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RSS (file format)

2007 Schools Wikipedia Selection. Related subjects: Computer Programming

   CAPTION: RSS

   The Firefox and Internet Explorer 7 Feed icon.
   Screenshot of a RSS feed as seen in Mozilla Thunderbird
   File extension: .rss, .xml
     MIME type:    application/rss+xml (unregistered)
   Extended from:  XML

   RSS is a family of web feed formats used to publish frequently updated
   pages, such as blogs or news feeds. Consumers of RSS content use
   special browsers called aggregators to watch for new content in dozens
   or even hundreds of web feeds. 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".

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 or Forté Agent: an
   example of such applications are nntp//rss, a Java coded program, or
   RSS Feed Converter a script for the popular mail-newsserver Hamster.

   Web-based feed readers and news aggregators such as YourLiveWire or
   NewsGator Online 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", an orange rectangle, a feed icon , or with the
   letters XML or RSS . Many news aggregators such as My Yahoo! 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.

   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 flythough
   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).

   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 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 .

   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 scripting news 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. 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, 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 Centre
   for the Internet & Society .

   In January 2005, Sean B. Palmer, Christopher Schmidt, and Cody Woodard
   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 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 .

   In December 2005, the Microsoft IE team and Outlook team announced in
   their blogs that they will be adopting the feed icon first used in the
   Mozilla Firefox browser , 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 will add the orange square in their next release of Opera 9.

   In January 2006, Rogers Cadenhead relaunched the RSS Advisory Board in
   order to move the RSS format forward

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" 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, 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 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 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) 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:
     * Ecommerce RSS 2.0 Module
     * Media RSS 2.0 Module
     * OpenSearch RSS 2.0 Module

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.
<?xml version="1.0"?>

<rdf:RDF
 xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 xmlns="http://purl.org/rss/1.0/">

 <channel rdf:about="http://www.xml.com/xml/news.rss">
   <title>XML.com</title>
   <link>http://xml.com/pub</link>
   <description>
     XML.com features a rich mix of information and services
     for the XML community.
   </description>
   <image rdf:resource="http://xml.com/universal/images/xml_tiny.gif" />
   <items>
     <rdf:Seq>
       <rdf:li resource="http://xml.com/pub/2000/08/09/xslt/xslt.html" />
       <rdf:li resource="http://xml.com/pub/2000/08/09/rdfdb/index.html" />
     </rdf:Seq>
   </items>
   <textinput rdf:resource="http://search.xml.com" />
 </channel>

 <image rdf:about="http://xml.com/universal/images/xml_tiny.gif">
   <title>XML.com</title>
   <link>http://www.xml.com</link>
   <url>http://xml.com/universal/images/xml_tiny.gif</url>
 </image>

 <item rdf:about="http://xml.com/pub/2000/08/09/xslt/xslt.html">
   <title>Processing Inclusions with XSLT</title>
   <link>http://xml.com/pub/2000/08/09/xslt/xslt.html</link>
   <description>
    Processing document inclusions with general XML tools can be
    problematic. This article proposes a way of preserving inclusion
    information through SAX-based processing.
   </description>
 </item>

 <item rdf:about="http://xml.com/pub/2000/08/09/rdfdb/index.html">
   <title>Putting RDF to Work</title>
   <link>http://xml.com/pub/2000/08/09/rdfdb/index.html</link>
   <description>
    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.
   </description>
 </item>

 <textinput rdf:about="http://search.xml.com">
   <title>Search XML.com</title>
   <description>Search XML.com's XML collection</description>
   <name>s</name>
   <link>http://search.xml.com</link>
 </textinput>
</rdf:RDF>

   The following is an example of an RSS 2.0 file.
<?xml version="1.0"?>
<rss version="2.0">
  <channel>
    <title>Liftoff News</title>
    <link>http://liftoff.msfc.nasa.gov/</link>
    <description>Liftoff to Space Exploration.</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, langua
ge
        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>
      <title>Space Exploration</title>
      <link>http://liftoff.msfc.nasa.gov/</link>
      <description>Sky watchers in Europe, Asia, and parts of Alaska and Canada
        will experience a partial eclipse of the Sun on Saturday, May 31st.</des
cription>
      <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 propose
d
        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>

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   with only minor checks and changes (see www.wikipedia.org for details
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