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Network Working Group                                   J. Gregorio, Ed.
Internet-Draft                                           BitWorking, Inc
Expires: November 10, 2005                                 R. Sayre, Ed.
                                                             May 9, 2005


                      The Atom Publishing Protocol
                   draft-ietf-atompub-protocol-04.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
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts.

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   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on November 10, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This memo presents a protocol for using XML (Extensible Markup
   Language) and HTTP (HyperText Transport Protocol) to edit content.

   The Atom Publishing Protocol is an application-level protocol for
   publishing and editing Web resources belonging to periodically
   updated websites.  The protocol at its core is the HTTP transport of
   Atom-formatted representations.  The Atom format is documented in the
   Atom Syndication Format (draft-ietf-atompub-format-06.txt).



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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 . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Notational Conventions . . . . . . . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  The Atom Publishing Protocol Model . . . . . . . . . . . . . .  6
     4.1   Collections  . . . . . . . . . . . . . . . . . . . . . . .  6
     4.2   Discovery  . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.3   Listing  . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.4   Authoring  . . . . . . . . . . . . . . . . . . . . . . . .  7
       4.4.1   Create . . . . . . . . . . . . . . . . . . . . . . . .  7
       4.4.2   Read . . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.4.3   Update . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.4.4   Delete . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.5   Success and Failure  . . . . . . . . . . . . . . . . . . .  9
   5.  Collections  . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.1   Collection Documents . . . . . . . . . . . . . . . . . . . 10
       5.1.1   Element Definitions  . . . . . . . . . . . . . . . . . 10
     5.2   Collection Resource  . . . . . . . . . . . . . . . . . . . 12
       5.2.2   POST . . . . . . . . . . . . . . . . . . . . . . . . . 14
       5.2.3   Usage Scenarios  . . . . . . . . . . . . . . . . . . . 15
       5.2.4   Range: Header  . . . . . . . . . . . . . . . . . . . . 16
       5.2.5   Accept-Ranges: Header  . . . . . . . . . . . . . . . . 16
       5.2.6   Name: Header . . . . . . . . . . . . . . . . . . . . . 17
   6.  Entry Collection . . . . . . . . . . . . . . . . . . . . . . . 18
     6.1   Editing Entry Resources  . . . . . . . . . . . . . . . . . 18
     6.2   Role of Atom Entry Elements During Editing . . . . . . . . 18
   7.  Generic Collection . . . . . . . . . . . . . . . . . . . . . . 20
     7.1   Editing Generic Resources  . . . . . . . . . . . . . . . . 20
   8.  Introspection  . . . . . . . . . . . . . . . . . . . . . . . . 21
     8.1   Introspection Document . . . . . . . . . . . . . . . . . . 21
       8.1.1   Element Definitions  . . . . . . . . . . . . . . . . . 21
     8.2   Introspection Resource . . . . . . . . . . . . . . . . . . 23
       8.2.1   Discovery  . . . . . . . . . . . . . . . . . . . . . . 24
   9.  Securing the Atom Protocol . . . . . . . . . . . . . . . . . . 25
   10.   Security Considerations  . . . . . . . . . . . . . . . . . . 26
   11.   IANA Considerations  . . . . . . . . . . . . . . . . . . . . 27
   12.   References . . . . . . . . . . . . . . . . . . . . . . . . . 30
     12.1  Normative References . . . . . . . . . . . . . . . . . . . 30
     12.2  Informative References . . . . . . . . . . . . . . . . . . 31
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 32
   A.  Revision History . . . . . . . . . . . . . . . . . . . . . . . 33
       Intellectual Property and Copyright Statements . . . . . . . . 35



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1.  Introduction

   The Atom Publishing Protocol is an application-level protocol for
   publishing and editing Web resources using HTTP [RFC2616] and XML 1.0
   [W3C.REC-xml-20040204].














































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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].














































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3.  Terminology

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

   Resource - an item identified by a URI [W3C.REC-webarch-20041215].

   Collection Resource - A resource that contains a listing of Member
   Resources and meets the requirements in Section 5 of this
   specification.

   Member Resource - A resource whose URI is listed by a Collection
   Resource.





































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4.  The Atom Publishing Protocol Model

   The Atom Publishing Protocol operates on collections of Web
   resources.  All collections support the same basic interactions, as
   do the resources within the collections.  The patterns of interaction
   are based on the common HTTP verbs.

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

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

   o  PUT is used to update a known resource.

   o  DELETE is used to remove a resource.


4.1  Collections

   The APP groups resources into "Collections", which are analogous to
   the "folders" or "directories" found in many file systems.

4.2  Discovery

   To discover the location of the collections exposed by an APP
   service, the client must locate and request an Introspection Document
   (Section 8).

   Client                      Server
   |                                |
   |  1.) GET Introspection         |
   |------------------------------->|
   |                                |
   |  2.) Introspection Doc         |
   |<-------------------------------|
   |                                |

   1.  The client sends a GET request to the Service Description
       Resource.

   2.  The server responds with an Introspection Document containing the
       locations of collections provided by the service.  The content of
       this document can vary based on aspects of the client request,
       including, but not limited to, authentication credentials.







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4.3  Listing

   Once the client has discovered the location of a collection, it can
   request a listing of the collection's membership.  However,
   collections might be extremely large, so servers are likely to list a
   small subset of the collection by default.

   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 a full
       or partial listing of the collection's membership.


4.4  Authoring

   After locating a collection, a client can add entries by sending a
   request to the collection; other changes are accomplished by sending
   HTTP requests to its member resources.

4.4.1  Create

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

   1.  The client sends a representation of a member to the server via
       HTTP POST.  The Request URI is that of the Collection.

   2.  The server responds with a response of "201 Created" and a
       "Location" header containing the URI of the newly-created
       resource.






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4.4.2  Read

   Client                      Server
   |                                |
   |  1.) GET or HEAD to Member URI |
   |------------------------------->|
   |                                |
   |  2.) 200 OK                    |
   |<-------------------------------|
   |                                |


   1.  The client sends a GET (or HEAD) request to the member's URI.

   2.  The server responds with an appropriate representation.


4.4.3  Update

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

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

   2.  The server responds with a representation of the member's new
       state.


4.4.4  Delete

   Client                      Server
   |                                |
   |  1.) DELETE to Member URI      |
   |------------------------------->|
   |                                |
   |  2.) 204 No Content            |
   |<-------------------------------|
   |                                |

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

   2.  The server responds with successful status code.




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4.5  Success and Failure

   HTTP defines classes of response.  HTTP status codes of the form 2xx
   signal that a request was successful.  HTTP status codes of the form
   4xx or 5xx signal that an error has occurred, and the request has
   failed.  Consult the HTTP specification for more detailed definitions
   of each status code.












































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5.  Collections

   An Atom Collection is a set of related resources.  All members of a
   collection have an "updated" property, and the collection is
   considered to be ordered by this property.

5.1  Collection Documents

   An example Collection Document.

   <?xml version="1.0" encoding='utf-8'?>
   <collection xmlns="http://purl.org/atom/app#">
     <member href="http://example.org/1"
             hrefreadonly="http://example.com/1/bar"
             title="Sample 1"
             updated="2003-12-13T18:30:02Z" />
     <member href="http://example.org/2"
             hrefreadonly="http://example.com/2/bar"
             title="Sample 2"
             updated="2003-12-13T18:30:02Z" />
     <member href="http://example.org/3"
             hrefreadonly="http://example.com/3/bar"
             title="Sample 3"
             updated="2003-12-13T18:30:02Z" />
     <member href="http://example.org/4"
             title="Sample 4"
             updated="2003-12-13T18:30:02Z" />
   </collection>

   Atom Collection Documents have the media-type 'application/
   atomcoll+xml', see Section 11.

5.1.1  Element Definitions

5.1.1.1  The 'app:collection' Element

   The 'app:collection' element represents an Atom Collection.  A
   collection document does not necessarily list every member of the
   collection.


   appCollection       element app:collection {
         attribute next { text } ?,
         appMember*
      }





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   o  'app:collection' elements MAY contain any number of 'app:member'
      elements.

   o  'app:collection' elements MAY contain a 'next' attribute which
      identifies a collection document containing member elements
      updated earlier in time.

   The members listed in a collection document MUST constitute a
   consecutive sequence of the collection's members, ordered by their
   "updated" properties.  That is, a collection document MUST contain a
   contiguous subset of the members of the collection ordered by their
   'updated' property.

5.1.1.2  The 'app:member' Element

   The 'app:member' represents a single member resource.


   appMember       element app:member {
         attribute title { text },
         attribute href { text },
         attribute hrefreadonly { text } ?,
         attribute updated { text }
      }


   o  'app:member' elements MUST include an 'href' attribute, whose
      value conveys the URI used to edit the member source

   o  'app:member' elements MAY include an "hrefreadonly
      (Section 5.1.1.3)" attribute.

   o  'app:member' elements MUST include a 'title' attribute, whose
      value is a human-readable name or description for the item.

   o  'app:member' elements MUST include an 'updated' attribute, whose
      value is the 'updated' property of the collection member.  Its
      format MUST conform to the date-time production in [RFC3339].


5.1.1.3  The 'hrefreadonly' Attribute

   This optional attribute identifies a URI which, on a GET request,
   responds equivalently to how the "href" URI would respond to the same
   request.  Clients SHOULD NOT apply to this URI any HTTP methods that
   would be expected to modify the state of the resource (e.g.  PUT,
   POST or DELETE).  A PUT or POST request to this URI MAY NOT affect



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   the underlying resource.  If the "hrefreadonly" attribute is not
   given, its value defaults to the "href" value.  If the "hrefreadonly"
   attribute is present, and its value is an empty string, then there is
   no URI that can be treated in the way such a value would be treated.

   Clients SHOULD use the "href" value to manipulate the resource within
   the context of the APP itself.  Clients SHOULD prefer the
   "hrefreadonly" value in any other context.  For example, if the
   resource is an image, a client may replace the image data using a PUT
   on the "href" value, and may even display a preview of the image by
   fetching the "href" URI.  But when creating a public, read-only
   reference to the same image resource, the client should use the
   "hrefreadonly" value.  If the "hrefreadonly" value is an empty
   string, the client SHOULD NOT make public reference to the "href"
   value.

   [[anchor10: Define extensibility for Collection Documents.]]

5.2  Collection Resource

   This specification defines two HTTP methods for use with collection
   resources: GET and POST.

5.2.1  GET

   Collections can contain extremely large numbers of resources.  A
   naive client such as a web spider or web browser would be overwhelmed
   if the response to a GET reflected the full membership of the
   collection, and the server would waste large amounts of bandwidth and
   processing time on clients unable to handle the response.  As a
   result, responses to a simple GET request represent a server-
   determined subset of the collection's membership.

   In addition, the client MAY send a 'Range' header with a range type
   of 'udpated', indicating the subset of the collection to be returned.
   The 'Range' header is described in Section 5.2.4.

   This specification defines two serializations for Atom Collections.
   Servers MUST provide both, but MAY also provide additional
   serializations.

   1.  Atom Collection Documents (application/atomcoll+xml),
       Section 5.1.

   2.  Atom Collection Documents wrapped by a SOAP envelope
       (application/soap+xml), .

   Clients use the HTTP 'Accept' request header to indicate their



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   preference.

   Example Request, with Accept header

   GET /collection HTTP/1.1
   Host: example.org
   User-Agent: Agent/1.0
   Accept: application/atomcoll+xml

   Here, the server could return any subset of the collection as an Atom
   Collection Document.

   Example Response, Atom Collection Document

   HTTP/1.1 200 OK
   Date: Fri, 25 Mar 2005 17:15:33 GMT
   Last-Modified: Mon, 04 Oct 2004 18:31:45 GMT
   ETag: "2b3f6-a4-5b572640"
   Accept-Ranges: updated
   Content-Length: nnnn
   Content-Type: application/atomcoll+xml; charset="utf-8"

   <?xml version="1.0" encoding="utf-8"?>
   <collection xmlns="http://purl.org/atom/app#">
   ...
     <member href="http://example.org/1"
             hrefreadonly="http://example.com/1/bar"
             title="Example 1"
             updated="2003-12-13T18:30:02Z" />
   ...
   </collection>


   Example Request, with SOAP Accept header

   GET /collection HTTP/1.1
   Host: example.org
   User-Agent: Cosimo/1.0
   Accept: application/soap+xml

   Here, the server could return any subset of the collection as an Atom
   Feed Document wrapped by a SOAP envelope.









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   Example Response, Atom Feed Document wrapped by a SOAP envelope

   HTTP/1.1 200 OK
   Date: Fri, 25 Mar 2005 17:15:33 GMT
   Last-Modified: Mon, 04 Oct 2004 18:31:45 GMT
   ETag: "2b3f6-a4-5b572640-89"
   Accept-Ranges: bytes
   Content-Length: nnnn
   Content-Type: application/soap+xml; charset="utf-8"

   <?xml version="1.0" encoding="utf-8"?>
   <env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope">
      <env:Header />
      <env:Body>
         <collection xmlns="http://purl.org/atom/app#">
         ...
         <member href="http://example.org/1"
                 hrefreadonly="http://example.com/1/bar"
                 title="Example 1"
                 updated="2003-12-13T18:30:02Z" />
         ...
         </collection>
      </env:Body>
   </env:Envelope>


5.2.2  POST

   In addition to GET, a Collection Resource also accepts POST requests.
   The client POSTs a representation of the desired resource to the
   Collection Resource.  Note that some collections only allow members
   of a specific media-type and a POST MAY generate a response with a
   status code of 415 ("Unsupported Media Type").

   In the case of a successful creation, the status code MUST be 201
   ("Created").















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   Example Request, Create a resource in a collection.

   POST /collection HTTP/1.1
   Host: example.org
   User-Agent: Cosimo/1.0
   Accept: application/atomcoll+xml
   Content-Type: image/png
   Content-Length: nnnn
   Name: trip-to-beach.png

   ...binary data...

   Here, the client is adding a new image resource to a collection.  The
   Name: header indicates the client's desired name for the resource,
   see Section 5.2.6.

   Example Response, resource created successfully.

   HTTP/1.1 201 Created
   Date: Fri, 25 Mar 2005 17:17:11 GMT
   Content-Length: nnnn
   Content-Type: application/atomcoll+xml; charset="utf-8"
   Location: http://example.org/images/trip-to-the-beach-01.png

   <?xml version="1.0" encoding="UTF-8"?>
   <collection xmlns="http://purl.org/atom/app#">
       <member href="http://example.org/images/trip-to-beach.png"
           hrefreadonly="http://example.com/ed/im/trip-01.png"
           title="trip-to-beach.png"
           updated="2005-03-25T17:17:09Z" />
   </collection>


5.2.3  Usage Scenarios

   These scenarios illustrate common idioms for interactin with
   Collections.

   The Atom Collection can be used by clients in two ways.  In the first
   case the client encounters a Collection for the first time and is
   doing an initial syncronization, that is, retrieving a list of all
   the members of the collections and possibly retrieving all the
   members of the collection also.  The client can perform a non-partial
   GET on the collection resource and it will receive a collection
   document that either contains all the members of the collection, or
   the collection document root element 'collection' will contain a
   'next' attribute pointing to the next collection document.  By
   repeatedly following the 'next' attribute from document to document



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   the client can find all the members of the collection.

   In the second case the client has already done an initial sync, and
   now needs to re-sync, because the client was just restarted, or some
   time has passed since a re-sync, etc.  The client does a partial GET
   on the collection document, supplying a Range header that begins from
   the last time the client sync'd to the current time.  The collection
   document returned will contain only those members of the collection
   that have changed since the last time the client syncronized.

5.2.4  Range: Header

   HTTP/1.1 allows a client to request that only part (a range of) the
   collection to be included within the response.  HTTP/1.1 uses range
   units in the Range header field.  A collection can be broken down
   into subranges according to the members 'updated' property.  If a
   Range: header is present in the request, its value explictly
   identifies the a time interval interval in which all the members
   'updated' property must fall to be included in the response.

      Range = "Range" ":" ranges-specifier

   The value of the Range: header should be a pair of ISO 8601 dates,
   separated by a slash character; either date may be optionally
   omitted, in which case the range is understood as stretching to
   infinity on that end.

      ranges-specifier = updated-ranges-specifier
      updated-ranges-specifier = updated-unit "=" updated-range
      updated-unit = "updated"
      updated-range = [iso-date] "/" [iso-date]

   The response to a collection request MUST be a collection document,
   all of whose 'member' elements fall within the requested range.  The
   request range is considered a closed set, that is, if a 'member'
   element matches one end of the range exactly it MUST be included in
   the response.  If no members fall in the requested range, the server
   MUST respond with a collection document containing no 'member'
   elements.

   The inclusion of the Range: header in a request changes the request
   to a "partial GET" [RFC2616].

5.2.5  Accept-Ranges: Header

   The response to a non-partial GET request MUST include an Accept-
   Ranges header that indicates that the server accepts 'updated' range
   requests.



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     Accept-Ranges     = "Accept-Ranges" ":" acceptable-ranges
     acceptable-ranges = updated-unit ( 1#range-unit )


5.2.6  Name: Header

   [[anchor13: this is new...]]

   The POST to a Collection Resource MAY contain a Name: header that
   indicates the clients suggested name for the resource.  The server
   MAY ignore the Name: header or modify the requested name to suit
   local conventions.

     Name     = "Name" ":" relative-part

   The relative-part production is defined in [RFC3986].



































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6.  Entry Collection

   Entry Collections are Collections that restrict their membership to
   Atom entries.  This specification defines two serializations for Atom
   entries.  Servers MUST provide both serializations.

   1.  Atom Entry Documents (application/atom+xml),  [AtomFormat].

   2.  Atom Entry Documents wrapped by a SOAP envelope (application/
       soap+xml), .

   Clients use the HTTP 'Accept' request header to indicate their
   preference [RFC2616].  If no 'Accept' header is present in the
   request, the server is free to choose any serialization.  When an
   HTTP request contains a body, clients MUST include a 'Content-Type'
   header, and servers MUST accept both application/atom+xml and
   application/soap+xml message bodies.

6.1  Editing Entry Resources

   Atom entries are edited by sending HTTP requests to an individual
   entry's URI.  Servers can determine the processing necessary to
   interpret a request by examining the request's HTTP method and
   'Content-Type' header.

   If the request method is POST and the 'Content-Type' is application/
   soap+xml, the SOAP document MUST contain a Web-Method property .
   This specifcation defines two values for that property, PUT and
   DELETE.

   Processing Client Requests

 +----------------------------------+------+--------+--------+--------+
 |                                  |  GET |   PUT  | DELETE |  POST  |
 +----------------------------------+------+--------+--------+--------+
 |                          No Body | Read |    x   | Delete |    x   |
 |                                  |      |        |        |        |
 |                        Atom Body |   x  | Update |    x   |    x   |
 |                                  |      |        |        |        |
 |    SOAP Body with Web-Method PUT |   x  |    x   |    x   | Update |
 |                                  |      |        |        |        |
 | SOAP Body with Web-Method DELETE |   x  |    x   |    x   | Delete |
 +----------------------------------+------+--------+--------+--------+


6.2  Role of Atom Entry Elements During Editing

   The elements of an Atom Entry Document are either a 'Writable



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   Element' or a 'Round Trip Element'.

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

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

   That categorization will determine the elements' disposition during
   editing.

                  +--------------------+------------+
                  | Atom Entry Element |  Property  |
                  +--------------------+------------+
                  |     atom:author    |  Writable  |
                  |                    |            |
                  |    atom:category   |  Writable  |
                  |                    |            |
                  |    atom:content    |  Writable  |
                  |                    |            |
                  |  atom:contributor  |  Writable  |
                  |                    |            |
                  |       atom:id      | Round Trip |
                  |                    |            |
                  |      atom:link     |  Writable  |
                  |                    |            |
                  |   atom:published   |  Writable  |
                  |                    |            |
                  |     atom:source    |  Writable  |
                  |                    |            |
                  |    atom:summary    |  Writable  |
                  |                    |            |
                  |     atom:title     |  Writable  |
                  |                    |            |
                  |    atom:updated    | Round Trip |
                  +--------------------+------------+

                                  Table 2













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7.  Generic Collection

   Generic Collections are Collections that do not have uniform
   restrictions on the representations of the member resources.

7.1  Editing Generic Resources

   Member resources are edited by sending HTTP requests to an individual
   resource's URI.  Servers can determine the processing necessary to
   interpret a request by examining the request's HTTP method and
   'Content-Type' header.

   Processing Client Requests

              +----------+------+--------+--------+------+
              |          |  GET |   PUT  | DELETE | POST |
              +----------+------+--------+--------+------+
              |  No Body | Read |    x   | Delete |   x  |
              |          |      |        |        |      |
              | Any Body |   x  | Update |    x   |   x  |
              +----------+------+--------+--------+------+






























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8.  Introspection

   In order for authoring to commence, a client must first discover the
   capabilities and locations of collections offered.

8.1  Introspection Document

   The Introspection Document describes "workspaces", which are server-
   defined groupings of collections.  There is no requirement that
   servers support multiple workspaces, and a collection may appear in
   more than one workspace.

   The Introspection Document has the media-type 'application/
   atomserv+xml', see Section 11

   <?xml version="1.0" encoding='utf-8'?>
   <service xmlns="http://purl.org/atom/app#">
     <workspace title="Main Site" >
       <collection contents="entries" title="My Blog Entries"
         href="http://example.org/reilly/feed" />
       <collection contents="generic" title="Documents"
         href="http://example.org/reilly/pic" />
     </workspace>
     <workspace title="Side Bar Blog">
       <collection contents="entries" title="Entries"
         href="http://example.org/reilly/feed" />
       <collection contents="http://example.net/booklist" title="Books"
         href="http://example.org/reilly/books" />
     </workspace>
   </service>

8.1.1  Element Definitions

8.1.1.1  The 'app:service' Element

   The "service" element is the document element of a Service Document,
   acting as a container for service data associated with one or more
   workspaces.


   appService       element app:service {
         ( appWorkspace*
           & anyElement* )
      }


   The following child elements are defined by this specification:



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   o  app:service elements MAY contain any number of app:workspace
      elements.


8.1.1.2  The 'app:workspace' Element

   The 'workspace' element element contains information elements about
   the collections of resources available for editing.


   appWorkspace       element app:workspace {
         attribute title { text },
         ( appCollection*
           & anyElement* )
      }


   The following attributes and child elements are defined by this
   specification:

   o  app:workspace elements MUST contain a 'title' attribute, which
      conveys a human-readable name for the workspace

   o  app:workspace elements MAY contain any number of app:collection
      elements.


8.1.1.3  The 'app:collection' Element

   The 'app:collection' element describes collections and their member
   resources.

   [[anchor19: We have a collection element that's different than the
   root element of the collection document.  Messy. --R.  Sayre]]


   appCollection       element app:collection {
         attribute title { text },
         attribute contents { text },
         attribute href { text },
         anyElement*
      }


   The following attributes are defined by this specification:




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   o  app:collection elements MUST contain a 'title' attribute, whose
      value conveys a human-readable name for the workspace

   o  app:collection elements MAY contain a 'contents' attribute
      (Section 8.1.1.3.1).  If it is not present, it's value is
      considered to be 'generic'.

   o  app:collection elements MUST contain an 'href' attribute, whose
      value conveys the URI of the collection.


8.1.1.3.1  The 'contents' Attribute

   The 'contents' attribute conveys the nature of a collection's member
   resources.  This specification defines two initial values for the
   'contents' attribute:

   o  entry

   o  generic

   Extensibility for 'content' values is handled [[anchor20: Same as
   atom:link]].

8.1.1.3.1.1  entry

   A value of 'entry' for the contents attribute indicates that the
   Collection is an Entry Collection (Section 6).

8.1.1.3.1.2  generic

   A value of 'generic' for the contents attribute indicates that the
   Collection is a Generic Collection (Section 7).

8.2  Introspection Resource

   To retrieve an Introspection Document, the client sends a GET request
   to its URI.

   GET /service-desc HTTP/1.1
   Host: example.org
   User-Agent: Cosimo/1.0
   Accept: application/atomserv+xml

   The server responds to a GET request by returning an Introspection
   Document in the message body.





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   HTTP/1.1 200 OK
   Date: Mon, 21 Mar 2005 19:20:19 GMT
   Server: CountBasic/2.0
   Last-Modified: Mon, 21 Mar 2005 19:17:26 GMT
   ETag: "4c083-268-423f1dc6"
   Content-Length: nnnn
   Content-Type: application/atomserv+xml

   <?xml version="1.0" encoding='utf-8'?>
   <service xmlns="http://purl.org/atom/app#">
       ...
   </service>


8.2.1  Discovery

   [[anchor24: Add in desc of an HTML link element that points to the
   Introspection Resource, or add it to the autodisco draft]]

































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9.  Securing the Atom Protocol

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

   o  HTTP Digest Authentication [RFC2617]

   o  [@@TBD@@ CGI Authentication ref]

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

   There are cases where an authentication mechanism may not be
   required, such as a publicly editable Wiki, or when using the PostURI
   to post comments to a site that does not require authentication to
   create comments.

9.1  [@@TBD@@ CGI Authentication]

   This authentication method is included as part of the protocol to
   allow Atom servers and clients that cannot use HTTP Digest
   Authentication but where the user can both insert its own HTTP
   headers and create a CGI program to authenticate entries to the
   server.  This scenario is common in environments where the user
   cannot control what services the server employs, but the user can
   write their own HTTP services.























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10.  Security Considerations

   Because Atom is a publishing protocol, it is important that only
   authorized users can create and edit entries.

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

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

   See RFC 2617 for more detailed description of the security properties
   of HTTP Digest Authentication.

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

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



























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11.  IANA Considerations

   A Atom Collection Document, when serialized as XML 1.0, can be
   identified with the following media type:

   MIME media type name: application

   MIME subtype name: atomcoll+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.
      [[anchor28: 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. [[anchor29: 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: .atomcoll

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






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

   Macintosh File Type code: TEXT

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

   Intended usage: COMMON

   Author/Change controller: IESG

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

   MIME media type name: application

   MIME subtype name: atomserv+xml

   Mandatory parameters: None.

   Optional parameters:

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

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

   Security considerations: As defined in this specification.
      [[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:





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   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). [[anchor32:
      update upon publication]]
































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12.  References

12.1  Normative References

   [AtomFormat]
              Nottingham, M. and R. Sayre, "The Atom Syndication
              Format",  work-in-progress, April 2005.

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

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

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

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

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

   [RFC3339]  Klyne, G. and C. Newman, "Date and Time on the Internet:
              Timestamps", RFC 3339, July 2002.

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

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

   [W3C.REC-soap12-part1-20030624]
              Nielsen, H., Mendelsohn, N., Gudgin, M., Hadley, M., and
              J. Moreau, "SOAP Version 1.2 Part 1: Messaging Framework",
              W3C REC REC-soap12-part1-20030624, June 2003.

   [W3C.REC-soap12-part2-20030624]
              Nielsen, H., Hadley, M., Moreau, J., Mendelsohn, N., and
              M. Gudgin, "SOAP Version 1.2 Part 2: Adjuncts", W3C
              REC REC-soap12-part2-20030624, June 2003.

   [W3C.REC-xml-20040204]
              Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T.,



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              and E. Maler, "Extensible Markup Language (XML) 1.0 (Third
              Edition)", W3C REC REC-xml-20040204, February 2004.

12.2  Informative References

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










































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URIs

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


Authors' Addresses

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

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


   Robert Sayre (editor)

   Email: rfsayre@boswijck.com
   URI:   http://boswijck.com





























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Appendix A.  Revision History

   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 it's purpose.

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



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

   Rev 03 - 10Jul2003 - Added a link to the Wiki near the front of the
   document.  Added a section on finding an Entry.  Retrieving an Entry
   now broken out into it's 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 it's own section.  Added
   the Revision History section.  Added more to the warning that the
   example URIs are not normative.





























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Intellectual Property Statement

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Disclaimer of Validity

   This document and the information contained herein are provided on an
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   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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Copyright Statement

   Copyright (C) The Internet Society (2005).  This document is subject
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   except as set forth therein, the authors retain all their rights.





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Acknowledgment

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















































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