RFC
TOC

Network Working Group | M Nottingham, Editor
INTERNET DRAFT | July 2004
<draft-ietf-atompub-format-01> |
Category: Informational |
Expires: January 2005 |

The Atom Syndication Format
draft-ietf-atompub-format-01

# Status of this Memo

By submitting this Internet-Draft, I certify that any applicable 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 RFC 3668.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress".

The list of current Internet-Drafts can be accessed at <http://www.ietf.org/ietf/1id-abstracts.txt>.

The list of Internet-Draft Shadow Directories can be accessed at <http://www.ietf.org/shadow.html>.

This Internet-Draft will expire in January 2005.

# Copyright Notice

Copyright (C) The Internet Society (2004). All Rights Reserved.

# Abstract

This specification describes Atom, an XML-based Web content and metadata syndication format.

RFC
TOC

# Table of Contents

1 Introduction
1.1 Editorial Notes
1.2 Example
1.3 Conformance
1.4 Notational Conventions
2 Atom Documents
3 Common Atom Constructs
3.1 Content Constructs
3.1.1 "type" Attribute
3.1.2 "mode" Attribute
3.2 Person Constructs
3.2.1 "atom:name" Element
3.2.2 "atom:uri" Element
3.2.3 "atom:email" Element
3.3 Date Constructs
3.4 Link Constructs
3.4.1 "rel" Attribute
3.4.2 "type" Attribute
3.4.3 "href" Attribute
3.4.4 "hreflang" Attribute
3.4.5 "title" Attribute
4 The "atom:feed" Element
4.1 "version" Attribute
4.2 The "atom:head" Element
4.2.1 "atom:title" Element
4.2.2 "atom:link" Element
4.2.3 "atom:author" Element
4.2.4 "atom:contributor" Element
4.2.5 "atom:tagline" Element
4.2.6 "atom:id" Element
4.2.7 "atom:generator" Element
4.2.8 "atom:copyright" Element
4.2.9 "atom:info" Element
4.2.10 "atom:modified" Element
5 The "atom:entry" Element
5.1 "atom:title" Element
5.2 "atom:link" Element
5.3 "atom:author" Element
5.4 "atom:contributor" Element
5.5 "atom:id" Element
5.6 "atom:modified" Element
5.7 "atom:issued" Element
5.8 "atom:created" Element
5.9 "atom:summary" Element
5.10 "atom:content" Element
5.11 "atom:copyright" Element
5.12 "atom:origin" Element
6 Managing Feed State
7 Embedding Atom in Other Formats
8 Extending Atom
9 IANA Considerations
10 Security Considerations
11 Normative References
§ Author's Address
A Contributors
B Revision History
§ Intellectual Property and Copyright Statements

TOC

# 1 Introduction

Atom is an XML-based document format intended to allow lists of related information, known as "feeds", to be synchronised between publishers and consumers. Feeds are composed of a number of items, known as "entries", each with an extensible set of attached metadata. For example, each entry has a title.

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 directly to user agents. However, nothing precludes it from being used for other purposes and kinds of content.

Details of comunication protocols between software agents using Atom can be found in the Atom Protocol specification [Atom-protocol].

[[ more motivation / design principles ]]

## 1.1 Editorial Notes

The Atom format is a work-in-progress, and this draft is both incomplete and likely to change rapidly. As a result, THE FORMAT DESCRIBED BY THIS DRAFT SHOULD NOT BE DEPLOYED, either in production systems or in any non-experimental fashion on the Internet.

Discussion of this draft happens in two fora;

  The mailing list <http://www.imc.org/atom-syntax/index.html>
  The Atom Wiki Web site <http://www.intertwingly.net/wiki/pie/FrontPage>

Active development takes place on the mailing list, while the Wiki is 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

A minimal, single-entry Atom Feed Document:

    <?xml version="1.0" encoding="utf-8"?>
    <feed version="draft-ietf-atompub-format-01: do not deploy"
     xmlns="http://purl.org/atom/ns#draft-ietf-atompub-format-01">
      <head>
        <title>Example Feed</title>
        <link rel="alternate" type="text/html"
         href="http://example.org/index.atom"/>
        <modified>2003-12-13T18:30:02Z</modified>
        <author>
          <name>John Doe</name>
        </author>
        </head>
      <entry>
        <title>Atom-Powered Robots Run Amok</title>
        <link rel="alternate" type="text/html"
         href="http://example.org/2003/12/13/atom03"/>
        <id>tag:example.org,2003:3.2397</id>
        <issued>2003-12-13T08:29:29-04:00</issued>
        <modified>2003-12-13T18:30:02Z</modified>
      </entry>
    </feed>

## 1.3 Conformance

[[ talk about atom documents and atom consumers, and how requirements are placed on them ]]

## 1.4 Notational Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

This specification uses XML Namespaces [W3C.REC-xml-names-19990114] to uniquely identify XML elements and attribute names. It uses the following namespace prefixes for the indicated namespace URIs;

"atom":
  http://purl.org/atom/ns#draft-ietf-atompub-format-01

Note that the choice of any namespace prefix is arbitrary and not semantically significant.

Atom is specified using terms from the XML Infoset [W3C.REC-xml-infoset-20011024]. However, this specification uses a shorthand for two common terms; the phrase "Information Item" is omitted when naming Element Information Items and Attribute Information Items.

Therefore, when this specification uses the term "element," it is refering to an Element Information Item in Infoset terms. Likewise, when it uses the term "attribute," it is refering to an Attribute Information Item.

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# 2 Atom Documents

This specification describes two kinds of Atom Documents; Atom Feed Documents and Atom Entry Documents.

An Atom Feed Document is a representation of an Atom feed, including metadata about the feed, and some or all of the entries associated with it. Its document element is atom:feed.

An Atom Entry Document represents exactly one Atom Entry, outside of the context of an Atom Feed. Its document element is atom:entry.

Both kinds of Atom documents are specified in terms of the XML Information Set, serialised as XML 1.0 [W3C.REC-xml-20040204] and identified with the "application/atom+xml" media type. Atom Documents MUST be well-formed XML.

[[ Validity? ]]

Atom constrains the appearance and content of elements and attributes; unless otherwise stated, Atom Documents MAY contain other Information Items as appropriate. In particular, Comment Information Items and Processing Instruction Information Items SHOULD be ignored in the normal processing of an Atom Document.

Any element in an Atom Document MAY have an xml:base attribute. XML Base [W3C.REC-xmlbase-20010627] processing MUST be applied to any relative URI reference present in an Atom document. This includes such elements and attributes as specified by Atom itself, as well as those specified by extensions to Atom.

Any element in an Atom Document MAY have an xml:lang attribute, whose content indicates the default natural language of the element's content. Requirements regarding the content and interpretation of xml:lang are specified in XML 1.0 [W3C.REC-xml-20040204] Section 2.12. For convenience, the most important are summarised here:

  The content of this attribute must be a language tag [RFC3066] or an empty string (e.g., xml:lang=""), which indicates that there is no language information available.
  If an element does not have an xml:lang element, the first xml:lang attribute in its ancestors indicates the natural language of its content.

[[ feedback as to whether this listing is helpful or not would be appreciated; re-stating the requirements of other specifications is tricky. ]]

[[ discussion of URI escaping and i18n ]]

[[ discussion of white space ]]

Atom is extensible. See the section titled 'Extending Atom' later in this document for a full description of how Atom Documents can be extended.

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# 3 Common Atom Constructs

Many of Atom's elements share a few common structures. This section defines a few such structures and their requirements, for convenient reference by the appropriate element definitions.

When an element is identified as being a particular kind of construct, it inherits the corresponding requirements from that construct's definition in this section.

## 3.1 Content Constructs

A Content construct is an element with arbitrary child content, whose properties are described by the following attributes:

### 3.1.1 "type" Attribute

Content constructs MAY have a "type" attribute, whose value indicates the media type of the content. When present, this attribute's value MUST be a media type [RFC2045]. If this attribute is not present, processors MUST behave as if it were present with a value of "text/plain".

### 3.1.2 "mode" Attribute

Content constructs MAY have a "mode" attribute, whose value indicates the method used to encode the content. When present, this attribute's value MUST be listed below. If not present, its value MUST be considered to be "xml".

"xml":
  A mode attribute with the value "xml" indicates that the element's content is inline xml (for example, namespace-qualified XHTML).
"escaped":
  A mode attribute with the value "escaped" indicates that the element's content is escaped, as defined in [W3C.REC-xml-20040204] (section 4.6). Processors MUST unescape the element's content before considering it as content of the indicated media type.
"base64":
  A mode attribute with the value "base64" indicates that the element's content is base64-encoded [RFC2045]. Processors MUST decode the element's content before considering it as content of the the indicated media type.

## 3.2 Person Constructs

A Person construct is an element that describes a person, corporation, or similar entity. It has the following children:

### 3.2.1 "atom:name" Element

The "atom:name" element's content conveys a human-readable name for the person. Person constructs MUST contain exactly one "atom:name" element, whose content is unstructured text.

### 3.2.2 "atom:uri" Element

The "atom:uri" element's content conveys a URI associated with the person. Person constructs MAY contain an atom:uri element, but MUST NOT contain more than one. The content of atom:uri in a Person construct MUST be a URI [RFC2396].

xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the atom:uri element's content.

### 3.2.3 "atom:email" Element

The "atom:email" element's content conveys an e-mail address associated with the persons. Person constructs MAY contain an atom:email element, but MUST NOT contain more than one. Its content MUST be an e-mail address [RFC2822].

Person constructs MAY be extended by namespace-qualified element children.

Ordering of the element children of Person constructs MUST NOT be considered significant.

## 3.3 Date Constructs

A Date construct is an element whose content is a W3C Date-Time string [W3C.NOTE-datetime-19980827].

## 3.4 Link Constructs

A Link construct is an element that MUST NOT have any child content, and has the following attributes:

### 3.4.1 "rel" Attribute

The "rel" attribute indicates the type of relationship that the link represents. Link constructs MUST have a rel attribute, whose value MUST be one of the values enumerated in the Atom Protocol specification [Atom-protocol].

### 3.4.2 "type" Attribute

The "type" attribute indicates an advisory media type; it MAY be used as a hint to determine the type of the representation which should be 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 MUST have a type attribute, whose value MUST be a media type [RFC2045].

### 3.4.3 "href" Attribute

The "href" attribute contains the link's URI. Link constructs MUST have a href attribute, whose value MUST be a URI [RFC2396].

xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the href attribute's content.

### 3.4.4 "hreflang" Attribute

The "hreflang" attribute's content describes the language of the resource pointed to by the href attribute. When used together with the rel="alternate", it implies a translated version of the entry. Link constructs MAY have an hreflang attribute, whose value MUST be a language tag [RFC3066].

### 3.4.5 "title" Attribute

The "title" attribute conveys human-readable information about the link. Link constructs MAY have a title attribute, whose value is unstructured text.

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# 4 The "atom:feed" Element

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 associated with the feed. Its first element child MUST be atom:head, which MAY be followed zero or more atom:entry child elements.

## 4.1 "version" Attribute

atom:feed elements MUST have a "version" attribute whose content indicates the version of the Atom specification that the feed conforms to. The content of this attribute is unstructured text.

The version identifier for this specification is "draft-ietf-atompub-format-01: do not deploy".

## 4.2 The "atom:head" Element

The atom:head element acts as a container for metadata about the feed itself.

The atom:head element MAY contain any namespace-qualified [W3C.REC-xml-names-19990114] elements as children. Ordering of the element children of atom:head element MUST NOT be considered significant.

The following child elements are defined by this specification (note that the presence of some of these elements is required):

### 4.2.1 "atom:title" Element

The "atom:title" element is a Content construct that conveys a human-readable title for the feed. atom:head elements MUST contain exactly one atom:title element.

### 4.2.2 "atom:link" Element

The "atom:link" element is a Link construct that conveys a URI associated with the feed. The nature of the relationship as well as the link itself is determined by the element's content.

atom:head elements MUST contain at least one atom:link element with a rel attribute value of "alternate".

atom:head elements MUST NOT contain more than one atom:link element with a rel attribute value of "alternate" that has the same type attribute value.

atom:head elements MAY contain additional atom:link elements beyond those described above.

### 4.2.3 "atom:author" Element

The "atom:author" element is a Person construct that indicates the default author of the feed. atom:head elements MUST contain exactly one atom:author element, UNLESS all of the atom:feed element's child atom:entry elements contain an atom:author element. atom:head elements MUST NOT contain more than one atom:author element.

[[explain inheritence]]

### 4.2.4 "atom:contributor" Element

The "atom:contributor" element is a Person construct that indicates a person or other entity who contributes to the feed. atom:head elements MAY contain one or more atom:contributor elements.

### 4.2.5 "atom:tagline" Element

The "atom:tagline" element is a Content construct that conveys a human-readable description or tagline for the feed. atom:head elements MAY contain an atom:tagline element, but MUST NOT contain more than one.

### 4.2.6 "atom:id" Element

The "atom:id" element's content conveys a permanent, globally unique identifier for the feed. It MUST NOT change over time, even if the feed is relocated. atom:head elements MAY contain an atom:id element, but MUST NOT contain more than one. The content of this element, when present, MUST be a URI.

xml:base [W3C.REC-xmlbase-20010627] processing MUST be applied to the atom:id element's content.

### 4.2.7 "atom:generator" Element

The "atom:generator" element's content indentifies the software agent used to generate the feed, for debugging and other purposes. atom:head elements MAY contain an atom:generator element, but MUST NOT contain more than one.

The content of this element, when present, MUST be a string that is a human-readable name for the generating agent.

The atom:generator element MAY have a "uri" attribute whose value MUST be a URI. When dereferenced, that URI SHOULD produce a representation that is relevant to that agent.

The atom:generator element MAY have a "version" attribute that indicates the version of the generating agent. When present, its value is unstructured text.

### 4.2.8 "atom:copyright" Element

The "atom:copyright" element is Content construct that conveys a human-readable copyright statement for the feed. atom:head elements MAY contain an atom:copyright element, but MUST NOT contain more than one.

The atom:copyright element SHOULD NOT be used to convey machine-readable licensing information.

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.

### 4.2.9 "atom:info" Element

The "atom:info" element is a Content construct that conveys a human-readable explanation of the feed format itself. atom:head elements MAY contain an atom:info element, but MUST NOT contain more than one.

The atom:info element SHOULD NOT considered meaningful by processors; it is a convenience to publishers in certain situations.

### 4.2.10 "atom:modified" Element

The "atom:modified" element is a Date construct that indicates the time when the state of the feed was last modified, including any changes to entries therein. atom:head elements MUST contain exactly one atom:modified element.

The content of an atom:modified element SHOULD have a time zone whose value MUST be "UTC".

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# 5 The "atom:entry" Element

The "atom:entry" element represents an individual entry. This 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 Entry Document.

When appearing in an Atom Entry Document, atom:entry elements MUST have a "version" attribute whose content indicates the version of the Atom specification that the entry conforms to.

The version identifier for this specification is "draft-ietf-atompub-format-01: do not deploy".

The atom:entry element MAY contain any namespace-qualified [W3C.REC-xml-names-19990114] elements as children. Ordering of the element children of atom:entry element MUST NOT be considered significant.

The following child elements are defined by this specification (note that it requires the presence of some of these elements):

## 5.1 "atom:title" Element

The "atom:title" element is a Content construct that conveys a human-readable title for the entry. atom:entry elements MUST have exactly one "atom:title" element.

## 5.2 "atom:link" Element

The "atom:link" element is a Link construct that conveys a URI associated with the entry. The nature of the relationship as well as the link itself is determined by the element's content.

atom:entry elements MUST 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 with a rel attribute value of "alternate" that has the same type attribute value.

atom:entry elements MAY contain additional atom:link elements beyond those described above.

## 5.3 "atom:author" Element

The "atom:author" element is a Person construct that indicates the default author of the entry. atom:entry elements MUST contain exactly one atom:author element, unless, in an Atom Feed Document, the atom:head element contains an atom:author element itself. atom:entry elements MUST NOT contain more than one atom:author element.

## 5.4 "atom:contributor" Element

The "atom:contributor" element is a Person construct that indicates a person or other entity who contributes to the entry. atom:entry elements MAY contain one or more atom:contributor elements.

## 5.5 "atom:id" Element

The "atom:id" element's content conveys a permanent, globally unique identifier for the entry. It MUST NOT change over time, even if other representations of the entry (such as a web representation pointed to by the entry's atom:link element) are relocated.

For a given entry, the atom:id element's content MUST be stable across all Atom Documents published by the same entity.

atom:entry MUST contain exactly one atom:id element. The content of this element MUST be a URI.

## 5.6 "atom:modified" Element

The "atom:modified" element is a Date construct that indicates the time that the entry was last modified. atom:entry elements MUST contain an atom:modified element, but MUST NOT contain more than one.

The content of an atom:modified element MUST have a time zone whose value SHOULD be "UTC".

## 5.7 "atom:issued" Element

The "atom:issued" element is a Date construct that indicates the time that the entry was issued. atom:entry elements MUST contain an atom:issued element, but MUST NOT contain more than one.

The content of an atom:issued element MAY omit a time zone.

## 5.8 "atom:created" Element

The "atom:created" element is a Date construct that indicates the time that the entry was created. atom:entry elements MAY contain an atom:created element, but MUST NOT contain more than one.

The content of an atom:created element MUST have a time zone whose value SHOULD be "UTC".

If atom:created is not present, its content MUST considered to be the same as that of atom:modified.

## 5.9 "atom:summary" Element

The "atom:summary" element is a Content construct that conveys a short summary, abstract or excerpt of the entry. atom:entry elements MAY contain an atom:summary element, but MUST NOT contain more than one.

## 5.10 "atom:content" Element

The "atom:content" element is a Content construct that conveys the content of the entry. atom:entry elements MAY contain one or more atom:content elements.

If @type="multipart/alternative", @mode MUST NOT be specified, and content element MUST contain 1 or more content elements. These content elements MUST NOT specify @type="multipart/alternative" (i.e. only one level of nesting is allowed). Consumers SHOULD look at all alternative content elements and determine which one is most suitable, based on which @type and @mode the consumer supports, and preferences specified by the end user (if any). Consumers SHOULD NOT render more than one content alternative.

## 5.11 "atom:copyright" Element

The "atom:copyright" element is a Content construct that conveys a human-readable copyright statement for the entry. atom:entry elements MAY contain an atom:copyright element, but MUST NOT contain more than one.

The atom:copyright element SHOULD NOT be used to convey machine-readable licensing information.

If an atom:entry element does not contain an atom:copyright element, then the atom:copyright element of the containing atom:feed element's atom:head element, if present, should be considered to apply to the entry.

## 5.12 "atom:origin" Element

The "atom:origin" element's content conveys the original source of the entry; e.g., the feed where the entry was first published.

If the source is an Atom Feed Document, then the content of atom:origin MUST be the same, character-for-character, as that of the href attribute of the atom:link element that has a rel attribute value of "alternate" in that document's atom:head section (i.e., the XPath expression "/atom:feed/atom:head/atom:link[@rel='alternate']/@href").

The content of this element MUST be a URI. atom:entry elements MAY contain an atom:origin element, but MUST NOT contain more than one.

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# 6 Managing Feed State

[[ talk about what it means to keep a view of a feed ]]

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# 7 Embedding Atom in Other Formats

[[ ... ]]

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# 8 Extending Atom

[[ ... ]]

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# 9 IANA Considerations

An Atom Document, when serialized as XML 1.0, can be identified with the following media type:

MIME media type name:
  application
MIME subtype name:
  atom+xml
Mandatory parameters:
  None.
Optional parameters:
  "charset":
    This parameter has identical semantics to the charset parameter of the "application/xml" media type as specified in RFC 3023 [RFC3023]. [RFC3023].
Encoding considerations:
  Identical to those of "application/xml" as described in RFC 3023 [RFC3023], section 3.2.
Security considerations:
  As defined in this specification. [[update upon publication]]
  In addition, as this media type uses the "+xml" convention, it shares the same security considerations as described in RFC 3023 [RFC3023], section 10.
Interoperability considerations:
  There are no known interoperability issues.
Published specification:
  This specification. [[update upon publication]]
Applications which use this media type:
  No known applications currently use this media type.

Additional information:

Magic number(s):
  As specified for "application/xml" in RFC 3023 [RFC3023], section 3.2.
File extension:
  .atom
Fragment identifiers:
  As specified for "application/xml" in RFC 3023 [RFC3023], section 5.
Base URI:
  As specified in RFC 3023 [RFC3023], section 6.
Macintosh File Type code:
  TEXT
Person and email address to contact for further information:
  Mark Nottingham <mnot@pobox.com>
Intended usage:
  COMMON
Author/Change controller:
  This specification's author(s). [[update upon publication]]

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# 10 Security Considerations

[[ this is required ]]

TOC

# 11 Normative References

[Atom-protocol] | Gregorio, J. and R. Sayre, "The Atom Publishing Protocol", work-in-progress, July 2004.
[RFC2045] | Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies", RFC 2045, November 1996.
[RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2396] | Berners-Lee, T., Fielding, R.T. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
[RFC2822] | Resnick, P., "Internet Message Format", RFC 2822, April 2001.
[RFC3023] | Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001.
[RFC3066] | Alvestrand, H., "Tags for the Identification of Languages", BCP 47, RFC 3066, January 2001.
[W3C.NOTE-datetime-19980827] | Wolf, M and C Wicksteed, "Date and Time Formats", W3C NOTE NOTE-datetime-19980827, August 1998.
[W3C.REC-xml-20040204] | Yergeau, F, Bray, T, Paoli, J, Sperberg-McQueen, C and E Maler, "Extensible Markup Language (XML) 1.0 (Third Edition)", W3C REC REC-xml-20040204, February 2004.
[W3C.REC-xml-infoset-20011024] | Cowan, J and R Tobin, "XML Information Set", W3C REC REC-xml-infoset-20011024, October 2001.
[W3C.REC-xml-names-19990114] | Bray, T, Hollander, D and A Layman, "Namespaces in XML", W3C REC REC-xml-names-19990114, January 1999.
[W3C.REC-xmlbase-20010627] | Marsh, J, "XML Base", W3C REC REC-xmlbase-20010627, June 2001.

TOC

# Author's Address

| Mark Nottingham (editor)
EMail: | mnot@pobox.com
URI: | http://www.mnot.net/

TOC

# A Contributors

The following people contributed to preliminary drafts of this document: Tim Bray, Mark Pilgrim, and Sam Ruby. The content and concepts within are a product of the Atom community and the Atom Publishing Format and Protocol Working Group.

TOC

# B Revision History

[[ this section should be removed before final publication. ]]

-01:
  Constrained omission of "Information Item" to just elements and attributes.
  Clarified xml:lang inheritence.
  Removed entry- and feed-specific langauge about xml:lang (covered by general discussion of xml:lang)
  Changed xml:lang to reference XML for normative requirements.
  Changed "... MUST be a string" to "... is unstructued text."
  Remomved langauge about DOCTYPEs, PIs, Comments, Entities.
  Changed atom:url to atom:uri, @url to @uri
  Introduced atom:head
  Introduced "Atom Feed Document" and "Atom Entry Document".
  Removed requirement for all elements and attributes to be namespace-qualified; now children of selective elements
  Added extensibility to Person constructs.
  Removed requirement for media types to be registered (non-registered media types are legal)
  Added atom:origin (PaceEntryOrigin)
  Added requirement for entry/id to be present and a URI (PaceEntryIdRequired).
  Clarified approach to Comments, PIs and well-formedness, as per RFC3470.
  Referenced escaping algorithm in XML.
  Assorted editorial nits and cleanup, refactoring
-00:
  Initial IETF Internet-Draft submission.
  Added optional version attribute to entry (PaceEntryElementNeedsVersionAttribute).
  Added hreflang attribute (PaceHrefLang).
  Clarified inheritence of copyright element (PaceItemCopyright).
  Added xml:lang to entries (PaceItemLang).
  Tweaked Infoset-related language (PaceNoInfoSet).
  Clarified lack of structure in version attribute (PaceVersionAsText).
  Changed approach to XML Base (PaceXmlBaseEverywhere).
  Added XML Base processing to atom:id (PaceXmlBaseId).
  Various editorial cleanup and adjustments for IETF publication.

TOC

# Intellectual Property Statement

The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79.

Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at <http://www.ietf.org/ipr>.

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# Copyright Statement

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# Acknowledgement

Funding for the RFC Editor function is currently provided by the Internet Society.