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Network Working Group                                   J. Gregorio, Ed.
Internet-Draft                                                       IBM
Expires: April 6, 2007                                   B. de hOra, Ed.
                                                           Propylon Ltd.
                                                        October 03, 2006


                      The Atom Publishing Protocol
                   draft-ietf-atompub-protocol-11.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
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   This Internet-Draft will expire on April 6, 2007.

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
     2.1  XML-related Conventions  . . . . . . . . . . . . . . . . .   5
       2.1.1  Referring to Information Items . . . . . . . . . . . .   5
       2.1.2  RELAX NG Schema  . . . . . . . . . . . . . . . . . . .   5
       2.1.3  Use of xml:base and xml:lang . . . . . . . . . . . . .   5
   3.   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.   Protocol Model . . . . . . . . . . . . . . . . . . . . . . .   7
   5.   Protocol Operations  . . . . . . . . . . . . . . . . . . . .   9
     5.1  Retrieving a Service Document  . . . . . . . . . . . . . .   9
     5.2  Listing Collection Members . . . . . . . . . . . . . . . .   9
     5.3  Creating a Resource  . . . . . . . . . . . . . . . . . . .  10
     5.4  Editing a Resource . . . . . . . . . . . . . . . . . . . .  10
       5.4.1  Retrieving a Resource  . . . . . . . . . . . . . . . .  10
       5.4.2  Updating a Resource  . . . . . . . . . . . . . . . . .  11
       5.4.3  Deleting a Resource  . . . . . . . . . . . . . . . . .  11
     5.5  Use of HTTP Response codes . . . . . . . . . . . . . . . .  11
   6.   Atom Publishing Protocol Documents . . . . . . . . . . . . .  12
     6.1  Document Types . . . . . . . . . . . . . . . . . . . . . .  12
     6.2  Document Extensibility . . . . . . . . . . . . . . . . . .  12
   7.   Category Documents . . . . . . . . . . . . . . . . . . . . .  13
     7.1  Example  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     7.2  Element Definitions  . . . . . . . . . . . . . . . . . . .  13
       7.2.1  The "app:categories" element . . . . . . . . . . . . .  13
   8.   Service Documents  . . . . . . . . . . . . . . . . . . . . .  15
     8.1  Example  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     8.2  Element Definitions  . . . . . . . . . . . . . . . . . . .  17
       8.2.1  The "app:service" Element  . . . . . . . . . . . . . .  17
       8.2.2  The "app:workspace" Element  . . . . . . . . . . . . .  17
       8.2.3  The "app:collection" Element . . . . . . . . . . . . .  18
       8.2.4  The "app:accept" Element . . . . . . . . . . . . . . .  19
       8.2.5  The "app:categories" Element . . . . . . . . . . . . .  20
   9.   Creating and Editing Resources . . . . . . . . . . . . . . .  22
     9.1  Member URIs  . . . . . . . . . . . . . . . . . . . . . . .  22
     9.2  Creating resources with POST . . . . . . . . . . . . . . .  22
       9.2.1  Example  . . . . . . . . . . . . . . . . . . . . . . .  23
     9.3  Updating Resources with PUT  . . . . . . . . . . . . . . .  24
     9.4  Deleting Resources with DELETE . . . . . . . . . . . . . .  24
     9.5  Media Resources and Media Link Entries . . . . . . . . . .  24
     9.6  The Slug: Header . . . . . . . . . . . . . . . . . . . . .  25
       9.6.1  Slug: Header syntax  . . . . . . . . . . . . . . . . .  25
       9.6.2  Examples . . . . . . . . . . . . . . . . . . . . . . .  26
   10.  Listing Collections  . . . . . . . . . . . . . . . . . . . .  28



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     10.1   Collection Paging  . . . . . . . . . . . . . . . . . . .  28
     10.2   The "app:edited" Element . . . . . . . . . . . . . . . .  29
   11.  Atom Format Link Relation Extensions . . . . . . . . . . . .  30
     11.1   The "edit" Link Relation . . . . . . . . . . . . . . . .  30
     11.2   The "edit-media" Link Relation . . . . . . . . . . . . .  30
   12.  Atom Publishing Controls . . . . . . . . . . . . . . . . . .  31
     12.1   The "app:control" Element  . . . . . . . . . . . . . . .  31
       12.1.1   The "app:draft" Element  . . . . . . . . . . . . . .  31
   13.  Securing the Atom Publishing Protocol  . . . . . . . . . . .  32
   14.  Security Considerations  . . . . . . . . . . . . . . . . . .  33
     14.1   Denial of Service  . . . . . . . . . . . . . . . . . . .  33
     14.2   Replay Attacks . . . . . . . . . . . . . . . . . . . . .  33
     14.3   Spoofing Attacks . . . . . . . . . . . . . . . . . . . .  33
     14.4   Linked Resources . . . . . . . . . . . . . . . . . . . .  33
     14.5   Digital Signatures and Encryption  . . . . . . . . . . .  33
     14.6   URIs and IRIs  . . . . . . . . . . . . . . . . . . . . .  33
   15.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  34
     15.1   Content-type registration for
            'application/atomserv+xml' . . . . . . . . . . . . . . .  34
     15.2   Content-type registration for
            'application/atomcat+xml'  . . . . . . . . . . . . . . .  35
     15.3   Header field registration for 'SLUG' . . . . . . . . . .  36
   16.  References . . . . . . . . . . . . . . . . . . . . . . . . .  38
     16.1   Normative References . . . . . . . . . . . . . . . . . .  38
     16.2   Informative References . . . . . . . . . . . . . . . . .  39
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  40
   A.   Contributors . . . . . . . . . . . . . . . . . . . . . . . .  41
   B.   RELAX NG Compact Schema  . . . . . . . . . . . . . . . . . .  42
   C.   Revision History . . . . . . . . . . . . . . . . . . . . . .  48
        Intellectual Property and Copyright Statements . . . . . . .  51





















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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-20060816].  The protocol supports the creation of
   arbitrary web resources and provides facilities for:

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

   o  Service: 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].

2.1  XML-related Conventions

2.1.1  Referring to Information Items

   Atom Protocol Document formats are specified in terms of the XML
   Information Set [W3C.REC-xml-infoset-20040204], serialized as XML 1.0
   [W3C.REC-xml-20060816].

   The Infoset terms "Element Information Item" and "Attribute
   Information Item" are shortened to "element" and "attribute"
   respectively.  Therefore, when this specification uses the term
   "element", it is referring to an Element Information Item, and when
   it uses the term "attribute", it is referring to an Attribute
   Information Item.

2.1.2  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.  Complete
   schemas appear in Appendix B.

2.1.3  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], by establishing the base URI (or IRI) for resolving
   relative references found within the 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-20060816].








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3.  Terminology

   For convenience, this protocol can 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].  Before an IRI found in a
   document is used by HTTP, the IRI is first converted to a URI (see
   Section 4

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

   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.

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

   Collection - A resource that contains a set of Member Entries.  See
   Section 9.

   Member - A resource whose IRI is listed in a Collection by a link
   element with a relation of "edit" or "edit-media".  See Section 9.1.

   Workspace - A group of collections.  See Section 8.

   Service Document - A document that describes the location and
   capabilities of one or more Collections.  See Section 8.

   Category Document - A document that describes the categories allowed
   in a Collection.  See Section 7.
















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4.  Protocol Model

   The Atom Publishing Protocol uses HTTP methods to author Member
   Resources as follows:

   o  GET is used to retrieve a representation of a known resource.

   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 known resource.

   Along with operations on Member Resources the Atom Protocol defines
   Collection resources for managing and organizing Member Resources.
   Collections are represented by Atom Feed documents and contain the
   IRIs of, and metadata about, their Member Resources.

   Atom Protocol documents allow the use of IRIs [RFC3987], as well as
   URIs [RFC3986].  Before an IRI found in a document is used by HTTP,
   the IRI is first converted to a URI according the procedure defined
   in Section 3.1 of [RFC3987].  The resource identified by the URI
   after conversion is the same as the one identified by the IRI.

   There are two kinds of Member Resources - Member Entry Resources and
   Media Resources.  Member Entry Resources are represented as Atom
   Entries [RFC4287].  Media Resources can have representations in any
   media type.  A Media Link Entry is a Member Entry that contains
   metadata about a Media Resource.  This diagram shows the
   classification of the resources:

     Member Resource
         -> Member Entry Resource
              -> Media Link Entry Resource
         -> Media Resource

   Collections, represented by Atom feeds, contain entries.  Those
   entries contain the Member Entry and Media Resources IRIs of the
   Collection.  A Collection can contain any number of entries of either
   kind.  In the diagram of a Collection below there are two entries.
   The first contains the IRI of a Member Entry Resource.  The second
   contains the IRIs of both a Media Resource and a Media Link Entry
   Resource, which contains the metadata for that Media Resource:








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     Collection
        Entry
           Member Entry IRI    ->   Member Entry Resource

        Entry
           Member Entry IRI    ->   Media Link Entry Resource
           Media IRI           ->   Media Resource


   Service Documents represent server-defined groups of Collections, and
   are used to initialize the process of creating and editing resources.








































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5.  Protocol Operations

5.1  Retrieving a Service Document

   Client                                     Server
     |                                           |
     |  1.) GET to Service Document              |
     |------------------------------------------>|
     |                                           |
     |  2.) Service Document                     |
     |<------------------------------------------|
     |                                           |

   1.  The client sends a GET request using the URI of the Service
       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  Listing Collection Members

   To list the members of a Collection, the client sends a GET request
   to the URI of a Collection.  An Atom Feed Document is returned
   containing one Atom Entry for each Member Entry Resource.  See
   Section 10 and Section 11 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 URI of the Collection.

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








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5.3  Creating a Resource

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

   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 IRI of the newly created Member Entry Resource.
       Media Resources may have also been created and their IRIs can be
       found through the Member Entry Resource.  See Section 9.5 for
       more details.


5.4  Editing a Resource

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

5.4.1  Retrieving a Resource

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

   1.  The client sends a GET request to the URI of a Member Resource to
       retrieve its representation.

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








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5.4.2  Updating a Resource

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

   1.  The client PUTs an updated representation to the URI of a Member
       Resource.

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


5.4.3  Deleting a Resource

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

   1.  The client sends a DELETE request to the URI of a Member
       Resource.

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

   A different approach is taken for deleting Media Resources, see
   Section 9.5 for details.

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.
   Implementers are asked to note that per the HTTP specification, HTTP
   4xx and 5xx response entities SHOULD include a human-readable
   explanation of the error.






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6.  Atom Publishing Protocol Documents

6.1  Document Types

   This specification describes two kinds of Documents - Category
   Documents and Service Documents.

   A Category Document (Section 7) contain lists of categories specified
   using the "atom:category" element from the Atom Syndication Format.
   A Service Document (Section 8) describes capabilities of workspaces,
   which are server-defined groupings of Collections.

   The namespace name [W3C.REC-xml-names-20060816] for either kind of
   document is:
       http://purl.org/atom/app#

   [[anchor8: Needs to be updated with the final URI upon publication]]

   This specification uses the prefix "app:" for the namespace name.
   The prefix "atom:" is used for "http://www.w3.org/2005/Atom", the
   namespace name of the Atom Syndication Format [RFC4287].  The
   namespace prefixes are not semantically significant.

   Atom Publishing Protocol Documents MUST be well-formed XML.  This
   specification does not define any DTDs for Atom Protocol formats, and
   hence does not require them to be "valid" in the sense used by XML.

6.2  Document Extensibility

   Unrecognized markup in an Atom Publishing Protocol document is
   considered "foreign markup" as defined in [RFC4287].  Such foreign
   markup can be used anywhere within a Category or Service Document
   unless it is explicitly forbidden.  Processors that encounter foreign
   markup MUST NOT stop processing or signal an error, and SHOULD
   preserve foreign markup when transmitting such documents.

   The namespace name "http://purl.org/atom/app#" is reserved for
   forward compatible revisions of the Category and Service Document
   types - this does not exclude the addition of elements and attributes
   that might not be recognised by processors conformant to this
   specification.  Such unrecognised markup from the
   "http://purl.org/atom/app#" namespace MUST be treated as foreign
   markup.








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7.  Category Documents

   Category Documents contain lists of categories described using the
   "atom:category" element from the Atom Syndication Format [RFC4287].
   Categories can also appear in Service Documents and describe the
   categories allowed in a Collection (see Section 8.2.5).

   Category Documents are identified with the "application/atomcat+xml"
   media type (see Section 15).

7.1  Example

       <?xml version="1.0" ?>
       <app:categories
           xmlns:app="http://purl.org/atom/app#"
           xmlns="http://www.w3.org/2005/Atom"
           fixed="yes" scheme="http://example.com/cats/big3">
         <category term="animal" />
         <category term="vegetable" />
         <category term="mineral" />
       </app:categories>

   This Category Document contains three categories, with the terms
   "animal", "vegetable", and "mineral".  None of the categories use the
   'label' attribute defined in [RFC4287].  They all inherit the
   "http://example.com/cats/big3" 'scheme' attribute declared on the
   app:categories element.  Therefore if the "mineral" category were to
   appear in an Atom Entry or Feed Document, it would appear as:

       <category scheme="http://example.com/cats/big3" term="mineral" />


7.2  Element Definitions

7.2.1  The "app:categories" element

   The root of a Category Document is the "app:categories" element.  An
   app:categories element can contain zero or more "atom:category"
   elements from the Atom namespace ("http://www.w3.org/2005/Atom").

   An app:category child element that has no "scheme" attribute inherits
   the attribute from its app:categories parent.  An app:category child
   element with an existing "scheme" attribute does not inherit the
   "scheme" value of its "app:categories" parent element.

7.2.1.1  Attributes of "app:categories"

   The app:categories element can contain a "fixed" attribute, with a



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   value of either "yes" or "no", indicating whether the list of
   categories is a fixed or an open set.  Newly created or updated
   members whose categories are not listed in the Collection Document
   MAY be rejected by the server.  Collections that indicate the set is
   open SHOULD NOT reject otherwise acceptable members whose categories
   are not listed in the Collection.

   Alternatively, the app:categories element MAY contain an "href"
   attribute, whose value MUST be an IRI reference identifying a
   Category Document.  If the "href" attribute is provided the app:
   categories element MUST be empty and MUST NOT have the "fixed" or
   "scheme" attributes.


   atomCategory =
       element atom:category {
          atomCommonAttributes,
          attribute term { text },
          attribute scheme { atomURI }?,
          attribute label { text }?,
          undefinedContent
       }

   appInlineCategories =
       element app:categories {
           attribute fixed { "yes" | "no" }?,
           attribute scheme { atomURI }?,
           (atomCategory*)
       }

   appOutOfLineCategories =
       element app:categories {
           attribute href { atomURI },
           undefinedContent
       }

   appCategories = appInlineCategories | appOutOfLineCategories














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8.  Service Documents

   For authoring to commence, a client needs to first discover the
   capabilities and locations of the available collections.  Service
   Documents are designed to support this discovery process.  How
   Service Documents are in turn discovered is not defined in this
   specification.

   A Service Document describes workspaces, which are server-defined
   groupings of Collections.  Service Documents are identified with the
   "application/atomserv+xml" media type (see Section 15).

   There is no requirement that a server support multiple workspaces.
   In addition, a Collection MAY appear in more than one Workspace.





































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8.1  Example

   <?xml version="1.0" encoding='utf-8'?>
   <service xmlns="http://purl.org/atom/app#"
            xmlns:atom="http://www.w3.org/2005/Atom">
     <workspace>
       <atom:title>Main Site</atom:title>
       <collection
           href="http://example.org/reilly/main" >
         <atom:title>My Blog Entries</atom:title>
         <categories
            href="http://example.com/cats/forMain.cats" />
       </collection>
       <collection
           href="http://example.org/reilly/pic" >
         <atom:title>Pictures</atom:title>
         <accept>image/*</accept>
       </collection>
     </workspace>
     <workspace>
       <atom:title>Side Bar Blog</atom:title>
       <collection
           href="http://example.org/reilly/list" >
         <atom:title>Remaindered Links</atom:title>
         <accept>entry</accept>
         <categories fixed="yes">
           <atom:category
             scheme="http://example.org/extra-cats/"
             term="joke" />
           <atom:category
             scheme="http://example.org/extra-cats/"
             term="serious" />
         </categories>
       </collection>
     </workspace>
   </service>

   This Service Document describes two workspaces.  The first Workspace
   is 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.  The "Pictures"
   Workspace includes an "accept" element indicating that a client can
   post image files to the Collection to create new entries.  Entries
   with associated media resources are discussed in Section 9.5.

   The second Workspace is called "Side Bar Blog" and has a single
   Collection called "Remaindered Links" whose IRI is
   "http://example.org/reilly/list".



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   Within each of the two entry collections, the categories element
   provides a list of available categories for member entries.  In the
   "My Blog Entries" Collection, the list of available categories is
   obtainable through the "href" attribute.  The "Side Bar Blog"
   Collection provides a category list within the Service Document, but
   states the list is fixed, signaling a request from the server that
   entries be posted using only those two categories.

8.2  Element Definitions

8.2.1  The "app:service" Element

   The root of a Service Document is the "app:service" element.

   The "app:service" element is the container for service 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* )
      }


8.2.2  The "app:workspace" Element

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


   appWorkspace =
      element app:workspace {
         appCommonAttributes,
         ( atomTitle
           & appCollection*
           & extensionElement* )
      }

   atomTitle = element atom:title { atomTextConstruct }




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   In an app:workspace element, the first app:collection element MUST
   refer to the preferred or primary Collection.  This distinction is
   considered useful in scenarios where Members and Media Link Entries
   are POSTed to different Collections.  In the following example, the
   "Eintragungen" collection would be considered the preferred
   Collection:

       <service xmlns="http://purl.org/atom/app#"
        xmlns:atom="http://www.w3.org/2005/Atom">
         <workspace xml:lang="de">
           <atom:title>Das Blog</atom:title>
           <collection
                href="http://example.org/blog/eintragungen" >
             <atom:title>Eintragungen</atom:title>
          </collection>
           <collection
                href="http://example.org/blog/fotos">
              <atom:title>Fotos</atom:title>
              <accept>image/*</accept>
           </collection>
         </workspace>
       </service>

8.2.2.1  The "atom:title" Element

   The app:workspace element MUST contain one "atom:title" element (as
   defined in [RFC4287]), giving a human-readable title for the
   workspace.

8.2.3  The "app:collection" Element

   The "app:collection" element describes a Collection.  The app:
   collection element MAY contain one app:accept element and MAY contain
   any number of app:categories elements.  The app:collection element
   MUST NOT contain more than one app:accept element.


   appCollection =
      element app:collection {
         appCommonAttributes,
         attribute href { atomURI  },
         ( atomTitle
           & appAccept?
           & appCategories*
           & extensionElement* )
      }





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8.2.3.1  Usage in Atom Feed Documents

   The app:collection element MAY appear as a child of an atom:feed or
   atom:source element in an Atom Feed Document.  Its value identifies a
   Collection by which new entries can be added to appear in the feed.
   The app:control element is considered foreign markup as defined in
   Section 6 of [RFC4287].

8.2.3.2  The "href" Attribute

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

8.2.3.3  The "atom:title" Element

   The app:collection Element MUST contain one "atom:title" element,
   giving a human-readable title for the Workspace.

8.2.4  The "app:accept" Element

   The "app:accept" element value specifies a comma-separated list of
   media-ranges (see [RFC2616]) identifying the types of representations
   that can be POSTed to the URI of a Collection.  Whitespace around and
   between media-range values is considered insignificant and MUST be
   ignored.

   The app:accept element is similar to the HTTP Accept request-header
   [RFC2616] with the exception that app:accept has no notion of
   preference.  As a result, the value syntax of app:accept does not use
   "accept-params" or "q" arguments as specified in [RFC2616], section
   14.1.

   The order of media-ranges is not significant.  The following lists
   are all equivalent:


     <app:accept>image/png,image/*</app:accept>
     <app:accept>image/*, image/png</app:accept>
     <app:accept> image/* </app:accept>

   A value of "entry" may appear in any list of media-ranges in an
   accept element and indicates that Atom Entry Documents can be posted
   to the Collection.  If the accept element is omitted or empty,
   clients SHOULD assume that only Atom Entry documents will be accepted
   by the Collection.






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   appAccept =
      element app:accept {
            appCommonAttributes,
            ( appTypeValue? )
      }


   appTypeValue = ( "entry" | media-type |entry-or-media-type  )
   media-type = xsd:string { pattern = "entry,(.+/.+,?)*" }
   entry-or-media-type = xsd:string { pattern = "(.+/.+,?)*" }


8.2.5  The "app:categories" Element

   The "app:categories" element provides a listing of the categories
   that can be applied to the members of a Collection.


   atomCategory =
       element atom:category {
          atomCommonAttributes,
          attribute term { text },
          attribute scheme { atomURI }?,
          attribute label { text }?,
          undefinedContent
       }

   appInlineCategories =
       element app:categories {
           attribute fixed { "yes" | "no" }?,
           attribute scheme { atomURI }?,
           (atomCategory*)
       }

   appOutOfLineCategories =
       element app:categories {
           attribute href { atomURI },
           undefinedContent
       }

   appCategories = appInlineCategories | appOutOfLineCategories


   The app:categories element MAY contain a "fixed" attribute, with a
   value of either "yes" or "no", indicating whether or not the listing
   of categories is considered to be a fixed, or closed set.  The
   absence of the "fixed" attribute is equivalent to the presence of a
   "fixed" attribute with a value of "no".  Collections that indicate a



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   fixed set MAY reject members that include categories not specified in
   the provided listing.  Collections that indicate an open set SHOULD
   NOT reject otherwise acceptable members whose categories are not
   present in the provided list.

   The app:categories element MAY contain an "href" attribute, whose
   value MUST be an IRI reference identifying a Category Document.  If
   the "href" attribute is provided, the app:categories element MUST be
   empty and the "fixed" and "scheme" attributes MUST NOT be present.










































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9.  Creating and Editing Resources

9.1  Member URIs

   The Member URI supports retrieving, updating and deleting the
   resource using HTTP GET, PUT and DELETE as described in this section.
   Retrieval and updating of Member Entry Resources are done via Atom
   Entry representations.

   Member Entry URIs appear in two places.  First, they are returned in
   a Location header after successful resource creation using POST, as
   described below.  Second, in the entries of a Collection document, by
   an atom:link element with a link relation of "edit".

   Each Member Entry SHOULD contain such an atom:link element providing
   its Member Entry URI.

9.2  Creating resources with POST

   To add members to a Collection, clients send POST requests to the URI
   of a Collection.  Successful member creation is normally indicated
   with a 201 ("Created") response code.  Collections MAY generate a
   response with a status code of 415 ("Unsupported Media Type") to
   indicate media-type of POSTed entity is not allowed or supported by
   the Collection.

   When a Member Resource is created in the Collection which received
   the POST, its Member Entry URI MUST be returned in an HTTP Location
   header.

   When the server generates a response with a status code of 201
   ("Created"), it SHOULD also return a response body, which if
   provided, MUST be an Atom Entry Document representing the newly-
   created resource.

   Since the server is free to alter the posted entry, for example by
   changing the content of the "id" element, returning the Entry as
   described in the previous paragraph can be useful to the client,
   enabling it to correlate the client and server views of the new
   Entry.

   When the POST request contains an Atom Entry Document, the response
   from the server SHOULD contain a Content-Location header that
   contains the same character-by-character value as the Location
   header.

   The request body sent with the POST need not be an Atom Entry.  For
   example, it might be a picture, or a movie.  For a discussion of the



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   issues in posting such content, see Section 9.5.

9.2.1  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
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Type: application/atom+xml
       Content-Length: nnn
       Slug: First Post

       <?xml version="1.0" ?>
       <entry xmlns="http://www.w3.org/2005/Atom"
           xmlns:app="http://purl.org/atom/app#">
         <title>Atom-Powered Robots Run Amok</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <updated>2003-12-13T18:30:02Z</updated>
         <author><name>John Doe</name></author>
         <content>Some text.</content>
       </entry>


   The server signals a successful creation with a status code of 201.
   The response includes a "Location" header indicating the Member Entry
   URI of the Atom Entry and a representation of that Entry in the body
   of the response.

       HTTP/1.1 201 Created
       Date: Fri, 7 Oct 2005 17:17:11 GMT
       Content-Length: nnn
       Content-Type: application/atom+xml; charset="utf-8"
       Content-Location: http://example.org/edit/first-post.atom
       Location: http://example.org/edit/first-post.atom

       <?xml version="1.0"?>
       <entry xmlns="http://www.w3.org/2005/Atom"
           xmlns:app="http://purl.org/atom/app#">
         <title>Atom-Powered Robots Run Amok</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <updated>2003-12-13T18:30:02Z</updated>
         <author><name>John Doe</name></author>
         <content>Some text.</content>
         <link rel="edit"
             href="http://example.org/edit/first-post.atom"/>



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       </entry>


   The Entry created and returned by the server might not match the
   Entry POSTed by the client.  A server MAY change the values of
   various elements in the Entry such as the atom:id, atom:updated and
   atom:author values and MAY choose to remove or add other elements and
   attributes, or change element and attribute values.

   In particular, the publishing system in this example filled in some
   values not provided in the original POST.  For example, it
   ascertained the name of the author, presumably via the authentication
   protocol used to establish the right to post.

9.3  Updating Resources with PUT

   To update a resource, clients send PUT requests to its Member URI, as
   specified in [RFC2616].

   To avoid unintentional loss of data when editing Member Entries or
   Media Link Entries, Atom Protocol clients SHOULD preserve all
   metadata that has not been intentionally modified, including unknown
   foreign markup as defined in Section 6 of [RFC4287].

9.4  Deleting Resources with DELETE

   To delete a resource, clients send DELETE requests to its Member URI,
   as specified in [RFC2616].  For Media Resources, deletion of a Media
   Link Entry SHOULD result in the deletion of the associated Media
   Resource.

9.5  Media Resources and Media Link Entries

   A client can POST a media type other than application/atom+xml to a
   Collection.  Such a request creates two new resources - one that
   corresponds to the entity sent in the request, called the Media
   Resource, and an associated Member Entry, called the Media Link
   Entry.  Media Link Entries are represented as Atom Entries.  The
   server can signal the media types it will accept via the "accept"
   element in the Service Document (Section 8.2.4).

   The Media Link Entry contains the IRI of the Media Resource and makes
   metadata about it separately available for retrieval and update.  The
   Media Link Entry is used to store metadata about the (perhaps non-
   textual) Media Resource.

   Successful responses to creation requests MUST include the URI of the
   Media Link Entry in the Location header.  The Media Link Entry SHOULD



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   contain an atom:link element with a link relation of "edit-media"
   that contains the Media Resource IRI.  The Media Link Entry MUST have
   an "atom:content" element with a non-empty "src" attribute.  The
   value of the "src" attribute is an IRI of the newly created Media
   Resource.  It is OPTIONAL that the IRI of the "src" attribute on the
   atom:content element be the same as the Media Resource IRI.  That is,
   the "src" attribute value might instead be a link into a static cache
   or content distribution network and not be the Media Resource IRI.

   Implementers are asked to note that according to the requirements of
   [RFC4287], entries, and thus Media Link Entries, MUST contain an
   atom:summary element.  Upon successful creation of a Media Link
   Entry, a server MAY choose to populate the atom:summary element (as
   well as other required elements such as atom:id, atom:author and
   atom:title) with content derived from the POSTed entity or from any
   other source.  A server might not allow a client to modify the server
   selected values for these elements.

   For resource creation this specification only defines cases where the
   POST body has an Atom Entry entity declared as an Atom media type
   ("application/atom+xml"), or a non-Atom entity declared as a non-Atom
   media type.  It does not specify any request semantics or server
   behavior in the case where the POSTed media-type is "application/
   atom+xml" but the body is something other than an Atom Entry.  In
   particular, what happens on POSTing an Atom Feed Document to a
   Collection using the "application/atom+xml" media type is undefined.

9.6  The Slug: Header

   Slug is a HTTP entity-header whose value is a "slug" - a short name
   that can be used as part of the URI for a Member Resource.

   When posting an entity to a Collection to add a new Member, the
   server MAY use this information when creating the Member URI of the
   newly-created resource, for instance by using some or all of the
   words in the last URI segment.  It MAY also use it when creating the
   atom:id or as the title of a Media Link Entry (see Section 9.5.).

   Servers MAY ignore the Slug entity-header and MAY alter its value
   before using it.  For example, the server MAY filter out some
   characters or replace accented letters with non-accented ones, spaces
   with underscores, etc.

9.6.1  Slug: Header syntax

   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.



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       Slug = "Slug" ":" *TEXT

   Clients MAY send non-ASCII characters in the Slug entity-header,
   which they MUST encode using "encoded-words", as defined in
   [RFC2047].  Servers SHOULD treat the slug as [RFC2047] encoded if it
   matches the "encoded-words" production.

9.6.2  Examples

   Below, the client sends a POST request containing a PNG image to the
   URI of the Collection:


       POST /myblog/entries HTTP/1.1
       Host: example.org
       Content-Type: image/png
       Slug: The Beach
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Length: nnn

       ...binary data...

   The server signals a successful creation with a status code of 201.
   The response includes a Location header indicating the Member URI of
   the Media Link Entry and a representation of that entry in the body
   of the response.  The Media Link Entry includes a content element
   with a src attribute, and a link using the link relation "edit-media"
   specifying the IRI to be used for modifying the Media Resource.























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       HTTP/1.1 201 Created
       Date: Fri, 7 Oct 2005 17:17:11 GMT
       Content-Length: nnn
       Content-Type: application/atom+xml; charset="utf-8"
       Content-Location: http://example.org/myblog/edit/the_beach
       Location: http://example.org/myblog/edit/the_beach

       <?xml version="1.0"?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>The Beach</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <updated>2005-10-07T17:17:08Z</updated>
         <author><name>Daffy</name></author>
         <summary type="text" />
         <content type="image/png"
            src="http://example.org/media/the_beach.png"/>
         <link rel="edit-media"
            href="http://example.org/media/edit/the_beach.png" />
         <link rel="edit"
            href="http://example.org/myblog/edit/the_beach />
       </entry>

   Here is an example of the Slug: header that uses the encoding rules
   of [RFC2047].


       POST /myblog/entries HTTP/1.1
       Host: example.org
       Content-Type: image/png
       Slug: =?iso-8859-1?q?The_Beach?=
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Length: nnn

       ...binary data...

   See Section 9.2.1 for an example of the Slug: header applied to the
   creation of a Member Entry Resource.














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10.  Listing Collections

   Collection resources MUST provide representations in the form of Atom
   Feed documents whose entries represent the Members in the Collection.
   Each entry in the Feed Document SHOULD have an atom:link element with
   a relation of "edit" (See Section 11.1).

   The entries in the returned Atom Feed SHOULD 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 of the fact that changes which do not alter the atom:
   updated value of an entry 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 Entry Resource and SHOULD perform a
   GET on the URI of the Member Entry before editing.

10.1  Collection Paging

   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 of 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 next most recently updated Member
   Resources) where it exists.  This is called "Collection paging".

   The returned Atom Feed MAY contain a subset the Member Entries for a
   Collection.  In addition, 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 Atom 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>


10.2  The "app:edited" Element

   The "app:edited" element is a Date construct as defined by [RFC4287]
   whose value indicates the most recent instant in time when an entry
   was edited, including when created.  Atom entry elements in
   Collection documents SHOULD contain one "app:edited" element, and
   MUST NOT contain more than one.

   appEdited = element app:edited ( atomDateConstruct )

   The server SHOULD change the value of this element every time a
   Collection Member Resource or an associated Media Resource has been
   edited by any means.












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11.  Atom Format Link Relation Extensions

11.1  The "edit" Link Relation

   This specification adds the value "edit" to the Atom Registry of Link
   Relations (see section 7.1 of [RFC4287]).  The value of "edit"
   specifies that the value of the href attribute is the IRI of an
   editable Member Entry.  When appearing within an atom:entry, the href
   IRI can be used to retrieve, update and delete the resource
   represented by that entry.  An atom:entry MUST contain no more than
   one "edit" link relation.

11.2  The "edit-media" Link Relation

   This specification adds the value "edit-media" to the Atom Registry
   of Link Relations (see section 7.1 of [RFC4287]).  When appearing
   within an atom:entry, the value of the href attribute is an IRI that
   can be used to modify a Media Resource associated with that entry.

   An atom:entry element MAY contain zero or more "edit-media" link
   relations.  An atom:entry MUST NOT contain more than one atom:link
   element with a rel attribute value of "edit-media" that has the same
   type and hreflang attribute values.  All "edit-media" link relations
   in the same entry reference the same resource.  If a client
   encounters multiple "edit-media" link relations in an entry then it
   SHOULD choose a link based on the client preferences for type and
   hreflang.  If a client encounters multiple "edit-media" link
   relations in an entry and has no preference based on the type and
   hreflang attributes then the client SHOULD pick the first "edit-
   media" link relation in document order.





















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12.  Atom Publishing Controls

   This specification defines an Atom Format Structured Extension, as
   defined in Section 6 of [RFC4287], for publishing control within the
   http://purl.org/atom/app# namespace.

12.1  The "app:control" Element

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

    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 MUST appear only once in an Entry.  The app:
   control element is considered foreign markup as defined in Section 6
   of [RFC4287].

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

   The app:control element can contain an optional "app:draft" element
   as defined below, and can contain extension elements as defined in
   Section 6 of [RFC4287].

12.1.1  The "app:draft" Element

   The number of app:draft elements in app:control MUST be zero or one.
   Its value MUST be one of "yes" or "no".  A value of "no" indicates a
   client request that the Member Resource be made publicly visible.  If
   the app:draft element is missing then the value MUST be understood to
   be "no".  The inclusion of the app:draft element represents a request
   by the client to control the visibility of a Member Resource and the
   app:draft element MAY be ignored by the server.









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13.  Securing the Atom Publishing Protocol

   The Atom Publishing Protocol is based on HTTP.  Authentication
   requirements for HTTP are covered in Section 11 of [RFC2616].

   The use of authentication mechanisms to prevent posting or editing by
   unknown or unauthorized clients is RECOMMENDED but not required.
   When authentication is not used, clients and servers are vulnerable
   to trivial spoofing, denial of service and defacement attacks,
   however, in some contexts, this is an acceptable risk.

   The type of authentication deployed is a local decision made by the
   server operator.  Clients are likely to face authentication schemes
   that vary across server deployments.  At a minimum, client and server
   implementations MUST be capable of being configured to use HTTP Basic
   Authentication [RFC2617] in conjunction with a TLS connection
   [RFC4346] as specified by [RFC2818].

   The choice of authentication mechanism will impact interoperability.
   The minimum level of security referenced above (Basic Auth with TLS)
   is considered good practice for Internet applications at the time of
   publication of this specification and sufficient for establishing a
   baseline for interoperability.  Implementers should, in general,
   investigate and use alternative mechanisms regarded as equivalently
   good or better at the time of deployment.  It is RECOMMENDED that
   clients be implemented in such a way that allows new authentication
   schemes to be deployed.

   Because this protocol uses HTTP response status codes as the primary
   means of reporting the result of a request, servers are advised to
   respond to unauthorized or unauthenticated requests using an
   appropriate 4xx HTTP response code (e.g. 401 "Unauthorized" or 403
   "Forbidden") in accordance with [RFC2617].


















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14.  Security Considerations

   As an HTTP-based protocol, APP is subject to the security
   considerations found in Section 15 of [RFC2616].

14.1  Denial of Service

   Atom Publishing server implementations need to take adequate
   precautions to ensure malicious clients cannot consume excessive
   server resources (CPU, memory, disk, etc).

14.2  Replay Attacks

   Atom Publishing server implementations are susceptible to replay
   attacks.  Specifically, this specification does not define a means of
   detecting duplicate requests.  Accidentally sent duplicate requests
   are indistinguishable from intentional and malicious replay attacks.

14.3  Spoofing Attacks

   Atom Publishing implementations are susceptible to a variety of
   spoofing attacks.  Malicious clients may send Atom entries containing
   inaccurate information anywhere in the document.

14.4  Linked Resources

   Atom Feed and Entry documents can contain XML External Entities as
   defined in Section 4.2.2 of [W3C.REC-xml-20060816].  Atom
   implementations are not required to load external entities.  External
   entities are subject to the same security concerns as any network
   operation and can alter the semantics of an Atom document.  The same
   issues exist for resources linked to by Atom elements such as atom:
   link and atom:content.

14.5  Digital Signatures and Encryption

   Atom Entry Documents sent to a server might contain XML Digital
   Signatures [W3C.REC-xmldsig-core-20020212] and might be encrypted
   using XML Encryption [W3C.REC-xmlenc-core-20021210] as specified in
   Section 5 of [RFC4287].

   Servers are allowed to modify received resource representations in
   ways that can invalidate signatures covering those representations.

14.6  URIs and IRIs

   Atom Publishing Protocol implementations handle URIs and IRIs.  See
   Section 7 of [RFC3986] and Section 8 of [RFC3987].



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15.  IANA Considerations

15.1  Content-type registration for 'application/atomserv+xml'

   An Atom Publishing Protocol Service 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.
      [[anchor31: 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. [[anchor32: 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







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

   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). [[anchor33:
      update upon publication]]


15.2  Content-type registration for 'application/atomcat+xml'

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

   MIME media type name: application

   MIME subtype name: atomcat+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.
      [[anchor34: 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.






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   Published specification: This specification. [[anchor35: 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: .atomcat

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

   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). [[anchor36:
      update upon publication]]


15.3  Header field registration for 'SLUG'

   [[anchor37: incomplete section --dehora]]

   Header field: SLUG

   Applicable protocol: http [RFC2616]

   Status: standard.

    Author/Change controller: IETF (iesg@ietf.org) Internet Engineering
      Task Force

   Specification document(s): draft-ietf-atompub-protocol-11.txt
      ([[anchor38: update on rfc number assignment --dehora]])







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   Related information:


















































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16.  References

16.1  Normative References

   [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.

   [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.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [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.

   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346, April 2006.

   [W3C.REC-xml-20060816]
              Bray, T., Paoli, J., Maler, E., Sperberg-McQueen, C., and
              F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth
              Edition)", World Wide Web Consortium Recommendation REC-
              xml-20060816, August 2006.

   [W3C.REC-xml-infoset-20040204]
              Cowan, J., Tobin, R., and A. Layman, "XML Information Set
              (Second Edition)", W3C REC W3C.REC-xml-infoset-20040204,
              February 2004.



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   [W3C.REC-xml-names-20060816]
              Hollander, D., Bray, T., and A. Layman, "Namespaces in
              XML", World Wide Web Consortium Recommendation REC-xml-
              names-20060816, August 2006.

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

   [W3C.REC-xmldsig-core-20020212]
              Solo, D., Reagle, J., and D. Eastlake, "XML-Signature
              Syntax and Processing", World Wide Web Consortium
              Recommendation REC-xmldsig-core-20020212, February 2002,
              <http://www.w3.org/TR/2002/REC-xmldsig-core-20020212>.

   [W3C.REC-xmlenc-core-20021210]
              Eastlake, D. and J. Reagle, "XML Encryption Syntax and
              Processing", World Wide Web Consortium Recommendation REC-
              xmlenc-core-20021210, December 2002,
              <http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.

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)
   IBM
   4205 South Miama Blvd.
   Research Triangle Park, NC  27709
   US

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

   [[anchor42: chairs to compile a contribution list for 1.0 --dehora]]













































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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].

   The Schema for Service Documents:

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

   namespace app = "http://purl.org/atom/app#"
   namespace atom = "http://www.w3.org/2005/Atom"
   namespace xsd = "http://www.w3.org/2001/XMLSchema"
   namespace xhtml = "http://www.w3.org/1999/xhtml"
   namespace local = ""

   start = appService

   # common:attrs

   atomURI = text

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


   atomCommonAttributes = appCommonAttributes

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



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

   atomDateConstruct =
       appCommonAttributes,
       xsd:dateTime




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   # app:service

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

   # app:workspace

   appWorkspace =
      element app:workspace {
         appCommonAttributes,
         ( atomTitle
           & appCollection*
           & extensionElement* )
      }

   atomTitle = element atom:title { atomTextConstruct }

   # app:collection

   appCollection =
      element app:collection {
         appCommonAttributes,
         attribute href { atomURI  },
         ( atomTitle
           & appAccept?
           & appCategories*
           & extensionElement* )
      }

   # app:categories

   atomCategory =
       element atom:category {
          atomCommonAttributes,
          attribute term { text },
          attribute scheme { atomURI }?,
          attribute label { text }?,
          undefinedContent
       }

   appInlineCategories =
       element app:categories {
           attribute fixed { "yes" | "no" }?,
           attribute scheme { atomURI }?,



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           (atomCategory*)
       }

   appOutOfLineCategories =
       element app:categories {
           attribute href { atomURI },
           undefinedContent
       }

   appCategories = appInlineCategories | appOutOfLineCategories


   # app:accept

   appAccept =
      element app:accept {
            appCommonAttributes,
            ( appTypeValue? )
      }


   appTypeValue = ( "entry" | media-type |entry-or-media-type  )
   media-type = xsd:string { pattern = "entry,(.+/.+,?)*" }
   entry-or-media-type = xsd:string { pattern = "(.+/.+,?)*" }
   # above is an approximation, rnc doesn't support interleaved text


   # Simple Extension

   simpleExtensionElement =
      element * - app:* {
         text
      }

   # Structured Extension

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

   # Other Extensibility

   extensionElement =
      simpleExtensionElement | structuredExtensionElement



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   undefinedContent = (text|anyForeignElement)*

   # Extensions

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

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

   atomPlainTextConstruct =
       atomCommonAttributes,
       attribute type { "text" | "html" }?,
       text

   atomXHTMLTextConstruct =
       atomCommonAttributes,
       attribute type { "xhtml" },
       xhtmlDiv

   atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct

   anyXHTML = element xhtml:* {
       (attribute * { text }
        | text
        | anyXHTML)*
   }

   xhtmlDiv = element xhtml:div {
     (attribute * { text }
      | text
      | anyXHTML)*
   }

   # EOF

   The Schema for Category Documents:

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



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   namespace app = "http://purl.org/atom/app#"
   namespace atom = "http://www.w3.org/2005/Atom"
   namespace xsd = "http://www.w3.org/2001/XMLSchema"
   namespace local = ""

   start = appCategories

   # common:attrs

   atomCommonAttributes =
      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})*"
   }


   atomCategory =
       element atom:category {
          atomCommonAttributes,
          attribute term { text },
          attribute scheme { atomUri }?,
          attribute label { text }?,
          undefinedContent
       }

   appInlineCategories =
       element app:categories {
           attribute fixed { "yes" | "no" }?,
           attribute scheme { atomUri }?,
           (atomCategory*)
       }

   appOutOfLineCategories =
       element app:categories {
           attribute href { atomURI },
           (empty)
       }

   appCategories = appInlineCategories | appOutOfLineCategories




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   # Extensibility

   undefinedContent = (text|anyForeignElement)*

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

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

   # EOF
































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Appendix C.  Revision History

   draft-ietf-atompub-protocol-11: Parts of PaceAppEdited.
   PaceSecurityConsiderationsRevised.

   draft-ietf-atompub-protocol-10: PaceRemoveTitleHeader2,
   PaceSlugHeader4, PaceOnlyMemberURI,PaceOneAppNamespaceOnly,
   PaceAppCategories, PaceExtendIntrospection,
   UseElementsForAppCollectionTitles3, renamed Introspection to Service,
   lots of good editorials suggestions, updated media example with slug,
   moved xml conventions to convention sections, renamed XMl related
   Conventions to Atom Publishing Protocol Documents, added auth header
   to examples, consolidated definition of all resource types into the
   model section, added IANA reg info for application/atomcat+xml.

   draft-ietf-atompub-protocol-09: PaceWorkspaceMayHaveCollections,
   PaceMediaEntries5,
   http://www.imc.org/atom-protocol/mail-archive/msg05322.html, and
   http://www.imc.org/atom-protocol/mail-archive/msg05272.html

   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.



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   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
   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



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   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
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   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
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   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
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.

   The IETF has been notified of intellectual property rights claimed in
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Disclaimer of Validity

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


Copyright Statement

   Copyright (C) The Internet Society (2006).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.





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Acknowledgment

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















































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