the weblog community to share the latest entries' headlines or their full text, and even attached multimedia files. (See podcasting, broadcatching and MP3 blogs.) A program known as a feed reader or aggregator can check RSS-enabled webpages on behalf of a user and display any updated articles that it finds. RSS saves users from having to repeatedly visit favorite websites to check for new content or be notified of updates via email. It is now very common to find RSS feeds on most major web sites, as well as many smaller ones. Feed Readers or News aggregators are typically constructed as extensions to a web browser, as extensions to an email program, or as standalone programs. Some programs now also have native support of RSS and/or Atom, such as Mozilla Firefox (via "live bookmarks"), Mozilla Thunderbird (via "RSS accounts"), Opera (via an "RSS browser"), and Avant Browser (via "XML feeds"). RSS support will be available in the next version of Safari. Web-based feed readers and aggregators such as the ones found on My Yahoo, Yahoo!'s user-customizable Web page, on Retronimo or on Bloglines, require no software installation and make the user's "feeds" available on any computer with Web access. Some aggregators syndicate (combine) RSS feeds into new feeds, e.g. take all football related items from several sports feeds and provide a new football feed. See news aggregator for a list of clients for various operating systems.

History

The original version of RSS was 0.9, designed by Netscape for use on their "My Netscape" portal. It was originally based on RDF. But according to the RSS timeline, Netscape's marketing people caused it to be stripped down http://goatee.net/2003/rss-history.html. This stripped-down version was renamed Rich Site Summary. Netscape later expanded the format, to add features present in the Scripting News XML format, which was designed by Dave Winer of UserLand Software. In 2000 RSS "was forked" (split into two development paths):

A group of developers organized in the rss-dev list http://groups.yahoo.com/group/rss-dev/ published RSS 1.0 http://purl.org/rss/1.0/ based on RSS 0.9 utilizing the W3C standards RDF and XML namespaces. RSS 1.0 was designed to provide a frozen standard that allows for extension through modules, residing in their own name spaces http://purl.org/rss/1.0/modules/. By leveraging RDF, RSS 1.0 streams can take part in the Semantic Web.
Dave Winer published RSS 0.92 , which extended RSS 0.91 with new elements, for those who felt namespaces and RDF added unnecessary complexity. Winer promoted the format to organizations including The New York Times, and emphasized "Really Simple Syndication" as the meaning of the three-letter abbreviation. The latest version (Fall 2002) is RSS 2.0.1, which, like the 1.0 format, is considered frozen, and allows for extensibility through modules living in their own namespaces. Details are given in its specification, published under a Creative Commons copyright at Harvard's Berkman Center for the Internet & Society. Winer and Userland Software assigned ownership of the specification to Berkman Center in 2003 and named an advisory board, from which Winer subsequently resigned.

Incompatibilities

RSS refers to multiple syndication formats (with multiple versions), which some observers say are incompatible http://diveintomark.org/archives/2004/02/04/incompatible-rss. Others disagree, arguing that the underlying structure of RSS is that of XML and therefore compatibility is achievable through XSLT, which the RSS aggregator would apply anyway in order to make the RSS feed presentable to users. Developers of aggregators and publishers have hedged their bets by supporting multiple XML syndication standards. Additional incompatibilities arose when publishers started to put small fragments of HTML content in an item's description. Some are added as a CDATA sections, while some are added as HTML-encoded PCDATA. The date format used by various versions of RSS is also different. Also many feed authors started mixing features of the different standards, or added new features supported only by certain feed readers or aggregators, thus producing RSS feeds that do not meet any of the standards and sometimes are not even well-formed XML. Because of these confusions and incompatibilities, the Atom standard was created. (Some have argued that the creation of yet another format only confuses things further.)