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,