A web feed is a data format used for providing users with frequently updated content. Content distributors syndicate a web feed, thereby allowing users to subscribe to it. Making a collection of web feeds accessible in one spot is known as aggregation, which is performed by an aggregator...
formats used to publish frequently updated works—such as blog
Blog
A blog is a type of website or part of a website supposed to be updated with new content from time to time. Blogs are usually maintained by an individual with regular entries of commentary, descriptions of events, or other material such as graphics or video. Entries are commonly displayed in...
entries, news headlines, audio, and video—in a standardized format. An RSS document (which is called a "feed", "web feed", or "channel") includes full or summarized text, plus metadata
Metadata
The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...
such as publishing dates and authorship.
RSS feeds benefit publishers by letting them syndicate
Web syndication
Web syndication is a form of syndication in which website material is made available to multiple other sites. Most commonly, web syndication refers to making web feeds available from a site in order to provide other people with a summary or update of the website's recently added content...
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
file format allows the information to be published once and viewed by many different programs. They benefit readers who want to subscribe to timely updates from favorite websites or to aggregate feeds from many sites into one place.
RSS feeds can be read using software called an "RSS reader", "feed reader", or "aggregator", which can be web-based
Web application
A web application is an application that is accessed over a network such as the Internet or an intranet. The term may also mean a computer software application that is coded in a browser-supported language and reliant on a common web browser to render the application executable.Web applications are...
Application software, also known as an application or an "app", is computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with...
, or mobile-device-based. The user subscribes to a feed by entering into the reader the feed's URI
Uniform Resource Identifier
In computing, a uniform resource identifier is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network using specific protocols...
The Feed icon is for indicating that a web feed is available on a web page. It was originally invented for the use of RSS, but it is also common for Atom and other web feeds now....
in a web browser that initiates the subscription process. The RSS reader checks the user's subscribed feeds regularly for new work, downloads any updates that it finds, and provides a user interface
User interface
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...
to monitor and read the feeds. RSS allows users to avoid manually inspecting all of the websites they are interested in, and instead subscribe to websites such that all new content is pushed onto their browsers when it becomes available.
History
The RSS formats were preceded by several attempts at web syndication
Web syndication
Web syndication is a form of syndication in which website material is made available to multiple other sites. Most commonly, web syndication refers to making web feeds available from a site in order to provide other people with a summary or update of the website's recently added content...
that did not achieve widespread popularity. The basic idea of restructuring information about websites goes back to as early as 1995, when Ramanathan V. Guha
Ramanathan V. Guha
Ramanathan V. Guha is an Indian computer scientist. He graduated with B.Tech from Indian Institute of Technology Madras, MS from University of California Berkeley and...
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
The Advanced Technology Group was a corporate research laboratory at Apple Computer from 1986 to 1997. ATG was started by Larry Tesler in October 1986 to study long term research into future technologies that were beyond the time frame or organizational scope of any individual product group. Over...
Meta Content Framework was a specification of a format for structuring metadata about web sites and other data. MCF was developed by Ramanathan V. Guha at Apple Computer between 1995 and 1997...
The Resource Description Framework is a family of World Wide Web Consortium specifications originally designed as a metadata data model...
Site Summary, the first version of RSS, was created by Dan Libby and Ramanathan V. Guha
Ramanathan V. Guha
Ramanathan V. Guha is an Indian computer scientist. He graduated with B.Tech from Indian Institute of Technology Madras, MS from University of California Berkeley and...
at Netscape. It was released in March 1999 for use on the My.Netscape.Com portal. This version became known as RSS 0.9. In July 1999, Dan Libby of Netscape produced a new version, RSS 0.91,
which simplified the format by removing RDF elements and incorporating elements from Dave Winer
Dave Winer
Dave Winer is an American software developer, entrepreneur and writer in New York City. Winer is noted for his contributions to outliners, scripting, content management, and web services, as well as blogging and podcasting...
's scriptingNews syndication format.
Libby also renamed RSS Rich Site Summary and outlined further development of the format in a "futures document".
This would be Netscape's last participation in RSS development for eight years. As RSS was being embraced by web publishers who wanted their feeds to be used on My.Netscape.Com and other early RSS portals, Netscape dropped RSS support from My.Netscape.Com in April 2001 during new owner AOL
AOL
AOL Inc. is an American global Internet services and media company. AOL is headquartered at 770 Broadway in New York. Founded in 1983 as Control Video Corporation, it has franchised its services to companies in several nations around the world or set up international versions of its services...
's restructuring of the company, also removing documentation and tools that supported the format.
Two entities emerged to fill the void, with neither Netscape's help nor approval: The RSS-DEV Working Group
RSS-DEV Working Group
The RSS-DEV Working Group was the outgrowth of a fork in RSS format development. The private, non-commercial working group began with a dozen members in three countries, and was chaired by Rael Dornfest, researcher and developer of the Meerkat RSS-reader software.-History:RSS-0.90 was released by...
UserLand Software is a US software company founded by Dave Winer in 1988. UserLand sells Web content management and blogging software packages and services.-Company History:Dave Winer founded the company in 1988 after leaving Symantec in the spring of 1988...
had published some of the first publishing tools outside of Netscape that could read and write RSS.
Winer published a modified version of the RSS 0.91 specification on the UserLand website, covering how it was being used in his company's products, and claimed copyright to the document. A few months later, UserLand filed a U.S. trademark registration for RSS, but failed to respond to a USPTO trademark examiner's request and the request was rejected in December 2001.
The RSS-DEV Working Group, a project whose members included Guha and representatives of O'Reilly Media
O'Reilly Media
O'Reilly Media is an American media company established by Tim O'Reilly that publishes books and Web sites and produces conferences on computer technology topics...
Moreover Technologies is a provider of business intelligence and news aggregation products for enterprises, also offering free news feeds for consumers...
, produced RSS 1.0 in December 2000. This new version, which reclaimed the name RDF Site Summary from RSS 0.9, reintroduced support for RDF and added XML namespaces support, adopting elements from standard metadata vocabularies such as Dublin Core
Dublin Core
The Dublin Core metadata terms are a set of vocabulary terms which can be used to describe resources for the purposes of discovery. The terms can be used to describe a full range of web resources: video, images, web pages etc and physical resources such as books and objects like artworks...
.
In December 2000, Winer released RSS 0.92
a minor set of changes aside from the introduction of the enclosure element, which permitted audio files to be carried in RSS feeds and helped spark podcast
Podcast
A podcast is a series of digital media files that are released episodically and often downloaded through web syndication...
ing. He also released drafts of RSS 0.93 and RSS 0.94 that were subsequently withdrawn.
In September 2002, Winer released a major new version of the format, RSS 2.0, that redubbed its initials Really Simple Syndication. RSS 2.0 removed the type attribute added in the RSS 0.94 draft and added support for namespaces. To preserve backward compatibility with RSS 0.92, namespace support applies only to other content included within an RSS 2.0 feed, not the RSS 2.0 elements themselves. (Although other standards such as Atom
Atom (standard)
The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol is a simple HTTP-based protocol for creating and updating web resources.Web feeds allow software programs to check for updates published on a...
attempt to correct this limitation, RSS feeds are not aggregated with other content often enough to shift the popularity from RSS to other formats having full namespace support.)
Because neither Winer nor the RSS-DEV Working Group had Netscape's involvement, they could not make an official claim on the RSS name or format. This has fueled ongoing controversy in the syndication development community as to which entity was the proper publisher of RSS.
One product of that contentious debate was the creation of an alternative syndication format, Atom, that began in June 2003. The Atom syndication format, whose creation was in part motivated by a desire to get a clean start free of the issues surrounding RSS, has been adopted as IETF Proposed Standard RFC 4287.
The Berkman Center for Internet & Society is a research center at Harvard University that focuses on the study of cyberspace. Founded at Harvard Law School, the center traditionally focused on internet-related legal issues. On May 15, 2008, the Center was elevated to an interfaculty initiative of...
, where he had just begun a term as a visiting fellow. At the same time, Winer launched the RSS Advisory Board
RSS Advisory board
The RSS Advisory Board is a group founded in July 2003 that publishes the RSS 0.9, RSS 0.91 and RSS 2.0 specifications and helps developers create RSS applications....
Jon Udell is an "Evangelist" at Microsoft. Previously he was lead analyst for the Infoworld Test Center.Udell is author of Practical Internet Groupware, published in 1999 by O'Reilly Media, and is an advisor to O'Reilly's Safari Tech Books Online. He wrote the column "Tangled in the Threads" for...
, a group whose purpose was to maintain and publish the specification and answer questions about the format.
In December 2005, the Microsoft Internet Explorer team and Microsoft Outlook
Microsoft Outlook
Microsoft Outlook is a personal information manager from Microsoft, available both as a separate application as well as a part of the Microsoft Office suite...
team announced on their blogs that they were adopting the feed icon first used in the Mozilla Firefox
Mozilla Firefox
Mozilla Firefox is a free and open source web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. , Firefox is the second most widely used browser, with approximately 25% of worldwide usage share of web browsers...
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
Opera Software ASA is a Norwegian software company, primarily known for its Opera family of web browsers with over 220 million users worldwide. Opera Software is also involved in promoting Web standards through participation in the W3C. The company has its headquarters in Oslo, Norway and is...
followed suit. This effectively made the orange square with white radio waves the industry standard for RSS and Atom feeds, replacing the large variety of icons and text that had been used previously to identify syndication data.
Rogers Cadenhead is a computer book author and web publisher who is currently chairman of the RSS Advisory Board, a group that assists developers in using the RSS 2.0 specification. He graduated from the University of North Texas in 1991 and Lloyd V...
relaunched the RSS Advisory Board without Dave Winer's participation, with a stated desire to continue the development of the RSS format and resolve ambiguities. In June 2007, the board revised their version of the specification to confirm that namespaces may extend core elements with namespace attributes, as Microsoft has done in Internet Explorer 7. According to their view, a difference of interpretation left publishers unsure of whether this was permitted or forbidden.
Example
As RSS files are essentially XML formatted plain text, the RSS file itself is relatively easily read both by automated processes and by humans alike. An example file could have contents such as the following. This could be placed on any appropriate communication protocol for file retrieval, such as http or ftp
File Transfer Protocol
File Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...
, and reading software would use the information to present a neat display to the end user.
RSS Title This is an example of an RSS feed
http://www.someexamplerssdomain.com/main.html Mon, 06 Sep 2010 00:01:00 +0000 Mon, 06 Sep 2009 16:45:00 +0000 1800
Example entry Here is some text containing an interesting description.
http://www.wikipedia.org/ unique string per item Mon, 06 Sep 2009 16:45:00 +0000
Variants
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
Resource Description Framework
The Resource Description Framework is a family of World Wide Web Consortium specifications originally designed as a metadata data model...
Site Summary, but was based on an early working draft of the RDF standard, and was not compatible with the final RDF Recommendation.
The RSS-DEV Working Group was the outgrowth of a fork in RSS format development. The private, non-commercial working group began with a dozen members in three countries, and was chaired by Rael Dornfest, researcher and developer of the Meerkat RSS-reader software.-History:RSS-0.90 was released by...
, 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 originally championed by Dave Winer
Dave Winer
Dave Winer is an American software developer, entrepreneur and writer in New York City. Winer is noted for his contributions to outliners, scripting, content management, and web services, as well as blogging and podcasting...
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.
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.
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.
In the context of telecommunications and computing, a device or technology is said to be backward or downward compatible if it can work with input generated by an older device...
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. "The Myth of RSS Compatibility", an article written in 2004 by RSS critic and Atom
Atom (standard)
The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol is a simple HTTP-based protocol for creating and updating web resources.Web feeds allow software programs to check for updates published on a...
advocate Mark Pilgrim, discusses RSS version compatibility issues 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 is the format supported for that use by iTunes
ITunes
iTunes is a media player computer program, used for playing, downloading, and organizing digital music and video files on desktop computers. It can also manage contents on iPod, iPhone, iPod Touch and iPad....
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
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...
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
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....
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 expected of readers, to the point of becoming a de facto
De facto
De facto is a Latin expression that means "concerning fact." In law, it often means "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established." It is commonly used in contrast to de jure when referring to matters of law, governance, or...
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.
, tracking data from www.syndic8.com indicates that the three main versions of RSS in current use are 0.91, 1.0, and 2.0. Of these, RSS 0.91 accounts for 13 percent of worldwide RSS usage and RSS 2.0 for 67 percent, while RSS 1.0 has a 17 percent share. These figures, however, do not include usage of the rival web feed format Atom. , the syndic8.com website is indexing 546,069 total feeds, of which 86,496 were some dialect of Atom and 438,102 were some dialect of RSS.
Modules
The primary objective of all RSS modules is to extend the basic XML
XML
Extensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
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
XML Namespace
xmlns tagged XML namespaces are used for providing uniquely named elements and attributes in an XML document. They are defined in a W3C recommendation. An XML instance may contain element or attribute names from more than one XML vocabulary...
to give names to concepts and relationships between those concepts.
Some RSS 2.0 modules with established namespaces are:
Although the number of items in an RSS channel are theoretically not limited, some news aggregators do not support RSS files larger than 150KB (if all elements are provided on a new line, this size corresponds to approx. 2,800 lines). For example, applications that rely on the Common Feed List of Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
might handle such files as if they were corrupt, and not open them. Interoperability
Interoperability
Interoperability is a property referring to the ability of diverse systems and organizations to work together . The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to...
can be maximized by keeping the file size under this limit.
Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...
applications also support RSS. Such feeds (also known as Torrent/RSS-es or Torrentcasts) allow client applications to download files automatically from the moment the RSS reader detects them (also known as Broadcatching
Broadcatching
Broadcatching is the downloading of digital content that has been made available over the Internet using RSS.The general idea is to use an automated mechanism to aggregate various web feeds and download content for viewing or presentation purposes....
The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol is a simple HTTP-based protocol for creating and updating web resources.Web feeds allow software programs to check for updates published on a...
are widely supported in all major consumer feed readers. RSS has gained widespread distribution through feed reader implementations earlier than Atom
Atom (standard)
The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol is a simple HTTP-based protocol for creating and updating web resources.Web feeds allow software programs to check for updates published on a...
The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol is a simple HTTP-based protocol for creating and updating web resources.Web feeds allow software programs to check for updates published on a...
has several advantages over RSS, such as less restrictive licensing, IANA
Internet Assigned Numbers Authority
The Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...
xmlns tagged XML namespaces are used for providing uniquely named elements and attributes in an XML document. They are defined in a W3C recommendation. An XML instance may contain element or attribute names from more than one XML vocabulary...
In computing, RELAX NG is a schema language for XML, based on Murata Makoto's RELAX and James Clark's TREX. A RELAX NG schema specifies a pattern for the structure and content of an XML document...
The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol is a simple HTTP-based protocol for creating and updating web resources.Web feeds allow software programs to check for updates published on a...
should be considered the more advanced syndication format between the two.
The following table summarizes those RSS elements that have their equivalents in Atom.
Time to live is a mechanism that limits the lifespan of data in a computer or network. TTL may be implemented as a counter or timestamp attached to or embedded in the data. Once the prescribed event count or timespan has elapsed, data is discarded. In computer networking, TTL prevents a data...
The following is a comparison of notable RSS feed aggregators. Often e-mail programs and web browsers have the ability to display RSS feeds. They are listed here, too.Many BitTorrent clients support RSS feeds for broadcatching ....
Data portability is the ability for people to reuse their data across interoperable applications - the ability for people to be able to control their identity, media and other forms of personal data...
In Web development, a mashup is a Web page or application that uses and combines data, presentation or functionality from two or more sources to create new services...
). In February 2006, Opera Software