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Network Working Group                                   J. Gregorio, Ed.
Internet-Draft                                                       IBM
Intended status: Standards Track                         B. de hOra, Ed.
Expires: September 5, 2007                                 Propylon Ltd.
                                                           March 4, 2007


                      The Atom Publishing Protocol
                   draft-ietf-atompub-protocol-14.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 September 5, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).













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Abstract

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













































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Editorial Note

   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 . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Notational Conventions . . . . . . . . . . . . . . . . . . . .  6
     2.1.  XML-related Conventions  . . . . . . . . . . . . . . . . .  6
       2.1.1.  Referring to Information Items . . . . . . . . . . . .  6
       2.1.2.  RELAX NG Schema  . . . . . . . . . . . . . . . . . . .  6
       2.1.3.  Use of xml:base and xml:lang . . . . . . . . . . . . .  6
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  7
   4.  Protocol Model . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Client Implementation Considerations . . . . . . . . . . .  9
   5.  Protocol Operations  . . . . . . . . . . . . . . . . . . . . . 11
     5.1.  Retrieving a Service Document  . . . . . . . . . . . . . . 11
     5.2.  Listing Collection Members . . . . . . . . . . . . . . . . 11
     5.3.  Creating a Resource  . . . . . . . . . . . . . . . . . . . 12
     5.4.  Editing a Resource . . . . . . . . . . . . . . . . . . . . 12
       5.4.1.  Retrieving a Resource  . . . . . . . . . . . . . . . . 12
       5.4.2.  Updating a Resource  . . . . . . . . . . . . . . . . . 13
       5.4.3.  Deleting a Resource  . . . . . . . . . . . . . . . . . 13
     5.5.  Use of HTTP Response codes . . . . . . . . . . . . . . . . 13
   6.  Atom Publishing Protocol Documents . . . . . . . . . . . . . . 14
     6.1.  Document Types . . . . . . . . . . . . . . . . . . . . . . 14
     6.2.  Document Extensibility . . . . . . . . . . . . . . . . . . 14
   7.  Category Documents . . . . . . . . . . . . . . . . . . . . . . 16
     7.1.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . 16
     7.2.  Element Definitions  . . . . . . . . . . . . . . . . . . . 16
       7.2.1.  The "app:categories" element . . . . . . . . . . . . . 16
   8.  Service Documents  . . . . . . . . . . . . . . . . . . . . . . 18
     8.1.  Workspaces . . . . . . . . . . . . . . . . . . . . . . . . 18
     8.2.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . 19
     8.3.  Element Definitions  . . . . . . . . . . . . . . . . . . . 20
       8.3.1.  The "app:service" Element  . . . . . . . . . . . . . . 20
       8.3.2.  The "app:workspace" Element  . . . . . . . . . . . . . 20
       8.3.3.  The "app:collection" Element . . . . . . . . . . . . . 21
       8.3.4.  The "app:accept" Element . . . . . . . . . . . . . . . 21
       8.3.5.  The "app:categories" Element . . . . . . . . . . . . . 22
   9.  Creating and Editing Resources . . . . . . . . . . . . . . . . 24
     9.1.  Member URIs  . . . . . . . . . . . . . . . . . . . . . . . 24
     9.2.  Creating resources with POST . . . . . . . . . . . . . . . 24
       9.2.1.  Example  . . . . . . . . . . . . . . . . . . . . . . . 25
     9.3.  Updating Resources with PUT  . . . . . . . . . . . . . . . 26
     9.4.  Deleting Resources with DELETE . . . . . . . . . . . . . . 26



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     9.5.  Caching and entity tags  . . . . . . . . . . . . . . . . . 26
       9.5.1.  Example  . . . . . . . . . . . . . . . . . . . . . . . 26
     9.6.  Media Resources and Media Link Entries . . . . . . . . . . 28
       9.6.1.  Examples . . . . . . . . . . . . . . . . . . . . . . . 29
     9.7.  The Slug: Header . . . . . . . . . . . . . . . . . . . . . 35
       9.7.1.  Slug: Header syntax  . . . . . . . . . . . . . . . . . 36
       9.7.2.  Example  . . . . . . . . . . . . . . . . . . . . . . . 36
   10. Listing Collections  . . . . . . . . . . . . . . . . . . . . . 37
     10.1. Collection partial lists . . . . . . . . . . . . . . . . . 37
     10.2. The "app:edited" Element . . . . . . . . . . . . . . . . . 38
   11. Atom Format Link Relation Extensions . . . . . . . . . . . . . 40
     11.1. The "edit" Link Relation . . . . . . . . . . . . . . . . . 40
     11.2. The "edit-media" Link Relation . . . . . . . . . . . . . . 40
   12. The Atom Format Type Parameter . . . . . . . . . . . . . . . . 41
     12.1. The 'type' parameter . . . . . . . . . . . . . . . . . . . 41
       12.1.1. Conformance  . . . . . . . . . . . . . . . . . . . . . 41
   13. Atom Publishing Controls . . . . . . . . . . . . . . . . . . . 42
     13.1. The "app:control" Element  . . . . . . . . . . . . . . . . 42
       13.1.1. The "app:draft" Element  . . . . . . . . . . . . . . . 42
   14. Securing the Atom Publishing Protocol  . . . . . . . . . . . . 43
   15. Security Considerations  . . . . . . . . . . . . . . . . . . . 44
     15.1. Denial of Service  . . . . . . . . . . . . . . . . . . . . 44
     15.2. Replay Attacks . . . . . . . . . . . . . . . . . . . . . . 44
     15.3. Spoofing Attacks . . . . . . . . . . . . . . . . . . . . . 44
     15.4. Linked Resources . . . . . . . . . . . . . . . . . . . . . 44
     15.5. Digital Signatures and Encryption  . . . . . . . . . . . . 44
     15.6. URIs and IRIs  . . . . . . . . . . . . . . . . . . . . . . 44
   16. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 45
     16.1. Content-type registration for
           'application/atomserv+xml' . . . . . . . . . . . . . . . . 45
     16.2. Content-type registration for 'application/atomcat+xml'  . 46
     16.3. Header field registration for 'SLUG' . . . . . . . . . . . 47
     16.4. The Link Relation registration "edit"  . . . . . . . . . . 48
     16.5. The Link Relation registration "edit-media"  . . . . . . . 48
     16.6. The Atom Format Media Type Parameter . . . . . . . . . . . 48
   17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 49
     17.1. Normative References . . . . . . . . . . . . . . . . . . . 49
     17.2. Informative References . . . . . . . . . . . . . . . . . . 50
   Appendix A.  Contributors  . . . . . . . . . . . . . . . . . . . . 52
   Appendix B.  RELAX NG Compact Schema . . . . . . . . . . . . . . . 53
   Appendix C.  Revision History  . . . . . . . . . . . . . . . . . . 59
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 63
   Intellectual Property and Copyright Statements . . . . . . . . . . 64








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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].  The protocol supports the creation of Web resources
   and provides facilities for:

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

   o  Services: Discovery and description of Collections.

   o  Editing: Creating, updating and deleting resources.

   The Atom Publishing Protocol is different from many contemporary
   protocols in that the server is given wide latitude in processing
   requests from clients.  See Section 4 for more details.


































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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], serialized as XML 1.0
   [W3C.REC-xml].

   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.  Requirements regarding the content and
   interpretation of xml:lang are specified in Section 2.12 of XML 1.0
   [W3C.REC-xml].










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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).

   In this specification the phrase "the URI of a document" 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.
   The protocol defines two kinds of Members - Entry and Media
   resources.

   Entry Resource - Member Resources of a Collection that are
   represented using the "application/atom+xml" media type.

   Media Resource -Member Resources of a Collection that are represented
   with a media type other than "application/atom+xml".

   Media Link Entry - an Entry Resource that contains metadata about a
   Media Resource.

   Workspace - A named group of Collections.  See Section 8.1.

   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.  When
      the client submits non-Atom-Entry representations to a Collection
      for creation, two resources are always created - a Media Entry for
      the requested resource, and a Media Link Entry for metadata (in
      Atom Entry format) about the resource.

   o  PUT is used to update a known resource.

   o  DELETE is used to remove a known resource.

   The Atom Protocol does not specify the form of the URIs that are
   used.  HTTP ([RFC2616]) specifies that the URI space of each server
   is controlled by that server, and this protocol imposes no further
   constraints on that control.  What is specified here are the formats
   of the representations that are exchanged and the actions that can be
   performed on the IRIs embedded in those representations.

   The Atom Protocol only covers the creation, update and deletion of
   Entry and Media resources.  Other resources could be created,
   updated, and deleted as the result of manipulating a Collection, but
   the number of those resources, their media-types, and effects of Atom
   Protocol operations on them are outside the scope of this
   specification.

   Since all aspects of client-server interaction are defined in terms
   of HTTP, [RFC2616] should be consulted for any areas not covered in
   this specification.

   Along with operations on Member Resources, the Atom Protocol defines
   Collection Resources for managing and organizing Member Resources.
   The representation of Collections are Atom Feed documents, and
   contain the IRIs of, and metadata about the Collection's Member
   Resources.  The Atom Protocol does not make a structural distinction
   between Feeds used for Collections and other Atom Feeds.  The only
   mechanism that this specification supplies for indicating a
   Collection Feed is its appearance in a Service Document.

   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].  In accordance with that specification,



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   this conversion SHOULD be applied as late as possible.  Conversion
   does not imply resource creation - the IRI and the URI into which it
   is converted identify the same resource.

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

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

   A Collection Feed's Atom Entries contain the Entry and Media Resource
   IRIs of the Collection.  A Collection Feed can contain any number of
   Entries for either kind, or an ordered subset of the Entries (see
   Section 10.1).  In the diagram of a Collection below, there are two
   Entries.  The first contains the IRI of an 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:

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

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

4.1.  Client Implementation Considerations

   The Atom Protocol imposes few restrictions on the actions of servers.
   Unless a constraint is specified here, servers can be expected to
   vary in behavior, in particular around the manipulation of Atom
   Entries sent by clients.  For example, although this specification
   only defines the expected behavior of Collections with respect to GET
   and POST, this does not imply that PUT, DELETE, PROPPATCH and others
   are forbidden on Collection resources - only that this specification
   does not define what the server's response would be to those methods.
   Similarly while some HTTP status codes are mentioned explicitly,
   clients ought to be prepared to handle any status code from a server.
   Servers can choose to accept, reject, delay, moderate, censor,
   reformat, translate, relocate or recategorize the content submitted



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   to them.  Only some of these choices are immediately relayed back to
   the client in responses to client requests; other choices may only
   become apparent later, in the feed or published entries.  The same
   series of requests to two different publishing sites can result in a
   different series of HTTP responses, different resulting feeds or
   different entry contents.

   As a result, client software has to be written flexibly to accept
   what the server decides are the results of its submissions.  Any
   server response or server content modification not explicitly
   forbidden by this specification or HTTP ([RFC2616]) is therefore
   allowed.







































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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
       group 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 whose
   Entries contain the IRIs of Member Resources.  The returned Feed may
   describe all, or only a partial list of the Members in a Collection
   (see Section 10).

   Client                          Server
     |                                |
     |  1.) GET to Collection URI     |
     |------------------------------->|
     |                                |
     |  2.) 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 Entry Resource.  Media
       Resources could have also been created and their IRIs can be
       found through the Entry Resource.  See Section 9.6 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.
   Section 11 describes extensions to the Atom Syndication Format used
   in the Atom Protocol for editing purposes.

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.  If the update is successful 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.  If the deletion is successful the server responds with a status
       code of 200.

   A different approach is taken for deleting Media Resources; see
   Section 9.6 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 according to 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 defines two kinds of Documents - Category
   Documents and Service Documents.

   A Category Document (Section 7) contains lists of categories
   specified using the "atom:category" element from the Atom Syndication
   Format.

   A Service Document (Section 8) groups available Collections into
   Workspaces.

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

   [[anchor8: The namespace name 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].  These
   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 Section 6 of [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 and MUST NOT signal
   an error.  Clients 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 recognized by processors conformant to this
   specification.  Such unrecognized markup from the
   "http://purl.org/atom/app#" namespace MUST be treated as foreign
   markup.




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   [[anchor9: The namespace name needs to be updated with the final URI
   upon publication]]

















































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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, where they describe
   the categories allowed in a Collection (see Section 8.3.5).

   Category Documents are identified with the "application/atomcat+xml"
   media type (see Section 16).

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.








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   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

7.2.1.1.  Attributes of "app:categories"

   The app:categories element can contain a "fixed" attribute, with a
   value of either "yes" or "no", indicating whether the list of
   categories is a fixed or an open set.  The absence of the "fixed"
   attribute is equivalent to the presence of a "fixed" attribute with a
   value of "no".

   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.














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8.  Service Documents

   For authoring to commence, a client needs to discover the
   capabilities and locations of the available Collections.  Service
   Documents are designed to support this discovery process.

   How Service Documents are discovered is not defined in this
   specification.

   Service Documents are identified with the "application/atomserv+xml"
   media type (see Section 16).

8.1.  Workspaces

   A Service Document groups a server's Collections into Workspaces.
   Operations on Workspaces, such as creation or deletion, are not
   defined by this specification.  In general, this specification
   assigns no meaning to Workspaces; that is, a Workspace does not imply
   any specific processing assumptions.

   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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8.2.  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>

   The Service Document above describes two Workspaces.  The first
   Workspace is called "Main Site", and 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 Media Resources (entries with associated Media Resources
   are discussed in Section 9.6).

   The second Workspace is called "Side Bar Blog" and has a single
   Collection called "Remaindered Links" whose IRI is



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   "http://example.org/reilly/list".

   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
   available 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.

8.3.  Element Definitions

8.3.1.  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* )
      }

8.3.2.  The "app:workspace" Element

   Workspaces are server-defined groups of Collections.  The "app:
   workspace" element contains zero or more app:collection elements
   describing the Collections of resources available for editing.


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

   atomTitle = element atom:title { atomTextConstruct }



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8.3.2.1.  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.

8.3.3.  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*
           & extensionSansTitleElement* )
      }

8.3.3.1.  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 content identifies
   a Collection by which new Entries can be added to appear in the feed.
   The app:collection element is considered foreign markup as defined in
   Section 6 of [RFC4287].

8.3.3.2.  The "href" Attribute

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

8.3.3.3.  The "atom:title" Element

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

8.3.4.  The "app:accept" Element

   The "app:accept" element value specifies a comma-separated list of
   media-ranges (see [RFC2616]).  The list identifies the types of
   representations that can be POSTed to the URI of a Collection.



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   Whitespace around and between media-range values is 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.  For example, 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 and
   indicates that Atom Entry Documents can be POSTed to the Collection.
   The value is equivalent to the media type and format parameter
   "application/atom+xml;type=entry", as defined in Section 12.  If the
   accept element exists but is empty, clients SHOULD assume that the
   Collection does not support the creation of new Entries.  If the
   accept element is not present, clients SHOULD treat this as
   equivalent to <app:accept>entry</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 = "(.+/.+,?)*" }

8.3.5.  The "app:categories" Element

   The "app:categories" element provides a list of the categories that
   can be applied to the members of a Collection.  See Section 7.2.1 for
   the detailed definition of app:categories.

   The server MAY reject attempts to create or update members whose
   categories are not listed in the Collection Document.  Collections
   that indicate the category set is open SHOULD NOT reject otherwise
   acceptable members whose categories are not listed by the Collection.



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   The absence of an "app:categories" element means that the category
   handling of the Collection is unspecified.

















































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9.  Creating and Editing Resources

9.1.  Member URIs

   The Member URI allows clients to retrieve, update and delete a Member
   Resource using HTTP's GET, PUT and DELETE methods.  As their name
   indicates, Entry Resources have Atom Entry documents as
   representations.

   Member URIs appear in two places.  They are returned in a Location
   header after successful resource creation using POST, as described in
   Section 9.2 below.  They can also appear in a Collection feed's
   entries, as atom:link elements with a link relation of "edit".

   A Member Entry SHOULD contain such an atom:link element with a link
   relation of "edit", which indicates the Member URI.

9.2.  Creating resources with POST

   To add members to a Collection, clients send POST requests to the URI
   of the Collection.

   Successful member creation is indicated with a 201 ("Created")
   response code.  When the Collection responds with a status code of
   201 ("Created"), it SHOULD also return a response body, which 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 "atom:id" element, returning the Entry
   can be useful to the client, enabling it to correlate the client and
   server views of the new Entry.

   When a Member Resource is created, its Member Entry URI MUST be
   returned in a Location header in the Collections's response.

   If the creation request contained an Atom Entry Document, and the
   subsequent response from the server contains a Content-Location
   header that matches the Location header character-for-character, then
   the client is authorized to interpret the response entity as being
   the representation of the newly created Entry.  Without a matching
   Content-Location header the client MUST NOT assume the returned
   entity is a complete representation of the created resource.

   The request body sent with the POST need not be an Atom Entry.  For
   example, it might be a picture, or a movie.  Collections MAY return a
   response with a status code of 415 ("Unsupported Media Type") to
   indicate that the media-type of the POSTed entity is not allowed or
   supported by the Collection.  For a discussion of the issues in
   creating such content, see Section 9.6.



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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">
         <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"
       Location: http://example.org/edit/first-post.atom

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

   The Entry created and returned by the Collection 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



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   and attributes, or change element content and attribute values.

9.3.  Updating Resources with PUT

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

9.5.  Caching and entity tags

   Implementers are advised to pay attention to cache controls, and to
   make use of the mechanisms available in HTTP to make editing resource
   easier, in particular entity-tags as outlined in
   [W3C.NOTE-detect-lost-update-19990510].  Clients are not assured to
   receive the most recent representations of Collection Members using
   GET if the server is authorizing intermediaries to cache them.

9.5.1.  Example

   Below, the client creates a Member Entry using POST:

       POST /myblog/entries HTTP/1.1
       Host: example.org
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Type: application/atom+xml;type=entry
       Content-Length: nnn
       Slug: First Post

       <?xml version="1.0" ?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>Atom-Powered Robots Run Amok</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <updated>2007-02-123T17:09:02Z</updated>
         <author><name>Captain Lansing</name></author>
         <content>It's something moving... solid metal</content>
       </entry>




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   The server signals a successful creation with a status code of 201,
   and returns an ETag header in the response.  Because in this case the
   server returned a Content-Location and Location header with the same
   value, the returned Entry representation can be understood to be
   complete (see Section 9.2) and thus the ETag entity value can be also
   be used.

       HTTP/1.1 201 Created
       Date: Fri, 23 Feb 2007 21:17:11 GMT
       Content-Length: nnn
       Content-Type: application/atom+xml;type=entry
       Location: http://example.org/edit/first-post.atom
       Content-Location: http://example.org/edit/first-post.atom
       ETag: "e180ee84f0671b1"

       <?xml version="1.0" ?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>Atom-Powered Robots Run Amok</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <updated>2007-02-123T17:09:02Z</updated>
         <author><name>Captain Lansing</name></author>
         <content>It's something moving... solid metal</content>
       </entry>

   The client can if it wishes use the returned ETag value to later
   construct a "Conditional GET" as defined in [RFC2616].  In this case,
   prior to editing the client sends the ETag value for the Member using
   the If-None-Match: header.
       GET /edit/first-post.atom HTTP/1.1
       Host: example.org
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       If-None-Match: "e180ee84f0671b1"

   If the Entry has not been modified, the server (or an intermediary
   cache) can return a status code of 304 (Not Modified).  This allows
   the client to determine it still has the most recent representation
   of the Entry at the time of editing.

       HTTP/1.1 304 Not Modified
       Date: Sat, 24 Feb 2007 13:17:11 GMT
       ETag: "e180ee84f0671b1"

   After editing, the client can PUT the updated Entry and send the ETag
   entity value in an If-Match header, informing the server to accept
   the entry on the condition the entity value sent still matches the
   server's.





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       PUT /edit/first-post.atom HTTP/1.1
       Host: example.org
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Type: application/atom+xml;type=entry
       Content-Length: nnn
       If-Match: "e180ee84f0671b1"

       <?xml version="1.0" ?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>Atom-Powered Robots Run Amok</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <updated>2007-02-24T16:34:06Z</updated>
         <author><name>Captain Lansing</name></author>
         <content>Update: it's a hoax!</content>
       </entry>

   The server however has since received a more recent update than the
   client's, and responds with a status code of 412 (Precondition
   Failed).

       HTTP/1.1 412 Precondition Failed
       Date: Sat, 24 Feb 2007 16:34:11 GMT
       ETag: "r34rrt84f0671b22"

   This informs the client that the server has a more recent version of
   the Entry and will not allow the update.

9.6.  Media Resources and Media Link Entries

   A client can POST a media type other than application/atom+xml to a
   Collection.  Such a request always 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 and appear
   in the Collection.

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

   The server can signal the media types it will accept using the
   "accept" element in the Service Document as specified in
   Section 8.3.4.

   Successful responses to creation requests MUST include the URI of the
   Media Link Entry in the Location header.  The Media Link Entry SHOULD
   contain an atom:link element with a link relation of "edit-media"



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   that contains the Media Resource IRI.  The Media Link Entry MUST have
   an "atom:content" element with a "src" attribute.  The value of the
   "src" attribute is an IRI for 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.  For example, the
   "src" attribute value might instead be a link into a static cache or
   content distribution network and not 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 any 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.

   The Atom Protocol does not specify a means to create multiple
   representations of the same resource (for example a PNG and a JPG of
   the same image) on creation or update.

9.6.1.  Examples

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


       POST /media/ 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



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   of the response.  The Media Link Entry includes a content element
   with a src attribute.  It also contains a link with a link relation
   of "edit-media", specifying the IRI to be used for modifying the
   Media Resource.


       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"
       Location: http://example.org/media/edit/the_beach.atom

       <?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://media.example.org/the_beach.png"/>
         <link rel="edit-media"
            href="http://media.example.org/edit/the_beach.png" />
         <link rel="edit"
            href="http://example.org/media/edit/the_beach.atom" />
       </entry>

   Later, the client PUTS a new PNG to the URI indicated in the Media
   Link Entry's "edit-media" link:

       PUT /edit/the_beach.png HTTP/1.1
       Host: media.example.org
       Content-Type: image/png
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Length: nnn

       ...binary data...

   The server signals a successful update with a status code of 200.

       HTTP/1.1 200 Ok
       Date: Fri, 8 Oct 2006 17:17:11 GMT
       Content-Length: nnn

   The client can update the metadata for the picture.  First GET the
   Media Link Entry:





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       GET /media/edit/the_beach.atom HTTP/1.1
       Host: example.org
       Authorization: Basic ZGFmZnk6c2VjZXJldA==

   The Media Link Entry is returned.


       HTTP/1.1 200 Ok
       Date: Fri, 7 Oct 2005 17:18:11 GMT
       Content-Length: nnn
       Content-Type: application/atom+xml; charset="utf-8"

       <?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://media.example.org/the_beach.png"/>
         <link rel="edit-media"
            href="http://media.example.org/edit/the_beach.png" />
         <link rel="edit"
            href="http://example.org/media/edit/the_beach.atom" />
       </entry>

   The metadata can be updated, in this case to add a summary, and then
   PUT back to the server.






















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       PUT /media/edit/the_beach.atom HTTP/1.1
       Host: example.org
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Type: application/atom+xml
       Content-Length: nnn

       <?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">
             A nice sunset picture over the water.
         </summary>
         <content type="image/png"
            src="http://media.example.org/the_beach.png"/>
         <link rel="edit-media"
            href="http://media.example.org/edit/the_beach.png" />
         <link rel="edit"
            href="http://example.org/media/edit/the_beach.atom" />
       </entry>

   The update was successful.


       HTTP/1.1 200 Ok
       Date: Fri, 7 Oct 2005 17:19:11 GMT
       Content-Length: 0

   Multiple media resources can be added to the Collection.


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

       ...binary data...

   The resource is created successfully.








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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"
       Location: http://example.org/media/edit/the_pier.atom

       <?xml version="1.0"?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>The Pier</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efe6b</id>
         <updated>2005-10-07T17:26:43Z</updated>
         <author><name>Daffy</name></author>
         <summary type="text" />
         <content type="image/png"
            src="http://media.example.org/the_pier.png"/>
         <link rel="edit-media"
            href="http://media.example.org/edit/the_pier.png" />
         <link rel="edit"
            href="http://example.org/media/edit/the_pier.atom" />
       </entry>

   The client can now create a new Atom Entry in the blog Entry
   Collection that references the two newly created Media Resources.




























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       POST /blog/ HTTP/1.1
       Host: example.org
       Content-Type: application/atom+xml
       Slug: A day at the beach
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Length: nnn

       <?xml version="1.0"?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>A fun day at the beach</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6b</id>
         <updated>2005-10-07T17:40:02Z</updated>
         <author><name>Daffy</name></author>
         <content type="xhtml">
             <xhtml:div xmlns:xhtml="http://www.w3.org/1999/xhtml">
                 <xhtml:p>We had a good day at the beach.
                     <xhtml:img
                         src="http://media.example.org/the_beach.png"/>
                 </xhtml:p>
                 <xhtml:p>Later we walked down to the pier.
                     <xhtml:img
                         src="http://media.example.org/the_pier.png"/>
                 </xhtml:p>
             </xhtml:div>
         </content>
       </entry>

   The resource is created successfully.























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       HTTP/1.1 200 Ok
       Date: Fri, 7 Oct 2005 17:20:11 GMT
       Content-Length: nnn
       Content-Type: application/atom+xml; charset="utf-8"
       Location: http://example.org/blog/atom/a-day-at-the-beach.atom

       <?xml version="1.0"?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>A fun day at the beach</title>
         <id>http://example.org/blog/a-day-at-the-beach.xhtml</id>
         <updated>2005-10-07T17:43:07Z</updated>
         <author><name>Daffy</name></author>
         <content type="xhtml">
             <xhtml:div xmlns:xhtml="http://www.w3.org/1999/xhtml">
                 <xhtml:p>We had a good day at the beach.
                     <xhtml:img
                        src="http://media.example.org/the_beach.png"/>
                 </xhtml:p>
                 <xhtml:p>Later we walked down to the pier.
                     <xhtml:img
                        src="http://media.example.org/the_pier.png"/>
                 </xhtml:p>
             </xhtml:div>
         </content>
         <link rel="edit"
           href="http://example.org/blog/edit/a-day-at-the-beach.atom"/>
         <link rel="alternate" type="application/xhtml+xml"
           href="http://example.org/blog/a-day-at-the-beach.xhtml"/>
       </entry>

   Note that the returned Entry contains a link with a relation of
   "alternate" that points to the associated XHTML page that was
   created.  This is not required by this specification, but is included
   to show the kinds of changes a server may make to an Entry.

9.7.  The Slug: Header

   Slug is a HTTP entity-header that when accompanying a POST to a
   Collection, constitutes a request by the client that its value be
   used as part of the URI for the to-be-created Member Resource.

   Servers MAY use the value of the Slug header when creating the Member
   URI of the newly-created resource, for instance by using some or all
   of the words in the value for the last URI segment.  Servers MAY also
   use the value when creating the atom:id or as the title of a Media
   Link Entry (see Section 9.6.).

   Servers MAY choose to ignore the Slug entity-header and MAY alter the



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   value before using it.  For instance, a server might filter out some
   characters or replace accented letters with non-accented ones,
   replace spaces with underscores, change case, and so on.

9.7.1.  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.

       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.

9.7.2.  Example

   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 an Entry Resource.

















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10.  Listing Collections

   Collection Resources MUST provide representations in the form of Atom
   Feed documents whose Entries contain the IRIs of the Members in the
   Collection.  No structural distinction is made between Collection
   Feeds and other kinds of Feeds - a Feed might act both as a 'public'
   feed for subscription purposes and as a Collection Feed.

   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.  Since the Atom Syndication
   Format states that the value of atom:updated is altered when the
   changes to an Entry are something that "the publisher considers
   significant", clients SHOULD be constructed in consideration of the
   fact that changes which do not result in alterations to the atom:
   updated value of an Entry will not affect the position of the Entry
   in a Collection.  The atom:updated value is not equivalent to the
   HTTP Last-Modified: header and can not be used to determine the
   freshness of cached responses.

   Clients MUST NOT assume that an Atom Entry returned in the Feed is a
   full representation of an Entry Resource and SHOULD perform a GET on
   the URI of the Member Entry before editing it.  See Section 9.5 for a
   discussion on the implications of cache control directives when
   obtaining entries.

10.1.  Collection partial lists

   Collections can contain large numbers of resources.  A client such as
   a web spider or web browser might be overwhelmed if the response to a
   GET contained every Entry in a Collection - in turn the server might
   also waste bandwidth and processing time on generating a response
   that cannot be handled.  For this reason, servers MAY respond to
   Collection GET requests with a feed document containing a 'partial
   list' of the Collection's members, which also links to the next
   partial list feed if it exists.  The first such partial list returned
   MUST contain the most recently updated member resources and MUST have
   an atom:link with a "next" relation whose "href" value is the URI of
   the next partial list of the Collection.  This next partial list will
   contain the next most recently updated set of Member Resources (and
   an atom:link to the following partial list if it exists).

   In addition, partial list feeds 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 entries in the



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   Collection.

   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 partial list of 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.

     <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 partial list feed
   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 content indicates the last time an Entry was edited.  If the
   entry has not been edited yet, the content indicates the time it was
   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 )




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
















































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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.  The Atom Format Type Parameter

   The Atom Syndication Format (RFC 4287) defines the "application/
   atom+xml" media type to identify both Atom Feed and Atom Entry
   Documents.  Implementation experience has demonstrated that Atom Feed
   and Entry Documents can have different processing models and that
   there are situations where they need to be differentiated.  This
   document defines an optional "type" parameter used to differentiate
   the two types of Atom documents.

12.1.  The 'type' parameter

   This document defines a new "type" parameter for use with the
   "application/atom+xml" media type:

      type = "entry" / "feed"

   Neither the parameter name nor its value are case sensitive.

   The value "entry" indicates that the media type identifies an Atom
   Entry Document.  The root element of the document MUST be atom:entry.

   The value "feed" indicates that the media type identifies an Atom
   Feed Document.  The root element of the document MUST be atom:feed.

   If not specified, the type is assumed to be unspecified, requiring
   Atom processors to examine the root element to determine the type of
   Atom document.

12.1.1.  Conformance

   New specifications MAY require that the type parameter be used to
   identify the Atom Document type.  Producers of Atom Entry Documents
   SHOULD use the type parameter regardless of whether or not it is
   required.  Producers of Atom Feed Documents MAY use the parameter.

   Atom processors that do not recognize the "type" parameter MUST
   ignore its value and examine the root element to determine the
   document type.

   Atom processors that do recognize the "type" parameter SHOULD detect
   and report inconsistencies between the parameter's value and the
   actual type of the document's root element.








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13.  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.

13.1.  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].

13.1.1.  The "app:draft" Element

   The inclusion of the app:draft element represents a request by the
   client to control the visibility of a Member Resource.  Server
   support is optional and thus the app:draft element MAY be ignored by
   the server.

   The number of app:draft elements in app:control MUST be zero or one.
   The content of an app:draft element MUST be one of "yes" or "no".  If
   the element contains "no" this indicates a client request that the
   Member Resource be made publicly visible.  If the app:draft element
   is not present then servers that support the extension MUST behave as
   though an app:draft element containing "no" was sent.





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14.  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 as
   specified by [RFC2818].  See [RFC4346] for more information on TLS.

   The choice of authentication mechanism will impact interoperability.
   The minimum level of security referenced above (Basic Authentication
   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 are
   encouraged to 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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15.  Security Considerations

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

15.1.  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).

15.2.  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.

15.3.  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.

15.4.  Linked Resources

   Atom Feed and Entry documents can contain XML External Entities as
   defined in Section 4.2.2 of [W3C.REC-xml].  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.

15.5.  Digital Signatures and Encryption

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

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

15.6.  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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16.  IANA Considerations

16.1.  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:  atomsvc+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.
      [[anchor30: 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. [[anchor31: 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:  .atomsvc







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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).
      [[anchor32: update upon publication]]

16.2.  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.
      [[anchor33: update upon publication]]

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

   Interoperability considerations:  There are no known interoperability
      issues.







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

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

   Additional information:

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

   File extension:  .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).
      [[anchor35: update upon publication]]

16.3.  Header field registration for 'SLUG'

   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-13.txt
      ([[anchor36: update on rfc number assignment]])

   Related information:








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16.4.  The Link Relation registration "edit"

   Attribute Value:  edit

   Description:  An 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.

   Expected display characteristics:  Undefined; this relation can be
      used for background processing or to provide extended
      functionality without displaying its value.

   Security considerations:  Automated agents should take care when this
      relation crosses administrative domains (e.g., the URI has a
      different authority than the current document).

16.5.  The Link Relation registration "edit-media"

   Attribute Value:  edit-media

   Description:  An IRI of an editable Media Resource.  When appearing
      within an atom:entry, the href IRI can be used to retrieve, update
      and delete the Media Resource associated with that Entry.

   Expected display characteristics:  Undefined; this relation can be
      used for background processing or to provide extended
      functionality without displaying its value.

   Security considerations:  Automated agents should take care when this
      relation crosses administrative domains (e.g., the URI has a
      different authority than the current document).

16.6.  The Atom Format Media Type Parameter

   IANA is requested to add a reference to this specification in the
   'application/atom+xml' media type registration.















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17.  References

17.1.  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.

   [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]
              Yergeau, F., Paoli, J., Bray, T., Sperberg-McQueen, C.,
              and E. Maler, "Extensible Markup Language (XML) 1.0
              (Fourth Edition)", World Wide Web Consortium
              Recommendation REC-xml-20060816, August 2006,
              <http://www.w3.org/TR/2006/REC-xml-20060816>.

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



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   [W3C.REC-xml-names]
              Hollander, D., Bray, T., Tobin, R., and A. Layman,
              "Namespaces in XML 1.0 (Second Edition)", World Wide Web
              Consortium Recommendation REC-xml-names-20060816,
              August 2006,
              <http://www.w3.org/TR/2006/REC-xml-names-20060816>.

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

   [W3C.REC-xmldsig-core]
              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]
              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>.

17.2.  Informative References

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

   [RNC]      Clark, J., "RELAX NG Compact Syntax", December 2001, <http
              ://www.oasis-open.org/committees/relax-ng/
              compact-20021121.html>.

   [W3C.NOTE-detect-lost-update-19990510]
              Nielsen, H. and D. LaLiberte, "Editing the Web: Detecting
              the Lost Update Problem Using Unreserved Checkout", World
              Wide Web Consortium NOTE NOTE-detect-lost-update,
              May 1999, <http://www.w3.org/1999/04/Editing/>.

   [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>
















































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Appendix A.  Contributors

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

   [[anchor40: 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*
           & extensionSansTitleElement* )
      }

   atomTitle = element atom:title { atomTextConstruct }

   # app:collection

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

   # 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

   simpleSansTitleExtensionElement =
      element * - (app:*|atom:title) {
         text
      }

   simpleExtensionElement =
      element * - (app:*) {
         text
      }


   # Structured Extension

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



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      }

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

   # Other Extensibility

   extensionSansTitleElement =
    simpleSansTitleExtensionElement|structuredSansTitleExtensionElement


   extensionElement =
      simpleExtensionElement | structuredExtensionElement

   undefinedContent = (text|anyForeignElement)*

   # Extensions

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

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

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

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

   atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct



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   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

   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

   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



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       }

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

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

   appCategories = appInlineCategories | appOutOfLineCategories


   # 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

   [[anchor42: This section to be removed upon publication.]]

   draft-ietf-atompub-protocol-14: typos; removed "The language context
   is only significant for elements and attributes declared to be
   "Language-Sensitive" by this specification. "; "Successful member
   creation is normally indicated with a 201 ("Created") response code."
   removed "normally" from that sentence (9.2); Added "Media Link
   Entries are represented as Atom Entries and appear in the
   Collection." to 9.6; said that an app:accept value of "entry" is
   equivalent to "application/atom+xml;type=entry"; double-check spec
   terms; Member Entry Resource -> Entry Resource; Added MLE, Entry
   Resource and Media Resource terms defs; 6.1 para split; 10.1
   collection paging, rewrote for clarity; 13.1.1 app:edited rewrote for
   clarity/conflict; text for GETting entries and cache handling; 4:
   Typo: "And Media Resources IRIs", s/Resources/Resource/; consensus
   call: application/atomsvc+xml, extension is .atomsvc; DRY app:
   categories; make it clear the app:draft support is optional whether
   or not the value is sent; 9.2: put related ideas together into
   paragraphs.; 10: partial list editing; security: use elharos text;
   app:edited: tweak text suplied by ari; create a section for
   workspaces and move the descriptive text there; Moved rfc2818 to non-
   normative references.  Added the W3C note on lost updates as a
   reference.

   draft-ietf-atompub-protocol-13: Added Lisa's verbiage.  Folded in
   James' Atom Format media type 'type' parameter spec.  Updated
   document references to be more consistent, added URLs to some, and
   shortened up their anchors.  Debugged rnc.

   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



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

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

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

   draft-ietf-atompub-protocol-05 - Added: Contributors section.  Added:
   de hOra to editors.  Fixed: typos.  Added diagrams and description to
   model section.  Incorporates PaceAppDocuments, PaceAppDocuments2,
   PaceSimplifyCollections2 (large-sized chunks of it anyhow: the
   notions of Entry and Generic resources, the section 4 language on the
   Protocol Model, 4.1 through 4.5.2, the notion of a Collection
   document, as in Section 5 through 5.3, Section 7 "Collection
   resources", Selection resources (modified from pace which talked
   about search); results in major mods to Collection Documents, Section
   9.2 "Title: Header" and brokeout para to section 9.1 Editing Generic
   Resources).  Added XML namespace and language section.  Some cleanup
   of front matter.  Added Language Sensitivity to some attributes.
   Removed resource descriptions from terminology.  Some juggling of
   sections.  See:
   http://www.imc.org/atom-protocol/mail-archive/msg01812.html.




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

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

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

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

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

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

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

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

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

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

   Rev 04 - 15Jul2003 - Updated the RSD version used from 0.7 to 1.0.



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   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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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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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

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

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


Intellectual Property

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   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
   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.


Acknowledgment

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





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