draft-ietf-atompub-format-05.txt		draft-ietf-atompub-format-06.txt
	Network Working Group M. Nottingham, Ed.		Network Working Group M. Nottingham, Ed.
	Internet-Draft		Internet-Draft
	Expires: July 27, 2005 R. Sayre, Ed.		Expires: September 13, 2005 R. Sayre, Ed.
	Boswijck Memex Consulting		Boswijck Memex Consulting
	January 26, 2005		March 12, 2005
	The Atom Syndication Format		The Atom Syndication Format
	draft-ietf-atompub-format-05		draft-ietf-atompub-format-06
	Status of this Memo		Status of this Memo
	By submitting this Internet-Draft, I certify that any applicable		This document is an Internet-Draft and is subject to all provisions
	patent or other IPR claims of which I am aware have been disclosed,		of Section 3 of RFC 3667. By submitting this Internet-Draft, each
	and any of which I become aware will be disclosed, in accordance with		author represents that any applicable patent or other IPR claims of
			which he or she is aware have been or will be disclosed, and any of
			which he or she 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
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	Internet-Drafts.		Internet-Drafts.
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	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 July 27, 2005.		This Internet-Draft will expire on September 13, 2005.
	Copyright Notice		Copyright Notice
	Copyright (C) The Internet Society (2005). All Rights Reserved.		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 . . . . . . . . . . . . . . . . . . . . . . . . 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 Notational Conventions . . . . . . . . . . . . . . . . . . 5
	1.4 Notational Conventions . . . . . . . . . . . . . . . . . . 5
	2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 7		2. Atom Documents . . . . . . . . . . . . . . . . . . . . . . . 7
	3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 9		3. Common Atom Constructs . . . . . . . . . . . . . . . . . . . 9
	3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 9		3.1 Text Constructs . . . . . . . . . . . . . . . . . . . . . 9
	3.1.1 "type" Attribute . . . . . . . . . . . . . . . . . . . 9		3.1.1 "type" Attribute . . . . . . . . . . . . . . . . . . . 9
	3.2 Person Constructs . . . . . . . . . . . . . . . . . . . . 10		3.2 Person Constructs . . . . . . . . . . . . . . . . . . . . 11
	3.2.1 The "atom:name" Element . . . . . . . . . . . . . . . 10		3.2.1 The "atom:name" Element . . . . . . . . . . . . . . . 11
	3.2.2 The "atom:uri" Element . . . . . . . . . . . . . . . . 10		3.2.2 The "atom:uri" Element . . . . . . . . . . . . . . . . 11
	3.2.3 The "atom:email" Element . . . . . . . . . . . . . . . 11		3.2.3 The "atom:email" Element . . . . . . . . . . . . . . . 11
	3.3 Date Constructs . . . . . . . . . . . . . . . . . . . . . 11		3.3 Date Constructs . . . . . . . . . . . . . . . . . . . . . 11
	3.4 Service Constructs . . . . . . . . . . . . . . . . . . . . 11		4. Atom Element Definitions . . . . . . . . . . . . . . . . . . 13
	3.4.1 The "href" Attribute . . . . . . . . . . . . . . . . . 11		4.1 Container Elements . . . . . . . . . . . . . . . . . . . . 13
	3.5 Identity Constructs . . . . . . . . . . . . . . . . . . . 11		4.1.1 The "atom:feed" Element . . . . . . . . . . . . . . . 13
	3.5.1 Dereferencing Identity Constructs . . . . . . . . . . 12		4.1.2 The "atom:entry" Element . . . . . . . . . . . . . . . 14
	3.5.2 Comparing Identity Constructs . . . . . . . . . . . . 12		4.1.3 The "atom:content" Element . . . . . . . . . . . . . . 16
	4. Element Definitions . . . . . . . . . . . . . . . . . . . . 14		4.2 Metadata Elements . . . . . . . . . . . . . . . . . . . . 19
	4.1 The "atom:feed" Element . . . . . . . . . . . . . . . . . 14		4.2.1 The "atom:author" Element . . . . . . . . . . . . . . 19
	4.1.1 The "version" Attribute . . . . . . . . . . . . . . . 14		4.2.2 The "atom:category" Element . . . . . . . . . . . . . 20
	4.2 The "atom:head" Element . . . . . . . . . . . . . . . . . 14		4.2.3 The "atom:contributor" Element . . . . . . . . . . . . 20
	4.2.1 Usage of "atom:head" within "atom:entry" . . . . . . . 16		4.2.4 The "atom:copyright Element . . . . . . . . . . . . . 20
	4.3 The "atom:entry" Element . . . . . . . . . . . . . . . . . 16		4.2.5 The "atom:generator" Element . . . . . . . . . . . . . 21
	4.4 The "atom:title" Element . . . . . . . . . . . . . . . . . 18		4.2.6 The "atom:icon" Element . . . . . . . . . . . . . . . 21
	4.5 The "atom:id" Element . . . . . . . . . . . . . . . . . . 18		4.2.7 The "atom:id" Element . . . . . . . . . . . . . . . . 21
	4.6 The "atom:link" Element . . . . . . . . . . . . . . . . . 18		4.2.8 The "atom:image" Element . . . . . . . . . . . . . . . 23
	4.6.1 The "href" Attribute . . . . . . . . . . . . . . . . . 19		4.2.9 The "atom:link" Element . . . . . . . . . . . . . . . 23
	4.6.2 The "rel" Attribute . . . . . . . . . . . . . . . . . 19		4.2.10 The "atom:published" Element . . . . . . . . . . . . 26
	4.6.3 The "type" Attribute . . . . . . . . . . . . . . . . . 20		4.2.11 The "atom:source-feed" Element . . . . . . . . . . . 26
	4.6.4 The "hreflang" Attribute . . . . . . . . . . . . . . . 20		4.2.12 The "atom:subtitle" Element . . . . . . . . . . . . 26
	4.6.5 The "title" Attribute . . . . . . . . . . . . . . . . 20		4.2.13 The "atom:summary" Element . . . . . . . . . . . . . 27
	4.6.6 The "length" Attribute . . . . . . . . . . . . . . . . 20		4.2.14 The "atom:title" Element . . . . . . . . . . . . . . 27
	4.7 The "atom:updated" Element . . . . . . . . . . . . . . . . 20		4.2.15 The "atom:updated" Element . . . . . . . . . . . . . 27
	4.8 The "atom:published" Element . . . . . . . . . . . . . . . 21		5. Securing Atom Documents . . . . . . . . . . . . . . . . . . 28
	4.9 The "atom:author" Element . . . . . . . . . . . . . . . . 21		5.1 Digital Signatures . . . . . . . . . . . . . . . . . . . . 28
	4.10 The "atom:contributor" Element . . . . . . . . . . . . . 21		5.2 Encryption . . . . . . . . . . . . . . . . . . . . . . . . 28
	4.11 The "atom:host" Element . . . . . . . . . . . . . . . . 21		6. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 29
	4.12 The "atom:copyright" Element . . . . . . . . . . . . . . 21		6.1 Extensions From Non-Atom Vocabularies . . . . . . . . . . 29
	4.13 The "atom:category" Element . . . . . . . . . . . . . . 22		6.2 Extensions To the Atom Vocabulary . . . . . . . . . . . . 29
	4.13.1 The "term" Attribute . . . . . . . . . . . . . . . . 22		6.3 Software Processing of Foreign Markup . . . . . . . . . . 29
	4.13.2 The "scheme" Attribute . . . . . . . . . . . . . . . 22		6.4 Extension Elements . . . . . . . . . . . . . . . . . . . . 29
	4.13.3 The "label" attribute . . . . . . . . . . . . . . . 22		6.4.1 Simple Extension Elements . . . . . . . . . . . . . . 30
	4.14 The "atom:summary" Element . . . . . . . . . . . . . . . 22		6.4.2 Structured Extension Elements . . . . . . . . . . . . 30
	4.15 The "atom:content" Element . . . . . . . . . . . . . . . 23		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . 31
	4.15.1 The "type" attribute . . . . . . . . . . . . . . . . 23		7.1 Registry of Link Relations . . . . . . . . . . . . . . . . 31
	4.15.2 The "src" attribute . . . . . . . . . . . . . . . . 23		8. Security Considerations . . . . . . . . . . . . . . . . . . 33
	4.15.3 Processing Model . . . . . . . . . . . . . . . . . . 24		8.1 HTML and XHTML Content . . . . . . . . . . . . . . . . . . 33
	4.16 The "atom:introspection" Element . . . . . . . . . . . . 25		8.2 URIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
	4.17 The "atom:post" Element . . . . . . . . . . . . . . . . 25		8.3 IRIs . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
	4.18 The "atom:edit" Element . . . . . . . . . . . . . . . . 25		8.4 Encryption and Signing . . . . . . . . . . . . . . . . . . 33
	4.19 The "atom:tagline" Element . . . . . . . . . . . . . . . 25		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
	4.20 The "atom:generator" Element . . . . . . . . . . . . . . 25		9.1 Normative References . . . . . . . . . . . . . . . . . . . 34
	4.21 The "atom:info" Element . . . . . . . . . . . . . . . . 26		9.2 Informative References . . . . . . . . . . . . . . . . . . 35
	5. Managing Feed State . . . . . . . . . . . . . . . . . . . . 27
	6. Securing Atom Documents . . . . . . . . . . . . . . . . . . 28
	6.1 Digital Signatures . . . . . . . . . . . . . . . . . . . . 28
	6.2 Encryption . . . . . . . . . . . . . . . . . . . . . . . . 28
	7. Embedding Atom in Other Formats . . . . . . . . . . . . . . 29
	8. Extending Atom . . . . . . . . . . . . . . . . . . . . . . . 30
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . 31
	9.1 Registry of Link Relations . . . . . . . . . . . . . . . . 31
	10. Security Considerations . . . . . . . . . . . . . . . . . . 33
	11. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
	11.1 Normative References . . . . . . . . . . . . . . . . . . . 34
	11.2 Informative References . . . . . . . . . . . . . . . . . . 35
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 36		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 36
	A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 37		A. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 37
	B. Collected RELAX NG Compact Schema . . . . . . . . . . . . . 38		B. Collected RELAX NG Compact Schema . . . . . . . . . . . . . 38
	C. Revision History . . . . . . . . . . . . . . . . . . . . . . 45		C. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 45
	Intellectual Property and Copyright Statements . . . . . . . 47		Intellectual Property and Copyright Statements . . . . . . . 48
	1. Introduction		1. Introduction
	Atom is an XML-based document format which describes lists of related		Atom is an XML-based document format that describes lists of related
	information known as "feeds". Feeds are composed of a number of		information known as "feeds". Feeds are composed of a number of
	items, known as "entries", each with an extensible set of attached		items, known as "entries", each with an extensible set of attached
	metadata. For example, each entry has a title.		metadata. For example, each entry has a title.
	The primary use case that Atom addresses is the syndication of Web		The primary use case that Atom addresses is the syndication of Web
	content such as Weblogs and news headlines to Web sites as well as		content such as Weblogs and news headlines to Web sites as well as
	directly to user agents. However, nothing precludes it from being		directly to user agents. 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
	can be found in the Atom Protocol specification [Atom-protocol].
	[[ more motivation / design principles ]]
	1.1 Editorial Notes		1.1 Editorial Notes
	The Atom format is a work-in-progress, and this draft is both		The Atom format is a work-in-progress, and this draft is both
	incomplete and likely to change rapidly. As a result, THE FORMAT		incomplete and likely to change rapidly. As a result, THE FORMAT
	DESCRIBED BY THIS DRAFT SHOULD NOT BE DEPLOYED, either in production		DESCRIBED BY THIS DRAFT SHOULD NOT BE DEPLOYED, either in production
	systems or in any non-experimental fashion on the Internet.		systems or in any non-experimental fashion on the Internet.
	Discussion of this draft happens in two fora;		Discussion of this draft happens in two fora;
	The mailing list [1]		The mailing list <http://www.imc.org/atom-syntax/index.html>
	The Atom Wiki Web site [2]		The Atom Wiki Web site
			<http://www.intertwingly.net/wiki/pie/FrontPage>
	Active development takes place on the mailing list, while the Wiki is		Active development takes place on the mailing list, while the Wiki is
	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
	marked [[like this]] indicate where additional text is likely to be
	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-05:do not deploy"		<feed
	xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-05">		xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-06">
	<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>
	<entry>		<entry>
	<title>Atom-Powered Robots Run Amok</title>		<title>Atom-Powered Robots Run Amok</title>
	<link href="http://example.org/2003/12/13/atom03"/>		<link href="http://example.org/2003/12/13/atom03"/>
	<id>vemmi://example.org/2003/32397</id>		<id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
	<updated>2003-12-13T18:30:02Z</updated>		<updated>2003-12-13T18:30:02Z</updated>
	</entry>		</entry>
	</feed>		</feed>
	1.3 Conformance		[[anchor4: Ask yourself: is the example atom:entry valid?]]
	[[ talk about atom documents and atom consumers, and how requirements		1.3 Notational Conventions
	are placed on them ]]
	1.4 Notational Conventions		This specification describes conformance in terms of two kinds of
			artefacts; Atom Feed Documents and Atom Entry documents.
			Additionally, it places some requirements on Atom Processors.
	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], as
			scoped to those conformance targets.
	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 names. It uses the following
	following namespace prefixes for the indicated namespace URIs;		namespace prefixes for the indicated namespace URIs;
	"atom": http://purl.org/atom/ns#draft-ietf-atompub-format-05		"atom": http://purl.org/atom/ns#draft-ietf-atompub-format-06
	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-20040204]. However, this specification uses a
	shorthand for two common terms; the phrase "Information Item" is		shorthand for two common terms; the phrase "Information Item" is
	omitted when naming Element Information Items and Attribute		omitted when naming Element Information Items and Attribute
	Information Items.		Information Items.
	Therefore, when this specification uses the term "element," it is		Therefore, when this specification uses the term "element," it is
	referring to an Element Information Item in Infoset terms. Likewise,		referring to an Element Information Item in Infoset terms. Likewise,
	when it uses the term "attribute," it is referring to an Attribute		when it uses the term "attribute," it is referring to an Attribute
	Information Item.		Information Item.
	Some sections of this specification are illustrated with fragments of		Some sections of this specification are illustrated with fragments of
	skipping to change at page 7, line 12		skipping to change at page 7, line 12
	text of this specification provides the definition of conformance. A		text of this specification provides the definition of conformance. A
	collected schema appears in an informative appendix.		collected schema appears in an informative appendix.
	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 document element is atom:feed.		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 document element is atom:entry.		the context of an Atom Feed. Its root is the atom:entry element.
	namespace atom =		namespace
	"http://purl.org/atom/ns#draft-ietf-atompub-format-05"		atom ="http://purl.org/atom/ns#draft-ietf-atompub-format-06"
	start = atomFeed | atomEntry		start = atomFeed | atomEntry
	Both kinds of Atom documents are specified in terms of the XML		Both kinds of Atom documents are specified in terms of the XML
	Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204] and		Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204] and
	identified with the "application/atom+xml" media type. Atom		identified with the "application/atom+xml" media type. Atom
	Documents MUST be well-formed XML.		Documents MUST be well-formed XML.
	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 reference [RFC3986] present in an Atom Document. This		relative reference [RFC3987] present in an Atom Document. This
	includes such elements and attributes as specified by Atom itself, as		includes such elements and attributes as specified by Atom itself, as
	well 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 natural language of the element's content.		content indicates the natural language for the element and its
			children. The language context is only significant for elements and
			attributes declared to be "language-sensitive" by this specification.
	Requirements regarding the content and interpretation of xml:lang are		Requirements regarding the content and interpretation of xml:lang are
	specified in XML 1.0 [W3C.REC-xml-20040204] Section 2.12.		specified in XML 1.0 [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 }?
	[[ discussion of URI escaping and i18n, IRI ]]		Atom allows the use of IRIs [RFC3987], rather than only URIs
			[RFC3986]. For resolution, IRIs can easily be converted to URIs.
			When comparing IRIs serving as Identity Constructs, they MUST NOT be
			converted to URIs. Please note that by definition, every URI is an
			IRI, so any URI can be used where an IRI is needed.
	[[ discussion of white space ]]		[[anchor7: discussion of white space]]
	Atom is extensible. See the section titled 'Extending Atom' later in		Atom is an extensible format. See the section titled 'Extending
	this document for a full description of how Atom Documents can be		Atom' later in this document for a full description of how Atom
	extended.		Documents can be extended.
			Atom Processors MAY keep state (e.g., metadata in atom:feed, entries)
			sourced from Atom Feed Documents and combine them with other Atom
			Feed Documents, in order to facilitate a contiguous view of the
			contents of a feed. The manner in which Atom Feed Documents are
			combined in order to reconstruct a feed (e.g., updating entries and
			metadata, dealing with missing entries) is out of the scope of this
			specification, but may be defined by an extension to Atom.
	3. Common Atom Constructs		3. Common Atom Constructs
	Many of Atom's elements share a few common structures. This section		Many of Atom's elements share a few common structures. This section
	defines a few such structures and their requirements for convenient		defines a few such structures and their requirements for convenient
	reference by the appropriate element definitions.		reference by the appropriate element definitions.
	When an element is identified as being a particular kind of		When an element is identified as being a particular kind of
	construct, it inherits the corresponding requirements from that		construct, it inherits the corresponding requirements from that
	construct's definition in this section.		construct's definition in this section.
	3.1 Text Constructs		3.1 Text Constructs
	A Text construct contains human readable text, usually in fairly		A Text construct contains human readable text, usually in small
	small quantities.		quantities. Except for the "type" attribute, 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" },
	(text|anyElement)*		(text|anyElement)*
	atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct		atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct
	3.1.1 "type" Attribute		3.1.1 "type" Attribute
	Text constructs MAY have a "type" attribute. When present, the value		Text constructs MAY have a "type" attribute. [[anchor11: Some feel
	MUST be one of "TEXT", "HTML" or "XHTML". If the "type" attribute is		type attributes with different allowable values in different elements
	not provided, software MUST behave as though it were present with a		is confusing.]]. When present, the value MUST be one of "text",
	value of "TEXT".		"html" or "xhtml". If the "type" attribute is not provided, Atom
			Processors MUST behave as though it were present with a value of
			"text".
	Note that MIME media types [RFC2045] are not acceptable values for		Note that MIME media types [RFC2045] are not acceptable values for
	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, Atom Processors MAY display it
	normal text rendering techniques such as proportional fonts,		using 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 escaped; for		as HTML [W3C.REC-html401-19991224]. Any markup within MUST be
	example, "<br>" as "&lt;br>". The HTML markup SHOULD be such that it		escaped; for example, "<br>" as "&lt;br>". HTML markup within SHOULD
	could validly appear directly within an HTML <DIV> element.		be such that it could validly appear directly within an HTML <DIV>
	Receiving software which displays the content MAY use the markup to		element, after unescaping. Atom Processors that display such content
	aid in displaying it.		MAY use markup to aid in its display.
	[[example atom entry w/ escaped markup]]		[[anchor12: example atom entry w/ escaped markup]]
	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		MUST be a single XHTML div element [W3C.REC-xhtml-basic-20001219].
	markup that could validly appear directly within an xhtml:div		The XHTML div MUST contain XHTML text and markup that could validly
	element. Receiving software which displays the content MAY use the		appear within an XHTML div element. The XHTML div element itself
	markup to aid in displaying it. Escaped markup is interpreted as a		MUST NOT be considered part of the content. Atom Processors which
	text representation of markup, and MUST NOT be interpreted as markup		display the content MAY use the markup to aid in displaying it.
	itself.		Escaped markup is interpreted as a text representation of markup, and
			MUST NOT be interpreted as markup itself.
			Example:
			...
			<summary type="xhtml">
			<div xmlns="http://www.w3.org/1999/xhtml">
			This is <b>XHTML</b> content.
			</div>
			</summary>
			...
			<summary type="xhtml">
			<xhtml:div xmlns:xhtml="http://www.w3.org/1999/xhtml">
			This is <xhtml:b>XHTML</xhtml:b> content.
			</xhtml:div>
			</summary>
			...
			The following example assumes that the XHTML namespace has been bound
			to the "xh" prefix earlier in the document:
			...
			<summary type="xhtml">
			<xh:div>
			This is <xh:b>XHTML</xh:b> content.
			</xh:div>
			</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.		corporation, or similar entity (hereafter, 'person').
	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 in a Person construct.		of the child elements in a Person construct.
	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 }?)
	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. Person constructs MUST contain exactly one "atom:name"		the person. The content of atom:name is language sensitive. Person
	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 a URI 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 a URI reference [RFC3986].		construct MUST be an IRI reference [RFC3987].
	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 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 persons. Person constructs MAY contain an		associated with the person. Person constructs MAY contain an
	atom:email element, but MUST NOT contain more than one. Its content		atom:email element, but MUST NOT contain more than one. Its content
	MUST be an e-mail address [RFC2822].		MUST conform to the addr-spec BNF rule 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 BNF rule in [RFC3339].		date-time BNF rule in [RFC3339]. I.e., the content of this element
			matches this regular expression:
	atomDateConstruct =
	atomCommonAttributes,
	xsd:dateTime
	3.4 Service Constructs
	A Service construct is an empty element that conveys the URI of an
	Atom Publishing Protocol [Atom-protocol] service associated with an
	entry or feed.
	atomServiceConstruct =
	atomCommonAttributes,
	attribute href { atomUri }
	3.4.1 The "href" Attribute
	The "href" attribute contains the a URI of the service. atom:service
	elements MUST have a "href" attribute, whose value MUST be a URI
	reference [RFC3986].
	xml:base processing MUST be applied to the "href" attribute.
	3.5 Identity Constructs
	An Identity construct is an element whose content conveys a		[0-9]{8}T[0-9]{2}:[0-9]{2}:[0-9]{2}(\.[0-9]+)
	permanent, universally unique identifier for the construct's parent.		?(Z|[\+\-][0-9]{2}:[0-9]{2})
	Its content MUST be a URI, as defined by [RFC3986]. Note that the
	definition of "URI" excludes relative references.
	When an Atom document is relocated, migrated, syndicated,		As a result, the date values conform to the following specifications:
	republished, exported or imported, the content of its Identity		[RFC3339], [W3C.REC-xmlschema-2-20041028],
	construct MUST NOT change. Put another way, an Identity construct		[W3C.NOTE-datetime-19980827], and [ISO.8601.1988].
	pertains to all instantiations of a particular Atom entry or feed;
	revisions retain the same content in their Identity constructs.
	atomIdentityConstruct =		atomDateConstruct =
	atomCommonAttributes,		atomCommonAttributes,
	(atomUri)		xsd:dateTime
	3.5.1 Dereferencing Identity Constructs
	The content of an Identity construct MAY be dereferencable (e.g. an
	HTTP URI). However, processors MUST NOT assume it to be
	dereferencable.
	The content of an Identity construct MUST be created in a way that
	assures uniqueness, and it is suggested that the Identity construct
	be stored along with the associated resource.
	Because of the risk of confusion between URIs that would be
	equivalent if dereferenced, the following normalization strategy is
	strongly encouraged when generating Identity constructs:
	o Provide the scheme in lowercase characters.
	o Provide the host, if any, in lowercase characters.
	o Only perform percent-encoding where it is essential.
	o Use uppercase A-through-F characters when percent-encoding.
	o Prevent dot-segments appearing in paths.
	o For schemes that define a default authority, use an empty
	authority if the default is desired.
	o For schemes that define an empty path to be equivalent to a path
	of "/", use "/".
	o For schemes that define a port, use an empty port if the default
	is desired.
	o Preserve empty fragment identifiers and queries.
	o Ensure that all portions of the URI are UTF-8 encoded NFC form
	Unicode strings.
	3.5.2 Comparing Identity Constructs
	Instances of Identity constructs can be compared to determine whether
	an entry or feed is the same as one seen before. Processors MUST
	compare Identity constructs on a character-by-character basis in a
	case-sensitive fashion.
	As a result, two URIs that resolve to the same resource but are not
	character-for-character identical will be considered different for
	the purposes of Identifier comparison.
	For example, "http://www.example.org/thing",		4. Atom Element Definitions
	"http://www.example.org/Thing", "http://www.EXAMPLE.org/thing" and
	"HTTP://www.example.org/thing" will all be considered different
	identifiers, despite their differences in case.
	Likewise, "http://www.example.com/~bob",		4.1 Container Elements
	"http://www.example.com/%7ebob" and "http://www.example.com/%7Ebob"
	will all be considered different identifiers, because URI %-escaping
	is significant for the purposes of comparison.
	4. Element Definitions		4.1.1 The "atom:feed" Element
	4.1 The "atom:feed" Element		[[anchor21: Substantially changed from format-05, review carefully.]]
	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 element children consist of one or
	which MAY be followed zero or more atom:entry child elements.