draft-ietf-atompub-format-06.txt   draft-ietf-atompub-format-07.txt 
Network Working Group M. Nottingham, Ed. Network Working Group M. Nottingham, Ed.
Internet-Draft Internet-Draft R. Sayre, Ed.
Expires: September 13, 2005 R. Sayre, Ed. Expires: October 2, 2005 March 31, 2005
Boswijck Memex Consulting
March 12, 2005
The Atom Syndication Format The Atom Syndication Format
draft-ietf-atompub-format-06 draft-ietf-atompub-format-07
Status of this Memo Status of this Memo
This document is an Internet-Draft and is subject to all provisions This document is an Internet-Draft and is subject to all provisions
of Section 3 of RFC 3667. By submitting this Internet-Draft, each of Section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with which he or she become aware will be disclosed, in accordance with
RFC 3668. RFC 3668.
skipping to change at page 1, line 37 skipping to change at page 1, line 35
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on September 13, 2005. This Internet-Draft will expire on October 2, 2005.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
This document specifies Atom, an XML-based Web content and metadata This document specifies Atom, an XML-based Web content and metadata
syndication format. syndication format.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Editorial Notes . . . . . . . . . . . . . . . . . . . . . 4 1.1 Examples . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Example . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 Notational Conventions . . . . . . . . . . . . . . . . . . 5
1.3 Notational Conventions . . . . . . . . . . . . . . . . . . 5 2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 6
2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 7 3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 8
3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 9 3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 8
3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 9 3.1.1 The "type" Attribute . . . . . . . . . . . . . . . . . 8
3.1.1 "type" Attribute . . . . . . . . . . . . . . . . . . . 9
3.2 Person Constructs . . . . . . . . . . . . . . . . . . . . 11 3.2 Person Constructs . . . . . . . . . . . . . . . . . . . . 11
3.2.1 The "atom:name" Element . . . . . . . . . . . . . . . 11 3.2.1 The "atom:name" Element . . . . . . . . . . . . . . . 11
3.2.2 The "atom:uri" Element . . . . . . . . . . . . . . . . 11 3.2.2 The "atom:uri" Element . . . . . . . . . . . . . . . . 11
3.2.3 The "atom:email" Element . . . . . . . . . . . . . . . 11 3.2.3 The "atom:email" Element . . . . . . . . . . . . . . . 11
3.3 Date Constructs . . . . . . . . . . . . . . . . . . . . . 11 3.3 Date Constructs . . . . . . . . . . . . . . . . . . . . . 12
4. Atom Element Definitions . . . . . . . . . . . . . . . . . . 13 4. Atom Element Definitions . . . . . . . . . . . . . . . . . . 13
4.1 Container Elements . . . . . . . . . . . . . . . . . . . . 13 4.1 Container Elements . . . . . . . . . . . . . . . . . . . . 13
4.1.1 The "atom:feed" Element . . . . . . . . . . . . . . . 13 4.1.1 The "atom:feed" Element . . . . . . . . . . . . . . . 13
4.1.2 The "atom:entry" Element . . . . . . . . . . . . . . . 14 4.1.2 The "atom:entry" Element . . . . . . . . . . . . . . . 15
4.1.3 The "atom:content" Element . . . . . . . . . . . . . . 16 4.1.3 The "atom:content" Element . . . . . . . . . . . . . . 17
4.2 Metadata Elements . . . . . . . . . . . . . . . . . . . . 19 4.2 Metadata Elements . . . . . . . . . . . . . . . . . . . . 20
4.2.1 The "atom:author" Element . . . . . . . . . . . . . . 19 4.2.1 The "atom:author" Element . . . . . . . . . . . . . . 20
4.2.2 The "atom:category" Element . . . . . . . . . . . . . 20 4.2.2 The "atom:category" Element . . . . . . . . . . . . . 20
4.2.3 The "atom:contributor" Element . . . . . . . . . . . . 20 4.2.3 The "atom:contributor" Element . . . . . . . . . . . . 20
4.2.4 The "atom:copyright Element . . . . . . . . . . . . . 20 4.2.4 The "atom:copyright" Element . . . . . . . . . . . . . 21
4.2.5 The "atom:generator" Element . . . . . . . . . . . . . 21 4.2.5 The "atom:generator" Element . . . . . . . . . . . . . 21
4.2.6 The "atom:icon" Element . . . . . . . . . . . . . . . 21 4.2.6 The "atom:icon" Element . . . . . . . . . . . . . . . 21
4.2.7 The "atom:id" Element . . . . . . . . . . . . . . . . 21 4.2.7 The "atom:id" Element . . . . . . . . . . . . . . . . 22
4.2.8 The "atom:image" Element . . . . . . . . . . . . . . . 23 4.2.8 The "atom:image" Element . . . . . . . . . . . . . . . 23
4.2.9 The "atom:link" Element . . . . . . . . . . . . . . . 23 4.2.9 The "atom:link" Element . . . . . . . . . . . . . . . 24
4.2.10 The "atom:published" Element . . . . . . . . . . . . 26 4.2.10 The "atom:published" Element . . . . . . . . . . . . 26
4.2.11 The "atom:source-feed" Element . . . . . . . . . . . 26 4.2.11 The "atom:source" Element . . . . . . . . . . . . . 26
4.2.12 The "atom:subtitle" Element . . . . . . . . . . . . 26 4.2.12 The "atom:subtitle" Element . . . . . . . . . . . . 27
4.2.13 The "atom:summary" Element . . . . . . . . . . . . . 27 4.2.13 The "atom:summary" Element . . . . . . . . . . . . . 27
4.2.14 The "atom:title" Element . . . . . . . . . . . . . . 27 4.2.14 The "atom:title" Element . . . . . . . . . . . . . . 27
4.2.15 The "atom:updated" Element . . . . . . . . . . . . . 27 4.2.15 The "atom:updated" Element . . . . . . . . . . . . . 27
5. Securing Atom Documents . . . . . . . . . . . . . . . . . . 28 5. Securing Atom Documents . . . . . . . . . . . . . . . . . . 29
5.1 Digital Signatures . . . . . . . . . . . . . . . . . . . . 28 6. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 30
5.2 Encryption . . . . . . . . . . . . . . . . . . . . . . . . 28 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 32
6. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 29 8. Security Considerations . . . . . . . . . . . . . . . . . . 34
6.1 Extensions From Non-Atom Vocabularies . . . . . . . . . . 29 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
6.2 Extensions To the Atom Vocabulary . . . . . . . . . . . . 29 9.1 Normative References . . . . . . . . . . . . . . . . . . . 35
6.3 Software Processing of Foreign Markup . . . . . . . . . . 29 9.2 Informative References . . . . . . . . . . . . . . . . . . 36
6.4 Extension Elements . . . . . . . . . . . . . . . . . . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 37
6.4.1 Simple Extension Elements . . . . . . . . . . . . . . 30 A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 38
6.4.2 Structured Extension Elements . . . . . . . . . . . . 30 B. Collected RELAX NG Compact Schema . . . . . . . . . . . . . 39
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 31 C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 47
7.1 Registry of Link Relations . . . . . . . . . . . . . . . . 31 Intellectual Property and Copyright Statements . . . . . . . 50
8. Security Considerations . . . . . . . . . . . . . . . . . . 33
8.1 HTML and XHTML Content . . . . . . . . . . . . . . . . . . 33
8.2 URIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.3 IRIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.4 Encryption and Signing . . . . . . . . . . . . . . . . . . 33
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
9.1 Normative References . . . . . . . . . . . . . . . . . . . 34
9.2 Informative References . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 36
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 37
B. Collected RELAX NG Compact Schema . . . . . . . . . . . . . 38
C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 45
Intellectual Property and Copyright Statements . . . . . . . 48
1. Introduction 1. Introduction
Atom is an XML-based document format that describes lists of related Atom is an XML-based document format that describes lists of related
information known as "feeds". Feeds are composed of a number of information known as "feeds". Feeds are composed of a number of
items, known as "entries", each with an extensible set of attached items, known as "entries", each with an extensible set of attached
metadata. For example, each entry has a title. metadata. For example, each entry has a title.
The primary use case that Atom addresses is the syndication of Web 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 content such as Weblogs and news headlines to Web sites as well as
directly to user agents. However, nothing precludes it from being directly to user agents. However, nothing precludes it from being
used for other purposes and kinds of content. used for other purposes and kinds of content.
1.1 Editorial Notes 1.1 Examples
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 <http://www.imc.org/atom-syntax/index.html>
The Atom Wiki Web site
<http://www.intertwingly.net/wiki/pie/FrontPage>
Active development takes place on the mailing list, while the Wiki is
used for issue tracking and new proposals.
1.2 Example
A minimal, single-entry Atom Feed Document: A minimal, single-entry Atom Feed Document:
<?xml version="1.0" encoding="UTF-8"?> <?xml version="1.0" encoding="utf-8"?>
<feed <feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-07">
xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-06">
<title>Example Feed</title> <title>Example Feed</title>
<link href="http://example.org/"/> <link href="http://example.org/"/>
<updated>2003-12-13T18:30:02Z</updated> <updated>2003-12-13T18:30:02Z</updated>
<author> <author>
<name>John Doe</name> <name>John Doe</name>
</author> </author>
<entry> <entry>
<title>Atom-Powered Robots Run Amok</title> <title>Atom-Powered Robots Run Amok</title>
<link href="http://example.org/2003/12/13/atom03"/> <link href="http://example.org/2003/12/13/atom03"/>
<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id> <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
<updated>2003-12-13T18:30:02Z</updated> <updated>2003-12-13T18:30:02Z</updated>
<content>Some text.</content>
</entry> </entry>
</feed>
[[anchor4: Ask yourself: is the example atom:entry valid?]] </feed>
A more extensive, single-entry Atom Feed Document:
1.3 Notational Conventions <?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-07">
<title type="text">dive into mark</title>
<subtitle type="html">
A &lt;em&gt;lot&lt;/em&gt; of effort
went into making this effortless
</subtitle>
<updated>2005-04-02T12:29:29Z</updated>
<id>tag:example.org,2003:3</id>
<link rel="alternate" type="text/html"
hreflang="en" href="http://example.org/"/>
<copyright>Copyright (c) 2003, Mark Pilgrim</copyright>
<generator uri="http://www.example.com/" version="1.0">
Example Toolkit
</generator>
<entry>
<title>Atom draft-07 snapshot</title>
<link rel="alternate" type="text/html"
href="http://example.org/2005/04/02/atom"/>
<link rel="enclosure" type="audio/mpeg" length="1337"
href="http://example.org/audio/ph34r_my_podcast.mp3"/>
<id>tag:example.org,2003:3.2397</id>
<updated>2005-04-02T12:29:29Z</updated>
<published>2003-12-13T08:29:29-04:00</published>
<author>
<name>Mark Pilgrim</name>
<uri>http://example.org/</uri>
<email>f8dy@example.com</email>
</author>
<contributor>
<name>Sam Ruby</name>
<uri>http://intertwingly.net/blog/</uri>
</contributor>
<contributor>
<name>Joe Gregorio</name>
<uri>http://bitworking.org/</uri>
</contributor>
<content type="xhtml" xml:lang="en"
xml:base="http://diveintomark.org/">
<div xmlns="http://www.w3.org/1999/xhtml">
<p><i>[Update: The Atom draft-07 snapshot is out.]</i></p>
</div>
</content>
</entry>
</feed>
This specification describes conformance in terms of two kinds of 1.2 Notational Conventions
artefacts; Atom Feed Documents and Atom Entry documents.
Additionally, it places some requirements on Atom Processors.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", This specification describes conformance in terms of two artifacts;
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this Atom Feed Documents and Atom Entry documents. Additionally, it
document are to be interpreted as described in BCP 14, [RFC2119], as places some requirements on Atom Processors.
scoped to those conformance targets.
This specification uses XML Namespaces [W3C.REC-xml-names-19990114] This specification uses XML Namespaces [W3C.REC-xml-names-19990114]
to uniquely identify XML elements names. It uses the following to uniquely identify XML element names. It uses the following
namespace prefixes for the indicated namespace URIs; namespace prefix for the indicated namespace URI;
"atom": http://purl.org/atom/ns#draft-ietf-atompub-format-06 "atom": http://purl.org/atom/ns#draft-ietf-atompub-format-07
Note that the choice of any namespace prefix is arbitrary and not Note that the choice of any namespace prefix is arbitrary and not
semantically significant. semantically significant.
Atom is specified using terms from the XML Infoset Atom is specified using terms from the XML Infoset
[W3C.REC-xml-infoset-20040204]. However, this specification uses a [W3C.REC-xml-infoset-20040204]. However, this specification uses a
shorthand for two common terms; the phrase "Information Item" is shorthand for two common terms; the phrase "Information Item" is
omitted when naming Element Information Items and Attribute omitted when naming Element Information Items and Attribute
Information Items. Information Items.
Therefore, when this specification uses the term "element," it is Therefore, when this specification uses the term "element," it is
referring to an Element Information Item in Infoset terms. Likewise, referring to an Element Information Item in Infoset terms. Likewise,
when it uses the term "attribute," it is referring to an Attribute when it uses the term "attribute," it is referring to an Attribute
Information Item. Information Item.
Some sections of this specification are illustrated with fragments of Some sections of this specification are illustrated with fragments of
a non-normative RELAX NG Compact schema [RELAX-NG]. However, the a non-normative RELAX NG Compact schema [RELAX-NG]. However, the
text of this specification provides the definition of conformance. A text of this specification provides the definition of conformance. A
collected schema appears in an informative appendix. collected schema appears in Appendix B.
Some sections of this specification are illustrated with Augmented
Backus-Naur Form (ABNF), a format used to represent permissible
strings in a protocol or language, as defined in [RFC2234].
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], as
scoped to those conformance targets.
2. Atom Documents 2. Atom Documents
This specification describes two kinds of Atom Documents; Atom Feed This specification describes two kinds of Atom Documents; Atom Feed
Documents and Atom Entry Documents. Documents and Atom Entry Documents.
An Atom Feed Document is a representation of an Atom feed, including An Atom Feed Document is a representation of an Atom feed, including
metadata about the feed, and some or all of the entries associated metadata about the feed, and some or all of the entries associated
with it. Its root is the atom:feed element. with it. Its root is the atom:feed element.
An Atom Entry Document represents exactly one Atom Entry, outside of An Atom Entry Document represents exactly one Atom entry, outside of
the context of an Atom Feed. Its root is the atom:entry element. the context of an Atom feed. Its root is the atom:entry element.
namespace
atom ="http://purl.org/atom/ns#draft-ietf-atompub-format-06"
namespace atom =
"http://purl.org/atom/ns#draft-ietf-atompub-format-07"
start = atomFeed | atomEntry start = atomFeed | atomEntry
Both kinds of Atom documents are specified in terms of the XML Both kinds of Atom documents are specified in terms of the XML
Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204] and Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204] and
identified with the "application/atom+xml" media type. Atom identified with the "application/atom+xml" media type. Atom
Documents MUST be well-formed XML. Documents MUST be well-formed XML.
Atom constrains the appearance and content of elements and Atom constrains the appearance and content of elements and
attributes; unless otherwise stated, Atom Documents MAY contain other attributes; unless otherwise stated, Atom Documents MAY contain other
Information Items as appropriate. In particular, Comment Information Information Items as appropriate.
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 Any element defined by this specification MAY have an xml:base
Base [W3C.REC-xmlbase-20010627] processing MUST be applied to any attribute. XML Base [W3C.REC-xmlbase-20010627] processing MUST be
relative reference [RFC3987] present in an Atom Document. This applied to any relative reference [RFC3987] present in an Atom
includes such elements and attributes as specified by Atom itself, as Document. This includes such elements and attributes as specified by
well as those specified by extensions to Atom. Atom itself, as well as those specified by extensions to Atom.
Any element in an Atom Document MAY have an xml:lang attribute, whose Any element defined by this specification MAY have an xml:lang
content indicates the natural language for the element and its attribute, whose content indicates the natural language for the
children. The language context is only significant for elements and element and its children. The language context is only significant
attributes declared to be "language-sensitive" by this specification. for elements and attributes declared to be "language-sensitive" by
Requirements regarding the content and interpretation of xml:lang are this specification. Requirements regarding the content and
specified in XML 1.0 [W3C.REC-xml-20040204], Section 2.12. interpretation of xml:lang are specified in XML 1.0
[W3C.REC-xml-20040204], Section 2.12.
atomCommonAttributes = atomCommonAttributes =
attribute xml:base { atomUri }?, attribute xml:base { atomUri }?,
attribute xml:lang { atomLanguageTag }? attribute xml:lang { atomLanguageTag }?
Atom allows the use of IRIs [RFC3987], rather than only URIs Atom allows the use of IRIs [RFC3987], as well as URIs [RFC3986].
[RFC3986]. For resolution, IRIs can easily be converted to URIs. For resolution, IRIs can easily be converted to URIs. When comparing
When comparing IRIs serving as Identity Constructs, they MUST NOT be IRIs serving as atom:id values, they MUST NOT be converted to URIs.
converted to URIs. Please note that by definition, every URI is an By definition, every URI is an IRI, so any URI can be used where an
IRI, so any URI can be used where an IRI is needed. IRI is needed.
[[anchor7: discussion of white space]]
Atom is an extensible format. See the section titled 'Extending Atom is an extensible format. See the section titled 'Extending
Atom' later in this document for a full description of how Atom Atom' later in this document for a full description of how Atom
Documents can be extended. Documents can be extended.
Atom Processors MAY keep state (e.g., metadata in atom:feed, entries) Atom Processors MAY keep state (e.g., metadata in atom:feed, entries)
sourced from Atom Feed Documents and combine them with other Atom sourced from Atom Feed Documents and combine them with other Atom
Feed Documents, in order to facilitate a contiguous view of the Feed Documents, in order to facilitate a contiguous view of the
contents of a feed. The manner in which Atom Feed Documents are contents of a feed. The manner in which Atom Feed Documents are
combined in order to reconstruct a feed (e.g., updating entries and combined in order to reconstruct a feed (e.g., updating entries and
metadata, dealing with missing entries) is out of the scope of this metadata, dealing with missing entries) is out of the scope of this
specification, but may be defined by an extension to Atom. specification, but may be defined by an extension to Atom.
3. Common Atom Constructs 3. Common Atom Constructs
Many of Atom's elements share a few common structures. This section Many of Atom's elements share a few common structures. This section
defines a few such structures and their requirements for convenient defines those structures and their requirements for convenient
reference by the appropriate element definitions. reference by the appropriate element definitions.
When an element is identified as being a particular kind of When an element is identified as being a particular kind of
construct, it inherits the corresponding requirements from that construct, it inherits the corresponding requirements from that
construct's definition in this section. construct's definition in this section.
3.1 Text Constructs 3.1 Text Constructs
A Text construct contains human readable text, usually in small A Text construct contains human-readable text, usually in small
quantities. Except for the "type" attribute, the content of Text quantities. The content of Text constructs is language-sensitive.
constructs is language-sensitive.
atomPlainTextConstruct = atomPlainTextConstruct =
atomCommonAttributes, atomCommonAttributes,
attribute type { "text" | "html" }?, attribute type { "text" | "html" }?,
text text
atomXHTMLTextConstruct = atomXHTMLTextConstruct =
atomCommonAttributes, atomCommonAttributes,
attribute type { "xhtml" }, attribute type { "xhtml" },
(text|anyElement)* xhtmlDiv
atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct
3.1.1 "type" Attribute 3.1.1 The "type" Attribute
Text constructs MAY have a "type" attribute. [[anchor11: Some feel Text constructs MAY have a "type" attribute. When present, the value
type attributes with different allowable values in different elements MUST be one of "text", "html" or "xhtml". If the "type" attribute is
is confusing.]]. When present, the value MUST be one of "text", not provided, Atom Processors MUST behave as though it were present
"html" or "xhtml". If the "type" attribute is not provided, Atom with a value of "text".
Processors MUST behave as though it were present with a value of
"text".
Note that MIME media types [RFC2045] are not acceptable values for Note that MIME media types [RFC2045] are not acceptable values for
the "type" attribute. the "type" attribute.
3.1.1.1 Text
Example atom:title with text content:
...
<title type="text">
Less: &lt;
</title>
...
If the value is "text", the content of the Text construct MUST NOT If the value is "text", the content of the Text construct MUST NOT
contain child elements. Such text is intended to be presented to contain child elements. Such text is intended to be presented to
humans in a readable fashion. Thus, Atom Processors MAY display it humans in a readable fashion. Thus, Atom Processors MAY display it
using normal text rendering techniques such as proportional fonts, using normal text rendering techniques such as proportional fonts,
white-space collapsing, and justification. white-space collapsing, and justification.
3.1.1.2 HTML
Example atom:title with HTML content:
...
<title type="html">
Less: &lt;em> &amp;lt; &lt;/em>
</title>
...
If the value of "type" is "html", the content of the Text construct If the value of "type" is "html", the content of the Text construct
MUST NOT contain child elements, and SHOULD be suitable for handling MUST NOT contain child elements, and SHOULD be suitable for handling
as HTML [W3C.REC-html401-19991224]. Any markup within MUST be as HTML [W3C.REC-html401-19991224]. Any markup within MUST be
escaped; for example, "<br>" as "&lt;br>". HTML markup within SHOULD escaped; for example, "<br>" as "&lt;br>". HTML markup within SHOULD
be such that it could validly appear directly within an HTML <DIV> be such that it could validly appear directly within an HTML <DIV>
element, after unescaping. Atom Processors that display such content element, after unescaping. Atom Processors that display such content
MAY use markup to aid in its display. MAY use that markup to aid in its display.
[[anchor12: example atom entry w/ escaped markup]] 3.1.1.3 XHTML
Example atom:title with XHTML content:
...
<title type="xhtml" xmlns:xhtml="http://www.w3.org/1999/xhtml">
<xhtml:div>
Less: <xhtml:em> &lt; </xhtml:em>
</xhtml:div>
</title>
...
If the value of "type" is "xhtml", the content of the Text construct If the value of "type" is "xhtml", the content of the Text construct
MUST be a single XHTML div element [W3C.REC-xhtml-basic-20001219]. MUST be a single XHTML div element [W3C.REC-xhtml-basic-20001219].
The XHTML div MUST contain XHTML text and markup that could validly The XHTML div MUST contain XHTML text and markup that could validly
appear within an XHTML div element. The XHTML div element itself appear within an XHTML div element. The XHTML div element itself
MUST NOT be considered part of the content. Atom Processors which MUST NOT be considered part of the content. Atom Processors which
display the content MAY use the markup to aid in displaying it. display the content MAY use the markup to aid in displaying it.
Escaped markup is interpreted as a text representation of markup, and Escaped characters, such as "&" and ">", represent those characters,
MUST NOT be interpreted as markup itself. not markup.
Example: Examples of valid XHTML content:
... ...
<summary type="xhtml"> <summary type="xhtml">
<div xmlns="http://www.w3.org/1999/xhtml"> <div xmlns="http://www.w3.org/1999/xhtml">
This is <b>XHTML</b> content. This is <b>XHTML</b> content.
</div> </div>
</summary> </summary>
... ...
<summary type="xhtml"> <summary type="xhtml">
<xhtml:div xmlns:xhtml="http://www.w3.org/1999/xhtml"> <xhtml:div xmlns:xhtml="http://www.w3.org/1999/xhtml">
skipping to change at page 11, line 10 skipping to change at page 11, line 10
This is <xh:b>XHTML</xh:b> content. This is <xh:b>XHTML</xh:b> content.
</xh:div> </xh:div>
</summary> </summary>
... ...
3.2 Person Constructs 3.2 Person Constructs
A Person construct is an element that describes a person, A Person construct is an element that describes a person,
corporation, or similar entity (hereafter, 'person'). corporation, or similar entity (hereafter, 'person').
Person constructs MAY be extended by namespace-qualified element
children.
This specification assigns no significance to the order of appearance
of the child elements in a Person construct.
atomPersonConstruct = atomPersonConstruct =
atomCommonAttributes, atomCommonAttributes,
(element atom:name { text } & (element atom:name { text }
element atom:uri { atomUri }? & & element atom:uri { atomUri }?
element atom:email { atomEmailAddress }?) & element atom:email { atomEmailAddress }?
& extensionElement*)
This specification assigns no significance to the order of appearance
of the child elements in a Person construct. Person constructs allow
extension Metadata Elements (see Section 6.4).
3.2.1 The "atom:name" Element 3.2.1 The "atom:name" Element
The "atom:name" element's content conveys a human-readable name for The "atom:name" element's content conveys a human-readable name for
the person. The content of atom:name is language sensitive. Person the person. The content of atom:name is language-sensitive. Person
constructs MUST contain exactly one "atom:name" element. constructs MUST contain exactly one "atom:name" element.
3.2.2 The "atom:uri" Element 3.2.2 The "atom:uri" Element
The "atom:uri" element's content conveys an IRI associated with the The "atom:uri" element's content conveys an IRI associated with the
person. Person constructs MAY contain an atom:uri element, but MUST person. Person constructs MAY contain an atom:uri element, but MUST
NOT contain more than one. The content of atom:uri in a Person NOT contain more than one. The content of atom:uri in a Person
construct MUST be an IRI reference [RFC3987]. construct MUST be an IRI reference [RFC3987].
xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the
atom:uri element's content.
3.2.3 The "atom:email" Element 3.2.3 The "atom:email" Element
The "atom:email" element's content conveys an e-mail address The "atom:email" element's content conveys an e-mail address
associated with the person. Person constructs MAY contain an associated with the person. Person constructs MAY contain an
atom:email element, but MUST NOT contain more than one. Its content atom:email element, but MUST NOT contain more than one. Its content
MUST conform to the addr-spec BNF rule in [RFC2822]. MUST conform to the addr-spec BNF rule in [RFC2822].
3.3 Date Constructs 3.3 Date Constructs
A Date construct is an element whose content MUST conform to the A Date construct is an element whose content MUST conform to the
date-time BNF rule in [RFC3339]. I.e., the content of this element extended date-time form ABNF rule in [RFC3339]. In addition, an
matches this regular expression: uppercase "T" character MUST be used to separate date and time, and
an uppercase "Z" character MUST be present in the absence of a
[0-9]{8}T[0-9]{2}:[0-9]{2}:[0-9]{2}(\.[0-9]+) numeric time zone offset.
?(Z|[\+\-][0-9]{2}:[0-9]{2})
As a result, the date values conform to the following specifications:
[RFC3339], [W3C.REC-xmlschema-2-20041028],
[W3C.NOTE-datetime-19980827], and [ISO.8601.1988].
atomDateConstruct = atomDateConstruct =
atomCommonAttributes, atomCommonAttributes,
xsd:dateTime xsd:dateTime
Such date values happen to be compatible with the following
specifications: [ISO.8601.1988], [W3C.NOTE-datetime-19980827], and
[W3C.REC-xmlschema-2-20041028].
Date values SHOULD be as accurate as possible. For example, it would
be generally inappropriate for a publishing system to apply the same
timestamp to several entries which were published during the course
of a single day.
4. Atom Element Definitions 4. Atom Element Definitions
4.1 Container Elements 4.1 Container Elements
4.1.1 The "atom:feed" Element 4.1.1 The "atom:feed" Element
[[anchor21: Substantially changed from format-05, review carefully.]]
The "atom:feed" element is the document (i.e., top-level) element of 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 an Atom Feed Document, acting as a container for metadata and data
associated with the feed. Its element children consist of one or associated with the feed. Its element children consist of metadata
more metadata elements followed by zero or more atom:entry child elements followed by zero or more atom:entry child elements.
elements.
This specification assigns no significance to the order of atom:entry
elements within the feed.
atomFeed = atomFeed =
element atom:feed { element atom:feed {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor?
& atomCategory* & atomCategory*
& atomContributor* & atomContributor*
& atomCopyright? & atomCopyright?
& atomGenerator? & atomGenerator?
& atomIcon? & atomIcon?
& atomId? & atomId?
& atomImage? & atomImage?
& atomLink+ & atomLink+
& atomSubtitle? & atomSubtitle?
& atomTitle & atomTitle
& atomUpdated & atomUpdated
& anyElement* ), & extensionElement*),
atomEntry* atomEntry*
} }
This specification assigns no significance to the order of atom:entry
elements within the feed.
The following child elements are defined by this specification (note The following child elements are defined by this specification (note
that the presence of some of these elements is required): that the presence of some of these elements is required):
o atom:feed elements MUST contain exactly one atom:author element, o atom:feed elements MUST contain exactly one atom:author element,
UNLESS all of the atom:feed element's child atom:entry elements UNLESS all of the atom:feed element's child atom:entry elements
contain an atom:author element. atom:feed elements MUST NOT contain an atom:author element. atom:feed elements MUST NOT
contain more than one atom:author element. [[anchor22: contain more than one atom:author element.
inheritance]]
o atom:feed elements MAY contain any number of atom:category o atom:feed elements MAY contain any number of atom:category
elements. elements.
o atom:feed elements MAY contain any number of atom:contributor o atom:feed elements MAY contain any number of atom:contributor
elements. elements.
o atom:feed elements MUST NOT contain more than one atom:copyright o atom:feed elements MUST NOT contain more than one atom:copyright
element. element.
o atom:feed elements MUST NOT contain more than one atom:generator o atom:feed elements MUST NOT contain more than one atom:generator
element. element.
o atom:feed elements MUST NOT contain more than one atom:icon o atom:feed elements MUST NOT contain more than one atom:icon
element. element.
o atom:feed elements MUST NOT contain more than one atom:image o atom:feed elements MUST NOT contain more than one atom:image
element. element.
skipping to change at page 14, line 19 skipping to change at page 14, line 28
o atom:feed elements MUST NOT contain more than one atom:generator o atom:feed elements MUST NOT contain more than one atom:generator
element. element.
o atom:feed elements MUST NOT contain more than one atom:icon o atom:feed elements MUST NOT contain more than one atom:icon
element. element.
o atom:feed elements MUST NOT contain more than one atom:image o atom:feed elements MUST NOT contain more than one atom:image
element. element.
o atom:feed elements MUST NOT contain more than one atom:id element. o atom:feed elements MUST NOT contain more than one atom:id element.
o atom:feed elements MUST contain at least one atom:link element o atom:feed elements MUST contain at least one atom:link element
with a relation of "alternate". with a relation of "alternate".
o atom:feed elements SHOULD contain one atom:link element with a rel o atom:feed elements SHOULD contain one atom:link element with a rel
attribute value of "self" and SHOULD contain a href attribute with attribute value of "self". This URI identifies the feed and a
an absolute URI as its value. This URI identifies the feed and a
representation equivalent to the feed. representation equivalent to the feed.
o atom:feed elements MUST NOT contain more than one atom:link o atom:feed elements MUST NOT contain more than one atom:link
element with a rel attribute value of "alternate" that has the element with a rel attribute value of "alternate" that has the
same type attribute value. If a feed's atom:link element with same type attribute value. If a feed's atom:link element with
type="alternate" resolves to an HTML document, then that document type="alternate" resolves to an HTML document, then that document
SHOULD have a autodiscovery link element [Atom-autodiscovery] that SHOULD have a autodiscovery link element [Atom-autodiscovery] that
reflects back to the feed. atom:feed elements MAY contain reflects back to the feed. atom:feed elements MAY contain
additional atom:link elements beyond those described above. additional atom:link elements beyond those described above.
o atom:feed elements MUST NOT contain more than one atom:subtitle o atom:feed elements MUST NOT contain more than one atom:subtitle
element. element.
skipping to change at page 14, line 44 skipping to change at page 15, line 13
identical atom:id values. identical atom:id values.
4.1.2 The "atom:entry" Element 4.1.2 The "atom:entry" Element
The "atom:entry" element represents an individual entry, acting as a The "atom:entry" element represents an individual entry, acting as a
container for metadata and data associated with the entry. This container for metadata and data associated with the entry. This
element can appear as a child of the atom:feed element, or it can 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 appear as the document (i.e., top-level) element of a standalone Atom
Entry Document. Entry Document.
The atom:entry element MAY contain any namespace-qualified
[W3C.REC-xml-names-19990114] elements as children. This
specification assigns no significance to the order of appearance of
the child elements of atom:entry.
atomEntry = atomEntry =
element atom:entry { element atom:entry {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor?
& atomCategory* & atomCategory*
& atomContent? & atomContent?
& atomContributor* & atomContributor*
& atomCopyright? & atomCopyright?
& atomId & atomId
& atomLink* & atomLink*
& atomPublished? & atomPublished?
& atomSourceFeed? & atomSource?
& atomSummary? & atomSummary?
& atomTitle & atomTitle
& atomUpdated & & atomUpdated
anyElement*) & extensionElement*)
} }
This specification assigns no significance to the order of appearance
of the child elements of atom:entry.
The following child elements are defined by this specification (note The following child elements are defined by this specification (note
that it requires the presence of some of these elements): that it requires the presence of some of these elements):
o atom:entry elements MUST contain exactly one atom:author element, o atom:entry elements MUST contain exactly one atom:author element,
unless, in an Atom Feed Document, the atom:feed element contains unless the atom:entry contains an atom:source element which
an atom:author element itself. atom:entry elements MUST NOT contains an atom:author element, or, in an Atom Feed Document, the
contain more than one atom:author element. [[anchor24: What if atom:feed element contains an atom:author element itself.
there's a source-feed element? This is busted. We should make atom:entry elements MUST NOT contain more than one atom:author
author required for atom:feed and optional for atom:entry. No element.
inheritance co-constraints required. --R. Sayre]]
o atom:entry elements MAY contain any number of atom:category o atom:entry elements MAY contain any number of atom:category
elements. elements.
o atom:entry elements MUST NOT contain more than one atom:content
element.
o atom:entry elements MAY contain any number of atom:contributor o atom:entry elements MAY contain any number of atom:contributor
elements. elements.
o atom:entry elements MUST NOT contain more than one atom:copyright o atom:entry elements MUST NOT contain more than one atom:copyright
element. element.
o atom:entry elements MUST contain exactly one atom:id element. o atom:entry elements MUST contain exactly one atom:id element.
o atom:entry elements that contain no child atom:content element o atom:entry elements that contain no child atom:content element
MUST contain at least one atom:link element with a rel attribute MUST contain at least one atom:link element with a rel attribute
value of "alternate". [[anchor25: "atom:entry elements MUST NOT value of "alternate". atom:entry elements MUST NOT contain more
contain more than one atom:link element with a rel attribute value than one atom:link element with a rel attribute value of
of "alternate" that has the same type attribute value." This "alternate" that has the same combination of type and hreflang
requirement predates @hreflang. Keep it? --R. Sayre]] atom:entry attribute values. atom:entry elements MAY contain additional
elements MAY contain additional atom:link elements beyond those atom:link elements beyond those described above.
described above.
o atom:entry elements MUST NOT contain more than one atom:published o atom:entry elements MUST NOT contain more than one atom:published
element. element.
o atom:entry elements MUST NOT contain more than one o atom:entry elements MUST NOT contain more than one atom:source
atom:source-feed element. element.
o atom:entry elements MUST contain an atom:summary element in any of o atom:entry elements MUST contain an atom:summary element in any of
the following cases: [[anchor26: Do these requirements reflect the the following cases:
WG's decisions? --R. Sayre]]
* the atom:entry element contains no atom:content element. * the atom:entry element contains no atom:content element.
[[anchor27: Net result: Atom entries MUST have an atom:summary
or an atom:content element.]]
* the atom:entry contains an atom:content that has a "src" * the atom:entry contains an atom:content that has a "src"
attribute (and is thus empty). attribute (and is thus empty).
* the atom:entry contains content that is encoded in Base64; i.e. * the atom:entry contains content that is encoded in Base64; i.e.
the "type" attribute of atom:content is a MIME media type the "type" attribute of atom:content is a MIME media type
[RFC2045] and does not begin with "text/" nor end with "+xml". [RFC2045] and does not begin with "text/" nor end with "+xml".
o atom:entry elements MUST NOT contain more than one atom:summary o atom:entry elements MUST NOT contain more than one atom:summary
element. element.
o atom:entry elements MUST have exactly one "atom:title" element. o atom:entry elements MUST have exactly one "atom:title" element.
o atom:entry elements MUST contain exactly one atom:updated element. o atom:entry elements MUST contain exactly one atom:updated element.
4.1.3 The "atom:content" Element 4.1.3 The "atom:content" Element
The "atom:content" element either contains or links to the content of The "atom:content" element either contains or links to the content of
the entry. Except for the "type" and "src" attributes, the content the entry. The content of atom:content is language-sensitive.
of atom:content is language-sensitive. atom:entry elements MUST
contain zero or one atom:content elements.
atomInlineTextContent = atomInlineTextContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "text" | "html" | atomMediaType }?, attribute type { "text" | "html" }?,
(text)* (text)*
} }
atomInlineXHTMLContent = atomInlineXHTMLContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { attribute type { "xhtml" },
"xhtml" | xhtmlDiv
atomMediaType }
}?,
atomInlineOtherContent =
element atom:content {
atomCommonAttributes,
attribute type { atomMediaType }?,
(text|anyElement)* (text|anyElement)*
} }
atomOutOfLineContent = atomOutOfLineContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { attribute type { atomMediaType }?,
"text" |
"html" |
"xhtml" |
atomMediaType }?,
attribute src { atomUri }, attribute src { atomUri },
empty empty
} }
atomContent = atomContent = atomInlineTextContent
atomInlineTextContent | | atomInlineXHTMLContent
atomInlineXHTMLContent | | atomInlineOtherContent
atomOutOfLineContent | atomOutOfLineContent
4.1.3.1 The "type" attribute 4.1.3.1 The "type" attribute
atom:content MAY have a "type" attribute. When present, the value atom:content MAY have a "type" attribute. When present, the value
MAY be one of "text", "html", or "xhtml". Failing that, it MUST be a MAY be one of "text", "html", or "xhtml". Failing that, it MUST be a
MIME media type [RFC2045] with a discrete top-level type (see Section MIME media type [RFC2045] with a discrete top-level type (see Section
5 of [RFC2045]). If the type attribute is not provided, Atom 5 of [RFC2045]). If the type attribute is not provided, Atom
Processors MUST behave as though it were present with a value of Processors MUST behave as though it were present with a value of
"text". "text".
skipping to change at page 18, line 17 skipping to change at page 18, line 23
If the "src" attribute is present, the "type" attribute SHOULD be If the "src" attribute is present, the "type" attribute SHOULD be
provided and MUST be a MIME media type [RFC2045], rather than "text", provided and MUST be a MIME media type [RFC2045], rather than "text",
"html", or "xhtml". The value is advisory; that is to say, upon "html", or "xhtml". The value is advisory; that is to say, upon
dereferencing the IRI to retrieve the content, if the server dereferencing the IRI to retrieve the content, if the server
providing that content also provides a media type, the providing that content also provides a media type, the
server-provided media type is authoritative. server-provided media type is authoritative.
If the value of type begins with "text/" or ends with "+xml", the If the value of type begins with "text/" or ends with "+xml", the
content SHOULD be local; that is to say, no "src" attribute should be content SHOULD be local; that is to say, no "src" attribute should be
provided. [[anchor31: J. Reschke: I'm not sure I understand what provided.
this is for. It seems to discourage putting XML data out-of-band.
Why? ... Explaining the issue instead of just trying to enforce it
may lead to better results...]]
4.1.3.3 Processing Model 4.1.3.3 Processing Model
Atom Documents MUST conform to the following rules. Atom Processors Atom Documents MUST conform to the following rules. Atom Processors
MUST interpret atom:content according to the first applicable rule. MUST interpret atom:content according to the first applicable rule.
1. If the value of "type" is "text", the content of atom:content 1. If the value of "type" is "text", the content of atom:content
MUST NOT contain child elements. Such text is intended to be MUST NOT contain child elements. Such text is intended to be
presented to humans in a readable fashion. Thus, Atom Processors presented to humans in a readable fashion. Thus, Atom Processors
MAY display it using normal text rendering techniques such as MAY display it using normal text rendering techniques such as
skipping to change at page 20, line 14 skipping to change at page 20, line 21
atomAuthor = element atom:author { atomPersonConstruct } atomAuthor = element atom:author { atomPersonConstruct }
4.2.2 The "atom:category" Element 4.2.2 The "atom:category" Element
The "atom:category" element conveys information about a category The "atom:category" element conveys information about a category
associated with an entry or feed. associated with an entry or feed.
atomCategory = atomCategory =
element atom:category { element atom:category {
atomCommonAttributes, attribute term { text }, atomCommonAttributes,
attribute term { text },
attribute scheme { atomUri }?, attribute scheme { atomUri }?,
attribute label { text }?, attribute label { text }?,
empty empty
} }
4.2.2.1 The "term" Attribute 4.2.2.1 The "term" Attribute
The "term" attribute is a string that identifies the category to The "term" attribute is a string that identifies the category to
which the entry or feed belongs. Category elements MUST have a which the entry or feed belongs. Category elements MUST have a
"term" attribute. "term" attribute.
skipping to change at page 20, line 44 skipping to change at page 21, line 5
end-user applications. The content of the "label" attribute is end-user applications. The content of the "label" attribute is
language-sensitive. Category elements MAY have a "label" attribute. language-sensitive. Category elements MAY have a "label" attribute.
4.2.3 The "atom:contributor" Element 4.2.3 The "atom:contributor" Element
The "atom:contributor" element is a Person construct that indicates a The "atom:contributor" element is a Person construct that indicates a
person or other entity who contributed to the entry or feed. person or other entity who contributed to the entry or feed.
atomContributor = element atom:contributor { atomPersonConstruct } atomContributor = element atom:contributor { atomPersonConstruct }
4.2.4 The "atom:copyright Element 4.2.4 The "atom:copyright" Element
The "atom:copyright" element is a Text construct that conveys a The "atom:copyright" element is a Text construct that conveys a
human-readable copyright statement for an entry or feed. human-readable copyright statement for an entry or feed.
atomCopyright = element atom:copyright { atomTextContstruct } atomCopyright = element atom:copyright { atomTextConstruct }
The atom:copyright element SHOULD NOT be used to convey The atom:copyright element SHOULD NOT be used to convey
machine-readable licensing information. machine-readable licensing information.
If an atom:entry element does not contain an atom:copyright element, If an atom:entry element does not contain an atom:copyright element,
then the atom:copyright element of the containing atom:feed element's then the atom:copyright element of the containing atom:feed element's
atom:head element, if present, is considered to apply to the entry. atom:head element, if present, is considered to apply to the entry.
4.2.5 The "atom:generator" Element 4.2.5 The "atom:generator" Element
The "atom:generator" element's content identifies the agent used to The "atom:generator" element's content identifies the agent used to
generate a feed, for debugging and other purposes. generate a feed, for debugging and other purposes.
atomGenerator = atomGenerator = element atom:generator {
element atom:generator {
atomCommonAttributes, atomCommonAttributes,
attribute uri { atomUri }?, attribute uri { atomUri }?,
attribute version { text }?, attribute version { text }?,
text text
} }
The content of this element, when present, MUST be a string that is a The content of this element, when present, MUST be a string that is a
human-readable name for the generating agent. human-readable name for the generating agent.
The atom:generator element MAY have a "uri" attribute whose value The atom:generator element MAY have a "uri" attribute whose value
MUST be an IRI reference [RFC3987]. When dereferenced, that IRI MUST be an IRI reference [RFC3987]. When dereferenced, that IRI
SHOULD produce a representation that is relevant to that agent. SHOULD produce a representation that is relevant to that agent.
The atom:generator element MAY have a "version" attribute that The atom:generator element MAY have a "version" attribute that
indicates the version of the generating agent. When present, its indicates the version of the generating agent. When present, its
value is unstructured text. value is unstructured text.
4.2.6 The "atom:icon" Element 4.2.6 The "atom:icon" Element
The "atom:icon" element's content is an IRI [RFC3987] which The "atom:icon" element's content is an IRI reference [RFC3987] which
identifies an image which provides iconic visual identification for a identifies an image which provides iconic visual identification for a
feed. The image SHOULD have an aspect ratio of one (horizontal) to feed.
one (vertical), and should be suitable for presentation at a small
size.
atomIcon = element atom:icon { atomCommonAttributes, (atomUri) } atomIcon = element atom:icon {
atomCommonAttributes,
(atomUri)
}
The image SHOULD have an aspect ratio of one (horizontal) to one
(vertical), and should be suitable for presentation at a small size.
4.2.7 The "atom:id" Element 4.2.7 The "atom:id" Element
[[anchor45: Substantially changed from format-05, review carefully]]
The "atom:id" element conveys a permanent, universally unique The "atom:id" element conveys a permanent, universally unique
identifier for an entry or feed. identifier for an entry or feed.
atomId = element atom:id { atomCommonAttributes, (atomUri) } atomId = element atom:id {
atomCommonAttributes,
(atomUri)
}
Its content MUST be an IRI, as defined by [RFC3987]. Note that the Its content MUST be an IRI, as defined by [RFC3987]. Note that the
definition of "IRI" excludes relative references. Though the IRI definition of "IRI" excludes relative references. Though the IRI
might use a dereferencable scheme, Atom Processors MUST NOT assume it might use a dereferencable scheme, Atom Processors MUST NOT assume it
can be dereferenced. can be dereferenced.
When an Atom document is relocated, migrated, syndicated, When an Atom document is relocated, migrated, syndicated,
republished, exported or imported, the content of its atom:id element republished, exported or imported, the content of its atom:id element
MUST NOT change. Put another way, an atom:id element pertains to all MUST NOT change. Put another way, an atom:id element pertains to all
instantiations of a particular Atom entry or feed; revisions retain instantiations of a particular Atom entry or feed; revisions retain
the same content in their atom:id elements. the same content in their atom:id elements. It is suggested that the
atom:id element be stored along with the associated resource.
The content of an atom:id element MUST be created in a way that The content of an atom:id element MUST be created in a way that
assures uniqueness; it is suggested that the atom:id element be assures uniqueness.
stored along with the associated resource.
Because of the risk of confusion between IRIs that would be Because of the risk of confusion between IRIs that would be
equivalent if dereferenced, the following normalization strategy is equivalent if dereferenced, the following normalization strategy is
strongly encouraged when generating atom:id elements: strongly encouraged when generating atom:id elements:
o Provide the scheme in lowercase characters. o Provide the scheme in lowercase characters.
o Provide the host, if any, in lowercase characters. o Provide the host, if any, in lowercase characters.
o Only perform percent-encoding where it is essential. o Only perform percent-encoding where it is essential.
o Use uppercase A-through-F characters when percent-encoding. o Use uppercase A-through-F characters when percent-encoding.
o Prevent dot-segments appearing in paths. o Prevent dot-segments appearing in paths.
skipping to change at page 23, line 29 skipping to change at page 23, line 38
http://www.example.com/~bob http://www.example.com/~bob
http://www.example.com/%7ebob http://www.example.com/%7ebob
http://www.example.com/%7Ebob http://www.example.com/%7Ebob
are three distinct identifiers, because IRI %-escaping is significant are three distinct identifiers, because IRI %-escaping is significant
for the purposes of comparison. for the purposes of comparison.
4.2.8 The "atom:image" Element 4.2.8 The "atom:image" Element
The "atom:image" element's content is an IRI [RFC3987] which The "atom:image" element's content is an IRI reference [RFC3987]
identifies an image which provides visual identification for a feed. which identifies an image which provides visual identification for a
feed.
atomImage = element atom:image {
atomCommonAttributes,
(atomUri)
}
The image SHOULD have an aspect ratio of 2 (horizontal) to 1 The image SHOULD have an aspect ratio of 2 (horizontal) to 1
(vertical). (vertical).
atomImage = element atom:image { atomCommonAttributes, (atomUri) }
4.2.9 The "atom:link" Element 4.2.9 The "atom:link" Element
The "atom:link" element is an empty element that defines a reference The "atom:link" element is an empty element that defines a reference
from an entry or feed to a Web resource. from an entry or feed to a Web resource.
atomLink = atomLink =
element atom:link { element atom:link {
atomCommonAttributes, atomCommonAttributes,
attribute href { atomUri }, attribute href { atomUri },
attribute rel { atomNCName | atomUri }?, attribute rel { atomNCName | atomUri }?,
skipping to change at page 24, line 12 skipping to change at page 24, line 28
attribute length { text }?, attribute length { text }?,
empty empty
} }
4.2.9.1 The "href" Attribute 4.2.9.1 The "href" Attribute
The "href" attribute contains the link's IRI. atom:link elements The "href" attribute contains the link's IRI. atom:link elements
MUST have a href attribute, whose value MUST be a IRI reference MUST have a href attribute, whose value MUST be a IRI reference
[RFC3987]. [RFC3987].
xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the
href attribute's content.
4.2.9.2 The "rel" Attribute 4.2.9.2 The "rel" Attribute
atom:link elements MAY have an "rel" attribute that indicates the atom:link elements MAY have a "rel" attribute that indicates the link
link relation type. If the "rel" attribute is not present, the link relation type. If the "rel" attribute is not present, the link
element MUST be interpreted as if the link relation type is element MUST be interpreted as if the link relation type is
"alternate". "alternate".
rel_attribute = segment-nz-nc / IRI ABNF for the "rel" attribute:
The value of "rel" MUST be either a name that is non-empty and does rel_attribute = isegment-nz-nc / IRI
not contain any colon (":") characters, or a IRI [RFC3987]. Note
that use of a relative reference is not allowed. If a name is given, The value of "rel" MUST be string that is non-empty, does not contain
implementations MUST consider the link relation type to be equivalent any colon (":") characters, and matches the "isegment-nz-nc" or "IRI"
to the same name registered within the IANA Registry of Link ABNF forms in [RFC3987]. Note that use of a relative reference is
Relations Section 7, and thus the IRI that would be obtained by not allowed. If a name is given, implementations MUST consider the
appending the value of the rel attribute to the string link relation type to be equivalent to the same name registered
"http://www.iana.org/assignments/relation/". The value of "rel" within the IANA Registry of Link Relations Section 7, and thus the
describes the meaning of the link, but does not impose any behavioral IRI that would be obtained by appending the value of the rel
requirements on implementations. attribute to the string "http://www.iana.org/assignments/relation/".
The value of "rel" describes the meaning of the link, but does not
impose any behavioral requirements on implementations.
This document defines five initial values for the Registry of Link This document defines five initial values for the Registry of Link
Relations: Relations:
The value "alternate" signifies that the IRI in the value of the href 1. The value "alternate" signifies that the IRI in the value of the
attribute identifies an alternate version of the resource described href attribute identifies an alternate version of the resource
by the containing element. described by the containing element.
The value "related" signifies that the IRI in the value of the href 2. The value "related" signifies that the IRI in the value of the
attribute identifies a resource related to the resource described by href attribute identifies a resource related to the resource
the containing element. For example, the feed for a site that described by the containing element. For example, the feed for a
discusses the performance of the search engine at site that discusses the performance of the search engine at
"http://search.example.com" might contain, as a child of atom:feed: "http://search.example.com" might contain, as a child of
atom:feed:
<link rel="related" href="http://search.example.com/"> <link rel="related" href="http://search.example.com/">
An identical link might appear as a child of any atom:entry whose An identical link might appear as a child of any atom:entry whose
content contains a discussion of that same search engine. content contains a discussion of that same search engine.
The value "self" signifies that the IRI in the value of the href 3. The value "self" signifies that the IRI in the value of the href
attribute identifies a resource equivalent to the containing element. attribute identifies a resource equivalent to the containing
element.
The value "enclosure" signifies that the IRI in the value of the href 4. The value "enclosure" signifies that the IRI in the value of the
attribute identifies a related resource which is potentially large in href attribute identifies a related resource which is potentially
size and may require special handling by consuming software. For large in size and may require special handling by consuming
Link constructs with rel="enclosure", the length attribute SHOULD be software. For Link elements with rel="enclosure", the length
provided. attribute SHOULD be provided.
The value "via" signifies that the IRI in the value of the href 5. The value "via" signifies that the IRI in the value of the href
attribute identifies a resource that is the source of the information attribute identifies a resource that is the source of the
provided in the containing element. information provided in the containing element.
4.2.9.3 The "type" Attribute 4.2.9.3 The "type" Attribute
Link elements MAY have a type attribute, whose value MUST conform to The "type" attribute's value is an advisory media type; it is a hint
the syntax of a MIME media type [RFC2045].
The type attribute's value is an advisory media type; it is a hint
about the type of the representation that is expected to be returned about the type of the representation that is expected to be returned
when the value of the href attribute is dereferenced. Note that the when the value of the href attribute is dereferenced. Note that the
type attribute does not override the actual media type returned with type attribute does not override the actual media type returned with
the representation. the representation. Link elements MAY have a type attribute, whose
value MUST conform to the syntax of a MIME media type [RFC2045].
4.2.9.4 The "hreflang" Attribute 4.2.9.4 The "hreflang" Attribute
The "hreflang" attribute's content describes the language of the The "hreflang" attribute's content describes the language of the
resource pointed to by the href attribute. When used together with resource pointed to by the href attribute. When used together with
the rel="alternate", it implies a translated version of the entry. the rel="alternate", it implies a translated version of the entry.
Link elements MAY have an hreflang attribute, whose value MUST be a Link elements MAY have an hreflang attribute, whose value MUST be a
language tag [RFC3066]. language tag [RFC3066].
4.2.9.5 The "title" Attribute 4.2.9.5 The "title" Attribute
skipping to change at page 25, line 51 skipping to change at page 26, line 18
link. The content of the "title" attribute is language sensitive. link. The content of the "title" attribute is language sensitive.
Link elements MAY have a title attribute. Link elements MAY have a title attribute.
4.2.9.6 The "length" Attribute 4.2.9.6 The "length" Attribute
The "length" attribute indicates an advisory length of the linked The "length" attribute indicates an advisory length of the linked
content in octets; it is a hint about the content length of the content in octets; it is a hint about the content length of the
representation returned when the IRI in the href attribute is representation returned when the IRI in the href attribute is
dereferenced. Note that the length attribute does not override the dereferenced. Note that the length attribute does not override the
actual content length of the representation as reported by the actual content length of the representation as reported by the
underlying protocol. underlying protocol. Link elements MAY have a length attribute.
Link elements MAY have a length attribute.
4.2.10 The "atom:published" Element 4.2.10 The "atom:published" Element
The "atom:published" element is a Date construct indicating an The "atom:published" element is a Date construct indicating an
instant in time associated with an event early in the life cycle of instant in time associated with an event early in the life cycle of
the entry. Typically, atom:published will be associated with the the entry.
initial creation or first availability of the resource.
atomPublished = element atom:published { atomDateConstruct } atomPublished = element atom:published { atomDateConstruct }
4.2.11 The "atom:source-feed" Element Typically, atom:published will be associated with the initial
creation or first availability of the resource.
4.2.11 The "atom:source" Element
If an atom:entry is copied from one feed into another feed, then the If an atom:entry is copied from one feed into another feed, then the
source atom:feed's metadata (all child elements of atom:feed other source atom:feed's metadata (all child elements of atom:feed other
than the atom:entry elements) MAY be preserved within the copied than the atom:entry elements) MAY be preserved within the copied
entry by adding an atom:source-feed child element, if it is not entry by adding an atom:source child element, if it is not already
already present in the entry, and including some or all of the source present in the entry, and including some or all of the source feed's
feed's metadata elements as the atom:source-feed element's children. metadata elements as the atom:source element's children. Such
Such metadata SHOULD be preserved if the source atom:feed contains metadata SHOULD be preserved if the source atom:feed contains any of
any of the child elements atom:author, atom:contributor, the child elements atom:author, atom:contributor, atom:copyright, or
atom:copyright, or atom:category and those child elements are not atom:category and those child elements are not present in the source
present in the source atom:entry. atom:entry.
atomSourceFeed = atomSource =
element atom:source-feed { element atom:source {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor?
& atomCategory* & atomCategory*
& atomContributor* & atomContributor*
& atomCopyright? & atomCopyright?
& atomGenerator? & atomGenerator?
& atomIcon? & atomIcon?
& atomId? & atomId?
& atomImage? & atomImage?
& atomLink+ & atomLink+
& atomSubtitle? & atomSubtitle?
& atomTitle & atomTitle
& atomUpdated & atomUpdated
& anyElement* ) & extensionElement*)
} }
4.2.12 The "atom:subtitle" Element 4.2.12 The "atom:subtitle" Element
The "atom:subtitle" element is a Text construct that conveys a The "atom:subtitle" element is a Text construct that conveys a
human-readable description or subtitle for a feed. human-readable description or subtitle for a feed.
atomSubtitle = element atom:subtitle { atomTextConstruct } atomSubtitle = element atom:subtitle { atomTextConstruct }
4.2.13 The "atom:summary" Element 4.2.13 The "atom:summary" Element
skipping to change at page 28, line 22 skipping to change at page 29, line 22
The root of an Atom document (i.e., atom:feed in an Atom Feed The root of an Atom document (i.e., atom:feed in an Atom Feed
Document, atom:entry in an Atom Entry Document) MAY have an Enveloped Document, atom:entry in an Atom Entry Document) MAY have an Enveloped
Signature, as described by XML-Signature and Syntax Processing Signature, as described by XML-Signature and Syntax Processing
[W3C.REC-xmldsig-core-20020212]. [W3C.REC-xmldsig-core-20020212].
Processors MUST NOT reject an Atom Document containing such a Processors MUST NOT reject an Atom Document containing such a
signature because they are not capable of verifying it; they MUST signature because they are not capable of verifying it; they MUST
continue processing and MAY inform the user of their failure to continue processing and MAY inform the user of their failure to
validate the signature. validate the signature.
In other words, the presence of an element with the namespace IRI In other words, the presence of an element with the namespace URI
"http://www.w3.org/2000/09/xmldsig#" and a local name of "Signature" "http://www.w3.org/2000/09/xmldsig#" and a local name of "Signature"
as a child of the document element must not cause an Atom Processor as a child of the document element must not cause an Atom Processor
to fail merely because of its presence. to fail merely because of its presence.
Other elements in an Atom Document MUST NOT be signed unless their Other elements in an Atom Document MUST NOT be signed unless their
definitions explicitly specify such a capability. definitions explicitly specify such a capability.
5.2 Encryption 5.2 Encryption
The root of an Atom Document (i.e., atom:feed in an Atom Feed The root of an Atom Document (i.e., atom:feed in an Atom Feed
skipping to change at page 29, line 22 skipping to change at page 30, line 22
the inclusion of arbitrary foreign markup. the inclusion of arbitrary foreign markup.
6.2 Extensions To the Atom Vocabulary 6.2 Extensions To the Atom Vocabulary
Future versions of this specification may add new elements and Future versions of this specification may add new elements and
attributes to the Atom markup vocabulary. Software written to attributes to the Atom markup vocabulary. Software written to
conform to this version of the specification will not be able to conform to this version of the specification will not be able to
process such markup correctly and, in fact, will not be able to process such markup correctly and, in fact, will not be able to
distinguish it from markup error. For the purposes of this distinguish it from markup error. For the purposes of this
discussion, unrecognized markup from the Atom vocabulary will be discussion, unrecognized markup from the Atom vocabulary will be
considered "foreign "markup". considered "foreign markup".
Unlike markup from other vocabularies, foreign markup from the Atom
vocabulary MAY appear at any location in an Atom document.
6.3 Software Processing of Foreign Markup 6.3 Software Processing of Foreign Markup
Software processing an Atom Document which encounters foreign markup Software processing an Atom Document which encounters foreign markup
in a location that is legal according to this specification MUST NOT in a location that is legal according to this specification MUST NOT
stop processing or signal an error. It may be the case that the stop processing or signal an error. It may be the case that the
software is able to process the foreign markup correctly and does so. software is able to process the foreign markup correctly and does so.
Otherwise, such markup is termed "unknown foreign markup". Otherwise, such markup is termed "unknown foreign markup".
When unknown foreign markup is encountered as a child of atom:entry, When unknown foreign markup is encountered as a child of atom:entry,
atom:feed, or a Person Construct, software MAY [[anchor67: Changed to atom:feed, or a Person construct, software MAY bypass the markup and
MAY from SHOULD. Republishers might want to copy it. --R. Sayre]] any textual content and MUST NOT change its behavior as a result of
bypass the markup and any textual content and MUST NOT change its the markup's presence.
behavior as a result of the markup's presence.
When unknown foreign markup is encountered in a Text Contruct or When unknown foreign markup is encountered in a Text Contruct or
atom:content element, software SHOULD ignore the markup and process atom:content element, software SHOULD ignore the markup and process
any text content of foreign elements as though the surrounding markup any text content of foreign elements as though the surrounding markup
were not present. were not present.
6.4 Extension Elements 6.4 Extension Elements
Atom allows foreign markup anywhere in an Atom document. Child Atom allows foreign markup anywhere in an Atom document. Child
elements of atom:entry and atom:feed are considered "metadata" elements of atom:entry, atom:feed, and Person constructs are
elements, and are described below. Child elements of Person considered Metadata Elements, and are described below. Child
Constructs are considered to apply to the construct. The role of elements of Person constructs are considered to apply to the
other foreign markup is undefined by this specification. construct. The role of other foreign markup is undefined by this
specification.
6.4.1 Simple Extension Elements 6.4.1 Simple Extension Elements
A Simple Extension element MUST NOT have any attributes or child A Simple Extension element MUST NOT have any attributes or child
elements. The element MAY contain either character data, or be elements. The element MAY contain character data, or be empty.
empty. Simple Extension elements are not language-sensitive.
The element can be interpreted as a simple property (or name/value The element can be interpreted as a simple property (or name/value
pair) of the parent element that encloses it. The pair consisting of pair) of the parent element that encloses it. The pair consisting of
the namespace-URI of the element and the local name of the element the namespace-URI of the element and the local name of the element
can be interpreted as the name of the property. The character data can be interpreted as the name of the property. The character data
content of the element can be interpreted as the value of the content of the element can be interpreted as the value of the
property. If the element is empty, then the property value can be property. If the element is empty, then the property value can be
interpreted as an empty string. interpreted as an empty string.
6.4.2 Structured Extension Elements 6.4.2 Structured Extension Elements
The root element of a Structured Extension element MUST have at least The root element of a Structured Extension element MUST have at least
one attribute or child element. It MAY have attributes, it MAY one attribute or child element. It MAY have attributes, it MAY
contain well-formed XML content (including character data), or it MAY contain well-formed XML content (including character data), or it MAY
be empty. be empty. Structured Extension elements are language-sensitive.
The structure of a Structured Extension element, including the order The structure of a Structured Extension element, including the order
of its child elements, could be significant. of its child elements, could be significant.
This specification does not provide an interpretation of a Structured This specification does not provide an interpretation of a Structured
Extension element. The syntax of the XML contained in the element, Extension element. The syntax of the XML contained in the element,
and an interpretation of how the element relates to its containing and an interpretation of how the element relates to its containing
element is defined by the specification of the Atom extension. element is defined by the specification of the Atom extension.
7. IANA Considerations 7. IANA Considerations
skipping to change at page 31, line 20 skipping to change at page 32, line 20
MIME media type name: application MIME media type name: application
MIME subtype name: atom+xml MIME subtype name: atom+xml
Mandatory parameters: None. Mandatory parameters: None.
Optional parameters: Optional parameters:
"charset": This parameter has identical semantics to the charset "charset": This parameter has identical semantics to the charset
parameter of the "application/xml" media type as specified in parameter of the "application/xml" media type as specified in
[RFC3023]. [RFC3023].
Encoding considerations: Identical to those of "application/xml" as Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023], section 3.2. described in [RFC3023], section 3.2.
Security considerations: As defined in this specification. Security considerations: As defined in this specification.
[[anchor71: update upon publication]] [[anchor59: update upon publication]]
In addition, as this media type uses the "+xml" convention, it In addition, as this media type uses the "+xml" convention, it
shares the same security considerations as described in [RFC3023], shares the same security considerations as described in [RFC3023],
section 10. section 10.
Interoperability considerations: There are no known interoperability Interoperability considerations: There are no known interoperability
issues. issues.
Published specification: This specification. [[anchor72: update upon Published specification: This specification. [[anchor60: update upon
publication]] publication]]
Applications that use this media type: No known applications Applications that use this media type: No known applications
currently use this media type. currently use this media type.
Additional information: Additional information:
Magic number(s): As specified for "application/xml" in [RFC3023], Magic number(s): As specified for "application/xml" in [RFC3023],
section 3.2. section 3.2.
File extension: .atom File extension: .atom
Fragment identifiers: As specified for "application/xml" in Fragment identifiers: As specified for "application/xml" in
[RFC3023], section 5. [RFC3023], section 5.
Base URI: As specified in [RFC3023], section 6. Base URI: As specified in [RFC3023], section 6.
Macintosh File Type code: TEXT Macintosh File Type code: TEXT
Person and email address to contact for further information: Mark Person and email address to contact for further information: Mark
Nottingham <mnot@pobox.com> Nottingham <mnot@pobox.com>
Intended usage: COMMON Intended usage: COMMON
Author/Change controller: This specification's author(s). Author/Change controller: This specification's author(s).
[[anchor73: update upon publication]] [[anchor61: update upon publication]]
7.1 Registry of Link Relations 7.1 Registry of Link Relations
This registry is maintained by IANA and initially contains five This registry is maintained by IANA and initially contains five
values: "alternate", "related", "self", "enclosure", and "via". New values: "alternate", "related", "self", "enclosure", and "via". New
assignments are subject to IESG Approval, as outlined in [RFC2434]. assignments are subject to IESG Approval, as outlined in [RFC2434].
Requests should be made by email to IANA, which will then forward the Requests should be made by email to IANA, which will then forward the
request to the IESG requesting approval. The request should contain request to the IESG requesting approval. The request should contain
discussion of at least the following five topics: discussion of at least the following five topics:
skipping to change at page 33, line 9 skipping to change at page 34, line 9
given in Section 4.2.9.2 given in Section 4.2.9.2
o Common name for link type. o Common name for link type.
o Description of link type semantics. o Description of link type semantics.
o Expected display characteristics. o Expected display characteristics.
o Security considerations. o Security considerations.
8. Security Considerations 8. Security Considerations
8.1 HTML and XHTML Content 8.1 HTML and XHTML Content
Text Constructs and atom:content allow the delivery of HTML and XHTML Text constructs and atom:content allow the delivery of HTML and XHTML
to receiving software, which may process it. Many elements in these to receiving software, which may process it. Many elements in these
languages are considered 'unsafe' in that they open clients to one or languages are considered 'unsafe' in that they open clients to one or
more types of attack. Implementers of software which processes Atom more types of attack. Implementers of software which processes Atom
should carefully consider their handling of every type of element should carefully consider their handling of every type of element
when processing incoming (X)HTML in Atom documents. See the security when processing incoming (X)HTML in Atom documents. See the security
sections of RFC 2854 and HTML 4.01 for guidance. sections of [RFC2854] and [W3C.REC-html401-19991224] for guidance.
Atom Processors should pay particular attention to the security of Atom Processors should pay particular attention to the security of
the IMG, SCRIPT, EMBED, OBJECT, FRAME, FRAMESET, IFRAME, META, and the IMG, SCRIPT, EMBED, OBJECT, FRAME, FRAMESET, IFRAME, META, and
LINK elements, but other elements may also have negative security LINK elements, but other elements may also have negative security
properties. properties.
(X)HTML can either directly contain or indirectly reference (X)HTML can either directly contain or indirectly reference
executable content. executable content.
8.2 URIs 8.2 URIs
Atom Processors handle URIs. See Section 7 of [RFC3986]. Atom Processors handle URIs. See Section 7 of [RFC3986].
8.3 IRIs 8.3 IRIs
Atom Processors handle IRIs. See Section 8 of [RFC3987]. Atom Processors handle IRIs. See Section 8 of [RFC3987].
8.4 Encryption and Signing 8.4 Encryption and Signing
Atom document can be encrypted and signed using Atom documents can be encrypted and signed using
[W3C.REC-xmlenc-core-20021210] and [W3C.REC-xmldsig-core-20020212], [W3C.REC-xmlenc-core-20021210] and [W3C.REC-xmldsig-core-20020212],
respectively, and is subject to the security considerations implied respectively, and are subject to the security considerations implied
by their use. by their use.
9. References 9. References
9.1 Normative References 9.1 Normative References
[Atom-autodiscovery] [Atom-autodiscovery]
Pilgrim, M., "Atom Feed Autodiscovery", work-in-progress, Pilgrim, M., "Atom Feed Autodiscovery", work-in-progress,
August 2004. August 2004.
[ISO.8601.1988]
International Organization for Standardization, "Data
elements and interchange formats - Information interchange
- Representation of dates and times", ISO Standard 8601,
June 1988.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996. Bodies", RFC 2045, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
2001. 2001.
[RFC2854] Connolly, D. and L. Masinter, "The 'text/html' Media
Type", RFC 2854, June 2000.
[RFC3023] Murata, M., St. Laurent, S. and D. Kohn, "XML Media [RFC3023] Murata, M., St. Laurent, S. and D. Kohn, "XML Media
Types", RFC 3023, January 2001. Types", RFC 3023, January 2001.
[RFC3066] Alvestrand, H., "Tags for the Identification of [RFC3066] Alvestrand, H., "Tags for the Identification of
Languages", BCP 47, RFC 3066, January 2001. Languages", BCP 47, RFC 3066, January 2001.
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, July 2002. Timestamps", RFC 3339, July 2002.
[RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC3548] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 3548, July 2003. Encodings", RFC 3548, July 2003.
[RFC3986] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005. Identifiers (IRIs)", RFC 3987, January 2005.
[W3C.NOTE-datetime-19980827]
Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C
NOTE NOTE-datetime-19980827, August 1998.
[W3C.REC-html401-19991224] [W3C.REC-html401-19991224]
Raggett, D., Hors, A. and I. Jacobs, "HTML 4.01 Raggett, D., Hors, A. and I. Jacobs, "HTML 4.01
Specification", W3C REC REC-html401-19991224, December Specification", W3C REC REC-html401-19991224, December
1999. 1999.
[W3C.REC-xhtml-basic-20001219] [W3C.REC-xhtml-basic-20001219]
Baker, M., Ishikawa, M., Matsui, S., Stark, P., Wugofski, Baker, M., Ishikawa, M., Matsui, S., Stark, P., Wugofski,
T. and T. Yamakami, "XHTML Basic", W3C T. and T. Yamakami, "XHTML Basic", W3C
REC REC-xhtml-basic-20001219, December 2000. REC REC-xhtml-basic-20001219, December 2000.
skipping to change at page 35, line 41 skipping to change at page 36, line 38
[W3C.REC-xmldsig-core-20020212] [W3C.REC-xmldsig-core-20020212]
Solo, D., Reagle, J. and D. Eastlake, "XML-Signature Solo, D., Reagle, J. and D. Eastlake, "XML-Signature
Syntax and Processing", W3C REC REC-xmldsig-core-20020212, Syntax and Processing", W3C REC REC-xmldsig-core-20020212,
February 2002. February 2002.
[W3C.REC-xmlenc-core-20021210] [W3C.REC-xmlenc-core-20021210]
Reagle, J. and D. Eastlake, "XML Encryption Syntax and Reagle, J. and D. Eastlake, "XML Encryption Syntax and
Processing", W3C REC REC-xmlenc-core-20021210, December Processing", W3C REC REC-xmlenc-core-20021210, December
2002. 2002.
[W3C.REC-xmlschema-2-20041028]
Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
Second Edition", W3C REC REC-xmlschema-2-20041028, October
2004.
9.2 Informative References 9.2 Informative References
[ISO.8601.1988]
International Organization for Standardization, "Data
elements and interchange formats - Information interchange
- Representation of dates and times", ISO Standard 8601,
June 1988.
[RELAX-NG] [RELAX-NG]
OASIS Technical Committee: RELAX NG, "RELAX NG OASIS Technical Committee: RELAX NG, "RELAX NG
Specification", December 2001. Specification", December 2001.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434, IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998. October 1998.
[W3C.NOTE-datetime-19980827]
Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C
NOTE NOTE-datetime-19980827, August 1998.
[W3C.REC-xmlschema-2-20041028]
Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
Second Edition", W3C REC REC-xmlschema-2-20041028, October
2004.
Authors' Addresses Authors' Addresses
Mark Nottingham (editor) Mark Nottingham (editor)
Email: mnot@pobox.com Email: mnot@pobox.com
URI: http://www.mnot.net/ URI: http://www.mnot.net/
Robert Sayre (editor) Robert Sayre (editor)
Boswijck Memex Consulting
Email: rfsayre@boswijck.com Email: rfsayre@boswijck.com
URI: http://boswijck.com URI: http://boswijck.com
Appendix A. Contributors Appendix A. Contributors
The following people contributed to preliminary drafts of this The following people contributed to preliminary drafts of this
document: Tim Bray, Mark Pilgrim, and Sam Ruby. Norman Walsh document: Tim Bray, Mark Pilgrim, and Sam Ruby. Norman Walsh
provided the Relax NG schema. The content and concepts within are a provided the Relax NG schema. The content and concepts within are a
product of the Atom community and the Atom Publishing Format and product of the Atom community and the Atom Publishing Format and
Protocol Working Group. Protocol Working Group.
Appendix B. Collected RELAX NG Compact Schema Appendix B. Collected RELAX NG Compact Schema
This appendix is informative. This appendix is informative.
# -*- Relax NG -*- # -*- rnc -*-
# RELAX NG Compact Syntax Grammar for the
namespace local = "" # Atom Format Specification Version 07
namespace
atom = "http://purl.org/atom/ns#draft-ietf-atompub-format-06"
namespace atom =
"http://purl.org/atom/ns#draft-ietf-atompub-format-07"
namespace xhtml = "http://www.w3.org/1999/xhtml"
namespace s = "http://www.ascc.net/xml/schematron" namespace s = "http://www.ascc.net/xml/schematron"
start = atomFeed | atomEntry start = atomFeed | atomEntry
## Attribute definitions # Common attributes
atomCommonAttributes = atomCommonAttributes =
attribute xml:base { atomUri }?, attribute xml:base { atomUri }?,
attribute xml:lang { atomLanguageTag }? attribute xml:lang { atomLanguageTag }?
## Common Atom Constructs # Text Constructs
atomPlainTextConstruct = atomPlainTextConstruct =
atomCommonAttributes, atomCommonAttributes,
attribute type { "TEXT" | "HTML" }?, attribute type { "text" | "html" }?,
text text
atomXHTMLTextConstruct = atomXHTMLTextConstruct =
atomCommonAttributes, atomCommonAttributes,
attribute type { "XHTML" }, attribute type { "xhtml" },
(text|anyElement)* xhtmlDiv
atomTextConstruct = atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct
atomPlainTextConstruct | atomXHTMLTextConstruct
# Person Construct
atomPersonConstruct = atomPersonConstruct =
atomCommonAttributes, atomCommonAttributes,
(element atom:name { text } (element atom:name { text }
& element atom:uri { atomUri }? & element atom:uri { atomUri }?
& element atom:email { atomEmailAddress }?) & element atom:email { atomEmailAddress }?
& extensionElement*)
# Date Construct
atomDateConstruct = atomDateConstruct =
atomCommonAttributes, atomCommonAttributes,
xsd:dateTime xsd:dateTime
## Container elements
# atom:feed
# TODO: Test for multiple atom:link/@rel='alternate' with
# the same @type The following tests are simple to do,
# but my validator is giving me trouble.
# TODO: Debug and add them back
# Test for at least one atom:link/@rel='alternate'
# Test for atom:author or all atom:entry have atom:author
# atom:feed # atom:feed
atomFeed = atomFeed =
[ [
s:rule [ s:rule [
context = "atom:feed" context = "atom:feed"
s:assert [ s:assert [
test = "atom:link[@rel='alternate']" test = "atom:link[@rel='alternate']"
"An atom:feed must have at least one link element "An atom:feed must have at least one link element "
with a rel attribute of 'alternate'." ~ "with a rel attribute of 'alternate'."
] ]
] ]
s:rule [ s:rule [
context = "atom:feed" context = "atom:feed"
s:assert [ s:assert [
test = "atom:author or not(../atom:entry[count(atom:author) = 0])" test = "atom:author or not(atom:entry[not(atom:author)])"
"An atom:feed must have an atom:author unless all of "An atom:feed must have an atom:author unless all "
its atom:entry children have an atom:author." ~ "of its atom:entry children have an atom:author."
] ]
] ]
] ]
element atom:feed { element atom:feed {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor?
& atomCategory* & atomCategory*
& atomContributor* & atomContributor*
& atomCopyright? & atomCopyright?
& atomGenerator? & atomGenerator?
& atomIcon? & atomIcon?
& atomId? & atomId?
& atomImage? & atomImage?
skipping to change at page 39, line 50 skipping to change at page 40, line 41
& atomContributor* & atomContributor*
& atomCopyright? & atomCopyright?
& atomGenerator? & atomGenerator?
& atomIcon? & atomIcon?
& atomId? & atomId?
& atomImage? & atomImage?
& atomLink+ & atomLink+
& atomSubtitle? & atomSubtitle?
& atomTitle & atomTitle
& atomUpdated & atomUpdated
& anyElement* ), & extensionElement*),
atomEntry* atomEntry*
} }
# atom:entry # atom:entry
# TODO: Test for multiple atom:link @rel='alternate'
# with the same @type
# TODO: Test for required atom:summary
atomEntry = atomEntry =
[ [
s:rule [ s:rule [
context = "atom:entry" context = "atom:entry"
s:assert [ s:assert [
test = "atom:link[@rel='alternate']" test = "atom:link[@rel='alternate'] or atom:content"
"An atom:entry must have at least one link element "An atom:entry must have at least one link element "
with a rel attribute of 'alternate'." ~ "with a rel attribute of 'alternate' or content."
] ]
] ]
s:rule [ s:rule [
context = "atom:entry" context = "atom:entry"
s:assert [ s:assert [
test = "atom:author or ../atom:author" test = "atom:author or "
"An atom:entry must have an atom:author ~ "../atom:author or atom:source/atom:author"
if the parent atom:feed does not." "An atom:entry must have an atom:author "
~ "if its feed does not."
] ]
] ]
# N.B. This rule doesn't test
# for content with a non-binary type.
s:rule [
context = "atom:entry"
s:assert [
test = "atom:summary or atom:content[not(@src)]"
"An atom:entry must have an atom:summary "
~ "if the atom:content element is empty."
]
]
] ]
element atom:entry { element atom:entry {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor?
& atomCategory* & atomCategory*
& atomContent? & atomContent?
& atomContributor* & atomContributor*
& atomCopyright? & atomCopyright?
& atomId & atomId
& atomLink* & atomLink*
& atomPublished? & atomPublished?
skipping to change at page 40, line 42 skipping to change at page 41, line 40
element atom:entry { element atom:entry {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor?
& atomCategory* & atomCategory*
& atomContent? & atomContent?
& atomContributor* & atomContributor*
& atomCopyright? & atomCopyright?
& atomId & atomId
& atomLink* & atomLink*
& atomPublished? & atomPublished?
& atomSourceFeed? & atomSource?
& atomSummary? & atomSummary?
& atomTitle & atomTitle
& atomUpdated & & atomUpdated
anyElement*) & extensionElement*)
} }
# atom:content # atom:content
atomInlineTextContent = atomInlineTextContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "text | "html" | atomMediaType }?, attribute type { "text" | "html" }?,
(text)* (text)*
} }
atomInlineXHTMLContent = atomInlineXHTMLContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "xhtml" | atomMediaType }?, attribute type { "xhtml" },
xhtmlDiv
}
atomInlineOtherContent =
element atom:content {
atomCommonAttributes,
attribute type { atomMediaType }?,
(text|anyElement)* (text|anyElement)*
} }
atomOutOfLineContent = atomOutOfLineContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "text" | "html" | "xhtml" | atomMediaType }?, attribute type { atomMediaType }?,
attribute src { atomUri }, attribute src { atomUri },
empty empty
} }
atomContent = atomInlineTextContent atomContent = atomInlineTextContent
| atomInlineXHTMLContent | atomInlineXHTMLContent
| atomInlineOtherContent
| atomOutOfLineContent | atomOutOfLineContent
## Metadata Elements
# atom:author # atom:author
atomAuthor = element atom:author { atomPersonConstruct } atomAuthor = element atom:author { atomPersonConstruct }
# atom:category # atom:category
atomCategory = element atom:category { atomCategory =
element atom:category {
atomCommonAttributes, atomCommonAttributes,
attribute term { text }, attribute term { text },
attribute scheme { atomUri }?, attribute scheme { atomUri }?,
attribute label { text }?, attribute label { text }?,
empty empty
} }
# atom:contributor # atom:contributor
atomContributor = element atom:contributor { atomPersonConstruct } atomContributor = element atom:contributor { atomPersonConstruct }
skipping to change at page 42, line 21 skipping to change at page 43, line 21
atomGenerator = element atom:generator { atomGenerator = element atom:generator {
atomCommonAttributes, atomCommonAttributes,
attribute uri { atomUri }?, attribute uri { atomUri }?,
attribute version { text }?, attribute version { text }?,
text text
} }
# atom:icon # atom:icon
atomIcon = element atom:icon { atomCommonAttributes, (atomUri) } atomIcon = element atom:icon {
atomCommonAttributes,
(atomUri)
}
# atom:id # atom:id
atomId = element atom:id { } atomId = element atom:id {
atomCommonAttributes,
(atomUri)
}
# atom:image # atom:image
atomImage = element atom:image { atomCommonAttributes, (atomUri) } atomImage = element atom:image {
atomCommonAttributes,
(atomUri)
}
# atom:link # atom:link
atomLink = element atom:link { atomLink =
element atom:link {
atomCommonAttributes, atomCommonAttributes,
attribute href { atomUri }, attribute href { atomUri },
attribute rel { atomNCName | atomUri }?, attribute rel { atomNCName | atomUri }?,
attribute type { atomMediaType }?, attribute type { atomMediaType }?,
attribute hreflang { atomLanguageTag }?, attribute hreflang { atomLanguageTag }?,
attribute title { text }?, attribute title { text }?,
attribute length { text }?, attribute length { text }?,
empty empty
} }
# atom:published # atom:published
atomPublished = element atom:published { atomDateConstruct } atomPublished = element atom:published { atomDateConstruct }
# atom:source-feed # atom:source
atomSourceFeed = atomSource =
element atom:source-feed { element atom:source {
atomCommonAttributes, atomCommonAttributes,
( atomTitle (atomAuthor?
& atomUpdated & atomCategory*
& atomLink+
& atomIcon
& atomId?
& atomImage?
& atomSubtitle?
& atomAuthor?
& atomContributor* & atomContributor*
& atomCopyright? & atomCopyright?
& atomCategory*
& atomGenerator? & atomGenerator?
& anyElement* ) & atomIcon?
& atomId?
& atomImage?
& atomLink+
& atomSubtitle?
& atomTitle
& atomUpdated
& extensionElement*)
} }
# atom:subtitle # atom:subtitle
atomSubtitle = element atom:subtitle { atomTextConstruct } atomSubtitle = element atom:subtitle { atomTextConstruct }
# atom:summary # atom:summary
atomSummary = element atom:summary { atomTextConstruct } atomSummary = element atom:summary { atomTextConstruct }
# atom:title # atom:title
atomTitle = element atom:title { atomTextConstruct } atomTitle = element atom:title { atomTextConstruct }
# atom:updated # atom:updated
# TODO: Test for a timezone that SHOULD be UTC
atomUpdated = element atom:updated { atomDateConstruct } atomUpdated = element atom:updated { atomDateConstruct }
# Low-level simple types # Low-level simple types
# TODO: can anything more specific be said about these types?
atomNCName = xsd:string { minLength = "1" pattern = "[^:]*" } atomNCName = xsd:string { minLength = "1" pattern = "[^:]*" }
atomMediaType = text
atomLanguageTag = text # Whatever a media type is, it contains at least one slash
atomMediaType = xsd:string { pattern = ".+/.+" }
# As defined in RFC 3066
atomLanguageTag = xsd:string {
pattern = "[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*"
}
# Unconstrained; it's not entirely clear how IRI fit into
# xsd:anyURI so let's not try to constrain it here
atomUri = text atomUri = text
atomEmailAddress = text
# Whatever an email address is, it contains at least one @
atomEmailAddress = xsd:string { pattern = ".+@.+" }
# Extensibility # Extensibility
anyForeignElement = simpleExtensionElement =
element * - (atom:* | local:*) element * - atom:* {
{ text
(attribute * { text }
| text
| anyForeignElement)*
} }
anyForeignAttribute = structuredExtensionElement =
attribute * - (atom:* | local:* | xml:*) { text } element * - atom:* {
(attribute * { text }+,
(text|anyElement)*)
| (attribute * { text }*,
(text?, anyElement+, (text|anyElement)*))
}
extensionElement =
simpleExtensionElement | structuredExtensionElement
anyElement = anyElement =
element * - atom:* element * - atom:* {
{
(attribute * { text } (attribute * { text }
| text | text
| anyElement)* | anyElement)*
} }
# XHTML
anyXHTML = element xhtml:* {
(attribute * { text }
| text
| anyXHTML)*
}
xhtmlDiv = element xhtml:div {
(attribute * { text }
| text
| anyXHTML)*
}
# EOF # EOF
Appendix C. Change Log Appendix C. Change Log
[[anchor85: This section should be removed before final [[anchor72: This section should be removed before final
publication.]] publication.]]
-07: Change atom:source-feed to atom:source.
Add ABNF reference
Many editorial tweaks
Rework extensibility
Adjust page breaks in txt version
-06: Move Identity Construct into atom:id (only place it's used) -06: Move Identity Construct into atom:id (only place it's used)
atom:id values must be unique within a feed. atom:id values must be unique within a feed.
restore atom:copyright definition mistakenly dropped during restore atom:copyright definition mistakenly dropped during
alphabetizing. alphabetizing.
Remove atom:head, add atom:source-feed, and "Extension Construct" Remove atom:head, add atom:source-feed, and "Extension Construct"
text in an effort to accurately reflect WG consensus on data model text in an effort to accurately reflect WG consensus on data model
and extensibility, acknowledging two opinions in favor of and extensibility, acknowledging two opinions in favor of
atom:head. atom:head.
Note @hreflang issue. Note @hreflang issue.
Add comment on atom:entry/atom:summary requirements. Add comment on atom:entry/atom:summary requirements.
 End of changes. 

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