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Network Working Group                                           J. Snell
Internet-Draft                                             June 17, 2007
Intended status: Standards Track
Expires: December 19, 2007


              Atom Publishing Protocol Features Extension
                   draft-snell-atompub-feature-05.txt

Status of this Memo

   By submitting this Internet-Draft, each 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 becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
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   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 on December 19, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document introduces extensions to the Atom Publishing Protocol
   introspection 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
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  Registry of Atom Publishing Features . . . . . . . . . . .  6
       5.1.1.  Initial Assignments  . . . . . . . . . . . . . . . . .  7
   6.  Normative References . . . . . . . . . . . . . . . . . . . . . 12
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
   Intellectual Property and Copyright Statements . . . . . . . . . . 14





































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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 in an,
   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 APP 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 presence of a f:feature element in an app:collection
   element is an indication 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.

     feature = element f:feature {
       atomCommonAttributes,
       attribute ref { atomUri },
       attribute required { 'yes' | 'no' }?,
       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.

   A 'required' attribute value of "yes" indicates that clients MUST
   utilize the identified feature when interacting with the collection.
   A server MAY reject requests from clients that do not support or use
   the feature.  If not specified, the value is assumed to be "no".

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



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   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 and a number of optional 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://code.google.com/apis/gdata/GoogleLogin"
            href="http://code.google.com/apis/gdata/"
            label="Google Login" required="yes" />
        </collection>
      </workspace>
    </app:server>


4.  Security Considerations

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


5.  IANA Considerations

5.1.  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



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   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  Href: (A URI referencing a document containing a detailed
      definition of the feature)
   o  Security Considerations:

5.1.1.  Initial Assignments

   The Registry of Features initially contains the following
   assignments:

5.1.1.1.  Drafts - http://www.w3.org/2007/app/drafts

   o  Ref: http://www.w3.org/2007/app/drafts
   o  Label: Drafts
   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].

5.1.1.2.  XHTML Content - http://www.w3.org/2007/app/xhtml-content

   o  Ref: http://www.w3.org/2007/app/xhtml-content
   o  Label: XHTML Content
   o  Description: The "XHTML Content" feature indicates that a server
      will accept the use of an XHTML value within the atom:content
      element.

5.1.1.3.  HTML Content - http://www.w3.org/2007/app/html-content

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

5.1.1.4.  Text Content - http://www.w3.org/2007/app/text-content

   o  Ref: http://www.w3.org/2007/app/text-content
   o  Label: Text 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.






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5.1.1.5.  XML Content - http://www.w3.org/2007/app/xml-content

   o  Ref: http://www.w3.org/2007/app/xml-content
   o  Label: XML 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.

5.1.1.6.  Binary Content - http://www.w3.org/2007/app/binary-content

   o  Ref: http://www.w3.org/2007/app/xhtml-content
   o  Label: Binary Content
   o  Description: The "Binary Content" feature indicates that a server
      will accept Base-64 encoded binary data within the atom:content
      element.

5.1.1.7.  Referenced Content - http://www.w3.org/2007/app/src-content

   o  Ref: http://www.w3.org/2007/app/ref-content
   o  Label: XHTML 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.

5.1.1.8.  XHTML Title - http://www.w3.org/2007/app/xhtml-title

   o  Ref: http://www.w3.org/2007/app/xhtml-title
   o  Label: XHTML Title
   o  Description: The "XHTML Title" feature indicates that a server
      will accept the use of an XHTML value within the atom:title
      element.

5.1.1.9.  HTML Title - http://www.w3.org/2007/app/html-title

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

5.1.1.10.  Text Title - http://www.w3.org/2007/app/text-title

   o  Ref: http://www.w3.org/2007/app/text-title
   o  Label: Text 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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5.1.1.11.  XHTML Summary - http://www.w3.org/2007/app/xhtml-summary

   o  Ref: http://www.w3.org/2007/app/xhtml-summary
   o  Label: XHTML Summary
   o  Description: The "XHTML Summary" feature indicates that a server
      will accept the use of an XHTML value within the atom:summary
      element.

5.1.1.12.  HTML Summary - http://www.w3.org/2007/app/html-summary

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

5.1.1.13.  Text Summary - http://www.w3.org/2007/app/text-summary

   o  Ref: http://www.w3.org/2007/app/text-summary
   o  Label: Text Summary
   o  Description: The "Text Summary" feature indicates that a server
      will accept the use of a plain text value within the atom:summary
      element.

5.1.1.14.  Auto Summary - http://www.w3.org/2007/app/auto-summary

   o  Ref: http://www.w3.org/2007/app/auto-summary
   o  Label: Auto 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.

5.1.1.15.  XHTML Rights - http://www.w3.org/2007/app/xhtml-rights

   o  Ref: http://www.w3.org/2007/app/xhtml-rights
   o  Label: XHTML Rights
   o  Description: The "XHTML Rights" feature indicates that a server
      will accept the use of an XHTML value within the atom:rights
      element.

5.1.1.16.  HTML Rights - http://www.w3.org/2007/app/html-rights

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



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5.1.1.17.  Text Rights - http://www.w3.org/2007/app/text-rights

   o  Ref: http://www.w3.org/2007/app/text-rights
   o  Label: Text 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.

5.1.1.18.  Authenticated Author - http://www.w3.org/2007/app/auth-author

   o  Ref: http://www.w3.org/2007/app/auth-author
   o  Label: Authenticated Author
   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
      information will either be rejected or ignored by the server.

5.1.1.19.  Slug - http://www.w3.org/2007/app/slug

   o  Ref: http://www.w3.org/2007/app/slug
   o  Label: Slug
   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.

5.1.1.20.  Multiple Categories -
           http://www.w3.org/2007/app/multiple-categories

   o  Ref: http://www.w3.org/2007/app/multiple-categories
   o  Label: Multiple Categories
   o  Description: The "Multiple Categories" feature indicates that a
      server will accept entries that contain multiple atom:category
      elements.

5.1.1.21.  Multiple Authors -
           http://www.w3.org/2007/app/multiple-authors

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







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5.1.1.22.  Multiple Contributors -
           http://www.w3.org/2007/app/multiple-contributors

   o  Ref: http://www.w3.org/2007/app/contributors
   o  Label: Multiple Contributors
   o  Description: The "Multiple Contributors" feature indicates that a
      server will accept and preserve atom:contributor elements
      contained by an entry.

5.1.1.23.  Preserve Infoset -
           http://www.w3.org/2007/app/preserve-infoset

   Label: Preserve Infoset

   Description: The "Preserve Infoset" feature indicates that a server
   will preserve the complete XML XML Infoset
   [W3C.REC-xml-infoset-20040204] of entries POST or PUT to a
   collection.

5.1.1.24.  Preserve IDs - http://www.w3.org/2007/app/preserve-id

   o  Ref: http://www.w3.org/2007/app/preserve-id
   o  Label: Preserve IDs
   o  Description: The "Preserve IDs" feature indicates that a server
      will preserve the value of atom:id elements as provided by a
      client.

5.1.1.25.  Preserve Dates - http://www.w3.org/2007/app/preserve-dates

   o  Ref: http://www.w3.org/2007/app/preserve-updated
   o  Label: Preserve Dates
   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.

5.1.1.26.  Preserve Extensions -
           http://www.w3.org/2007/app/preserve-extensions

   o  Ref: http://www.w3.org/2007/app/preserve-extensions
   o  Label: Preserve Extensions
   o  Description: The "Preserve Extensions" feature indicates that a
      server will preserve unknown foreign markup contained within an
      entry.

5.1.1.27.  Preserve Links - http://www.w3.org/2007/app/preserve-links






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   o  Ref: http://www.w3.org/2007/app/preserve-links
   o  Label: Preserve Links
   o  Description: The "Preserve Links" feature indicates that a server
      will preserve all atom:link elements contained within an entry.

5.1.1.28.  Preserve Rights - http://www.w3.org/2007/app/preserve-rights

   o  Ref: http://www.w3.org/2007/app/preserve-rights
   o  Label: Preserve Rights
   o  Description: The "Preserve Rights" feature indicates that a server
      will preserve all atom:rights elements and License Links
      [I-D.snell-atompub-feed-license] contained within an entry.

5.1.1.29.  Threading - http://purl.org/syndication/thread/1.0

   o  Ref: http://purl.org/syndication/thread/1.0
   o  Label: Threading
   o  Description: The Feed Thread feature indicates that the APP server
      accepts entries that contain the in-reply-to element as defined by
      [RFC4685].


6.  Normative References

   [I-D.ietf-atompub-protocol]
              Hora, B. and J. Gregorio, "The Atom Publishing Protocol",
              draft-ietf-atompub-protocol-15 (work in progress),
              May 2007.

   [I-D.snell-atompub-feed-license]
              Snell, J., "Atom License Extension",
              draft-snell-atompub-feed-license-11 (work in progress),
              March 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.

   [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.




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

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

   [W3C.REC-xml-20040204]
              Yergeau, F., Maler, E., Bray, T., Paoli, J., and C.
              Sperberg-McQueen, "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 Elias Torres, Robert Yates,
   David Johnson, Byrne Reese, Joe Gregorio, Bill de hO`ra and 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
   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Intellectual Property

   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
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   Copies of IPR disclosures made to the IETF Secretariat and any
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   The IETF invites any interested party to bring to its attention any
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   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Acknowledgment

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





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