draft-ietf-atompub-format-03.txt   draft-ietf-atompub-format-04.txt 
Network Working Group M. Nottingham, Ed. Network Working Group M. Nottingham, Ed.
Internet-Draft Internet-Draft
Expires: April 20, 2005 R. Sayre, Ed. Expires: July 11, 2005 R. Sayre, Ed.
Boswijck Memex Consulting Boswijck Memex Consulting
October 20, 2004 January 10, 2005
The Atom Syndication Format The Atom Syndication Format
draft-ietf-atompub-format-03 draft-ietf-atompub-format-04
Status of this Memo Status of this Memo
By submitting this Internet-Draft, I certify that any applicable By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been disclosed, patent or other IPR claims of which I am aware have been disclosed,
and any of which I become aware will be disclosed, in accordance with and any of which I become aware will be disclosed, in accordance with
RFC 3668. RFC 3668.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 34 skipping to change at page 1, line 35
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
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This Internet-Draft will expire on April 20, 2005. This Internet-Draft will expire on July 11, 2005.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved. Copyright (C) The Internet Society (2005). All Rights Reserved.
Abstract Abstract
This document specifies Atom, an XML-based Web content and metadata This document specifies Atom, an XML-based Web content and metadata
syndication format. syndication format.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Editorial Notes . . . . . . . . . . . . . . . . . . . . . 4 1.1 Editorial Notes . . . . . . . . . . . . . . . . . . . . . 4
1.2 Example . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 Example . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3 Conformance . . . . . . . . . . . . . . . . . . . . . . . 5 1.3 Conformance . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Notational Conventions . . . . . . . . . . . . . . . . . . 5 1.4 Notational Conventions . . . . . . . . . . . . . . . . . . 5
2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 7 2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 7
3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 8 3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 8
3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 8 3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 8
3.1.1 "type" Attribute . . . . . . . . . . . . . . . . . . . 8 3.1.1 "type" Attribute . . . . . . . . . . . . . . . . . . . 8
3.2 Person Constructs . . . . . . . . . . . . . . . . . . . . 8 3.2 Person Constructs . . . . . . . . . . . . . . . . . . . . 9
3.2.1 "atom:name" Element . . . . . . . . . . . . . . . . . 9 3.2.1 "atom:name" Element . . . . . . . . . . . . . . . . . 9
3.2.2 "atom:uri" Element . . . . . . . . . . . . . . . . . . 9 3.2.2 "atom:uri" Element . . . . . . . . . . . . . . . . . . 9
3.2.3 "atom:email" Element . . . . . . . . . . . . . . . . . 9 3.2.3 "atom:email" Element . . . . . . . . . . . . . . . . . 9
3.3 Date Constructs . . . . . . . . . . . . . . . . . . . . . 9 3.3 Date Constructs . . . . . . . . . . . . . . . . . . . . . 9
3.4 Service Constructs . . . . . . . . . . . . . . . . . . . . 9 3.4 Service Constructs . . . . . . . . . . . . . . . . . . . . 9
3.4.1 "href" Attribute . . . . . . . . . . . . . . . . . . . 9 3.4.1 "href" Attribute . . . . . . . . . . . . . . . . . . . 10
3.5 Link Constructs . . . . . . . . . . . . . . . . . . . . . 10 3.5 Link Constructs . . . . . . . . . . . . . . . . . . . . . 10
3.5.1 "rel" Attribute . . . . . . . . . . . . . . . . . . . 10 3.5.1 "rel" Attribute . . . . . . . . . . . . . . . . . . . 10
3.5.2 "type" Attribute . . . . . . . . . . . . . . . . . . . 10 3.5.2 "type" Attribute . . . . . . . . . . . . . . . . . . . 11
3.5.3 "href" Attribute . . . . . . . . . . . . . . . . . . . 10 3.5.3 "href" Attribute . . . . . . . . . . . . . . . . . . . 11
3.5.4 "hreflang" Attribute . . . . . . . . . . . . . . . . . 10 3.5.4 "hreflang" Attribute . . . . . . . . . . . . . . . . . 11
3.5.5 "title" Attribute . . . . . . . . . . . . . . . . . . 11 3.5.5 "title" Attribute . . . . . . . . . . . . . . . . . . 11
3.6 Identity Constructs . . . . . . . . . . . . . . . . . . . 11 3.5.6 "length" Attribute . . . . . . . . . . . . . . . . . . 11
3.6.1 Dereferencing Identity Constructs . . . . . . . . . . 11 3.6 Identity Constructs . . . . . . . . . . . . . . . . . . . 12
3.6.1 Dereferencing Identity Constructs . . . . . . . . . . 12
3.6.2 Comparing Identity Constructs . . . . . . . . . . . . 12 3.6.2 Comparing Identity Constructs . . . . . . . . . . . . 12
4. The "atom:feed" Element . . . . . . . . . . . . . . . . . . 13 3.7 The Category Construct . . . . . . . . . . . . . . . . . . 13
4.1 "version" Attribute . . . . . . . . . . . . . . . . . . . 13 3.7.1 The "term" Attribute . . . . . . . . . . . . . . . . . 13
4.2 The "atom:head" Element . . . . . . . . . . . . . . . . . 13 3.7.2 The "scheme" Attribute . . . . . . . . . . . . . . . . 13
4.2.1 "atom:title" Element . . . . . . . . . . . . . . . . . 13 3.7.3 The "label" attribute . . . . . . . . . . . . . . . . 13
4.2.2 "atom:link" Element . . . . . . . . . . . . . . . . . 13 4. The "atom:feed" Element . . . . . . . . . . . . . . . . . . 14
4.2.3 "atom:introspection" Element . . . . . . . . . . . . . 14 4.1 "version" Attribute . . . . . . . . . . . . . . . . . . . 14
4.2.4 "atom:post" Element . . . . . . . . . . . . . . . . . 14 4.2 The "atom:head" Element . . . . . . . . . . . . . . . . . 14
4.2.5 "atom:author" Element . . . . . . . . . . . . . . . . 14 4.2.1 "atom:title" Element . . . . . . . . . . . . . . . . . 14
4.2.6 "atom:contributor" Element . . . . . . . . . . . . . . 14 4.2.2 "atom:link" Element . . . . . . . . . . . . . . . . . 14
4.2.7 "atom:tagline" Element . . . . . . . . . . . . . . . . 14 4.2.3 "atom:category" Element . . . . . . . . . . . . . . . 15
4.2.8 "atom:id" Element . . . . . . . . . . . . . . . . . . 14 4.2.4 "atom:introspection" Element . . . . . . . . . . . . . 15
4.2.9 "atom:generator" Element . . . . . . . . . . . . . . . 15 4.2.5 "atom:post" Element . . . . . . . . . . . . . . . . . 15
4.2.10 "atom:copyright" Element . . . . . . . . . . . . . . 15 4.2.6 "atom:author" Element . . . . . . . . . . . . . . . . 15
4.2.11 "atom:info" Element . . . . . . . . . . . . . . . . 15 4.2.7 "atom:contributor" Element . . . . . . . . . . . . . . 15
4.2.12 "atom:updated" Element . . . . . . . . . . . . . . . 16 4.2.8 "atom:tagline" Element . . . . . . . . . . . . . . . . 15
5. The "atom:entry" Element . . . . . . . . . . . . . . . . . . 17 4.2.9 "atom:id" Element . . . . . . . . . . . . . . . . . . 16
5.1 "atom:title" Element . . . . . . . . . . . . . . . . . . . 17 4.2.10 "atom:generator" Element . . . . . . . . . . . . . . 16
5.2 "atom:link" Element . . . . . . . . . . . . . . . . . . . 17 4.2.11 "atom:copyright" Element . . . . . . . . . . . . . . 16
5.3 "atom:edit" Element . . . . . . . . . . . . . . . . . . . 17 4.2.12 "atom:info" Element . . . . . . . . . . . . . . . . 16
5.4 "atom:author" Element . . . . . . . . . . . . . . . . . . 18 4.2.13 "atom:updated" Element . . . . . . . . . . . . . . . 16
5.5 "atom:contributor" Element . . . . . . . . . . . . . . . . 18 5. The "atom:entry" Element . . . . . . . . . . . . . . . . . . 18
5.6 "atom:id" Element . . . . . . . . . . . . . . . . . . . . 18 5.1 "atom:title" Element . . . . . . . . . . . . . . . . . . . 18
5.7 "atom:updated" Element . . . . . . . . . . . . . . . . . . 18 5.2 "atom:link" Element . . . . . . . . . . . . . . . . . . . 18
5.8 "atom:published" Element . . . . . . . . . . . . . . . . . 18 5.3 "atom:category" Element . . . . . . . . . . . . . . . . . 18
5.9 "atom:summary" Element . . . . . . . . . . . . . . . . . . 19 5.4 "atom:edit" Element . . . . . . . . . . . . . . . . . . . 19
5.10 "atom:content" Element . . . . . . . . . . . . . . . . . 19 5.5 "atom:author" Element . . . . . . . . . . . . . . . . . . 19
5.10.1 "type" attribute . . . . . . . . . . . . . . . . . . 19 5.6 "atom:contributor" Element . . . . . . . . . . . . . . . . 19
5.10.2 "src" attribute . . . . . . . . . . . . . . . . . . 19 5.7 "atom:host" Element . . . . . . . . . . . . . . . . . . . 19
5.10.3 Processing Model . . . . . . . . . . . . . . . . . . 20 5.8 "atom:id" Element . . . . . . . . . . . . . . . . . . . . 19
5.11 "atom:copyright" Element . . . . . . . . . . . . . . . . 21 5.9 "atom:updated" Element . . . . . . . . . . . . . . . . . . 19
5.12 "atom:origin" Element . . . . . . . . . . . . . . . . . 21 5.10 "atom:published" Element . . . . . . . . . . . . . . . . 20
6. Managing Feed State . . . . . . . . . . . . . . . . . . . . 22 5.11 "atom:summary" Element . . . . . . . . . . . . . . . . . 20
7. Securing Atom Documents . . . . . . . . . . . . . . . . . . 23 5.12 "atom:content" Element . . . . . . . . . . . . . . . . . 20
7.1 Digital Signatures . . . . . . . . . . . . . . . . . . . . 23 5.12.1 "type" attribute . . . . . . . . . . . . . . . . . . 20
7.2 Encryption . . . . . . . . . . . . . . . . . . . . . . . . 23 5.12.2 "src" attribute . . . . . . . . . . . . . . . . . . 21
8. Embedding Atom in Other Formats . . . . . . . . . . . . . . 24 5.12.3 Processing Model . . . . . . . . . . . . . . . . . . 21
9. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 25 5.13 "atom:copyright" Element . . . . . . . . . . . . . . . . 22
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 26 5.14 "atom:head" Element . . . . . . . . . . . . . . . . . . 22
11. Security Considerations . . . . . . . . . . . . . . . . . . 27 6. Managing Feed State . . . . . . . . . . . . . . . . . . . . 23
12. Normative References . . . . . . . . . . . . . . . . . . . . 27 7. Securing Atom Documents . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 28 7.1 Digital Signatures . . . . . . . . . . . . . . . . . . . . 24
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 29 7.2 Encryption . . . . . . . . . . . . . . . . . . . . . . . . 24
B. Revision History . . . . . . . . . . . . . . . . . . . . . . 30 8. Embedding Atom in Other Formats . . . . . . . . . . . . . . 25
Intellectual Property and Copyright Statements . . . . . . . 32 9. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 26
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 27
10.1 Registry of Link Relations . . . . . . . . . . . . . . . 27
11. Security Considerations . . . . . . . . . . . . . . . . . . 29
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
12.1 Normative References . . . . . . . . . . . . . . . . . . . 30
12.2 Informative References . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 32
A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 33
B. Revision History . . . . . . . . . . . . . . . . . . . . . . 34
Intellectual Property and Copyright Statements . . . . . . . 36
1. Introduction 1. Introduction
Atom is an XML-based document format intended to allow lists of Atom is an XML-based document format intended to allow lists of
related information, known as "feeds", to be synchronised between related information, known as "feeds". Feeds are composed of a
publishers and consumers. Feeds are composed of a number of items, number of items, known as "entries", each with an extensible set of
known as "entries", each with an extensible set of attached metadata. attached metadata. For example, each entry has a title.
For example, each entry has a title.
The primary use case that Atom addresses is the syndication of Web The primary use case that Atom addresses is the syndication of Web
content such as Weblogs and news headlines to Web sites as well as content such as Weblogs and news headlines to Web sites as well as
directly to user agents. However, nothing precludes it from being directly to user agents. However, nothing precludes it from being
used for other purposes and kinds of content. used for other purposes and kinds of content.
Details of communication protocols between software agents using Atom Details of communication protocols between software agents using Atom
can be found in the Atom Protocol specification [Atom-protocol]. can be found in the Atom Protocol specification [Atom-protocol].
[[ more motivation / design principles ]] [[ more motivation / design principles ]]
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used for issue tracking and new proposals. used for issue tracking and new proposals.
This document is an early draft and known to be incomplete. Topics This document is an early draft and known to be incomplete. Topics
marked [[like this]] indicate where additional text is likely to be marked [[like this]] indicate where additional text is likely to be
added. added.
1.2 Example 1.2 Example
A minimal, single-entry Atom Feed Document: A minimal, single-entry Atom Feed Document:
<?xml version="1.0" encoding="utf-8"?> <?xml version="1.0" encoding="UTF-8"?>
<feed version="draft-ietf-atompub-format-03: do not deploy" <feed version="draft-ietf-atompub-format-04
xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-03"> : do not deploy"
xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-04
">
<head> <head>
<title>Example Feed</title> <title>Example Feed</title>
<link href="http://example.org/"/> <link href="http://example.org/"/>
<updated>2003-12-13T18:30:02Z</updated> <updated>2003-12-13T18:30:02Z</updated>
<author> <author>
<name>John Doe</name> <name>John Doe</name>
</author> </author>
</head> </head>
<entry> <entry>
<title>Atom-Powered Robots Run Amok</title> <title>Atom-Powered Robots Run Amok</title>
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1.4 Notational Conventions 1.4 Notational Conventions
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]. document are to be interpreted as described in BCP 14, [RFC2119].
This specification uses XML Namespaces [W3C.REC-xml-names-19990114] This specification uses XML Namespaces [W3C.REC-xml-names-19990114]
to uniquely identify XML elements and attribute names. It uses the to uniquely identify XML elements and attribute names. It uses the
following namespace prefixes for the indicated namespace URIs; following namespace prefixes for the indicated namespace URIs;
"atom": http://purl.org/atom/ns#draft-ietf-atompub-format-03 "atom": http://purl.org/atom/ns#draft-ietf-atompub-format-04
Note that the choice of any namespace prefix is arbitrary and not Note that the choice of any namespace prefix is arbitrary and not
semantically significant. semantically significant.
Atom is specified using terms from the XML Infoset Atom is specified using terms from the XML Infoset
[W3C.REC-xml-infoset-20011024]. However, this specification uses a [W3C.REC-xml-infoset-20011024]. However, this specification uses a
shorthand for two common terms; the phrase "Information Item" is shorthand for two common terms; the phrase "Information Item" is
omitted when naming Element Information Items and Attribute omitted when naming Element Information Items and Attribute
Information Items. Information Items.
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[[ Validity? ]] [[ Validity? ]]
Atom constrains the appearance and content of elements and Atom constrains the appearance and content of elements and
attributes; unless otherwise stated, Atom Documents MAY contain other attributes; unless otherwise stated, Atom Documents MAY contain other
Information Items as appropriate. In particular, Comment Information Information Items as appropriate. In particular, Comment Information
Items and Processing Instruction Information Items SHOULD be ignored Items and Processing Instruction Information Items SHOULD be ignored
in the normal processing of an Atom Document. in the normal processing of an Atom Document.
Any element in an Atom Document MAY have an xml:base attribute. XML Any element in an Atom Document MAY have an xml:base attribute. XML
Base [W3C.REC-xmlbase-20010627] processing MUST be applied to any Base [W3C.REC-xmlbase-20010627] processing MUST be applied to any
relative URI reference present in an Atom document. This includes relative reference [RFC2396bis] present in an Atom Document. This
such elements and attributes as specified by Atom itself, as well as includes such elements and attributes as specified by Atom itself, as
those specified by extensions to Atom. well as those specified by extensions to Atom.
Any element in an Atom Document MAY have an xml:lang attribute, whose Any element in an Atom Document MAY have an xml:lang attribute, whose
content indicates the default natural language of the element's content indicates the default natural language of the element's
content. Requirements regarding the content and interpretation of content. Requirements regarding the content and interpretation of
xml:lang are specified in XML 1.0 [W3C.REC-xml-20040204] Section xml:lang are specified in XML 1.0 [W3C.REC-xml-20040204] Section
2.12. 2.12.
[[ discussion of URI escaping and i18n ]] [[ discussion of URI escaping and i18n, IRI ]]
[[ discussion of white space ]] [[ discussion of white space ]]
Atom is extensible. See the section titled 'Extending Atom' later in Atom is extensible. See the section titled 'Extending Atom' later in
this document for a full description of how Atom Documents can be this document for a full description of how Atom Documents can be
extended. extended.
3. Common Atom Constructs 3. Common Atom Constructs
Many of Atom's elements share a few common structures. This section Many of Atom's elements share a few common structures. This section
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the "type" attribute. the "type" attribute.
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, software MAY display it using humans in a readable fashion. Thus, software MAY display it using
normal text rendering techniques such as proportional fonts, normal text rendering techniques such as proportional fonts,
white-space collapsing, and justification. white-space collapsing, and justification.
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
by software that knows HTML. The HTML markup must be encoded; for by software that knows HTML. The HTML markup must be escaped; for
example, "<br>" as "&lt;br>". The HTML markup SHOULD be such that it example, "<br>" as "&lt;br>". The HTML markup SHOULD be such that it
could validly appear directly within an HTML <DIV> element. could validly appear directly within an HTML <DIV> element.
Receiving software which displays the content MAY use the markup to Receiving software which displays the content MAY use the markup to
aid in displaying it. aid in displaying it.
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
MAY contain child elements. The content SHOULD be XHTML text and MAY contain child elements. The content SHOULD be XHTML text and
markup that could validly appear directly within an xhtml:div markup that could validly appear directly within an xhtml:div
element. Receiving software which displays the content MAY use the element. Receiving software which displays the content MAY use the
markup to aid in displaying it. markup to aid in displaying it. Escaped markup is interpreted as a
text representation of markup, and MUST NOT be interpreted as markup
itself.
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. corporation, or similar entity.
Person constructs MAY be extended by namespace-qualified element Person constructs MAY be extended by namespace-qualified element
children. children.
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 a Person construct.
3.2.1 "atom:name" Element 3.2.1 "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. Person constructs MUST contain exactly one "atom:name" the person. Person constructs MUST contain exactly one "atom:name"
element. element.
3.2.2 "atom:uri" Element 3.2.2 "atom:uri" Element
The "atom:uri" element's content conveys a URI associated with the The "atom:uri" element's content conveys a URI 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 a URI [RFC2396]. construct MUST be a URI reference [RFC2396bis].
xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the
atom:uri element's content. atom:uri element's content.
3.2.3 "atom:email" Element 3.2.3 "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 persons. Person constructs MAY contain an associated with the persons. Person constructs MAY contain an
atom:email element, but MUST NOT contain more than one. Its content atom:email element, but MUST NOT contain more than one. Its content
MUST be an e-mail address [RFC2822]. MUST be an e-mail address [RFC2822].
3.3 Date Constructs 3.3 Date Constructs
A Date construct is an element whose content MUST conform to the A Date construct is an element whose content MUST conform to the
date-time BNF rule in [RFC3339]. date-time BNF rule in [RFC3339].
3.4 Service Constructs 3.4 Service Constructs
A Service construct is an empty element that conveys the URI of an A Service construct is an empty element that conveys the URI of an
Atom Publishing Protocol [Atom-protocol] service associated with an Atom Publishing Protocol [Atom-protocol] service associated with an
entry or feed. entry or feed. The type of service is identified by the element
name.
A Service construct has the following attribute: A Service construct has the following attribute:
3.4.1 "href" Attribute 3.4.1 "href" Attribute
The "href" attribute contains the a URI pointing to the endpoint of The "href" attribute contains the a URI pointing to the endpoint of
the service named by the name attribute. atom:service elements MUST the service named by the name attribute. atom:service elements MUST
have a "href" attribute, whose value MUST be a URI. have a "href" attribute, whose value MUST be a URI reference
[RFC2396bis].
xml:base processing MUST be applied to the "href" attribute. xml:base processing MUST be applied to the "href" attribute.
3.5 Link Constructs 3.5 Link Constructs
A Link construct is an empty element that describes a connection from A Link construct is an empty element that describes a connection from
an Atom document to another Web resource. an Atom Document to another Web resource.
3.5.1 "rel" Attribute 3.5.1 "rel" Attribute
The "rel" attribute indicates the type of relationship that the link Link constructs MAY have an optional "rel" attribute that indicates
represents. Link constructs MAY have a rel attribute, whose value the link relation type. If the "rel" attribute is not present, the
MUST be a string, and MUST be one of the following values: link construct MUST be interpreted as if the link relation type is
"alternate", "related". "alternate".
If the "rel" attribute is not present, the link element MUST be rel_attribute = segment-nz-nc / URI
interpreted as if the value "alternate" had been supplied.
The value of "rel" MUST be either a name, which is non-empty and does
not contain any colon (":") characters, or a URI [RFC2396bis]. Note
that use of a relative reference to the "rel" value URI is not
allowed. If a name is given, implementations MUST consider the link
relation type to be equivalent to the same name registered within the
IANA Registry of Link Relations Section 10, and thus the URI that
would be obtained by appending the value of the rel attribute to the
string "http://www.iana.org/assignments/relation/". The value of
"rel" describes the meaning of the link, but does not impose any
behavioral requirements on implementations.
This document defines two initial values for the Registry of Link
Relations:
The value "alternate" signifies that the URI in the value of the href
attribute identifies an alternate version of the resource described
by the containing element.
The value "related" signifies that the URI in the value of the href
attribute identifies a resource to which the resource described by
the containing atom:feed or atom:entry element is related. For
example, the feed for a site which discusses the performance of the
search engine at "http://search.example.com" might contain, as a
child of atom:head:
<link rel="related" href="http://search.example.com/">
An identical link might appear as a child of any atom:entry whose
content contains a discussion of that same search engine.
3.5.2 "type" Attribute 3.5.2 "type" Attribute
The "type" attribute indicates an advisory media type; it MAY be used Link constructs MAY have a type attribute, whose value MUST conform
as a hint to determine the type of the representation which should be to the syntax of a MIME media type [RFC2045].
returned when the URI in the href attribute is dereferenced. Note
that the type attribute does not override the actual media type
returned with the representation.
Link constructs MAY have a type attribute, whose value MUST be a The type attribute's value is an advisory media type; it MAY be used
registered media type [RFC2045]. as a hint to determine the type of the representation which is
expected to be returned when the value of the href attribute is
dereferenced. Note that the type attribute does not override the
actual media type returned with the representation.
3.5.3 "href" Attribute 3.5.3 "href" Attribute
The "href" attribute contains the link's URI. Link constructs MUST The "href" attribute contains the link's URI. Link constructs MUST
have a href attribute, whose value MUST be a URI [RFC2396]. have a href attribute, whose value MUST be a URI reference
[RFC2396bis].
xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the
href attribute's content. href attribute's content.
3.5.4 "hreflang" Attribute 3.5.4 "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 constructs MAY have an hreflang attribute, whose value MUST be a Link constructs MAY have an hreflang attribute, whose value MUST be a
language tag [RFC3066]. language tag [RFC3066].
3.5.5 "title" Attribute 3.5.5 "title" Attribute
The "title" attribute conveys human-readable information about the The "title" attribute conveys human-readable information about the
link. Link constructs MAY have a title attribute. link. Link constructs MAY have a title attribute.
3.5.6 "length" Attribute
The "length" attribute indicates an advisory length of the linked
content in octets; it MAY be used as a hint to determine the content
length of the representation returned when the URI in the href
attribute is dereferenced. Note that the length attribute does not
override the actual content length of the representation as reported
by the underlying protocol.
Link constructs MAY have a length attribute.
3.6 Identity Constructs 3.6 Identity Constructs
An Identity construct is an element whose content conveys a An Identity construct is an element whose content conveys a
permanent, universally unique identifier for the construct's parent. permanent, universally unique identifier for the construct's parent.
Its content MUST be an absolute URI [RFC2396]. Its content MUST be a URI, as defined by [RFC2396bis]. Note that the
definition of "URI" excludes relative references.
When an Atom document is relocated, migrated, syndicated, When an Atom document is relocated, migrated, syndicated,
republished, exported or imported, the content of its Identity republished, exported or imported, the content of its Identity
construct MUST NOT change. Put another way, an Identity construct construct MUST NOT change. Put another way, an Identity construct
pertains to all instantiations of a particular Atom entry or feed; pertains to all instantiations of a particular Atom entry or feed;
revisions retain the same content in their Identity constructs. revisions retain the same content in their Identity constructs.
3.6.1 Dereferencing Identity Constructs 3.6.1 Dereferencing Identity Constructs
The content of an Identity construct MAY be dereferencable (e.g. an The content of an Identity construct MAY be dereferencable (e.g. an
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o Only perform percent-encoding where it is essential. o Only perform percent-encoding where it is essential.
o Use uppercase A-through-F characters when percent-encoding. o Use uppercase A-through-F characters when percent-encoding.
o Prevent dot-segments appearing in paths. o Prevent dot-segments appearing in paths.
o For schemes that define a default authority, use an empty o For schemes that define a default authority, use an empty
authority if the default is desired. authority if the default is desired.
o For schemes that define an empty path to be equivalent to a path o For schemes that define an empty path to be equivalent to a path
of "/", use "/". of "/", use "/".
o For schemes that define a port, use an empty port if the default o For schemes that define a port, use an empty port if the default
is desired. is desired.
o Preserve empty fragment identifiers and queries. o Preserve empty fragment identifiers and queries.
o Ensure that all portions of the URI are utf-8 encoded NFC form o Ensure that all portions of the URI are UTF-8 encoded NFC form
Unicode strings. Unicode strings.
3.6.2 Comparing Identity Constructs 3.6.2 Comparing Identity Constructs
Instances of Identity constructs can be compared to determine whether Instances of Identity constructs can be compared to determine whether
an entry or feed is the same as one seen before. Processors MUST an entry or feed is the same as one seen before. Processors MUST
compare Identity constructs on a character-by-character basis in a compare Identity constructs on a character-by-character basis in a
case-sensitive fashion. case-sensitive fashion.
As a result, two URIs that resolve to the same resource but are not As a result, two URIs that resolve to the same resource but are not
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For example, "http://www.example.org/thing", For example, "http://www.example.org/thing",
"http://www.example.org/Thing", "http://www.EXAMPLE.org/thing" and "http://www.example.org/Thing", "http://www.EXAMPLE.org/thing" and
"HTTP://www.example.org/thing" will all be considered different "HTTP://www.example.org/thing" will all be considered different
identifiers, despite their differences in case. identifiers, despite their differences in case.
Likewise, "http://www.example.com/~bob", Likewise, "http://www.example.com/~bob",
"http://www.example.com/%7ebob" and "http://www.example.com/%7Ebob" "http://www.example.com/%7ebob" and "http://www.example.com/%7Ebob"
will all be considered different identifiers, because URI %-escaping will all be considered different identifiers, because URI %-escaping
is significant for the purposes of comparison. is significant for the purposes of comparison.
3.7 The Category Construct
Category constructs contain information about a category to which an
Atom feed or entry is associated.
3.7.1 The "term" Attribute
The "term" attribute will be a string which identifies the category
within the categorization scheme to which the entry or feed belongs.
Category constructs MUST have a "term" attribute.
3.7.2 The "scheme" Attribute
The is a URI that identifies a categorization scheme. Category
constructs MAY have a "scheme" attribute.
3.7.3 The "label" attribute
The "label" attribute provides a human-readable label that may be
displayed in end-user applications. Category constructs MAY have a
"label" attribute.
4. The "atom:feed" Element 4. 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 first element child MUST be atom:head, associated with the feed. Its first element child MUST be atom:head,
which MAY be followed zero or more atom:entry child elements. which MAY be followed zero or more atom:entry child elements.
4.1 "version" Attribute 4.1 "version" Attribute
atom:feed elements MUST have a "version" attribute whose content atom:feed elements MUST have a "version" attribute whose content
indicates the version of the Atom specification that the feed indicates the version of the Atom specification that the feed
conforms to. The content of this attribute is unstructured text. conforms to. The content of this attribute is unstructured text.
The version identifier for this specification is The version identifier for this specification is
"draft-ietf-atompub-format-03: do not deploy". "draft-ietf-atompub-format-04 : do not deploy".
4.2 The "atom:head" Element 4.2 The "atom:head" Element
The atom:head element acts as a container for metadata about the feed The atom:head element acts as a container for metadata about the feed
itself. itself.
The atom:head element MAY contain any namespace-qualified The atom:head element MAY contain any namespace-qualified
[W3C.REC-xml-names-19990114] elements as children. This [W3C.REC-xml-names-19990114] elements as children. This
specification assigns no significance to the order of appearance of specification assigns no significance to the order of appearance of
the child elements of atom:head. the child elements of atom:head.
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with a rel attribute value of "alternate" that has the same type with a rel attribute value of "alternate" that has the same type
attribute value. attribute value.
If a feed's atom:link element with type="alternate" resolves to an If a feed's atom:link element with type="alternate" resolves to an
HTML document, then that document SHOULD have a autodiscovery link HTML document, then that document SHOULD have a autodiscovery link
element [Atom-autodiscovery] that reflects back to the feed. element [Atom-autodiscovery] that reflects back to the feed.
atom:head elements MAY contain additional atom:link elements beyond atom:head elements MAY contain additional atom:link elements beyond
those described above. those described above.
4.2.3 "atom:introspection" Element 4.2.3 "atom:category" Element
A Category Construct identifying a category with which the feed is
associated. atom:head elements MAY contain any number of
atom:category elements.
4.2.4 "atom:introspection" Element
The "atom:introspection" element is a Service construct that conveys The "atom:introspection" element is a Service construct that conveys
the URI of an introspection file associated with the feed. atom:head the URI of an introspection file associated with the feed. atom:head
elements MUST NOT contain more than one atom:introspection element. elements MUST NOT contain more than one atom:introspection element.
4.2.4 "atom:post" Element 4.2.5 "atom:post" Element
The "atom:post" element is a Service construct that conveys the URI The "atom:post" element is a Service construct that conveys the URI
used to add entries to the feed. atom:head elements MUST NOT contain used to add entries to the feed. atom:head elements MUST NOT contain
more than one atom:post element. more than one atom:post element.
4.2.5 "atom:author" Element 4.2.6 "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
default author of the feed. atom:head elements MUST contain exactly default author of the feed. atom:head elements MUST contain exactly
one atom:author element, UNLESS all of the atom:feed element's child one atom:author element, UNLESS all of the atom:feed element's child
atom:entry elements contain an atom:author element. atom:head atom:entry elements contain an atom:author element. atom:head
elements MUST NOT contain more than one atom:author element. elements MUST NOT contain more than one atom:author element.
[[explain inheritance]] [[explain inheritance]]
4.2.6 "atom:contributor" Element 4.2.7 "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 contributes to the feed. atom:head person or other entity who contributes to the feed. atom:head
elements MAY contain one or more atom:contributor elements. elements MAY contain one or more atom:contributor elements.
4.2.7 "atom:tagline" Element 4.2.8 "atom:tagline" Element
The "atom:tagline" element is a Text construct that conveys a The "atom:tagline" element is a Text construct that conveys a
human-readable description or tagline for the feed. atom:head human-readable description or tagline for the feed. atom:head
elements MAY contain an atom:tagline element, but MUST NOT contain elements MAY contain an atom:tagline element, but MUST NOT contain
more than one. more than one.
4.2.8 "atom:id" Element 4.2.9 "atom:id" Element
The "atom:id" element is an Identity construct that conveys a The "atom:id" element is an Identity construct that conveys a
permanent, universally unique identifier for a feed. atom:head permanent, universally unique identifier for a feed. atom:head
elements MAY contain an atom:id element, but MUST NOT contain more elements MAY contain an atom:id element, but MUST NOT contain more
than one. than one.
4.2.9 "atom:generator" Element 4.2.10 "atom:generator" Element
The "atom:generator" element's content identifies the software agent The "atom:generator" element's content identifies the software agent
used to generate the feed, for debugging and other purposes. used to generate the feed, for debugging and other purposes.
atom:head elements MAY contain an atom:generator element, but MUST atom:head elements MAY contain an atom:generator element, but MUST
NOT contain more than one. NOT contain more than one.
The content of this element, when present, MUST be a string that is a The content of this element, when present, MUST be a string that is a
human-readable name for the generating agent. human-readable name for the generating agent.
The atom:generator element MAY have a "uri" attribute whose value The atom:generator element MAY have a "uri" attribute whose value
MUST be a URI. When dereferenced, that URI SHOULD produce a MUST be a URI reference [RFC2396bis]. When dereferenced, that URI
representation that is relevant to that agent. SHOULD produce a representation that is relevant to that agent.
The atom:generator element MAY have a "version" attribute that The atom:generator element MAY have a "version" attribute that
indicates the version of the generating agent. When present, its indicates the version of the generating agent. When present, its
value is unstructured text. value is unstructured text.
4.2.10 "atom:copyright" Element 4.2.11 "atom:copyright" Element
The "atom:copyright" element is Text construct that conveys a The "atom:copyright" element is Text construct that conveys a
human-readable copyright statement for the feed. atom:head elements human-readable copyright statement for the feed. atom:head elements
MAY contain an atom:copyright element, but MUST NOT contain more than MAY contain an atom:copyright element, but MUST NOT contain more than
one. one.
The atom:copyright element SHOULD NOT be used to convey The atom:copyright element SHOULD NOT be used to convey
machine-readable licensing information. machine-readable licensing information.
[[Is the following paragraph bogus amateur lawyering? The first 4.2.12 "atom:info" Element
paragraph seems sufficient.]]
The atom:copyright element may be assumed to apply to all entries
contained by the feed except those entries which contain
atom:copyright elements. The atom:copyright element MUST, if
present, be considered to apply to the feed as a collection of
entries.
4.2.11 "atom:info" Element
The "atom:info" element is a Text construct that conveys a The "atom:info" element is a Text construct that conveys a
human-readable explanation of the feed format itself. atom:head human-readable explanation of the feed format itself. atom:head
elements MAY contain an atom:info element, but MUST NOT contain more elements MAY contain an atom:info element, but MUST NOT contain more
than one. than one.
The atom:info element SHOULD NOT considered meaningful by processors; The atom:info element SHOULD NOT considered meaningful by processors;
it is a convenience to publishers in certain situations. it is a convenience to publishers in certain situations.
4.2.12 "atom:updated" Element 4.2.13 "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 a change to the feed was made that the recent instant in time when the feed was modified in a way the
publisher wishes to bring to the attention of subscribers. For producer considers significant. Therefore, not all modifications
example, such changes might not include minor adjustments like necessarily result in a changed atom:updated value.
spelling and grammatical corrections.
atom:head elements MUST contain exactly one atom:updated element. atom:head elements MUST contain exactly one atom:updated element.
5. The "atom:entry" Element 5. The "atom:entry" Element
The "atom:entry" element represents an individual entry. This The "atom:entry" element represents an individual entry. This
element can appear as a child of the atom:feed element, or it can element can appear as a child of the atom:feed element, or it can
appear as the document (i.e., top-level) element of a standalone Atom appear as the document (i.e., top-level) element of a standalone Atom
Entry Document. Entry Document.
When appearing in an Atom Entry Document, atom:entry elements MUST When appearing in an Atom Entry Document, atom:entry elements MUST
have a "version" attribute whose content indicates the version of the have a "version" attribute whose content indicates the version of the
Atom specification that the entry conforms to. Atom specification that the entry conforms to.
The version identifier for this specification is The version identifier for this specification is
"draft-ietf-atompub-format-03: do not deploy". "draft-ietf-atompub-format-04 : do not deploy".
The atom:entry element MAY contain any namespace-qualified The atom:entry element MAY contain any namespace-qualified
[W3C.REC-xml-names-19990114] elements as children. This [W3C.REC-xml-names-19990114] elements as children. This
specification assigns no significance to the order of appearance of specification assigns no significance to the order of appearance of
the child elements of atom:entry. 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):
5.1 "atom:title" Element 5.1 "atom:title" Element
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The "atom:title" element is a Text construct that conveys a The "atom:title" element is a Text construct that conveys a
human-readable title for the entry. atom:entry elements MUST have human-readable title for the entry. atom:entry elements MUST have
exactly one "atom:title" element. exactly one "atom:title" element.
5.2 "atom:link" Element 5.2 "atom:link" Element
The "atom:link" element is a Link construct that conveys a URI The "atom:link" element is a Link construct that conveys a URI
associated with the entry. The nature of the relationship as well as associated with the entry. The nature of the relationship as well as
the link itself is determined by the element's content. the link itself is determined by the element's content.
atom:entry elements MUST contain at least one atom:link element with atom:entry elements that contain no child atom:content element MUST
a rel attribute value of "alternate". contain at least one atom:link element with a rel attribute value of
"alternate".
atom:entry elements MUST NOT contain more than one atom:link element atom:entry elements MUST NOT contain more than one atom:link element
with a rel attribute value of "alternate" that has the same type with a rel attribute value of "alternate" that has the same type
attribute value. attribute value.
atom:entry elements MAY contain additional atom:link elements beyond atom:entry elements MAY contain additional atom:link elements beyond
those described above. those described above.
5.3 "atom:edit" Element 5.3 "atom:category" Element
A Category Construct identifying a category with which the entry is
associated. atom:entry elements MAY contain any number of
atom:category elements.
5.4 "atom:edit" Element
The "atom:edit" element is a Service construct that conveys the URI The "atom:edit" element is a Service construct that conveys the URI
used to retrieve and edit the source representation of the entry. used to retrieve and edit the source representation of the entry.
atom:entry elements MUST NOT contain more than one atom:edit element. atom:entry elements MUST NOT contain more than one atom:edit element.
5.4 "atom:author" Element 5.5 "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
default author of the entry. atom:entry elements MUST contain default author of the entry. atom:entry elements MUST contain
exactly one atom:author element, unless, in an Atom Feed Document, exactly one atom:author element, unless, in an Atom Feed Document,
the atom:head element contains an atom:author element itself. the atom:head element contains an atom:author element itself.
atom:entry elements MUST NOT contain more than one atom:author atom:entry elements MUST NOT contain more than one atom:author
element. element.
5.5 "atom:contributor" Element 5.6 "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 contributes to the entry. atom:entry person or other entity who contributes to the entry. atom:entry
elements MAY contain one or more atom:contributor elements. elements MAY contain one or more atom:contributor elements.
5.6 "atom:id" Element 5.7 "atom:host" Element
The "atom:host" element's content conveys a domain name or network
address associated with the entry's origin. atom:entry elements MAY
contain a single atom:host element. Its content MUST be a domain
name [RFC1035], a dotted-decimal IPv4 address [RFC0791], or a
colon-delimited IPv6 address [RFC2460].
5.8 "atom:id" Element
The "atom:id" element is an Identity construct that conveys a The "atom:id" element is an Identity construct that conveys a
permanent, universally unique identifier for an entry. atom:entry permanent, universally unique identifier for an entry. atom:entry
elements MUST contain exactly one atom:id element. elements MUST contain exactly one atom:id element.
5.7 "atom:updated" Element 5.9 "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 a change to the entry was made that the recent instant in time when the entry was modified in a way the
publisher wishes to bring to the attention of subscribers. For producer considers significant. Therefore, not all modifications
example, such changes might not include minor adjustments like necessarily result in a changed atom:updated value.
spelling and grammatical corrections.
atom:entry elements MUST contain exactly one atom:updated element. atom:entry elements MUST contain exactly one atom:updated element.
Publishers MAY change the value of this element over time. Publishers MAY change the value of this element over time.
Processors MAY present entries sorted using this value. Processors Processors MAY present entries sorted using this value. Processors
MAY choose not to present entries until the instant in time specified MAY choose not to present entries until the instant in time specified
in the atom:updated element has passed. in the atom:updated element has passed.
5.8 "atom:published" Element 5.10 "atom:published" Element
The "atom:published" element is a Date construct indicating an The "atom:published" element is a Date construct indicating an
instant in time associated with an event early in the life cycle of instant in time associated with an event early in the life cycle of
the entry. Typically, atom:published will be associated with the the entry. Typically, atom:published will be associated with the
initial creation or first availability of the resource. initial creation or first availability of the resource.
atom:entry elements MAY contain an atom:published element, but MUST atom:entry elements MAY contain an atom:published element, but MUST
NOT contain more than one. NOT contain more than one.
Processors MAY present entries sorted using this value. Processors Processors MAY present entries sorted using this value. Processors
MAY choose not to present entries until the instant in time specified MAY choose not to present entries until the instant in time specified
in the atom:published element has passed. in the atom:published element has passed.
5.9 "atom:summary" Element 5.11 "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 the entry. atom:entry elements MAY summary, abstract or excerpt of the entry. atom:entry elements MAY
contain an atom:summary element, but MUST NOT contain more than one. contain an atom:summary element, but MUST NOT contain more than one.
atom:entry elements MUST contain an atom:summary element in any of atom:entry elements MUST contain an atom:summary element in any of
the following cases: the following cases:
o the atom:entry element contains no atom:content element. o the atom:entry element contains no atom:content element.
o the atom:entry contains an atom:content which has a "src" o the atom:entry contains an atom:content which has a "src"
attribute (and is thus empty). attribute (and is thus empty).
o the atom:entry contains content which is encoded in Base64; i.e. o the atom:entry contains content which is encoded in Base64; i.e.
the "type" attribute of atom:content is a MIME media type the "type" attribute of atom:content is a MIME media type
[RFC2045] and does not begin with "text/" nor end with "+xml". [RFC2045] and does not begin with "text/" nor end with "+xml".
5.10 "atom:content" Element 5.12 "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. atom:entry elements MUST contain zero or one atom:content the entry. atom:entry elements MUST contain zero or one atom:content
elements. elements.
5.10.1 "type" attribute 5.12.1 "type" attribute
atom:content MAY have a "type" attribute, When present, the value MAY atom:content MAY have a "type" attribute, When present, the value MAY
be one of "TEXT", "HTML", or "XHTML". Failing that, it MUST be a be one of "TEXT", "HTML", or "XHTML". Failing that, it MUST be a
MIME media type [RFC2045] in which, to use the terminology of Section MIME media type [RFC2045] in which, to use the terminology of Section
5 of [RFC2045], the top level is a discrete type. If the type 5 of [RFC2045], the top level is a discrete type. If the type
attribute is not provided, software MUST behave as though it were attribute is not provided, software MUST behave as though it were
present with a value of "TEXT". present with a value of "TEXT".
5.10.2 "src" attribute 5.12.2 "src" attribute
atom:content MAY have a "src" attribute, whose value MUST be a URI. atom:content MAY have a "src" attribute, whose value MUST be a URI
If the "src" attribute is present, software MAY use the URI to reference [RFC2396bis]. If the "src" attribute is present, software
retrieve the content. If the "src" attribute is present, MAY use the URI to retrieve the content. If the "src" attribute is
atom:content MUST be empty. That is to say, the content may be present, atom:content MUST be empty. That is to say, the content may
retrievable using "src=" URI, or it may be contained within be retrievable using "src=" URI, or it may be contained within
atom:content, but not both. atom:content, but not both.
If the "src" attribute is present, the "type" attribute MUST be If the "src" attribute is present, the "type" attribute SHOULD be
provided and MUST be a MIME media type [RFC2045], rather than "TEXT", provided and MUST be a MIME media type [RFC2045], rather than "TEXT",
"HTML", or "XHTML". The value is advisory; that is to say, upon "HTML", or "XHTML". The value is advisory; that is to say, upon
dereferencing the URI to retrieve the content, if the server dereferencing the URI to retrieve the content, if the server
providing that content also provides a media type, the providing that content also provides a media type, the
server-provided media type is authoritative. server-provided media type is authoritative.
If the value of type begins with "text/" or ends with "+xml", the If the value of type begins with "text/" or ends with "+xml", the
content SHOULD be local; that is to say, no "src" attribute should be content SHOULD be local; that is to say, no "src" attribute should be
provided. provided.
5.10.3 Processing Model 5.12.3 Processing Model
Software MUST apply the following rules in succession in the order Software MUST apply the following rules in succession in the order
below to ascertain the rules governing the content of "atom:content". below to ascertain the rules governing the content of "atom:content".
1. If the value is "TEXT", the content of atom:content MUST NOT 1. If the value is "TEXT", the content of atom:content 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, software MAY display it humans in a readable fashion. Thus, software MAY display it
using normal text rendering techniques such as proportional using normal text rendering techniques such as proportional
fonts, white-space collapsing, and justification. fonts, white-space collapsing, and justification.
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 by software that knows HTML. The HTML markup must be handling by software that knows HTML. The HTML markup must be
encoded; for example, "<br>" as "&lt;br>". The HTML markup escaped; for example, "<br>" as "&lt;br>". The HTML markup
SHOULD be such that it could validly appear directly within an SHOULD be such that it could validly appear directly within an
HTML <DIV> element. Receiving software which displays the HTML <DIV> element. Receiving software which displays the
content SHOULD use the markup to aid in displaying it. content SHOULD use the 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
MAY contain child elements. The content SHOULD be XHTML text and MAY contain child elements. The content SHOULD be XHTML text and
markup that could validly appear directly within an xhtml:div markup that could validly appear directly within an xhtml:div
element. Receiving software which displays the content SHOULD element. Receiving software which displays the content SHOULD
use the markup to aid in displaying it. use the markup to aid in displaying it. Escaped markup is
interpreted as a text representation of markup, and MUST NOT be
interpreted as markup itself.
4. If the value of "type" ends with "+xml" or "/xml", the content of 4. If the value of "type" ends with "+xml" or "/xml", 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 by software that knows the indicated media type. If for handling by software that knows the indicated media type. If
the "src" attribute is not provided, this would normally mean the "src" attribute is not provided, this would normally mean
that the "atom:content" element would contain a single child that the "atom:content" element would contain a single child
element which would serve as the root element of the XML document element which would serve as the root element of the XML document
of the indicated type. of the indicated type.
5. If the value of "type" begins with "text/" the content of 5. If the value of "type" begins with "text/" the content of
atom:content MUST NOT contain child elements. atom:content MUST NOT contain child elements.
6. For all other values of "type", the content of atom:content MUST 6. For all other values of "type", the content of atom:content MUST
be a valid Base64 encoding [RFC3548], which when decoded SHOULD be a valid Base64 encoding [RFC3548], which when decoded SHOULD
be suitable for handling by software that knows the indicated be suitable for handling by software that knows 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
whitespace, and lines are separated by a single newline (U+000A) whitespace, and lines are separated by a single newline (U+000A)
character, as required by XML. character, as required by XML.
5.11 "atom:copyright" Element 5.13 "atom:copyright" Element
The "atom:copyright" element is a Text construct that conveys a The "atom:copyright" element is a Text construct that conveys a
human-readable copyright statement for the entry. atom:entry human-readable copyright statement for the entry. atom:entry
elements MAY contain an atom:copyright element, but MUST NOT contain elements MAY contain an atom:copyright element, but MUST NOT contain
more than one. more than one.
The atom:copyright element SHOULD NOT be used to convey The atom:copyright element SHOULD NOT be used to convey
machine-readable licensing information. machine-readable licensing information.
If an atom:entry element does not contain an atom:copyright element, If an atom:entry element does not contain an atom:copyright element,
then the atom:copyright element of the containing atom:feed element's then the atom:copyright element of the containing atom:feed element's
atom:head element, if present, should be considered to apply to the atom:head element, if present, should be considered to apply to the
entry. entry.
5.12 "atom:origin" Element 5.14 "atom:head" Element
The "atom:origin" element's content conveys the original source of The atom:head element acts as a container for metadata about the feed
the entry; e.g., the feed where the entry was first published. within which the entry was created.
If the source is an Atom Feed Document, then the content of atom:entry elements MAY contain at most one atom:head element. If
atom:origin MUST be the same, character-for-character, as that of the the atom:head element is present, it SHOULD be the first child
atom:id element in that document's atom:head section (i.e., the XPath element of atom:entry.
expression "/atom:feed/atom:head/atom:id").
The content of this element MUST be a URI. atom:entry elements MAY If an atom:entry is copied into one feed from another feed, then the
contain an atom:origin element, but MUST NOT contain more than one. atom:head element of the source feed SHOULD be inserted into the
atom:entry unless the entry, as copied, already contains an atom:head
element. If the atom:entry already contains an atom:head, then that
atom:head SHOULD be copied without modification.
[[ ... example ... ]]
6. Managing Feed State 6. Managing Feed State
[[ talk about what it means to keep a view of a feed ]] [[ talk about what it means to keep a view of a feed ]]
7. Securing Atom Documents 7. Securing Atom Documents
Because Atom is an XML-based format, existing XML security mechanisms Because Atom is an XML-based format, existing XML security mechanisms
can be used to secure its content. can be used to secure its content.
skipping to change at page 27, line 5 skipping to change at page 27, line 46
Fragment identifiers: As specified for "application/xml" in RFC 3023 Fragment identifiers: As specified for "application/xml" in RFC 3023
[RFC3023], section 5. [RFC3023], section 5.
Base URI: As specified in RFC 3023 [RFC3023], section 6. Base URI: As specified in RFC 3023 [RFC3023], section 6.
Macintosh File Type code: TEXT Macintosh File Type code: TEXT
Person and email address to contact for further information: Mark Person and email address to contact for further information: Mark
Nottingham <mnot@pobox.com> Nottingham <mnot@pobox.com>
Intended usage: COMMON Intended usage: COMMON
Author/Change controller: This specification's author(s). [[update Author/Change controller: This specification's author(s). [[update
upon publication]] upon publication]]
10.1 Registry of Link Relations
This registry is maintained by IANA and initially contains the two
values: "alternate" and "related". New assignments are subject to
IESG Approval, as outlined in [RFC2434]. Requests should be made by
email to IANA, which will then forward the request to the IESG
requesting approval. The request should contain discussion of at
least the following five topics:
o A value for the "rel" attribute that conforms to the syntax rule
given in Section 3.5.1
o Common name for link type.
o Description of link type semantics.
o Expected display characteristics.
o Security considerations.
11. Security Considerations 11. Security Considerations
Atom document can be encrypted and signed using Atom document can be encrypted and signed using
[W3C.REC-xmlenc-core-20021210] and [W3C.REC-xmldsig-core-20020212], [W3C.REC-xmlenc-core-20021210] and [W3C.REC-xmldsig-core-20020212],
respectively, and is subject to the security considerations implied respectively, and is subject to the security considerations implied
by their use. by their use.
12 Normative References 12. References
12.1 Normative References
[Atom-autodiscovery] [Atom-autodiscovery]
Pilgrim, M., "Atom Feed Autodiscovery", work-in-progress, Pilgrim, M., "Atom Feed Autodiscovery", work-in-progress,
August 2004. August 2004.
[Atom-protocol] [Atom-protocol]
Gregorio, J. and R. Sayre, "The Atom Publishing Protocol", Gregorio, J. and R. Sayre, "The Atom Publishing Protocol",
work-in-progress, July 2004. work-in-progress, July 2004.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996. Bodies", RFC 2045, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform [RFC2396bis]
Resource Identifiers (URI): Generic Syntax", RFC 2396, Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
August 1998. Resource Identifier (URI): Generic Syntax", awaiting RFC
number, December 2004.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April [RFC2822] Resnick, P., "Internet Message Format", RFC 2822, April
2001. 2001.
[RFC3023] Murata, M., St. Laurent, S. and D. Kohn, "XML Media [RFC3023] Murata, M., St. Laurent, S. and D. Kohn, "XML Media
Types", RFC 3023, January 2001. Types", RFC 3023, January 2001.
[RFC3066] Alvestrand, H., "Tags for the Identification of [RFC3066] Alvestrand, H., "Tags for the Identification of
Languages", BCP 47, RFC 3066, January 2001. Languages", BCP 47, RFC 3066, January 2001.
skipping to change at page 28, line 30 skipping to change at page 31, line 36
[W3C.REC-xmldsig-core-20020212] [W3C.REC-xmldsig-core-20020212]
Solo, D., Reagle, J. and D. Eastlake, "XML-Signature Solo, D., Reagle, J. and D. Eastlake, "XML-Signature
Syntax and Processing", W3C REC REC-xmldsig-core-20020212, Syntax and Processing", W3C REC REC-xmldsig-core-20020212,
February 2002. February 2002.
[W3C.REC-xmlenc-core-20021210] [W3C.REC-xmlenc-core-20021210]
Reagle, J. and D. Eastlake, "XML Encryption Syntax and Reagle, J. and D. Eastlake, "XML Encryption Syntax and
Processing", W3C REC REC-xmlenc-core-20021210, December Processing", W3C REC REC-xmlenc-core-20021210, December
2002. 2002.
12.2 Informative References
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
URIs
[1] <http://www.imc.org/atom-syntax/index.html> [1] <http://www.imc.org/atom-syntax/index.html>
[2] <http://www.intertwingly.net/wiki/pie/FrontPage> [2] <http://www.intertwingly.net/wiki/pie/FrontPage>
Authors' Addresses Authors' Addresses
Mark Nottingham (editor) Mark Nottingham (editor)
EMail: mnot@pobox.com EMail: mnot@pobox.com
URI: http://www.mnot.net/ URI: http://www.mnot.net/
skipping to change at page 30, line 9 skipping to change at page 34, line 9
The following people contributed to preliminary drafts of this The following people contributed to preliminary drafts of this
document: Tim Bray, Mark Pilgrim, and Sam Ruby. The content and document: Tim Bray, Mark Pilgrim, and Sam Ruby. The content and
concepts within are a product of the Atom community and the Atom concepts within are a product of the Atom community and the Atom
Publishing Format and Protocol Working Group. Publishing Format and Protocol Working Group.
Appendix B. Revision History Appendix B. Revision History
[[ this section should be removed before final publication. ]] [[ this section should be removed before final publication. ]]
-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 -03: Move definition of Link @rel to format spec, restrict
acceptable values (PaceMoveLinkElement, PaceLinkAttrDefaults). acceptable values (PaceMoveLinkElement, PaceLinkAttrDefaults).
Add Service Construct, head/post, head/introspection, entry/edit Add Service Construct, head/post, head/introspection, entry/edit
(PaceServiceElement). (PaceServiceElement).
Add Text Construct, entry/content (PaceReformedContent3). Add Text Construct, entry/content (PaceReformedContent3).
Add entry/published (PaceDatePublished). Add entry/published (PaceDatePublished).
Adjust definition of Identity Construct per chairs' direction to Adjust definition of Identity Construct per chairs' direction to
"fix it." "fix it."
Add Sayre to editors. Add Sayre to editors.
-02: Removed entry/modified, entry/issued, entry/created; added -02: Removed entry/modified, entry/issued, entry/created; added
skipping to change at page 32, line 41 skipping to change at page 36, line 41
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights. except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
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.
 End of changes. 

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