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RSS is a family of web feed? formats used to publish frequently updated digital content, such as blogs,? news feeds or podcasts.

Users of RSS content use programs called feed 'readers' or 'aggregators': the user 'subscribes' to a feed by supplying to their reader a link to the feed; the reader can then check the user's subscribed feeds to see if any of those feeds have new content since the last time it checked, and if so, retrieve that content and present it to the user.

The initials "RSS" are variously used to refer to the following standards:

  • Really Simple Syndication (RSS 2.0)
  • Rich Site Summary (RSS 0.91, RSS 1.0)
  • RDF? Site Summary (RSS 0.9 and 1.0)

RSS formats are specified in XML (a generic specification for data formats). RSS delivers its information as an XML file called an "RSS feed", "webfeed", "RSS stream", or "RSS channel".

Contents
1 Usage
2 History
3 Incompatibilities
4 Atom
5 Modules
6 BitTorrent and RSS
7 Example
8 References
8.1 Specifications
8.2 Articles

Usage


Programs known as feed readers or aggregators can check a list of feeds on behalf of a user and display any updated articles that they find. 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. Client-side readers and aggregators are typically constructed as standalone programs or extensions to existing programs such as web browsers? and Email? readers. Many browsers have integrated support for RSS feeds. There also are other applications that can convert an RSS feed into several usenet articles, viewable through the major newsreader software such as Mozilla Thunderbird (http://www.mozilla.com/thunderbird/) or Forté Agent (http://www.forteinc.com).

Web-based feed readers and news aggregators such as NewsGator Online (http://www.newsgator.com/Home.aspx) 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 Bloglines.?

On Web pages, web feeds (RSS or Atom) are typically linked with the word "Subscribe", an orange rectangle, a feed icon|16px,? or with the letters XML? or RSS.? Many news aggregators such as My Yahoo!? [1] (http://my.yahoo.com) publish subscription buttons for use on Web pages to simplify the process of adding news feeds.

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. These originated from push and pull technologies. Two of the earliest examples are Backweb? and Pointcast.{{cn}}?

Between 1995 and 1997, Ramanathan V. Guha? at Apple Computer's? Advanced Technology Group developed the Meta Content Framework? (MCF). MCF was a specification for structuring metadata information about web sites and other data, and the basis of Project X? (aka Hot Sauce), a 3D flythrough visualizer for the web. When the research project was discontinued, Guha left Apple for Netscape, where he adapted MCF to use XML and created the first version of the Resource Description Framework? (RDF).{{cn}}

In 1997? Microsoft? created Channel Definition Format for the Active Channel feature of Internet Explorer? 4.0, which never became popular. This was probably due to CDF being focused on commercial application of the concept and the extensive resources it required at a time when people were mostly on dial-up. Backweb and Pointcast were geared towards news, much like a personal API feed. Backweb later morphed into providing software updates, a precursor to the push update features used by various companies now.

Dave Winer? also designed his own XML syndication format for use on his Scripting News weblog, which was also introduced in 1997.{{cite web |url=http://davenet.scripting.com/1997/12/15/scriptingNewsInXML |title=Scripting News in XML |author=Winer, Dave |date=1997-12-15? |publisher=Scripting News |accessdate=2006-10-31 }}

RDF Site Summary, the first version of RSS, was created by Ramanathan V. Guha? of Netscape? in March 1999 for use on the My Netscape? portal. This version became known as RSS 0.9.{{cite web |url=http://my.netscape.com/publish/help/quickstart.html |title=My Netscape Network: Quick Start |archiveurl=http://web.archive.org/web/20001208063100/http://my.netscape.com/publish/help/quickstart.html |archivedate=2000-12-08 |publisher=Netscape Communications? |accessdate=2006-10-31 }} In July 1999, responding to comments and suggestions, Dan Libby? produced a prototype tentatively named RSS 0.91{{cite web |url=http://my.netscape.com/publish/formats/rss-spec-0.91.html |title=RSS 0.91 Spec, revision 3 |author=Libby, Dan |date=1999-07-10? |publisher=Netscape Communications? |accessdate=2006-10-31 }} (RSS standing for Rich Site Summary), that simplified the format and incorporated parts of Winer's scripting news format. This they considered an interim measure, with Libby suggesting an RSS 1.0-like format through the so-called Futures Document.{{cite web |url=http://my.netscape.com/publish/help/futures.html |title=MNN Future Directions |archiveurl=http://web.archive.org/web/20001204123600/http://my.netscape.com/publish/help/futures.html |archivedate=2000-12-04 |publisher=Netscape Communications? |accessdate=2006-10-31 }}

In April 2001,? in the midst of AOL's acquisition and subsequent restructuring of Netscape properties, a re-design of the My Netscape portal removed RSS/XML support. The RSS 0.91 DTD was removed during this re-design, but in response to feedback, Dan Libby? was able to restore the DTD, but not the RSS validator previously in place. In response to comments within the RSS community at the time, Lars Marius Garshol,? to whom (co?)authorship of the original 0.9 DTD is sometimes attributed, commented, "What I don't understand is all this fuss over Netscape removing the DTD. A well-designed RSS tool, whether it validates or not, would not use the DTD at Netscape's site in any case. There are several mechanisms which can be used to control the dereferencing of references from XML documents to their DTDs. These should be used. If not the result will be as described in the article." {{cite web |url=http://www.webreference.com/authoring/languages/xml/rss/1/ |title=The Evolution of RSS |author=Andrew King |date=2003-04-13? |accessdate=2007-01-17 }}

Effectively, this left 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.{{cite? web |url=http://backend.userland.com/rss091#copyrightAndDisclaimer |title=RSS 0.91: Copyright and Disclaimer |author=Winer, Dave |date=2000-06-04? |publisher=UserLand Software? |accessdate=2006-10-31 }} 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.{{cite web |url=http://web.resource.org/rss/1.0/spec |title=RDF Site Summary (RSS) 1.0 |author=RSS-DEV Working Group |date=2000-12-09? |accessdate=2006-10-31 }} 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,{{cite web |url=http://backend.userland.com/rss092 |title=RSS 0.92 Specification |author=Winer, Dave |date=2000-12-25? |publisher=UserLand Software? |accessdate=2006-10-31 }} 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.{{cite web |url=http://backend.userland.com/rss093 |title=RSS 0.93 Specification |author=Winer, Dave |date=2001-04-20? |publisher=UserLand Software? |accessdate=2006-10-31 }} 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,? Winer called the New York Times' 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.{{cite? web |url=http://blogs.law.harvard.edu/tech/announceRss2 |title=RSS 2.0 Specification moves to Berkman |date=2003-07-15? |publisher=Berkman Center for the Internet & Society? |accessdate=2006-10-31 }}

In January 2005,? Sean B. Palmer,? Christopher Schmidt,? and Cody Woodard? produced a preliminary draft of RSS 1.1.{{cite web |url=http://inamidst.com/rss1.1/ |title=RSS 1.1: RDF Site Summary |author=Palmer, Sean B. and Christopher Schmidt |date=2005-01-23? |accessdate=2006-10-31 }} 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 April 2005,? Apple Computer? released Safari? 2.0 with RSS Feed capabilities built in. Safari delivered the ability to read RSS feeds, and bookmark them, with built-in search features. Safari's RSS button is a blue rounded rectangle with RSS written inside in white, Safari's RSS icon/button.? The favicon? displayed defaults to a newspaper icon Safari's feed [[favicon.]].?

In November 2005,? Microsoft proposed its Simple Sharing Extensions? to RSS.{{cite web |url=http://msdn.microsoft.com/xml/rss/sse/ |title=Simple Sharing Extensions for RSS and OPML |date=2006-01-12? |publisher=Microsoft? |accessdate=2006-10-31 }}

In December 2005,? the Microsoft IE team (http://blogs.msdn.com/rssteam/archive/2005/12/14/503778.aspx) and Outlook team (http://blogs.msdn.com/michael_affronti/archive/2005/12/15/504316.aspx) announced in their blogs that they will be adopting the feed icon (http://feedicons.com/) first used in the Mozilla Firefox? browser? 16px,? effectively making the orange square with white radio waves the industry standard for both RSS and related formats such as Atom. Also in February 2006, Opera Software? announced they too would add the orange square in their Opera? 9 release.

In January 2006,? Rogers Cadenhead? relaunched (http://www.rssboard.org/news/15/rss-advisory-board-goes-public) the RSS Advisory Board in order to move the RSS format forward.

In January 2007,? as part of a revitalization of Netscape by AOL, the FQDN? for my.netscape.com was redirected to a holding page in preparation for an impending relaunch, and as a result some news feeders using RSS 0.91 stopped working (http://news.bbc.co.uk/2/hi/technology/6263501.stm). The DTD has again been restored.

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 is 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.
  • RSS 1.1 is also an open format and is intended to update and replace RSS 1.0. The specification is an independent draft not supported or endorsed in any way by the RSS-Dev Working Group or any other organization.

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" (http://diveintomark.org/archives/2004/02/04/incompatible-rss) 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 [2] (http://www.xs4all.nl/~foz/mod_enclosure.html). 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, including a new proposal from Microsoft? for use in Internet Explorer? 7.

The most serious compatibility problem is with HTML markup. Userland's RSS reader—generally considered as the reference implementation—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 behavior 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

{{main|Atom (standard)}}

In reaction to recognized issues with RSS (and because RSS 2.0 is frozen), a third group began a new syndication specification, Atom,? in June 2003.? Their work was later adopted by the Internet Engineering Task Force? (IETF) leading to the publication of a specification ( RFC 4287 (http://www.ietf.org/rfc/rfc4287)) for the Atom Format in 2005. Work on the Atom Publishing Protocol,? a standards-based protocol for posting to publishing tools is ongoing.

The relative benefits of Atom in comparison to the two RSS branches are a matter of debate within the Web-syndication community. Supporters of Atom claim that it improves on RSS by relying on standard XML features, by specifying a payload container that can handle many different kinds of content unambiguously, and by having a specification maintained by a recognized standards organization. Critics 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 see Atom Compared to RSS 2.0.?

Modules

The primary objective of all RSS modules is to extend the basic XML schema established for more robust syndication of content. This inherently allows for more diverse, yet standardized, transactions without modifying the core RSS specification.

To accomplish this extension, a tightly controlled vocabulary (in the RSS world; "module", in the XML world; "schema") is declared through an XML namespace? to give names to concepts and relationships between those concepts.

Some RSS 2.0 modules with established namespaces:

BitTorrent and RSS

The peer-to-peer? application BitTorrent? has also announced support for RSS. Such feeds (also known as Torrent/RSS-es) will allow client applications to download files automatically (also known as Broadcatching).? Most common BitTorrent clients already offer RSS support.

Example

The following is an example of an RSS 1.0 file. 

 '''''

 
 http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  xmlns="http://purl.org/rss/1.0/">
 
  http://www.xml.com/xml/news.rss">
    XML.com
    http://xml.com/pub
    
      XML.com features a rich mix of information and services 
      for the XML community.
    
    xml_tiny.gif" />
    
      
        http://xml.com/pub/2000/08/09/xslt/xslt.html" />
        http://xml.com/pub/2000/08/09/rdfdb/index.html" />
      
    
    http://search.xml.com" />
  
 
  xml_tiny.gif">
    XML.com
    http://www.xml.com
    xml_tiny.gif
  
 
  http://xml.com/pub/2000/08/09/xslt/xslt.html">
    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.
    
  
 
  http://xml.com/pub/2000/08/09/rdfdb/index.html">
    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.
    
  
 
  http://search.xml.com">
    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. 

 '''''

 
   
     Liftoff News
     http://liftoff.msfc.nasa.gov/
     Liftoff to Space Exploration.
     en-us
     Tue, 10 Jun 2003 04:00:00 GMT
     Tue, 10 Jun 2003 09:41:01 GMT
     http://blogs.law.harvard.edu/tech/rss
     Weblog Editor 2.0
     editor@example.com
     webmaster@example.com
 
     
       Star City
       http://liftoff.msfc.nasa.gov/news/2003/news-starcity.asp
       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.
       Tue, 03 Jun 2003 09:39:21 GMT
       http://liftoff.msfc.nasa.gov/2003/06/03.html#item573
     
     
     
       Space Exploration
       http://liftoff.msfc.nasa.gov/
       Sky watchers in Europe, Asia, and parts of Alaska and Canada
         will experience a partial eclipse of the Sun on Saturday, May 31st.
       Fri, 30 May 2003 11:06:42 GMT
       http://liftoff.msfc.nasa.gov/2003/05/30.html#item572
     
     
     
       The Engine That Does More
       http://liftoff.msfc.nasa.gov/news/2003/news-VASIMR.asp
       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.
       Tue, 27 May 2003 08:37:32 GMT
       http://liftoff.msfc.nasa.gov/2003/05/27.html#item571
     
     
     
       Astronauts' Dirty Laundry
       http://liftoff.msfc.nasa.gov/news/2003/news-laundry.asp
       Compared to earlier spacecraft, the International Space
         Station has many luxuries, but laundry facilities are not one of them.
         Instead, astronauts have other options.
       Tue, 20 May 2003 08:56:02 GMT
       http://liftoff.msfc.nasa.gov/2003/05/20.html#item570

References



Specifications

Articles




  • RSS History (http://blogs.law.harvard.edu/tech/rssVersionHistory) (Dave Winer)
  • RSS Political Faq (http://backend.userland.com/davesRss2PoliticalFaq) (Dave Winer)
  • History of the RSS Fork (http://diveintomark.org/archives/2002/09/06/history_of_the_rss_fork) (Mark Pilgrim)
  • Building a RSS feed (http://www.xul.fr/en-xml-rss.html). Progressive manual with example.



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