#pragma section-numbers off || [[TableOfContents]] || = RSS and Atom = People who generate syndication feeds have a choice of feed formats. As of mid-2005, the two most likely candidates will be [http://blogs.law.harvard.edu/tech/rss RSS 2.0] and [http://ietfreport.isoc.org/idref/draft-ietf-atompub-format/ Atom 1.0]. The purpose of this page is to summarize, as clearly and simply as possible, the differences between the RSS 2.0 and Atom 1.0 syndication languages. Toru Marumoto has produced [http://www.witha.jp/Atom/RSS-and-Atom.html a Japanese translation]. == Major/Qualitative Differences == === Deployment === 2005/07/21: RSS 2.0 is widely deployed and Atom 1.0 only by a few early adopters, see KnownAtomFeeds and KnownAtomConsumers. === Specifications === The RSS 2.0 specification is copyrighted by Harvard University and is frozen. No significant changes can be made and it is intended that future work be done under a different name; Atom is one example of such work. The Atom 1.0 specification (in the course of becoming an IETF standards track RFC) represents the consensus of the [http://www.ietf.org/html.charters/atompub-charter.html Atompub Working Group] within the [http://www.ietf.org/ IETF], as reviewed and approved by the IETF community and the [http://www.ietf.org/iesg.html Internet Engineering Steering Group]. The specification is structured in such a way that the IETF could conceivably issue further versions or revisions of this specification without breaking existing deployments, although there is no commitment, nor currently expressed interest, in doing so. See the Extensibility section below for how each can be extended without changing the specifications themselves. === Publishing Protocols === There are two popular protocols widely used with RSS, [http://www.xmlrpc.com/metaWeblogApi MetaWeblog] and [http://www.blogger.com/developers/api/ Blogger]. There are frequent [http://www.bblfish.net/blog/page7.html#2005/06/20/22-28-18-208 reports] of problems with interoperability and feature shortcomings. The Atompub working group is in the late stages of developing the [http://ietfreport.isoc.org/idref/draft-ietf-atompub-protocol/ Atom Publishing Protocol], which is closely integrated with the Atom feed format and is based on the experience with the existing protocols. === Required Content === RSS 2.0 requires feed-level title, link, and description. RSS 2.0 does not require that any of the fields of individual items in a feed be present. Atom 1.0 requires that both feeds and entries include a title (which may be empty), a unique identifier, and a last-updated timestamp. === Payload === RSS 2.0 may contain either plain text or escaped HTML, with no way to indicate which of the two is provided. Escaped HTML is ugly (for example, the string AT&T would be expressed as “AT&T”) and has been a source of difficulty for implementors. RSS 2.0 cannot contain actual well-formed XML markup, which reduces the re-usability of content. Atom has a carefully-designed payload container. Content may be explicitly labeled as any one of: * plain text, with no markup (the default) * escaped HTML, like is commonly used with RSS 2.0 * well-formed, displayable XHTML markup * some other XML vocabulary (There is no guarantee that the recipient will be able to do anything useful with such content) * base64-encoded binary content (again, no guarantee) * a pointer to Web content not included in the feed === Full or Partial Content === RSS 2.0 has a “description” element which is commonly used to contain either the full text of an entry or just a synopsis (sometimes in the same feed), and which sometimes is absent. There is no built-in way to signal whether the contents are complete. Atom has separate “summary” and “content” elements. The summary is encouraged for accessibility reasons if the content is non-textual (e.g. audio) or non-local (i.e. identified by pointer). === Autodiscovery === RSS [http://diveintomark.org/archives/2002/06/02/important_change_to_the_link_tag autodiscovery] has been implemented several times in different ways and has never been standardized. This is a common source of difficulty for non-technical users. Atom [http://www.ietf.org/internet-drafts/draft-ietf-atompub-autodiscovery-01.txt standardizes autodiscovery]. Additionally, Atom feeds contain a “self” pointer, so a newsreader can auto-subscribe given only the contents of the feed, based on Web-standard dispatching techniques. === Extraction and Aggregation === The only recognized form of RSS 2.0 is an document. Atom 1.0 allows standalone Atom Entry documents; these could be transferred using any network protocol, for example [http://ietfreport.isoc.org/idref/draft-saintandre-atompub-notify/ XMPP]. Atom also has support for aggregated feeds, where entries from multiple different feeds are combined, with pointers back to the feed they came from. == Differences of Degree == === Extensibility === RSS 2.0 is not in an XML namespace but may contain elements from other XML namespaces. There is no central place where one can find out about many popular extensions, such as dc:creator and content:encoded. Atom 1.0 is in [http://www.w3.org/2005/Atom an XML namespace] and may contain elements or attributes from other XML namespaces. There are specific guidelines on how to interpret extension elements. Additionally, there will be an IANA managed directory rel= values for . Finally, Atom 1.0 provides recommended extension points and guidance on how to interpret simple extensions. === URIs === RSS 2.0 does not specify the handling of relative URI references, and in practice they cannot be used in RSS feeds. Atom 1.0 specifies use of the XML's built-in [http://www.w3.org/TR/xmlbase/ xml:base] attribute for allowing the use of relative references. === Software Libraries (Parsing, Generating) === Both RSS 2.0 and Atom 1.0 feeds can be accessed via standard HTTP client libraries. Standard caching techniques work well and are encouraged. Template-driven creation of both formats is quite practical. Libraries for processing RSS 2.0: * [http://feedparser.org/ FeedParser] * [http://rome.dev.java.net/ Rome] Libraries for processing Atom 1.0: * [http://bulknews.typepad.com/blog/2005/07/searchcpanorg_t.html XML::Atom] === Language Tagging === For identification of the language used in feeds, RSS 2.0 has its own element, while Atom uses XML's built-in [http://www.w3.org/TR/REC-xml/#sec-lang-tag xml:lang] attribute. === Digital Signature/Encryption === RSS 2.0 can be encrypted or signed like any other web content, if treated as a bag of bits. Rules for applying standard [http://www.w3.org/TR/xmlenc-core/ XML Encryption] and [http://www.w3.org/TR/xmldsig-core/ XML Digital Signature] on entries are included in Atom 1.0. Alternatively, the feed can be encrypted or signed, like RSS 2.0, as a bag of bits. === Authors === RSS 2.0 provides the ability to specify email addresses for a feed’s “managingEditor” and “webMaster”, and for an item’s “author”. Some publishers prefer not to share email addresses, and use “dc:creator” from the dublin core extension instead. Atom 1.0 provides “author” and “contributor” elements at both the feed and entry level. These elements must contain a name, and also have optional email and URI sub-elements. === Categories === RSS 2.0 categories have two parts: label and domain. Atom 1.0 categories have three, with the addition of optional human-readable title. === Schema === The RSS 2.0 specification includes no schema. Atom 1.0 includes a (non-normative) ISO-Standard [http://relaxng.org/ RelaxNG] schema, to support those who want to check the validity of data advertised as Atom 1.0. Other schema formats can be [http://www.thaiopensource.com/relaxng/trang.html generated] from the RelaxNG schema. == Sample RSS and Atom Feeds == === RSS 2.0 (687 bytes) === {{{~cpp Example Feed Insert witty or insightful remark here http://example.org/ Sat, 13 Dec 2003 18:30:02 GMT johndoe@example.com (John Doe) Atom-Powered Robots Run Amok http://example.org/2003/12/13/atom03 urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a Sat, 13 Dec 2003 18:30:02 GMT Some text. }}} === Atom 1.0 (677 bytes) === {{{~cpp Example Feed Insert witty or insightful remark here 2003-12-13T18:30:02Z John Doe johndoe@example.com urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6 Atom-Powered Robots Run Amok urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2003-12-13T18:30:02Z Some text. }}} == Element Comparison Table == Atom 1.0 defines 21 elements; RSS 2.0, 30. Most of the RSS 2.0 elements missing in Atom 1.0 are either those that were never widely implemented in practice, or the capabilities are provided in other ways. ||'''RSS 2.0'''||'''Atom 1.0'''||'''Comments'''|| ||rss||-||Vestigial in RSS|| ||channel||feed|||| ||title||title|||| ||link||link||Atom defines an extensible family of "rel" values|| ||description||subtitle|||| ||language||-||Atom uses standard "xml:lang" attribute|| ||copyright||rights|||| ||webMaster||-|||| ||managingEditor||author or contributor|||| ||pubDate||published (in entry)||Atom has no feed-level equivalent|| ||lastBuildDate (in channel)||updated||RSS has no item-level equivalent|| ||category||category|||| ||generator||generator|||| ||docs||-|||| ||cloud||-|||| ||ttl||-||Use the Expires and max-age cache hints in HTTP 1.1|| ||image||logo||Atom recommends 2:1 aspect ratio|| ||-||icon||As in "favicon.ico"|| ||rating||-|||| ||textInput||-|||| ||skipHours||-|||| ||skipDays||-|||| ||item||entry|||| ||author||author|||| ||-||contributor|||| ||description||summary and/or content||depending on whether full content is provided|| ||comments||-|||| ||enclosure||-||rel="enclosure" on in Atom|| ||guid||id|||| ||source||-||rel="via" on in Atom|| ||-||source||Container for feed-level metadata to support aggregation|| == Related == See also: * [http://www.atomenabled.org/developers/syndication/ Atom Syndication Format - Introduction] * [http://www.tbray.org/ongoing/When/200x/2005/07/27/Atomic-RSS Atomic RSS] * [http://www.intertwingly.net/slides/2003/rssQuickSummary.html RSS Quick Summary] ---- [기술분류]