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Network Working Group                                   J. Gregorio, Ed.
Internet-Draft                                           BitWorking, Inc
Expires: August 5, 2006                                  B. de hOra, Ed.
                                                           Propylon Ltd.
                                                       February 01, 2006


                      The Atom Publishing Protocol
                   draft-ietf-atompub-protocol-08.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
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   This Internet-Draft will expire on August 5, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The Atom Publishing Protocol (APP) is an application-level protocol
   for publishing and editing Web resources.  The protocol is based on
   HTTP transport of Atom-formatted representations.  The Atom format is
   documented in the Atom Syndication Format (RFC4287).

Editorial Note




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   To provide feedback on this Internet-Draft, join the atom-protocol
   mailing list (http://www.imc.org/atom-protocol/index.html) [1].

Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.   Notational Conventions . . . . . . . . . . . . . . . . . . .   5
   3.   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.   Protocol Model . . . . . . . . . . . . . . . . . . . . . . .   7
   5.   Protocol Operations  . . . . . . . . . . . . . . . . . . . .   8
     5.1  Retrieving an Introspection Document . . . . . . . . . . .   8
     5.2  Creating a Resource  . . . . . . . . . . . . . . . . . . .   8
     5.3  Editing a Resource . . . . . . . . . . . . . . . . . . . .   8
       5.3.1  Retrieving a Resource  . . . . . . . . . . . . . . . .   9
       5.3.2  Updating a Resource  . . . . . . . . . . . . . . . . .   9
       5.3.3  Deleting a Resource  . . . . . . . . . . . . . . . . .   9
     5.4  Listing Collection Members . . . . . . . . . . . . . . . .  10
     5.5  Use of HTTP Response codes . . . . . . . . . . . . . . . .  10
   6.   XML-related Conventions  . . . . . . . . . . . . . . . . . .  11
     6.1  Referring to Information Items . . . . . . . . . . . . . .  11
     6.2  XML Namespace Usage  . . . . . . . . . . . . . . . . . . .  11
     6.3  Use of xml:base and xml:lang . . . . . . . . . . . . . . .  11
     6.4  RELAX NG Schema  . . . . . . . . . . . . . . . . . . . . .  12
   7.   Introspection Documents  . . . . . . . . . . . . . . . . . .  13
     7.1  Example  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     7.2  Element Definitions  . . . . . . . . . . . . . . . . . . .  14
       7.2.1  The "app:service" Element  . . . . . . . . . . . . . .  14
       7.2.2  The "app:workspace" Element  . . . . . . . . . . . . .  14
       7.2.3  The "app:collection" Element . . . . . . . . . . . . .  15
       7.2.4  The "app:member-type" Element  . . . . . . . . . . . .  16
   8.   Collections  . . . . . . . . . . . . . . . . . . . . . . . .  17
     8.1  Creating resources with POST . . . . . . . . . . . . . . .  17
       8.1.1  Example  . . . . . . . . . . . . . . . . . . . . . . .  17
       8.1.2  Title: Header  . . . . . . . . . . . . . . . . . . . .  17
     8.2  Entry Collections  . . . . . . . . . . . . . . . . . . . .  18
       8.2.1  Editing entries with foreign markup  . . . . . . . . .  18
     8.3  Media Collections  . . . . . . . . . . . . . . . . . . . .  18
       8.3.1  Editing Media Resources  . . . . . . . . . . . . . . .  18
       8.3.2  Editing Media Metadata . . . . . . . . . . . . . . . .  19
   9.   Listing Collections  . . . . . . . . . . . . . . . . . . . .  20
     9.1  Collection Paging  . . . . . . . . . . . . . . . . . . . .  20
   10.  Atom Format Link Relation Extensions . . . . . . . . . . . .  22
     10.1   The "edit" Link Relation . . . . . . . . . . . . . . . .  22
   11.  Atom Publishing Control Extensions . . . . . . . . . . . . .  23
     11.1   The Atom Publishing Control Namespace  . . . . . . . . .  23
     11.2   The "pub:control" Element  . . . . . . . . . . . . . . .  23
       11.2.1   The "pub:draft" Element  . . . . . . . . . . . . . .  23
   12.  Atom Publishing Protocol Example . . . . . . . . . . . . . .  24



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   13.  Securing the Atom Protocol . . . . . . . . . . . . . . . . .  26
   14.  Security Considerations  . . . . . . . . . . . . . . . . . .  27
   15.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  28
   16.  References . . . . . . . . . . . . . . . . . . . . . . . . .  30
     16.1   Normative References . . . . . . . . . . . . . . . . . .  30
     16.2   Informative References . . . . . . . . . . . . . . . . .  31
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  32
   A.   Contributors . . . . . . . . . . . . . . . . . . . . . . . .  33
   B.   RELAX NG Compact Schema  . . . . . . . . . . . . . . . . . .  34
   C.   Revision History . . . . . . . . . . . . . . . . . . . . . .  37
        Intellectual Property and Copyright Statements . . . . . . .  40








































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1.  Introduction

   The Atom Publishing Protocol is an application-level protocol for
   publishing and editing Web resources using HTTP [RFC2616] and XML 1.0
   [W3C.REC-xml-20040204].  The protocol supports the creation of
   arbitrary web resources and provides facilities for:

   o  Collections: Sets of resources, which may be retrieved in whole or
      in part.

   o  Introspection: Discovering and describing collections.

   o  Editing: Creating, updating and deleting resources.






































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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 [RFC2119].

   Note: The Introspection Document allows the use of IRIs [RFC3987], as
   well as URIs [RFC3986].  Every URI is an IRI, so any URI can be used
   where an IRI is needed.  How to map an IRI to a URI is specified in
   Section 3.1 of Internationalized Resource Identifiers (IRIs)
   [RFC3987].








































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3.  Terminology

   For convenience, this protocol may be referred to as the "Atom
   Protocol" or "APP".

   URI/IRI - A Uniform Resource Identifier and Internationalized
   Resource Identifier.  These terms and the distinction between them
   are defined in [RFC3986] and [RFC3987].  Note that IRIs are mapped to
   URIs before dereferencing takes place.

   Resource - A network-accessible data object or service identified by
   an IRI, as defined in [RFC2616].  See [W3C.REC-webarch-20041215] for
   further discussion on resources.

   The phrase "the URI of a document" in this specification is shorthand
   for "an URI which, when dereferenced, is expected to produce that
   document as a representation".

   Representation - An entity included with a request or response as
   defined in [RFC2616].

   Collection - A resource that contains a set of member IRIs.  See
   Section 8.

   Member - A resource whose IRI is listed in a Collection.

   Introspection Document - A document that describes the location and
   capabilities of one or more Collections.  See Section 7.























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4.  Protocol Model

   The Atom Publishing Protocol uses HTTP to edit and author web
   resources.  The Atom Protocol uses the following HTTP methods:

   o  GET is used to retrieve a representation of a resource or perform
      a query.

   o  POST is used to create a new, dynamically-named resource.

   o  PUT is used to update a known resource.

   o  DELETE is used to remove a resource.

   Along with operations on resources, the Atom Protocol provides list-
   based structures, called Collections, for managing and organising
   resources, called Members.  Collections contain the IRIs of, and
   metadata about, their Member resources.  For authoring and editing of
   resources to commence, an Atom Protocol client can examine
   Introspection Documents which represent server-defined groups of
   Collections.

   Note that when an IRI is used for resource retrieval over HTTP, the
   IRI is first converted to a URI according the procedure defined in
   [RFC3987] section 3.1.  The resource that the IRI locates is the same
   as the one located by the URI obtained after converting the IRI.

























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5.  Protocol Operations

5.1  Retrieving an Introspection Document

   Client                                     Server
     |                                           |
     |  1.) GET to URI of Introspection Document |
     |------------------------------------------>|
     |                                           |
     |  2.) Introspection Document               |
     |<------------------------------------------|
     |                                           |

   1.  The client sends a GET request to the URI of the Introspection
       Document.

   2.  The server responds with the document enumerating the IRIs of a
       set of Collections and the capabilities of those Collections
       supported by the server.  The content of this document can vary
       based on aspects of the client request, including, but not
       limited to, authentication credentials.


5.2  Creating a Resource

   Client                                     Server
     |                                           |
     |  1.) POST to URI of Collection            |
     |------------------------------------------>|
     |                                           |
     |  2.) 201 Created                          |
     |<------------------------------------------|
     |                                           |

   1.  The client POSTs a representation of the Member to the URI of the
       collection.

   2.  If the Member resource was created successfully, the server
       responds with a status code of 201 and a Location: header that
       contains the URI of the newly created resource.


5.3  Editing a Resource

   Once a resource has been created and its URI is known, that URI may
   be used to retrieve, update, and delete the resource.





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5.3.1  Retrieving a Resource

   Client                                     Server
     |                                           |
     |  1.) GET to Member URI                    |
     |------------------------------------------>|
     |                                           |
     |  2.) Member Representation                |
     |<------------------------------------------|
     |                                           |

   1.  The client sends a GET request to the Member's URI to retrieve
       its representation.

   2.  The server responds with the representation of the resource.


5.3.2  Updating a Resource

   Client                                     Server
     |                                           |
     |  1.) PUT to Member URI                    |
     |------------------------------------------>|
     |                                           |
     |  2.) 200 OK                               |
     |<------------------------------------------|

   1.  The client PUTs an updated representation to the Member's URI.

   2.  Upon a successful update of the resource the server responds with
       a status code of 200.


5.3.3  Deleting a Resource

   Client                                     Server
     |                                           |
     |  1.) DELETE to Member URI                 |
     |------------------------------------------>|
     |                                           |
     |  2.) 200 Ok                               |
     |<------------------------------------------|
     |                                           |

   1.  The client sends a DELETE request to the Member's URI.

   2.  Upon the successful deletion of the resource the server responds
       with a status code of 200.



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5.4  Listing Collection Members

   To list the members of a Collection the client sends a GET request to
   the Collection's URI.  An Atom Feed Document is returned containing
   one Atom Entry for each member resource.  See Section 9 and
   Section 10 for a description of the feed contents.

   Client                          Server
     |                                |
     |  1.) GET to Collection URI     |
     |------------------------------->|
     |                                |
     |  2.) 200 OK, Atom Feed Doc     |
     |<-------------------------------|
     |                                |

   1.  The client sends a GET request to the Collection's URI.

   2.  The server responds with an Atom Feed Document containing the
       IRIs of the collection members.


5.5  Use of HTTP Response codes

   The Atom Protocol uses the response status codes defined in HTTP to
   indicate the success or failure of an operation.  Consult the HTTP
   specification [RFC2616] for detailed definitions of each status code.
   It is RECOMMENDED that entities contained within HTTP 4xx and 5xx
   responses include an explanation of the error using natural language.






















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6.  XML-related Conventions

   The Atom Protocol Introspection format is specified in terms of the
   XML Information Set [W3C.REC-xml-infoset-20040204], serialised as XML
   1.0 [W3C.REC-xml-20040204].  Atom Publishing Protocol Documents MUST
   be well-formed XML.  This specification does not define any DTDs for
   Atom Protocol, and hence does not require them to be "valid" in the
   sense used by XML.

6.1  Referring to Information Items

   This specification uses a shorthand for two common terms: the phrase
   "Information Item" is omitted when discussing Element Information
   Items and Attribute Information Items.  Therefore, when this
   specification uses the term "element," it is referring to an Element
   Information Item in Infoset terms.  Likewise, when it uses the term
   "attribute," it is referring to an Attribute Information Item.

6.2  XML Namespace Usage

   The namespace name [W3C.REC-xml-names-19990114] for the XML format
   described in this specification is:

   http://purl.org/atom/app#

   This specification uses the prefix "app:" for the namespace name.
   The choice of namespace prefix is not semantically significant.

   This specification also uses the prefix "atom:" for
   "http://www.w3.org/2005/Atom", the namespace name of the Atom
   Publishing Format [RFC4287].

6.3  Use of xml:base and xml:lang

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



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   appCommonAttributes =
      attribute xml:base { atomUri }?,
      attribute xml:lang { atomLanguageTag }?,
      undefinedAttribute*


6.4  RELAX NG Schema

   Some sections of this specification are illustrated with fragments of
   a non-normative RELAX NG Compact schema [RNC].  A complete schema
   appears in Appendix B.  However, the text of this specification
   provides the definition of conformance.







































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7.  Introspection Documents

   For authoring to commence, a client needs to first discover the
   capabilities and locations of collections offered.  This is done
   using Introspection Documents.  An Introspection Document describes
   workspaces, which are server-defined groupings of collections.

   Introspection documents are identified with the "application/
   atomserv+xml" media type (see Section 15).

   While an introspection document allows multiple workspaces, there is
   no requirement that a service support multiple workspaces.  In
   addition, a collection MAY appear in more than one workspace.

7.1  Example

   <?xml version="1.0" encoding='utf-8'?>
   <service xmlns="http://purl.org/atom/app#">
     <workspace title="Main Site" >
       <collection
         title="My Blog Entries"
         href="http://example.org/reilly/main" >
         <member-type>entry</member-type>
       </collection>
       <collection
         title="Pictures"
         href="http://example.org/reilly/pic" >
         <member-type>media</member-type>
       </collection>
     </workspace>
     <workspace title="Side Bar Blog">
       <collection title="Remaindered Links"
         href="http://example.org/reilly/list" >
         <member-type>entry</member-type>
       </collection>
     </workspace>
   </service>

   This Introspection Document describes two workspaces.  The first,
   called "Main Site", has two collections called "My Blog Entries" and
   "Pictures" whose URIs are "http://example.org/reilly/main" and
   "http://example.org/reilly/pic" respectively.  "My Blog Entries" is
   an Entry collection and "Pictures" is a Media collection.  Entry and
   Media collections are discussed in Section 7.2.4.

   The second workspace is called "Side Bar Blog" and has a single
   collection called "Remaindered Links" whose collection URI is
   "http://example.org/reilly/list".  "Remaindered Links" is an Entry



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   collection.

7.2  Element Definitions

7.2.1  The "app:service" Element

   The root of an introspection document is the "app:service" element.

   The "app:service" element is the container for introspection
   information associated with one or more workspaces.  An app:service
   element MUST contain one or more app:workspace elements.


   namespace app = "http://purl.org/atom/app#"
   start = appService


   appService =
      element app:service {
         appCommonAttributes,
         ( appWorkspace+
           & extensionElement* )
      }


7.2.2  The "app:workspace" Element

   The "app:workspace" element contains information elements about the
   collections of resources available for editing.  The app:workspace
   element MUST contain one or more app:collection elements.


   appWorkspace =
      element app:workspace {
         appCommonAttributes,
         attribute title { text },
         ( appCollection+
           & extensionElement* )
      }


   In an app:workspace element, the first app:collection element of each
   type MUST refer to the preferred or primary collection.  In the
   following example, the "Entries" collection would be considered the
   preferred (or primary) entries collection of the workspace and the
   "Photos" collection would be considered the primary media collection:





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      <service>
        <workspace title="My Blog">
          <collection title="Entries"
               href="http://example.org/myblog/entries">
           <member-type>entry</member-type>
          </collection>
          <collection title="Photos"
               href="http://example.org/myblog/fotes">
           <member-type>media</member-type>
          </collection>
        </workspace>
      </service>


7.2.2.1  The "title" Attribute

   The app:workspace element MUST contain a "title" attribute, which
   gives a human-readable name for the workspace.  This attribute is
   Language-Sensitive.

7.2.3  The "app:collection" Element

   The "app:collection" describes an Atom Protocol collection.  One
   child element is defined here for app:collection: "app:member-type".


   appCollection =
      element app:collection {
         appCommonAttributes,
         attribute title { text },
         attribute href { text },
         ( appMemberType
           & appListTemplate
           & extensionElement* )
      }


7.2.3.1  The "title" Attribute

   The app:collection element MUST contain a "title" attribute, whose
   value gives a human-readable name for the collection.  This attribute
   is Language-Sensitive.

7.2.3.2  The "href" Attribute

   The app:collection element MUST contain a "href" attribute, whose
   value gives the IRI of the collection.




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7.2.4  The "app:member-type" Element

   The app:collection element MUST contain one "app:member-type"
   element.  The app:member-type element value specifies the types of
   members that can appear in the collection.


   appMemberType =
      element app:member-type {
            appCommonAttributes,
            ( appTypeValue )
      }

   appTypeValue = "entry" | "media"


   This specification defines two values for the app:member-type
   element:

   o  "entry" - Indicates the collection contains only member resources
      whose representation MUST be an Atom Entry.  Further constraints
      on the representations of members in a collection of type "entry"
      are listed in Section 8.2.

   o  "media" - Indicates the collection contains member resources whose
      representation can be of any media type.  Additional constraints
      are listed in Section 8.3.
























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8.  Collections

8.1  Creating resources with POST

   To add members to a collection, clients send POST requests to the
   collection's URI.  Collections MAY impose constraints on the media-
   types that are created in a collection and MAY generate a response
   with a status code of 415 ("Unsupported Media Type").  On successful
   creation, the response to the POST request MUST return a Location:
   header with the URI of the newly created resource.

8.1.1  Example

   Below, the client sends a POST request containing an Atom Entry
   representation to the URI of the Collection:

   POST /myblog/entries HTTP/1.1
   Host: example.org
   User-Agent: Thingio/1.0
   Content-Type: application/atom+xml
   Content-Length: nnn

   <entry xmlns="http://www.w3.org/2005/Atom">
     <title>Atom-Powered Robots Run Amok</title>
     <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
     <updated>2003-12-13T18:30:02Z</updated>
     <content>Some text.</content>
   </entry>


   The server signals a successful creation with a status code of 201
   and the response includes a 'Location' header indicating the URI of
   the Atom Entry.

   HTTP/1.1 201 Created
   Date: Fri, 7 Oct 2005 17:17:11 GMT
   Content-Length: 0
   Location: http://example.org/edit/first-post.atom


8.1.2  Title: Header

   A POST to a Media Collection creating a resource SHOULD contain a
   Title: header that indicates the client's suggested title for the
   resource:






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     POST /myblog/fotes HTTP/1.1
     Host: example.org
     User-Agent: Thingio/1.0
     Content-Type: image/png
     Content-Length: nnnn
     Title: An Atom-Powered Robot

     ...binary data...

   The server MAY ignore the content of the Title: header or modify the
   suggested title.

      Title = "Title" ":" [TEXT]

   The syntax of this header MUST conform to the augmented BNF grammar
   in section 2.1 of the HTTP/1.1 specification [RFC2616].  The [TEXT]
   rule is described in section 2.2 of the same document.  Words of
   *TEXT MAY contain characters from character sets other than
   [ISO88591] only when encoded according to the rules of
   [RFC2047].

8.2  Entry Collections

   Entry Collections are collections that restrict their membership to
   Atom Entries.  They are identified by having an app:member-type of
   "entry".  Every member representation MAY contain an atom:link
   element with a link relation of "edit" that contains the IRI of the
   member resource.  Member representations MAY contain a pub:control
   element (Section 11).

8.2.1  Editing entries with foreign markup

   To avoid unintentional loss of data when editing entry collection
   members, Atom Protocol clients SHOULD preserve all metadata,
   including unknown foreign markup, that has not been intentionally
   modified.

8.3  Media Collections

   Media Collections are collections whose member representations are
   not constrained.  They are identified by having an app:member-type of
   "media".

8.3.1  Editing Media Resources

   When listing the contents of a Media Collection, every Entry in the
   Atom Feed Document MUST have an atom:content element with a "src"
   attribute containing the IRI of the media resource itself.  This
   value may be used to update and delete resources as described in



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   Section 5.3.  When creating a public, read-only reference to the
   member resource, a client SHOULD use this value.

8.3.2  Editing Media Metadata

   Entries in a Media Collection MAY contain an atom:link element with a
   link relation of "edit" that contains the IRI of an Atom Entry
   document representing the metadata of the member resource.  A client
   MAY use this to edit the metadata associated with the resource.










































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9.  Listing Collections

   Collection resources MUST provide representations in the form of Atom
   Feed documents.  Each entry in the  Feed Document MUST have an atom:
   link element with a relation of "edit" (See Section 10.1).

   The entries in the returned Atom Feed MUST be ordered by their "atom:
   updated" property, with the most recently updated entries coming
   first in the document order.  Clients SHOULD be constructed in
   consideration that changes which do not alter the entry's
   atom:updated value will not affect the position of the entry in a
   collection.

   Clients MUST NOT assume that an Atom Entry returned in the Feed is a
   full representation of a member resource and SHOULD perform a GET on
   the member resource before editing.

   Collections can contain large numbers of resources.  A naive client
   such as a web spider or web browser could be overwhelmed if the
   response to a GET contained every entry in the collection, and the
   server would waste large amounts of bandwidth and processing time on
   clients unable to handle the response.  For this reason, servers MAY
   return a partial listing containing the most recently updated member
   resources.  Such partial feed documents MUST have an atom:link with a
   "next" relation whose "href" value is the URI of the next partial
   listing of the collection (the least recently updated member
   resources) where it exists.  This is called "collection paging".

9.1  Collection Paging

   Atom Protocol servers MUST provide representations of collections as
   Atom feed documents whose entries represent the collection's members.
   The returned Atom feed MAY NOT contain entries for all the
   collection's members.  Instead, the Atom feed document MAY contain
   link elements with "rel" attribute values of "next", "previous",
   "first" and "last" that can be used to navigate through the complete
   set of matching entries.

   For instance, suppose a client is supplied the URI
   "http://example.org/entries/go" of a collection of member entries,
   where the server as a matter of policy avoids generating feed
   documents containing  more than 10 entries.  The Atom feed document
   for the collection will then represent the first 'page' in a set of
   10 linked feed documents.  The "first" relation will reference the
   initial feed document in the set and the "last" relation references
   the final feed document in the set.  Within each document, the "next"
   and "previous" link relations reference the preceding and subsequent
   documents.



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     <feed xmlns="http://www.w3.org/2005/Atom">
       <link rel="first"
             href="http://example.org/entries/go" />
       <link rel="next"
             href="http://example.org/entries/2" />
       <link rel="last"
             href="http://example.org/entries/10" />
       ...
     </feed>

   The "next" and "previous" link elements for the feed 'page' located
   at "http://example.org/entries/2" would look like this:

     <feed xmlns="http://www.w3.org/2005/Atom">
       <link rel="first"
             href="http://example.org/entries/go" />
       <link rel="previous"
             href="http://example.org/entries/go" />
       <link rel="next"
             href="http://example.org/entries/3" />
       <link rel="last"
             href="http://example.org/entries/10" />
       ...
     </feed>



























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10.  Atom Format Link Relation Extensions

10.1  The "edit" Link Relation

   The Atom Protocol adds the value "edit" to the Atom Registry of Link
   Relations (see section 7.1 of [RFC4287]).  The value of "edit"
   specifies that the IRI in the value of the href attribute is the IRI
   of an editable Atom Entry Document associated with a resource.  In a
   Media Collection this IRI may be used to update the metadata
   associated with a Media Resource.  In an Entry Collection this IRI
   may be used to update and delete the member resource itself.  The
   link relation MAY appear in Atom Entry representations as well as
   Entry and Media Collections.






































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11.  Atom Publishing Control Extensions

11.1  The Atom Publishing Control Namespace

   This specification defines an Atom Format extension for publishing
   control called Atom Publishing Control.  The namespace name for the
   Atom Publishing Control's XML vocabulary is
   "http://example.net/appns/".  This specification uses "pub:" for the
   namespace prefix.  The choice of namespace prefix is not semantically
   significant.

11.2  The "pub:control" Element

   namespace pub = "http://example.net/appns/"

    pubControl =
       element pub:control {
       atomCommonAttributes,
       pubDraft?
       & extensionElement
    }

    pubDraft =
      element pub:draft { "yes" | "no" }

   The "pub:control" element MAY appear as a child of an "atom:entry"
   which is being created or updated via the Atom Publishing Protocol.
   The "pub:control" element, if it does appear in an entry, MUST only
   appear at most one time.  The "pub:control" element is considered
   foreign markup as defined in Section 6 of [RFC4287].

   The "pub:control" element and its child elements MAY be included in
   Atom Feed or Entry Documents.

   The "pub:control" element MAY contain exactly one "pub:draft" element
   as defined here, and MAY contain zero or more extension elements as
   outlined in Section 6 of  [RFC4287].  Both clients and servers MUST
   ignore foreign markup present in the pub:control element.

11.2.1  The "pub:draft" Element

   The number of "pub:draft" elements in "pub:control" MUST be zero or
   one.  Its value MUST be one of "yes" or "no".  A value of "no" means
   that the entry MAY be made publicly visible.  If the "pub:draft"
   element is missing then the value MUST be understood to be "no".  The
   pub:draft element MAY be ignored.





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12.  Atom Publishing Protocol Example

   This is an example of a client creating a new entry with an image.
   The client has an image to publish and an entry that includes an HTML
   "img" element that uses that image.  In this scenario we consider a
   client that has IRIs of two collections, an entry collection and a
   media collection, both of which were discovered through an
   introspection document.  The IRI of the entry collection is:

   http://example.net/blog/edit/

   The IRI of the media collection is:

   http://example.net/binary/edit

   First the client creates a new image resource by POSTing the image to
   the IRI of the media collection.

   POST /binary/edit/ HTTP/1.1
   Host: example.net
   User-Agent: Thingio/1.0
   Content-Type: image/png
   Content-Length: nnnn
   Title: A picture of the beach

   ...binary data...

   The member resource is created and an HTTP status code of 201 is
   returned.

   HTTP/1.1 201 Created
   Date: Fri, 25 Mar 2005 17:17:11 GMT
   Content-Length: nnnn
   Content-Type: application/atom+xml
   Location: http://example.net/binary/edit/b/129.png

   <?xml version="1.0" encoding="utf-8"?>
   <entry xmlns="http://www.w3.org/2005/Atom">
       <title>A picture of the beach</title>
       <link rel="edit"
           href="http://example.net/binary/edit/b/129.png"/>
       <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-568596895695</id>
       <updated>2005-09-02T10:30:00Z</updated>
       <summary>Waves</summary>
       <content type="image/png"
           src="http://example.net/binary/readonly/129.png"/>
   </entry>




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   The client then POSTs the Atom Entry that refers to the newly created
   image resource.  Note that the client takes the URI
   http://example.net/binary/readonly/129.png and uses it in the 'img'
   element in the Entry content:

   POST  /blog/edit/ HTTP/1.1
   Host: example.net
   User-Agent: Thingio/1.0
   Content-Type: application/atom+xml
   Content-Length: nnnn

   <?xml version="1.0" encoding="utf-8"?>
   <entry xmlns="http://www.w3.org/2005/Atom">
       <title>What I did on my summer vacation</title>
       <link href="http://example.org/atom05"/>
       <id>urn:uuid:1225c695-ffb8-4ebb-aaaa-80da354efa6a</id>
       <updated>2005-09-02T10:30:00Z</updated>
       <summary>Beach!</summary>
       <content type="xhtml" xml:lang="en">
           <div xmlns="http://www.w3.org/1999/xhtml">
               <p>We went to the beach for summer vacation.
                   Here is a picture of the waves rolling in:
                   <img
                       src="http://example.net/binary/readonly/129.png"
                       alt="A picture of the beach"
                       />
               </p>
           </div>
       </content>
   </entry>





















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13.  Securing the Atom Protocol

   All instances of publishing Atom Format entries SHOULD be protected
   by authentication to prevent posting or editing by unknown sources.
   Atom Protocol servers and clients MUST support one of the following
   authentication mechanisms, and SHOULD support both.

   o  HTTP Digest Authentication [RFC2617]

   o  CGI Authentication

   Atom Protocol servers and clients MAY support encryption of the
   session using TLS (see [RFC2246]).

   There are cases where an authentication mechanism might not be
   required, such as a publicly editable Wiki, or when using POST to
   send comments to a site that does not require authentication from a
   commenter.

13.1  CGI Authentication

   [[anchor27: note: this section is incomplete; cgi-authentication is
   described but is unspecified.]]  This authentication method is
   included as part of the protocol to allow Atom Protocol servers and
   clients that cannot use HTTP Digest Authentication but where the user
   can both insert its own HTTP headers and create a CGI program to
   authenticate entries to the server.  This scenario is common in
   environments where the user cannot control what services the server
   employs, but the user can write their own HTTP services.






















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14.  Security Considerations

   The security of the Atom Protocol is based on HTTP Digest
   Authentication and/or CGI Authentication [[anchor29: note: refers to
   incomplete section]].  Any weaknesses in either of these
   authentication schemes will affect the security of the Atom
   Publishing Protocol.

   Both HTTP Digest Authentication and CGI Authentication [[anchor30:
   note: refers to incomplete section]] are susceptible to dictionary-
   based attacks on the shared secret.  If the shared secret is a
   password (instead of a random string with sufficient entropy), an
   attacker can determine the secret by exhaustively comparing the
   authenticating string with hashed results of the public string and
   dictionary entries.

   See [RFC2617] for the description of the security properties of HTTP
   Digest Authentication.

   [[anchor31: expand on HTTP basic and digest authentication, or
   refer.]]

   [[anchor32: note: talk here about denial of service attacks using
   large XML files, or the billion laughs DTD attack.]]



























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15.  IANA Considerations

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

   MIME media type name: application

   MIME subtype name: atomserv+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
         [RFC3023].

   Encoding considerations: Identical to those of "application/xml" as
      described in [RFC3023], section 3.2.

   Security considerations: As defined in this specification.
      [[anchor33: update upon publication]]

      In addition, as this media type uses the "+xml" convention, it
      shares the same security considerations as described in [RFC3023],
      section 10.

   Interoperability considerations: There are no known interoperability
      issues.

   Published specification: This specification. [[anchor34: update upon
      publication]]

   Applications that use this media type: No known applications
      currently use this media type.

   Additional information:

   Magic number(s): As specified for "application/xml" in [RFC3023],
      section 3.2.

   File extension: .atomsrv

   Fragment identifiers: As specified for "application/xml" in
      [RFC3023], section 5.






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   Base URI: As specified in [RFC3023], section 6.

   Macintosh File Type code: TEXT

   Person and email address to contact for further information: Joe
      Gregorio <joe@bitworking.org>

   Intended usage: COMMON

   Author/Change controller: This specification's author(s). [[anchor35:
      update upon publication]]








































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16.  References

16.1  Normative References

   [ISO88591]
              ISO, "International Standard -- Information Processing --
              8-bit Single-Byte Coded Graphic Character Sets -- Part 1:
              Latin alphabet No. 1,", January 1987.

   [RFC2047]  Moore, K., "MIME (Multipurpose Internet Mail Extensions)
              Part Three: Message Header Extensions for Non-ASCII Text",
              RFC 2047, November 1996.

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

   [RFC2246]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
              RFC 2246, January 1999.

   [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.

   [RFC2617]  Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
              Leach, P., Luotonen, A., and L. Stewart, "HTTP
              Authentication: Basic and Digest Access Authentication",
              RFC 2617, June 1999.

   [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.

   [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. and R. Sayre, "The Atom Syndication
              Format", RFC 4287, December 2005.

   [W3C.REC-xml-20040204]
              Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T.,
              and E. Maler, "Extensible Markup Language (XML) 1.0 (Third
              Edition)", W3C REC REC-xml-20040204, February 2004.

   [W3C.REC-xml-infoset-20040204]
              Cowan, J., Tobin, R., and A. Layman, "XML Information Set



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              (Second Edition)", W3C REC W3C.REC-xml-infoset-20040204,
              February 2004.

   [W3C.REC-xml-names-19990114]
              Hollander, D., Bray, T., and A. Layman, "Namespaces in
              XML", W3C REC REC-xml-names-19990114, January 1999.

   [W3C.REC-xmlbase-20010627]
              Marsh, J., "XML Base", W3C REC W3C.REC-xmlbase-20010627,
              June 2001.

16.2  Informative References

   [RNC]      Clark, J., "RELAX NG Compact Syntax", December 2001.

   [W3C.REC-webarch-20041215]
              Walsh, N. and I. Jacobs, "Architecture of the World Wide
              Web, Volume One", W3C REC REC-webarch-20041215,
              December 2004.
































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URIs

   [1]  <http://www.imc.org/atom-protocol/index.html>


Authors' Addresses

   Joe Gregorio (editor)
   BitWorking, Inc
   1002 Heathwood Dairy Rd.
   Apex, NC  27502
   US

   Phone: +1 919 272 3764
   Email: joe@bitworking.com
   URI:   http://bitworking.com/


   Bill de hOra (editor)
   Propylon Ltd.
   45 Blackbourne Square, Rathfarnham Gate
   Dublin, Dublin  D14
   IE

   Phone: +353-1-4927444
   Email: bill.dehora@propylon.com
   URI:   http://www.propylon.com/
























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Appendix A.  Contributors

   The content and concepts within are a product of the Atom community
   and the Atompub Working Group.















































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Appendix B.  RELAX NG Compact Schema

   This appendix is informative.

   The Relax NG schema explicitly excludes elements in the Atom Protocol
   namespace which are not defined in this revision of the
   specification.  Requirements for Atom Protocol processors
   encountering such markup are given in Section 6.2 and Section 6.3 of
   [RFC4287].

   # -*- rnc -*-
   # RELAX NG Compact Syntax Grammar for the Atom Protocol

   namespace app = "http://purl.org/atom/app#"
   namespace local = ""

   start = appService

   # common:attrs

   appCommonAttributes =
      attribute xml:base { atomUri }?,
      attribute xml:lang { atomLanguageTag }?,
      undefinedAttribute*

   undefinedAttribute =
     attribute * - (xml:base | xml:lang | local:*) { text }

   atomUri = text

   atomLanguageTag = xsd:string {
      pattern = "[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*"
   }

   # app:service

   appService =
      element app:service {
         appCommonAttributes,
         ( appWorkspace+
           & extensionElement* )
      }

   # app:workspace

   appWorkspace =
      element app:workspace {
         appCommonAttributes,



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         attribute title { text },
         ( appCollection+
           & extensionElement* )
      }

   # app:collection

   appCollection =
      element app:collection {
         appCommonAttributes,
         attribute title { text },
         attribute href { atomUri  },
         ( appMemberType
           & extensionElement* )
      }


   # app:member

   appMemberType =
      element app:member-type {
            appCommonAttributes,
            ( appTypeValue )
      }

   appTypeValue = "entry" | "media"


   # Simple Extension

   simpleExtensionElement =
      element * - app:* {
         text
      }

   # Structured Extension

   structuredExtensionElement =
      element * - app:* {
         (attribute * { text }+,
            (text|anyElement)*)
       | (attribute * { text }*,
          (text?, anyElement+, (text|anyElement)*))
      }

   # Other Extensibility

   extensionElement =



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      simpleExtensionElement | structuredExtensionElement



   # Extensions

   anyElement =
      element * {
         (attribute * { text }
          | text
          | anyElement)*
      }

   # EOF





































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Appendix C.  Revision History

   draft-ietf-atompub-protocol-08: added infoset ref; added wording re
   IRI/URI; fixed URI/IRI ; next/previous fixed as per Atom
   LinkRelations Attribute
   (http://www.imc.org/atom-protocol/mail-archive/msg04095.html);
   incorporated: PaceEditLinkMustToMay; PaceMissingDraftHasNoMeaning,
   PaceRemoveMemberTypeMust, PaceRemoveMemberTypePostMust,
   PaceTitleHeaderOnlyInMediaCollections, PacePreserveForeignMarkup,
   PaceClarifyTitleHeader, PaceClarifyMediaResourceLinks,
   PaceTwoPrimaryCollections;

   draft-ietf-atompub-protocol-07: updated Atom refs to RFC4287;
   incorporated PaceBetterHttpResponseCode;
   PaceClarifyCollectionAndDeleteMethodByWritingLessInsteadOfMore;
   PaceRemoveAcceptPostText; PaceRemoveListTemplate2;
   PaceRemoveRegistry; PaceRemoveWhoWritesWhat;
   PaceSimplifyClarifyBetterfyRemoveBogusValidityText;
   PaceCollectionOrderSignificance; PaceFixLostIntrospectionText;
   PaceListPaging; PaceCollectionControl; element typo in Listing
   collections para3 (was app:member-type, not app:list-template);
   changed post atom entry example to be valid.  Dropped inline use of
   'APP'.  Removed nested diagram from section 4.  Added ed notes in the
   security section.

   draft-ietf-atompub-protocol-06 - Removed: Robert Sayre from the
   contributors section per his request.  Added in
   PaceCollectionControl.  Fixed all the {daterange} verbage and
   examples so they all use a dash.  Added full rnc schema.  Collapsed
   Introspection and Collection documents into a single document.
   Removed {dateRange} queries.  Renamed search to list.  Moved
   discussion of media and entry collection until later in the document
   and tied the discussion to the Introspection element app:member-type.

   draft-ietf-atompub-protocol-05 - Added: Contributors section.  Added:
   de hOra to editors.  Fixed: typos.  Added diagrams and description to
   model section.  Incorporates PaceAppDocuments, PaceAppDocuments2,
   PaceSimplifyCollections2 (large-sized chunks of it anyhow: the
   notions of Entry and Generic resources, the section 4 language on the
   Protocol Model, 4.1 through 4.5.2, the notion of a Collection
   document, as in Section 5 through 5.3, Section 7 "Collection
   resources", Selection resources (modified from pace which talked
   about search); results in major mods to Collection Documents, Section
   9.2 "Title: Header" and brokeout para to section 9.1 Editing Generic
   Resources).  Added XML namespace and language section.  Some cleanup
   of front matter.  Added Language Sensitivity to some attributes.
   Removed resource descriptions from terminology.  Some juggling of
   sections.  See:



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   http://www.imc.org/atom-protocol/mail-archive/msg01812.html.

   draft-ietf-atompub-protocol-04 - Add ladder diagrams, reorganize, add
   SOAP interactions

   draft-ietf-atompub-protocol-03 - Incorporates PaceSliceAndDice3 and
   PaceIntrospection.

   draft-ietf-atompub-protocol-02 - Incorporates Pace409Response,
   PacePostLocationMust, and PaceSimpleResourcePosting.

   draft-ietf-atompub-protocol-01 - Added in sections on Responses for
   the EditURI.  Allow 2xx for response to EditURI PUTs.  Elided all
   mentions of WSSE.  Started adding in some normative references.
   Added the section "Securing the Atom Protocol".  Clarified that it is
   possible that the PostURI and FeedURI could be the same URI.  Cleaned
   up descriptions for Response codes 400 and 500.

   Rev draft-ietf-atompub-protocol-00 - 5Jul2004 - Renamed the file and
   re-titled the document to conform to IETF submission guidelines.
   Changed MIME type to match the one selected for the Atom format.
   Numerous typographical fixes.  We used to have two 'Introduction'
   sections.  One of them was moved into the Abstract the other absorbed
   the Scope section.  IPR and copyright notifications were added.

   Rev 09 - 10Dec2003 - Added the section on SOAP enabled clients and
   servers.

   Rev 08 - 01Dec2003 - Refactored the specification, merging the
   Introspection file into the feed format.  Also dropped the
   distinction between the type of URI used to create new entries and
   the kind used to create comments.  Dropped user preferences.

   Rev 07 - 06Aug2003 - Removed the use of the RSD file for auto-
   discovery.  Changed copyright until a final standards body is chosen.
   Changed query parameters for the search facet to all begin with atom-
   to avoid name collisions.  Updated all the Entries to follow the 0.2
   version.  Changed the format of the search results and template file
   to a pure element based syntax.

   Rev 06 - 24Jul2003 - Moved to PUT for updating Entries.  Changed all
   the mime-types to application/x.atom+xml.  Added template editing.
   Changed 'edit-entry' to 'create-entry' in the Introspection file to
   more accurately reflect its purpose.

   Rev 05 - 17Jul2003 - Renamed everything Echo into Atom.  Added
   version numbers in the Revision history.  Changed all the mime-types
   to application/atom+xml.



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   Rev 04 - 15Jul2003 - Updated the RSD version used from 0.7 to 1.0.
   Change the method of deleting an Entry from POSTing <delete/> to
   using the HTTP DELETE verb.  Also changed the query interface to GET
   instead of POST.  Moved Introspection Discovery to be up under
   Introspection.  Introduced the term 'facet' for the services listed
   in the Introspection file.

   Rev 03 - 10Jul2003 - Added a link to the Wiki near the front of the
   document.  Added a section on finding an Entry.  Retrieving an Entry
   now broken out into its own section.  Changed the HTTP status code
   for a successful editing of an Entry to 205.

   Rev 02 - 7Jul2003 - Entries are no longer returned from POSTs,
   instead they are retrieved via GET.  Cleaned up figure titles, as
   they are rendered poorly in HTML.  All content-types have been
   changed to application/atom+xml.

   Rev 01 - 5Jul2003 - Renamed from EchoAPI.html to follow the more
   commonly used format: draft-gregorio-NN.html.  Renamed all references
   to URL to URI.  Broke out introspection into its own section.  Added
   the Revision History section.  Added more to the warning that the
   example URIs are not normative.





























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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
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Acknowledgment

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















































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