Internet-Draft September 5, 2004 Expires: March 6, The Atom Syndication Format draft-ietf-atompub-format-02. Status of this Memo

Transcription

1 Network Working Group M. Nottingham, Ed. Internet-Draft September 5, 2004 Expires: March 6, 2005 Status of this Memo The Atom Syndication Format draft-ietf-atompub-format-02 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 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 The list of Internet-Draft Shadow Directories can be accessed at This Internet-Draft will expire on March 6, Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document specifies Atom, an XML-based Web content and metadata syndication format. Nottingham Expires March 6, 2005 [Page 1]

2 Table of Contents 1. Introduction Editorial Notes Example Conformance Notational Conventions Atom Documents Common Atom Constructs Content Constructs "type" Attribute "mode" Attribute Person Constructs "atom:name" Element "atom:uri" Element "atom: " Element Date Constructs Link Constructs "rel" Attribute "type" Attribute "href" Attribute "hreflang" Attribute "title" Attribute Identity Constructs Dereferencing Identity Constructs Comparing Identity Constructs The "atom:feed" Element "version" Attribute The "atom:head" Element "atom:title" Element "atom:link" Element "atom:author" Element "atom:contributor" Element "atom:tagline" Element "atom:id" Element "atom:generator" Element "atom:copyright" Element "atom:info" Element "atom:modified" Element The "atom:entry" Element "atom:title" Element "atom:link" Element "atom:author" Element "atom:contributor" Element "atom:id" Element "atom:updated" Element "atom:summary" Element "atom:content" Element Nottingham Expires March 6, 2005 [Page 2]

3 5.9 "atom:copyright" Element "atom:origin" Element Managing Feed State Securing Atom Documents Digital Signatures Encryption Embedding Atom in Other Formats Extending Atom IANA Considerations Security Considerations Normative References Author s Address A. Contributors B. Revision History Intellectual Property and Copyright Statements Nottingham Expires March 6, 2005 [Page 3]

4 1. Introduction Atom is an XML-based document 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 to 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 March 6, 2005 [Page 4]

5 1.2 Example A minimal, single-entry Atom Feed Document: <?xml version="1.0" encoding="utf-8"?> <feed version="draft-ietf-atompub-format-02: do not deploy" xmlns=" <head> <title>example Feed</title> <link rel="alternate" type="text/html" href=" <modified> t18:30:02z</modified> <author> <name>john Doe</name> </author> </head> <entry> <title>atom-powered Robots Run Amok</title> <link rel="alternate" type="text/html" href=" <id>tag:example.org,2003:3.2397</id> <issued> t08:29:29-04:00</issued> <modified> t18:30:02z</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 BCP 14, [RFC2119]. This specification uses XML Namespaces [W3C.REC-xml-names ] to uniquely identify XML elements and attribute names. It uses the following namespace prefixes for the indicated namespace URIs; "atom": 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 March 6, 2005 [Page 5]

6 [W3C.REC-xml-infoset ]. However, this specification uses a shorthand for two common terms; the phrase "Information Item" is omitted when naming 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 March 6, 2005 [Page 6]

7 2. Atom Documents This specification describes two kinds of Atom Documents; Atom Feed Documents and Atom Entry Documents. An Atom Feed Document is a representation of an Atom 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 the 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 ] and identified with the "application/atom+xml" media type. Atom Documents MUST be well-formed XML. [[ Validity? ]] Atom constrains the appearance and content of elements and attributes; unless otherwise stated, Atom Documents MAY contain other Information Items as appropriate. In particular, Comment Information Items and Processing Instruction Information Items SHOULD be ignored in the normal processing of an Atom Document. Any element in an Atom Document MAY have an xml:base attribute. XML Base [W3C.REC-xmlbase ] 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 Atom Document 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 ] Section For convenience, the most important are summarised here: o The content of this attribute must be a language tag [RFC3066] or an empty string (e.g., xml:lang=""), which indicates that there is no language information available. o If an element does not have an xml:lang element, the first xml:lang attribute in its ancestors indicates the natural language of its content. [[ feedback as to whether this listing is helpful or not would be appreciated; re-stating the requirements of other specifications is tricky. ]] Nottingham Expires March 6, 2005 [Page 7]

8 [[ 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 how Atom Documents can be extended. Nottingham Expires March 6, 2005 [Page 8]

9 3. Common Atom Constructs Many of Atom s elements share a few common 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: "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 a media type [RFC2045]. If this attribute is not present, processors MUST behave as if it were present with a value of "text/ plain" "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, processors MUST behave as if its value were "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 is escaped, as defined in [W3C.REC-xml ] (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 element that describes a person, corporation, or similar entity. Nottingham Expires March 6, 2005 [Page 9]

10 Person constructs MAY be extended by namespace-qualified element children. Ordering of the element children of Person constructs MUST NOT be considered significant "atom:name" Element The "atom:name" element s content conveys a human-readable name for the person. Person constructs MUST contain exactly one "atom:name" element "atom:uri" Element The "atom:uri" element s content conveys a URI associated with the person. Person constructs MAY contain an atom:uri element, but MUST NOT contain more than one. The content of atom:uri in a Person construct MUST be a URI [RFC2396]. xml:base [W3C.REC-xmlbase ] processing MUST be applied to the atom:uri element s content "atom: " Element The "atom: " element s content conveys an address associated with the persons. Person constructs MAY contain an atom: element, but MUST NOT contain more than one. Its content MUST be an address [RFC2822]. 3.3 Date Constructs A Date construct is an element whose content MUST conform to the date-time BNF rule in [RFC3339]. 3.4 Link Constructs A Link construct is an element that MUST NOT have any child content, and has the following attributes: "rel" Attribute The "rel" attribute indicates the type of relationship that the link represents. Link constructs MUST have a rel attribute, whose value MUST be one of the values enumerated in the Atom Protocol specification [Atom-protocol]. Nottingham Expires March 6, 2005 [Page 10]

11 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. Link constructs MUST have a type attribute, whose value MUST be a media type [RFC2045] "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 ] processing MUST be applied to the href attribute s content "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] "title" Attribute The "title" attribute conveys human-readable information about the link. Link constructs MAY have a title attribute. 3.5 Identity Constructs An Identity construct is an element whose content conveys a permanent, universally unique identifier for the construct s parent. Its content MUST be an absolute URI [RFC2396] that is universally unique; i.e., it MUST NOT change over time, even if the parent feed or entry element is relocated, migrated, syndicated, republished, exported or imported Dereferencing Identity Constructs The content of an Identity construct MAY be dereferencable (e.g. a HTTP URI). However, processors MUST NOT assume it to be dereferencable. Nottingham Expires March 6, 2005 [Page 11]

12 If the identified resource is served dynamically, the content of an Identity construct MUST be created only once and then stored along with the resource. The content of an Identity construct MUST NOT be created dynamically. Because of the risk of confusion between URIs that would be equivalent if dereferenced, the following normalization strategy is strongly encouraged when generating Identity constructs: o Provide the scheme in lowercase characters. o Provide the host, if any, in lowercase characters. o Only perform percent-encoding where it is essential. o Use uppercase A-through-F characters when percent-encoding. o Prevent dot-segments appearing in paths. o For schemes that define a default authority, use an empty authority if the default is desired. o For schemes that define an empty path to be equivalent to a path of "/", use "/". o For schemes that define a port, use an empty port if the default is desired. o Preserve empty fragment identifiers and queries. o Ensure that all portions of the URI are utf-8 encoded NFC form Unicode strings Comparing Identity Constructs Instances of Identity constructs can be compared to determine whether a entry or feed is the same as one seen before. Processors MUST compare Identity constructs on a character-by-character basis in a case-sensitive fashion. As a result, two URIs that resolve to the same resource but are not character-for-character identical will be considered different for the purposes of Identifier comparison. For example, " " " and " will all be considered different identifiers, despite their differences in case. Likewise, " bob", " and " will all be considered different identifiers, because URI %-escaping is significant for the purposes of comparison. XML character and entity references MUST be converted into characters before comparison. Nottingham Expires March 6, 2005 [Page 12]

13 4. The "atom:feed" Element The "atom:feed" element is the document (i.e., top-level) element of an Atom Feed Document, acting as a container for metadata and data associated with the feed. Its first element child MUST be atom:head, which MAY be followed zero or more atom:entry child elements. 4.1 "version" Attribute atom:feed elements MUST have a "version" attribute whose content indicates the version of the Atom specification that the feed conforms to. The content of this attribute is unstructured text. The version identifier for this specification is "draft-ietf-atompub-format-02: 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 ] elements as children. Ordering of the element children of atom:head element MUST NOT be considered significant. The following child elements are defined by this specification (note that the presence of some of these elements is required): "atom:title" Element The "atom:title" element is a Content construct that conveys a human-readable title for the feed. atom:head elements MUST contain exactly one atom:title element "atom:link" Element The "atom:link" element is a Link construct that conveys a URI associated with the feed. The nature of the relationship is determined by the construct s rel attribute. atom:head elements MUST contain at least one atom:link element with a rel attribute value of "alternate". atom: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. Nottingham Expires March 6, 2005 [Page 13]

14 If a feed s atom:link element with type="alternate" resolves to an HTML document, then that document SHOULD have a autodiscovery link element [Atom-autodiscovery] that reflects back to the feed. atom:head elements MAY contain additional atom:link elements beyond those described above "atom:author" Element The "atom:author" element is a Person construct that indicates the default author of the feed. atom: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:head elements MUST NOT contain more than one atom:author element. [[explain inheritence]] "atom:contributor" Element The "atom:contributor" element is a Person construct that indicates a person or other entity who contributes to the feed. atom:head elements MAY contain one or more atom:contributor elements "atom:tagline" Element The "atom:tagline" element is a Content construct that conveys a human-readable description or tagline for the feed. atom:head elements MAY contain an atom:tagline element, but MUST NOT contain more than one "atom:id" Element The "atom:id" element is an Identity construct that conveys a permanent, universally unique identifier for a feed. atom:head elements MAY contain an atom:id element, but MUST NOT contain more than one "atom:generator" Element The "atom:generator" element s content indentifies the software agent used to generate the feed, for debugging and other purposes. atom: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 "uri" attribute whose value Nottingham Expires March 6, 2005 [Page 14]

15 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 value is unstructured text "atom:copyright" Element The "atom:copyright" element is Content construct that conveys a human-readable copyright statement for the feed. atom: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 "atom:info" Element The "atom:info" element is a Content construct that conveys a human-readable explanation of the feed format itself. atom: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 "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: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". Nottingham Expires March 6, 2005 [Page 15]

16 5. The "atom:entry" Element The "atom:entry" element represents an individual entry. This element can appear as a child of the atom:feed element, or it can appear as the document (i.e., top-level) element of a 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 the entry conforms to. The version identifier for this specification is "draft-ietf-atompub-format-02: do not deploy". The atom:entry element MAY contain any namespace-qualified [W3C.REC-xml-names ] 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): 5.1 "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. 5.2 "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. 5.3 "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 March 6, 2005 [Page 16]

17 exactly one atom:author element, unless, in an Atom Feed Document, the atom:head element contains an atom:author element itself. atom:entry elements MUST NOT contain more than one atom:author element. 5.4 "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. 5.5 "atom:id" Element The "atom:id" element is an Identity construct that conveys a permanent, universally unique identifier for an entry. atom:entry elements MUST contain exactly one atom:id element. 5.6 "atom:updated" Element The "atom:updated" element is a Date construct indicating the most recent instant in time when a change to the entry was made that the publisher wishes to bring to the attention of subscribers. For example, such changes might not include minor adjustments like spelling and grammatical corrections. atom:entry elements MUST contain exactly one atom:updated element. Publishers MAY change the value of this element over time. Processors MAY present entries sorted using this value. Processors MAY choose not to present entries until the instant in time specified in the atom:updated element has passed. 5.7 "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 an atom:summary element, but MUST NOT contain more than one. 5.8 "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 MUST NOT be specified, and content element MUST contain 1 or more content elements. These content elements MUST NOT (i.e. Nottingham Expires March 6, 2005 [Page 17]

18 only one level of nesting is allowed). Consumers SHOULD look at all alternative content elements and determine which one is most suitable, based on the consumer supports, and preferences specified by the end user (if any). Consumers SHOULD NOT render more than one content alternative. 5.9 "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 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. 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 "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 atom:origin MUST be the same, character-for-character, as that of the atom:id element in that document s atom:head section (i.e., the XPath expression "/atom:feed/atom:head/atom:id"). 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. Nottingham Expires March 6, 2005 [Page 18]

19 6. Managing Feed State [[ talk about what it means to keep a view of a feed ]] Nottingham Expires March 6, 2005 [Page 19]

20 7. Securing Atom Documents Because Atom is an XML-based format, existing XML security mechanisms can be used to secure its content. Note that while these mechanisms are available to secure Atom documents, they should not be used indiscriminately. 7.1 Digital Signatures The document element of an Atom document (i.e., atom:feed in an Atom Feed Document, atom:entry in an Atom Entry Document) MAY have an Enveloped Signature, as described by XML-Signature and Syntax Processing [W3C.REC-xmldsig-core ]. Other XML signature mechanisms MUST NOT be used on the document element of an Atom document. Processors MUST NOT reject an Atom document containing such a signature because they are not capable of verifying it; they MUST continue processing and MAY inform the user of their failure to validate the signature. In other words, the presence of an element with the namespace URI " and a local name of "Signature" as a child of the document element must not cause a processor to fail merely because of its presence. Other elements in an Atom document MUST NOT be signed unless their defintions explicitly specify such a capability. 7.2 Encryption The document element of an Atom document (i.e., atom:feed in an Atom Feed Document, atom:entry in an Atom Entry Document) MAY be encrypted, using the mechanisms described by XML Encryption Syntax and Processing [W3C.REC-xmlenc-core ]. Other XML encryption mechanisms MUST NOT be used on the document element of an Atom document. Nottingham Expires March 6, 2005 [Page 20]

21 8. Embedding Atom in Other Formats [[... ]] Nottingham Expires March 6, 2005 [Page 21]

22 9. Extending Atom [[... ]] Nottingham Expires March 6, 2005 [Page 22]

23 10. IANA Considerations An Atom 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]] In 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 address to contact for further information: Mark Nottingham Intended usage: COMMON Author/Change controller: This specification s author(s). [[update upon publication]] Nottingham Expires March 6, 2005 [Page 23]

24 11. Security Considerations Atom document can be encrypted and signed using [W3C.REC-xmlenc-core ] and [W3C.REC-xmldsig-core ], respectively, and is subject to the security considerations implied by their use. 12 Normative References [Atom-autodiscovery] Pilgrim, M., "Atom Feed Autodiscovery", work-in-progress, August [Atom-protocol] Gregorio, J. and R. Sayre, "The Atom Publishing Protocol", work-in-progress, July [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March [RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April [RFC3023] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January [RFC3066] Alvestrand, H., "Tags for the Identification of Languages", BCP 47, RFC 3066, January [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, July [W3C.NOTE-datetime ] Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C NOTE NOTE-datetime , August [W3C.REC-xml ] Yergeau, F., Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (Third Edition)", W3C REC REC-xml , February Nottingham Expires March 6, 2005 [Page 24]

25 [W3C.REC-xml-infoset ] Cowan, J. and R. Tobin, "XML Information Set", W3C REC REC-xml-infoset , October [W3C.REC-xml-names ] Bray, T., Hollander, D. and A. Layman, "Namespaces in XML", W3C REC REC-xml-names , January [W3C.REC-xmlbase ] Marsh, J., "XML Base", W3C REC REC-xmlbase , June [W3C.REC-xmldsig-core ] Eastlake, D., Reagle, J. and D. Solo, "XML-Signature Syntax and Processing", W3C REC REC-xmldsig-core , February [W3C.REC-xmlenc-core ] Eastlake, D. and J. Reagle, "XML Encryption Syntax and Processing", W3C REC REC-xmlenc-core , December [1] < [2] < Author s Address Mark Nottingham (editor) mnot@pobox.com URI: Nottingham Expires March 6, 2005 [Page 25]

26 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 March 6, 2005 [Page 26]

27 Appendix B. Revision History [[ this section should be removed before final publication. ]] -02: Removed entry/modified, entry/issued, entry/created; added entry/updated (PaceDateUpdated). Changed date construct from W3C date-time to RFC3339 (PaceDateUpdated). Feed links to HTML pages should be reflected back (PaceLinkReflection). Added Identity construct (PaceIdConstruct). Changed feed/id and entry/id to be Identity constructs (PaceIdConstruct). Changed entry/origin s content so that it s the same as the feed s id, rather than its link/@rel="alternate" (PaceIdConstruct). Added "Securing Atom Documents" (PaceDigitalSignatures). -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 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). Nottingham Expires March 6, 2005 [Page 27]

28 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 March 6, 2005 [Page 28]

29 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 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 March 6, 2005 [Page 29]