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Network Working Group M. Nottingham, Ed. Internet-Draft July8,17, 2004 Expires: January6,15, 2005 The Atom Syndication Formatdraft-ietf-atompub-format-00draft-ietf-atompub-format-01 Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January6,15, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This specification describes Atom, an XML-based Web content and metadata syndication format. Nottingham Expires January6,15, 2005 [Page 1] Internet-Draft Atom Format July 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . ..4 1.1 Editorial Notes . . . . . . . . . . . . . . . . . . . . . 4 1.2 Example . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3 Conformance . . . . . . . . . . . . . . . . . . . . . . . 5 1.4 Notational Conventions . . . . . . . . . . . . . . . . . . 5 2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . .. 67 3. Common Atom Constructs . . . . . . . . . . . . . . . . . . .. 79 3.1 Content Constructs . . . . . . . . . . . . . . . . . . . .79 3.1.1 "type" Attribute . . . . . . . . . . . . . . . . . . .79 3.1.2 "mode" Attribute . . . . . . . . . . . . . . . . . . .79 3.2 Person Constructs . . . . . . . . . . . . . . . . . . . .79 3.2.1 "atom:name" Element . . . . . . . . . . . . . . . . .710 3.2.2"atom:url""atom:uri" Element . . . . . . . . . . . . . . . . . .810 3.2.3 "atom:email" Element . . . . . . . . . . . . . . . . .810 3.3 Date Constructs . . . . . . . . . . . . . . . . . . . . .810 3.4 Link Constructs . . . . . . . . . . . . . . . . . . . . .810 3.4.1 "rel" Attribute . . . . . . . . . . . . . . . . . . .810 3.4.2 "type" Attribute . . . . . . . . . . . . . . . . . . .811 3.4.3 "href" Attribute . . . . . . . . . . . . . . . . . . .911 3.4.4 "hreflang" Attribute . . . . . . . . . . . . . . . . .911 3.4.5 "title" Attribute . . . . . . . . . . . . . . . . . .911 4. The "atom:feed" Element . . . . . . . . . . . . . . . . . .. 912 4.1 "version" Attribute . . . . . . . . . . . . . . . . . . .912 4.2"xml:lang" Attribute . .The "atom:head" Element . . . . . . . . . . . . . . . . .10 4.312 4.2.1 "atom:title" Element . . . . . . . . . . . . . . . . .. . 10 4.412 4.2.2 "atom:link" Element . . . . . . . . . . . . . . . . .. . 10 4.512 4.2.3 "atom:author" Element . . . . . . . . . . . . . . . .. . 10 4.613 4.2.4 "atom:contributor" Element . . . . . . . . . . . . . .. . 10 4.713 4.2.5 "atom:tagline" Element . . . . . . . . . . . . . . . .. . 10 4.813 4.2.6 "atom:id" Element . . . . . . . . . . . . . . . . . .. . 11 4.913 4.2.7 "atom:generator" Element . . . . . . . . . . . . . . .. . 11 4.1013 4.2.8 "atom:copyright" Element . . . . . . . . . . . . . . .. . 11 4.1114 4.2.9 "atom:info" Element . . . . . . . . . . . . . . . . .. . 12 4.1214 4.2.10 "atom:modified" Element . . . . . . . . . . . . . .. . . 12 4.1314 5. The "atom:entry" Element . . . . . . . . . . . . . . . . . .. 12 4.13.115 5.1 "atom:title" Element . . . . . . . . . . . . . . . . .13 4.13.2. . 15 5.2 "atom:link" Element . . . . . . . . . . . . . . . . .13 4.13.3. . 15 5.3 "atom:author" Element . . . . . . . . . . . . . . . .13 4.13.4. . 15 5.4 "atom:contributor" Element . . . . . . . . . . . . . .13 4.13.5. . 16 5.5 "atom:id" Element . . . . . . . . . . . . . . . . . .13 4.13.6. . 16 5.6 "atom:modified" Element . . . . . . . . . . . . . . .14 4.13.7. . 16 5.7 "atom:issued" Element . . . . . . . . . . . . . . . .14 4.13.8. . 16 5.8 "atom:created" Element . . . . . . . . . . . . . . . .14 4.13.9. . 16 5.9 "atom:summary" Element . . . . . . . . . . . . . . . .14 4.13.10. . 17 5.10 "atom:content" Element . . . . . . . . . . . . . . .14 4.13.11. . 17 5.11 "atom:copyright" Element . . . . . . . . . . . . . .15. . 17 Nottingham Expires January6,15, 2005 [Page 2] Internet-Draft Atom Format July 20045.5.12 "atom:origin" Element . . . . . . . . . . . . . . . . . 17 6. Managing Feed State . . . . . . . . . . . . . . . . . . . .. 15 6.19 7. Embedding Atom in Other Formats . . . . . . . . . . . . . .. 15 7.20 8. Extending Atom . . . . . . . . . . . . . . . . . . . . . . .. 15 8.21 9. IANA Considerations . . . . . . . . . . . . . . . . . . . .. 15 9.22 10. Security Considerations . . . . . . . . . . . . . . . . . .. 16 10.23 11. Normative References . . . . . . . . . . . . . . . . . . . .1623 Author's Address . . . . . . . . . . . . . . . . . . . . . .. 1724 A. Contributors . . . . . . . . . . . . . . . . . . . . . . . .. 1725 B. Revision History . . . . . . . . . . . . . . . . . . . . . .. 1726 Intellectual Property and Copyright Statements . . . . . . .. 1927 Nottingham Expires January6,15, 2005 [Page 3] Internet-Draft Atom Format July 2004 1. Introduction Atom is an XML-basedfiledocument format intended to allow lists of related information, known as "feeds", to be synchronised between publishers and consumers. Feeds are composed of a number of items, known as "entries", each with an extensible set of attached metadata. For example, each entry has a title. The primary use case that Atom addresses is the syndication of Web content such as Weblogs and news headlines, to Web sites as well as directly toconsumers.user agents. However, nothing precludes it from being used for other purposes and kinds of content. Details of comunication protocols between software agents using Atom can be found in the Atom Protocol specification [Atom-protocol]. [[ more motivation / design principles ]] 1.1 Editorial Notes The Atom format is a work-in-progress, and this draft is both incomplete and likely to change rapidly. As a result, THE FORMAT DESCRIBED BY THIS DRAFT SHOULD NOT BE DEPLOYED, either in production systems or in any non-experimental fashion on the Internet. Discussion of this draft happens in two fora; The mailing list [1] The Atom Wiki Web site [2] Active development takes place on the mailing list, while the Wiki is used for issue tracking and new proposals. This document is an early draft and known to be incomplete. Topics marked [[like this]] indicate where additional text is likely to be added. Nottingham Expires January6,15, 2005 [Page 4] Internet-Draft Atom Format July 2004 1.2 Example A minimal, single-entry Atomfeed serialized as XML 1.0:Feed Document: <?xml version="1.0" encoding="utf-8"?> <feedversion="draft-ietf-atompub-format-00.txt:version="draft-ietf-atompub-format-01: do not deploy"xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-00"> <title>Example</title>xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-01"> <head> <title>Example Feed</title> <link rel="alternate" type="text/html"href="http://example.org/"/>href="http://example.org/index.atom"/> <modified>2003-12-13T18:30:02Z</modified> <author> <name>John Doe</name> </author> </head> <entry><title>Atom 0.3 snapshot</title><title>Atom-Powered Robots Run Amok</title> <link rel="alternate" type="text/html" href="http://example.org/2003/12/13/atom03"/> <id>tag:example.org,2003:3.2397</id> <issued>2003-12-13T08:29:29-04:00</issued> <modified>2003-12-13T18:30:02Z</modified> </entry> </feed> 1.3 Conformance [[ talk about atom documents and atom consumers, and how requirements are placed on them ]] 1.4 Notational Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. This specification uses XML Namespaces [W3C.REC-xml-names-19990114] to uniquely identify XML elements and attribute names. It uses the following namespace prefixes for the indicated namespace URIs; "atom":http://purl.org/atom/ns#draft-ietf-atompub-format-00http://purl.org/atom/ns#draft-ietf-atompub-format-01 Note that the choice of any namespace prefix is arbitrary and not semantically significant. Atom is specified using terms from the XML Infoset Nottingham Expires January 15, 2005 [Page 5] Internet-Draft Atom Format July 2004 [W3C.REC-xml-infoset-20011024]. However, this specification uses a shorthand for two common terms; the phrase "Information Item" isnot used Nottingham Expires January 6, 2005 [Page 5] Internet-Draft Atom Format July 2004omitted when namingXML constructs.Element Information Items and Attribute Information Items. Therefore, when this specification uses the term "element," it is refering to an Element Information Item in Infoset terms. Likewise, when it uses the term "attribute," it is refering to an Attribute Information Item. Nottingham Expires January 15, 2005 [Page 6] Internet-Draft Atom Format July 2004 2. Atom Documents This specification describes two kinds of Atom Documents; Atom Feed Documents and Atom Entry Documents. An AtomdocumentFeed Document is a representation of anXML document whose document elementAtom feed, including metadata about the feed, and some or all of the entries associated with it. Its document element is atom:feed. An Atom Entry Document represents exactly one Atom Entry, outside of theatom:feed element, as described below.context of an Atom Feed. Its document element is atom:entry. Both kinds of Atom documents are specified in terms of the XML Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204] and identified with the "application/atom+xml" media type. Atomdocuments MAY have a Document Type Declaration. [[Entities]]Documents MUST be well-formed XML. [[ Validity? ]] Atomdocuments SHOULD NOT contain Processing Instructions, unless they are a commonly used convention outsideconstrains thescopeappearance and content of elements and attributes; unless otherwise stated, Atom(e.g., the PI for XSLT processing). Atom documentsDocuments MAY containComments. All elementsother Information Items as appropriate. In particular, Comment Information Items andattributes in an Atom document MUSTProcessing Instruction Information Items SHOULD benamespace-qualified. Note that this requirement does not precludeignored in theusenormal processing ofa default namespace.an Atom Document. Any element in an AtomdocumentDocument MAY have an xml:base attribute. XML Base [W3C.REC-xmlbase-20010627] processing MUST be applied to any relative URI reference present in an Atom document. This includes such elements and attributes as specified by Atom itself, as well as those specified by extensions to Atom. Any element in an AtomdocumentDocument MAY have an xml:lang attribute, whose content indicates the default natural language of the element's content. Requirements regarding the content and interpretation of xml:lang are specified in XML 1.0 [W3C.REC-xml-20040204] Section 2.12. For convenience, the most important are summarised here: The content of this attributeMUSTmust be a language tag[RFC3066]. When determining[RFC3066] or an empty string (e.g., xml:lang=""), which indicates that there is no language information available. If an elementcontent's natural language,does not have an xml:lang element, the first xml:lang attributeencounteredinthat element'sits ancestorsMUSTindicates the natural language of its content. [[ feedback as to whether this listing is helpful or not would beused.appreciated; re-stating the requirements of other specifications is tricky. ]] Nottingham Expires January 15, 2005 [Page 7] Internet-Draft Atom Format July 2004 [[ discussion of URI escaping and i18n ]] [[ discussion of white space ]] Atom is extensible. See the section titled 'Extending Atom' later in this document for a full description of howextensionsAtom Documents can bemade to the format.extended. Nottingham Expires January6,15, 2005 [Page6]8] Internet-Draft Atom Format July 2004 3. Common Atom Constructs Many of Atom's elements share a few commonstructure.structures. This section defines a few such structures and their requirements, for convenient reference by the appropriate element definitions. When an element is identified as being a particular kind of construct, it inherits the corresponding requirements from that construct's definition in this section. 3.1 Content Constructs A Content construct is an element with arbitrary child content, whose properties are described by the following attributes: 3.1.1 "type" Attribute Content constructs MAY have a "type" attribute, whose value indicates the media type of the content. When present, this attribute's value MUST be aregisteredmedia type [RFC2045]. If this attribute is not present,its valueprocessors MUSTbe considered to be "text/plain".behave as if it were present with a value of "text/ plain". 3.1.2 "mode" Attribute Content constructs MAY have a "mode" attribute, whose value indicates the method used to encode the content. When present, this attribute's value MUST be listed below. If not present, its value MUST be considered to be "xml". "xml": A mode attribute with the value "xml" indicates that the element's content is inline xml (for example, namespace-qualified XHTML). "escaped": A mode attribute with the value "escaped" indicates that the element's content isan escaped string.escaped, as defined in [W3C.REC-xml-20040204] (section 4.6). Processors MUST unescape the element's content before considering it as content of the indicated media type. "base64": A mode attribute with the value "base64" indicates that the element's content is base64-encoded [RFC2045]. Processors MUST decode the element's content before considering it as content of the the indicated media type. 3.2 Person Constructs A Person construct is an elementwiththat describes a person, corporation, or similar entity. It has the following children: Nottingham Expires January 15, 2005 [Page 9] Internet-Draft Atom Format July 2004 3.2.1 "atom:name" Element The "atom:name" element's content conveys a human-readable name forNottingham Expires January 6, 2005 [Page 7] Internet-Draft Atom Format July 2004 the author. It MAY bethename of a corporation or other entity no individual authors can be named.person. Person constructs MUST contain exactly one "atom:name" element, whose contentMUST be a string.is unstructured text. 3.2.2"atom:url""atom:uri" Element The"atom:url""atom:uri" element's content conveys a URI associated with theauthor.person. Person constructs MAY contain anatom:urlatom:uri element, but MUST NOT contain more than one. The content ofatom:urlatom:uri in a Person construct MUST be a URI [RFC2396]. xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to theatom:urlatom:uri element's content. 3.2.3 "atom:email" Element The "atom:email" element's content conveys an e-mail address associated with thePerson construct.persons. Person constructs MAY contain an atom:email element, but MUST NOT contain more than one. Its content MUST be an e-mail address [RFC2822]. Person constructs MAY be extended by namespace-qualified element children. Ordering of the element children of Person constructs MUST NOT be considered significant. 3.3 Date Constructs A Date construct is an element whosechildcontent is a W3C Date-Time string [W3C.NOTE-datetime-19980827]. 3.4 Link Constructs A Link construct is an element that MUST NOT have any child content, and has the following attributes: 3.4.1 "rel" Attribute The "rel" attribute indicates the type of relationship that the link represents. Link constructs MUST have a rel attribute, whose value MUST bea string, and MUST beone of the values enumerated in the Atom Protocol specification [Atom-protocol]. Nottingham Expires January 15, 2005 [Page 10] Internet-Draft Atom Format July 2004 3.4.2 "type" Attribute The "type" attribute indicates an advisory media type; it MAY be used as a hint to determine the type of the representation which should be returned when the URI in the href attribute is dereferenced. Note that the type attribute does not override the actual media type returned with the representation.Nottingham Expires January 6, 2005 [Page 8] Internet-Draft Atom Format July 2004Link constructs MUST have a type attribute, whose value MUST be aregisteredmedia type [RFC2045]. 3.4.3 "href" Attribute The "href" attribute contains the link's URI. Link constructs MUST have a href attribute, whose value MUST be a URI [RFC2396]. xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the href attribute's content. 3.4.4 "hreflang" Attribute The "hreflang" attribute's content describes the language of the resource pointed to by the href attribute. When used together with the rel="alternate", it implies a translated version of the entry. Link constructs MAY have an hreflang attribute, whose value MUST be a language tag [RFC3066]. 3.4.5 "title" Attribute The "title" attribute conveys human-readable information about the link. Link constructs MAY have a title attribute, whose valueMUST be a string.is unstructured text. Nottingham Expires January 15, 2005 [Page 11] Internet-Draft Atom Format July 2004 4. The "atom:feed" Element The "atom:feed" element is the document (i.e., top-level) element ofthe format described by this specification. Its children arean Atom Feed Document, acting as a(potentially partial) representation of the state ofcontainer for metadata and data associated with the feed.The atom:feed element MAY contain any namespace-qualified [W3C.REC-xml-names-19990114] elements as children. Ordering of the element children of atom:feedIts first element child MUSTNOTbeconsidered significant. The following attributes andatom:head, which MAY be followed zero or more atom:entry childelements are defined by this specification (note that it requires the presence of some of these elements):elements. 4.1 "version" Attribute atom:feed elements MUST have a "version" attribute whose content indicates the version of the Atom specification that theconstruct conforms to. The content of this attribute is unstructured text. The version identifier for this specification is "draft-ietf-atompub-format-00: do not deploy". Nottingham Expires January 6, 2005 [Page 9] Internet-Draft Atom Format July 2004 4.2 "xml:lang" Attribute atom:feed elements SHOULD have an "xml:lang" attribute whose content indicates the default natural language of the feed.feed conforms to. The content of this attribute is unstructured text. The version identifier for this specification is "draft-ietf-atompub-format-01: do not deploy". 4.2 The "atom:head" Element The atom:head element acts as a container for metadata about the feed itself. The atom:head element MAY contain any namespace-qualified [W3C.REC-xml-names-19990114] elements as children. Ordering of the element children of atom:head element MUST NOT bea language tag [RFC3066]. 4.3considered significant. The following child elements are defined by this specification (note that the presence of some of these elements is required): 4.2.1 "atom:title" Element The "atom:title" element is a Content construct that conveys a human-readable title for the feed.atom:feedatom:head elements MUST contain exactly one atom:title element.If the feed describes a Web resource, its content SHOULD be the same as that resource's title. 4.44.2.2 "atom:link" Element The "atom:link" element is a Link construct that conveys a URI associated with the feed. The nature of the relationship as well as the link itself is determined by the element's content.atom:feedatom:head elements MUST contain at least one atom:link element with a rel attribute value of "alternate".atom:feedatom:head elements MUST NOT contain more than one atom:link element with a rel attribute value of "alternate" that has the same type attribute value.atom:feedNottingham Expires January 15, 2005 [Page 12] Internet-Draft Atom Format July 2004 atom:head elements MAY contain additional atom:link elements beyond those described above.4.54.2.3 "atom:author" Element The "atom:author" element is a Person construct that indicates the default author of the feed.atom:feedatom:head elements MUST contain exactly one atom:author element, UNLESS all of the atom:feed element's child atom:entry elements contain an atom:author element.atom:feedatom:head elements MUST NOT contain more than one atom:author element. [[explain inheritence]]4.64.2.4 "atom:contributor" Element The "atom:contributor" element is a Person construct that indicates a person or other entity who contributes to the feed.atom:feedatom:head elements MAY contain one or more atom:contributor elements.4.74.2.5 "atom:tagline" Element The "atom:tagline" element is a Content construct that conveys aNottingham Expires January 6, 2005 [Page 10] Internet-Draft Atom Format July 2004human-readable description or tagline for the feed.atom:feedatom:head elements MAY contain an atom:tagline element, but MUST NOT contain more than one.4.84.2.6 "atom:id" Element The "atom:id" element's content conveys a permanent, globally unique identifier for the feed. It MUST NOT change over time, even if the feed is relocated.atom:feedatom:head elements MAY contain an atom:id element, but MUST NOT contain more than one. The content of this element, when present, MUST be a URI. xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the atom:id element's content.4.94.2.7 "atom:generator" Element The "atom:generator" element's content indentifies the software agent used to generate the feed, for debugging and other purposes.atom:feedatom:head elements MAY contain an atom:generator element, but MUST NOT contain more than one. The content of this element, when present, MUST be a string that is a human-readable name for the generating agent. The atom:generator element MAY have a"url""uri" attribute whose value Nottingham Expires January 15, 2005 [Page 13] Internet-Draft Atom Format July 2004 MUST be a URI. When dereferenced, that URI SHOULD produce a representation that is relevant to that agent. The atom:generator element MAY have a "version" attribute that indicates the version of the generating agent. When present, its valueMUST be a string. 4.10is unstructured text. 4.2.8 "atom:copyright" Element The "atom:copyright" element is Content construct that conveys a human-readable copyright statement for the feed.atom:feedatom:head elements MAY contain an atom:copyright element, but MUST NOT contain more than one. The atom:copyright element SHOULD NOT be used to convey machine-readable licensing information. The atom:copyright element may be assumed to apply to all entries contained by the feed except those entries which contain atom:copyright elements. The atom:copyright element MUST, if present, be considered to apply to the feed as a collection of entries.Nottingham Expires January 6, 2005 [Page 11] Internet-Draft Atom Format July 2004 4.114.2.9 "atom:info" Element The "atom:info" element is a Content construct that conveys a human-readable explanation of the feed format itself.atom:feedatom:head elements MAY contain an atom:info element, but MUST NOT contain more than one. The atom:info element SHOULD NOT considered meaningful by processors; it is a convenience to publishers in certain situations.4.124.2.10 "atom:modified" Element The "atom:modified" element is a Date construct that indicates the time when the state of the feed was last modified, including any changes to entries therein.atom:feedatom:head elements MUST contain exactly one atom:modified element. The content of an atom:modified element SHOULD have a time zone whose value MUST be "UTC".4.13Nottingham Expires January 15, 2005 [Page 14] Internet-Draft Atom Format July 2004 5. The "atom:entry" Element The "atom:entry" element represents an individualentry that is contained by the feed. atom:feed elements MAY contain one or more atom:entry elements. atom:entry elements MAY have an "xml:lang" attribute whose content indicates the default natural language of theentry.If the language of the atom:entry is different from the languageThis element can appear as a child of thefeed thenatom:feed element, or it can appear as theatom:entry SHOULD have an "xml:lang" attribute. The content of this attributedocument (i.e., top-level) elementMUST beof alanguage tag [RFC3066] or an empty string (e.g., xml:lang=""), which indicates that there is no language information available. If used alone,standalone Atom Entry Document. When appearing in an Atom Entry Document, atom:entry elements MUST have a "version" attribute whose content indicates the version of the Atom specification that theconstructentry conforms to. The version identifier for this specification is "draft-ietf-atompub-format-01: do not deploy". The atom:entry element MAY contain any namespace-qualified [W3C.REC-xml-names-19990114] elements as children. Ordering of the element children of atom:entry element MUST NOT be considered significant. The following child elements are defined by this specification (note that it requires the presence of some of these elements):Nottingham Expires January 6, 2005 [Page 12] Internet-Draft Atom Format July 2004 4.13.15.1 "atom:title" Element The "atom:title" element is a Content construct that conveys a human-readable title for the entry. atom:entry elements MUST have exactly one "atom:title" element.If an entry describes a Web resource, its content SHOULD be the same as that resource's title. 4.13.25.2 "atom:link" Element The "atom:link" element is a Link construct that conveys a URI associated with the entry. The nature of the relationship as well as the link itself is determined by the element's content. atom:entry elements MUST contain at least one atom:link element with a rel attribute value of "alternate". atom:entry elements MUST NOT contain more than one atom:link element with a rel attribute value of "alternate" that has the same type attribute value. atom:entry elements MAY contain additional atom:link elements beyond those described above.4.13.35.3 "atom:author" Element The "atom:author" element is a Person construct that indicates the default author of the entry. atom:entry elements MUST contain Nottingham Expires January 15, 2005 [Page 15] Internet-Draft Atom Format July 2004 exactly one atom:author element,UNLESSunless, in an Atom Feed Document, theatom:feedatom:head elementcontaining themcontains an atom:author element itself. atom:entry elements MUST NOT contain more than one atom:author element.[[explain inheritence]] 4.13.45.4 "atom:contributor" Element The "atom:contributor" element is a Person construct that indicates a person or other entity who contributes to the entry. atom:entry elements MAY contain one or more atom:contributor elements.4.13.55.5 "atom:id" Element The "atom:id" element's content conveys a permanent, globally unique identifier for the entry. It MUST NOT change over time, even if other representations of the entry (such as a web representation pointed to by the entry's atom:link element) are relocated.IfFor a given entry, thesame entry is syndicated in two atom:feedsatom:id element's content MUST be stable across all Atom Documents published by the sameentity, the entry'sentity. atom:entry MUST contain exactly one atom:id element. The content of this element MUST bethe same in both feeds. Nottingham Expires January 6, 2005 [Page 13] Internet-Draft Atom Format July 2004 4.13.6a URI. 5.6 "atom:modified" Element The "atom:modified" element is a Date construct that indicates the time that the entry was last modified. atom:entry elements MUST contain an atom:modified element, but MUST NOT contain more than one. The content of an atom:modified element MUST have a time zone whose value SHOULD be "UTC".4.13.75.7 "atom:issued" Element The "atom:issued" element is a Date construct that indicates the time that the entry was issued. atom:entry elements MUST contain an atom:issued element, but MUST NOT contain more than one. The content of an atom:issued element MAY omit a time zone.4.13.85.8 "atom:created" Element The "atom:created" element is a Date construct that indicates the time that the entry was created. atom:entry elements MAY contain an atom:created element, but MUST NOT contain more than one. The content of an atom:created element MUST have a time zone whose Nottingham Expires January 15, 2005 [Page 16] Internet-Draft Atom Format July 2004 value SHOULD be "UTC". If atom:created is not present, its content MUST considered to be the same as that of atom:modified.4.13.95.9 "atom:summary" Element The "atom:summary" element is a Content construct that conveys a short summary, abstract or excerpt of the entry. atom:entry elements MAY contain anatom:createdatom:summary element, but MUST NOT contain more than one.4.13.105.10 "atom:content" Element The "atom:content" element is a Content construct that conveys the content of the entry. atom:entry elements MAY contain one or more atom:content elements. If @type="multipart/alternative", @mode MUST NOT be specified, and content element MUST contain 1 or more content elements. These content elements MUST NOT specify @type="multipart/alternative" (i.e. only one level of nesting is allowed). Consumers SHOULD look at all alternative content elements and determine which one is most suitable, based on which @type and @mode the consumer supports, andNottingham Expires January 6, 2005 [Page 14] Internet-Draft Atom Format July 2004preferences specified by the end user (if any). Consumers SHOULD NOT render more than one content alternative.4.13.115.11 "atom:copyright" Element The "atom:copyright" element is a Content construct that conveys a human-readable copyright statement for the entry. atom:entry elements MAY contain anatom:copyrightatom:copyright element, but MUST NOT contain more than one. The atom:copyright element SHOULD NOT be used to convey machine-readable licensing information. If an atom:entry element does not contain an atom:copyright element, then the atom:copyright element of the containing atom:feed element's atom:head element, if present, should be considered to apply to the entry. 5.12 "atom:origin" Element The "atom:origin" element's content conveys the original source of the entry; e.g., the feed where the entry was first published. If the source is an Atom Feed Document, then the content of Nottingham Expires January 15, 2005 [Page 17] Internet-Draft Atom Format July 2004 atom:origin MUST be the same, character-for-character, as that of the href attribute of the atom:link element that has a rel attribute value of "alternate" in that document's atom:head section (i.e., the XPath expression "/atom:feed/atom:head/atom:link[@rel='alternate']/ @href"). The content of this element MUST be a URI. atom:entry elements MAY contain an atom:origin element, but MUST NOT contain more than one.The atom:copyright element SHOULD NOT be used to convey machine-readable licensing information. If an atom:entry element does not contain an atom:copyright element, then the atom:copyright element of the containing atom:feed, if present, should be considered to apply to the atom:entry. 5.Nottingham Expires January 15, 2005 [Page 18] Internet-Draft Atom Format July 2004 6. Managing Feed State [[ talk about what it means to keep a view of a feed ]]6.Nottingham Expires January 15, 2005 [Page 19] Internet-Draft Atom Format July 2004 7. Embedding Atom in Other Formats [[ ... ]]7.Nottingham Expires January 15, 2005 [Page 20] Internet-Draft Atom Format July 2004 8. Extending Atom [[ ... ]]8.Nottingham Expires January 15, 2005 [Page 21] Internet-Draft Atom Format July 2004 9. IANA ConsiderationsTheAn Atomformat,Document, when serialized as XML 1.0, can be identified with the following media type: MIME media type name: application MIME subtype name: atom+xml Mandatory parameters: None. Optional parameters: "charset": This parameter has identical semantics to the charset parameter of the "application/xml" media type as specified in RFC 3023 [RFC3023]. [RFC3023]. Encoding considerations: Identical to those of "application/xml" as described in RFC 3023 [RFC3023], section 3.2. Security considerations: As defined in this specification. [[update upon publication]]Nottingham Expires January 6, 2005 [Page 15] Internet-Draft Atom Format July 2004In addition, as this media type uses the "+xml" convention, it shares the same security considerations as described in RFC 3023 [RFC3023], section 10. Interoperability considerations: There are no known interoperability issues. Published specification: This specification. [[update upon publication]] Applications which use this media type: No known applications currently use this media type. Additional information: Magic number(s): As specified for "application/xml" in RFC 3023 [RFC3023], section 3.2. File extension: .atom Fragment identifiers: As specified for "application/xml" in RFC 3023 [RFC3023], section 5. Base URI: As specified in RFC 3023 [RFC3023], section 6. Macintosh File Type code: TEXT Person and email address to contact for further information: Mark Nottingham <mnot@pobox.com> Intended usage: COMMON Author/Change controller: This specification's author(s). [[update upon publication]]9.Nottingham Expires January 15, 2005 [Page 22] Internet-Draft Atom Format July 2004 10. Security Considerations [[ this is required ]]1011 Normative References [Atom-protocol] Gregorio, J. and R. Sayre, "The Atom Publishing Protocol", work-in-progress, July 2004. [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April 2001.Nottingham Expires January 6, 2005 [Page 16] Internet-Draft Atom Format July 2004[RFC3023] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001. [RFC3066] Alvestrand, H., "Tags for the Identification of Languages", BCP 47, RFC 3066, January 2001. [W3C.NOTE-datetime-19980827] Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C NOTE NOTE-datetime-19980827, August 1998. [W3C.REC-xml-20040204] Yergeau, F., Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (Third Edition)", W3C REC REC-xml-20040204, February 2004. [W3C.REC-xml-infoset-20011024] Cowan, J. and R. Tobin, "XML Information Set", W3C REC REC-xml-infoset-20011024, October 2001. [W3C.REC-xml-names-19990114] Bray, T., Hollander, D. and A. Layman, "Namespaces in XML", W3C REC REC-xml-names-19990114, January 1999. [W3C.REC-xmlbase-20010627] Nottingham Expires January 15, 2005 [Page 23] Internet-Draft Atom Format July 2004 Marsh, J., "XML Base", W3C REC REC-xmlbase-20010627, June 2001. [1] <http://www.imc.org/atom-syntax/index.html> [2] <http://www.intertwingly.net/wiki/pie/FrontPage> Author's Address Mark Nottingham (editor) EMail: mnot@pobox.com URI: http://www.mnot.net/ Nottingham Expires January 15, 2005 [Page 24] Internet-Draft Atom Format July 2004 Appendix A. Contributors The following people contributed to preliminary drafts of this document: Tim Bray, Mark Pilgrim, and Sam Ruby. The content and concepts within are a product of the Atom community and the Atom Publishing Format and Protocol Working Group. Nottingham Expires January 15, 2005 [Page 25] Internet-Draft Atom Format July 2004 Appendix B. Revision History [[ this section should be removed before final publication. ]]Nottingham Expires January 6, 2005 [Page 17] Internet-Draft Atom Format July 2004 2004-07-06 (-00):-01: Constrained omission of "Information Item" to just elements and attributes. Clarified xml:lang inheritence. Removed entry- and feed-specific langauge about xml:lang (covered by general discussion of xml:lang) Changed xml:lang to reference XML for normative requirements. Changed "... MUST be a string" to "... is unstructued text." Remomved langauge about DOCTYPEs, PIs, Comments, Entities. Changed atom:url to atom:uri, @url to @uri Introduced atom:head Introduced "Atom Feed Document" and "Atom Entry Document". Removed requirement for all elements and attributes to be namespace-qualified; now children of selective elements Added extensibility to Person constructs. Removed requirement for media types to be registered (non-registered media types are legal) Added atom:origin (PaceEntryOrigin) Added requirement for entry/id to be present and a URI (PaceEntryIdRequired). Clarified approach to Comments, PIs and well-formedness, as per RFC3470. Referenced escaping algorithm in XML. Assorted editorial nits and cleanup, refactoring -00: Initial IETF Internet-Draft submission. Added optional version attribute to entry (PaceEntryElementNeedsVersionAttribute). Added hreflang attribute (PaceHrefLang). Clarified inheritence of copyright element (PaceItemCopyright). Added xml:lang to entries (PaceItemLang). Tweaked Infoset-related language (PaceNoInfoSet). Clarified lack of structure in version attribute (PaceVersionAsText). Changed approach to XML Base (PaceXmlBaseEverywhere). Added XML Base processing to atom:id (PaceXmlBaseId). Various editorial cleanup and adjustments for IETF publication. Nottingham Expires January6,15, 2005 [Page18]26] Internet-Draft Atom Format July 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Nottingham Expires January6,15, 2005 [Page19]27] ----