draft-ietf-atompub-format-07.txt   draft-ietf-atompub-format-08.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 2, 2005 March 31, 2005 Expires: October 20, 2005 April 18, 2005
The Atom Syndication Format The Atom Syndication Format
draft-ietf-atompub-format-07 draft-ietf-atompub-format-08
Status of this Memo Status of this Memo
This document is an Internet-Draft and is subject to all provisions This document is an Internet-Draft and is subject to all provisions
of Section 3 of RFC 3667. By submitting this Internet-Draft, each of Section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with which he or she become aware will be disclosed, in accordance with
RFC 3668. RFC 3668.
skipping to change at page 1, line 35 skipping to change at page 1, line 35
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 2, 2005. This Internet-Draft will expire on October 20, 2005.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
This document specifies Atom, an XML-based Web content and metadata This document specifies Atom, an XML-based Web content and metadata
syndication format. syndication format.
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4.2.8 The "atom:image" Element . . . . . . . . . . . . . . . 23 4.2.8 The "atom:image" Element . . . . . . . . . . . . . . . 23
4.2.9 The "atom:link" Element . . . . . . . . . . . . . . . 24 4.2.9 The "atom:link" Element . . . . . . . . . . . . . . . 24
4.2.10 The "atom:published" Element . . . . . . . . . . . . 26 4.2.10 The "atom:published" Element . . . . . . . . . . . . 26
4.2.11 The "atom:source" Element . . . . . . . . . . . . . 26 4.2.11 The "atom:source" Element . . . . . . . . . . . . . 26
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 . . . . . . . . . . . . . 27
4.2.14 The "atom:title" Element . . . . . . . . . . . . . . 27 4.2.14 The "atom:title" Element . . . . . . . . . . . . . . 27
4.2.15 The "atom:updated" Element . . . . . . . . . . . . . 27 4.2.15 The "atom:updated" Element . . . . . . . . . . . . . 27
5. Securing Atom Documents . . . . . . . . . . . . . . . . . . 29 5. Securing Atom Documents . . . . . . . . . . . . . . . . . . 29
6. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 30 6. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 30
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 32 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 33
8. Security Considerations . . . . . . . . . . . . . . . . . . 34 8. Security Considerations . . . . . . . . . . . . . . . . . . 35
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 35 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
9.1 Normative References . . . . . . . . . . . . . . . . . . . 35 9.1 Normative References . . . . . . . . . . . . . . . . . . . 36
9.2 Informative References . . . . . . . . . . . . . . . . . . 36 9.2 Informative References . . . . . . . . . . . . . . . . . . 37
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 37 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 38
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 38 A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 39
B. Collected RELAX NG Compact Schema . . . . . . . . . . . . . 39 B. RELAX NG Compact Schema . . . . . . . . . . . . . . . . . . 40
C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 47 C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 48
Intellectual Property and Copyright Statements . . . . . . . 50 Intellectual Property and Copyright Statements . . . . . . . 51
1. Introduction 1. Introduction
Atom is an XML-based document format that describes lists of related Atom is an XML-based document format that describes lists of related
information known as "feeds". Feeds are composed of a number of information known as "feeds". Feeds are composed of a number of
items, known as "entries", each with an extensible set of attached items, known as "entries", each with an extensible set of attached
metadata. For example, each entry has a title. metadata. For example, each entry has a title.
The primary use case that Atom addresses is the syndication of Web The primary use case that Atom addresses is the syndication of Web
content such as Weblogs and news headlines to Web sites as well as content such as Weblogs and news headlines to Web sites as well as
directly to user agents. However, nothing precludes it from being directly to user agents.
used for other purposes and kinds of content.
1.1 Examples 1.1 Examples
A minimal, single-entry Atom Feed Document: A minimal, single-entry Atom Feed Document:
<?xml version="1.0" encoding="utf-8"?> <?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-07"> <feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-08">
<title>Example Feed</title> <title>Example Feed</title>
<link href="http://example.org/"/> <link href="http://example.org/"/>
<updated>2003-12-13T18:30:02Z</updated> <updated>2003-12-13T18:30:02Z</updated>
<author> <author>
<name>John Doe</name> <name>John Doe</name>
</author> </author>
<entry> <entry>
<title>Atom-Powered Robots Run Amok</title> <title>Atom-Powered Robots Run Amok</title>
<link href="http://example.org/2003/12/13/atom03"/> <link href="http://example.org/2003/12/13/atom03"/>
<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id> <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
<updated>2003-12-13T18:30:02Z</updated> <updated>2003-12-13T18:30:02Z</updated>
<content>Some text.</content> <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-07"> <feed xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-08">
<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> <copyright>Copyright (c) 2003, Mark Pilgrim</copyright>
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1.2 Notational Conventions 1.2 Notational Conventions
This specification describes conformance in terms of two artifacts; This specification describes conformance in terms of two artifacts;
Atom Feed Documents and Atom Entry documents. Additionally, it Atom Feed Documents and Atom Entry documents. Additionally, it
places some requirements on Atom Processors. places some requirements on Atom Processors.
This specification uses XML Namespaces [W3C.REC-xml-names-19990114] This specification uses XML Namespaces [W3C.REC-xml-names-19990114]
to uniquely identify XML element names. It uses the following to uniquely identify XML element names. It uses the following
namespace prefix for the indicated namespace URI; namespace prefix for the indicated namespace URI;
"atom": http://purl.org/atom/ns#draft-ietf-atompub-format-07 "atom": http://purl.org/atom/ns#draft-ietf-atompub-format-08
[[anchor4: This paragraph to be removed by the RFC Editor. The
namespace here is a temporary one and will be changed when the IESG
approves this document as a standard. At that time, the namespace
will be drawn from W3C URI space. The choice of that namespace will
be coordinated between the IETF and W3C through their respective
liaisons.]]
Note that the choice of any namespace prefix is arbitrary and not Note that the choice of any namespace prefix is arbitrary and not
semantically significant. semantically significant.
Atom is specified using terms from the XML Infoset Atom is specified using terms from the XML Infoset
[W3C.REC-xml-infoset-20040204]. However, this specification uses a [W3C.REC-xml-infoset-20040204]. However, this specification uses a
shorthand for two common terms; the phrase "Information Item" is shorthand for two common terms; the phrase "Information Item" is
omitted when naming Element Information Items and Attribute omitted when naming Element Information Items and Attribute
Information Items. Information Items.
Therefore, when this specification uses the term "element," it is Therefore, when this specification uses the term "element," it is
referring to an Element Information Item in Infoset terms. Likewise, referring to an Element Information Item in Infoset terms. Likewise,
when it uses the term "attribute," it is referring to an Attribute when it uses the term "attribute," it is referring to an Attribute
Information Item. Information Item.
Some sections of this specification are illustrated with fragments of Some sections of this specification are illustrated with fragments of
a non-normative RELAX NG Compact schema [RELAX-NG]. However, the a non-normative RELAX NG Compact schema [RELAX-NG]. However, the
text of this specification provides the definition of conformance. A text of this specification provides the definition of conformance. A
collected schema appears in Appendix B. complete schema appears in Appendix B.
Some sections of this specification are illustrated with Augmented
Backus-Naur Form (ABNF), a format used to represent permissible
strings in a protocol or language, as defined in [RFC2234].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, [RFC2119], as document are to be interpreted as described in BCP 14, [RFC2119], as
scoped to those conformance targets. scoped to those conformance targets.
2. Atom Documents 2. Atom Documents
This specification describes two kinds of Atom Documents; Atom Feed This specification describes two kinds of Atom Documents; Atom Feed
Documents and Atom Entry Documents. Documents and Atom Entry Documents.
An Atom Feed Document is a representation of an Atom feed, including An Atom Feed Document is a representation of an Atom feed, including
metadata about the feed, and some or all of the entries associated metadata about the feed, and some or all of the entries associated
with it. Its root is the atom:feed element. with it. Its root is the atom:feed element.
An Atom Entry Document represents exactly one Atom entry, outside of An Atom Entry Document represents exactly one Atom entry, outside of
the context of an Atom feed. Its root is the atom:entry element. the context of an Atom feed. Its root is the atom:entry element.
namespace atom = namespace atom =
"http://purl.org/atom/ns#draft-ietf-atompub-format-07" "http://purl.org/atom/ns#draft-ietf-atompub-format-08"
start = atomFeed | atomEntry start = atomFeed | atomEntry
Both kinds of Atom documents are specified in terms of the XML Both kinds of Atom documents are specified in terms of the XML
Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204] and Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204] and
identified with the "application/atom+xml" media type. Atom identified with the "application/atom+xml" media type. Atom
Documents MUST be well-formed XML. Documents MUST be well-formed XML. This specification does not
define a DTD for Atom Documents, and hence does not require them to
Atom constrains the appearance and content of elements and be valid (in the sense used by XML).
attributes; unless otherwise stated, Atom Documents MAY contain other
Information Items as appropriate.
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. XML Base [W3C.REC-xmlbase-20010627] processing MUST be
applied to any relative reference [RFC3987] present in an Atom applied to any relative reference [RFC3987] present in an Atom
Document. This includes such elements and attributes as specified by Document. This includes such elements and attributes as specified by
Atom itself, as well as those specified by extensions to Atom. Atom itself, as well as those specified by extensions to Atom.
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 children. The language context is only significant
for elements and attributes declared to be "language-sensitive" by for elements and attributes declared to be "language-sensitive" by
this specification. Requirements regarding the content and this specification. Requirements regarding the content and
interpretation of xml:lang are specified in XML 1.0 interpretation of xml:lang are specified in XML 1.0
[W3C.REC-xml-20040204], Section 2.12. [W3C.REC-xml-20040204], Section 2.12.
atomCommonAttributes = atomCommonAttributes =
attribute xml:base { atomUri }?, attribute xml:base { atomUri }?,
attribute xml:lang { atomLanguageTag }? attribute xml:lang { atomLanguageTag }?
Atom allows the use of IRIs [RFC3987], as well as URIs [RFC3986]. Atom allows the use of IRIs [RFC3987], as well as URIs [RFC3986].
For resolution, IRIs can easily be converted to URIs. When comparing IRIs can easily be converted to URIs. Every URI is an IRI, so any
IRIs serving as atom:id values, they MUST NOT be converted to URIs. URI can be used where an IRI is needed. When comparing IRIs serving
By definition, every URI is an IRI, so any URI can be used where an as atom:id values, they MUST NOT be converted to URIs.
IRI is needed.
Atom is an extensible format. See the section titled 'Extending Atom is an extensible format. See Section 6 of this document for a
Atom' later in this document for a full description of how Atom full description of how Atom Documents can be extended.
Documents can be extended.
Atom Processors MAY keep state (e.g., metadata in atom:feed, entries) Atom Processors MAY keep state (e.g., metadata in atom:feed, entries)
sourced from Atom Feed Documents and combine them with other Atom sourced from Atom Feed Documents and combine them with other Atom
Feed Documents, in order to facilitate a contiguous view of the Feed Documents, in order to facilitate a contiguous view of the
contents of a feed. The manner in which Atom Feed Documents are contents of a feed. The manner in which Atom Feed Documents are
combined in order to reconstruct a feed (e.g., updating entries and combined in order to reconstruct a feed (e.g., updating entries and
metadata, dealing with missing entries) is out of the scope of this metadata, dealing with missing entries) is out of the scope of this
specification, but may be defined by an extension to Atom. specification.
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.
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attribute type { "xhtml" }, attribute type { "xhtml" },
xhtmlDiv xhtmlDiv
atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct
3.1.1 The "type" Attribute 3.1.1 The "type" Attribute
Text constructs MAY have a "type" attribute. When present, the value Text constructs MAY have a "type" attribute. When present, the value
MUST be one of "text", "html" or "xhtml". If the "type" attribute is MUST be one of "text", "html" or "xhtml". If the "type" attribute is
not provided, Atom Processors MUST behave as though it were present not provided, Atom Processors MUST behave as though it were present
with a value of "text". with a value of "text". MIME media types [MIMEREG] MUST NOT be used
as values for the "type" attribute.
Note that MIME media types [RFC2045] are not acceptable values for
the "type" attribute.
3.1.1.1 Text 3.1.1.1 Text
Example atom:title with text content: Example atom:title with text content:
... ...
<title type="text"> <title type="text">
Less: &lt; Less: &lt;
</title> </title>
... ...
If the value is "text", the content of the Text construct MUST NOT If the value is "text", the content of the Text construct MUST NOT
contain child elements. Such text is intended to be presented to contain child elements. Such text is intended to be presented to
humans in a readable fashion. Thus, Atom Processors MAY display it humans in a readable fashion. Thus, Atom Processors MAY collapse
using normal text rendering techniques such as proportional fonts, white-space (including line-breaks), and display the text using
white-space collapsing, and justification. typographic techniques such as justification and proportional fonts.
3.1.1.2 HTML 3.1.1.2 HTML
Example atom:title with HTML content: Example atom:title with HTML content:
... ...
<title type="html"> <title type="html">
Less: &lt;em> &amp;lt; &lt;/em> Less: &lt;em> &amp;lt; &lt;/em>
</title> </title>
... ...
If the value of "type" is "html", the content of the Text construct If the value of "type" is "html", the content of the Text construct
MUST NOT contain child elements, and SHOULD be suitable for handling MUST NOT contain child elements, and SHOULD be suitable for handling
as HTML [W3C.REC-html401-19991224]. Any markup within MUST be as HTML [HTML]. Any markup within MUST be escaped; for example,
escaped; for example, "<br>" as "&lt;br>". HTML markup within SHOULD "<br>" as "&lt;br>". HTML markup within SHOULD be such that it could
be such that it could validly appear directly within an HTML <DIV> validly appear directly within an HTML <DIV> element, after
element, after unescaping. Atom Processors that display such content unescaping. Atom Processors that display such content MAY use that
MAY use that markup to aid in its display. markup to aid in its display.
3.1.1.3 XHTML 3.1.1.3 XHTML
Example atom:title with XHTML content: Example atom:title with XHTML content:
... ...
<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 [W3C.REC-xhtml-basic-20001219]. MUST be a single XHTML div element [XHTML]. The XHTML div MUST
The XHTML div MUST contain XHTML text and markup that could validly contain XHTML text and markup that could validly appear within an
appear within an XHTML div element. The XHTML div element itself XHTML div element. The XHTML div element itself MUST NOT be
MUST NOT be considered part of the content. Atom Processors which considered part of the content. Atom Processors which display the
display the content MAY use the markup to aid in displaying it. content MAY use the markup to aid in displaying it. Escaped
Escaped characters, such as "&" and ">", represent those characters, characters, such as "&" and ">", represent those characters, not
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>
... ...
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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:email element, but MUST NOT contain more than one. Its content atom:email element, but MUST NOT contain more than one. Its content
MUST conform to the addr-spec BNF rule in [RFC2822]. MUST conform to the "addr-spec" 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
extended date-time form ABNF rule in [RFC3339]. In addition, an "date-time" production in [RFC3339]. In addition, an uppercase "T"
uppercase "T" character MUST be used to separate date and time, and character MUST be used to separate date and time, and an uppercase
an uppercase "Z" character MUST be present in the absence of a "Z" character MUST be present in the absence of a numeric time zone
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].
Date values SHOULD be as accurate as possible. For example, it would Date values SHOULD be as accurate as possible. For example, it would
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} }
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 exactly one atom:author element,
UNLESS all of the atom:feed element's child atom:entry elements UNLESS all of the atom:feed element's child atom:entry elements
contain an atom:author element. atom:feed elements MUST NOT contain an atom:author element.
contain more than 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 o atom:feed elements MUST NOT contain more than one atom:copyright
element. element.
o atom:feed elements MUST NOT contain more than one atom:generator o atom:feed elements MUST NOT contain more than one atom:generator
element. element.
o atom:feed elements MUST NOT contain more than one atom:icon o atom:feed elements MUST NOT contain more than one atom:icon
element. element.
o atom:feed elements MUST NOT contain more than one atom:image o atom:feed elements MUST NOT contain more than one atom:image
element. element.
o atom:feed elements MUST NOT contain more than one atom:id element. o atom:feed elements MUST NOT contain more than one atom:id element.
o atom:feed elements MUST contain at least one atom:link element o atom:feed elements MUST contain at least one atom:link element
with a relation of "alternate". with a relation of "alternate".
o atom:feed elements SHOULD contain one atom:link element with a rel o atom:feed elements SHOULD contain one atom:link element with a rel
attribute value of "self". This URI identifies the feed and a attribute value of "self". This URI identifies the feed and a
representation equivalent to the feed. representation equivalent to the feed.
o atom:feed elements MUST NOT contain more than one atom:link o atom:feed elements MUST NOT contain more than one atom:link
element with a rel attribute value of "alternate" that has the element with a rel attribute value of "alternate" that has the
same type attribute value. If a feed's atom:link element with same type attribute value. atom:feed elements MAY contain
type="alternate" resolves to an HTML document, then that document
SHOULD have a autodiscovery link element [Atom-autodiscovery] that
reflects back to the feed. atom:feed elements MAY contain
additional atom:link elements beyond those described above. additional atom:link elements beyond those described above.
o atom:feed elements MUST NOT contain more than one atom:subtitle o atom:feed elements MUST NOT contain more than one atom:subtitle
element. element.
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 o atom:feed elements MUST NOT contain atom:entry elements with
identical atom:id values. identical atom:id values.
4.1.2 The "atom:entry" Element 4.1.2 The "atom:entry" Element
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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 exactly one atom:author element,
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.
atom:entry elements MUST NOT contain more than one atom:author o atom:entry elements MUST NOT contain more than one atom:author
element. 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 o atom:entry elements MUST NOT contain more than one atom:copyright
element. element.
o atom:entry elements MUST contain exactly one atom:id element. o atom:entry elements MUST contain exactly one atom:id element.
o atom:entry elements that contain no child atom:content element o atom:entry elements that contain no child atom:content element
MUST contain at least one atom:link element with a rel attribute MUST contain at least one atom:link element with a rel attribute
value of "alternate". atom:entry elements MUST NOT contain more value of "alternate".
than one atom:link element with a rel attribute value of o atom:entry elements MUST NOT contain more than one atom:link
"alternate" that has the same combination of type and hreflang element with a rel attribute value of "alternate" that has the
attribute values. atom:entry elements MAY contain additional same combination of type and hreflang attribute values.
atom:link elements beyond those described above. o atom:entry elements MAY contain additional atom:link elements
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: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 o atom:entry elements MUST contain an atom:summary element in any of
the following cases: the following cases:
* the atom:entry element contains no atom:content element. * the atom:entry element contains no atom:content element.
* the atom:entry contains an atom:content that has a "src" * the atom:entry contains an atom:content that has a "src"
attribute (and is thus empty). attribute (and is thus empty).
* the atom:entry contains content that is encoded in Base64; i.e. * the atom:entry contains content that is encoded in Base64; i.e.
the "type" attribute of atom:content is a MIME media type the "type" attribute of atom:content is a MIME media type
[RFC2045] and does not begin with "text/" nor end with "+xml". [MIMEREG] and does not begin with "text/" nor end with "+xml".
o atom:entry elements MUST NOT contain more than one atom:summary o atom:entry elements MUST NOT contain more than one atom:summary
element. element.
o atom:entry elements MUST have exactly one "atom:title" element. o atom:entry elements MUST have exactly one "atom:title" element.
o atom:entry elements MUST contain exactly one atom:updated element. o atom:entry elements MUST contain exactly one atom:updated element.
4.1.3 The "atom:content" Element 4.1.3 The "atom:content" Element
The "atom:content" element either contains or links to the content of The "atom:content" element either contains or links to the content of
the entry. The content of atom:content is language-sensitive. the entry. The content of atom:content is language-sensitive.
skipping to change at page 17, line 28 skipping to change at page 17, line 28
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|anyElement)* (text|anyForeignElement)*
} }
atomOutOfLineContent = atomOutOfLineContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { atomMediaType }?, attribute type { atomMediaType }?,
attribute src { atomUri }, attribute src { atomUri },
empty empty
} }
atomContent = atomInlineTextContent atomContent = atomInlineTextContent
| atomInlineXHTMLContent | atomInlineXHTMLContent
| atomInlineOtherContent | atomInlineOtherContent
| atomOutOfLineContent | atomOutOfLineContent
4.1.3.1 The "type" attribute 4.1.3.1 The "type" attribute
atom:content MAY have a "type" attribute. When present, the value On the atom:content element, the value of the "type" attribute MAY be
MAY be one of "text", "html", or "xhtml". Failing that, it MUST be a one of "text", "html", or "xhtml". Failing that, it MUST be a MIME
MIME media type [RFC2045] with a discrete top-level type (see Section media type, but MUST NOT be a composite type (see Section 4.2.6 of
5 of [RFC2045]). If the type attribute is not provided, Atom [MIMEREG]). If the type attribute is not provided, Atom Processors
Processors MUST behave as though it were present with a value of MUST behave as though it were present with a value of "text".
"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
Processors MAY use the IRI to retrieve the content. If the "src" Processors MAY use the IRI to retrieve the content. If the "src"
attribute is present, atom:content MUST be empty. That is to say, attribute is present, atom:content MUST be empty.
the content may be retrievable using "src=" IRI, or it may be
contained within atom:content, but not both.
If the "src" attribute is present, the "type" attribute SHOULD be If the "src" attribute is present, the "type" attribute SHOULD be
provided and MUST be a MIME media type [RFC2045], rather than "text", provided and MUST be a MIME media type [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-provided media type is authoritative. server-provided media type is authoritative.
If the value of type begins with "text/" or ends with "+xml", the If the value of type begins with "text/" or ends with "+xml", the
content SHOULD be local; that is to say, no "src" attribute should be content SHOULD be local; that is to say, no "src" attribute should be
provided. 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 display it using normal text rendering techniques such as MAY collapse white-space (including line-breaks), and display the
proportional fonts, white-space collapsing, and justification. text using typographic techniques such as justification and
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 [W3C.REC-html401-19991224]. The HTML markup handling as HTML [HTML]. The HTML markup must be escaped; for
must be escaped; for example, "<br>" as "&lt;br>". The HTML example, "<br>" as "&lt;br>". The HTML markup SHOULD be such
markup SHOULD be such that it could validly appear directly that it could validly appear directly within an HTML <DIV>
within an HTML <DIV> element. Atom Processors that display the element. Atom Processors that display the content MAY use the
content SHOULD 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 MUST be a single XHTML div element [XHTML], and SHOULD be
[W3C.REC-xhtml-basic-20001219]. The XHTML div MUST contain XHTML suitable for handling as XHTML. The XHTML div element itself
text and markup that could validly appear within an XHTML div MUST NOT be considered part of the content. Atom Processors that
element. The XHTML div element itself MUST NOT be considered display the content MAY use the markup to aid in displaying it.
part of the content. Atom Processors that display the content Escaped characters, such as "&" and ">", represent those
MAY use the markup to aid in displaying it. Escaped markup is characters, not markup.
interpreted as a text representation of markup, and MUST NOT be
interpreted as markup itself.
4. If the value of "type" ends with "+xml" or "/xml" 4. If the value of "type" ends with "+xml" or "/xml"
(case-insensitive), the content of atom:content may include child (case-insensitive), the content of atom:content MAY include child
elements, and SHOULD be suitable for handling as the indicated elements, and SHOULD be suitable for handling as the indicated
media type. If the "src" attribute is not provided, this would media type. If the "src" attribute is not provided, this would
normally mean that the "atom:content" element would contain a normally mean that the "atom:content" element would contain a
single child element which would serve as the root element of the single child element which would serve as the root element of the
XML document of the indicated type. 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 [RFC3548], which when decoded SHOULD
be suitable for handling as the indicated media type. In this be suitable for handling as the indicated media type. In this
case, the characters in the Base64 encoding may be preceded and case, the characters in the Base64 encoding MAY be preceded and
followed in the atom:content element by whitespace, and lines are followed in the atom:content element by white-space, and lines
separated by a single newline (U+000A) character. 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 22, line 33 skipping to change at page 22, line 33
republished, exported or imported, the content of its atom:id element republished, exported or imported, the content of its atom:id element
MUST NOT change. Put another way, an atom:id element pertains to all MUST NOT change. Put another way, an atom:id element pertains to all
instantiations of a particular Atom entry or feed; revisions retain instantiations of a particular Atom entry or feed; revisions retain
the same content in their atom:id elements. It is suggested that the the same content in their atom:id elements. It is suggested that the
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 is equivalent if dereferenced, the following normalization strategy
strongly encouraged 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 "/".
skipping to change at page 24, line 35 skipping to change at page 24, line 35
MUST have a href attribute, whose value MUST be a IRI reference MUST have a href attribute, whose value MUST be a IRI reference
[RFC3987]. [RFC3987].
4.2.9.2 The "rel" Attribute 4.2.9.2 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".
ABNF for the "rel" attribute: The value of "rel" MUST be string that is non-empty, and matches the
"isegment-nz-nc" or "IRI" production in [RFC3987]. Note that use of
rel_attribute = isegment-nz-nc / IRI a relative reference is not allowed. If a name is given,
implementations MUST consider the link relation type to be equivalent
The value of "rel" MUST be string that is non-empty, does not contain to the same name registered within the IANA Registry of Link
any colon (":") characters, and matches the "isegment-nz-nc" or "IRI" Relations Section 7, and thus the IRI that would be obtained by
ABNF forms in [RFC3987]. Note that use of a relative reference is appending the value of the rel attribute to the string
not allowed. If a name is given, implementations MUST consider the "http://www.iana.org/assignments/relation/". The value of "rel"
link relation type to be equivalent to the same name registered describes the meaning of the link, but does not impose any behavioral
within the IANA Registry of Link Relations Section 7, and thus the requirements on implementations.
IRI that would be obtained by appending the value of the rel
attribute to the string "http://www.iana.org/assignments/relation/".
The value of "rel" describes the meaning of the link, but does not
impose any behavioral requirements on implementations.
This document defines five initial values for the Registry of Link This document defines five initial values for the Registry of Link
Relations: Relations:
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
described by the containing element. For example, the feed for a described by the containing element. For example, the feed for a
site that discusses the performance of the search engine at site that discusses the performance of the search engine at
"http://search.example.com" might contain, as a child of "http://search.example.com" might contain, as a child of
atom:feed: atom:feed:
<link rel="related" href="http://search.example.com/"> <link rel="related" href="http://search.example.com/"/>
An identical link might appear as a child of any atom:entry whose An identical link might appear as a child of any atom:entry whose
content contains a discussion of that same search engine. content contains a discussion of that same search engine.
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 may require special handling by consuming large in size and might require special handling by consuming
software. For Link elements with rel="enclosure", the length software. For Link elements with rel="enclosure", the length
attribute SHOULD be provided. attribute SHOULD be 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 4.2.9.3 The "type" Attribute
The "type" attribute's value is an advisory media type; it is a hint On the link element, the "type" attribute's value is an advisory
about the type of the representation that is expected to be returned media type; it is a hint about the type of the representation that is
when the value of the href attribute is dereferenced. Note that the expected to be returned when the value of the href attribute is
type attribute does not override the actual media type returned with dereferenced. Note that the type attribute does not override the
the representation. Link elements MAY have a type attribute, whose actual media type returned with the representation. Link elements
value MUST conform to the syntax of a MIME media type [RFC2045]. MAY have a type attribute, whose value MUST conform to the syntax of
a MIME media type [MIMEREG].
4.2.9.4 The "hreflang" Attribute 4.2.9.4 The "hreflang" Attribute
The "hreflang" attribute's content describes the language of the The "hreflang" attribute's content describes the language of the
resource pointed to by the href attribute. When used together with resource pointed to by the href attribute. When used together with
the rel="alternate", it implies a translated version of the entry. the rel="alternate", it implies a translated version of the entry.
Link elements MAY have an hreflang attribute, whose value MUST be a Link elements MAY have an hreflang attribute, whose value MUST be a
language tag [RFC3066]. language tag [RFC3066].
4.2.9.5 The "title" Attribute 4.2.9.5 The "title" Attribute
skipping to change at page 29, line 24 skipping to change at page 29, line 24
Signature, as described by XML-Signature and Syntax Processing Signature, as described by XML-Signature and Syntax Processing
[W3C.REC-xmldsig-core-20020212]. [W3C.REC-xmldsig-core-20020212].
Processors MUST NOT reject an Atom Document containing such a Processors MUST NOT reject an Atom Document containing such a
signature because they are not capable of verifying it; they MUST signature because they are not capable of verifying it; they MUST
continue processing and MAY inform the user of their failure to continue processing and MAY inform the user of their failure to
validate the signature. validate the signature.
In other words, the presence of an element with the namespace 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
definitions explicitly specify such a capability. definitions explicitly specify such a capability.
5.2 Encryption 5.2 Encryption
The root of an Atom Document (i.e., atom:feed in an Atom Feed The root of an Atom Document (i.e., atom:feed in an Atom Feed
Document, atom:entry in an Atom Entry Document) MAY be encrypted, Document, atom:entry in an Atom Entry Document) MAY be encrypted,
using the mechanisms described by XML Encryption Syntax and using the mechanisms described by XML Encryption Syntax and
skipping to change at page 30, line 16 skipping to change at page 30, line 16
6.1 Extensions From Non-Atom Vocabularies 6.1 Extensions From Non-Atom Vocabularies
This specification describes Atom's XML markup vocabulary. Markup This specification describes Atom's XML markup vocabulary. Markup
from other vocabularies ("foreign markup") can be used in an Atom from other vocabularies ("foreign markup") can be used in an Atom
document. Note that the atom:content element is designed to support document. Note that the atom:content element is designed to support
the inclusion of arbitrary foreign markup. the inclusion of arbitrary foreign markup.
6.2 Extensions To the Atom Vocabulary 6.2 Extensions To the Atom Vocabulary
Future versions of this specification may add new elements and Future versions of this specification 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 Software Processing of Foreign Markup
Software processing an Atom Document which encounters foreign markup Software processing an Atom Document which encounters foreign markup
in a location that is legal according to this specification MUST NOT in a location that is legal according to this specification MUST NOT
stop processing or signal an error. It may be the case that the stop processing or signal an error. It might be the case that the
software is able to process the foreign markup correctly and does so. software is able to process the foreign markup correctly and does so.
Otherwise, such markup is termed "unknown foreign markup". Otherwise, such markup is termed "unknown foreign markup".
When unknown foreign markup is encountered as a child of atom:entry, When unknown foreign markup is encountered as a child of atom:entry,
atom:feed, or a Person construct, software MAY bypass the markup and atom:feed, or a Person construct, software MAY bypass the markup and
any textual content and MUST NOT change its behavior as a result of any textual content and MUST NOT change its behavior as a result of
the markup's presence. 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
skipping to change at page 31, line 20 skipping to change at page 31, line 20
elements of Person constructs are considered to apply to the elements of Person constructs are considered to apply to the
construct. The role of other foreign markup is undefined by this construct. The role of other foreign markup is undefined by this
specification. 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 =
element * - atom:* {
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 =
element * - atom:* {
(attribute * { text }+,
(text|anyElement)*)
| (attribute * { text }*,
(text?, anyElement+, (text|anyElement)*))
}
The structure of a Structured Extension element, including the order The structure of a Structured Extension element, including the order
of its child elements, could be significant. of its child elements, could be significant.
This specification does not provide an interpretation of a Structured This specification does not provide an interpretation of a Structured
Extension element. The syntax of the XML contained in the element, Extension element. The syntax of the XML contained in the element,
and an interpretation of how the element relates to its containing and an interpretation of how the element relates to its containing
element is defined by the specification of the Atom extension. element is defined by the specification of the Atom extension.
7. IANA Considerations 7. IANA Considerations
skipping to change at page 32, line 43 skipping to change at page 33, line 43
Magic number(s): As specified for "application/xml" in [RFC3023], Magic number(s): As specified for "application/xml" in [RFC3023],
section 3.2. section 3.2.
File extension: .atom File extension: .atom
Fragment identifiers: As specified for "application/xml" in Fragment identifiers: As specified for "application/xml" in
[RFC3023], section 5. [RFC3023], section 5.
Base URI: As specified in [RFC3023], section 6. Base URI: As specified in [RFC3023], section 6.
Macintosh File Type code: TEXT Macintosh File Type code: TEXT
Person and email address to contact for further information: Mark Person and email address to contact for further information: Mark
Nottingham <mnot@pobox.com> Nottingham <mnot@pobox.com>
Intended usage: COMMON Intended usage: COMMON
Author/Change controller: This specification's author(s). Author/Change controller: IESG
[[anchor61: update upon publication]]
7.1 Registry of Link Relations 7.1 Registry of Link Relations
This registry is maintained by IANA and initially contains five This registry is maintained by IANA and initially contains five
values: "alternate", "related", "self", "enclosure", and "via". New values: "alternate", "related", "self", "enclosure", and "via". New
assignments are subject to IESG Approval, as outlined in [RFC2434]. assignments are subject to IESG Approval, as outlined in [RFC2434].
Requests should be made by email to IANA, which will then forward the Requests should be made by email to IANA, which will then forward the
request to the IESG requesting approval. The request should contain request to the IESG requesting approval. The request should use the
discussion of at least the following five topics: following template:
o A value for the "rel" attribute that conforms to the syntax rule o Attribute Value: ( A value for the "rel" attribute that conforms
given in Section 4.2.9.2 to the syntax rule given in Section 4.2.9.2 )
o Common name for link type. o Description:
o Description of link type semantics. o Expected display characteristics:
o Expected display characteristics. o Security considerations:
o Security considerations.
8. Security Considerations 8. Security Considerations
8.1 HTML and XHTML Content 8.1 HTML and XHTML Content
Text constructs and atom:content allow the delivery of HTML and XHTML Text constructs and atom:content allow the delivery of HTML and XHTML
to receiving software, which may process it. Many elements in these to receiving software. Many elements in these languages are
languages are considered 'unsafe' in that they open clients to one or considered 'unsafe' in that they open clients to one or more types of
more types of attack. Implementers of software which processes Atom attack. Implementers of software which processes Atom should
should carefully consider their handling of every type of element carefully consider their handling of every type of element when
when processing incoming (X)HTML in Atom documents. See the security processing incoming (X)HTML in Atom documents. See the security
sections of [RFC2854] and [W3C.REC-html401-19991224] for guidance. sections of [RFC2854] and [HTML] for guidance.
Atom Processors should pay particular attention to the security of Atom Processors should pay particular attention to the security of
the IMG, SCRIPT, EMBED, OBJECT, FRAME, FRAMESET, IFRAME, META, and the IMG, SCRIPT, EMBED, OBJECT, FRAME, FRAMESET, IFRAME, META, and
LINK elements, but other elements may also have negative security LINK elements, but other elements 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
skipping to change at page 35, line 9 skipping to change at page 36, line 9
Atom documents can be encrypted and signed using Atom documents can be encrypted and signed using
[W3C.REC-xmlenc-core-20021210] and [W3C.REC-xmldsig-core-20020212], [W3C.REC-xmlenc-core-20021210] and [W3C.REC-xmldsig-core-20020212],
respectively, and are subject to the security considerations implied respectively, and are subject to the security considerations implied
by their use. by their use.
9. References 9. References
9.1 Normative References 9.1 Normative References
[Atom-autodiscovery] [HTML] Raggett, D., Hors, A. and I. Jacobs, "HTML 4.01
Pilgrim, M., "Atom Feed Autodiscovery", work-in-progress, Specification", W3C REC REC-html401-19991224, December
August 2004. 1999, <http://www.w3.org/TR/1999/REC-html401-19991224>.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [MIMEREG] Freed, N. and J. Klensin, "Media Type Specifications and
Extensions (MIME) Part One: Format of Internet Message Registration Procedures", work-in-progress
Bodies", RFC 2045, November 1996. (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.
[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
2001. 2001.
[RFC2854] Connolly, D. and L. Masinter, "The 'text/html' Media [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
skipping to change at page 35, line 48 skipping to change at page 36, line 45
[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-html401-19991224]
Raggett, D., Hors, A. and I. Jacobs, "HTML 4.01
Specification", W3C REC REC-html401-19991224, December
1999.
[W3C.REC-xhtml-basic-20001219]
Baker, M., Ishikawa, M., Matsui, S., Stark, P., Wugofski,
T. and T. Yamakami, "XHTML Basic", W3C
REC REC-xhtml-basic-20001219, December 2000.
[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. and
E. Maler, "Extensible Markup Language (XML) 1.0 (Third 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>.
[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, February
2004. 2004,
<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>.
[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, June
2001. 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>.
[W3C.REC-xmlenc-core-20021210] [W3C.REC-xmlenc-core-20021210]
Reagle, J. and D. Eastlake, "XML Encryption Syntax and Reagle, J. and D. Eastlake, "XML Encryption Syntax and
Processing", W3C REC REC-xmlenc-core-20021210, December Processing", W3C REC REC-xmlenc-core-20021210, December
2002. 2002,
<http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.
[XHTML] Altheim, M., Boumphrey, F., McCarron, S., Dooley, S.,
Schnitzenbaumer, S. and T. Wugofski, "Modularization of
XHTML[TM]", W3C REC REC-xhtml-modularization-20010410,
April 2001,
<http://www.w3.org/TR/2001/REC-xhtml-modularization-200104
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]
OASIS Technical Committee: RELAX NG, "RELAX NG Clark, J., "RELAX NG Compact Syntax", December 2001,
Specification", December 2001. <http://www.oasis-open.org/committees/relax-ng/compact-200
21121.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>.
[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, October
2004. 2004,
<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 39, line 5 skipping to change at page 40, line 5
URI: http://boswijck.com URI: http://boswijck.com
Appendix A. Contributors Appendix A. Contributors
The following people contributed to preliminary drafts of this The following people contributed to preliminary drafts of this
document: Tim Bray, Mark Pilgrim, and Sam Ruby. Norman Walsh document: Tim Bray, Mark Pilgrim, and Sam Ruby. Norman Walsh
provided the Relax NG schema. The content and concepts within are a provided the Relax NG schema. The content and concepts within are a
product of the Atom community and the Atom Publishing Format and product of the Atom community and the Atom Publishing Format and
Protocol Working Group. Protocol Working Group.
Appendix B. Collected RELAX NG Compact Schema Appendix B. 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 07 # Atom Format Specification Version 08
namespace atom = namespace atom =
"http://purl.org/atom/ns#draft-ietf-atompub-format-07" "http://purl.org/atom/ns#draft-ietf-atompub-format-08"
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"
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 }?
skipping to change at page 40, line 14 skipping to change at page 41, line 14
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']" test = "atom:link[@rel='alternate']"
~ "or atom:link[not(@rel)]"
"An atom:feed must have at least one link element " "An atom:feed must have at least one link element "
~ "with a rel attribute of 'alternate'." ~ "with a rel attribute of 'alternate'."
] ]
] ]
s:rule [ s:rule [
context = "atom:feed" context = "atom:feed"
s:assert [ s:assert [
test = "atom:author or not(atom:entry[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."
skipping to change at page 41, line 4 skipping to change at page 42, line 5
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'] or atom:content" test = "atom:link[@rel='alternate'] "
~ "or atom:link[not(@rel)] "
~ "or atom:content"
"An atom:entry must have at least one link element " "An atom:entry must have at least one link element "
~ "with a rel attribute of 'alternate' or content." ~ "with a rel attribute of 'alternate' or content."
] ]
] ]
s:rule [ s:rule [
context = "atom:entry" context = "atom:entry"
s:assert [ s:assert [
test = "atom:author or " 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 "
skipping to change at page 42, line 19 skipping to change at page 43, line 22
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|anyElement)* (text|anyForeignElement)*
} }
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 45, line 16 skipping to change at page 46, line 19
pattern = "[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*" pattern = "[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*"
} }
# Unconstrained; it's not entirely clear how IRI fit into # Unconstrained; it's not entirely clear how IRI fit into
# xsd:anyURI so let's not try to constrain it here # xsd:anyURI so let's not try to constrain it here
atomUri = text atomUri = text
# Whatever an email address is, it contains at least one @ # Whatever an email address is, it contains at least one @
atomEmailAddress = xsd:string { pattern = ".+@.+" } atomEmailAddress = xsd:string { pattern = ".+@.+" }
# Extensibility # Simple Extension
simpleExtensionElement = simpleExtensionElement =
element * - atom:* { element * - atom:* {
text text
} }
# Structured Extension
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)*))
} }
# Other Extensibility
extensionElement = extensionElement =
simpleExtensionElement | structuredExtensionElement simpleExtensionElement | structuredExtensionElement
anyElement = anyElement =
element * {
(attribute * { text }
| text
| anyElement)*
}
anyForeignElement =
element * - atom:* { element * - atom:* {
(attribute * { text } (attribute * { text }
| text | text
| anyElement)* | anyElement)*
} }
# XHTML # XHTML
anyXHTML = element xhtml:* { anyXHTML = element xhtml:* {
(attribute * { text } (attribute * { text }
skipping to change at page 47, line 7 skipping to change at page 48, 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
[[anchor72: This section should be removed before final [[anchor71: This section should be removed before final
publication.]] publication.]]
-08: Remove BNF
complete rather than collected schema
Remove a couple introductory sentences
update MIME references
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"
 End of changes. 

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