draft-ietf-atompub-format-08.txt   draft-ietf-atompub-format-09.txt 
Network Working Group M. Nottingham, Ed. Network Working Group M. Nottingham, Ed.
Internet-Draft R. Sayre, Ed. Internet-Draft R. Sayre, Ed.
Expires: October 20, 2005 April 18, 2005 Expires: December 9, 2005 June 07, 2005
The Atom Syndication Format The Atom Syndication Format
draft-ietf-atompub-format-08 draft-ietf-atompub-format-09
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
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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 . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Examples . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Examples . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Notational Conventions . . . . . . . . . . . . . . . . . . 5 1.2 Namespace and Version . . . . . . . . . . . . . . . . . . 5
1.3 Notational Conventions . . . . . . . . . . . . . . . . . . 5
2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 6 2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 6
3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 8 3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 8
3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 8 3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 8
3.1.1 The "type" Attribute . . . . . . . . . . . . . . . . . 8 3.1.1 The "type" Attribute . . . . . . . . . . . . . . . . . 8
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 . . . . . . . . . . . . . . . . . . . . . 12 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 . . . . . . . . . . . . . . . 15 4.1.2 The "atom:entry" Element . . . . . . . . . . . . . . . 15
4.1.3 The "atom:content" Element . . . . . . . . . . . . . . 17 4.1.3 The "atom:content" Element . . . . . . . . . . . . . . 17
4.2 Metadata Elements . . . . . . . . . . . . . . . . . . . . 20 4.2 Metadata Elements . . . . . . . . . . . . . . . . . . . . 20
4.2.1 The "atom:author" Element . . . . . . . . . . . . . . 20 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 . . . . . . . . . . . . 21
4.2.4 The "atom:copyright" Element . . . . . . . . . . . . . 21 4.2.4 The "atom:generator" Element . . . . . . . . . . . . . 21
4.2.5 The "atom:generator" Element . . . . . . . . . . . . . 21 4.2.5 The "atom:icon" Element . . . . . . . . . . . . . . . 21
4.2.6 The "atom:icon" Element . . . . . . . . . . . . . . . 21 4.2.6 The "atom:id" Element . . . . . . . . . . . . . . . . 22
4.2.7 The "atom:id" Element . . . . . . . . . . . . . . . . 22 4.2.7 The "atom:link" Element . . . . . . . . . . . . . . . 24
4.2.8 The "atom:image" Element . . . . . . . . . . . . . . . 23 4.2.8 The "atom:logo" Element . . . . . . . . . . . . . . . 26
4.2.9 The "atom:link" Element . . . . . . . . . . . . . . . 24 4.2.9 The "atom:published" Element . . . . . . . . . . . . . 26
4.2.10 The "atom:published" Element . . . . . . . . . . . . 26 4.2.10 The "atom:rights" Element . . . . . . . . . . . . . 26
4.2.11 The "atom:source" Element . . . . . . . . . . . . . 26 4.2.11 The "atom:source" Element . . . . . . . . . . . . . 27
4.2.12 The "atom:subtitle" Element . . . . . . . . . . . . 27 4.2.12 The "atom:subtitle" Element . . . . . . . . . . . . 27
4.2.13 The "atom:summary" Element . . . . . . . . . . . . . 27 4.2.13 The "atom:summary" Element . . . . . . . . . . . . . 28
4.2.14 The "atom:title" Element . . . . . . . . . . . . . . 27 4.2.14 The "atom:title" Element . . . . . . . . . . . . . . 28
4.2.15 The "atom:updated" Element . . . . . . . . . . . . . 27 4.2.15 The "atom:updated" Element . . . . . . . . . . . . . 28
5. Securing Atom Documents . . . . . . . . . . . . . . . . . . 29 5. Securing Atom Documents . . . . . . . . . . . . . . . . . . 29
6. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 30 6. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 30
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 33 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 32
8. Security Considerations . . . . . . . . . . . . . . . . . . 35 8. Security Considerations . . . . . . . . . . . . . . . . . . 34
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 36 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
9.1 Normative References . . . . . . . . . . . . . . . . . . . 36 9.1 Normative References . . . . . . . . . . . . . . . . . . . 35
9.2 Informative References . . . . . . . . . . . . . . . . . . 37 9.2 Informative References . . . . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 38 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 37
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 39 A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 38
B. RELAX NG Compact Schema . . . . . . . . . . . . . . . . . . 40 B. RELAX NG Compact Schema . . . . . . . . . . . . . . . . . . 39
C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 48 C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 47
Intellectual Property and Copyright Statements . . . . . . . 51 Intellectual Property and Copyright Statements . . . . . . . 53
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. directly to user agents.
1.1 Examples 1.1 Examples
A minimal, single-entry Atom Feed Document: A brief, single-entry Atom Feed Document:
<?xml version="1.0" encoding="utf-8"?> <?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-08"> <feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-09">
<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>
<id>urn:uuid:60a76c80-d399-11d9-b93C-0003939e0af6</id>
<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>
<summary>Some text.</summary> <summary>Some text.</summary>
</entry> </entry>
</feed> </feed>
A more extensive, single-entry Atom Feed Document: A more extensive, single-entry Atom Feed Document:
<?xml version="1.0" encoding="utf-8"?> <?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-08"> <feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-09">
<title type="text">dive into mark</title> <title type="text">dive into mark</title>
<subtitle type="html"> <subtitle type="html">
A &lt;em&gt;lot&lt;/em&gt; of effort A &lt;em&gt;lot&lt;/em&gt; of effort
went into making this effortless went into making this effortless
</subtitle> </subtitle>
<updated>2005-04-02T12:29:29Z</updated> <updated>2005-04-02T12:29:29Z</updated>
<id>tag:example.org,2003:3</id> <id>tag:example.org,2003:3</id>
<link rel="alternate" type="text/html" <link rel="alternate" type="text/html"
hreflang="en" href="http://example.org/"/> hreflang="en" href="http://example.org/"/>
<copyright>Copyright (c) 2003, Mark Pilgrim</copyright> <rights>Copyright (c) 2003, Mark Pilgrim</rights>
<generator uri="http://www.example.com/" version="1.0"> <generator uri="http://www.example.com/" version="1.0">
Example Toolkit Example Toolkit
</generator> </generator>
<entry> <entry>
<title>Atom draft-07 snapshot</title> <title>Atom draft-07 snapshot</title>
<link rel="alternate" type="text/html" <link rel="alternate" type="text/html"
href="http://example.org/2005/04/02/atom"/> href="http://example.org/2005/04/02/atom"/>
<link rel="enclosure" type="audio/mpeg" length="1337" <link rel="enclosure" type="audio/mpeg" length="1337"
href="http://example.org/audio/ph34r_my_podcast.mp3"/> href="http://example.org/audio/ph34r_my_podcast.mp3"/>
<id>tag:example.org,2003:3.2397</id> <id>tag:example.org,2003:3.2397</id>
<updated>2005-04-02T12:29:29Z</updated> <updated>2005-04-02T12:29:29Z</updated>
<published>2003-12-13T08:29:29-04:00</published> <published>2003-12-13T08:29:29-04:00</published>
<author> <author>
<name>Mark Pilgrim</name> <name>Mark Pilgrim</name>
<uri>http://example.org/</uri> <uri>http://example.org/</uri>
<email>f8dy@example.com</email> <email>f8dy@example.com</email>
</author> </author>
<contributor> <contributor>
<name>Sam Ruby</name> <name>Sam Ruby</name>
<uri>http://intertwingly.net/blog/</uri>
</contributor> </contributor>
<contributor> <contributor>
<name>Joe Gregorio</name> <name>Joe Gregorio</name>
<uri>http://bitworking.org/</uri>
</contributor> </contributor>
<content type="xhtml" xml:lang="en" <content type="xhtml" xml:lang="en"
xml:base="http://diveintomark.org/"> xml:base="http://diveintomark.org/">
<div xmlns="http://www.w3.org/1999/xhtml"> <div xmlns="http://www.w3.org/1999/xhtml">
<p><i>[Update: The Atom draft-07 snapshot is out.]</i></p> <p><i>[Update: The Atom draft-07 snapshot is out.]</i></p>
</div> </div>
</content> </content>
</entry> </entry>
</feed> </feed>
1.2 Notational Conventions 1.2 Namespace and Version
This specification describes conformance in terms of two artifacts;
Atom Feed Documents and Atom Entry documents. Additionally, it
places some requirements on Atom Processors.
This specification uses XML Namespaces [W3C.REC-xml-names-19990114] The XML Namespaces URI [W3C.REC-xml-names-19990114] for the XML data
to uniquely identify XML element names. It uses the following format described in this specification is:
namespace prefix for the indicated namespace URI;
"atom": http://purl.org/atom/ns#draft-ietf-atompub-format-08 http://purl.org/atom/ns#draft-ietf-atompub-format-09
[[anchor4: This paragraph to be removed by the RFC Editor. The [[anchor4: This paragraph to be removed by the RFC Editor. The
namespace here is a temporary one and will be changed when the IESG namespace here is a temporary one and will be changed when the IESG
approves this document as a standard. At that time, the namespace approves this document as a standard. At that time, the namespace
will be drawn from W3C URI space. The choice of that namespace will will be drawn from W3C URI space. The choice of that namespace will
be coordinated between the IETF and W3C through their respective be coordinated between the IETF and W3C through their respective
liaisons.]] liaisons.]]
Note that the choice of any namespace prefix is arbitrary and not For convenience, this data format may be referred to as "Atom 1.0".
semantically significant. This specification uses "Atom" internally.
Atom is specified using terms from the XML Infoset 1.3 Notational Conventions
[W3C.REC-xml-infoset-20040204]. However, this specification uses a
shorthand for two common terms; the phrase "Information Item" is This specification describes conformance in terms of two artifacts;
omitted when naming Element Information Items and Attribute Atom Feed Documents and Atom Entry documents. Additionally, it
Information Items. places some requirements on Atom Processors.
This specification uses the namespace prefix "atom:" for the
Namespace URI identified in section 1.2. above. Note that the choice
of namespace prefix is arbitrary and not semantically significant.
Atom is specified using terms from the XML Infoset [W3C.REC-xml-
infoset-20040204]. However, this specification uses a shorthand for
two common terms; the phrase "Information Item" is omitted when
naming Element Information Items and Attribute Information Items.
Therefore, when this specification uses the term "element," it is 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
complete schema appears in Appendix B. complete schema appears in Appendix B.
skipping to change at page 6, line 18 skipping to change at page 6, line 18
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 = namespace atom =
"http://purl.org/atom/ns#draft-ietf-atompub-format-08" "http://purl.org/atom/ns#draft-ietf-atompub-format-09"
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. This specification does not Documents MUST be well-formed XML. This specification does not
define a DTD for Atom Documents, and hence does not require them to define a DTD for Atom Documents, and hence does not require them to
be valid (in the sense used by XML). be valid (in the sense used by XML).
Atom allows the use of IRIs [RFC3987], as well as URIs [RFC3986].
IRIs can easily be converted to URIs. Every URI is an IRI, so any
URI can be used where an IRI is needed. When comparing IRIs serving
as atom:id values, they MUST NOT be converted to URIs.
Any element defined by this specification MAY have an xml:base Any element defined by this specification MAY have an xml:base
attribute. XML Base [W3C.REC-xmlbase-20010627] processing MUST be attribute [W3C.REC-xmlbase-20010627]. When xml:base is used in an
applied to any relative reference [RFC3987] present in an Atom Atom document, it serves the function described in section 5.1.1 of
Document. This includes such elements and attributes as specified by [RFC3986], establishing the base URI (or IRI) for resolving any
Atom itself, as well as those specified by extensions to Atom. relative references found within the effective scope of the xml:base
attribute.
Any element defined by this specification MAY have an xml:lang Any element defined by this specification MAY have an xml:lang
attribute, whose content indicates the natural language for the attribute, whose content indicates the natural language for the
element and its children. The language context is only significant element and its descendents. The language context is only
for elements and attributes declared to be "language-sensitive" by significant for elements and attributes declared to be "Language-
this specification. Requirements regarding the content and Sensitive" by this specification. Requirements regarding the content
interpretation of xml:lang are specified in XML 1.0 and interpretation of xml:lang are specified in XML 1.0 [W3C.REC-xml-
[W3C.REC-xml-20040204], Section 2.12. 20040204], Section 2.12.
atomCommonAttributes = atomCommonAttributes =
attribute xml:base { atomUri }?, attribute xml:base { atomUri }?,
attribute xml:lang { atomLanguageTag }? attribute xml:lang { atomLanguageTag }?,
undefinedAttribute*
Atom allows the use of IRIs [RFC3987], as well as URIs [RFC3986].
IRIs can easily be converted to URIs. Every URI is an IRI, so any
URI can be used where an IRI is needed. When comparing IRIs serving
as atom:id values, they MUST NOT be converted to URIs.
Atom is an extensible format. See Section 6 of this document for a Atom is an extensible format. See Section 6 of this document for a
full description of how Atom Documents can be extended. full description of how Atom Documents can be extended.
Atom Processors MAY keep state (e.g., metadata in atom:feed, entries) Atom Processors MAY keep state sourced from Atom Feed Documents and
sourced from Atom Feed Documents and combine them with other Atom combine them with other Atom Feed Documents, in order to facilitate a
Feed Documents, in order to facilitate a contiguous view of the contiguous view of the contents of a feed. The manner in which Atom
contents of a feed. The manner in which Atom Feed Documents are Feed Documents are combined in order to reconstruct a feed (e.g.,
combined in order to reconstruct a feed (e.g., updating entries and updating entries and metadata, dealing with missing entries) is out
metadata, dealing with missing entries) is out of the scope of this of the scope of this specification.
specification.
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 those 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. The content of Text constructs is language-sensitive. quantities. The content of Text 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" },
xhtmlDiv xhtmlDiv
skipping to change at page 10, line 18 skipping to change at page 10, line 18
... ...
<title type="xhtml" xmlns:xhtml="http://www.w3.org/1999/xhtml"> <title type="xhtml" xmlns:xhtml="http://www.w3.org/1999/xhtml">
<xhtml:div> <xhtml:div>
Less: <xhtml:em> &lt; </xhtml:em> Less: <xhtml:em> &lt; </xhtml:em>
</xhtml:div> </xhtml:div>
</title> </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 [XHTML]. The XHTML div MUST MUST be a single XHTML div element [XHTML], and SHOULD be suitable
contain XHTML text and markup that could validly appear within an for handling as XHTML. The XHTML div element itself MUST NOT be
XHTML div element. The XHTML div element itself MUST NOT be considered part of the content. Atom Processors that display the
considered part of the content. Atom Processors which display the content MAY use the markup to aid in displaying it. The escaped
content MAY use the markup to aid in displaying it. Escaped versions of characters such as "&" and ">" represent those
characters, such as "&" and ">", represent those characters, not characters, not markup.
markup.
Examples of valid XHTML content: 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>
... ...
skipping to change at page 11, line 19 skipping to change at page 11, line 19
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*) & extensionElement*)
This specification assigns no significance to the order of appearance This specification assigns no significance to the order of appearance
of the child elements in a Person construct. Person constructs allow of the child elements in a Person construct. Person constructs allow
extension Metadata Elements (see Section 6.4). 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].
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:
atom:email element, but MUST NOT contain more than one. Its content email element, but MUST NOT contain more than one. Its content MUST
MUST conform to the "addr-spec" production in [RFC2822]. conform to the "addr-spec" production 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" production in [RFC3339]. In addition, an uppercase "T" "date-time" production in [RFC3339]. In addition, an uppercase "T"
character MUST be used to separate date and time, and an uppercase character MUST be used to separate date and time, and an uppercase
"Z" character MUST be present in the absence of a numeric time zone "Z" character MUST be present in the absence of a numeric time zone
offset. offset.
atomDateConstruct = atomDateConstruct =
atomCommonAttributes, atomCommonAttributes,
xsd:dateTime xsd:dateTime
Such date values happen to be compatible with the following Such date values happen to be compatible with the following
specifications: [ISO.8601.1988], [W3C.NOTE-datetime-19980827], and specifications: [ISO.8601.1988], [W3C.NOTE-datetime-19980827], and
[W3C.REC-xmlschema-2-20041028]. [W3C.REC-xmlschema-2-20041028].
Example Date constructs:
<updated>2003-12-13T18:30:02Z</updated>
<updated>2003-12-13T18:30:02.25Z</updated>
<updated>2003-12-13T18:30:02+01:00</updated>
<updated>2003-12-13T18:30:02.25+01:00</updated>
Date values SHOULD be as accurate as possible. For example, it would Date values SHOULD be as accurate as possible. For example, it would
be generally inappropriate for a publishing system to apply the same be generally inappropriate for a publishing system to apply the same
timestamp to several entries which were published during the course timestamp to several entries which were published during the course
of a single day. 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
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 metadata associated with the feed. Its element children consist of metadata
elements followed by zero or more atom:entry child elements. elements followed by zero or more atom:entry child elements.
atomFeed = atomFeed =
element atom:feed { element atom:feed {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor*
& atomCategory* & atomCategory*
& atomContributor* & atomContributor*
& atomCopyright?
& atomGenerator? & atomGenerator?
& atomIcon? & atomIcon?
& atomId? & atomId
& atomImage? & atomLink*
& atomLink+ & atomLogo?
& atomRights?
& atomSubtitle? & atomSubtitle?
& atomTitle & atomTitle
& atomUpdated & atomUpdated
& extensionElement*), & extensionElement*),
atomEntry* atomEntry*
} }
This specification assigns no significance to the order of atom:entry This specification assigns no significance to the order of atom:entry
elements within the feed. 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 one or more atom:author elements,
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. contain at least one atom:author element.
o atom:feed elements MUST NOT contain more than one atom:author
element.
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
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.
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 exactly one atom:id element.
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". This URI identifies the feed and a attribute value of "self". This is the preferred URI for
representation equivalent to the feed. retrieving Atom Feed Documents representing this Atom 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. atom:feed elements MAY contain same type attribute value. 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:rights
element.
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.
o atom:feed elements MUST contain exactly one atom:title element. o atom:feed elements MUST contain exactly one atom:title element.
o atom:feed elements MUST contain exactly one atom:updated element. o atom:feed elements MUST contain exactly one atom:updated element.
o atom:feed elements MUST NOT contain atom:entry elements with
identical atom:id values. If multiple atom:entry elements with the same atom:id value appear in
an Atom Feed Document, they represent the same entry. Their atom:
updated timestamps SHOULD be different. If an Atom Feed Document
contains multiple entries with the same atom:id, Atom Processors MAY
choose to display all of them or some subset of them. One typical
behavior would be to display only the entry with the latest atom:
updated timestamp.
4.1.1.1 Providing Textual Content
Experience teaches that feeds which contain textual content are in
general more useful than those which do not. Some applications (one
example is full-text indexers) require a minimum amount of text or
(X)HTML to function reliably and predictably. Feed producers should
be aware of these issues. It is advisable that each atom:entry
element contain a non-empty atom:title element, a non-empty atom:
content element when that element is present, and a non-empty atom:
summary element when the entry contains no atom:content element.
However, the absence of atom:summary is not an error and Atom
Processors MUST NOT fail to function correctly as a consequence of
such an absence.
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.
atomEntry = atomEntry =
element atom:entry { element atom:entry {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor*
& atomCategory* & atomCategory*
& atomContent? & atomContent?
& atomContributor* & atomContributor*
& atomCopyright?
& atomId & atomId
& atomLink* & atomLink*
& atomPublished? & atomPublished?
& atomRights?
& atomSource? & atomSource?
& atomSummary? & atomSummary?
& atomTitle & atomTitle
& atomUpdated & atomUpdated
& extensionElement*) & extensionElement*)
} }
This specification assigns no significance to the order of appearance This specification assigns no significance to the order of appearance
of the child elements of atom:entry. 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 one or more atom:author elements,
unless the atom:entry contains an atom:source element which unless the atom:entry contains an atom:source element which
contains an atom:author element, or, in an Atom Feed Document, the contains an atom:author element, or, in an Atom Feed Document, the
atom:feed element contains an atom:author element itself. atom:feed element contains an atom:author element itself.
o atom:entry elements MUST NOT contain more than one atom:author
element.
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 o atom:entry elements MUST NOT contain more than one atom:content
element. 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
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". value of "alternate".
o atom:entry elements MUST NOT contain more than one atom:link o atom:entry 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 combination of type and hreflang attribute values. same combination of type and hreflang attribute values.
o atom:entry elements MAY contain additional atom:link elements o atom:entry elements MAY contain additional atom:link elements
beyond those described above. beyond those 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 atom:rights
element.
o atom:entry elements MUST NOT contain more than one atom:source o atom:entry elements MUST NOT contain more than one atom:source
element. element.
o atom:entry elements MUST contain an atom:summary element in any of
the following cases: o atom:entry elements MUST contain an atom:summary element in either
* the atom:entry element contains no atom:content element. of the following cases:
* 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
[MIMEREG] and does not begin with "text/" nor end with "+xml". [MIMEREG], but is not an XML media type [RFC3023], does not
begin with "text/", and does not end with "/xml" or "+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. The content of atom:content is language-sensitive. the entry. The content of atom:content is Language-Sensitive.
atomInlineTextContent = atomInlineTextContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "text" | "html" }?, attribute type { "text" | "html" }?,
(text)* (text)*
} }
atomInlineXHTMLContent = atomInlineXHTMLContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "xhtml" }, attribute type { "xhtml" },
xhtmlDiv xhtmlDiv
} }
atomInlineOtherContent = atomInlineOtherContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { atomMediaType }?, attribute type { atomMediaType }?,
(text|anyForeignElement)* (text|anyElement)*
} }
atomOutOfLineContent = atomOutOfLineContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { atomMediaType }?, attribute type { atomMediaType }?,
attribute src { atomUri }, attribute src { atomUri },
empty empty
} }
skipping to change at page 18, line 8 skipping to change at page 18, line 8
On the atom:content element, the value of the "type" attribute MAY be On the atom:content element, the value of the "type" attribute MAY be
one of "text", "html", or "xhtml". Failing that, it MUST be a MIME one of "text", "html", or "xhtml". Failing that, it MUST be a MIME
media type, but MUST NOT be a composite type (see Section 4.2.6 of media type, but MUST NOT be a composite type (see Section 4.2.6 of
[MIMEREG]). If the type attribute is not provided, Atom Processors [MIMEREG]). If the type attribute is not provided, Atom Processors
MUST behave as though it were present with a value of "text". MUST behave as though it were present with a value of "text".
4.1.3.2 The "src" attribute 4.1.3.2 The "src" attribute
atom:content MAY have a "src" attribute, whose value MUST be an IRI atom:content MAY have a "src" attribute, whose value MUST be an IRI
reference [RFC3987]. If the "src" attribute is present, Atom reference [RFC3987]. If the "src" attribute is present, atom:content
Processors MAY use the IRI to retrieve the content. If the "src" MUST be empty. Atom Processors MAY use the IRI to retrieve the
attribute is present, atom:content MUST be empty. content, and MAY NOT process or present remote content in the same
manner as local content.
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 [MIMEREG], rather than "text", provided and MUST be a MIME media type [MIMEREG], 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-
server-provided media type is authoritative. provided media type is authoritative.
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
provided.
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 collapse white-space (including line-breaks), and display the MAY collapse white-space (including line-breaks), and display the
text using typographic techniques such as justification and text using typographic techniques such as justification and
proportional fonts. proportional fonts.
2. If the value of "type" is "html", the content of atom:content 2. If the value of "type" is "html", the content of atom:content
MUST NOT contain child elements, and SHOULD be suitable for MUST NOT contain child elements, and SHOULD be suitable for
handling as HTML [HTML]. The HTML markup must be escaped; for handling as HTML [HTML]. The HTML markup MUST be escaped; for
example, "<br>" as "&lt;br>". The HTML markup SHOULD be such example, "<br>" as "&lt;br>". The HTML markup SHOULD be such
that it could validly appear directly within an HTML <DIV> that it could validly appear directly within an HTML <DIV>
element. Atom Processors that display the content MAY use the element. Atom Processors that display the content MAY use the
markup to aid in displaying it. markup to aid in displaying it.
3. If the value of "type" is "xhtml", the content of atom:content 3. If the value of "type" is "xhtml", the content of atom:content
MUST be a single XHTML div element [XHTML], and SHOULD be MUST be a single XHTML div element [XHTML], and SHOULD be
suitable for handling as XHTML. The XHTML div element itself suitable for handling as XHTML. The XHTML div element itself
MUST NOT be considered part of the content. Atom Processors that MUST NOT be considered part of the content. Atom Processors that
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 characters, such as "&" and ">", represent those The escaped versions of characters such as "&" and ">" represent
characters, not markup. those characters, not markup.
4. If the value of "type" ends with "+xml" or "/xml" 4. If the value of "type" is an XML media type [RFC3023], or ends
(case-insensitive), the content of atom:content MAY include child with "+xml" or "/xml" (case-insensitive), the content of
elements, and SHOULD be suitable for handling as the indicated atom:content MAY include child elements, and SHOULD be suitable
media type. If the "src" attribute is not provided, this would for handling as the indicated media type. If the "src" attribute
normally mean that the "atom:content" element would contain a is not provided, this would normally mean that the "atom:content"
single child element which would serve as the root element of the element would contain a single child element which would serve as
XML document of the indicated type. the root element of the XML document of the indicated type.
5. If the value of "type" begins with "text/" (case-insensitive), 5. If the value of "type" begins with "text/" (case-insensitive),
the content of atom:content MUST NOT contain child elements. the content of atom:content MUST NOT contain child elements.
6. For all other values of "type", the content of atom:content MUST 6. For all other values of "type", the content of atom:content MUST
be a valid Base64 encoding [RFC3548], which when decoded SHOULD be a valid Base64 encoding, as described in [RFC3548], section 3.
be suitable for handling as the indicated media type. In this When decoded, it SHOULD be suitable for handling as the indicated
case, the characters in the Base64 encoding MAY be preceded and media type. In this case, the characters in the Base64 encoding
followed in the atom:content element by white-space, and lines MAY be preceded and followed in the atom:content element by
are separated by a single newline (U+000A) character. white-space, and lines are separated by a single newline (U+000A)
character.
4.1.3.4 Examples 4.1.3.4 Examples
XHTML inline: XHTML inline:
... ...
<content type="xhtml"> <content 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>
skipping to change at page 20, line 14 skipping to change at page 20, line 14
4.2 Metadata Elements 4.2 Metadata Elements
4.2.1 The "atom:author" Element 4.2.1 The "atom:author" Element
The "atom:author" element is a Person construct that indicates the The "atom:author" element is a Person construct that indicates the
author of the entry or feed. author of the entry or feed.
atomAuthor = element atom:author { atomPersonConstruct } atomAuthor = element atom:author { atomPersonConstruct }
If an atom:entry element does not contain atom:author elements, then
the atom:author elements of the contained atom:source element are
considered to apply. In an Atom Feed Document, the atom:author
elements of the containing atom:feed element are considered to apply
to the entry if there are no atom:author elements in the locations
described above.
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. This specification assigns no
meaning to the content (if any) of this element.
atomCategory = atomCategory =
element atom:category { element atom:category {
atomCommonAttributes, atomCommonAttributes,
attribute term { text }, attribute term { text },
attribute scheme { atomUri }?, attribute scheme { atomUri }?,
attribute label { text }?, attribute label { text }?,
empty undefinedContent
} }
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.
4.2.2.2 The "scheme" Attribute 4.2.2.2 The "scheme" Attribute
The "scheme" attribute is an IRI that identifies a categorization The "scheme" attribute is an IRI that identifies a categorization
scheme. Category elements MAY have a "scheme" attribute. scheme. Category elements MAY have a "scheme" attribute.
4.2.2.3 The "label" attribute 4.2.2.3 The "label" attribute
The "label" attribute provides a human-readable label for display in The "label" attribute provides a human-readable label for display in
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:generator" Element
The "atom:copyright" element is a Text construct that conveys a
human-readable copyright statement for an entry or feed.
atomCopyright = element atom:copyright { atomTextConstruct }
The atom:copyright element SHOULD NOT be used to convey
machine-readable licensing information.
If an atom:entry element does not contain an atom:copyright element,
then the atom:copyright element of the containing atom:feed element's
atom:head element, if present, is considered to apply to the entry.
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 = element atom:generator { atomGenerator = 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.
value is unstructured text.
4.2.6 The "atom:icon" Element 4.2.5 The "atom:icon" Element
The "atom:icon" element's content is an IRI reference [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. feed.
atomIcon = element atom:icon { atomIcon = element atom:icon {
atomCommonAttributes, atomCommonAttributes,
(atomUri) (atomUri)
} }
The image SHOULD have an aspect ratio of one (horizontal) to one The image SHOULD have an aspect ratio of one (horizontal) to one
(vertical), and should be suitable for presentation at a small size. (vertical), and SHOULD be suitable for presentation at a small size.
4.2.7 The "atom:id" Element 4.2.6 The "atom:id" Element
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 { atomId = element atom:id {
atomCommonAttributes, atomCommonAttributes,
(atomUri) (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
skipping to change at page 22, line 37 skipping to change at page 22, line 35
atom:id element be stored along with the associated resource. 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. assures uniqueness.
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 equivalent if dereferenced, the following normalization strategy
SHOULD be applied when generating atom:id elements: SHOULD be applied 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.
o For schemes that define a default authority, use an empty o For schemes that define a default authority, use an empty
authority if the default is desired. authority if the default is desired.
o For schemes that define an empty path to be equivalent to a path o For schemes that define an empty path to be equivalent to a path
of "/", use "/". of "/", use "/".
o For schemes that define a port, use an empty port if the default o For schemes that define a port, use an empty port if the default
is desired. is desired.
o Preserve empty fragment identifiers and queries. o Preserve empty fragment identifiers and queries.
o Ensure that all components of the IRI are appropriately
character-normalized, e.g. by using NFC or NFKC.
4.2.7.1 Comparing atom:id o Ensure that all components of the IRI are appropriately character-
normalized, e.g. by using NFC or NFKC.
4.2.6.1 Comparing atom:id
Instances of atom:id elements can be compared to determine whether an Instances of atom:id elements can be compared to determine whether an
entry or feed is the same as one seen before. Processors MUST entry or feed is the same as one seen before. Processors MUST
compare atom:id elements on a character-by-character basis (in a compare atom:id elements on a character-by-character basis (in a
case-sensitive fashion). Comparison operations MUST be based solely case-sensitive fashion). Comparison operations MUST be based solely
on the IRI character strings, and MUST NOT rely on dereferencing the on the IRI character strings, and MUST NOT rely on dereferencing the
IRIs. IRIs.
As a result, two IRIs that resolve to the same resource but are not As a result, two IRIs that resolve to the same resource but are not
character-for-character identical will be considered different for character-for-character identical will be considered different for
the purposes of identifier comparison. the purposes of identifier comparison.
For example: For example, these are four distinct identifiers, despite the fact
that they differ only in case:
http://www.example.org/thing http://www.example.org/thing
http://www.example.org/Thing http://www.example.org/Thing
http://www.EXAMPLE.org/thing http://www.EXAMPLE.org/thing
HTTP://www.example.org/thing
are four distinct identifiers, despite their differences in case. HTTP://www.example.org/thing
Likewise, Likewise, these are three distinct identifiers, because IRI
%-escaping is significant for the purposes of comparison:
http://www.example.com/~bob http://www.example.com/~bob
http://www.example.com/%7ebob
http://www.example.com/%7Ebob
are three distinct identifiers, because IRI %-escaping is significant http://www.example.com/%7ebob
for the purposes of comparison.
4.2.8 The "atom:image" Element
The "atom:image" element's content is an IRI reference [RFC3987]
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 http://www.example.com/%7Ebob
(vertical).
4.2.9 The "atom:link" Element 4.2.7 The "atom:link" Element
The "atom:link" element is an empty element that defines a reference The "atom:link" element defines a reference from an entry or feed to
from an entry or feed to a Web resource. a Web resource. This specification assigns no meaning to the content
(if any) of this element.
atomLink = atomLink =
element atom:link { 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 undefinedContent
} }
4.2.9.1 The "href" Attribute 4.2.7.1 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
MUST have a href attribute, whose value MUST be a IRI reference have a href attribute, whose value MUST be a IRI reference [RFC3987].
[RFC3987].
4.2.9.2 The "rel" Attribute 4.2.7.2 The "rel" Attribute
atom:link elements MAY have a "rel" attribute that indicates the link atom:link elements MAY have a "rel" attribute that indicates the 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".
The value of "rel" MUST be string that is non-empty, and matches the The value of "rel" MUST be a string that is non-empty, and matches
"isegment-nz-nc" or "IRI" production in [RFC3987]. Note that use of the "isegment-nz-nc" or "IRI" production in [RFC3987]. Note that use
a relative reference is not allowed. If a name is given, of a relative reference is not allowed. If a name is given,
implementations MUST consider the link relation type to be equivalent implementations MUST consider the link relation type to be equivalent
to the same name registered within the IANA Registry of Link to the same name registered within the IANA Registry of Link
Relations Section 7, and thus the IRI that would be obtained by Relations Section 7, and thus the IRI that would be obtained by
appending the value of the rel attribute to the string appending the value of the rel attribute to the string
"http://www.iana.org/assignments/relation/". The value of "rel" "http://www.iana.org/assignments/relation/". The value of "rel"
describes the meaning of the link, but does not impose any behavioral describes the meaning of the link, but does not impose any behavioral
requirements on implementations. requirements on Atom Processors.
This document defines five initial values for the Registry of Link This document defines five initial values for the Registry of Link
Relations: Relations:
1. The value "alternate" signifies that the IRI in the value of the 1. The value "alternate" signifies that the IRI in the value of the
href attribute identifies an alternate version of the resource href attribute identifies an alternate version of the resource
described by the containing element. described by the containing element.
2. The value "related" signifies that the IRI in the value of the 2. The value "related" signifies that the IRI in the value of the
href attribute identifies a resource related to the resource href attribute identifies a resource related to the resource
skipping to change at page 25, line 23 skipping to change at page 25, line 23
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.
3. 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 attribute identifies a resource equivalent to the containing
element. element.
4. The value "enclosure" signifies that the IRI in the value of the 4. The value "enclosure" signifies that the IRI in the value of the
href attribute identifies a related resource which is potentially href attribute identifies a related resource which is potentially
large in size and might require special handling by consuming large in size and might require special handling. For atom:link
software. For Link elements with rel="enclosure", the length elements with rel="enclosure", the length attribute SHOULD be
attribute SHOULD be provided. provided.
5. 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 attribute identifies a resource that is the source of the
information provided in the containing element. information provided in the containing element.
4.2.9.3 The "type" Attribute 4.2.7.3 The "type" Attribute
On the link element, the "type" attribute's value is an advisory On the link element, the "type" attribute's value is an advisory
media type; it is a hint about the type of the representation that is media type; it is a hint about the type of the representation that is
expected to be returned when the value of the href attribute is expected to be returned when the value of the href attribute is
dereferenced. Note that the type attribute does not override the dereferenced. Note that the type attribute does not override the
actual media type returned with the representation. Link elements actual media type returned with the representation. Link elements
MAY have a type attribute, whose value MUST conform to the syntax of MAY have a type attribute, whose value MUST conform to the syntax of
a MIME media type [MIMEREG]. a MIME media type [MIMEREG].
4.2.9.4 The "hreflang" Attribute 4.2.7.4 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 4.2.7.5 The "title" Attribute
The "title" attribute conveys human-readable information about the The "title" attribute conveys human-readable information about the
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 4.2.7.6 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. Link elements MAY have a length attribute. underlying protocol. Link elements MAY have a length attribute.
4.2.10 The "atom:published" Element 4.2.8 The "atom:logo" Element
The "atom:logo" element's content is an IRI reference [RFC3987] which
identifies an image which provides visual identification for a feed.
atomLogo = element atom:logo {
atomCommonAttributes,
(atomUri)
}
The image SHOULD have an aspect ratio of 2 (horizontal) to 1
(vertical).
4.2.9 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. the entry.
atomPublished = element atom:published { atomDateConstruct } atomPublished = element atom:published { atomDateConstruct }
Typically, atom:published will be associated with the initial Typically, atom:published will be associated with the initial
creation or first availability of the resource. creation or first availability of the resource.
4.2.10 The "atom:rights" Element
The "atom:rights" element is a Text construct that conveys
information about rights held in and over an entry or feed.
atomRights = element atom:rights { atomTextConstruct }
The atom:rights element SHOULD NOT be used to convey machine-readable
licensing information.
If an atom:entry element does not contain an atom:rights element,
then the atom:rights element of the containing atom:feed element, if
present, is considered to apply to the entry.
4.2.11 The "atom:source" Element 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 child element, if it is not already entry by adding an atom:source child element, if it is not already
present in the entry, and including some or all of the source feed's present in the entry, and including some or all of the source feed's
metadata elements as the atom:source element's children. Such Metadata elements as the atom:source element's children. Such
metadata SHOULD be preserved if the source atom:feed contains any of metadata SHOULD be preserved if the source atom:feed contains any of
the child elements atom:author, atom:contributor, atom:copyright, or the child elements atom:author, atom:contributor, atom:rights, or
atom:category and those child elements are not present in the source atom:category and those child elements are not present in the source
atom:entry. atom:entry.
atomSource = atomSource =
element atom:source { element atom:source {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor?
& atomCategory* & atomCategory*
& atomContributor* & atomContributor*
& atomCopyright?
& atomGenerator? & atomGenerator?
& atomIcon? & atomIcon?
& atomId? & atomId?
& atomImage? & atomLink*
& atomLink+ & atomLogo?
& atomRights?
& atomSubtitle? & atomSubtitle?
& atomTitle & atomTitle?
& atomUpdated & atomUpdated?
& extensionElement*) & extensionElement*)
} }
The atom:source element is designed to allow the aggregation of
entries from different feeds while retaining information about an
entry's source feed. For this reason, Atom Processors which are
performing such aggregation SHOULD include at least the required
feed-level Metadata elements (atom:id, atom:title, and atom:updated)
in the atom:source element.
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-
human-readable description or subtitle for a feed. 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
The "atom:summary" element is a Text construct that conveys a short The "atom:summary" element is a Text construct that conveys a short
summary, abstract or excerpt of an entry. summary, abstract, or excerpt of an entry.
atomSummary = element atom:summary { atomTextConstruct } atomSummary = element atom:summary { atomTextConstruct }
It is not advisable for the atom:summary element to duplicate atom:
title or atom:content, because Atom Processors might assume there is
a useful summary when there is none.
4.2.14 The "atom:title" Element 4.2.14 The "atom:title" Element
The "atom:title" element is a Text construct that conveys a The "atom:title" element is a Text construct that conveys a human-
human-readable title for an entry or feed. readable title for an entry or feed.
atomTitle = element atom:title { atomTextConstruct } atomTitle = element atom:title { atomTextConstruct }
4.2.15 The "atom:updated" Element 4.2.15 The "atom:updated" Element
The "atom:updated" element is a Date construct indicating the most The "atom:updated" element is a Date construct indicating the most
recent instant in time when an entry or feed was modified in a way recent instant in time when an entry or feed was modified in a way
the publisher considers significant. Therefore, not all the publisher considers significant. Therefore, not all
modifications necessarily result in a changed atom:updated value. modifications necessarily result in a changed atom:updated value.
skipping to change at page 29, line 17 skipping to change at page 29, line 17
Because Atom is an XML-based format, existing XML security mechanisms Because Atom is an XML-based format, existing XML security mechanisms
can be used to secure its content. can be used to secure its content.
5.1 Digital Signatures 5.1 Digital Signatures
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 Atom 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 URI 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
skipping to change at page 30, line 24 skipping to change at page 30, line 24
6.2 Extensions To the Atom Vocabulary 6.2 Extensions To the Atom Vocabulary
Future versions of this specification could add new elements and Future versions of this specification could 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".
6.3 Software Processing of Foreign Markup 6.3 Processing Foreign Markup
Software processing an Atom Document which encounters foreign markup Atom Processors which encounter foreign markup in a location that is
in a location that is legal according to this specification MUST NOT legal according to this specification MUST NOT stop processing or
stop processing or signal an error. It might be the case that the signal an error. It might be the case that the Atom Processor is
software is able to process the foreign markup correctly and does so. able to process the foreign markup correctly and does so. Otherwise,
Otherwise, such markup is termed "unknown foreign markup". 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 bypass the markup and atom:feed, or a Person construct, Atom Processors MAY bypass the
any textual content and MUST NOT change its behavior as a result of markup and any textual content and MUST NOT change their behavior as
the markup's presence. 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, except where
elements of atom:entry, atom:feed, and Person constructs are it is explicitly forbidden. Child elements of atom:entry, atom:feed,
considered Metadata Elements, and are described below. Child and Person constructs are considered Metadata elements, and are
elements of Person constructs are considered to apply to the described below. Child elements of Person constructs are considered
construct. The role of other foreign markup is undefined by this to apply to the construct. The role of other foreign markup is
specification. 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 character data, or be empty. elements. The element MAY contain character data, or be empty.
Simple Extension elements are not language-sensitive. Simple Extension elements are not Language-Sensitive.
simpleExtensionElement = simpleExtensionElement =
element * - atom:* { element * - atom:* {
text text
} }
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. Structured Extension elements are language-sensitive. be empty. Structured Extension elements are Language-Sensitive.
structuredExtensionElement = structuredExtensionElement =
element * - atom:* { element * - atom:* {
(attribute * { text }+, (attribute * { text }+,
(text|anyElement)*) (text|anyElement)*)
| (attribute * { text }*, | (attribute * { text }*,
(text?, anyElement+, (text|anyElement)*)) (text?, anyElement+, (text|anyElement)*))
} }
The structure of a Structured Extension element, including the order The structure of a Structured Extension element, including the order
skipping to change at page 33, line 11 skipping to change at page 32, line 11
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
An Atom Document, when serialized as XML 1.0, can be identified with An Atom Document, when serialized as XML 1.0, can be identified with
the following media type: the following media type:
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.
[[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. [[anchor60: update upon
publication]] Published specification: This specification.
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: IESG Author/Change controller: IESG
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 use the request to the IESG requesting approval. The request should use the
following template: following template:
skipping to change at page 34, line 6 skipping to change at page 33, line 24
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 use the request to the IESG requesting approval. The request should use the
following template: following template:
o Attribute Value: ( A value for the "rel" attribute that conforms o Attribute Value: ( A value for the "rel" attribute that conforms
to the syntax rule given in Section 4.2.9.2 ) to the syntax rule given in Section 4.2.7.2 )
o Description: o Description:
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
to receiving software. Many elements in these languages are XHTML. Many elements in these languages are considered 'unsafe' in
considered 'unsafe' in that they open clients to one or more types of that they open clients to one or more types of attack. Implementers
attack. Implementers of software which processes Atom should of software which processes Atom should carefully consider their
carefully consider their handling of every type of element when handling of every type of element when processing incoming (X)HTML in
processing incoming (X)HTML in Atom documents. See the security Atom documents. See the security sections of [RFC2854] and [HTML]
sections of [RFC2854] and [HTML] for guidance. 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 might also have negative security LINK elements, but other elements might 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 Spoofing
Atom documents can be encrypted and signed using Atom Processors should be aware of the potential for spoofing attacks
[W3C.REC-xmlenc-core-20021210] and [W3C.REC-xmldsig-core-20020212], where the attacker publishes an atom:entry with the atom:id value of
respectively, and are subject to the security considerations implied an entry from another feed, perhaps with a falsified atom:source
by their use. element duplicating the atom:id of the other feed. For example, an
Atom Processor could suppress display of duplicate entries by
displaying only one entry from a set of entries with identical
atom:id values. In that situation, the Atom Processor might also
take steps to determine whether the entries originated from the same
publisher before considering them to be duplicates.
8.5 Encryption and Signing
Atom documents can be encrypted and signed using [W3C.REC-xmlenc-
core-20021210] and [W3C.REC-xmldsig-core-20020212], respectively, and
are subject to the security considerations implied by their use.
9. References 9. References
9.1 Normative References 9.1 Normative References
[HTML] Raggett, D., Hors, A. and I. Jacobs, "HTML 4.01 [HTML] Raggett, D., Hors, A., and I. Jacobs, "HTML 4.01
Specification", W3C REC REC-html401-19991224, December Specification", W3C REC REC-html401-19991224,
1999, <http://www.w3.org/TR/1999/REC-html401-19991224>. December 1999,
<http://www.w3.org/TR/1999/REC-html401-19991224>.
[MIMEREG] Freed, N. and J. Klensin, "Media Type Specifications and [MIMEREG] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", work-in-progress Registration Procedures", work-in-progress
(draft-freed-media-type-reg-04), April 2005. (draft-freed-media-type-reg-04), April 2005.
[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.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
2001. April 2001.
[RFC2854] Connolly, D. and L. Masinter, "The 'text/html' Media [RFC2854] Connolly, D. and L. Masinter, "The 'text/html' Media
Type", RFC 2854, June 2000. 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.REC-xml-20040204] [W3C.REC-xml-20040204]
Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T. and Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T.,
E. Maler, "Extensible Markup Language (XML) 1.0 (Third and E. Maler, "Extensible Markup Language (XML) 1.0 (Third
Edition)", W3C REC REC-xml-20040204, February 2004, Edition)", W3C REC REC-xml-20040204, February 2004,
<http://www.w3.org/TR/2004/REC-xml-2004020>. <http://www.w3.org/TR/2004/REC-xml-2004020>.
[W3C.REC-xml-infoset-20040204] [W3C.REC-xml-infoset-20040204]
Cowan, J. and R. Tobin, "XML Information Set (Second Cowan, J. and R. Tobin, "XML Information Set (Second
Edition)", W3C REC REC-xml-infoset-20040204, February Edition)", W3C REC REC-xml-infoset-20040204,
2004, February 2004,
<http://www.w3.org/TR/2004/REC-xml-infoset-20040204>. <http://www.w3.org/TR/2004/REC-xml-infoset-20040204>.
[W3C.REC-xml-names-19990114] [W3C.REC-xml-names-19990114]
Hollander, D., Bray, T. and A. Layman, "Namespaces in Hollander, D., Bray, T., and A. Layman, "Namespaces in
XML", W3C REC REC-xml-names-19990114, January 1999, XML", W3C REC REC-xml-names-19990114, January 1999,
<http://www.w3.org/TR/1999/REC-xml-names-19990114>. <http://www.w3.org/TR/1999/REC-xml-names-19990114>.
[W3C.REC-xmlbase-20010627] [W3C.REC-xmlbase-20010627]
Marsh, J., "XML Base", W3C REC REC-xmlbase-20010627, June Marsh, J., "XML Base", W3C REC REC-xmlbase-20010627,
2001, <http://www.w3.org/TR/2001/REC-xmlbase-20010627>. June 2001,
<http://www.w3.org/TR/2001/REC-xmlbase-20010627>.
[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,
<http://www.w3.org/TR/2002/REC-xmldsig-core-20020212>. <http://www.w3.org/TR/2002/REC-xmldsig-core-20020212>.
[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,
2002, December 2002,
<http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>. <http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.
[XHTML] Altheim, M., Boumphrey, F., McCarron, S., Dooley, S., [XHTML] Altheim, M., Boumphrey, F., McCarron, S., Dooley, S.,
Schnitzenbaumer, S. and T. Wugofski, "Modularization of Schnitzenbaumer, S., and T. Wugofski, "Modularization of
XHTML[TM]", W3C REC REC-xhtml-modularization-20010410, XHTML[TM]", W3C REC REC-xhtml-modularization-20010410,
April 2001, April 2001, <http://www.w3.org/TR/2001/
<http://www.w3.org/TR/2001/REC-xhtml-modularization-200104 REC-xhtml-modularization-20010410>.
10>.
9.2 Informative References 9.2 Informative References
[ISO.8601.1988] [ISO.8601.1988]
International Organization for Standardization, "Data International Organization for Standardization, "Data
elements and interchange formats - Information interchange elements and interchange formats - Information interchange
- Representation of dates and times", ISO Standard 8601, - Representation of dates and times", ISO Standard 8601,
June 1988. June 1988.
[RELAX-NG] [RELAX-NG]
Clark, J., "RELAX NG Compact Syntax", December 2001, Clark, J., "RELAX NG Compact Syntax", December 2001, <http
<http://www.oasis-open.org/committees/relax-ng/compact-200 ://www.oasis-open.org/committees/relax-ng/
21121.html>. compact-20021121.html>.
[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] [W3C.NOTE-datetime-19980827]
Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C
NOTE NOTE-datetime-19980827, August 1998, NOTE NOTE-datetime-19980827, August 1998,
<http://www.w3.org/TR/1998/NOTE-datetime-19980827>. <http://www.w3.org/TR/1998/NOTE-datetime-19980827>.
[W3C.REC-xmlschema-2-20041028] [W3C.REC-xmlschema-2-20041028]
Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
Second Edition", W3C REC REC-xmlschema-2-20041028, October Second Edition", W3C REC REC-xmlschema-2-20041028,
2004, October 2004,
<http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>. <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.
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)
skipping to change at page 40, line 11 skipping to change at page 39, line 11
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. RELAX NG Compact Schema Appendix B. RELAX NG Compact Schema
This appendix is informative. This appendix is informative.
# -*- rnc -*- # -*- rnc -*-
# RELAX NG Compact Syntax Grammar for the # RELAX NG Compact Syntax Grammar for the
# Atom Format Specification Version 08 # Atom Format Specification Version 09
namespace atom = namespace atom =
"http://purl.org/atom/ns#draft-ietf-atompub-format-08" "http://purl.org/atom/ns#draft-ietf-atompub-format-09"
namespace xhtml = "http://www.w3.org/1999/xhtml" namespace xhtml = "http://www.w3.org/1999/xhtml"
namespace s = "http://www.ascc.net/xml/schematron" namespace s = "http://www.ascc.net/xml/schematron"
namespace local = ""
start = atomFeed | atomEntry start = atomFeed | atomEntry
# Common attributes # Common attributes
atomCommonAttributes = atomCommonAttributes =
attribute xml:base { atomUri }?, attribute xml:base { atomUri }?,
attribute xml:lang { atomLanguageTag }? attribute xml:lang { atomLanguageTag }?,
undefinedAttribute*
# Text Constructs # Text Constructs
atomPlainTextConstruct = atomPlainTextConstruct =
atomCommonAttributes, atomCommonAttributes,
attribute type { "text" | "html" }?, attribute type { "text" | "html" }?,
text text
atomXHTMLTextConstruct = atomXHTMLTextConstruct =
atomCommonAttributes, atomCommonAttributes,
skipping to change at page 41, line 13 skipping to change at page 40, line 15
atomCommonAttributes, atomCommonAttributes,
xsd:dateTime xsd:dateTime
# 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'] "
~ "or atom:link[not(@rel)]"
"An atom:feed must have at least one link element "
~ "with a rel attribute of 'alternate'."
]
]
s:rule [
context = "atom:feed"
s:assert [
test = "atom:author or not(atom:entry[not(atom:author)])" test = "atom:author or not(atom:entry[not(atom:author)])"
"An atom:feed must have an atom:author unless all " "An atom:feed must have an atom:author unless all "
~ "of 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?
& atomGenerator? & atomGenerator?
& atomIcon? & atomIcon?
& atomId? & atomId
& atomImage? & atomLink*
& atomLink+ & atomLogo?
& atomRights?
& atomSubtitle? & atomSubtitle?
& atomTitle & atomTitle
& atomUpdated & atomUpdated
& extensionElement*), & extensionElement*),
atomEntry* atomEntry*
} }
# atom:entry # atom:entry
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:link[not(@rel)] " ~ "or atom:link[not(@rel)] "
~ "or atom:content" ~ "or atom:content"
"An atom:entry must have at least one link element " "An atom:entry must have at least one atom:link element "
~ "with a rel attribute of 'alternate' or content." ~ "with a rel attribute of 'alternate' "
~ "or an atom:content."
] ]
] ]
s:rule [ s:rule [
context = "atom:entry" context = "atom:entry"
s:assert [ s:assert [
test = "atom:author or " test = "atom:author or "
~ "../atom:author or atom:source/atom:author" ~ "../atom:author or atom:source/atom:author"
"An atom:entry must have an atom:author " "An atom:entry must have an atom:author "
~ "if its feed does not." ~ "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?
& atomId & atomId
& atomLink* & atomLink*
& atomPublished? & atomPublished?
& atomRights?
& atomSource? & atomSource?
& atomSummary? & atomSummary?
& atomTitle & atomTitle
& atomUpdated & atomUpdated
& extensionElement*) & extensionElement*)
} }
# atom:content # atom:content
atomInlineTextContent = atomInlineTextContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "text" | "html" }?, attribute type { "text" | "html" }?,
(text)* (text)*
} }
atomInlineXHTMLContent = atomInlineXHTMLContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
skipping to change at page 43, line 22 skipping to change at page 42, line 5
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "xhtml" }, attribute type { "xhtml" },
xhtmlDiv xhtmlDiv
} }
atomInlineOtherContent = atomInlineOtherContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { atomMediaType }?, attribute type { atomMediaType }?,
(text|anyForeignElement)* (text|anyElement)*
} }
atomOutOfLineContent = atomOutOfLineContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { atomMediaType }?, attribute type { atomMediaType }?,
attribute src { atomUri }, attribute src { atomUri },
empty empty
} }
skipping to change at page 43, line 50 skipping to change at page 42, line 33
atomAuthor = element atom:author { atomPersonConstruct } atomAuthor = element atom:author { atomPersonConstruct }
# atom:category # atom:category
atomCategory = atomCategory =
element atom:category { element atom:category {
atomCommonAttributes, atomCommonAttributes,
attribute term { text }, attribute term { text },
attribute scheme { atomUri }?, attribute scheme { atomUri }?,
attribute label { text }?, attribute label { text }?,
empty undefinedContent
} }
# atom:contributor # atom:contributor
atomContributor = element atom:contributor { atomPersonConstruct } atomContributor = element atom:contributor { atomPersonConstruct }
# atom:copyright
atomCopyright = element atom:copyright { atomTextConstruct }
# atom:generator # atom:generator
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
skipping to change at page 44, line 35 skipping to change at page 43, line 15
(atomUri) (atomUri)
} }
# atom:id # atom:id
atomId = element atom:id { atomId = element atom:id {
atomCommonAttributes, atomCommonAttributes,
(atomUri) (atomUri)
} }
# atom:image # atom:logo
atomImage = element atom:image { atomLogo = element atom:logo {
atomCommonAttributes, atomCommonAttributes,
(atomUri) (atomUri)
} }
# atom:link # atom:link
atomLink = atomLink =
element atom:link { 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 undefinedContent
} }
# atom:published # atom:published
atomPublished = element atom:published { atomDateConstruct } atomPublished = element atom:published { atomDateConstruct }
# atom:rights
atomRights = element atom:rights { atomTextConstruct }
# atom:source # atom:source
atomSource = atomSource =
element atom:source { element atom:source {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor? (atomAuthor?
& atomCategory* & atomCategory*
& atomContributor* & atomContributor*
& atomCopyright?
& atomGenerator? & atomGenerator?
& atomIcon? & atomIcon?
& atomId? & atomId?
& atomImage? & atomLink*
& atomLink+ & atomLogo?
& atomRights?
& atomSubtitle? & atomSubtitle?
& atomTitle & atomTitle?
& atomUpdated & atomUpdated?
& extensionElement*) & 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 }
skipping to change at page 46, line 41 skipping to change at page 45, line 24
(text|anyElement)*) (text|anyElement)*)
| (attribute * { text }*, | (attribute * { text }*,
(text?, anyElement+, (text|anyElement)*)) (text?, anyElement+, (text|anyElement)*))
} }
# Other Extensibility # Other Extensibility
extensionElement = extensionElement =
simpleExtensionElement | structuredExtensionElement simpleExtensionElement | structuredExtensionElement
undefinedAttribute =
attribute * - (xml:base | xml:lang | local:*) { text }
undefinedContent = (text|anyForeignElement)*
anyElement = anyElement =
element * { element * {
(attribute * { text } (attribute * { text }
| text | text
| anyElement)* | anyElement)*
} }
anyForeignElement = anyForeignElement =
element * - atom:* { element * - atom:* {
(attribute * { text } (attribute * { text }
skipping to change at page 48, line 7 skipping to change at page 47, line 7
xhtmlDiv = element xhtml:div { xhtmlDiv = element xhtml:div {
(attribute * { text } (attribute * { text }
| text | text
| anyXHTML)* | anyXHTML)*
} }
# EOF # EOF
Appendix C. Change Log Appendix C. Change Log
[[anchor71: This section should be removed before final [[anchor72: This section should be removed before final
publication.]] publication.]]
-09: Changed atom:copyright to atom:rights.
Clarify atom:source, also reflect changes to atom:feed
Change 'minimal' to brief (PaceBriefExample).
Add text about "Atom 1.0" (PaceAtom10).
Remove SHOULD about content@src.
feed/id now required.
rework xml:base text
rework xml:lang terms and requirements
rework escaped markup explanations
change atom:image to atom:logo
Add example Date Constructs
Clarify that atom:link and atom:category MUST be empty.
Make XHTML definitions consistent
atom:icon editorial fix-- capitalize SHOULD.
-08: Remove BNF -08: Remove BNF
complete rather than collected schema complete rather than collected schema
Remove a couple introductory sentences Remove a couple introductory sentences
update MIME references update MIME references
Many editorial adjustments Many editorial adjustments
-07: Change atom:source-feed to atom:source. -07: Change atom:source-feed to atom:source.
Add ABNF reference Add ABNF reference
Many editorial tweaks Many editorial tweaks
Rework extensibility Rework extensibility
Adjust page breaks in txt version 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:
atom:head. head.
Note @hreflang issue. Note @hreflang issue.
Add comment on atom:entry/atom:summary requirements. Add comment on atom:entry/atom:summary requirements.
Rework atom:id text. The dereferencing section didn't talk about Rework atom:id text. The dereferencing section didn't talk about
dereferencing. dereferencing.
Remove protocol reference. Remove protocol reference.
Alphabetize where appropriate (PaceOrderSpecAlphabetically). Alphabetize where appropriate (PaceOrderSpecAlphabetically).
Add mI language (PaceExtendingAtom). Add mI language (PaceExtendingAtom).
Add atom:icon and atom:image (PaceImageAndIcon). Add atom:icon and atom:image (PaceImageAndIcon).
Change atom:tagline to atom:subtitle Change atom:tagline to atom:subtitle
Add inline XHTML language (PaceXHTMLNamespaceDiv). Add inline XHTML language (PaceXHTMLNamespaceDiv).
Change "TEXT" etc, to lowercase Change "TEXT" etc, to lowercase
Change example id IRI to urn:uuid:... Change example id IRI to urn:uuid:...
Add rel="self" (PaceFeedLink). Add rel="self" (PaceFeedLink).
Add Feed State text (PaceNoFeedState). Add Feed State text (PaceNoFeedState).
Move to IRIs (PaceIRI). Move to IRIs (PaceIRI).
Add rel="via" (PaceLinkRelVia). Add rel="via" (PaceLinkRelVia).
Add rel="enclosure" (PaceEnclosuresAndPix). Add rel="enclosure" (PaceEnclosuresAndPix).
Remove info and host (PaceRemoveInfoAndHost) Remove info and host (PaceRemoveInfoAndHost)
Clarify order of entries (PaceEntryOrder). Clarify order of entries (PaceEntryOrder).
Remove version attribute (PaceRemoveVersionAttr). Remove version attribute (PaceRemoveVersionAttr).
Date format roundup (PaceDatesXSD). Date format roundup (PaceDatesXSD).
Remove Service construct and elements. Remove Service construct and elements.
fix atom:contributor cardinality typo fix atom:contributor cardinality typo
Removed motivation/design principles note; if we haven't come up Removed motivation/design principles note; if we haven't come up
with them by now... with them by now...
Put conformance text into notational conventions. Put conformance text into notational conventions.
Removed instances of 'software'; too specific. Removed instances of 'software'; too specific.
Added refs to HTML and XHTML. Added refs to HTML and XHTML.
Updated ref to Infoset. Updated ref to Infoset.
Various editorial tweaks. Various editorial tweaks.
Fix RFC 3023 refs in IANA section Fix RFC 3023 refs in IANA section
Adjust head/link requirement Adjust head/link requirement
fix @version typos fix @version typos
-05: Add RNC from N. Walsh. -05: Add RNC from N. Walsh.
Re-organize element definitions. Re-organize element definitions.
Lift the prohibition on other types of DSig and encryption. Lift the prohibition on other types of DSig and encryption.
Remove text on "indiscriminate use" of DSig and XMLEnc. Remove text on "indiscriminate use" of DSig and XMLEnc.
-04: Update URI terms for 2396bis. -04: Update URI terms for 2396bis.
Add Category construct (PaceCategoryRevised). Add Category construct (PaceCategoryRevised).
Insert paranoid XHTML interpretation guidelines. Insert paranoid XHTML interpretation guidelines.
Adjust atom:copyright, per chairs' instruction. Adjust atom:copyright, per chairs' instruction.
Add atom:host as child element of atom:entry, per chairs' Add atom:host as child element of atom:entry, per chairs'
direction (PacePersonConstruct). direction (PacePersonConstruct).
Add link/content co-constraint (PaceContentOrLink). Add link/content co-constraint (PaceContentOrLink).
Remove atom:origin as a side effect of adding atom:head to
atom:entry (PaceHeadInEntry). Remove atom:origin as a side effect of adding atom:head to atom:
entry (PaceHeadInEntry).
Add optional length attribute to atom:link (PaceLinkRelated). Add optional length attribute to atom:link (PaceLinkRelated).
Add Link registry to Link Construct, IANA Considerations Add Link registry to Link Construct, IANA Considerations
placeholder (PaceFieldingLinks). placeholder (PaceFieldingLinks).
Change definition of atom:updated (PaceUpdatedDefinition). Change definition of atom:updated (PaceUpdatedDefinition).
-03: Move definition of Link @rel to format spec, restrict -03: Move definition of Link @rel to format spec, restrict
acceptable values (PaceMoveLinkElement, PaceLinkAttrDefaults). acceptable values (PaceMoveLinkElement, PaceLinkAttrDefaults).
Add Service Construct, head/post, head/introspection, entry/edit Add Service Construct, head/post, head/introspection, entry/edit
(PaceServiceElement). (PaceServiceElement).
Add Text Construct, entry/content (PaceReformedContent3). Add Text Construct, entry/content (PaceReformedContent3).
Add entry/published (PaceDatePublished). Add entry/published (PaceDatePublished).
Adjust definition of Identity Construct per chairs' direction to Adjust definition of Identity Construct per chairs' direction to
"fix it." "fix it."
Add Sayre to editors. Add Sayre to editors.
-02: Removed entry/modified, entry/issued, entry/created; added -02: Removed entry/modified, entry/issued, entry/created; added
entry/updated (PaceDateUpdated). entry/updated (PaceDateUpdated).
Changed date construct from W3C date-time to RFC3339 Changed date construct from W3C date-time to RFC3339
(PaceDateUpdated). (PaceDateUpdated).
Feed links to HTML pages should be reflected back Feed links to HTML pages should be reflected back
(PaceLinkReflection). (PaceLinkReflection).
Added Identity construct (PaceIdConstruct). Added Identity construct (PaceIdConstruct).
Changed feed/id and entry/id to be Identity constructs Changed feed/id and entry/id to be Identity constructs
(PaceIdConstruct). (PaceIdConstruct).
Changed entry/origin's content so that it's the same as the feed's Changed entry/origin's content so that it's the same as the feed's
id, rather than its link/@rel="alternate" (PaceIdConstruct). id, rather than its link/@rel="alternate" (PaceIdConstruct).
Added "Securing Atom Documents" (PaceDigitalSignatures). Added "Securing Atom Documents" (PaceDigitalSignatures).
-01: Constrained omission of "Information Item" to just elements and -01: Constrained omission of "Information Item" to just elements and
attributes. attributes.
Clarified xml:lang inheritence. Clarified xml:lang inheritence.
Removed entry- and feed-specific langauge about xml:lang (covered Removed entry- and feed-specific langauge about xml:lang (covered
by general discussion of xml:lang) by general discussion of xml:lang)
Changed xml:lang to reference XML for normative requirements. Changed xml:lang to reference XML for normative requirements.
Changed "... MUST be a string" to "... is unstructued text." Changed "... MUST be a string" to "... is unstructued text."
Remomved langauge about DOCTYPEs, PIs, Comments, Entities. Remomved langauge about DOCTYPEs, PIs, Comments, Entities.
Changed atom:url to atom:uri, @url to @uri Changed atom:url to atom:uri, @url to @uri
Introduced atom:head Introduced atom:head
Introduced "Atom Feed Document" and "Atom Entry Document". Introduced "Atom Feed Document" and "Atom Entry Document".
Removed requirement for all elements and attributes to be Removed requirement for all elements and attributes to be
namespace-qualified; now children of selective elements namespace-qualified; now children of selective elements
Added extensibility to Person constructs. Added extensibility to Person constructs.
Removed requirement for media types to be registered
(non-registered media types are legal) Removed requirement for media types to be registered (non-
registered media types are legal)
Added atom:origin (PaceEntryOrigin) Added atom:origin (PaceEntryOrigin)
Added requirement for entry/id to be present and a URI Added requirement for entry/id to be present and a URI
(PaceEntryIdRequired). (PaceEntryIdRequired).
Clarified approach to Comments, PIs and well-formedness, as per Clarified approach to Comments, PIs and well-formedness, as per
RFC3470. RFC3470.
Referenced escaping algorithm in XML. Referenced escaping algorithm in XML.
Assorted editorial nits and cleanup, refactoring Assorted editorial nits and cleanup, refactoring
-00: Initial IETF Internet-Draft submission. -00: Initial IETF Internet-Draft submission.
Added optional version attribute to entry Added optional version attribute to entry
(PaceEntryElementNeedsVersionAttribute). (PaceEntryElementNeedsVersionAttribute).
Added hreflang attribute (PaceHrefLang). Added hreflang attribute (PaceHrefLang).
Clarified inheritence of copyright element (PaceItemCopyright). Clarified inheritence of copyright element (PaceItemCopyright).
Added xml:lang to entries (PaceItemLang). Added xml:lang to entries (PaceItemLang).
Tweaked Infoset-related language (PaceNoInfoSet). Tweaked Infoset-related language (PaceNoInfoSet).
Clarified lack of structure in version attribute Clarified lack of structure in version attribute
(PaceVersionAsText). (PaceVersionAsText).
Changed approach to XML Base (PaceXmlBaseEverywhere). Changed approach to XML Base (PaceXmlBaseEverywhere).
Added XML Base processing to atom:id (PaceXmlBaseId). Added XML Base processing to atom:id (PaceXmlBaseId).
Various editorial cleanup and adjustments for IETF publication. Various editorial cleanup and adjustments for IETF publication.
Intellectual Property Statement Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
 End of changes. 

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