Atom (web standard)

{{Use dmy dates|date=June 2022}} {{Short description|Web standards}} {{Infobox file format | name = Atom | icon = [[Image:Application atom+xml.svg|128px]] | caption = The [[feed icon]] used on the official wiki | extension = {{tt|.atom}}, {{tt|.xml}} | mime = application/atom+xml | owner = [[Internet Engineering Task Force]] | creatorcode = | genre = [[Web syndication]] | released = {{IETF RFC|4287}} {{Start date and age|2005|12}} | open = Yes | url = {{URL|https://www.ietf.org/rfc/rfc4287.txt}} | containerfor = Updates of a website and its related metadata ([[Web feed]]) | containedby = | extendedfrom = [[XML]] | extendedto = }} [[File:Tiny Tiny RSS English Interface.png|thumb|upright=1.5|User interface of a feed reader]]

The name '''Atom''' applies to a pair of related [[Web standards]]. The '''Atom Syndication Format''' is an [[XML]] language used for [[web feed]]s, while the '''Atom Publishing Protocol''' ('''AtomPub''' or '''APP''') is a simple [[HTTP]]-based protocol for creating and updating web resources.<ref name="why_echo" />

Web feeds allow [[software]] programs to check for updates published on a website. To provide a web feed, the site owner may use specialized software (such as a [[content management system]]) 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 or links to content on a website along with various [[metadata]].

The Atom format was developed as an alternative to [[RSS]]. [[Benjamin Trott|Ben Trott]], 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 compatibility|backward compatible]]—and that there were advantages to a fresh design.<ref name="why_echo">{{cite web |first=Benjamin |last=Trott |url=http://www.sixapart.com/about/news/2003/06/why_we_need_ech.html |title=Why We Need Echo |work=Six Apart — News and Events |date=29 June 2003 |archive-url=https://web.archive.org/web/20080216234454/http://www.sixapart.com/about/news/2003/06/why_we_need_ech.html |archive-date=16 February 2008 }}</ref>

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).

==Usage==

The [[blog]]ging community uses [[web feed]]s to share recent entries' headlines, full text, and even attached multimedia files.<ref>See also [[podcast]]ing, [[vodcast]]ing, [[broadcasting]], [[screencast]]ing, [[vlog]]ging, and [[MP3 blog]]s.</ref> The providers allow other websites to incorporate a blog's "syndicated" headline or headline-and-short-summary feeds under various usage agreements. {{As of | 2016}} people use Atom and other web-syndication formats 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 websites, as well as on many smaller ones.{{citation needed|date=April 2016}} Some websites let people choose between RSS- or Atom-formatted web feeds; others offer only RSS or only Atom. In particular, many blog and [[wiki]] sites offer their web feeds in the Atom format.

A [[feed reader]] or "aggregator" program can be used to check feeds and to display new articles. [[Client-side]] readers may also be designed as standalone programs or as extensions to existing programs like [[web browser]]s.

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.

==Atom compared to RSS 2.0== When Atom emerged as a format intended to rival or replace [[RSS]], [[CNET]] described the motivation of its creators as follows: "[[Dave Winer|Winer's]] 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."<ref>{{cite web | title=Battle of the blog, Dispute exposes bitter power struggle behind Web logs| url=http://news.cnet.com/Battle-of-the-blog/2009-1032_3-5059006.html | publisher=news.cnet.com | date=4 August 2003 | access-date=6 August 2008 | archive-date=6 August 2009 | archive-url=https://web.archive.org/web/20090806234534/http://news.cnet.com/Battle-of-the-blog/2009-1032_3-5059006.html | last=Festa | first=Paul | quote=The conflict centers on something called Really Simple Syndication (RSS), a technology widely used to syndicate blogs and other Web content. The dispute pits Harvard Law fellow Dave Winer, the blogging pioneer who is the key gatekeeper of RSS, against advocates of a different format. | url-status=dead}}</ref>

A brief description of some of the ways Atom 1.0 differs from RSS 2.0 has been given by [[Tim Bray]], who played a major role in the creation of Atom:<ref>{{cite web |url=http://www.intertwingly.net/wiki/pie/Rss20AndAtom10Compared |title=RSS 2.0 and Atom 1.0 Compared |work=Atom Wiki |access-date=4 December 2007 | archive-url= https://web.archive.org/web/20071204213325/http://www.intertwingly.net/wiki/pie/Rss20AndAtom10Compared#major| archive-date= 4 December 2007 | url-status= live}}</ref>

===Date formats===

The RSS 2.0 specification relies on the use of {{IETF 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 {{IETF RFC|3339}} (which is a subset of [[ISO 8601]]; see [http://tools.ietf.org/html/rfc3339#appendix-A Appendix A in RFC 3339] for differences).

===Internationalization===

While the [[RSS]] 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.

Atom also differs from RSS in that it supports the use of [[Internationalized Resource Identifier]]s, which allow links to resources and unique identifiers to contain characters outside the US [[ASCII]] character set.

===Modularity===

The elements of the RSS vocabulary are not generally reusable in other [[XML]] 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]] to embrace Atom, use of the older and better-known RSS formats has continued. There are several reasons for this:

* RSS 2.0 support for [[RSS enclosure|enclosures]] led directly to the development of [[podcast]]ing. While many podcasting applications support the use of Atom 1.0, RSS 2.0 remains the preferred format. While [[iTunes]] previously supported Atom,{{Clarify|post-text=(see [[Talk:Atom (web standard)#To what degree did iTunes ever support Atom?|talk]])|date=April 2026}} it dropped support in 2023.<ref>{{cite web |url=https://podcasters.apple.com/4115-technical-updates-for-hosting-providers |title=Technical updates for hosting providers |publisher=Apple Inc |access-date=30 October 2024 | archive-url= https://web.archive.org/web/20240818221952/https://podcasters.apple.com/4115-technical-updates-for-hosting-providers | archive-date= 18 August 2024 | url-status= live}}</ref> and requires podcasts to be in RSS 2.0 format.<ref>{{cite web |url=https://podcasters.apple.com/support/823-podcast-requirements |title=Podcast RSS feed requirements |publisher=Apple Inc |access-date=30 October 2024 | archive-url=https://web.archive.org/web/20240921203020/https://podcasters.apple.com/support/823-podcast-requirements | archive-date= 21 September 2024 | url-status= live}}</ref> * Many sites choose to publish their feeds in only a single format. For example, [[CNN]] 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.<ref>{{cite journal |first=John R. |last=Quain |url=https://www.nytimes.com/ref/technology/circuits/03basi.html |title=Fine-Tuning Your Filter for Online Information |journal=New York Times |date=3 June 2004 |access-date=4 March 2017 |archive-date=15 December 2016 |archive-url=https://web.archive.org/web/20161215120947/http://www.nytimes.com/ref/technology/circuits/03basi.html |url-status=live }}</ref><ref>{{cite journal|first=Bob |last=Tedeschi |url=http://travel2.nytimes.com/2006/01/29/travel/29prac.html |title=There's a Popular New Code for Deals: RSS |journal=New York Times |date=29 January 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060717202415/http://travel2.nytimes.com/2006/01/29/travel/29prac.html |archive-date=17 July 2006 }}</ref>

==Development history==

===Background=== Before the creation of Atom the primary method of web content syndication was the RSS 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.<ref>{{Cite web|url=https://cyber.harvard.edu/rss/rss.html|title=RSS 2.0 Specification (RSS 2.0 at Harvard Law)|website=cyber.harvard.edu|access-date=14 June 2022|archive-date=5 June 2022|archive-url=https://web.archive.org/web/20220605193128/https://cyber.harvard.edu/rss/rss.html|url-status=live}}</ref>

===Initial work=== In June 2003, [[Sam Ruby]] set up a wiki to discuss what makes "a well-formed log entry".<ref>{{cite web |first=Sam |last=Ruby |url=http://www.intertwingly.net/blog/1472.html |title=Anatomy of a Well Formed Log Entry |date=16 June 2003 |access-date=28 August 2005 |archive-date=30 October 2012 |archive-url=https://web.archive.org/web/20121030042604/http://intertwingly.net/blog/1472.html |url-status=dead }}</ref> This initial posting acted as a rallying point.<ref>{{cite web |first=Tim |last=Bray |url=http://www.tbray.org/ongoing/When/200x/2003/06/23/SamsPie |title=I Like Pie |date=23 June 2003 |access-date=16 February 2006 |archive-date=7 February 2006 |archive-url=https://web.archive.org/web/20060207042238/http://www.tbray.org/ongoing/When/200x/2003/06/23/SamsPie |url-status=live }}</ref> People quickly started using the wiki to discuss a new syndication format to address the shortcomings of RSS. 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.com|Blogger]] API and [[LiveJournal]] [[XML-RPC]] Client/Server Protocol as well.

The project aimed to develop a web syndication format that was:<ref name="atom_roadmap">{{cite web |url=http://www.intertwingly.net/wiki/pie/RoadMap |title=Roadmap |work=Atom Wiki |access-date=4 December 2007 | archive-url= https://web.archive.org/web/20071211104213/http://www.intertwingly.net/wiki/pie/RoadMap| archive-date= 11 December 2007 | url-status= live}}</ref> * "100% vendor neutral," * "implemented by everybody," * "freely extensible by anybody, and" * "cleanly and thoroughly specified."

In short order, a project road map<ref name="atom_roadmap" /> was built. The effort quickly attracted more than 150 supporters, including [[David Sifry]] of [[Technorati]], [[Mena Trott]] of [[Six Apart]], [[Brad Fitzpatrick]] of LiveJournal, [[Jason Shellen]] of [[Blogger.com|Blogger]], [[Jeremy Zawodny]] of [[Yahoo!|Yahoo]], Timothy Appnel of the [[O'Reilly Media|O'Reilly Network]], Glenn Otis Brown of [[Creative Commons]] and [[Lawrence Lessig]]. Other notables supporting Atom include [[Mark Pilgrim (software developer)|Mark Pilgrim]], [[Tim Bray]], [[Aaron Swartz]], [[Joi Ito]], and Jack Park.<ref>{{cite web |url=http://www.intertwingly.net/wiki/pie/RoadMap#head-74b5d46318b48115b07ab1a2e77cb22df987c284 |title=Roadmap — Supporters |work=Atom Wiki |access-date=4 December 2007 | archive-url= https://web.archive.org/web/20071211104213/http://www.intertwingly.net/wiki/pie/RoadMap| archive-date= 11 December 2007 | url-status= live}}</ref> Also, [[Dave Winer]], the key figure behind RSS 2.0, gave tentative support to the new endeavor.<ref>{{cite web|first=Dave |last=Winer |url=http://backend.userland.com/2003/06/26 |title=Tentative endorsement of Echo |date=26 June 2003 |url-status=dead |archive-url=https://web.archive.org/web/20060208154438/http://backend.userland.com/2003/06/26 |archive-date=8 February 2006 }}</ref>

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)<ref>{{Cite web|url=http://www.tbray.org/ongoing/When/200x/2003/08/18/PieSchema02|title=ongoing by Tim Bray · Schemaware for PEAW 0.2|website=www.tbray.org|access-date=19 January 2009|archive-date=30 March 2009|archive-url=https://web.archive.org/web/20090330130445/http://www.tbray.org/ongoing/When/200x/2003/08/18/PieSchema02|url-status=live}}</ref> 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-related services, such as Blogger, [[Google News]], and [[Gmail]]. Google's Data APIs (Beta) [[GData]] 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]] or the [[Internet Engineering Task Force]] (IETF). The group eventually chose the IETF and the Atompub working group<ref>{{cite web|url=http://www.ietf.org/html.charters/atompub-charter.html |title=Atompub working group |url-status=dead |archive-url=https://web.archive.org/web/20071018010134/http://www.ietf.org/html.charters/atompub-charter.html |archive-date=18 October 2007 }}</ref> 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 (the co-editor of the XML specification) and [[Paul Hoffman (VPNC)|Paul Hoffman]]. Initial development was focused on the syndication format.

The '''Atom Syndication Format''' was issued as a Proposed Standard in IETF {{IETF RFC|4287}} in December 2005. The co-editors were Mark Nottingham and Robert Sayre. This document is known as ''atompub-format'' in IETF's terminology. The '''Atom Publishing Protocol''' was issued as a Proposed Standard in IETF {{IETF RFC|5023}} in October 2007. Two other drafts have not been standardized.<ref>{{cite web |author=Internet Engineering Task Force |url=http://tools.ietf.org/wg/atompub |title=Atompub Status Pages |access-date=4 December 2007 | archive-url= https://web.archive.org/web/20071217041539/http://tools.ietf.org/wg/atompub| archive-date= 17 December 2007 | url-status= live}}</ref>

==Example of an Atom 1.0 feed== An example of a document in the Atom Syndication Format: <syntaxhighlight lang="xml"><?xml version="1.0" encoding="utf-8"?>

<title>Example Feed</title> <subtitle>A subtitle.</subtitle> <link href="http://example.org/feed/" rel="self" /> <link href="http://example.org/" /> <id>urn:uuid:60a76c80-d399-11d9-b91C-0003939e0af6</id> <updated>2003-12-13T18:30:02Z</updated> <entry> <title>Atom-Powered Robots Run Amok</title> <link href="http://example.org/2003/12/13/atom03" /> <link rel="alternate" type="text/html" href="http://example.org/2003/12/13/atom03.html"/> <link rel="edit" href="http://example.org/2003/12/13/atom03/edit"/> <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id> <published>2003-11-09T17:23:02Z</published> <updated>2003-12-13T18:30:02Z</updated> <summary>Some text.</summary> <content type="xhtml"> <div xmlns="http://www.w3.org/1999/xhtml"> <p>This is the entry content.</p> </div> </content> <author> <name>John Doe</name> <email>johndoe@example.com</email> </author> </entry>

</feed></syntaxhighlight>

===Including in HTML=== The following tag should be placed into the head of an HTML document to provide a link to an Atom feed. <syntaxhighlight lang="html"> <link href="atom.xml" type="application/atom+xml" rel="alternate" title="Sitewide Atom feed" /> </syntaxhighlight>

== RSS compared with Atom == {{RSSvsATOM}}

==See also== *[[hAtom]] – [[microformat]] for marking up (X)HTML so that Atom feeds can be derived from it * [[Micropub (protocol)|Micropub]] – W3C standard client–server protocol that uses [[HTTP]] to create, update, and delete; a more recent alternative to AtomPub except using [[OAuth]] for authentication instead of HTTP Basic Authentication *[[Channel Definition Format]] – an early feed format developed before Atom and RSS *[[Content Management Interoperability Services]] – provides an extension to AtomPub for content management *[[List of content syndication markup languages]] *[[Open Data Protocol]] – a set of extensions to AtomPub developed by Microsoft * [[OPML]] to exchange lists of Atom feeds between feed readers *[[SWORD (protocol)]] *[[Web syndication]]

==References== {{Reflist|30em}}

==External links== *{{IETF RFC|4287}} – "The Atom Syndication Format" *{{IETF RFC|5023}} – "The Atom Publishing Protocol" *[http://www.intertwingly.net/wiki/pie/Rss20AndAtom10Compared Comparison of RSS and Atom Web Feed Formats] *[https://web.archive.org/web/20070301043011/http://www-128.ibm.com/developerworks/library/x-atompp1/ Getting to know the Atom Publishing Protocol] – IBM developerWorks article by James Snell *{{cite web|url=http://www.intertwingly.net/blog/1472.html|title=Anatomy of a Well Formed Log Entry – the weblog post that started it all|last=Ruby|first=Sam|date=16 June 2003|archive-url=https://web.archive.org/web/20200217120837/http://www.intertwingly.net/blog/1472.html|archive-date=17 February 2020}}

{{DEFAULTSORT:Atom (Standard)}} [[Category:Atom (web standard)| ]] [[Category:Cloud standards]] [[Category:Internet properties established in 2003]] [[Category:Open formats]] [[Category:RSS]] [[Category:Web syndication formats]] [[Category:XML-based standards]]