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Network Working Group                                           J. Snell
Internet-Draft                                           August 21, 2007
Intended status: Standards Track
Expires: February 22, 2008


              Atom Publishing Protocol Features Extension
                   draft-snell-atompub-feature-07.txt

Status of this Memo

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   This Internet-Draft will expire on February 22, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document introduces extensions to the Atom Publishing Protocol
   service document format for expressing metadata about the behaviors,
   functions and capabilities supported by an Atom Publishing Protocol
   collection.







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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Notational Conventions . . . . . . . . . . . . . . . . . . . .  3
   3.  The f:feature element  . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Example  . . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.2.  Contradictory Features . . . . . . . . . . . . . . . . . .  6
   4.  The f:type element . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  An example f:feature using the f:type element  . . . . . .  7
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  7
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
     6.1.  Registry of Atom Publishing Features . . . . . . . . . . .  8
       6.1.1.  Initial Assignments  . . . . . . . . . . . . . . . . .  8
   7.  Normative References . . . . . . . . . . . . . . . . . . . . . 20
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 21
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 21
   Intellectual Property and Copyright Statements . . . . . . . . . . 22


































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1.  Introduction

   This document introduces extensions for the Atom Publishing Protocol
   service document format for expressing metadata about the behaviors,
   functions and capabilities supported by an Atom Publishing Protocol
   collection.


2.  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 BCP 14, [RFC2119].

   This specification uses XML Namespaces [W3C.REC-xml-names-19990114]
   to uniquely identify XML element names.  It uses the following
   namespace prefix for the indicated namespace URI;

     "f": "http://purl.org/atompub/features/1.0"

   This specification uses terms from the XML Infoset
   [W3C.REC-xml-infoset-20040204].  However, this specification uses a
   shorthand; the phrase "Information Item" is omitted when naming
   Element Information Items.  Therefore, when this specification uses
   the terms "element" and "attribute" it is referring, respectively, to
   the Element and Attribute Information Items in Infoset terms.

   This specification uses the terms "atomUri" and
   "atomCommonAttributes" from the non-normative RELAX NG Compact schema
   included in [RFC4287].  Where used, these serve the same purpose and
   have the same meaning as their use in [RFC4287].

   Atom allows the use of IRIs [RFC3987].  Every URI [RFC3986] is also
   an IRI, so a URI may be used wherever below an IRI is named.  There
   are two special considerations: (1) when an IRI that is not also a
   URI is given for dereferencing, it MUST be mapped to a URI using the
   steps in Section 3.1 of [RFC3987] and (2) when an IRI is serving as
   an identifier, it MUST NOT be so mapped.

   Any element defined by this specification MAY have an xml:base
   attribute [W3C.REC-xmlbase-20010627].  When xml:base is used, it
   serves the function described in section 5.1.1 of [RFC3986],
   establishing the base URI (or IRI) for resolving any relative
   references found within the effective scope of the xml:base
   attribute.

   Any element defined by this specification MAY have an xml:lang
   attribute, whose content indicates the natural language for the



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   element and its descendents.  The language context is only
   significant for elements and attributes declared to be "Language-
   Sensitive".  Requirements regarding the content and interpretation of
   xml:lang are specified in XML 1.0 [W3C.REC-xml-20040204], Section
   2.12.


3.  The f:feature element

   A feature is an abstract behavior, function and capability supported
   by an Atom Publishing Protocol collection.  Examples of features that
   might be supported by an Atom publishing server include support for
   draft entries, scheduled publication of entries, use of a particular
   set of Atom format extensions, use of a particular authentication
   scheme, and so on.  The f:feature element can be used in an app:
   collection element to indicate that the collection supports the
   feature specified and may require that a client wishing to use the
   endpoint use that feature.  Features are identified using permanent,
   universally unique IRI's.

     namespace f = "http://purl.org/atompub/features/1.0"

     feature = element f:feature {
       atomCommonAttributes,
       attribute ref    { atomUri },
       attribute status { 'supported' | 'required' | 'unsupported'}?,
       attribute href   { atomUri }?,
       attribute label  { text }?,
       (anyElement)*
     }

     anyElement = element * - f:* {
       (attribute * { text }
         | text
         | anyElement)*
     }

   The ref attribute specifies a globally unique IRI identifying a
   feature supported by a collection.  The value of the ref attribute
   MUST be compared on a case-sensitive, character-by-character basis.
   Relative references MUST NOT be used.

   The status attribute indicates a collections level of support for the
   identified feature.  The value of the attribute can be "supported",
   "required" or "unsupported".  If not specified, the value is assumed
   to be "supported".





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   o  The value "supported" indicates that the server supports the
      identified feature.  Clients MAY utilize the feature when
      interacting with the collection.
   o  The value "required" indicates that server supports the identified
      feature.  Clients MUST utilize the feature when interacting with
      the collection.
   o  The value "unsupported" indicates that the server explicitly does
      not support a feature.  Clients SHOULD NOT utilize the feature
      when interacting with the collection.

   An optional href attribute MAY be used to specify the URI of a human-
   readable description of the feature.  Relative references MAY be
   used.

   The optional label attribute MAY be used to specify a human-readable
   label for the feature.  The value of the label attribute is Language-
   Sensitive as defined by Section 2 of [RFC4287].

   The f:feature element MAY contain child elements and attributes other
   than those defined in this specification.  Such "foreign markup" are
   considered to be metadata applicable to the feature identified by the
   f:feature element.  Software agents MUST NOT stop processing or
   signal an error or change their behavior as a result of encountering
   such foreign markup.

   An app:collection element MAY contain zero or more f:feature elements
   but MUST NOT contain more than one with the same ref attribute value.
   The order in which f:feature elements appear within the app:
   collection element is insignificant.

   The f:feature element MAY contain attributes included as part of the
   atomCommonAttributes production defined by Section 2 of [RFC4287] or
   any update thereof.  When used on an f:feature element, such
   attributes serve the same purpose described in [RFC4287] or their
   corresponding specifications.
















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3.1.  Example

   The following is an example of a collection supporting one
   hypothetical required feature, one unsupported feature, and a number
   of supported features.

     <service
       xmlns="http://www.w3.org/2007/app"
       xmlns:atom="http://www.w3.org/2005/Atom"
       xmlns:f="http://purl.org/atompub/features/1.0">
       <workspace>
         <atom:title>My Workspace</atom:title>
         <collection href="...">
           <atom:title>My Atom Collection</atom:title>
           <accept>application/atom+xml;type=entry</accept>
           <f:feature
             ref="http://www.w3.org/2007/app/drafts" />
           <f:feature
             ref="http://www.w3.org/2007/app/xhtml-content" />
           <f:feature
             ref="http://www.w3.org/2007/app/preserve-extensions" />
           <f:feature
             ref="http://purl.org/syndication/thread/1.0" />
           <f:feature
             ref="http://www.w3.org/2007/app/binary-content"
             status="unsupported" />
           <f:feature
             ref="http://code.google.com/apis/gdata/GoogleLogin"
             href="http://code.google.com/apis/gdata/"
             label="Google Login" status="required" />
         </collection>
       </workspace>
     </app:server>

3.2.  Contradictory Features

   Some combinations of features can be contradictory when the support
   level of one or more of those features is "required" and the others
   are "supported".  For instance, a collection that specifies that
   XHTML values in the atom:title is required and that HTML in an atom:
   title is supported is contradictory.  Such contradictions can cause
   problems for clients that are attempting to select an appropriate
   collection based on the support level of various features.  A service
   document MUST NOT specify contradictory features.  If a client
   determines that the features specified in a service document are
   contradictory, the client SHOULD proceed as if the support level for
   each of those features is "supported".




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4.  The f:type element

   The content of an f:type element is a media-range as defined in
   [RFC2616].  The media range specifies a type of content that can be
   included in an atom:content element or referenced by the atom:content
   src attribute.

     type =
       element f:type {
         atomCommonAttributes,
         ( text? )
       }

   Media type parameters are allowed within f:type, but f:type has no
   notion of preference - "accept-params" or "q" arguments, as specified
   in Section 14.1 of [RFC2616] are not significant.

   White space (as defined in [W3C.REC-xml-20040204]) around the f:type
   element's media-range is insignificant and MUST be ignored.

   Any number of f:type elements MAY appear as children of an f:feature
   element.  When used with features whose ref attributes identify the
   "XML Content", "Binary Content" or "Reference Content" features as
   defined in Section 6.1.1, the f:type elements specify the set of
   media types that can be specified in the atom:content elements type
   attribute.  If no f:type element are present, clients SHOULD treat
   this as equivalent to an f:type element with the content "*/*".

   The order of f:type elements within a f:feature element is
   insignificant.

4.1.  An example f:feature using the f:type element


     <f:feature
       ref="http://www.w3.org/2007/app/binary-content">
       <f:type>image/jpg</f:type>
       <f:type>image/png</f:type>
       <f:type>image/gif</f:type>
       <f:type>text/*</f:type>
     </f:feature>



5.  Security Considerations

   Specific features supported by a collection may introduce security
   considerations and concerns beyond those discussed by the Atom



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   Publishing Protocol and Atom Syndication Format specifications.
   Implementors must refer to the specifications and description of each
   feature to determine the security considerations relevant to each.


6.  IANA Considerations

6.1.  Registry of Atom Publishing Features

   The Registry of Atom Publishing Features is maintained by IANA and
   contains information about known features that can be supported by
   Atom Publishing Protocol implementations.  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 use the following
   template:

   o  Ref: (A globally unique IRI identifying the feature)
   o  Label: (A human-readable label for the feature)
   o  Description: (A human-readable description of the feature)
   o  Support Levels: (A description of the relevant support levels for
      the feature)
   o  Contradictory Features: (A listing of features that are
      contradictory to this feature when one or more are marked as
      "required")
   o  Href: (A URI referencing a document containing a detailed
      definition of the feature)
   o  Security Considerations:

6.1.1.  Initial Assignments

   The Registry of Features initially contains the following
   assignments:

6.1.1.1.  Drafts

   o  Ref: http://www.w3.org/2007/app/drafts
   o  Label: Drafts
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         contain the app:draft control element.
      *  "required" indicates that the collection requires all entries
         to contain the app:draft control element.
      *  "unsupported" indicates that the collection does not accept
         entries that use the app:draft control element or that the
         server will ignore the element if present.





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   o  Contradictory Features: none
   o  Description: The "Drafts" feature indicates that a collection
      supports the use of the app:draft control element as defined in
      section 13.1.1 of [I-D.ietf-atompub-protocol].

6.1.1.2.  XHTML Content

   o  Ref: http://www.w3.org/2007/app/xhtml-content
   o  Label: XHTML Content
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide XHTML in the atom:content element.
      *  "required" indicates that the collection requires all entries
         to provide XHTML in the atom:content element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide XHTML in the atom:content element.
   o  Contradictory Features: http://www.w3.org/2007/app/html-content,
      http://www.w3.org/2007/app/text-content,
      http://www.w3.org/2007/app/xml-content,
      http://www.w3.org/2007/app/binary-content,
      http://www.w3.org/2007/app/ref-content
   o  Description: The "XHTML Content" feature indicates that a server
      will accept the use of an XHTML value within the atom:content
      element.

6.1.1.3.  HTML Content

   o  Ref: http://www.w3.org/2007/app/html-content
   o  Label: HTML Content
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide HTML in the atom:content element.
      *  "required" indicates that the collection requires all entries
         to provide HTML in the atom:content element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide HTML in the atom:content element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-content,
      http://www.w3.org/2007/app/text-content,
      http://www.w3.org/2007/app/xml-content,
      http://www.w3.org/2007/app/binary-content,
      http://www.w3.org/2007/app/ref-content
   o  Description: The "HTML Content" feature indicates that a server
      will accept the use of an escaped HTML value within the atom:
      content element.







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6.1.1.4.  Text Content

   o  Ref: http://www.w3.org/2007/app/text-content
   o  Label: Text Content
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide plain text in the atom:content element.
      *  "required" indicates that the collection requires all entries
         to provide plain text in the atom:content element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide plain text in the atom:content element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-content,
      http://www.w3.org/2007/app/html-content,
      http://www.w3.org/2007/app/xml-content,
      http://www.w3.org/2007/app/binary-content,
      http://www.w3.org/2007/app/ref-content
   o  Description: The "Text Content" feature indicates that a server
      will accept the use of a plain text value within the atom:content
      element.

6.1.1.5.  XML Content

   o  Ref: http://www.w3.org/2007/app/xml-content
   o  Label: XML Content
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide well-formed XML in the atom:content element.
      *  "required" indicates that the collection requires all entries
         to provide well-formed XML in the atom:content element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide XML in the atom:content element.  The MIME
         media type of acceptable XML formats is specified using one or
         more f:type elements within the f:feature.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-content,
      http://www.w3.org/2007/app/html-content,
      http://www.w3.org/2007/app/text-content,
      http://www.w3.org/2007/app/binary-content,
      http://www.w3.org/2007/app/ref-content
   o  Description: The "XML Content" feature indicates that a server
      will accept the use of well-formed XML content within the atom:
      content element.

6.1.1.6.  Binary Content

   o  Ref: http://www.w3.org/2007/app/binary-content
   o  Label: Binary Content





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   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide binary content in the atom:content element.
      *  "required" indicates that the collection requires all entries
         to provide binary content in the atom:content element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide binary content in the atom:content
         element.  The MIME media type of acceptable binary formats is
         specified using one or more f:type elements within the
         f:feature.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-content,
      http://www.w3.org/2007/app/html-content,
      http://www.w3.org/2007/app/text-content,
      http://www.w3.org/2007/app/xml-content,
      http://www.w3.org/2007/app/ref-content
   o  Description: The "Binary Content" feature indicates that a server
      will accept Base-64 encoded binary data within the atom:content
      element.

6.1.1.7.  Referenced Content

   o  Ref: http://www.w3.org/2007/app/ref-content
   o  Label: XHTML Content
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         use the atom:content src attribute to reference external
         content.
      *  "required" indicates that the collection requires all entries
         to use the atom:content src attribute to reference external
         content.
      *  "unsupported" indicates that the collection does not accept
         entries that use the atom:content src attribute.  The MIME
         media type of acceptable referenced resources is specified
         using one or more f:type elements within the f:feature.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-content,
      http://www.w3.org/2007/app/html-content,
      http://www.w3.org/2007/app/text-content,
      http://www.w3.org/2007/app/xml-content,
      http://www.w3.org/2007/app/binary-content
   o  Description: The "Referenced Content" feature indicates that a
      server will accept atom:content elements that use the src
      attribute to reference external content resources.

6.1.1.8.  XHTML Title

   o  Ref: http://www.w3.org/2007/app/xhtml-title





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   o  Label: XHTML Title
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide XHTML in the atom:title element.
      *  "required" indicates that the collectionrequires all entries to
         provide XHTML in the atom:title element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide XHTML in the atom:title element.
   o  Contradictory Features: http://www.w3.org/2007/app/html-title,
      http://www.w3.org/2007/app/text-title
   o  Description: The "XHTML Title" feature indicates that a server
      will accept the use of an XHTML value within the atom:title
      element.

6.1.1.9.  HTML Title

   o  Ref: http://www.w3.org/2007/app/html-title
   o  Label: HTML Title
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide HTML in the atom:title element.
      *  "required" indicates that the collection requires all entries
         to provide HTML in the atom:title element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide HTML in the atom:title element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-title,
      http://www.w3.org/2007/app/text-title
   o  Description: The "HTML Content" feature indicates that a server
      will accept the use of an escaped HTML value within the atom:title
      element.

6.1.1.10.  Text Title

   o  Ref: http://www.w3.org/2007/app/text-title
   o  Label: Text Title
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide plain text in the atom:title element.
      *  "required" indicates that the collection requires all entries
         to provide plain text in the atom:title element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide plain text in the atom:title element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-title,
      http://www.w3.org/2007/app/html-title
   o  Description: The "Text Content" feature indicates that a server
      will accept the use of a plain text value within the atom:title
      element.




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6.1.1.11.  XHTML Summary

   o  Ref: http://www.w3.org/2007/app/xhtml-summary
   o  Label: XHTML Summary
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide XHTML in the atom:summary element.
      *  "required" indicates that the collection requires all entries
         to provide XHTML in the atom:summary element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide XHTML in the atom:summary element.
   o  Contradictory Features: http://www.w3.org/2007/app/html-summary,
      http://www.w3.org/2007/app/text-summary
   o  Description: The "XHTML Summary" feature indicates that a server
      will accept the use of an XHTML value within the atom:summary
      element.

6.1.1.12.  HTML Summary

   o  Ref: http://www.w3.org/2007/app/html-summary
   o  Label: HTML Summary
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide HTML in the atom:summary element.
      *  "required" indicates that the collection requires all entries
         to provide HTML in the atom:summary element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide HTML in the atom:summary element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-summary,
      http://www.w3.org/2007/app/text-summary
   o  Description: The "HTML Summary" feature indicates that a server
      will accept the use of an escaped HTML value within the atom:
      summary element.

6.1.1.13.  Text Summary

   o  Ref: http://www.w3.org/2007/app/text-summary
   o  Label: Text Summary
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide plain text in the atom:summary element.
      *  "required" indicates that the collection requires all entries
         to provide plain text in the atom:summary element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide plain text in the atom:summary element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-summary,
      http://www.w3.org/2007/app/html-summary




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   o  Description: The "Text Summary" feature indicates that a server
      will accept the use of a plain text value within the atom:summary
      element.

6.1.1.14.  Auto Summary

   o  Ref: http://www.w3.org/2007/app/auto-summary
   o  Label: Auto Summary
   o  Support Levels:
      *  "supported" indicates that the server will automatically
         generate an atom:summary element if the entry provided by the
         client does not already contain one.
      *  "required" indicates that the server will automatically
         generate an atom:summary element regardless of whether the
         entry already contains one.
      *  "unsupported" indicates that the server will not automatically
         generate an atom:summary element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-summary,
      http://www.w3.org/2007/app/html-summary,
      http://www.w3.org/2007/app/text-summary
   o  Description: The "Auto Summary" feature indicates that a server
      will autogenerate the value of the atom:summary element and will
      either reject or ignore attempts by the client to modify the value
      of atom:summary.

6.1.1.15.  XHTML Rights

   o  Ref: http://www.w3.org/2007/app/xhtml-rights
   o  Label: XHTML Rights
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide XHTML in the atom:rights element.
      *  "required" indicates that the collection requires all entries
         to provide XHTML in the atom:rights element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide XHTML in the atom:rights element.
   o  Contradictory Features: http://www.w3.org/2007/app/html-rights,
      http://www.w3.org/2007/app/text-rights
   o  Description: The "XHTML Rights" feature indicates that a server
      will accept the use of an XHTML value within the atom:rights
      element.

6.1.1.16.  HTML Rights

   o  Ref: http://www.w3.org/2007/app/html-rights
   o  Label: HTML Rights





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   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide HTML in the atom:rights element.
      *  "required" indicates that the collection requires all entries
         to provide HTML in the atom:rights element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide HTML in the atom:rights element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-rights,
      http://www.w3.org/2007/app/text-rights
   o  Description: The "HTML Rights" feature indicates that a server
      will accept the use of an escaped HTML value within the atom:
      rights element.

6.1.1.17.  Text Rights

   o  Ref: http://www.w3.org/2007/app/text-rights
   o  Label: Text Rights
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         provide plain text in the atom:rights element.
      *  "required" indicates that the collection requires all entries
         to provide plain text in the atom:rights element.
      *  "unsupported" indicates that the collection does not accept
         entries that provide plain text in the atom:rights element.
   o  Contradictory Features: http://www.w3.org/2007/app/xhtml-rights,
      http://www.w3.org/2007/app/html-rights
   o  Description: The "Text Rights" feature indicates that a server
      will accept the use of a plain text value within the atom:rights
      element.

6.1.1.18.  Authenticated Author

   o  Ref: http://www.w3.org/2007/app/auth-author
   o  Label: Authenticated Author
   o  Support Levels:
      *  "supported" indicates that the server will automatically
         generate the atom:author element based on the client's
         authenticated identity.
      *  For this feature,"required" is synonymous with "supported".
      *  "unsupported" indicates that the server will not automatically
         generate the atom:author for an entry based on the client's
         authenticated identity.
   o  Contradictory Features:
      http://www.w3.org/2007/app/multiple-authors
   o  Description: The "Authenticated Author" feature indicates that a
      server will use the authenticated identity of the client to
      determine the values to use within the atom:author element.
      Attempts by a client to manually set or modify the author



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      information will either be rejected or ignored by the server.

6.1.1.19.  Slug

   o  Ref: http://www.w3.org/2007/app/slug
   o  Label: Slug
   o  Support Levels:
      *  "supported" indicates that the collection accepts the use of
         the Slug header in POST requests.
      *  "required" indicates that the collection requires that the Slug
         header be used for all POST requests.
      *  "unsupported" indicates that the collection will not accept the
         use of the Slug header in POST requests or that the header will
         be ignored.
   o  Contradictory Features: none
   o  Description: The "Slug" feature indicates that a server will use
      the Slug request header defined in section 9.7 of
      [I-D.ietf-atompub-protocol] to set the URI of newly created
      resources.

6.1.1.20.  Multiple Categories

   o  Ref: http://www.w3.org/2007/app/multiple-categories
   o  Label: Multiple Categories
   o  Support Levels:
      *  "supported" indicates that the collection accepts the use of
         multiple atom:category elements within an entry.
      *  For this feature, "required" is synonymous with "supported".
      *  "unsupported" indicates that the collection will not accept
         entries with multiple atom:category elements or that that
         additional atom:category elements will be ignored.
   o  Contradictory Features: none
   o  Description: The "Multiple Categories" feature indicates that a
      server will accept entries that contain multiple atom:category
      elements.

6.1.1.21.  Multiple Authors

   o  Ref: http://www.w3.org/2007/app/multiple-authors
   o  Label: Multiple Authors
   o  Support Levels:
      *  "supported" indicates that the collection accepts the use of
         multiple atom:author elements within an entry.
      *  For this feature, "required" is synonymous with "supported".
      *  "unsupported" indicates that the collection will not accept
         entries with multiple atom:author elements or that the
         additional atom:author elements will be ignored.




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   o  Contradictory Features: http://www.w3.org/2007/app/auth-author
   o  Description: The "Multiple Authors" feature indicates that a
      server will accept and preserve multiple atom:author elements
      contained by an entry.

6.1.1.22.  Multiple Contributors

   o  Ref: http://www.w3.org/2007/app/contributors
   o  Label: Multiple Contributors
   o  Support Levels:
      *  "supported" indicates that the collection accepts the use of
         multiple atom:contributor elements within an entry.
      *  For this feature, "required" is synonymous with "supported".
      *  "unsupported" indicates that the collection will not accept
         entries with multiple atom:contributor elements or that the
         additional atom:contributor elements will be ignored.
   o  Contradictory Features: none
   o  Description: The "Multiple Contributors" feature indicates that a
      server will accept and preserve atom:contributor elements
      contained by an entry.

6.1.1.23.  Preserve Infoset

   o  Ref: http://www.w3.org/2007/app/preserve-infoset
   o  Label: Preserve Infoset
   o  Support Levels:
      *  "supported" indicates that the collection will store entries in
         such a way as to preserve the complete XML infoset of the entry
         document.
      *  For this feature, "required" is synonymous with "supported".
      *  "unsupported" indicates that the collection will not preserve
         the complete XML infoset of the entry when storing.
   o  Contradictory Features: none
   o  Description: The "Preserve Infoset" feature indicates that a
      server will preserve the complete XML Infoset
      [W3C.REC-xml-infoset-20040204] of entries POST or PUT to a
      collection.

6.1.1.24.  Preserve IDs

   o  Ref: http://www.w3.org/2007/app/preserve-id
   o  Label: Preserve IDs
   o  Support Levels:
      *  "supported" indicates that the collection will preserve the
         value of the atom:id element as provided by the client.
      *  For this feature, "required" is synonymous with "supported".





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      *  "unsupported" indicates that the collection will not preserve
         the value of the atom:id element as provided by the client
         (e.g. the server will generate it's own value for the atom:id
         element.
   o  Contradictory Features: none
   o  Description: The "Preserve IDs" feature indicates that a server
      will preserve the value of atom:id elements as provided by a
      client.

6.1.1.25.  Preserve Dates

   o  Ref: http://www.w3.org/2007/app/preserve-updated
   o  Label: Preserve Dates
   o  Support Levels:
      *  "supported" indicates that the collection will preserve the
         value of all date elements as provided by the client.
      *  For this feature,"required" is synonymous with "supported".
      *  "unsupported" indicates that the collection will not preserve
         the value of date elements as provided by the client (e.g. the
         server will generate it's own value for the date elements.
   o  Contradictory Features: none
   o  Description: The "Preserve Dates" feature indicates that a server
      will preserve the value of the atom:updated and atom:published
      elements as provided by a client.

6.1.1.26.  Preserve Extensions

   o  Ref: http://www.w3.org/2007/app/preserve-extensions
   o  Label: Preserve Extensions
   o  Support Levels:
      *  "supported" indicates that the collection will preserve all
         extensions contained within an entry.
      *  For this feature, "required" is synonymous with "supported".
      *  "unsupported" indicates that the collection will not preserve
         all extensions contained within an entry, however some
         extensions may be preserved.
   o  Contradictory Features: none
   o  Description: The "Preserve Extensions" feature indicates that a
      server will preserve unknown foreign markup contained within an
      entry.

6.1.1.27.  Preserve Links

   o  Ref: http://www.w3.org/2007/app/preserve-links
   o  Label: Preserve Links
   o  Support Levels:





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      *  "supported" indicates that the collection will preserve all
         atom:link elements contained within an entry.
      *  For this feature, "required" is synonymous with "supported".
      *  "unsupported" indicates that the collection will not preserve
         all atom:links contained within an entry, however some atom:
         link elements may be preserved.
   o  Contradictory Features: none
   o  Description: The "Preserve Links" feature indicates that a server
      will preserve all atom:link elements contained within an entry.

6.1.1.28.  Preserve Rights

   o  Ref: http://www.w3.org/2007/app/preserve-rights
   o  Label: Preserve Rights
   o  Support Levels:
      *  "supported" indicates that the collection will preserve the
         value of the atom:rights element as well as all License Links
         [RFC4946] contained within an entry.
      *  For this feature, "required" is synonymous with "supported".
      *  "unsupported" indicates that the collection may not preserve
         the value of the atom:rights element or all License Links
         [RFC4946], however, some rights information may be preserved.
   o  Contradictory Features: none
   o  Description: The "Preserve Rights" feature indicates that a server
      will preserve all atom:rights elements and License Links [RFC4946]
      contained within an entry.

6.1.1.29.  Threading

   o  Ref: http://purl.org/syndication/thread/1.0
   o  Label: Threading
   o  Support Levels:
      *  "supported" indicates that the collection accepts entries that
         contain the in-reply-to element as defined by [RFC4685].
      *  "required" indicates that the collection requires that all
         entries contain an in-reply-to element.
      *  "unsupported" indicates that the collection will not accept
         entries containing the in-reply-to element or that the element
         will be ignored if present.
   o  Contradictory Features: none
   o  Description: The Feed Thread feature indicates that the collection
      accepts entries that contain the in-reply-to element as defined by
      [RFC4685].

6.1.1.30.  Scheduled Publishing






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   o  Ref: http://www.w3.org/2007/app/scheduled-publishing
   o  Label: Scheduled Publishing
   o  Support Levels:
      *  "supported" indicates that the collection allows clients to
         specify a future instant in time for the atom:published element
         when the entry should be made publicly available.
      *  "required" indicates that the collection requires clients to
         specify a future instant in time for the atom:published
         element.
      *  "unsupported" indicates that the collection will not allow
         clients to specify a future instance in time for the atom:
         published element.
   o  Contradictory Features: none
   o  Description: The "Scheduled Publishing" feature indicates that a
      collection allows clients to set the value of an entries atom:
      published element to some future point in time after which the
      entry will be made publicly visible.  Prior to that time, the
      entry will be considered to be in a draft state and SHOULD contain
      an app:draft control element with a value of "yes".


7.  Normative References

   [I-D.ietf-atompub-protocol]
              Hora, B. and J. Gregorio, "The Atom Publishing Protocol",
              draft-ietf-atompub-protocol-17 (work in progress),
              July 2007.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.

   [RFC4287]  Nottingham, M., Ed. and R. Sayre, Ed., "The Atom
              Syndication Format", RFC 4287, December 2005.



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   [RFC4685]  Snell, J., "Atom Threading Extensions", RFC 4685,
              September 2006.

   [RFC4946]  Snell, J., "Atom License Extension", RFC 4946, July 2007.

   [W3C.REC-xml-20040204]
              Maler, E., Sperberg-McQueen, C., Paoli, J., Yergeau, F.,
              and T. Bray, "Extensible Markup Language (XML) 1.0 (Third
              Edition)", World Wide Web Consortium FirstEdition REC-xml-
              20040204, February 2004,
              <http://www.w3.org/TR/2004/REC-xml-20040204>.

   [W3C.REC-xml-infoset-20040204]
              Tobin, R. and J. Cowan, "XML Information Set (Second
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-infoset-20040204, February 2004,
              <http://www.w3.org/TR/2004/REC-xml-infoset-20040204>.

   [W3C.REC-xml-names-19990114]
              Hollander, D., Bray, T., and A. Layman, "Namespaces in
              XML", World Wide Web Consortium FirstEdition REC-xml-
              names-19990114, January 1999,
              <http://www.w3.org/TR/1999/REC-xml-names-19990114>.

   [W3C.REC-xmlbase-20010627]
              Marsh, J., "XML Base", World Wide Web Consortium
              Recommendation REC-xmlbase-20010627, June 2001,
              <http://www.w3.org/TR/2001/REC-xmlbase-20010627>.


Appendix A.  Acknowledgements

   The author acknowledges the feedback from the other members of the
   IETF Atom Publishing working group during the development of this
   specification.


Author's Address

   James M Snell


   Phone:
   Email: jasnell@gmail.com
   URI:   http://snellspace.com






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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


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   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
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   on the procedures with respect to rights in RFC documents can be
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Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





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