RSS feed

RSS is a family of web feed formats, specified in XML and used for Web syndication. RSS is used by (among other things) news websites, weblogs and podcasting. The abbreviation is variously used to refer to the following standards:


 * Rich Site Summary (RSS 0.91)
 * RDF Site Summary (RSS 0.9 and 1.0)
 * Really Simple Syndication (RSS 2.0)

Web feeds provide web content or summaries of web content together with links to the full versions of the content, and other metadata. RSS in particular, delivers this information as an XML file called an RSS feed, webfeed, RSS stream, or RSS channel. In addition to facilitating syndication, web feeds allow a website's frequent readers to track updates on the site using an aggregator.

Usage
Web feeds are widely used by the weblog community to share the latest entries' headlines or their full text, and even attached multimedia files. (See podcasting, vodcasting, broadcasting, screencasting, Vloging, and MP3 blogs.) Since mid-2000, use of RSS has spread to many of the major news organizations, including Reuters, CNN, PR Newswire, and the BBC. These providers allow other websites to incorporate their "syndicated" headline or headline-and-short-summary feeds under various usage agreements. RSS is now used for many purposes, including marketing, bug-reports, or any other activity involving periodic updates or publications. Many corporations are turning to RSS for delivery of their news, replacing email and fax distribution.

As the mainstream media attempts to realize the full potential of RSS, the new media is utilizing RSS by bypassing traditional news sources. Consumers and journalists are now able to have news constantly fed to them instead of searching for it.

A program known as a feed reader or aggregator can check a list of feeds on behalf of a user and display any updated articles that it finds. It is common to find web feeds on major websites and many smaller ones. Some websites let people choose between RSS or Atom formatted web feeds; others offer only RSS or only Atom.

RSS-aware programs are available for various operating systems (see list of news aggregators). Client-side readers and aggregators are typically constructed as standalone programs or extensions to existing programs such as web browsers. Browsers are moving toward integrated feed reader functions, such as Opera browser and Mozilla Firefox.

Web-based feed readers and news aggregators require no software installation and make the user's "feeds" available on any computer with Web access. Some aggregators combine existing web feeds into new feeds, e.g., taking all football related items from several sports feeds and providing a new football feed. There are also search engines for content published via web feeds like Feedster or Blogdigger.

On Web pages, web feeds (RSS or Atom) are typically linked with the word "Subscribe" or an orange rectangle,, or with the letters or  (although this indicates specifically an RSS feed.)

History
Before RSS several similar formats already existed for syndication, but none achieved widespread popularity or are still in common use today, as 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, which became mildly popular. Dave Winer also designed his own XML syndication format for use on his Scripting News weblog, which was also introduced in 1997.

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, responding to comments and suggestions, Libby produced a prototype tentatively named RSS 0.91 (RSS standing for Rich Site Summary), that simplified the format and incorporated parts of Winer's scriptingNews format. This they considered an interim measure, with Libby suggesting an RSS 1.0-like format through the so-called Futures Document.

Soon afterwards, Netscape lost interest in RSS/XML, 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 and XML notables to continue its development. At the same time, Winer unilaterally posted a modified version of the RSS 0.91 specification to the Userland website, since it was already in use in their products. He claimed the RSS 0.91 specification was the property of his company, UserLand Software. 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.

The RSS-DEV group went on to produce RSS 1.0 in December 2000 based on a draft proposal of amendments to the specification presented by Tristan Louis. 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 by himself RSS 0.92, a minor and supposedly compatible set of changes to RSS 0.91 based on the same proposal. In April 2001, he published a draft of RSS 0.93 which was almost identical to 0.92. A draft RSS 0.94 surfaced in August, reverting the changes made in 0.93, and adding a type attribute to the description element.

In September 2002, Winer released a final successor to RSS 0.92, known as RSS 2.0 and emphasizing "Really Simple Syndication" as the meaning of the three-letter abbreviation. The RSS 2.0 spec removed the type attribute added in RSS 0.94 and allowed people to add extension elements using XML namespaces. Several versions of RSS 2.0 were released, but the version number of the document model was not changed.

In November, 2002, the New York Times began offering its readers the ability to subscribe to RSS news feeds related to various topics. In January, 2003, David Winer called the New York Time's adoption of RSS the "tipping point" in driving the RSS format's becoming a de facto standard.

In July, 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.

Winer was criticized for unilaterally creating a new format and raising the version number. In response, RSS 1.0 coauthor Aaron Swartz published RSS 3.0, a non-XML textual format. The format was possibly intended as a parody and only a few implementations were ever made.

In January 2005, Sean B. Palmer and Christopher Schmidt produced a preliminary draft of RSS 1.1. It was intended as a bugfix for 1.0, removing little-used features, simplifying the syntax and improving the specification based on the more recent RDF specifications. As of July 2005, RSS 1.1 had amounted to little more than an academic exercise.

In August 2005, Jonathan Avidan launched his own project to create an "RSS 3", though apparently without backing from anyone in the RSS industry, and the project failed to take off. Sean B. Palmer and Morbus Iff, claiming to be acting on behalf of Aaron Swartz, sent a cease-and-desist notice for abuse of the RSS 3 name.

In November 2005, Microsoft proposed its Simple Sharing Extensions to RSS, informally named "Real Simple Synchronization"  by Colm Smyth.

In December 2005, the Microsoft IE team and Outlook team have announced in their blogs that they will be adopting the RSS icon,, first used in the Mozilla Firefox browser, effectively making the orange square with white radio waves the industry standard. Also in February 2006, Opera announced they too will add the orange square in their next release of Opera 9.

Incompatibilities
As noted above, there are several different versions of RSS, falling into two major branches (RDF and 2.*). The RDF, or RSS 1.* branch includes the following versions:


 * RSS 0.90 was the original Netscape RSS version. This RSS was called RDF Site Summary, but was based on an early working draft of the RDF standard, and was not compatible with the final RDF Recommendation.
 * RSS 1.0 and 1.1 are an open format by the "RSS-DEV Working Group", again standing for RDF Site Summary. RSS 1.0 is an RDF format like RSS 0.90, but not fully compatible with it, since 1.0 is based on the final RDF 1.0 Recommendation.

The RSS 2.* branch (initially UserLand, now Harvard) includes the following versions:


 * RSS 0.91 is the simplified RSS version released by Netscape, and also the version number of the simplified version championed by Dave Winer from Userland Software. The Netscape version was now called Rich Site Summary, this was no longer an RDF format, but was relatively easy to use. It remains the most common RSS variant.
 * RSS 0.92 through 0.94 are expansions of the RSS 0.91 format, which are mostly compatible with each other and with Winer's version of RSS 0.91, but are not compatible with RSS 0.90. In all Userland RSS 0.9x specifications, RSS was no longer an acronym.
 * RSS 2.0.1 has the internal version number 2.0. RSS 2.0.1 was proclaimed to be "frozen", but still updated shortly after release without changing the version number. RSS now stood for Really Simple Syndication.  The major change in this version is an explicit extension mechanism using XML Namespaces.

For the most part, later versions in each branch are backward-compatible with earlier versions (aside from non-conformant RDF syntax in 0.90), and both versions include properly documented extension mechanisms using XML Namespaces, either directly (in the 2.* branch) or through RDF (in the 1.* branch). Most syndication software supports both branches. Mark Pilgrim's article "The Myth of RSS Compatibility" discusses RSS version compatibility in more detail.

The extension mechanisms make it possible for each branch to track innovations in the other. For example, the RSS 2.* branch was the first to support enclosures, making it the current leading choice for podcasting, and as of mid-2005 is the format supported for that use by iTunes and other podcasting software; however, an enclosure extension is now available for the RSS 1.* branch, mod_enclosure. Likewise, the RSS 2.* core specification does not support providing full-text in addition to a synopsis, but the RSS 1.* markup can be (and often is) used as an extension. There are also several common outside extension packages available, include a new proposal from Microsoft for use in Internet Explorer 7.

The most serious compatibility problem is with HTML markup. Userland's RSS reader&mdash;generally considered as the reference implementation&mdash;did not originally filter out HTML markup from feeds. As a result, publishers began placing HTML markup into the titles and descriptions of items in their RSS feeds. This behaviour has become widely expected of readers, to the point of becoming a de facto standard, though there is still some inconsistency in how software handles this markup, particularly in titles. The RSS 2.0 specification was later updated to include examples of entity-encoded HTML, however all prior plain text usages remain valid.

Atom
In reaction to recognised issues with RSS (and because RSS 2.0 is frozen), a third group began a new syndication specification, Atom, in June 2003, and their work was later adopted by Internet Engineering Task Force (IETF).

The relative benefits of Atom and the two RSS branches are currently a subject of heated debate within the Web-syndication community. Supporters claim that Atom improves on RSS by relying on standard XML features, and by specifying a payload container that can handle many different kinds of content unambiguously. Opponents claim that Atom unnecessarily introduces a third branch of syndication specifications, further confusing the marketplace.

For a comparison of Atom 1.0 to RSS 2.0 from the point of view of Atom's developers see Atom Compared to RSS 2.0.

BitTorrent and RSS
The peer-to-peer application BitTorrent has also recently announced support for RSS. Such feeds (also termed as Torrent/RSS-es) will allow client softwares to non-interactively download files (also known as Broadcatching). Almost all the major bittorent client software already offer RSS support. More information.

Example
The following is an example of an RSS 1.0 file.





 XML.com http://xml.com/pub XML.com features a rich mix of information and services for the XML community.      

 XML.com http://www.xml.com http://xml.com/universal/images/xml_tiny.gif

 Processing Inclusions with XSLT http://xml.com/pub/2000/08/09/xslt/xslt.html Processing document inclusions with general XML tools can be     problematic. This article proposes a way of preserving inclusion information through SAX-based processing.

 Putting RDF to Work http://xml.com/pub/2000/08/09/rdfdb/index.html Tool and API support for the Resource Description Framework is slowly coming of age. Edd Dumbill takes a look at RDFDB, one of the most exciting new RDF toolkits.

 Search XML.com Search XML.com's XML collection s    http://search.xml.com 

The following is an example of an RSS 2.0 file.

  <channel> <title>Birthday Bash Interviews</title> <link> http://kccnfm100.com/ </link> <description>Natural Vibrations.</description> <language>en-us</language> <pubDate>Tue, 10 Jun 2003 04:00:00 GMT</pubDate> <lastBuildDate>Tue, 10 Jun 2003 09:41:01 GMT</lastBuildDate> <docs> http://blogs.law.harvard.edu/tech/rss </docs> <generator>Weblog Editor 2.0</generator> <managingEditor>editor@example.com</managingEditor> <webMaster>webmaster@example.com</webMaster> <item> <title>Star City</title> <link> http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp </link> <description>How do Americans get ready to work with Russians aboard the International Space Station? They take a crash course in culture, language and protocol at Russia's Star City.</description> <pubDate>Tue, 03 Jun 2003 09:39:21 GMT</pubDate> <guid> http://liftoff.msfc.nasa.gov/2003/06/03.html#item573 </guid> </item> <item> <description>Sky watchers in Europe, Asia, and parts of Alaska and Canada will experience a partial eclipse of the Sun on Saturday, May 31st.</description> <pubDate>Fri, 30 May 2003 11:06:42 GMT</pubDate> <guid> http://liftoff.msfc.nasa.gov/2003/05/30.html#item572 </guid> </item> <item> <title>The Engine That Does More</title> <link> http://liftoff.msfc.nasa.gov/news/2003/news-VASIMR.asp </link> <description>Before man travels to Mars, NASA hopes to design new engines that will let us fly through the Solar System more quickly. The proposed VASIMR engine would do that.</description> <pubDate>Tue, 27 May 2003 08:37:32 GMT</pubDate> <guid> http://liftoff.msfc.nasa.gov/2003/05/27.html#item571 </guid> </item> <item> <title>Astronauts' Dirty Laundry</title> <link> http://liftoff.msfc.nasa.gov/news/2003/news-laundry.asp </link> <description>Compared to earlier spacecraft, the International Space Station has many luxuries, but laundry facilities are not one of them. Instead, astronauts have other options.</description> <pubDate>Tue, 20 May 2003 08:56:02 GMT</pubDate> <guid> http://liftoff.msfc.nasa.gov/2003/05/20.html#item570 </guid> </item> </channel> </rss>

Notes and references

 * 1)  Winer, Dave, 12 December, 1997. Scripting.com: Scripting News in XML
 * 2)  Libby, Dan, 10 July, 1999. RSS 0.91 Spec, revision 3
 * 3)  Winer, Dave, 4 June, 2000. RSS 0.91: Copyright and Disclaimer
 * 4)  RSS-DEV Working Group, December 9, 2000. RDF Site Summary (RSS) 1.0''
 * 5)  Winer, Dave, 25 December, 2000. RSS 0.92 Specification
 * 6)  Winer, Dave, 20 April, 2001. RSS 0.93 Specification
 * 7)  Berkman Center, 15 July, 2003. RSS 2.0 Specification moves to Berkman
 * 8)  Swartz, Aaron, 6 September, 2002. The Road to RSS 3.0 and RSS 3.0
 * 9)   Palmer, Sean B. and Christopher Schmidt, 23 January, 2005. RSS 1.1: RDF Site Summary
 * 10)  Avidan, Jonathan, August 2005. RSS 3 Project
 * 11)  Palmer, Sean B., 20 August, 2005. ''RSS 3: Cease and Desist Notice

Specifications

 * RSS 0.91 Spec, revision 3
 * RSS 1.0 Specifications (RDF Site Summary 1.0) Modules
 * RSS 2.0 Specifications Modules
 * (proposed) Simple Sharing Extensions to RSS (Microsoft)
 * rss-extensions.org, a proposed list of RSS extensions by companies such as Microsoft, Apple and others
 * RSS Tutorial for Content Publishers and Webmasters

History and context

 * RSS History (Joseph Reagle)
 * RSS History (Dave Winer)
 * RSS Political Faq (Dave Winer)
 * History of the RSS Fork (Mark Pilgrim)
 * RSS 2.0 And Atom 1.0 Compared (various/wiki)
 * Content feeds with RSS 2.0

Tutorials and references

 * Building a RSS feed, step by step. And using it.
 * RSS Quick Summary (Sam Ruby)
 * Usage Study, RSS—Crossing into the Mainstream (Ipsos Insight/Yahoo!), PDF

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