Network Working Group                                   J. Gregorio, Ed.
Internet-Draft                                           BitWorking, Inc                                                       IBM
Expires: December 25, 2006 March 9, 2007                                   B. de hOra, Ed.
                                                           Propylon Ltd.
                                                           June 23,
                                                      September 05, 2006

                      The Atom Publishing Protocol
                   draft-ietf-atompub-protocol-09.txt
                   draft-ietf-atompub-protocol-10.txt

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

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

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

Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.   Notational Conventions . . . . . . . . . . . . . . . . . . .   5
   3.   Terminology
     2.1  XML-related Conventions  . . . . . . . . . . . . . . . . .   5
       2.1.1  Referring to Information Items . . . . . . .   6
   4.   Protocol Model . . . . .   5
       2.1.2  RELAX NG Schema  . . . . . . . . . . . . . . . . . .   7
   5.   Protocol Operations .   5
       2.1.3  Use of xml:base and xml:lang . . . . . . . . . . . . .   5
   3.   Terminology  . . . . . .   8
     5.1  Retrieving an Introspection Document . . . . . . . . . . .   8
     5.2  Creating a Resource . . . . . . .   7
   4.   Protocol Model . . . . . . . . . . . .   8
     5.3  Editing a Resource . . . . . . . . . . .   8
   5.   Protocol Operations  . . . . . . . . .   8
       5.3.1  Retrieving a Resource . . . . . . . . . . .  10
     5.1  Retrieving a Service Document  . . . . .   9
       5.3.2  Updating a Resource . . . . . . . . .  10
     5.2  Listing Collection Members . . . . . . . .   9
       5.3.3  Deleting a Resource . . . . . . . .  10
     5.3  Creating a Resource  . . . . . . . . .   9
     5.4  Listing Collection Members . . . . . . . . . .  11
     5.4  Editing a Resource . . . . . .  10
     5.5  Use of HTTP Response codes . . . . . . . . . . . . . .  11
       5.4.1  Retrieving a Resource  . .  10
   6.   XML-related Conventions . . . . . . . . . . . . . .  11
       5.4.2  Updating a Resource  . . . .  11
     6.1  Referring to Information Items . . . . . . . . . . . . .  12
       5.4.3  Deleting a Resource  .  11
     6.2  XML Namespace Usage . . . . . . . . . . . . . . . .  12
     5.5  Use of HTTP Response codes . . .  11
     6.3  Use of xml:base and xml:lang . . . . . . . . . . . . .  12
   6.   Atom Publishing Protocol Documents . .  11
     6.4  RELAX NG Schema . . . . . . . . . . .  13
     6.1  Document Types . . . . . . . . . .  12
   7.   Introspection Documents . . . . . . . . . . . .  13
     6.2  Document Extensibility . . . . . .  13
     7.1  Example . . . . . . . . . . . .  13
   7.   Category Documents . . . . . . . . . . . . .  13
     7.2  Element Definitions . . . . . . . .  14
     7.1  Example  . . . . . . . . . . .  14
       7.2.1  The "app:service" Element . . . . . . . . . . . . . .  14
       7.2.2  The "app:workspace"
     7.2  Element Definitions  . . . . . . . . . . . . .  14
       7.2.3  The "app:collection" Element . . . . . .  14
       7.2.1  The "app:categories" element . . . . . . .  15
       7.2.4  The "app:accept" Element . . . . . .  14
   8.   Service Documents  . . . . . . . . .  16
   8.   Collections . . . . . . . . . . . .  16
     8.1  Example  . . . . . . . . . . . .  17
     8.1  Creating resources with POST . . . . . . . . . . . . .  16
     8.2  Element Definitions  . .  17
     8.2  Example . . . . . . . . . . . . . . . . .  17
       8.2.1  The "app:service" Element  . . . . . . . .  17
     8.3  The 'edit' Link . . . . . .  17
       8.2.2  The "app:workspace" Element  . . . . . . . . . . . . .  17
       8.2.3  The "app:collection" Element . .  19
     8.4  Media Resources and Media Link Entries . . . . . . . . . .  19
       8.4.1  Title: Header .  18
       8.2.4  The "app:accept" Element . . . . . . . . . . . . . . .  19
       8.2.5  The "app:categories" Element . . . .  20
       8.4.2  Example . . . . . . . . .  20
   9.   Creating and Editing Resources . . . . . . . . . . . . . .  20
     8.5  Editing Entries with Foreign Markup .  22
     9.1  Member URIs  . . . . . . . . . . . . . .  21
   9.   Listing Collections . . . . . . . . .  22
     9.2  Creating resources with POST . . . . . . . . . . . . . . .  22
     9.1  Collection Paging
       9.2.1  Example  . . . . . . . . . . . . . . . . . . . . .  22
   10.  Atom Format Link Relation Extensions . .  23
     9.3  Updating Resources with PUT  . . . . . . . . . .  24
     10.1   The "edit" Link Relation . . . . .  24
     9.4  Deleting Resources with DELETE . . . . . . . . . . . . . .  24
     10.2   The "edit-media"
     9.5  Media Resources and Media Link Relation Entries . . . . . . . . . .  24
     9.6  The Slug: Header . . . . . . . .  24
   11.  Atom Publishing Control Extensions . . . . . . . . . . . . .  25
     11.1   The Atom Publishing Control Namespace
       9.6.1  Slug: Header syntax  . . . . . . . . .  25
     11.2   The "pub:control" Element . . . . . . . .  25
       9.6.2  Examples . . . . . . .  25
       11.2.1   The "pub:draft" Element . . . . . . . . . . . . . .  25
   12.  Securing the Atom Protocol . .  26
   10.  Listing Collections  . . . . . . . . . . . . . . .  26
   13.  Security Considerations . . . . .  28
     10.1   Collection Paging  . . . . . . . . . . . . .  27
   14.  IANA Considerations . . . . . .  28
   11.  Atom Format Link Relation Extensions . . . . . . . . . . . .  30
     11.1   The "edit" Link Relation . .  28
   15.  References . . . . . . . . . . . . . .  30
     11.2   The "edit-media" Link Relation . . . . . . . . . . .  30
     15.1   Normative References . .  30
   12.  Atom Publishing Controls . . . . . . . . . . . . . . . .  30
     15.2   Informative References . .  31
     12.1   The "app:control" Element  . . . . . . . . . . . . . . .  31
        Authors' Addresses
       12.1.1   The "app:draft" Element  . . . . . . . . . . . . . .  31
   13.  Securing the Atom Protocol . . . . . . . . .  32
   A.   Contributors . . . . . . . .  32
   14.  Security Considerations  . . . . . . . . . . . . . . . . . .  33
   B.   RELAX NG Compact Schema
   15.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  34
   C.   Revision History
     15.1   Content-type registration for
            'application/atomserv+xml' . . . . . . . . . . . . . . .  34
     15.2   Content-type registration for
            'application/atomcat+xml'  . . . . . . . . . . . . . . .  35
   16.  References . . . . . . . . . . . . . . . . . . . . . . . . .  37
        Intellectual Property and Copyright Statements
     16.1   Normative References . . . . . . .  40

1.  Introduction

   The Atom Publishing Protocol is an application-level protocol for
   publishing and editing Web resources using HTTP [RFC2616] and XML 1.0
   [W3C.REC-xml-20040204].  The protocol supports . . . . . . . . . . .  37
     16.2   Informative References . . . . . . . . . . . . . . . . .  38
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  39
   A.   Contributors . . . . . . . . . . . . . . . . . . . . . . . .  40
   B.   RELAX NG Compact Schema  . . . . . . . . . . . . . . . . . .  41
   C.   Revision History . . . . . . . . . . . . . . . . . . . . . .  47
        Intellectual Property and Copyright Statements . . . . . . .  50

1.  Introduction

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

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

   o  Introspection:  Service: Discovering and describing collections. Collections.

   o  Editing: Creating, updating and deleting resources.

2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   Note: The Introspection Document allows

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

2.1  XML-related Conventions

2.1.1  Referring to Information Items

   Atom Protocol Document formats are specified in
   Section 3.1 terms of Internationalized Resource Identifiers (IRIs)
   [RFC3987].

3.  Terminology

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

   URI/IRI - XML
   Information Set [W3C.REC-xml-infoset-20040204], serialized as XML 1.0
   [W3C.REC-xml-20040204].

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

2.1.2  RELAX NG Schema

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

2.1.3  Use of xml:base and xml:lang

   XML elements defined by this specification MAY have an xml:base
   attribute [W3C.REC-xmlbase-20010627].  When xml:base is used, it
   serves the function described in section 5.1.1 of URI Generic Syntax
   [RFC3986], by establishing the base URI (or IRI) for resolving
   relative references found within the scope of the xml:base attribute.

   Any element defined by this specification MAY have an xml:lang
   attribute, whose content indicates the natural language for the
   element and its descendents.  The language context is only
   significant for elements and attributes declared to be "Language-
   Sensitive" by this specification.  Requirements regarding the content
   and interpretation of xml:lang are specified in Section 2.12 of XML
   1.0 [W3C.REC-xml-20040204].

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].  Note that  IRIs are mapped to URIs
   before dereferencing takes place.

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

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

   Representation

   Resource - An entity included with a request A network-accessible data object or response 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 Member IRIs.  See
   Section 8. 9.

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

   Introspection Collection by a link
   element with a relation of "edit" or "edit-media".  See Section 9.1.

   Workspace - A group of collections.  See Section 8.

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

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

4.  Protocol Model

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

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

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

   o  PUT is used to update a known resource.

   o  DELETE is used to remove a known resource.

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

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

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

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

     Collection
        Entry
           Member Entry IRI    ->   Member Entry Resource

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

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

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

5.  Protocol Operations

5.1  Retrieving an Introspection a Service Document

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

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

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

5.2  Listing Collection Members

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

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

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

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

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.
       Collection.

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

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

5.4  Editing a Resource

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

5.3.1

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 Member's URI of a Member Resource to
       retrieve its representation.

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

5.3.2

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 Member's URI. URI of a Member
       Resource.

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

5.3.3

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 Member's URI. URI of a Member
       Resource.

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

5.4  Listing Collection Members

   To list the members of a Collection the client sends a GET request to
   the Collection's URI.  An Atom Feed Document

   A different approach is returned containing
   one Atom Entry taken for each member resource.  See Section 9 and deleting Media Resources, see
   Section 10 9.5 for a description details.

5.5  Use of the feed contents.

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

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

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

5.5  Use of HTTP Response codes

   The Atom Protocol uses HTTP Response codes

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

6.  XML-related Conventions

   The  Atom Publishing Protocol Introspection format is Documents

6.1  Document Types

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

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

   The namespace name [W3C.REC-xml-names-19990114] for either kind of
   document is:
       http://purl.org/atom/app#

   This specification uses the
   XML Information Set [W3C.REC-xml-infoset-20040204], serialised as XML
   1.0 [W3C.REC-xml-20040204]. prefix "app:" for the namespace name.
   The prefix "atom:" is used for "http://www.w3.org/2005/Atom", the
   namespace name of the Atom Syndication Format [RFC4287].  The
   namespace prefixes are not semantically significant.

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

6.1  Referring to Information Items

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

6.2  XML Namespace Usage  Document Extensibility

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

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

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

   The "app:" namespace "http://purl.org/atom/app#" is reserved for future
   forward-compatible revisions of the Atom Publishing Protocol. document types.  Future versions
   of this specification could add new elements and attributes to the markup
   vocabulary. attributes.
   Software written to conform to this version of the specification will
   not be able to process such markup correctly and, and in fact, fact will not be
   able to distinguish it from markup error.  For
   the purposes of this discussion, unrecognized

   Unrecognized markup from the in an Atom Publishing Protocol vocabulary will be document is
   considered "foreign markup".

   This specification also uses the prefix "atom:" for
   "http://www.w3.org/2005/Atom", the namespace name markup" as defined in [RFC4287].

   Markup from other vocabularies ("foreign markup") can be used
   anywhere within a Category or Service Document unless it is
   explicitly forbidden.  Processors that encounter foreign markup MUST
   NOT stop processing or signal an error, and SHOULD preserve foreign
   markup when transmitting such documents.

7.  Category Documents

   Category Documents contain lists of categories described using the
   "atom:category" element from the Atom Syndication Format [RFC4287].

6.3  Use of xml:base
   Categories can also appear in Service Documents 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 describe the function described
   categories allowed in section 5.1.1 of URI Generic Syntax
   [RFC3986], establishing a Collection (see Section 8.2.5).

   Category Documents are identified with the base URI (or IRI) for resolving any
   relative references found within "application/atomcat+xml"
   media type (see Section 15).

7.1  Example

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

   This Category Document contains three categories with the effective scope terms
   "animal", "vegetable", and "mineral".  None of the xml:base
   attribute.

   Any element categories has a
   label attribute (as defined by this specification MAY have an xml:lang
   attribute, whose content indicates in [RFC4287]).  They all inherit the natural language for
   "http://example.com/cats/big3" category 'scheme' (in the [RFC4287]
   sense) 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 and its descendents.

   The language context root of a Category Document is only
   significant for the "app:categories" element.  An
   app:categories element MAY contain one or more "atom:category"
   elements and attributes declared to be "Language-
   Sensitive" by this specification.  Requirements regarding from the content
   and interpretation of xml:lang are specified in Section 2.12 of XML
   1.0 [W3C.REC-xml-20040204].
   appCommonAttributes = Atom namespace ("http://www.w3.org/2005/Atom").

   If an app:category child element has no "scheme" attribute xml:base { atomUri }?, it
   inherits the attribute xml:lang { atomLanguageTag }?,
      undefinedAttribute*

6.4  RELAX NG Schema

   Some sections from its app:categories parent.  An app:
   category child element with an existing "scheme" attribute does not
   inherit the "scheme" value of this specification are illustrated its "app:categories" parent element.

7.2.1.1  Attributes of "app:categories"

   The app:categories element MAY contain a "fixed" attribute, with fragments a
   value of either "yes" or "no", indicating if the list of categories
   is a non-normative RELAX NG Compact schema [RNC].  A complete schema
   appears fixed or an open set.  Collections that indicate the set is
   fixed MAY reject members whose categories are not listed in Appendix B.  However, the text of this specification
   provides
   Collection Document.  Collections that indicate the definition of conformance.

7.  Introspection set is open
   SHOULD NOT reject otherwise acceptable members whose categories are
   not listed in the Collection.

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

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

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

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

   appCategories = appInlineCategories | appOutOfLineCategories

8.  Service Documents

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

   A Service Document describes workspaces, which are server-defined
   groupings of collections.

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

   While an introspection document allows multiple workspaces, there 15).

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

7.1 Workspace.

8.1  Example

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

   This Introspection Service Document describes two workspaces.  The first, first Workspace
   is called "Main Site", has two collections called "My Blog Entries"
   and "Pictures" whose IRIs are "http://example.org/reilly/main" and
   "http://example.org/reilly/pic" respectively.  The "Pictures"
   Workspace includes an accept "accept" element indicating that a client can
   post image files to the collection Collection to create new entries.  Entries
   with associated media resources are discussed in section 8.3. Section 9.5.

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

7.2  Element Definitions

7.2.1  The "app:service" Element

   The root

   Within each of an introspection document is the "app:service" element.

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

8.2  Element Definitions

8.2.1  The "app:service" Element

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

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

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

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

7.2.2

8.2.2  The "app:workspace" Element

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

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

   atomTitle = element atom:title { atomTextConstruct }

   In an app:workspace element, the first app:collection element MUST
   refer to the preferred or primary collection. Collection.  In the following
   example, the "Entries" collection would be considered the preferred
   collection:
   Collection:

       <service xmlns="http://purl.org/atom/app#">
         <workspace title="My Blog"> xmlns="http://purl.org/atom/app#"
        xmlns:atom="http://www.w3.org/2005/Atom">
         <workspace>
           <atom:title>My Blog</atom:title>
           <collection title="Entries"
                href="http://example.org/myblog/entries" /> >
             <atom:title>Entries</atom:title>
          </collection>
           <collection title="Photos"
                href="http://example.org/myblog/fotes">
              <atom:title>Photos</atom:title>
              <accept>image/*</accept>
           </collection>
         </workspace>
       </service>

7.2.2.1

8.2.2.1  The "title" Attribute "atom:title" Element

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

7.2.3

8.2.3  The "app:collection" Element

   The "app:collection" element describes an 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 that one app:accept element.

   appCollection =
      element app:collection {
         appCommonAttributes,
         attribute href { atomURI  },
         ( appAccept?

           & appCategories*
           & extensionElement* )
      }

8.2.3.1  Usage in Atom Protocol collection.  One Feed Documents

   The app:collection element MAY appear as a child of an atom:feed or
   atom:source element is defined here in an Atom Feed Document.  Its value identifies a
   Collection by which new entries can be added to appear in the feed.

8.2.3.2  The "href" Attribute

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

8.2.3.3  The "atom:title" Element

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

   appCollection the Workspace.

8.2.4  The "app:accept" Element

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

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

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

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

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

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

8.2.5  The "app:categories" Element

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

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

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

   appOutOfLineCategories =
       element app:categories { text },
           attribute href { atomUri atomURI },
         ( appAccept?
           & extensionElement* )
           (empty)
       }

   In an Atom feed, the app:collection

   appCategories = appInlineCategories | appOutOfLineCategories
   The app:categories element MAY appear as contain a child "fixed" attribute, with a
   value of
   an atom:feed either "yes" or atom:source element to identify "no", indicating whether or not the collection listing
   of categories is considered to
   which new entries can be added a fixed, or closed set.  The
   absence of the "fixed" attribute is equivalent to the feed.

7.2.3.1  The "title" Attribute

   The app:collection element MUST contain presence of a
   "fixed" attribute with a "title" attribute, whose value gives of "no".  Collections that indicate a human-readable name for
   fixed set MAY reject members that include categories not specified in
   the collection.  This attribute
   is Language-Sensitive.

7.2.3.2  The "href" Attribute provided listing.  Collections that indicate an open set SHOULD
   NOT reject otherwise acceptable members whose categories are not
   present in the provided list.

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

7.2.4  The "app:accept" Element

   The app:collection element MAY contain one "app:accept" element.  The
   app:accept element value specifies a comma-separated list of media-
   ranges [RFC2616] reference identifying a Category Document.  If
   the types of representations that can be
   POSTed to "href" attribute is provided, the Collection's URI.  Whitespace separating app:categories element MUST be
   empty and the media-
   range values is considered insignificant "fixed" and "scheme" attributes MUST NOT be ignored. present.

9.  Creating and Editing Resources

9.1  Member URIs

   The app:accept element is similar to the HTTP Accept request-header
   [RFC2616] with the exception that app:accept has no notion of
   preference.  Accordingly, Member URI supports retrieving, updating and deleting the value syntax of app:accept does not use
   accept-params or "q" parameters as specified in [RFC2616], section
   14.1.  The order of media-ranges is not significant.  The following
   lists are all equivalent:

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

   A value
   resource using HTTP GET, PUT and DELETE as described in this section.
   Retrieval and updating of "entry" indicates that Member Entry Resources are done via Atom
   Entry Documents can be posted
   to the Collection.  If representations.

   Member Entry URIs appear in two places.  First, they are returned in
   a Location header after successful resource creation using POST, as
   described below.  Second, in the accept entries of a Collection document, by
   an atom:link element is omitted, or empty,
   clients SHOULD assume that only Atom with a link relation of "edit".

   Each Member Entry documents will be accepted
   by the collection.

   appAccept = SHOULD contain such an atom:link 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.  Collections

8.1 providing
   its Member Entry URI.

9.2  Creating resources with POST

   To add members to a collection, Collection, clients send POST requests to the
   collection's URI. URI
   of a Collection.  Collections MAY impose constraints on the media-
   types of request entities POSTed to the collection Collection and MAY generate a
   response with a status code of 415 ("Unsupported Media Type").

   If an entry a Member Resource was created in the collection Collection which received the
   POST, its Member Entry URI MUST be returned in an HTTP Location
   header.

   When the server generates a response with a status code of 201
   ("Created"), it SHOULD also return a response body, which, which if
   provided, MUST be an Atom Entry Document representing the newly-
   created resource.  Clients MUST NOT assume that an Atom resource, and SHOULD include its Member Entry
   returned is URI in an atom:
   link element that has a full representation relation of the member resource. "edit".

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

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

   Clients MUST NOT assume that the URI provided by the Location header
   can be used to edit the created entry.

   The request body of sent with the POST need not be an Atom entry. Entry.  For
   example, it might be a picture, or a movie.  For a discussion of the
   issues in posting such content, see Section 8.4.

8.2 9.5.

9.2.1  Example

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

       POST /myblog/entries HTTP/1.1
       Host: example.org
       User- Agent:
       User-Agent: Thingio/1.0
       Content- Type:
       Authorization: Basic ZGFmZnk6c2VjZXJldA==
       Content-Type: application/atom+xml
       Content- Length:
       Content-Length: nnn
       Slug: First Post

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

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

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

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

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

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

8.3  The 'edit' Link

   Each member Entry within a collection SHOULD contain an atom:link
   element with a link relation name of "edit" that contains the IRI author, presumably via the authentication
   protocol used to
   retrieve, update or delete establish the member Entry.

8.4  Media right to post.

9.3  Updating Resources and with PUT

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

   To avoid unintentional loss of data when editing Member Entries or
   Media Link Entries

   As discussed above, if the body of a client's POST is an Entries, Atom Entry
   document, this constitutes a request Protocol clients SHOULD preserve all
   metadata that the server create a new
   entry has not been intentionally modified, including unknown
   foreign markup as defined in the collection Section 6 of [RFC4287].

9.4  Deleting Resources with DELETE

   To delete a resource, clients send DELETE requests to which the POST is addressed and return its
   URI.

   If Member URI,
   as specified in [RFC2616].  For Media Resources, deletion of a Media
   Link Entry SHOULD result in the body deletion of the client's associated Media
   Resource.

9.5  Media Resources and Media Link Entries

   A client can POST is of a media type other than
   application/atom+xml, this constitutes application/atom+xml to a request that the server
   create
   Collection.  Such a request creates two new resource as represented by resources - one that
   corresponds to the body of entity sent in the post, request, called
   a "media resource", the Media
   Resource, and also an entry in the collection to which the
   POST was addressed, associated Member Entry, called a "media link entry", and return both
   URIs.  If the Media Link
   Entry.  The server successfully creates a media resource and can signal the media
   link entry pair, types it will accept via the Location header included
   "accept" element in the response MUST be
   that of the media link entry. Service Document (Section 8.2.4).

   The media link entry MUST have a
   "content" element with a "src" attribute which links to Media Link Entry contains the media
   resource. IRI of the Media Resource and makes
   metadata about it separately available for retrieval and update.  The intent
   Media Link Entry is that the media link entry be used to store metadata about the (perhaps non-textual) media resource, so that non-
   textual) Media Resource.

   Successful responses to creation requests MUST include the media and URI of the metadata can be retrieved and updated separately.

   A media link entry
   Media Link Entry in the Location header.  The Media Link Entry SHOULD
   contain an atom:link element with a link relation of "edit-media"
   that contains the Media Resource IRI.  The Media Link Entry MUST have
   an "atom:content" element with a non-empty "src" attribute.  The
   value of the "src" attribute is an IRI used to modify of the
   media resource.  Deletion newly created Media
   Resource.  It is OPTIONAL that the IRI of the "src" attribute on the
   atom:content element be the same as the Media Resource IRI.  That is,
   the "src" attribute value might instead be a media link entry SHOULD result in the
   deletion of into a static cache
   or content distribution network and not be the linked media resource.

   Implementors will Media Resource IRI.

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

   Note that

   For resource creation this specification covers the only defines cases when where the
   POST body is has an Atom Entry, and when it is of 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 POST POSTed media-type is application/atom+xml "application/
   atom+xml" but the body is something other than an Atom Entry.

8.4.1  Title: Header

   A POST whose body is not of the  In
   particular, what happens on POSTing an Atom Feed Document to a
   Collection using the "application/atom+xml" media type and which thus
   requests the creation of is undefined.

9.6  The Slug: Header

   Slug is a media resource SHOULD contain HTTP entity-header whose value is a Title:
   header indicating the client's suggested title "slug", i.e. a short
   name that can be used as part of URI for the resource.  For
   example:

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

       ...binary data...

   The a Member Resource.

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

   Servers MAY ignore the resource, which
   would presumably appear in Slug entity-header and MAY alter its value
   before using it.  For example, the media link entry.

       Title = "Title" ":" [TEXT] server MAY filter out some
   characters or replace accented letters with non-accented ones, spaces
   with underscores, etc.

9.6.1  Slug: Header syntax

   The syntax of this header MUST conform to the augmented BNF grammar
   in section 2.1 of the HTTP/1.1 specification [RFC2616].  The [TEXT] TEXT
   rule is described in section 2.2 of the same document.  Words of

       Slug = "Slug" ":" *TEXT

   Clients MAY contain send non-ASCII characters from character sets other than
   [ISO88591] only when encoded according to in the rules of Slug entity-header,
   which they MUST encode using "encoded-words", as defined in
   [RFC2047].

8.4.2  Example  Servers SHOULD treat the slug as [RFC2047] encoded if it
   matches the "encoded-words" production.

9.6.2  Examples

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

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

       ...binary data...

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

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

       <?xml version="1.0"?>
       <entry xmlns="http://www.w3.org/2005/Atom">
         <title>A picture of the beach</title>
         <title>The Beach</title>
         <id>urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a</id>
         <updated>2003-12-13T18:30:02Z</updated>
         <author><name>John Doe</name></author>
         <updated>2005-10-07T17:17:08Z</updated>
         <author><name>Daffy</name></author>
         <summary type="text" />
         <content type="image/png"
           src="http://example.org/media/img123.png"/>
            src="http://example.org/media/the_beach.png"/>
         <link rel="edit"
           href="http://example.org/edit/first-post.atom" rel="edit-media"
            href="http://example.org/media/edit/the_beach.png" />
         <link rel="edit-media"
           href="http://example.org/edit/img123.png" rel="edit"
            href="http://example.org/myblog/edit/the_beach />
       </entry>

8.5  Editing Entries with Foreign Markup

   To avoid unintentional loss
   Here is an example of data when editing entries or media
   link entries, Atom Protocol clients SHOULD preserve all metadata,
   including unknown foreign markup as defined in 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 6 9.2.1 for an example of
   [RFC4287], which has not been intentionally modified.

9. the Slug: header applied to the
   creation of a Member Entry Resource.

10.  Listing Collections

   Collection resources MUST provide representations in the form of Atom
   Feed documents whose entries represent the collection's members. Members in the Collection.
   Each entry in the Feed Document SHOULD have an atom:link element with
   a relation of "edit" (See Section 10.1). 11.1).

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

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

10.1  Collection Paging

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

9.1  Collection Paging

   The returned Atom feed Feed MAY NOT contain entries for all the
   collection's members. Members in
   a Collection.  Instead, the Atom feed Feed document MAY contain link
   elements with "rel" attribute values of "next", "previous", "first"
   and "last" that can be used to navigate through the complete set of
   matching entries.

   For instance, suppose a client is supplied the URI
   "http://example.org/entries/go" of a collection Collection of member Member entries,
   where the server as a matter of policy avoids generating feed
   documents containing more than 10 entries.  The Atom feed Feed document
   for the collection Collection will then represent the first 'page' in a set of
   10 linked feed documents.  The "first" relation will reference the
   initial feed document in the set and the "last" relation references
   the final feed document 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 feed 'page' located
   at "http://example.org/entries/2" would look like this:

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

10.

11.  Atom Format Link Relation Extensions

10.1

11.1  The "edit" Link Relation

   The Atom Protocol

   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 Atom Entry Document. Member Entry.  When appearing within an atom:entry, the href
   IRI MAY 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.

10.2

11.2  The "edit-media" Link Relation

   The Atom Protocol

   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
   MAY be used to modify a media resource 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" "edit-
   media" link relation in document order.

11.  Atom Publishing Control Extensions

11.1  The

12.  Atom Publishing Control Namespace Controls

   This specification defines an Atom Format extension Structured Extension, as
   defined in Section 6 of [RFC4287], for publishing control called Atom Publishing Control.  The namespace name for the
   Atom Publishing Control's XML vocabulary is
   "http://example.net/appns/".  This specification uses "pub:" for within the
   namespace prefix.  The choice of namespace prefix is not semantically
   significant.

11.2
   http://purl.org/atom/app# namespace.

12.1  The "pub:control" "app:control" Element

   namespace pub app = "http://example.net/appns/" "http://purl.org/atom/app#"

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

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

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

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

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

11.2.1

12.1.1  The "pub:draft" "app:draft" Element

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

12.

13.  Securing the Atom Protocol

   All instances of publishing Atom Format entries SHOULD be protected
   by authentication to prevent posting or editing by unknown sources.
   [[anchor22:
   [[anchor23: note: this section is currently under discussion.]]

13. is currently under discussion.]]

14.  Security Considerations

   The security of the Atom Protocol is based on [[anchor25: note:
   refers to incomplete section]].

   [[anchor26: note: talk here about denial of service attacks using
   large XML files, or the billion laughs DTD attack.]]

15.  IANA Considerations

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

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

   MIME media type name: application

   MIME subtype name: atomserv+xml

   Mandatory parameters: None.

   Optional parameters:

      "charset": This parameter has identical semantics to the charset
         parameter of the "application/xml" media type as specified in
         [RFC3023].

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

   Security Considerations

   The security of considerations: As defined in this specification.
      [[anchor27: update upon publication]]

      In addition, as this media type uses the Atom Protocol is based on [[anchor24: note:
   refers to incomplete section]].

   [[anchor25: note: talk here about denial of service attacks using
   large XML files, or "+xml" convention, it
      shares the billion laughs DTD attack.]]

14.  IANA Considerations same security considerations as described in [RFC3023],
      section 10.

   Interoperability considerations: There are no known interoperability
      issues.

   Published specification: This specification. [[anchor28: update upon
      publication]]

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

   Additional information:

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

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

   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). [[anchor29:
      update upon publication]]

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

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

   MIME media type name: application

   MIME subtype name: atomserv+xml 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.
      [[anchor26:
      [[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. [[anchor27: [[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: .atomsrv .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). [[anchor28: [[anchor32:
      update upon publication]]

15.

16.  References

15.1

16.1  Normative References

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

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

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

   [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.

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

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC3987]  Duerst, M. and M. Suignard, "Internationalized Resource
              Identifiers (IRIs)", RFC 3987, January 2005.

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

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

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

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

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

15.2

16.2  Informative References

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

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

URIs

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

Authors' Addresses

   Joe Gregorio (editor)
   BitWorking, Inc
   1002 Heathwood Dairy Rd.
   Apex,
   IBM
   4205 South Miama Blvd.
   Research Triangle Park, NC  27502  27709
   US

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

Appendix A.  Contributors

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

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

   atomCommonAttributes = appCommonAttributes

   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})*"
   }

   atomDateConstruct =
       appCommonAttributes,
       xsd:dateTime
   # app:service

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

   # app:workspace

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

   atomTitle = element atom:title { atomTextConstruct }

   # app:collection

   appCollection =
      element app:collection {
         appCommonAttributes,
         attribute title href { text atomURI  },
         ( appCollection+ appAccept?

           & appCategories*
           & extensionElement* )
      }

   # app:collection

   appCollection

   # 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 }?,
           (atomCategory*)
       }

   appOutOfLineCategories =
       element app:collection app:categories {
         appCommonAttributes,
         attribute title { text },
           attribute href { atomUri atomURI },
         ( appAccept?
           & extensionElement* )
           (empty)
       }

   appCategories = appInlineCategories | appOutOfLineCategories

   # app:member app:accept

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

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

   # Simple Extension

   simpleExtensionElement =
      element * - app:* {
         text
      }

   # Structured Extension

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

   # Other Extensibility

   extensionElement =
      simpleExtensionElement | structuredExtensionElement
   undefinedContent = (text|anyForeignElement)*

   # Extensions

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

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

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

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

   atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct

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

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

   # EOF

   The Schema for Category Documents:

   # -*- rnc -*-
   # RELAX NG Compact Syntax Grammar for the Atom Protocol
   namespace app = "http://purl.org/atom/app#"
   namespace atom = "http://www.w3.org/2005/Atom"
   namespace xsd = "http://www.w3.org/2001/XMLSchema"
   namespace local = ""

   start = appCategories

   # common:attrs

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

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

   atomUri = text

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

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

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

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

   appCategories = appInlineCategories | appOutOfLineCategories
   # Extensibility

   undefinedContent = (text|anyForeignElement)*

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

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

   # EOF

Appendix C.  Revision History

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Intellectual Property Statement

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