The name Atom applies to a pair of related standards. The Atom Syndication Format is an 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....
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...
s, while the Atom Publishing Protocol (AtomPub or APP) is a simple HTTP-based protocol for creating and updating web resources.
Web feeds allow software programs to check for updates published on a website. To provide a web feed, a site owner may use specialized software (such as a content management system
Content management system
A content management system is a system providing a collection of procedures used to manage work flow in a collaborative environment. These procedures can be manual or computer-based...
) that publishes a list (or "feed") of recent articles or content in a standardized, machine-readable format. The feed can then be downloaded by programs that use it, like websites that syndicate content from the feed, or by feed reader programs that allow Internet users to subscribe to feeds and view their content.
A feed contains entries, which may be headlines, full-text articles, excerpts, summaries, and/or links to content on a website, along with various 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...
.
The Atom format was developed as an alternative to RSS
RSS
-Mathematics:* Root-sum-square, the square root of the sum of the squares of the elements of a data set* Residual sum of squares in statistics-Technology:* RSS , "Really Simple Syndication" or "Rich Site Summary", a family of web feed formats...
Benjamin Trott, born , is a co-founder of Six Apart, creator of Movable Type and TypePad. In November 2010, he became Chief Technical Officer of , a new online advertising and software company formed by a merger of ad network VideoEgg with Six Apart.Before joining SAY Media, Trott was also CTO of...
, an advocate of the new format that became Atom, believed that RSS had limitations and flaws—such as lack of on-going innovation and its necessity to remain backward compatible— and that there were advantages to a fresh design.
Proponents of the new format formed the IETF Atom Publishing Format and Protocol Workgroup. The Atom syndication format was published as an IETF proposed standard in RFC 4287 (December 2005), and the Atom Publishing Protocol was published as RFC 5023 (October 2007).
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...
ging community to share recent entries' headlines, full text, and even attached multimedia files. These providers allow other websites to incorporate the blog's "syndicated" headline or headline-and-short-summary feeds under various usage agreements. Atom and other web syndication formats are now used for many purposes, including journalism, marketing, bug-reports, or any other activity involving periodic updates or publications. Atom also provides a standard way to export an entire blog, or parts of it, for backup or for importing into other blogging systems.
It is common to find web feeds on major Web sites, as well as many smaller ones. Some websites let people choose between RSS or Atom formatted web feeds; others offer only RSS or only Atom. In particular, many 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...
A wiki is a website that allows the creation and editing of any number of interlinked web pages via a web browser using a simplified markup language or a WYSIWYG text editor. Wikis are typically powered by wiki software and are often used collaboratively by multiple users. Examples include...
sites offer their web feeds in the Atom format.
A feed reader or "aggregator" program can be used to check feeds and display new articles. Client-side
Client-side
Client-side refers to operations that are performed by the client in a client–server relationship in a computer network.Typically, a client is a computer application, such as a web browser, that runs on a user's local computer or workstation and connects to a server as necessary...
readers may also be designed as standalone programs or as extensions to existing programs like web browser
Web browser
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...
s. Browsers are moving toward integrated feed reader functions.
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 syndicate (combine) 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 several search engines for web feed content.
On Web pages, web feeds (both Atom and RSS) are typically linked with the word "Subscribe" or with the unofficial web feed logo ().
Atom compared to RSS 2.0
When Atom emerged as a format intended to rival or replace RSS
RSS (file format)
RSS is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format...
CNET is a tech media website that publishes news articles, blogs, and podcasts on technology and consumer electronics. Originally founded in 1994 by Halsey Minor and Shelby Bonnie, it was the flagship brand of CNET Networks and became a brand of CBS Interactive through CNET Networks' acquisition...
described the motivation of its creators as follows: "Winer's
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...
opponents are seeking a new format that would clarify RSS ambiguities, consolidate its multiple versions, expand its capabilities, and fall under the auspices of a traditional standards organization."
A brief description of some of the ways Atom 1.0 differs from RSS 2.0 has been given by Tim Bray
Tim Bray
Timothy William Bray is a Canadian software developer and entrepreneur. He co-founded Open Text Corporation and Antarctica Systems. Bray was Director of Web Technologies at Sun Microsystems from early 2004 to early 2010. Since then he has served as a Developer Advocate at Google, focusing on...
, who played a major role in the creation of Atom:
Content model
RSS 2.0 may contain either plain text or escaped HTML as a payload, with no way to indicate which of the two is provided. Atom, on the other hand, provides a mechanism to explicitly and unambiguously label the type of content being provided by the entry, and allows for a broad variety of payload types including plain text, escaped HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....
XHTML is a family of XML markup languages that mirror or extend versions of the widely-used Hypertext Markup Language , the language in which web pages are written....
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....
Base64 is a group of similar encoding schemes that represent binary data in an ASCII string format by translating it into a radix-64 representation...
-encoded binary, and references to external content such as documents, video, audio streams, and so forth.
Date formats
The RSS 2.0 specification relies on the use of RFC 822 formatted timestamps to communicate information about when items in the feed were created and last updated. The Atom working group chose instead to use timestamps formatted according to the rules specified by RFC 3339 (which is a subset of ISO 8601
ISO 8601
ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date and time-related data. It was issued by the International Organization for Standardization and was first published in 1988...
-Mathematics:* Root-sum-square, the square root of the sum of the squares of the elements of a data set* Residual sum of squares in statistics-Technology:* RSS , "Really Simple Syndication" or "Rich Site Summary", a family of web feed formats...
vocabulary has a mechanism to indicate a human language for the feed, there is no way to specify a language for individual items or text elements. Atom, on the other hand, uses the standard xml:lang attribute to make it possible to specify a language context for every piece of human-readable content in the feed.
On the Internet, the Internationalized Resource Identifier is a generalization of the Uniform Resource Identifier . While URIs are limited to a subset of the ASCII character set, IRIs may contain characters from the Universal Character Set , including Chinese or Japanese kanji, Korean, Cyrillic...
s, which allow links to resources and unique identifiers to contain characters outside the US ASCII
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...
-Mathematics:* Root-sum-square, the square root of the sum of the squares of the elements of a data set* Residual sum of squares in statistics-Technology:* RSS , "Really Simple Syndication" or "Rich Site Summary", a family of web feed formats...
vocabulary are not generally reusable in other 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....
vocabularies. The Atom syntax was specifically designed to allow elements to be reused outside the context of an Atom feed document. For instance, it is not uncommon to find atom:link elements being used within RSS 2.0 feeds.
Barriers to adoption
Despite the emergence of Atom as an IETF Proposed Standard and the decision by major companies such as Google
Google
Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
to embrace Atom, use of the older and better-known RSS formats has continued.
RSS 2.0 support for enclosures led directly to the development of podcast
Podcast
A podcast is a series of digital media files that are released episodically and often downloaded through web syndication...
ing. While many podcasting applications, such as 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....
, support the use of Atom 1.0, RSS 2.0 remains the preferred format.
Many sites choose to publish their feeds in only a single format. For example CNN
CNN
Cable News Network is a U.S. cable news channel founded in 1980 by Ted Turner. Upon its launch, CNN was the first channel to provide 24-hour television news coverage, and the first all-news television channel in the United States...
and the New York Times offer their web feeds only in RSS 2.0 format.
News articles about web syndication feeds have increasingly used the term "RSS" to refer generically to any of the several variants of the RSS format such as RSS 2.0 and RSS 1.0 as well as the Atom format.
Background
Before the creation of Atom the primary method of web content syndication was the RSS
RSS (file format)
RSS is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format...
family of formats.
Members of the community who felt there were significant deficiencies with this family of formats were unable to make changes directly to RSS 2.0 because the official specification document stated that it was purposely frozen to ensure its stability.
Sam Ruby is a prominent software developer who has made significant contributions to many of the Apache Software Foundation's open source software projects, and to the standardization of web feeds via his involvement with the Atom web feed standard and the feedvalidator.org web service.He currently...
A wiki is a website that allows the creation and editing of any number of interlinked web pages via a web browser using a simplified markup language or a WYSIWYG text editor. Wikis are typically powered by wiki software and are often used collaboratively by multiple users. Examples include...
to discuss what makes "a well-formed log entry". This initial posting acted as a rallying point. People quickly started using the wiki to discuss a new syndication format to address the shortcomings of RSS
RSS (file format)
RSS is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format...
. It also became clear that the new format could form the basis of a more robust replacement for blog editing protocols such as the Blogger API and LiveJournal
LiveJournal
LiveJournal is a virtual community where Internet users can keep a blog, journal or diary. LiveJournal is also the name of the free and open source server software that was designed to run the LiveJournal virtual community....
XML-RPC is a remote procedure call protocol which uses XML to encode its calls and HTTP as a transport mechanism. "XML-RPC" also refers generically to the use of XML for remote procedure call, independently of the specific protocol...
Client/Server Protocol as well.
The project aimed to develop a web syndication format that was:
"100% vendor neutral,"
"implemented by everybody,"
"freely extensible by anybody, and"
"cleanly and thoroughly specified."
In short order, a project road map was built. The effort quickly attracted more than 150 supporters, including David Sifry of Technorati
Technorati
Technorati is an Internet search engine for searching blogs. By June 2008, Technorati was indexing 112.8 million blogs and over 250 million pieces of tagged social media...
Six Apart Ltd., sometimes abbreviated 6A, is a software company known for creating the Movable Type blogware, TypePad blog hosting service, and Vox. The company also is the former owner of LiveJournal. Six Apart is headquartered in Tokyo and is planning to open a new, U.S.-based office in New York...
Bradley Joseph "Brad" Fitzpatrick , is an American programmer. He is best known as the creator of LiveJournal and is the author of a variety of free software projects such as memcached....
LiveJournal is a virtual community where Internet users can keep a blog, journal or diary. LiveJournal is also the name of the free and open source server software that was designed to run the LiveJournal virtual community....
Jeremy Zawodny is an incoming employee of Craigslist, having left Yahoo!'s platform engineering group. He has been described as "Yahoo!'s MySQL guru"....
Yahoo! Inc. is an American multinational internet corporation headquartered in Sunnyvale, California, United States. The company is perhaps best known for its web portal, search engine , Yahoo! Directory, Yahoo! Mail, Yahoo! News, Yahoo! Groups, Yahoo! Answers, advertising, online mapping ,...
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...
Creative Commons is a non-profit organization headquartered in Mountain View, California, United States devoted to expanding the range of creative works available for others to build upon legally and to share. The organization has released several copyright-licenses known as Creative Commons...
Lawrence "Larry" Lessig is an American academic and political activist. He is best known as a proponent of reduced legal restrictions on copyright, trademark, and radio frequency spectrum, particularly in technology applications, and he has called for state-based activism to promote substantive...
. Other notables supporting Atom include Mark Pilgrim
Mark Pilgrim
Mark Pilgrim is a software developer, writer, and advocate of free software. He authors a popular blog, and has written several books including Dive into Python, a guide to the Python programming language published under the GNU Free Documentation License...
Timothy William Bray is a Canadian software developer and entrepreneur. He co-founded Open Text Corporation and Antarctica Systems. Bray was Director of Web Technologies at Sun Microsystems from early 2004 to early 2010. Since then he has served as a Developer Advocate at Google, focusing on...
Aaron Swartz is an American programmer, writer, political organizer and Internet activist. He is best known in programming circles for co-authoring the RSS 1.0 specification...
is a Japanese activist, entrepreneur, venture capitalist and Director of the MIT Media Lab.Ito has received recognition for his role as an entrepreneur focused on Internet and technology companies and has founded, among other companies, PSINet Japan, Digital Garage and Infoseek Japan. He maintains...
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...
RSS is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format...
, gave tentative support to the new endeavor.
After this point, discussion became chaotic, due to the lack of a decision-making process. The project also lacked a name, tentatively using "Pie," "Echo," "Atom," and "Whatever" (PEAW) before settling on Atom. After releasing a project snapshot known as Atom 0.2 in early July 2003, discussion was shifted off the wiki.
Atom 0.3 and adoption by Google
The discussion then moved to a newly set up mailing list. The next and final snapshot during this phase was Atom 0.3, released in December 2003. This version gained widespread adoption in syndication tools, and in particular it was added to several Google
Google
Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...
Google News is a free news aggregator provided by Google Inc, selecting recent items from thousands of publications by an automatic aggregation algorithm....
Gmail is a free, advertising-supported email service provided by Google. Users may access Gmail as secure webmail, as well via POP3 or IMAP protocols. Gmail was launched as an invitation-only beta release on April 1, 2004 and it became available to the general public on February 7, 2007, though...
GData provides a simple protocol for reading and writing data on the Internet, designed by Google. GData combines common XML-based syndication formats with a feed-publishing system based on the Atom Publishing Protocol, plus some extensions for handling queries. It relies on XML or JSON as a data...
are based on Atom 1.0 and RSS 2.0.
Atom 1.0 and IETF standardization
In 2004, discussions began about moving the project to a standards body such as the World Wide Web Consortium
World Wide Web Consortium
The World Wide Web Consortium is the main international standards organization for the World Wide Web .Founded and headed by Tim Berners-Lee, the consortium is made up of member organizations which maintain full-time staff for the purpose of working together in the development of standards for the...
The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...
(IETF). The group eventually chose the IETF and the Atompub working group was formally set up in June 2004, finally giving the project a charter and process. The Atompub working group is co-chaired by Tim Bray
Tim Bray
Timothy William Bray is a Canadian software developer and entrepreneur. He co-founded Open Text Corporation and Antarctica Systems. Bray was Director of Web Technologies at Sun Microsystems from early 2004 to early 2010. Since then he has served as a Developer Advocate at Google, focusing on...
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....
Paul Hoffman is a Santa Cruz-based Internet pioneer.Hoffman has been involved with the Internet Engineering Task Force since the early 1990s, is current chair of the IETF ipsecme working group, and has chaired numerous working groups in the past...
. Initial development was focused on the syndication format.
The Atom Syndication Format was issued as a Proposed Standard in IETF RFC 4287 in December 2005. The co-editors were Mark Nottingham
Mark Nottingham
Mark Nottingham is an influential web infrastructure developer who is one of the authors of the Atom and WS-I Basic Profile specifications, the author of RFC 4229: HTTP Header Registrations, and the chairman of the IETF HTTPBIS Working Group and W3C Web Services Addressing Working Group...
Robert Sayre is a software developer who wrote the Atom specification along with Mark Nottingham. Sayre joined Mozilla in 2006, where he worked until 31 May 2011 as an engineering director...
. This document is known as atompub-format in IETF's terminology. The Atom Publishing Protocol was issued as a Proposed Standard in IETF RFC 5023 in October 2007. Two other drafts have not been standardized.
Example of an Atom 1.0 feed
An example of a document in the Atom Syndication Format:
Example Feed A subtitle.
urn:uuid:60a76c80-d399-11d9-b91C-0003939e0af6 2003-12-13T18:30:02Z John Doe johndoe@example.com
Atom-Powered Robots Run Amok
urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2003-12-13T18:30:02Z Some text.
Including in XHTML
The following tag should be placed into the head of an XHTML document to provide a link to an ATOM Feed.
hAtom is a draft Microformat for marking up HTML, using classes and rel attributes, content on web pages that contain blog entries or similar chronological content...
A microformat is a web-based approach to semantic markup which seeks to re-use existing HTML/XHTML tags to convey metadata and other attributes in web pages and other contexts that support HTML, such as RSS...
for marking up (X)HTML so that Atom feeds can be derived from it
The Open Data Protocol is an open web protocol for querying and updating data. The protocol allows for a consumer to query a datasource over the HTTP protocol and get the result back in formats like Atom, JSON or plain XML, including pagination, ordering or filtering of the data.Many of the...
– a set of extensions to the AtomPub developed by Microsoft
Content Management Interoperability Services is a specification for improving interoperability between Enterprise Content Management systems. OASIS, a web standards consortium, approved CMIS as an OASIS Specification on May 1, 2010....
– provides an extension to AtomPub for content management
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...
External links
Atom standard
RFC 4287 – "The Atom Syndication Format"
RFC 5023 – "The Atom Publishing Protocol"
Atom advocacy / evangelism
AtomEnabled.org – An unofficial website following the Atom project
A microformat is a web-based approach to semantic markup which seeks to re-use existing HTML/XHTML tags to convey metadata and other attributes in web pages and other contexts that support HTML, such as RSS...
.gif)
).