draft-ietf-atompub-format-11.txt   rfc4287.txt 
Network Working Group M. Nottingham, Ed. Network Working Group M. Nottingham, Ed.
Internet-Draft R. Sayre, Ed. Request for Comments: 4287 R. Sayre, Ed.
Expires: February 16, 2006 August 15, 2005 Category: Standards Track December 2005
The Atom Syndication Format The Atom Syndication Format
draft-ietf-atompub-format-11
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2005).
Abstract Abstract
This document specifies Atom, an XML-based Web content and metadata This document specifies Atom, an XML-based Web content and metadata
syndication format. syndication format.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................3
1.1 Examples . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Examples ...................................................3
1.2 Namespace and Version . . . . . . . . . . . . . . . . . . 5 1.2. Namespace and Version ......................................5
1.3 Notational Conventions . . . . . . . . . . . . . . . . . . 5 1.3. Notational Conventions .....................................5
2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 6 2. Atom Documents ..................................................6
3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 8 3. Common Atom Constructs ..........................................7
3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 8 3.1. Text Constructs ............................................7
3.1.1 The "type" Attribute . . . . . . . . . . . . . . . . . 8 3.1.1. The "type" Attribute ................................8
3.2 Person Constructs . . . . . . . . . . . . . . . . . . . . 11 3.2. Person Constructs .........................................10
3.2.1 The "atom:name" Element . . . . . . . . . . . . . . . 11 3.2.1. The "atom:name" Element ............................10
3.2.2 The "atom:uri" Element . . . . . . . . . . . . . . . . 11 3.2.2. The "atom:uri" Element .............................10
3.2.3 The "atom:email" Element . . . . . . . . . . . . . . . 11 3.2.3. The "atom:email" Element ...........................10
3.3 Date Constructs . . . . . . . . . . . . . . . . . . . . . 12 3.3. Date Constructs ...........................................10
4. Atom Element Definitions . . . . . . . . . . . . . . . . . . 13 4. Atom Element Definitions .......................................11
4.1 Container Elements . . . . . . . . . . . . . . . . . . . . 13 4.1. Container Elements ........................................11
4.1.1 The "atom:feed" Element . . . . . . . . . . . . . . . 13 4.1.1. The "atom:feed" Element ............................11
4.1.2 The "atom:entry" Element . . . . . . . . . . . . . . . 15 4.1.2. The "atom:entry" Element ...........................13
4.1.3 The "atom:content" Element . . . . . . . . . . . . . . 17 4.1.3. The "atom:content" Element .........................14
4.2 Metadata Elements . . . . . . . . . . . . . . . . . . . . 20 4.2. Metadata Elements .........................................17
4.2.1 The "atom:author" Element . . . . . . . . . . . . . . 20 4.2.1. The "atom:author" Element ..........................17
4.2.2 The "atom:category" Element . . . . . . . . . . . . . 20 4.2.2. The "atom:category" Element ........................18
4.2.3 The "atom:contributor" Element . . . . . . . . . . . . 21 4.2.3. The "atom:contributor" Element .....................18
4.2.4 The "atom:generator" Element . . . . . . . . . . . . . 21 4.2.4. The "atom:generator" Element .......................18
4.2.5 The "atom:icon" Element . . . . . . . . . . . . . . . 21 4.2.5. The "atom:icon" Element ............................19
4.2.6 The "atom:id" Element . . . . . . . . . . . . . . . . 22 4.2.6. The "atom:id" Element ..............................19
4.2.7 The "atom:link" Element . . . . . . . . . . . . . . . 24 4.2.7. The "atom:link" Element ............................21
4.2.8 The "atom:logo" Element . . . . . . . . . . . . . . . 26 4.2.8. The "atom:logo" Element ............................23
4.2.9 The "atom:published" Element . . . . . . . . . . . . . 26 4.2.9. The "atom:published" Element .......................23
4.2.10 The "atom:rights" Element . . . . . . . . . . . . . 26 4.2.10. The "atom:rights" Element .........................24
4.2.11 The "atom:source" Element . . . . . . . . . . . . . 27 4.2.11. The "atom:source" Element .........................24
4.2.12 The "atom:subtitle" Element . . . . . . . . . . . . 27 4.2.12. The "atom:subtitle" Element .......................25
4.2.13 The "atom:summary" Element . . . . . . . . . . . . . 28 4.2.13. The "atom:summary" Element ........................25
4.2.14 The "atom:title" Element . . . . . . . . . . . . . . 28 4.2.14. The "atom:title" Element ..........................25
4.2.15 The "atom:updated" Element . . . . . . . . . . . . . 28 4.2.15. The "atom:updated" Element ........................25
5. Securing Atom Documents . . . . . . . . . . . . . . . . . . 29 5. Securing Atom Documents ........................................26
6. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 32 5.1. Digital Signatures ........................................26
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 34 5.2. Encryption ................................................27
8. Security Considerations . . . . . . . . . . . . . . . . . . 36 5.3. Signing and Encrypting ....................................28
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 6. Extending Atom .................................................28
9.1 Normative References . . . . . . . . . . . . . . . . . . . 38 6.1. Extensions from Non-Atom Vocabularies .....................28
9.2 Informative References . . . . . . . . . . . . . . . . . . 39 6.2. Extensions to the Atom Vocabulary .........................28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 40 6.3. Processing Foreign Markup .................................28
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 41 6.4. Extension Elements ........................................29
B. RELAX NG Compact Schema . . . . . . . . . . . . . . . . . . 42 6.4.1. Simple Extension Elements ..........................29
C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 50 6.4.2. Structured Extension Elements ......................29
Intellectual Property and Copyright Statements . . . . . . . 56 7. IANA Considerations ............................................30
7.1. Registry of Link Relations ................................31
8. Security Considerations ........................................31
8.1. HTML and XHTML Content ....................................31
8.2. URIs ......................................................31
8.3. IRIs ......................................................31
8.4. Spoofing ..................................................31
8.5. Encryption and Signing ....................................32
9. References .....................................................32
9.1. Normative References ......................................32
9.2. Informative References ....................................34
Appendix A. Contributors ..........................................35
Appendix B. RELAX NG Compact Schema ...............................35
1. Introduction 1. Introduction
Atom is an XML-based document format that describes lists of related Atom is an XML-based document format that describes lists of related
information known as "feeds". Feeds are composed of a number of information known as "feeds". Feeds are composed of a number of
items, known as "entries", each with an extensible set of attached items, known as "entries", each with an extensible set of attached
metadata. For example, each entry has a title. metadata. For example, each entry has a title.
The primary use case that Atom addresses is the syndication of Web The primary use case that Atom addresses is the syndication of Web
content such as Weblogs and news headlines to Web sites as well as content such as weblogs and news headlines to Web sites as well as
directly to user agents. directly to user agents.
1.1 Examples 1.1. Examples
A brief, single-entry Atom Feed Document: A brief, single-entry Atom Feed Document:
<?xml version="1.0" encoding="utf-8"?> <?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom"> <feed xmlns="http://www.w3.org/2005/Atom">
<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>
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</contributor> </contributor>
<content type="xhtml" xml:lang="en" <content type="xhtml" xml:lang="en"
xml:base="http://diveintomark.org/"> xml:base="http://diveintomark.org/">
<div xmlns="http://www.w3.org/1999/xhtml"> <div xmlns="http://www.w3.org/1999/xhtml">
<p><i>[Update: The Atom draft is finished.]</i></p> <p><i>[Update: The Atom draft is finished.]</i></p>
</div> </div>
</content> </content>
</entry> </entry>
</feed> </feed>
1.2 Namespace and Version 1.2. Namespace and Version
The XML Namespaces URI [W3C.REC-xml-names-19990114] for the XML data The XML Namespaces URI [W3C.REC-xml-names-19990114] for the XML data
format described in this specification is: format described in this specification is:
http://www.w3.org/2005/Atom http://www.w3.org/2005/Atom
For convenience, this data format may be referred to as "Atom 1.0". For convenience, this data format may be referred to as "Atom 1.0".
This specification uses "Atom" internally. This specification uses "Atom" internally.
1.3 Notational Conventions 1.3. 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 the namespace prefix "atom:" for the This specification uses the namespace prefix "atom:" for the
Namespace URI identified in section 1.2. above. Note that the choice Namespace URI identified in Section 1.2, above. Note that the choice
of namespace prefix is arbitrary and not semantically significant. of namespace prefix is arbitrary and not semantically significant.
Atom is specified using terms from the XML Infoset [W3C.REC-xml- Atom is specified using terms from the XML Infoset
infoset-20040204]. However, this specification uses a shorthand for [W3C.REC-xml-infoset-20040204]. However, this specification uses a
two common terms; the phrase "Information Item" is omitted when shorthand for two common terms: the phrase "Information Item" is
naming Element Information Items and Attribute Information Items. omitted when naming Element Information Items and Attribute
Therefore, when this specification uses the term "element," it is Information Items. Therefore, when this specification uses the term
referring to an Element Information Item in Infoset terms. Likewise, "element," it is referring to an Element Information Item in Infoset
when it uses the term "attribute," it is referring to an Attribute terms. Likewise, when it uses the term "attribute," it is referring
Information Item. to an Attribute Information Item.
Some sections of this specification are illustrated with fragments of Some sections of this specification are illustrated with fragments of
a non-normative RELAX NG Compact schema [RELAX-NG]. However, the a non-normative RELAX NG Compact schema [RELAX-NG]. However, the
text of this specification provides the definition of conformance. A text of this specification provides the definition of conformance. A
complete schema appears in Appendix B. complete schema appears in Appendix B.
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 = "http://www.w3.org/2005/Atom" namespace atom = "http://www.w3.org/2005/Atom"
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, serialized as XML 1.0 [W3C.REC-xml-20040204] and
identified with the "application/atom+xml" media type. Atom identified with the "application/atom+xml" media type. Atom
Documents MUST be well-formed XML. This specification does not Documents MUST be well-formed XML. This specification does not
define a DTD for Atom Documents, and hence does not require them to define a DTD for Atom Documents, and hence does not require them to
be valid (in the sense used by XML). be valid (in the sense used by XML).
Atom allows the use of IRIs [RFC3987]. Every URI [RFC3986] is also Atom allows the use of IRIs [RFC3987]. Every URI [RFC3986] is also
an IRI, so a URI may be used wherever below an IRI is named. There an IRI, so a URI may be used wherever below an IRI is named. There
are two special considerations: when an IRI which is not also a URI are two special considerations: (1) when an IRI that is not also a
is given for dereferencing, it MUST be mapped to a URI using the URI is given for dereferencing, it MUST be mapped to a URI using the
steps in Section 3.1 of [RFC3987]; when an IRI is serving as an steps in Section 3.1 of [RFC3987] and (2) when an IRI is serving as
atom:id value, it MUST NOT be so mapped, so that the comparison works an atom:id value, it MUST NOT be so mapped, so that the comparison
as described in Section 4.2.6.1. works as described in Section 4.2.6.1.
Any element defined by this specification MAY have an xml:base Any element defined by this specification MAY have an xml:base
attribute [W3C.REC-xmlbase-20010627]. When xml:base is used in an attribute [W3C.REC-xmlbase-20010627]. When xml:base is used in an
Atom Document, it serves the function described in section 5.1.1 of Atom Document, it serves the function described in section 5.1.1 of
[RFC3986], establishing the base URI (or IRI) for resolving any [RFC3986], establishing the base URI (or IRI) for resolving any
relative references found within the effective scope of the xml:base relative references found within the effective scope of the xml:base
attribute. attribute.
Any element defined by this specification MAY have an xml:lang Any element defined by this specification MAY have an xml:lang
attribute, whose content indicates the natural language for the attribute, whose content indicates the natural language for the
element and its descendents. The language context is only element and its descendents. The language context is only
significant for elements and attributes declared to be "Language- significant for elements and attributes declared to be "Language-
Sensitive" by this specification. Requirements regarding the content Sensitive" by this specification. Requirements regarding the content
and interpretation of xml:lang are specified in XML 1.0 [W3C.REC-xml- and interpretation of xml:lang are specified in XML 1.0
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 }?,
undefinedAttribute* undefinedAttribute*
Atom is an extensible format. See Section 6 of this document for a Atom is an extensible format. See Section 6 of this document for a
full description of how Atom Documents can be extended. full description of how Atom Documents can be extended.
Atom Processors MAY keep state sourced from Atom Feed Documents and Atom Processors MAY keep state sourced from Atom Feed Documents and
skipping to change at page 8, line 16 skipping to change at page 7, line 31
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.
Note that there MUST NOT be any whitespace in a Date construct or in Note that there MUST NOT be any whitespace in a Date construct or in
any IRI. Some XML-emitting implementations erroneously insert any IRI. Some XML-emitting implementations erroneously insert white
whitespace around values by default, and such implementations will space around values by default, and such implementations will emit
emit invalid Atom Documents. invalid Atom Documents.
3.1 Text Constructs 3.1. Text Constructs
A Text construct contains human-readable text, usually in small A Text construct contains human-readable text, usually in small
quantities. The content of Text constructs is Language-Sensitive. quantities. The content of Text constructs is Language-Sensitive.
atomPlainTextConstruct = atomPlainTextConstruct =
atomCommonAttributes, atomCommonAttributes,
attribute type { "text" | "html" }?, attribute type { "text" | "html" }?,
text text
atomXHTMLTextConstruct = atomXHTMLTextConstruct =
atomCommonAttributes, atomCommonAttributes,
attribute type { "xhtml" }, attribute type { "xhtml" },
xhtmlDiv xhtmlDiv
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
not provided, Atom Processors MUST behave as though it were present is not provided, Atom Processors MUST behave as though it were
with a value of "text". Unlike the atom:content element defined in present with a value of "text". Unlike the atom:content element
Section 4.1.3, MIME media types [MIMEREG] MUST NOT be used as values defined in Section 4.1.3, MIME media types [MIMEREG] MUST NOT be used
for the "type" attribute on Text constructs. as values for the "type" attribute on Text constructs.
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 collapse humans in a readable fashion. Thus, Atom Processors MAY collapse
white-space (including line-breaks), and display the text using white space (including line breaks) and display the text using
typographic techniques such as justification and proportional fonts. 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 [HTML]. Any markup within MUST be escaped; for example, as HTML [HTML]. Any markup within MUST be escaped; for example,
"<br>" as "&lt;br>". HTML markup within SHOULD be such that it could "<br>" as "&lt;br>". HTML markup within SHOULD be such that it could
validly appear directly within an HTML <DIV> element, after validly appear directly within an HTML <DIV> element, after
unescaping. Atom Processors that display such content MAY use that unescaping. Atom Processors that display such content 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 [XHTML], and SHOULD be suitable MUST be a single XHTML div element [XHTML] and SHOULD be suitable for
for handling as XHTML. The XHTML div element itself MUST NOT be handling as XHTML. The XHTML div element itself MUST NOT be
considered part of the content. Atom Processors that display the considered part of the content. Atom Processors that display the
content MAY use the markup to aid in displaying it. The escaped content MAY use the markup to aid in displaying it. The escaped
versions of characters such as "&" and ">" represent those versions of characters such as "&" and ">" represent those
characters, not markup. characters, not 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">
skipping to change at page 11, line 5 skipping to change at page 10, line 5
to the "xh" prefix earlier in the document: to the "xh" prefix earlier in the document:
... ...
<summary type="xhtml"> <summary type="xhtml">
<xh:div> <xh:div>
This is <xh:b>XHTML</xh:b> content. This is <xh:b>XHTML</xh:b> content.
</xh:div> </xh:div>
</summary> </summary>
... ...
3.2 Person Constructs 3.2. Person Constructs
A Person construct is an element that describes a person, A Person construct is an element that describes a person,
corporation, or similar entity (hereafter, 'person'). corporation, or similar entity (hereafter, 'person').
atomPersonConstruct = atomPersonConstruct =
atomCommonAttributes, atomCommonAttributes,
(element atom:name { text } (element atom:name { text }
& element atom:uri { atomUri }? & element atom:uri { atomUri }?
& element atom:email { atomEmailAddress }? & element atom:email { atomEmailAddress }?
& extensionElement*) & extensionElement*)
This specification assigns no significance to the order of appearance This specification assigns no significance to the order of appearance
of the child elements in a Person construct. Person constructs allow of the child elements in a Person construct. Person constructs allow
extension Metadata elements (see Section 6.4). extension Metadata elements (see Section 6.4).
3.2.1 The "atom:name" Element 3.2.1. The "atom:name" Element
The "atom:name" element's content conveys a human-readable name for The "atom:name" element's content conveys a human-readable name for
the person. The content of atom:name is Language-Sensitive. Person the person. The content of atom:name is Language-Sensitive. Person
constructs MUST contain exactly one "atom:name" element. constructs MUST contain exactly one "atom:name" element.
3.2.2 The "atom:uri" Element 3.2.2. The "atom:uri" Element
The "atom:uri" element's content conveys an IRI associated with the The "atom:uri" element's content conveys an IRI associated with the
person. Person constructs MAY contain an atom:uri element, but MUST person. Person constructs MAY contain an atom:uri element, but MUST
NOT contain more than one. The content of atom:uri in a Person NOT contain more than one. The content of atom:uri in a Person
construct MUST be an IRI reference [RFC3987]. construct MUST be an IRI reference [RFC3987].
3.2.3 The "atom:email" Element 3.2.3. The "atom:email" Element
The "atom:email" element's content conveys an e-mail address The "atom:email" element's content conveys an e-mail address
associated with the person. Person constructs MAY contain an atom: associated with the person. Person constructs MAY contain an
email element, but MUST NOT contain more than one. Its content MUST atom:email element, but MUST NOT contain more than one. Its content
conform to the "addr-spec" production 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
"date-time" production in [RFC3339]. In addition, an uppercase "T" "date-time" production in [RFC3339]. In addition, an uppercase "T"
character MUST be used to separate date and time, and an uppercase character MUST be used to separate date and time, and an uppercase
"Z" character MUST be present in the absence of a numeric time zone "Z" character MUST be present in the absence of a numeric time zone
offset. offset.
atomDateConstruct = atomDateConstruct =
atomCommonAttributes, atomCommonAttributes,
xsd:dateTime xsd:dateTime
skipping to change at page 12, line 30 skipping to change at page 11, line 17
Example Date constructs: Example Date constructs:
<updated>2003-12-13T18:30:02Z</updated> <updated>2003-12-13T18:30:02Z</updated>
<updated>2003-12-13T18:30:02.25Z</updated> <updated>2003-12-13T18:30:02.25Z</updated>
<updated>2003-12-13T18:30:02+01:00</updated> <updated>2003-12-13T18:30:02+01:00</updated>
<updated>2003-12-13T18:30:02.25+01:00</updated> <updated>2003-12-13T18:30:02.25+01:00</updated>
Date values SHOULD be as accurate as possible. For example, it would Date values SHOULD be as accurate as possible. For example, it would
be generally inappropriate for a publishing system to apply the same be generally inappropriate for a publishing system to apply the same
timestamp to several entries which were published during the course timestamp to several entries that were published during the course of
of a single day. a single day.
4. Atom Element Definitions 4. Atom Element Definitions
4.1 Container Elements 4.1. Container Elements
4.1.1 The "atom:feed" Element 4.1.1. The "atom:feed" Element
The "atom:feed" element is the document (i.e., top-level) element of The "atom:feed" element is the document (i.e., top-level) element of
an Atom Feed Document, acting as a container for metadata and data an Atom Feed Document, acting as a container for metadata and data
associated with the feed. Its element children consist of metadata associated with the feed. Its element children consist of metadata
elements followed by zero or more atom:entry child elements. elements followed by zero or more atom:entry child elements.
atomFeed = atomFeed =
element atom:feed { element atom:feed {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor* (atomAuthor*
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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 one or more atom:author elements, o atom:feed elements MUST contain one or more atom:author elements,
unless all of the atom:feed element's child atom:entry elements unless all of the atom:feed element's child atom:entry elements
contain at least one atom:author element. contain at least 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: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:logo o atom:feed elements MUST NOT contain more than one atom:logo
element. element.
o atom:feed elements MUST contain exactly one atom:id element. o atom:feed elements MUST contain exactly one atom:id element.
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 is the preferred URI for attribute value of "self". This is the preferred URI for
retrieving Atom Feed Documents representing this Atom feed. retrieving Atom Feed Documents representing this Atom feed.
o atom:feed elements MUST NOT contain more than one atom:link o atom:feed elements MUST NOT contain more than one atom:link
element with a rel attribute value of "alternate" that has the element with a rel attribute value of "alternate" that has the
same combination of type and hreflang attribute values. same combination of type and hreflang attribute values.
o atom:feed elements MAY contain additional atom:link elements o atom:feed elements MAY contain additional atom:link elements
beyond those described above. beyond those described above.
o atom:feed elements MUST NOT contain more than one atom:rights o atom:feed elements MUST NOT contain more than one atom:rights
element. element.
o atom:feed elements MUST NOT contain more than one atom:subtitle o atom:feed elements MUST NOT contain more than one atom:subtitle
element. element.
o atom:feed elements MUST contain exactly one atom:title element. o atom:feed elements MUST contain exactly one atom:title element.
o atom:feed elements MUST contain exactly one atom:updated element. o atom:feed elements MUST contain exactly one atom:updated element.
If multiple atom:entry elements with the same atom:id value appear in If multiple atom:entry elements with the same atom:id value appear in
an Atom Feed Document, they represent the same entry. Their atom: an Atom Feed Document, they represent the same entry. Their
updated timestamps SHOULD be different. If an Atom Feed Document atom:updated timestamps SHOULD be different. If an Atom Feed
contains multiple entries with the same atom:id, Atom Processors MAY Document contains multiple entries with the same atom:id, Atom
choose to display all of them or some subset of them. One typical Processors MAY choose to display all of them or some subset of them.
behavior would be to display only the entry with the latest atom: One typical behavior would be to display only the entry with the
updated timestamp. latest atom:updated timestamp.
4.1.1.1 Providing Textual Content 4.1.1.1. Providing Textual Content
Experience teaches that feeds which contain textual content are in Experience teaches that feeds that contain textual content are in
general more useful than those which do not. Some applications (one general more useful than those that do not. Some applications (one
example is full-text indexers) require a minimum amount of text or example is full-text indexers) require a minimum amount of text or
(X)HTML to function reliably and predictably. Feed producers should (X)HTML to function reliably and predictably. Feed producers should
be aware of these issues. It is advisable that each atom:entry be aware of these issues. It is advisable that each atom:entry
element contain a non-empty atom:title element, a non-empty atom: element contain a non-empty atom:title element, a non-empty
content element when that element is present, and a non-empty atom: atom:content element when that element is present, and a non-empty
summary element when the entry contains no atom:content element. atom:summary element when the entry contains no atom:content element.
However, the absence of atom:summary is not an error and Atom However, the absence of atom:summary is not an error, and Atom
Processors MUST NOT fail to function correctly as a consequence of Processors MUST NOT fail to function correctly as a consequence of
such an absence. such an absence.
4.1.2 The "atom:entry" Element 4.1.2. The "atom:entry" Element
The "atom:entry" element represents an individual entry, acting as a The "atom:entry" element represents an individual entry, acting as a
container for metadata and data associated with the entry. This container for metadata and data associated with the entry. This
element can appear as a child of the atom:feed element, or it can element can appear as a child of the atom:feed element, or it can
appear as the document (i.e., top-level) element of a standalone Atom appear as the document (i.e., top-level) element of a stand-alone
Entry Document. Atom Entry Document.
atomEntry = atomEntry =
element atom:entry { element atom:entry {
atomCommonAttributes, atomCommonAttributes,
(atomAuthor* (atomAuthor*
& atomCategory* & atomCategory*
& atomContent? & atomContent?
& atomContributor* & atomContributor*
& atomId & atomId
& atomLink* & atomLink*
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& extensionElement*) & extensionElement*)
} }
This specification assigns no significance to the order of appearance This specification assigns no significance to the order of appearance
of the child elements of atom:entry. of the child elements of atom:entry.
The following child elements are defined by this specification (note The following child elements are defined by this specification (note
that it requires the presence of some of these elements): that it requires the presence of some of these elements):
o atom:entry elements MUST contain one or more atom:author elements, o atom:entry elements MUST contain one or more atom:author elements,
unless the atom:entry contains an atom:source element which unless the atom:entry contains an atom:source element that
contains an atom:author element, or, in an Atom Feed Document, the contains an atom:author element or, in an Atom Feed Document, the
atom:feed element contains an atom:author element itself. atom:feed element contains an atom:author element itself.
o atom:entry elements 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 contain exactly one atom:id element. o atom:entry elements MUST contain exactly one atom:id element.
o atom:entry elements that contain no child atom:content element o atom:entry elements that contain no child atom:content element
MUST contain at least one atom:link element with a rel attribute MUST contain at least one atom:link element with a rel attribute
value of "alternate". value of "alternate".
o atom:entry elements MUST NOT contain more than one atom:link o atom:entry elements MUST NOT contain more than one atom:link
element with a rel attribute value of "alternate" that has the element with a rel attribute value of "alternate" that has the
same combination of type and hreflang attribute values. same combination of type and hreflang attribute values.
o atom:entry elements MAY contain additional atom:link elements o atom:entry elements MAY contain additional atom:link elements
beyond those described above. beyond those described above.
o atom:entry elements MUST NOT contain more than one atom:published o atom:entry elements MUST NOT contain more than one atom:published
element. element.
o atom:entry elements MUST NOT contain more than one atom:rights o atom:entry elements MUST NOT contain more than one atom:rights
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 either o atom:entry elements MUST contain an atom:summary element in either
of the following cases: of the following cases:
* the atom:entry contains an atom:content that has a "src" * the atom:entry contains an atom:content that has a "src"
attribute (and is thus empty). attribute (and is thus empty).
* the atom:entry contains content that is encoded in Base64;
* the atom:entry contains content that is encoded in Base64; i.e. i.e., the "type" attribute of atom:content is a MIME media type
the "type" attribute of atom:content is a MIME media type
[MIMEREG], but is not an XML media type [RFC3023], does not [MIMEREG], but is not an XML media type [RFC3023], does not
begin with "text/", and does not end with "/xml" or "+xml". begin with "text/", and does not end with "/xml" or "+xml".
o atom:entry elements MUST NOT contain more than one atom:summary o atom:entry elements MUST NOT contain more than one atom:summary
element. element.
o atom:entry elements MUST contain exactly one atom:title element. o atom:entry elements MUST contain exactly one atom:title element.
o atom:entry elements MUST contain exactly one atom:updated element. o atom:entry elements MUST contain exactly one atom:updated element.
4.1.3 The "atom:content" Element 4.1.3. The "atom:content" Element
The "atom:content" element either contains or links to the content of The "atom:content" element either contains or links to the content of
the entry. The content of atom:content is Language-Sensitive. the entry. The content of atom:content is Language-Sensitive.
atomInlineTextContent = atomInlineTextContent =
element atom:content { element atom:content {
atomCommonAttributes, atomCommonAttributes,
attribute type { "text" | "html" }?, attribute type { "text" | "html" }?,
(text)* (text)*
} }
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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
On the atom:content element, the value of the "type" attribute MAY be On the atom:content element, the value of the "type" attribute MAY be
one of "text", "html", or "xhtml". Failing that, it MUST conform to one of "text", "html", or "xhtml". Failing that, it MUST conform to
the syntax of a MIME media type, but MUST NOT be a composite type the syntax of a MIME media type, but MUST NOT be a composite type
(see Section 4.2.6 of [MIMEREG]). If neither the type attribute nor (see Section 4.2.6 of [MIMEREG]). If neither the type attribute nor
the src attribute is provided, Atom Processors MUST behave as though the src attribute is provided, Atom Processors MUST behave as though
the type attribute were present with a value of "text". the type attribute were present with a value of "text".
4.1.3.2 The "src" attribute 4.1.3.2. The "src" Attribute
atom:content MAY have a "src" attribute, whose value MUST be an IRI atom:content MAY have a "src" attribute, whose value MUST be an IRI
reference [RFC3987]. If the "src" attribute is present, atom:content reference [RFC3987]. If the "src" attribute is present, atom:content
MUST be empty. Atom Processors MAY use the IRI to retrieve the MUST be empty. Atom Processors MAY use the IRI to retrieve the
content, and MAY chose to ignore remote content or present it in a content and MAY choose to ignore remote content or to present it in a
different manner than local content. different manner than local content.
If the "src" attribute is present, the "type" attribute SHOULD be If the "src" attribute is present, the "type" attribute SHOULD be
provided and MUST be a MIME media type [MIMEREG], rather than "text", provided and MUST be a MIME media type [MIMEREG], rather than "text",
"html", or "xhtml". The value is advisory; that is to say, when the "html", or "xhtml". The value is advisory; that is to say, when the
corresponding URI (mapped from an IRI, if necessary), is corresponding URI (mapped from an IRI, if necessary) is dereferenced,
dereferenced, if the server providing that content also provides a if the server providing that content also provides a media type, the
media type, the server-provided media type is authoritative. server-provided media type is authoritative.
4.1.3.3 Processing Model 4.1.3.3. Processing Model
Atom Documents MUST conform to the following rules. Atom Processors Atom Documents MUST conform to the following rules. Atom Processors
MUST interpret atom:content according to the first applicable rule. MUST interpret atom:content according to the first applicable rule.
1. If the value of "type" is "text", the content of atom:content 1. If the value of "type" is "text", the content of atom:content
MUST NOT contain child elements. Such text is intended to be MUST NOT contain child elements. Such text is intended to be
presented to humans in a readable fashion. Thus, Atom Processors presented to humans in a readable fashion. Thus, Atom Processors
MAY collapse white-space (including line-breaks), and display the MAY collapse white space (including line breaks), and display the
text using typographic techniques such as justification and text using typographic techniques such as justification and
proportional fonts. proportional fonts.
2. If the value of "type" is "html", the content of atom:content 2. If the value of "type" is "html", the content of atom:content
MUST NOT contain child elements, and SHOULD be suitable for MUST NOT contain child elements and SHOULD be suitable for
handling as HTML [HTML]. The HTML markup MUST be escaped; for handling as HTML [HTML]. The HTML markup MUST be escaped; for
example, "<br>" as "&lt;br>". The HTML markup SHOULD be such example, "<br>" as "&lt;br>". The HTML markup SHOULD be such
that it could validly appear directly within an HTML <DIV> that it could validly appear directly within an HTML <DIV>
element. Atom Processors that display the content MAY use the element. Atom Processors that display the content MAY use the
markup to aid in displaying it. markup to aid in displaying it.
3. If the value of "type" is "xhtml", the content of atom:content 3. If the value of "type" is "xhtml", the content of atom:content
MUST be a single XHTML div element [XHTML], and SHOULD be MUST be a single XHTML div element [XHTML] and SHOULD be suitable
suitable for handling as XHTML. The XHTML div element itself for handling as XHTML. The XHTML div element itself MUST NOT be
MUST NOT be considered part of the content. Atom Processors that considered part of the content. Atom Processors that display the
display the content MAY use the markup to aid in displaying it. content MAY use the markup to aid in displaying it. The escaped
The escaped versions of characters such as "&" and ">" represent versions of characters such as "&" and ">" represent those
those characters, not markup. characters, not markup.
4. If the value of "type" is an XML media type [RFC3023], or ends 4. If the value of "type" is an XML media type [RFC3023] or ends
with "+xml" or "/xml" (case-insensitive), the content of with "+xml" or "/xml" (case insensitive), the content of
atom:content MAY include child elements, and SHOULD be suitable atom:content MAY include child elements and SHOULD be suitable
for handling as the indicated media type. If the "src" attribute for handling as the indicated media type. If the "src" attribute
is not provided, this would normally mean that the "atom:content" is not provided, this would normally mean that the "atom:content"
element would contain a single child element which would serve as element would contain a single child element that would serve as
the root element of the XML document of the indicated type. the root element of the XML document of the indicated type.
5. If the value of "type" begins with "text/" (case-insensitive), 5. If the value of "type" begins with "text/" (case insensitive),
the content of atom:content MUST NOT contain child elements. the content of atom:content MUST NOT contain child elements.
6. For all other values of "type", the content of atom:content MUST 6. For all other values of "type", the content of atom:content MUST
be a valid Base64 encoding, as described in [RFC3548], section 3. be a valid Base64 encoding, as described in [RFC3548], section 3.
When decoded, it SHOULD be suitable for handling as the indicated When decoded, it SHOULD be suitable for handling as the indicated
media type. In this case, the characters in the Base64 encoding media type. In this case, the characters in the Base64 encoding
MAY be preceded and followed in the atom:content element by MAY be preceded and followed in the atom:content element by white
white-space, and lines are separated by a single newline (U+000A) space, and lines are separated by a single newline (U+000A)
character. 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>
</content> </content>
... ...
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to the "xh" prefix earlier in the document: to the "xh" prefix earlier in the document:
... ...
<content type="xhtml"> <content type="xhtml">
<xh:div> <xh:div>
This is <xh:b>XHTML</xh:b> content. This is <xh:b>XHTML</xh:b> content.
</xh:div> </xh:div>
</content> </content>
... ...
4.2 Metadata Elements 4.2. Metadata Elements
4.2.1 The "atom:author" Element 4.2.1. The "atom:author" Element
The "atom:author" element is a Person construct that indicates the The "atom:author" element is a Person construct that indicates the
author of the entry or feed. author of the entry or feed.
atomAuthor = element atom:author { atomPersonConstruct } atomAuthor = element atom:author { atomPersonConstruct }
If an atom:entry element does not contain atom:author elements, then If an atom:entry element does not contain atom:author elements, then
the atom:author elements of the contained atom:source element are the atom:author elements of the contained atom:source element are
considered to apply. In an Atom Feed Document, the atom:author considered to apply. In an Atom Feed Document, the atom:author
elements of the containing atom:feed element are considered to apply elements of the containing atom:feed element are considered to apply
to the entry if there are no atom:author elements in the locations to the entry if there are no atom:author elements in the locations
described above. described above.
4.2.2 The "atom:category" Element 4.2.2. The "atom:category" Element
The "atom:category" element conveys information about a category The "atom:category" element conveys information about a category
associated with an entry or feed. This specification assigns no associated with an entry or feed. This specification assigns no
meaning to the content (if any) of this element. meaning to the content (if any) of this element.
atomCategory = atomCategory =
element atom:category { element atom:category {
atomCommonAttributes, atomCommonAttributes,
attribute term { text }, attribute term { text },
attribute scheme { atomUri }?, attribute scheme { atomUri }?,
attribute label { text }?, attribute label { text }?,
undefinedContent undefinedContent
} }
4.2.2.1 The "term" Attribute 4.2.2.1. The "term" Attribute
The "term" attribute is a string that identifies the category to The "term" attribute is a string that identifies the category to
which the entry or feed belongs. Category elements MUST have a which the entry or feed belongs. Category elements MUST have a
"term" attribute. "term" attribute.
4.2.2.2 The "scheme" Attribute 4.2.2.2. The "scheme" Attribute
The "scheme" attribute is an IRI that identifies a categorization The "scheme" attribute is an IRI that identifies a categorization
scheme. Category elements MAY have a "scheme" attribute. scheme. Category elements MAY have a "scheme" attribute.
4.2.2.3 The "label" attribute 4.2.2.3. The "label" Attribute
The "label" attribute provides a human-readable label for display in The "label" attribute provides a human-readable label for display in
end-user applications. The content of the "label" attribute is end-user applications. The content of the "label" attribute is
Language-Sensitive. Entities such as "&amp;" and "&lt;" represent Language-Sensitive. Entities such as "&amp;" and "&lt;" represent
their corresponding characters ("&" and "<" respectively), not their corresponding characters ("&" and "<", respectively), not
markup. Category elements MAY have a "label" attribute. markup. Category elements MAY have a "label" attribute.
4.2.3 The "atom:contributor" Element 4.2.3. The "atom:contributor" Element
The "atom:contributor" element is a Person construct that indicates a The "atom:contributor" element is a Person construct that indicates a
person or other entity who contributed to the entry or feed. person or other entity who contributed to the entry or feed.
atomContributor = element atom:contributor { atomPersonConstruct } atomContributor = element atom:contributor { atomPersonConstruct }
4.2.4 The "atom:generator" Element 4.2.4. The "atom:generator" Element
The "atom:generator" element's content identifies the agent used to The "atom:generator" element's content identifies the agent used to
generate a feed, for debugging and other purposes. generate a feed, for debugging and other purposes.
atomGenerator = element atom:generator { atomGenerator = element atom:generator {
atomCommonAttributes, atomCommonAttributes,
attribute uri { atomUri }?, attribute uri { atomUri }?,
attribute version { text }?, attribute version { text }?,
text text
} }
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"<" respectively), not markup. "<" respectively), not markup.
The atom:generator element MAY have a "uri" attribute whose value The atom:generator element MAY have a "uri" attribute whose value
MUST be an IRI reference [RFC3987]. When dereferenced, the resulting MUST be an IRI reference [RFC3987]. When dereferenced, the resulting
URI (mapped from an IRI, if necessary) SHOULD produce a URI (mapped from an IRI, if necessary) SHOULD produce a
representation that is relevant to that agent. representation that is relevant to that agent.
The atom:generator element MAY have a "version" attribute that The atom:generator element MAY have a "version" attribute that
indicates the version of the generating agent. indicates the version of the generating agent.
4.2.5 The "atom:icon" Element 4.2.5. The "atom:icon" Element
The "atom:icon" element's content is an IRI reference [RFC3987] which The "atom:icon" element's content is an IRI reference [RFC3987] that
identifies an image which provides iconic visual identification for a identifies an image that provides iconic visual identification for a
feed. feed.
atomIcon = element atom:icon { atomIcon = element atom:icon {
atomCommonAttributes, atomCommonAttributes,
(atomUri) (atomUri)
} }
The image SHOULD have an aspect ratio of one (horizontal) to one The image SHOULD have an aspect ratio of one (horizontal) to one
(vertical), and SHOULD be suitable for presentation at a small size. (vertical) and SHOULD be suitable for presentation at a small size.
4.2.6 The "atom:id" Element 4.2.6. The "atom:id" Element
The "atom:id" element conveys a permanent, universally unique The "atom:id" element conveys a permanent, universally unique
identifier for an entry or feed. identifier for an entry or feed.
atomId = element atom:id { atomId = element atom:id {
atomCommonAttributes, atomCommonAttributes,
(atomUri) (atomUri)
} }
Its content MUST be an IRI, as defined by [RFC3987]. Note that the Its content MUST be an IRI, as defined by [RFC3987]. Note that the
definition of "IRI" excludes relative references. Though the IRI definition of "IRI" excludes relative references. Though the IRI
might use a dereferencable scheme, Atom Processors MUST NOT assume it might use a dereferencable scheme, Atom Processors MUST NOT assume it
can be dereferenced. can be dereferenced.
When an Atom Document is relocated, migrated, syndicated, When an Atom Document is relocated, migrated, syndicated,
republished, exported or imported, the content of its atom:id element republished, exported, or imported, the content of its atom:id
MUST NOT change. Put another way, an atom:id element pertains to all element MUST NOT change. Put another way, an atom:id element
instantiations of a particular Atom entry or feed; revisions retain pertains to all instantiations of a particular Atom entry or feed;
the same content in their atom:id elements. It is suggested that the revisions retain the same content in their atom:id elements. It is
atom:id element be stored along with the associated resource. suggested that the atom:id element be stored along with the
associated resource.
The content of an atom:id element MUST be created in a way that The content of an atom:id element MUST be created in a way that
assures uniqueness. 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 mapped to URIs and dereferenced, the following equivalent if they were mapped to URIs and dereferenced, the
normalization strategy SHOULD be applied when generating atom:id following normalization strategy SHOULD be applied when generating
elements: 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 from appearing in paths.
o Prevent dot-segments appearing in paths.
o For schemes that define a default authority, use an empty o For schemes that define a default authority, use an empty
authority if the default is desired. authority if the default is desired.
o For schemes that define an empty path to be equivalent to a path o For schemes that define an empty path to be equivalent to a path
of "/", use "/". of "/", use "/".
o For schemes that define a port, use an empty port if the default o For schemes that define a port, use an empty port if the default
is desired. is desired.
o Preserve empty fragment identifiers and queries. o Preserve empty fragment identifiers and queries.
o Ensure that all components of the IRI are appropriately character
normalized, e.g., by using NFC or NFKC.
o Ensure that all components of the IRI are appropriately character- 4.2.6.1. Comparing atom:id
normalized, e.g. by using NFC or NFKC.
4.2.6.1 Comparing atom:id
Instances of atom:id elements can be compared to determine whether an Instances of atom:id elements can be compared to determine whether an
entry or feed is the same as one seen before. Processors MUST entry or feed is the same as one seen before. Processors MUST
compare atom:id elements on a character-by-character basis (in a compare atom:id elements on a character-by-character basis (in a
case-sensitive fashion). Comparison operations MUST be based solely case-sensitive fashion). Comparison operations MUST be based solely
on the IRI character strings, and MUST NOT rely on dereferencing the on the IRI character strings and MUST NOT rely on dereferencing the
IRIs or URIs mapped from them. IRIs or URIs mapped from them.
As a result, two IRIs that resolve to the same resource but are not As a result, two IRIs that resolve to the same resource but are not
character-for-character identical will be considered different for character-for-character identical will be considered different for
the purposes of identifier comparison. the purposes of identifier comparison.
For example, these are four distinct identifiers, despite the fact For example, these are four distinct identifiers, despite the fact
that they differ only in case: that they differ only in case:
http://www.example.org/thing http://www.example.org/thing
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IRIs or URIs mapped from them. IRIs or URIs mapped from them.
As a result, two IRIs that resolve to the same resource but are not As a result, two IRIs that resolve to the same resource but are not
character-for-character identical will be considered different for character-for-character identical will be considered different for
the purposes of identifier comparison. the purposes of identifier comparison.
For example, these are four distinct identifiers, despite the fact For example, these are four distinct identifiers, despite the fact
that they differ only in case: that they differ only in case:
http://www.example.org/thing http://www.example.org/thing
http://www.example.org/Thing http://www.example.org/Thing
http://www.EXAMPLE.org/thing http://www.EXAMPLE.org/thing
HTTP://www.example.org/thing HTTP://www.example.org/thing
Likewise, these are three distinct identifiers, because IRI Likewise, these are three distinct identifiers, because IRI
%-escaping is significant for the purposes of comparison: %-escaping is significant for the purposes of comparison:
http://www.example.com/~bob http://www.example.com/~bob
http://www.example.com/%7ebob http://www.example.com/%7ebob
http://www.example.com/%7Ebob http://www.example.com/%7Ebob
4.2.7 The "atom:link" Element 4.2.7. The "atom:link" Element
The "atom:link" element defines a reference from an entry or feed to The "atom:link" element defines a reference from an entry or feed to
a Web resource. This specification assigns no meaning to the content a Web resource. This specification assigns no meaning to the content
(if any) of this element. (if any) of this element.
atomLink = atomLink =
element atom:link { element atom:link {
atomCommonAttributes, atomCommonAttributes,
attribute href { atomUri }, attribute href { atomUri },
attribute rel { atomNCName | atomUri }?, attribute rel { atomNCName | atomUri }?,
attribute type { atomMediaType }?, attribute type { atomMediaType }?,
attribute hreflang { atomLanguageTag }?, attribute hreflang { atomLanguageTag }?,
attribute title { text }?, attribute title { text }?,
attribute length { text }?, attribute length { text }?,
undefinedContent undefinedContent
} }
4.2.7.1 The "href" Attribute 4.2.7.1. The "href" Attribute
The "href" attribute contains the link's IRI. atom:link elements MUST The "href" attribute contains the link's IRI. atom:link elements MUST
have a href attribute, whose value MUST be a IRI reference [RFC3987]. have an href attribute, whose value MUST be a IRI reference
[RFC3987].
4.2.7.2 The "rel" Attribute 4.2.7.2. The "rel" Attribute
atom:link elements MAY have a "rel" attribute that indicates the link atom:link elements MAY have a "rel" attribute that indicates the link
relation type. If the "rel" attribute is not present, the link relation type. If the "rel" attribute is not present, the link
element MUST be interpreted as if the link relation type is element MUST be interpreted as if the link relation type is
"alternate". "alternate".
The value of "rel" MUST be a string that is non-empty, and matches The value of "rel" MUST be a string that is non-empty and matches
either the "isegment-nz-nc" or the "IRI" production in [RFC3987]. either the "isegment-nz-nc" or the "IRI" production in [RFC3987].
Note that use of a relative reference other than a simple name is not Note that use of a relative reference other than a simple name is not
allowed. If a name is given, implementations MUST consider the link allowed. If a name is given, implementations MUST consider the link
relation type to be equivalent to the same name registered within the relation type equivalent to the same name registered within the IANA
IANA Registry of Link Relations (Section 7), and thus the IRI that Registry of Link Relations (Section 7), and thus to the IRI that
would be obtained by appending the value of the rel attribute to the would be obtained by appending the value of the rel attribute to the
string "http://www.iana.org/assignments/relation/". The value of string "http://www.iana.org/assignments/relation/". The value of
"rel" describes the meaning of the link, but does not impose any "rel" describes the meaning of the link, but does not impose any
behavioral requirements on Atom Processors. behavioral requirements on Atom Processors.
This document defines five initial values for the Registry of Link This document defines five initial values for the Registry of Link
Relations: Relations:
1. The value "alternate" signifies that the IRI in the value of the 1. The value "alternate" signifies that the IRI in the value of the
href attribute identifies an alternate version of the resource href attribute identifies an alternate version of the resource
skipping to change at page 25, line 22 skipping to change at page 22, line 34
<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 that is potentially
large in size and might require special handling. For atom:link large in size and might require special handling. For atom:link
elements with rel="enclosure", the length attribute SHOULD be elements with rel="enclosure", the length attribute SHOULD be
provided. provided.
5. The value "via" signifies that the IRI in the value of the href 5. The value "via" signifies that the IRI in the value of the href
attribute identifies a resource that is the source of the attribute identifies a resource that is the source of the
information provided in the containing element. information provided in the containing element.
4.2.7.3 The "type" Attribute 4.2.7.3. The "type" Attribute
On the link element, the "type" attribute's value is an advisory On the link element, the "type" attribute's value is an advisory
media type; it is a hint about the type of the representation that is media type: it is a hint about the type of the representation that is
expected to be returned when the value of the href attribute is expected to be returned when the value of the href attribute is
dereferenced. Note that the type attribute does not override the dereferenced. Note that the type attribute does not override the
actual media type returned with the representation. Link elements actual media type returned with the representation. Link elements
MAY have a type attribute, whose value MUST conform to the syntax of MAY have a type attribute, whose value MUST conform to the syntax of
a MIME media type [MIMEREG]. a MIME media type [MIMEREG].
4.2.7.4 The "hreflang" Attribute 4.2.7.4. The "hreflang" Attribute
The "hreflang" attribute's content describes the language of the The "hreflang" attribute's content describes the language of the
resource pointed to by the href attribute. When used together with resource pointed to by the href attribute. When used together with
the rel="alternate", it implies a translated version of the entry. the rel="alternate", it implies a translated version of the entry.
Link elements MAY have an hreflang attribute, whose value MUST be a Link elements MAY have an hreflang attribute, whose value MUST be a
language tag [RFC3066]. language tag [RFC3066].
4.2.7.5 The "title" Attribute 4.2.7.5. The "title" Attribute
The "title" attribute conveys human-readable information about the The "title" attribute conveys human-readable information about the
link. The content of the "title" attribute is Language-Sensitive. link. The content of the "title" attribute is Language-Sensitive.
Entities such as "&amp;" and "&lt;" represent their corresponding Entities such as "&amp;" and "&lt;" represent their corresponding
characters ("&" and "<" respectively), not markup. Link elements MAY characters ("&" and "<", respectively), not markup. Link elements
have a title attribute. MAY have a title attribute.
4.2.7.6 The "length" Attribute 4.2.7.6. The "length" Attribute
The "length" attribute indicates an advisory length of the linked The "length" attribute indicates an advisory length of the linked
content in octets; it is a hint about the content length of the content in octets; it is a hint about the content length of the
representation returned when the IRI in the href attribute is mapped representation returned when the IRI in the href attribute is mapped
to a URI and dereferenced. Note that the length attribute does not to a URI and dereferenced. Note that the length attribute does not
override the actual content length of the representation as reported override the actual content length of the representation as reported
by the underlying protocol. Link elements MAY have a length by the underlying protocol. Link elements MAY have a length
attribute. attribute.
4.2.8 The "atom:logo" Element 4.2.8. The "atom:logo" Element
The "atom:logo" element's content is an IRI reference [RFC3987] which The "atom:logo" element's content is an IRI reference [RFC3987] that
identifies an image which provides visual identification for a feed. identifies an image that provides visual identification for a feed.
atomLogo = element atom:logo { atomLogo = element atom:logo {
atomCommonAttributes, atomCommonAttributes,
(atomUri) (atomUri)
} }
The image SHOULD have an aspect ratio of 2 (horizontal) to 1 The image SHOULD have an aspect ratio of 2 (horizontal) to 1
(vertical). (vertical).
4.2.9 The "atom:published" Element 4.2.9. The "atom:published" Element
The "atom:published" element is a Date construct indicating an The "atom:published" element is a Date construct indicating an
instant in time associated with an event early in the life cycle of instant in time associated with an event early in the life cycle of
the entry. the entry.
atomPublished = element atom:published { atomDateConstruct } atomPublished = element atom:published { atomDateConstruct }
Typically, atom:published will be associated with the initial Typically, atom:published will be associated with the initial
creation or first availability of the resource. creation or first availability of the resource.
4.2.10 The "atom:rights" Element 4.2.10. The "atom:rights" Element
The "atom:rights" element is a Text construct that conveys The "atom:rights" element is a Text construct that conveys
information about rights held in and over an entry or feed. information about rights held in and over an entry or feed.
atomRights = element atom:rights { atomTextConstruct } atomRights = element atom:rights { atomTextConstruct }
The atom:rights element SHOULD NOT be used to convey machine-readable The atom:rights element SHOULD NOT be used to convey machine-readable
licensing information. licensing information.
If an atom:entry element does not contain an atom:rights element, If an atom:entry element does not contain an atom:rights element,
then the atom:rights element of the containing atom:feed element, if then the atom:rights element of the containing atom:feed element, if
present, is considered to apply to the entry. present, is considered to apply to the entry.
4.2.11 The "atom:source" Element 4.2.11. The "atom:source" Element
If an atom:entry is copied from one feed into another feed, then the If an atom:entry is copied from one feed into another feed, then the
source atom:feed's metadata (all child elements of atom:feed other source atom:feed's metadata (all child elements of atom:feed other
than the atom:entry elements) MAY be preserved within the copied than the atom:entry elements) MAY be preserved within the copied
entry by adding an atom:source child element, if it is not already entry by adding an atom:source child element, if it is not already
present in the entry, and including some or all of the source feed's present in the entry, and including some or all of the source feed's
Metadata elements as the atom:source element's children. Such Metadata elements as the atom:source element's children. Such
metadata SHOULD be preserved if the source atom:feed contains any of metadata SHOULD be preserved if the source atom:feed contains any of
the child elements atom:author, atom:contributor, atom:rights, or the child elements atom:author, atom:contributor, atom:rights, or
atom:category and those child elements are not present in the source atom:category and those child elements are not present in the source
skipping to change at page 27, line 39 skipping to change at page 25, line 4
& atomIcon? & atomIcon?
& atomId? & atomId?
& atomLink* & atomLink*
& atomLogo? & atomLogo?
& atomRights? & atomRights?
& atomSubtitle? & atomSubtitle?
& atomTitle? & atomTitle?
& atomUpdated? & atomUpdated?
& extensionElement*) & extensionElement*)
} }
The atom:source element is designed to allow the aggregation of The atom:source element is designed to allow the aggregation of
entries from different feeds while retaining information about an entries from different feeds while retaining information about an
entry's source feed. For this reason, Atom Processors which are entry's source feed. For this reason, Atom Processors that are
performing such aggregation SHOULD include at least the required performing such aggregation SHOULD include at least the required
feed-level Metadata elements (atom:id, atom:title, and atom:updated) feed-level Metadata elements (atom:id, atom:title, and atom:updated)
in the atom:source element. in the atom:source element.
4.2.12 The "atom:subtitle" Element 4.2.12. The "atom:subtitle" Element
The "atom:subtitle" element is a Text construct that conveys a human- The "atom:subtitle" element is a Text construct that conveys a human-
readable description or subtitle for a feed. readable description or subtitle for a feed.
atomSubtitle = element atom:subtitle { atomTextConstruct } atomSubtitle = element atom:subtitle { atomTextConstruct }
4.2.13 The "atom:summary" Element 4.2.13. The "atom:summary" Element
The "atom:summary" element is a Text construct that conveys a short The "atom:summary" element is a Text construct that conveys a short
summary, abstract, or excerpt of an entry. summary, abstract, or excerpt of an entry.
atomSummary = element atom:summary { atomTextConstruct } atomSummary = element atom:summary { atomTextConstruct }
It is not advisable for the atom:summary element to duplicate atom: It is not advisable for the atom:summary element to duplicate
title or atom:content, because Atom Processors might assume there is atom:title or atom:content because Atom Processors might assume there
a useful summary when there is none. is a useful summary when there is none.
4.2.14 The "atom:title" Element 4.2.14. The "atom:title" Element
The "atom:title" element is a Text construct that conveys a human- The "atom:title" element is a Text construct that conveys a human-
readable title for an entry or feed. readable title for an entry or feed.
atomTitle = element atom:title { atomTextConstruct } atomTitle = element atom:title { atomTextConstruct }
4.2.15 The "atom:updated" Element 4.2.15. The "atom:updated" Element
The "atom:updated" element is a Date construct indicating the most The "atom:updated" element is a Date construct indicating the most
recent instant in time when an entry or feed was modified in a way recent instant in time when an entry or feed was modified in a way
the publisher considers significant. Therefore, not all the publisher considers significant. Therefore, not all
modifications necessarily result in a changed atom:updated value. modifications necessarily result in a changed atom:updated value.
atomUpdated = element atom:updated { atomDateConstruct } atomUpdated = element atom:updated { atomDateConstruct }
Publishers MAY change the value of this element over time. Publishers MAY change the value of this element over time.
skipping to change at page 29, line 28 skipping to change at page 26, line 28
feeds so that a passive observer cannot tell what topics the feeds so that a passive observer cannot tell what topics the
recipient is interested in. Of course, many other examples exist as recipient is interested in. Of course, many other examples exist as
well. well.
The algorithm requirements in this section pertain to the Atom The algorithm requirements in this section pertain to the Atom
Processor. They require that a recipient, at a minimum, be able to Processor. They require that a recipient, at a minimum, be able to
handle messages that use the specified cryptographic algorithms. handle messages that use the specified cryptographic algorithms.
These requirements do not limit the algorithms that the sender can These requirements do not limit the algorithms that the sender can
choose. choose.
5.1 Digital Signatures 5.1. Digital Signatures
The root of an Atom Document (i.e., atom:feed in an Atom Feed The root of an Atom Document (i.e., atom:feed in an Atom Feed
Document, atom:entry in an Atom Entry Document), or any atom:entry Document, atom:entry in an Atom Entry Document) or any atom:entry
element, MAY have an Enveloped Signature, as described by XML- element MAY have an Enveloped Signature, as described by XML-
Signature and Syntax Processing [W3C.REC-xmldsig-core-20020212]. Signature and Syntax Processing [W3C.REC-xmldsig-core-20020212].
Atom Processors MUST NOT reject an Atom Document containing such a Atom Processors MUST NOT reject an Atom Document containing such a
signature because they are not capable of verifying it; they MUST signature because they are not capable of verifying it; they MUST
continue processing and MAY inform the user of their failure to continue processing and MAY inform the user of their failure to
validate the signature. validate the signature.
In other words, the presence of an element with the namespace URI In other words, the presence of an element with the namespace URI
"http://www.w3.org/2000/09/xmldsig#" and a local name of "Signature" "http://www.w3.org/2000/09/xmldsig#" and a local name of "Signature"
as a child of the document element MUST NOT cause an Atom Processor as a child of the document element MUST NOT cause an Atom Processor
skipping to change at page 30, line 6 skipping to change at page 27, line 6
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.
Section 6.5.1 of [W3C.REC-xmldsig-core-20020212] requires support for Section 6.5.1 of [W3C.REC-xmldsig-core-20020212] requires support for
Canonical XML [W3C.REC-xml-c14n-20010315]. However, many Canonical XML [W3C.REC-xml-c14n-20010315]. However, many
implementers do not use it because signed XML documents enclosed in implementers do not use it because signed XML documents enclosed in
other XML documents have their signatures broken. Thus, Atom other XML documents have their signatures broken. Thus, Atom
Processors that verify signed Atom Documents MUST be able to Processors that verify signed Atom Documents MUST be able to
canonicalize with the exclusive XML canonicalization method canonicalize with the exclusive XML canonicalization method
identified by the URI "http://www.w3.org/2001/10/xml-exc-c14n#", as identified by the URI "http://www.w3.org/2001/10/xml-exc-c14n#", as
specified in Exclusive XML Canonicalization [W3C.REC-xml-exc-c14n- specified in Exclusive XML Canonicalization
20020718]. [W3C.REC-xml-exc-c14n-20020718].
Intermediaries such as aggregators may need to add an atom:source Intermediaries such as aggregators may need to add an atom:source
element to an entry that does not contain its own atom:source element to an entry that does not contain its own atom:source
element. If such an entry is signed, the addition will break the element. If such an entry is signed, the addition will break the
signature. Thus, a publisher of individually-signed entries should signature. Thus, a publisher of individually-signed entries should
strongly consider adding an atom:source element to those entries strongly consider adding an atom:source element to those entries
before signing them. Implementors should also be aware of the issues before signing them. Implementers should also be aware of the issues
concerning the use of markup in the "xml:" namespace as it interacts concerning the use of markup in the "xml:" namespace as it interacts
with canonicalization. with canonicalization.
Section 4.4.2 of [W3C.REC-xmldsig-core-20020212] requires support for Section 4.4.2 of [W3C.REC-xmldsig-core-20020212] requires support for
DSA signatures and recommends support for RSA signatures. However, DSA signatures and recommends support for RSA signatures. However,
because of the much greater popularity in the market of RSA versus because of the much greater popularity in the market of RSA versus
DSA, Atom Processors that verify signed Atom Documents MUST be able DSA, Atom Processors that verify signed Atom Documents MUST be able
to verify RSA signatures, but do not need be able to verify DSA to verify RSA signatures, but do not need be able to verify DSA
signatures. Due to security issues that can arise if the keying signatures. Due to security issues that can arise if the keying
material for MAC (message authentication code) authentication is not material for message authentication code (MAC) authentication is not
handled properly, Atom Documents SHOULD NOT use MACs for signatures. handled properly, Atom Documents SHOULD NOT use MACs for signatures.
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
Processing [W3C.REC-xmlenc-core-20021210]. Processing [W3C.REC-xmlenc-core-20021210].
Section 5.1 of [W3C.REC-xmlenc-core-20021210] requires support of Section 5.1 of [W3C.REC-xmlenc-core-20021210] requires support of
TripleDES, AES-128, and AES-256. Atom Processors that decrypt Atom TripleDES, AES-128, and AES-256. Atom Processors that decrypt Atom
Documents MUST be able to decrypt with AES-128 in CBC mode. Documents MUST be able to decrypt with AES-128 in Cipher Block
Chaining (CBC) mode.
Encryption based on [W3C.REC-xmlenc-core-20021210] does not assure Encryption based on [W3C.REC-xmlenc-core-20021210] does not ensure
integrity of the original document. There are known cryptographic integrity of the original document. There are known cryptographic
attacks where someone who cannot decrypt a message can still change attacks where someone who cannot decrypt a message can still change
bits in a way where part or all the decrypted message makes sense but bits in a way where part or all the decrypted message makes sense but
has a different meaning. Thus, Atom Processors that decrypt Atom has a different meaning. Thus, Atom Processors that decrypt Atom
Documents SHOULD check the integrity of the decrypted document by Documents SHOULD check the integrity of the decrypted document by
verifying the hash in the signature (if any) in the document, or by verifying the hash in the signature (if any) in the document, or by
verifying a hash of the document within the document (if any). verifying a hash of the document within the document (if any).
5.3 Signing and Encrypting 5.3. Signing and Encrypting
When an Atom Document is to be both signed and encrypted, it is When an Atom Document is to be both signed and encrypted, it is
generally a good idea to first sign the document, then encrypt the generally a good idea to first sign the document, then encrypt the
signed document. This provides integrity to the base document while signed document. This provides integrity to the base document while
encrypting all the information, including the identity of the entity encrypting all the information, including the identity of the entity
that signed the document. Note that, if MACs are used for that signed the document. Note that, if MACs are used for
authentication, the order MUST be that the signed document is authentication, the order MUST be that the document is signed and
encrypted, and not the other way around. then encrypted, and not the other way around.
6. Extending Atom 6. Extending Atom
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
The Atom namespace is reserved for future forwards-compatible The Atom namespace is reserved for future forward-compatible
revisions of Atom. Future versions of this specification could add revisions of Atom. Future versions of this specification could add
new elements and attributes to the Atom markup vocabulary. Software new elements and attributes to the Atom markup vocabulary. Software
written to conform to this version of the specification will not be written to conform to this version of the specification will not be
able to process such markup correctly and, in fact, will not be able able to process such markup correctly and, in fact, will not be able
to distinguish it from markup error. For the purposes of this to 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 Processing Foreign Markup 6.3. Processing Foreign Markup
Atom Processors which encounter foreign markup in a location that is Atom Processors that encounter foreign markup in a location that is
legal according to this specification MUST NOT stop processing or legal according to this specification MUST NOT stop processing or
signal an error. It might be the case that the Atom Processor is signal an error. It might be the case that the Atom Processor is
able to process the foreign markup correctly and does so. Otherwise, able to process the foreign markup correctly and does so. Otherwise,
such markup is termed "unknown foreign markup". such markup is termed "unknown foreign markup".
When unknown foreign markup is encountered as a child of atom:entry, When unknown foreign markup is encountered as a child of atom:entry,
atom:feed, or a Person construct, Atom Processors MAY bypass the atom:feed, or a Person construct, Atom Processors MAY bypass the
markup and any textual content and MUST NOT change their behavior as markup and any textual content and MUST NOT change their behavior as
a result of the markup's presence. a result of the markup's presence.
When unknown foreign markup is encountered in a Text Construct or When unknown foreign markup is encountered in a Text Construct or
atom:content element, software SHOULD ignore the markup and process atom:content element, software SHOULD ignore the markup and process
any text content of foreign elements as though the surrounding markup any text content of foreign elements as though the surrounding markup
were not present. were not present.
6.4 Extension Elements 6.4. Extension Elements
Atom allows foreign markup anywhere in an Atom document, except where Atom allows foreign markup anywhere in an Atom document, except where
it is explicitly forbidden. Child elements of atom:entry, atom:feed, it is explicitly forbidden. Child elements of atom:entry, atom:feed,
atom:source, and Person constructs are considered Metadata elements, atom:source, and Person constructs are considered Metadata elements
and are described below. Child elements of Person constructs are and are described below. Child elements of Person constructs are
considered to apply to the construct. The role of other foreign considered to apply to the construct. The role of other foreign
markup is undefined by this specification. markup is undefined by this specification.
6.4.1 Simple Extension Elements 6.4.1. Simple Extension Elements
A Simple Extension element MUST NOT have any attributes or child A Simple Extension element MUST NOT have any attributes or child
elements. The element MAY contain character data, or be empty. elements. The element MAY contain character data or be empty.
Simple Extension elements are not Language-Sensitive. Simple Extension elements are not Language-Sensitive.
simpleExtensionElement = simpleExtensionElement =
element * - atom:* { element * - atom:* {
text text
} }
The element can be interpreted as a simple property (or name/value The element can be interpreted as a simple property (or name/value
pair) of the parent element that encloses it. The pair consisting of pair) of the parent element that encloses it. The pair consisting of
the namespace-URI of the element and the local name of the element the namespace-URI of the element and the local name of the element
can be interpreted as the name of the property. The character data can be interpreted as the name of the property. The character data
content of the element can be interpreted as the value of the content of the element can be interpreted as the value of the
property. If the element is empty, then the property value can be property. If the element is empty, then the property value can be
interpreted as an empty string. interpreted as an empty string.
6.4.2 Structured Extension Elements 6.4.2. Structured Extension Elements
The root element of a Structured Extension element MUST have at least The root element of a Structured Extension element MUST have at least
one attribute or child element. It MAY have attributes, it MAY one attribute or child element. It MAY have attributes, it MAY
contain well-formed XML content (including character data), or it MAY contain well-formed XML content (including character data), or it MAY
be empty. Structured Extension elements are Language-Sensitive. be empty. Structured Extension elements are Language-Sensitive.
structuredExtensionElement = structuredExtensionElement =
element * - atom:* { element * - atom:* {
(attribute * { text }+, (attribute * { text }+,
(text|anyElement)*) (text|anyElement)*)
| (attribute * { text }*, | (attribute * { text }*,
(text?, anyElement+, (text|anyElement)*)) (text?, anyElement+, (text|anyElement)*))
} }
The structure of a Structured Extension element, including the order The structure of a Structured Extension element, including the order
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
An Atom Document, when serialized as XML 1.0, can be identified with An Atom Document, when serialized as XML 1.0, can be identified with
the following media type: the following media type:
MIME media type name: application MIME media type name: application
MIME subtype name: atom+xml MIME subtype name: atom+xml
Mandatory parameters: None. Mandatory parameters: None.
Optional parameters: Optional parameters:
"charset": This parameter has semantics identical to the charset
"charset": This parameter has identical semantics to the charset
parameter of the "application/xml" media type as specified in parameter of the "application/xml" media type as specified in
[RFC3023]. [RFC3023].
Encoding considerations: Identical to those of "application/xml" as Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023], section 3.2. described in [RFC3023], Section 3.2.
Security considerations: As defined in this specification. Security considerations: As defined in this specification.
In addition, as this media type uses the "+xml" convention, it In addition, as this media type uses the "+xml" convention, it
shares the same security considerations as described in [RFC3023], shares the same security considerations as described in [RFC3023],
section 10. Section 10.
Interoperability considerations: There are no known interoperability Interoperability considerations: There are no known interoperability
issues. issues.
Published specification: This specification. Published specification: This specification.
Applications that use this media type: No known applications Applications that use this media type: No known applications
currently use this media type. currently use this media type.
Additional information: Additional information:
Magic number(s): As specified for "application/xml" in [RFC3023], Magic number(s): As specified for "application/xml" in [RFC3023],
section 3.2. Section 3.2.
File extension: .atom File extension: .atom
Fragment identifiers: As specified for "application/xml" in Fragment identifiers: As specified for "application/xml" in
[RFC3023], section 5. [RFC3023], Section 5.
Base URI: As specified in [RFC3023], Section 6.
Base URI: As specified in [RFC3023], section 6.
Macintosh File Type code: TEXT Macintosh File Type code: TEXT
Person and email address to contact for further information: Mark Person and email address to contact for further information: Mark
Nottingham <mnot@pobox.com> Nottingham <mnot@pobox.com>
Intended usage: COMMON Intended usage: COMMON
Author/Change controller: IESG Author/Change controller: IESG
7.1 Registry of Link Relations 7.1. Registry of Link Relations
This registry is maintained by IANA and initially contains five This registry is maintained by IANA and initially contains five
values: "alternate", "related", "self", "enclosure", and "via". New values: "alternate", "related", "self", "enclosure", and "via". New
assignments are subject to IESG Approval, as outlined in [RFC2434]. assignments are subject to IESG Approval, as outlined in [RFC2434].
Requests should be made by email to IANA, which will then forward the Requests should be made by email to IANA, which will then forward the
request to the IESG requesting approval. The request should use the request to the IESG, requesting approval. The request should use the
following template: following template:
o Attribute Value: ( A value for the "rel" attribute that conforms o Attribute Value: (A value for the "rel" attribute that conforms to
to the syntax rule given in Section 4.2.7.2 ) the syntax rule given in Section 4.2.7.2)
o Description: o Description:
o Expected display characteristics: o Expected display characteristics:
o Security considerations: o Security considerations:
8. Security Considerations 8. Security Considerations
8.1 HTML and XHTML Content 8.1. HTML and XHTML Content
Text constructs and atom:content allow the delivery of HTML and Text constructs and atom:content allow the delivery of HTML and
XHTML. Many elements in these languages are considered 'unsafe' in XHTML. Many elements in these languages are considered 'unsafe' in
that they open clients to one or more types of attack. Implementers that they open clients to one or more types of attack. Implementers
of software which processes Atom should carefully consider their of software that processes Atom should carefully consider their
handling of every type of element when processing incoming (X)HTML in handling of every type of element when processing incoming (X)HTML in
Atom Documents. See the security sections of [RFC2854] and [HTML] Atom Documents. See the security sections of [RFC2854] and [HTML]
for guidance. for guidance.
Atom Processors should pay particular attention to the security of Atom Processors should pay particular attention to the security of
the IMG, SCRIPT, EMBED, OBJECT, FRAME, FRAMESET, IFRAME, META, and the IMG, SCRIPT, EMBED, OBJECT, FRAME, FRAMESET, IFRAME, META, and
LINK elements, but other elements might also have negative security LINK elements, but other elements might also have negative security
properties. properties.
(X)HTML can either directly contain or indirectly reference (X)HTML can either directly contain or indirectly reference
executable content. executable content.
8.2 URIs 8.2. URIs
Atom Processors handle URIs. See Section 7 of [RFC3986]. Atom Processors handle URIs. See Section 7 of [RFC3986].
8.3 IRIs 8.3. IRIs
Atom Processors handle IRIs. See Section 8 of [RFC3987]. Atom Processors handle IRIs. See Section 8 of [RFC3987].
8.4 Spoofing 8.4. Spoofing
Atom Processors should be aware of the potential for spoofing attacks Atom Processors should be aware of the potential for spoofing attacks
where the attacker publishes an atom:entry with the atom:id value of where the attacker publishes an atom:entry with the atom:id value of
an entry from another feed, perhaps with a falsified atom:source an entry from another feed, perhaps with a falsified atom:source
element duplicating the atom:id of the other feed. For example, an element duplicating the atom:id of the other feed. For example, an
Atom Processor could suppress display of duplicate entries by Atom Processor could suppress display of duplicate entries by
displaying only one entry from a set of entries with identical displaying only one entry from a set of entries with identical
atom:id values. In that situation, the Atom Processor might also atom:id values. In that situation, the Atom Processor might also
take steps to determine whether the entries originated from the same take steps to determine whether the entries originated from the same
publisher before considering them to be duplicates. publisher before considering them duplicates.
8.5 Encryption and Signing 8.5. Encryption and Signing
Atom Documents can be encrypted and signed using [W3C.REC-xmlenc- Atom Documents can be encrypted and signed using
core-20021210] and [W3C.REC-xmldsig-core-20020212], respectively, and [W3C.REC-xmlenc-core-20021210] and [W3C.REC-xmldsig-core-20020212],
are subject to the security considerations implied by their use. respectively, and are subject to the security considerations implied
by their use.
Digital signatures provide authentication, message integrity, and Digital signatures provide authentication, message integrity, and
non-repudiation with proof of origin. Encryption provides data non-repudiation with proof of origin. Encryption provides data
confidentiality. confidentiality.
9. References 9. References
9.1 Normative References 9.1. Normative References
[HTML] Raggett, D., Hors, A., and I. Jacobs, "HTML 4.01 [HTML] Raggett, D., Hors, A., and I. Jacobs, "HTML 4.01
Specification", W3C REC REC-html401-19991224, Specification", W3C REC REC-html401-19991224,
December 1999, December 1999,
<http://www.w3.org/TR/1999/REC-html401-19991224>. <http://www.w3.org/TR/1999/REC-html401-19991224>.
[MIMEREG] Freed, N. and J. Klensin, "Media Type Specifications and [MIMEREG] Freed, N. and J. Klensin, "Media Type Specifications and
Registration Procedures", work-in-progress Registration Procedures", BCP 13, RFC 4288, December 2005.
(draft-freed-media-type-reg-04), April 2005.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, [RFC2822] Resnick, P., "Internet Message Format", RFC 2822,
April 2001. April 2001.
[RFC2854] Connolly, D. and L. Masinter, "The 'text/html' Media [RFC2854] Connolly, D. and L. Masinter, "The 'text/html' Media
Type", RFC 2854, June 2000. Type", RFC 2854, June 2000.
skipping to change at page 38, line 50 skipping to change at page 33, line 19
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
[RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005. Identifiers (IRIs)", RFC 3987, January 2005.
[W3C.REC-xml-20040204] [W3C.REC-xml-20040204]
Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T., Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T.,
and E. Maler, "Extensible Markup Language (XML) 1.0 (Third and E. Maler, "Extensible Markup Language (XML) 1.0 (Third
Edition)", W3C REC REC-xml-20040204, February 2004, Edition)", W3C REC REC-xml-20040204, February 2004,
<http://www.w3.org/TR/2004/REC-xml-2004020>. <http://www.w3.org/TR/2004/REC-xml-20040204>.
[W3C.REC-xml-c14n-20010315] [W3C.REC-xml-c14n-20010315]
Boyer, J., "Canonical XML Version 1.0", W3C REC REC-xml- Boyer, J., "Canonical XML Version 1.0", W3C REC REC-xml-
c14n-20010315, March 2001, c14n-20010315, March 2001,
<http://www.w3.org/TR/2001/REC-xml-c14n-20010315>. <http://www.w3.org/TR/2001/REC-xml-c14n-20010315>.
[W3C.REC-xml-exc-c14n-20020718] [W3C.REC-xml-exc-c14n-20020718]
Eastlake, D., Boyer, J., and J. Reagle, "Exclusive XML Eastlake, D., Boyer, J., and J. Reagle, "Exclusive XML
Canonicalization Version 1.0", W3C REC REC-xml-exc-c14n- Canonicalization Version 1.0", W3C REC REC-xml-exc-c14n-
20020718, July 2002, 20020718, July 2002,
skipping to change at page 39, line 48 skipping to change at page 34, line 17
Processing", W3C REC REC-xmlenc-core-20021210, Processing", W3C REC REC-xmlenc-core-20021210,
December 2002, December 2002,
<http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>. <http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.
[XHTML] Altheim, M., Boumphrey, F., McCarron, S., Dooley, S., [XHTML] Altheim, M., Boumphrey, F., McCarron, S., Dooley, S.,
Schnitzenbaumer, S., and T. Wugofski, "Modularization of Schnitzenbaumer, S., and T. Wugofski, "Modularization of
XHTML[TM]", W3C REC REC-xhtml-modularization-20010410, XHTML[TM]", W3C REC REC-xhtml-modularization-20010410,
April 2001, <http://www.w3.org/TR/2001/ April 2001, <http://www.w3.org/TR/2001/
REC-xhtml-modularization-20010410>. REC-xhtml-modularization-20010410>.
9.2 Informative References 9.2. Informative References
[ISO.8601.1988] [ISO.8601.1988]
International Organization for Standardization, "Data International Organization for Standardization, "Data
elements and interchange formats - Information interchange elements and interchange formats - Information interchange
- Representation of dates and times", ISO Standard 8601, - Representation of dates and times", ISO Standard 8601,
June 1988. June 1988.
[RELAX-NG] [RELAX-NG] Clark, J., "RELAX NG Compact Syntax", December 2001,
Clark, J., "RELAX NG Compact Syntax", December 2001,
<http://www.oasis-open.org/committees/relax-ng/ <http://www.oasis-open.org/committees/relax-ng/
compact-20021121.html>. compact-20021121.html>.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434, IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998. October 1998.
[W3C.NOTE-datetime-19980827] [W3C.NOTE-datetime-19980827]
Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C Wolf, M. and C. Wicksteed, "Date and Time Formats", W3C
NOTE NOTE-datetime-19980827, August 1998, NOTE NOTE-datetime-19980827, August 1998,
<http://www.w3.org/TR/1998/NOTE-datetime-19980827>. <http://www.w3.org/TR/1998/NOTE-datetime-19980827>.
[W3C.REC-xmlschema-2-20041028] [W3C.REC-xmlschema-2-20041028]
Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
Second Edition", W3C REC REC-xmlschema-2-20041028, Second Edition", W3C REC REC-xmlschema-2-20041028,
October 2004, October 2004,
<http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>. <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.
Authors' Addresses
Mark Nottingham (editor)
Email: mnot@pobox.com
URI: http://www.mnot.net/
Robert Sayre (editor)
Email: rfsayre@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 versions 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 Atompub Working Group. product of the Atom community and the Atompub Working Group.
The Atompub Working Group has dozens of very active contributors who The Atompub Working Group has dozens of very active contributors who
proposed ideas and wording for this document, including: proposed ideas and wording for this document, including:
Danny Ayers, James Aylett, Roger Benningfield, Arve Bersvendsen, Tim Danny Ayers, James Aylett, Roger Benningfield, Arve Bersvendsen, Tim
Bray, Dan Brickley, Thomas Broyer, Robin Cover, Bill de hOra, Martin Bray, Dan Brickley, Thomas Broyer, Robin Cover, Bill de hOra, Martin
Duerst, Roy Fielding, Joe Gregorio, Bjoern Hoehrmann, Paul Hoffman, Duerst, Roy Fielding, Joe Gregorio, Bjoern Hoehrmann, Paul Hoffman,
skipping to change at page 42, line 10 skipping to change at page 35, line 30
Pilgrim, David Powell, Julian Reschke, Phil Ringnalda, Antone Roundy, Pilgrim, David Powell, Julian Reschke, Phil Ringnalda, Antone Roundy,
Sam Ruby, Eric Scheid, Brent Simmons, Henri Sivonen, Ray Slakinski, Sam Ruby, Eric Scheid, Brent Simmons, Henri Sivonen, Ray Slakinski,
James Snell, Henry Story, Asbjorn Ulsberg, Walter Underwood, Norman James Snell, Henry Story, Asbjorn Ulsberg, Walter Underwood, Norman
Walsh, Dave Winer, and Bob Wyman. Walsh, Dave Winer, and Bob Wyman.
Appendix B. RELAX NG Compact Schema Appendix B. RELAX NG Compact Schema
This appendix is informative. This appendix is informative.
The Relax NG schema explicitly excludes elements in the Atom The Relax NG schema explicitly excludes elements in the Atom
namespace which are not defined in this revision of the namespace that are not defined in this revision of the specification.
specification. Requirements for Atom Processors encountering such Requirements for Atom Processors encountering such markup are given
markup are given in Section 6.2 and Section 6.3. in Sections 6.2 and 6.3.
# -*- rnc -*- # -*- rnc -*-
# RELAX NG Compact Syntax Grammar for the # RELAX NG Compact Syntax Grammar for the
# Atom Format Specification Version 11 # Atom Format Specification Version 11
namespace atom = "http://www.w3.org/2005/Atom" namespace atom = "http://www.w3.org/2005/Atom"
namespace xhtml = "http://www.w3.org/1999/xhtml" namespace xhtml = "http://www.w3.org/1999/xhtml"
namespace s = "http://www.ascc.net/xml/schematron" namespace s = "http://www.ascc.net/xml/schematron"
namespace local = "" namespace local = ""
skipping to change at page 50, line 5 skipping to change at page 42, line 34
} }
xhtmlDiv = element xhtml:div { xhtmlDiv = element xhtml:div {
(attribute * { text } (attribute * { text }
| text | text
| anyXHTML)* | anyXHTML)*
} }
# EOF # EOF
Appendix C. Change Log Authors' Addresses
[[anchor70: This section should be removed before final
publication.]]
-10: capitalize "Atom Document" consistently.
fix atom:feed/atom:logo
fix link hreflang/alternate in atom:feed
Add more acknowledgements
Expand security section
Clarify IRI processing
-09: Changed atom:copyright to atom:rights.
Clarify atom:source, also reflect changes to atom:feed
Change 'minimal' to brief (PaceBriefExample).
Add text about "Atom 1.0" (PaceAtom10).
Remove SHOULD about content@src.
feed/id now required.
rework xml:base text
rework xml:lang terms and requirements
rework escaped markup explanations
change atom:image to atom:logo
Add example Date Constructs
Clarify that atom:link and atom:category MUST be empty.
Make XHTML definitions consistent
atom:icon editorial fix-- capitalize SHOULD.
-08: Remove BNF
complete rather than collected schema
Remove a couple introductory sentences
update MIME references
Many editorial adjustments
-07: Change atom:source-feed to atom:source.
Add ABNF reference
Many editorial tweaks
Rework extensibility
Adjust page breaks in txt version
-06: Move Identity Construct into atom:id (only place it's used)
atom:id values must be unique within a feed.
restore atom:copyright definition mistakenly dropped during
alphabetizing.
Remove atom:head, add atom:source-feed, and "Extension Construct"
text in an effort to accurately reflect WG consensus on data model
and extensibility, acknowledging two opinions in favor of atom:
head.
Note @hreflang issue.
Add comment on atom:entry/atom:summary requirements.
Rework atom:id text. The dereferencing section didn't talk about
dereferencing.
Remove protocol reference.
Alphabetize where appropriate (PaceOrderSpecAlphabetically).
Add mI language (PaceExtendingAtom).
Add atom:icon and atom:image (PaceImageAndIcon).
Change atom:tagline to atom:subtitle
Add inline XHTML language (PaceXHTMLNamespaceDiv).
Change "TEXT" etc, to lowercase
Change example id IRI to urn:uuid:...
Add rel="self" (PaceFeedLink).
Add Feed State text (PaceNoFeedState).
Move to IRIs (PaceIRI).
Add rel="via" (PaceLinkRelVia).
Add rel="enclosure" (PaceEnclosuresAndPix).
Remove info and host (PaceRemoveInfoAndHost)
Clarify order of entries (PaceEntryOrder).
Remove version attribute (PaceRemoveVersionAttr).
Date format roundup (PaceDatesXSD).
Remove Service construct and elements.
fix atom:contributor cardinality typo
Removed motivation/design principles note; if we haven't come up
with them by now...
Put conformance text into notational conventions.
Removed instances of 'software'; too specific.
Added refs to HTML and XHTML.
Updated ref to Infoset.
Various editorial tweaks.
Fix RFC 3023 refs in IANA section
Adjust head/link requirement
fix @version typos
-05: Add RNC from N. Walsh.
Re-organize element definitions.
Lift the prohibition on other types of DSig and encryption.
Remove text on "indiscriminate use" of DSig and XMLEnc.
-04: Update URI terms for 2396bis.
Add Category construct (PaceCategoryRevised).
Insert paranoid XHTML interpretation guidelines.
Adjust atom:copyright, per chairs' instruction.
Add atom:host as child element of atom:entry, per chairs'
direction (PacePersonConstruct).
Add link/content co-constraint (PaceContentOrLink).
Remove atom:origin as a side effect of adding atom:head to atom:
entry (PaceHeadInEntry).
Add optional length attribute to atom:link (PaceLinkRelated).
Add Link registry to Link Construct, IANA Considerations
placeholder (PaceFieldingLinks).
Change definition of atom:updated (PaceUpdatedDefinition).
-03: Move definition of Link @rel to format spec, restrict
acceptable values (PaceMoveLinkElement, PaceLinkAttrDefaults).
Add Service Construct, head/post, head/introspection, entry/edit
(PaceServiceElement).
Add Text Construct, entry/content (PaceReformedContent3).
Add entry/published (PaceDatePublished).
Adjust definition of Identity Construct per chairs' direction to
"fix it."
Add Sayre to editors.
-02: Removed entry/modified, entry/issued, entry/created; added
entry/updated (PaceDateUpdated).
Changed date construct from W3C date-time to RFC3339
(PaceDateUpdated).
Feed links to HTML pages should be reflected back
(PaceLinkReflection).
Added Identity construct (PaceIdConstruct).
Changed feed/id and entry/id to be Identity constructs
(PaceIdConstruct).
Changed entry/origin's content so that it's the same as the feed's
id, rather than its link/@rel="alternate" (PaceIdConstruct).
Added "Securing Atom Documents" (PaceDigitalSignatures).
-01: Constrained omission of "Information Item" to just elements and
attributes.
Clarified xml:lang inheritence.
Removed entry- and feed-specific langauge about xml:lang (covered
by general discussion of xml:lang)
Changed xml:lang to reference XML for normative requirements.
Changed "... MUST be a string" to "... is unstructued text."
Remomved langauge about DOCTYPEs, PIs, Comments, Entities.
Changed atom:url to atom:uri, @url to @uri
Introduced atom:head
Introduced "Atom Feed Document" and "Atom Entry Document".
Removed requirement for all elements and attributes to be
namespace-qualified; now children of selective elements
Added extensibility to Person constructs.
Removed requirement for media types to be registered (non-
registered media types are legal)
Added atom:origin (PaceEntryOrigin)
Added requirement for entry/id to be present and a URI
(PaceEntryIdRequired).
Clarified approach to Comments, PIs and well-formedness, as per
RFC3470.
Referenced escaping algorithm in XML.
Assorted editorial nits and cleanup, refactoring
-00: Initial IETF Internet-Draft submission.
Added optional version attribute to entry
(PaceEntryElementNeedsVersionAttribute).
Added hreflang attribute (PaceHrefLang). Mark Nottingham (editor)
Clarified inheritence of copyright element (PaceItemCopyright). EMail: mnot@pobox.com
URI: http://www.mnot.net/
Added xml:lang to entries (PaceItemLang). Robert Sayre (editor)
Tweaked Infoset-related language (PaceNoInfoSet). EMail: rfsayre@boswijck.com
URI: http://boswijck.com
Clarified lack of structure in version attribute Full Copyright Statement
(PaceVersionAsText).
Changed approach to XML Base (PaceXmlBaseEverywhere). Copyright (C) The Internet Society (2005).
Added XML Base processing to atom:id (PaceXmlBaseId). This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
Various editorial cleanup and adjustments for IETF publication. This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property Statement Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79. found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at this standard. Please address the information to the IETF at ietf-
ietf-ipr@ietf.org. ipr@ietf.org.
Disclaimer of Validity
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgement
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
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