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Network Working Group                                   J. Gregorio, Ed.
Internet-Draft                                           BitWorking, Inc
Expires: April 30, 2006                                  B. de hOra, Ed.
                                                           Propylon Ltd.
                                                        October 27, 2005


                      The Atom Publishing Protocol
                   draft-ietf-atompub-protocol-06.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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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 30, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2005).

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
   (draft-ietf-atompub-format-11.txt).

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 Collections  . . . . . . . . . . . . . . . . . . .  10
     5.5  Success and Failure  . . . . . . . . . . . . . . . . . . .  10
   6.   XML-related Conventions  . . . . . . . . . . . . . . . . . .  11
     6.1  Referring to Information Items . . . . . . . . . . . . . .  11
     6.2  XML Namespace Usage  . . . . . . . . . . . . . . . . . . .  11
     6.3  RELAX NG Schema  . . . . . . . . . . . . . . . . . . . . .  11
     6.4  Use of xml:base and xml:lang . . . . . . . . . . . . . . .  11
   7.   Introspection Documents  . . . . . . . . . . . . . . . . . .  13
     7.1  Introduction . . . . . . . . . . . . . . . . . . . . . . .  13
     7.2  Example  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     7.3  Element Definitions  . . . . . . . . . . . . . . . . . . .  14
       7.3.1  The 'app:service' Element  . . . . . . . . . . . . . .  14
       7.3.2  The 'app:workspace' Element  . . . . . . . . . . . . .  14
       7.3.3  The 'app:collection' Element . . . . . . . . . . . . .  15
       7.3.4  The 'app:member-type' Element  . . . . . . . . . . . .  15
       7.3.5  The 'app:list-template' Element  . . . . . . . . . . .  16
   8.   Collections  . . . . . . . . . . . . . . . . . . . . . . . .  18
     8.1  Creating resources with POST . . . . . . . . . . . . . . .  18
       8.1.1  Title: Header  . . . . . . . . . . . . . . . . . . . .  18
     8.2  Entry Collections  . . . . . . . . . . . . . . . . . . . .  19
       8.2.1  Role of Atom Entry Elements During Editing . . . . . .  19
     8.3  Media Collections  . . . . . . . . . . . . . . . . . . . .  20
       8.3.1  Editing Media Resources  . . . . . . . . . . . . . . .  20
   9.   Listing Collections  . . . . . . . . . . . . . . . . . . . .  21
   10.  Atom Entry Extensions  . . . . . . . . . . . . . . . . . . .  23
     10.1   The 'edit' Link Relation . . . . . . . . . . . . . . . .  23
     10.2   Publishing Control . . . . . . . . . . . . . . . . . . .  23
       10.2.1   The app:draft Element  . . . . . . . . . . . . . . .  24
   11.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   12.  Securing the Atom Protocol . . . . . . . . . . . . . . . . .  27
   13.  Security Considerations  . . . . . . . . . . . . . . . . . .  28
   14.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  29



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   15.  References . . . . . . . . . . . . . . . . . . . . . . . . .  31
     15.1   Normative References . . . . . . . . . . . . . . . . . .  31
     15.2   Informative References . . . . . . . . . . . . . . . . .  32
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  33
   A.   Contributors . . . . . . . . . . . . . . . . . . . . . . . .  34
   B.   RELAX NG Compact Schema  . . . . . . . . . . . . . . . . . .  35
   C.   Revision History . . . . . . . . . . . . . . . . . . . . . .  38
        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 "Atom Protocol"
   or "APP".

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

   URI/IRI - A Uniform Resource Identifier and Internationalized
   Resource Identifier, respectively.  These terms (and the distinction
   between them) are defined in [RFC3986] and [RFC3987].

   resource -  A network data object or service that can be identified
   by a IRI, as defined in [RFC2616].  See [W3C.REC-webarch-20041215]
   for further discussion on resources.

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

   collection - A resource that contains a set of member IRIs, as
   described in Section 8 of this specification.

   member - A resource whose IRI is listed in a collection.

   IRI template - A parameterized string that becomes a IRI when the
   parameters are filled in.  See Section 9.

   introspection document - A document that describes the location and
   capabilities of one or more collections.  See Section 7

   client writable element - An element of an Atom Entry whose value is
   editable by the client and not enforced by the server.

   server-controlled element - An element of an Atom Entry whose value
   is enforced by the server and not editable by the client.















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4.  Protocol Model

   The Atom Publishing Protocol uses HTTP to edit resources on the web.
   It provides a list based mechanism for managing collections of
   editable resources called member resources.  Collections contain the
   IRIs and metadata describing member resources.  The APP uses these
   HTTP verbs:

   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.

   This diagram shows the APP model:

    +---------------+
    | Introspection |   +------------+
    |               |-->| Collection |
    +---------------+   |            |
                        |            |   +--------+
                        |            |-->| Member |
                        |            |   +--------+
                        |            |
                        |            |      .
                        |            |      .
                        |            |      .
                        |            |
                        |            |   +--------+
                        |            |-->| Member |
                        |            |   +--------+
                        |            |
                        +------------+

   The introspection document contains the IRIs of one or more
   collections.  A collection contains IRIs and metadata describing
   member resources.  The protocol allows editing of resources with
   representations of any media-type.  Some types of collections are
   specialized and restrict the resource representations of their
   members.








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5.  Protocol Operations

5.1  Retrieving an Introspection Document

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

   1.  The client sends a GET request to the IRI of the introspection
       document.

   2.  The server responds with the introspection document which
       enumerates the IRIs of all the collections, and the capabilities
       of those collections, that the service supports.


5.2  Creating a Resource

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

   1.  The client POSTs a representation to the IRI 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 IRI of the newly created member resource.


5.3  Editing a Resource

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








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5.3.1  Retrieving a Resource

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

   1.  The client sends a GET request to the member's IRI 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 IRI                    |
     |------------------------------------------>|
     |                                           |
     |  2.) 200 OK                               |
     |<------------------------------------------|

   1.  The client PUTs an updated representation to the member's IRI.

   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 Resource IRI        |
     |------------------------------------------>|
     |                                           |
     |  2.) 200 Ok                               |
     |<------------------------------------------|
     |                                           |

   1.  The client sends a DELETE request to the member's IRI.

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



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   Note: deleting a member also removes it from all the collections to
   which it belongs.

5.4  Listing Collections

   To enumerate the members of a collection the client sends a GET to
   its IRI.  This IRI is constructed from information in the
   introspection document.  An Atom Feed Document is returned with one
   Atom Entry for each member resource that matches the selection
   criteria in the IRI.  See Section 9 and Section 10 for a  description
   of the feed contents.

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

   1.  The client sends a GET request to the membership list IRI.

   2.  The server responds with an Atom Feed Document containing the
       IRIs of all the collection members that match the selection
       criteria.


5.5  Success and Failure

   The Atom Protocol uses HTTP status codes to signal the results of
   protocol operations.  Status codes of the form 2xx signal that a
   request was successful.  HTTP status codes of the form 4xx or 5xx
   signal that an error has occurred.  Consult the HTTP specification
   [RFC2616] for the definitions of HTTP status codes.
















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6.  XML-related Conventions

   The data format in this specification is specified in terms of the
   XML Information Set, 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 naming 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 URI [W3C.REC-xml-names-19990114] for the data format
   described in this specification is:

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

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

   This specification also uses the prefix "atom:" for the Namespace URI
   identified in [AtomFormat].

6.3  RELAX NG Schema

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

6.4  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 [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" 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], .
   appCommonAttributes =
      attribute xml:base { atomUri }?,
      attribute xml:lang { atomLanguageTag }?,
      undefinedAttribute*










































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7.  Introspection Documents

7.1  Introduction

   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.

7.2  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>
         <list-template>http://example.org/{index}</list-template>
       </collection>
       <collection
         title="Pictures"
         href="http://example.org/reilly/pic" >
         <member-type>media</member-type>
         <list-template>http://example.org/p/{index}</list-template>
       </collection>
     </workspace>
     <workspace title="Side Bar Blog">
       <collection title="Remaindered Links"
         href="http://example.org/reilly/list" >
         <member-type>entry</member-type>
         <list-template>http://example.org/l/{index}</list-template>
       </collection>
     </workspace>
   </service>

   This Introspection Document describes two workspaces.  The first,
   called 'Main Site', has two collections called 'My Blog Entries' and
   'Pictures' whose IRIs 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 7.3.4.

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




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   Introspection documents are identified with the "application/
   atomserv+xml" media type (see Section 14).

   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.

7.3  Element Definitions

7.3.1  The 'app:service' Element

   The root of an introspection document is the app:service element.
   namespace app = "http://purl.org/atom/app#"
   start = appService

   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.


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


7.3.2  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* )
      }


7.3.2.1  The 'title' Attribute

   The app:workspace element MUST contain a 'title' attribute, which
   conveys a human-readable name for the workspace.  This attribute is



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   Language-Sensitive.

7.3.3  The 'app:collection' Element

   The app:collection contains information elements that describe the
   location and capabilities of a collection.


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


7.3.3.1  The 'title' Attribute

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

7.3.3.2  The 'href' Attribute

   The app:collection element MUST contain an 'href' attribute, whose
   value conveys the IRI of the collection.

   This specification defines two child elements for app:collection:

   o  app:member-type: a single element that contains the type of
      members that the collection can contain.

   o  app:list-template: a single element that contains a IRI template
      of a membership list.  (See Section 9).


7.3.4  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.







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

   appTypeValue = "entry" | "media"


   An Entry POSTed to a collection MUST meet the constraints of the app:
   member-type element.

   This specification defines two initial values for the app:member-type
   IANA registry:

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

   In general the value of app:member-type MUST be a string that is non-
   empty, and matches either the "isegment-nz-nc" or the "IRI"
   production in [RFC3987].  Note that use of a relative reference other
   than a simple name is not allowed.  If a name is given,
   implementations MUST consider the link relation type to be equivalent
   to the same name registered within the IANA Registry of Link
   Relations Section 14, and thus the IRI that would be obtained by
   appending the value of the rel attribute to the string
   "http://www.iana.org/assignments/member-type/".

7.3.5  The 'app:list-template' Element

   The app:collection element MUST contain one 'app:list-template'
   elements.  The element content of app:list-template is an IRI
   template (Section 9) for a collection.


   appListTemplate =
      element app:list-template {
            appCommonAttributes,
            ( appUriTemplate )
      }

   appUriTemplate = xsd:string { pattern = ".+\{.+\}.*" }



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8.  Collections

8.1  Creating resources with POST

   Every collection accepts POST requests to create resources - the
   client POSTs a representation of the desired resource to the IRI of
   the collection.  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").

   The status code returned for a successful creation POST MUST be 201
   ("Created").

   A successful creation POST MUST return a Location: header with the
   URI of the newly created resource.

   Clients MAY POST invalid Atom for initial resource creation -
   specifically the id and link elements MAY be omitted.

   Below, the client requests to create a resource in a collection:

   POST /edit 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>
       <updated>2003-12-13T18:30:02Z</updated>
       <summary>Some text.</summary>
   </entry>
    The resource is created by sending an Atom Entry as the entity body.

   Successful creation is indicated by a 201 created response and
   includes a Location: header.

   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


8.1.1  Title: Header

   The POST to a collection  MAY contain a Title: header that indicates
   the client's suggested title for the resource.  The server MAY ignore
   the Title: header or modify the requested title.



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   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].

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 MUST contain an atom:link
   element with a relation of rel="edit" that contains the IRI of the
   member resource.  Member representations MAY contain an app:control
   element (Section 10.2).

8.2.1  Role of Atom Entry Elements During Editing

   The elements of an Atom Entry Document are either a client writable
   or server controlled.

   Client Writable - An element of an Atom Entry whose value is editable
   by the client.  Servers MAY modify the content of client writable
   elements.  Some reasons that a server may change client writable
   content include length limits, obscenity filters or the addition of
   boilerplate text.

   Server Controlled - An element of an Atom Entry whose value is
   enforced by the server and not editable by the client.  Clients
   SHOULD NOT change the value of server controlled elements.  Servers
   MUST NOT rely on clients preserving the values of server controlled
   elements.





















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              +--------------------+--------------------+
              | Atom Entry Element |      Property      |
              +--------------------+--------------------+
              |     atom:author    |   Client Writable  |
              |                    |                    |
              |    atom:category   |   Client Writable  |
              |                    |                    |
              |    atom:content    |   Client Writable  |
              |                    |                    |
              |  atom:contributor  |   Client Writable  |
              |                    |                    |
              |       atom:id      |  Server Controlled |
              |                    |                    |
              |      atom:link     |   Client Writable  |
              |                    |                    |
              |   atom:published   |   Client Writable  |
              |                    |                    |
              |     atom:source    |   Client Writable  |
              |                    |                    |
              |    atom:summary    |   Client Writable  |
              |                    |                    |
              |     atom:title     |   Client Writable  |
              |                    |                    |
              |    atom:updated    |  Server Controlled |
              |                    |                    |
              |     app:control    |   Client Writable  |
              +--------------------+--------------------+

                                  Table 1


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 a membership list resource returns an Atom Feed enumerating the
   contents of a Media Collection, all the Entries MUST have an atom:
   content element with a 'src' attribute.  When creating a public,
   read-only reference to the member resource, a client SHOULD use the
   "atom:content/@src" attribute value.







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9.  Listing Collections

   Collections, as identified in an Introspection Document, are
   resources that MUST provide representations in the form of Atom Feed
   documents.  The entries in the returned Feed MUST be ordered by their
   'atom:updated' property, with the most recently updated entries
   coming first in the document order.  Every entry in the Feed Document
   MUST have an atom:link element with a relation of "edit" (See
   Section 10.1).  Clients MUST NOT assume that an Atom Entry returned
   in the Feed is a full representation of a member resource.  The value
   of atom:updated is only changed when the change to a member resource
   is considered significant.  Insignificant changes do not result in
   changes to the atom:updated value and thus do not change the position
   of the corresponding entry in a membership list.  Clients SHOULD be
   constructed with this in mind and SHOULD perform a GET on the member
   resource before editing.

   Collections can contain extremely large numbers of resources.  A
   naive client such as a web spider or web browser would be overwhelmed
   if the response to a GET contained every entry in the feed, and the
   server would waste large amounts of bandwidth and processing time on
   clients unable to handle the response.

   For this reason, Introspection documents refer to collections not
   with IRIs but with IRI Templates, contained in the "app:member-type"
   child of "app:collection".  An IRI Template is a string containing
   the embedded token "{index}".

   To produce an IRI that can be used to retrieve part or all of the
   collection, software replaces the "{index}" with a pair of positive
   integer indices separated by a dash character.  An IRI template MUST,
   after such substitution has been performed, constitute a
   syntactically valid IRI.

   One or other index MAY be omitted, in which case the range is
   understood as stretching to 0 or infinity.  The index values are 0
   based and select members from the collection based on the member's
   index, with all of the members ordered by their 'atom:updated'
   property.  The response to the selection request MUST be an Atom Feed
   where all the entries fall within the requested criteria.  The
   request range is considered a closed set - if an entry matches one
   end of the range exactly it MUST be included in the response.  If no
   members fall in the requested range, the server MUST respond with an
   Atom Feed containing no entries.  If a membership list is returned
   with a number of entries that is less than the number of entries
   requested than the client MAY assume that it has made a request that
   exceeds the last index of the members.




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   For example, suppose the client is supplied this IRI template:

   http://example.org/blog/edit/{index}
    If the client wants the first 15 entries in the collection it would
   substitute the brace-delimited parameter {index}, with the value
   0-14, giving:

   http://example.org/blog/edit/0-14











































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10.  Atom Entry Extensions

   This specification adds one new value to the Registry of Link
   Relations and also adds a new element to Atom Entries called "app:
   control"  for controlling publishing.  These new links and app:
   control elements MAY appear in both membership lists and in member
   representations.

10.1  The 'edit' Link Relation

   This specification adds the value "edit" to the Registry of Link
   Relations.  The value of "edit" signifies that the IRI in the value
   of the href attribute is the IRI of the member resource, and is
   intended to be used to update and delete resources as described in
   this specification.

10.2  Publishing Control

   This specification also adds a new element to Atom Entries for
   controlling publishing.

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

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

   The "app:control" element MAY appear as a child of an "atom:entry"
   which is being created or updated via the Atom Publishing Protocol.
   The "app:control" element, if it does appear in an entry, MUST only
   appear at most one time.

   The "app:control" element and its children elements MAY be included
   in Atom Feed or Entry Documents.  The "app:control" element is
   considered "foreign markup" as defined in Section 6 of the Atom
   Syndication Format.

   The "app:control" element MAY contain exactly one app:draft element
   and MAY contain zero or more extension elements as outlined in the
   Atom Syndication Format, Section 6.  Both clients and servers MUST
   ignore foreign markup present in the app:control element that they do
   not know.





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10.2.1  The app:draft Element

   This specification defines only one child element for "app:control",
   "app:draft".

   The number of "app:draft" elements in "app:control" MUST be zero or
   one.  Its content MUST be one of the values "yes" or "no".  A value
   of "no" means that the entry MAY be made publicly visible.  If the
   "app:draft" element is missing then the value is understood to be
   "no".  That is, if "app:control" and/or the "app:draft" elements are
   missing from an entry then the entry is considered not a draft and
   can be made publicly visible.  Clients MUST understand "app:draft"
   elements and MUST NOT drop them from Atom Entries during editing.
   Clients MUST NOT operate on the expectation that a server will honor
   the value of an "app:draft" element.  Servers MAY ignore "app:draft"
   elements and drop them from Atom Entries.



































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11.  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 IRI
   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>
       <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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12.  Securing the Atom Protocol

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

   o  HTTP Digest Authentication [RFC2617]

   o  [@@TBD@@ CGI Authentication ref]

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

   There are cases where an authentication mechanism is 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.

12.1  [@@TBD@@ CGI Authentication]

   This authentication method is included as part of the protocol to
   allow Atom 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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13.  Security Considerations

   The security of Atom is based on HTTP Digest Authentication and/or
   [@@TBD@@ CGI Authentication].  Any weaknesses in either of these
   authentication schemes will affect the security of the Atom
   Publishing Protocol.

   Both HTTP Digest Authentication and [@@TBD@@ CGI Authentication] 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.

   @@TBD@@ Talk here about using HTTP basic and digest authentication.

   @@TBD@@ Talk here about denial of service attacks using large XML
   files, or the billion laughs DTD attack.






























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14.  IANA Considerations

   An Atom 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.
      [[anchor22: 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. [[anchor23: 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). [[anchor24:
      update upon publication]]








































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15.  References

15.1  Normative References

   [AtomFormat]
              Nottingham, M. and R. Sayre, "The Atom Syndication
              Format",  1.0, July 2005.

   [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.

   [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-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.






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15.2  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 APP namespace
   which are not defined in this revision of the specification.
   Requirements for APP Processors encountering such markup are given in
   Section 6.2 and Section 6.3 of [AtomFormat].

   # -*- 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,
         attribute title { text },



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         ( appCollection+
           & extensionElement* )
      }

   # app:collection

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


   # app:member

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

   appTypeValue = "entry" | "media"

   # app:list-template

   appListTemplate =
      element app:list-template {
            appCommonAttributes,
            ( appUriTemplate )
      }


   # Whatever an IRI template is, it contains at least {index}

   appUriTemplate = xsd:string { pattern = ".+\{index\}.*" }

   # Simple Extension

   simpleExtensionElement =
      element * - app:* {
         text
      }

   # Structured Extension



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

   # Other Extensibility

   extensionElement =
      simpleExtensionElement | structuredExtensionElement



   # Extensions

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

   # EOF


























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Appendix C.  Revision History

   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:
   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



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   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.

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

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
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Acknowledgment

   Funding for the RFC Editor function is currently provided by the
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