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Network Working Group                                   J. Gregorio, Ed.
Internet-Draft                                           BitWorking, Inc
Expires: March 22, 2005                                    R. Sayre, Ed.
                                               Boswijck Memex Consulting
                                                      September 21, 2004



                      The Atom Publishing Protocol
                   draft-ietf-atompub-protocol-02.txt


Status of this Memo


   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3668.


   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as
   Internet-Drafts.


   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."


   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.


   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.


   This Internet-Draft will expire on March 22, 2005.


Copyright Notice


   Copyright (C) The Internet Society (2004).  All Rights Reserved.


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-02.txt).




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Editorial Note


   To provide feedback on this Internet-Draft, join the
   <http://www.imc.org/atom-syntax/index.html>.


Table of Contents


   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1  Notational Conventions . . . . . . . . . . . . . . . . . .   4
     1.2  Terminology  . . . . . . . . . . . . . . . . . . . . . . .   4
   2.   The Atom Publishing Protocol Model . . . . . . . . . . . . .   4
   3.   Functional Specification . . . . . . . . . . . . . . . . . .   5
     3.1  PostURI  . . . . . . . . . . . . . . . . . . . . . . . . .   5
       3.1.1  Locating the PostURI . . . . . . . . . . . . . . . . .   5
       3.1.2  Request  . . . . . . . . . . . . . . . . . . . . . . .   5
       3.1.3  Response . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2  EditURI  . . . . . . . . . . . . . . . . . . . . . . . . .   7
       3.2.1  Locating . . . . . . . . . . . . . . . . . . . . . . .   7
       3.2.2  Request  . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3  FeedURI  . . . . . . . . . . . . . . . . . . . . . . . . .   9
       3.3.1  Locating . . . . . . . . . . . . . . . . . . . . . . .  10
       3.3.2  Request  . . . . . . . . . . . . . . . . . . . . . . .  10
       3.3.3  Response . . . . . . . . . . . . . . . . . . . . . . .  10
     3.4  ResourcePostURI  . . . . . . . . . . . . . . . . . . . . .  10
       3.4.1  Locating . . . . . . . . . . . . . . . . . . . . . . .  10
       3.4.2  Request  . . . . . . . . . . . . . . . . . . . . . . .  11
       3.4.3  Response . . . . . . . . . . . . . . . . . . . . . . .  11
     3.5  Link Tag . . . . . . . . . . . . . . . . . . . . . . . . .  12
       3.5.1  rel  . . . . . . . . . . . . . . . . . . . . . . . . .  12
       3.5.2  href . . . . . . . . . . . . . . . . . . . . . . . . .  12
       3.5.3  title  . . . . . . . . . . . . . . . . . . . . . . . .  13
       3.5.4  type . . . . . . . . . . . . . . . . . . . . . . . . .  13
     3.6  Atom Request and Response Body Constraints . . . . . . . .  13
       3.6.1  id . . . . . . . . . . . . . . . . . . . . . . . . . .  13
       3.6.2  link . . . . . . . . . . . . . . . . . . . . . . . . .  13
       3.6.3  title  . . . . . . . . . . . . . . . . . . . . . . . .  13
       3.6.4  summary  . . . . . . . . . . . . . . . . . . . . . . .  14
       3.6.5  content  . . . . . . . . . . . . . . . . . . . . . . .  14
       3.6.6  issued . . . . . . . . . . . . . . . . . . . . . . . .  14
       3.6.7  modified . . . . . . . . . . . . . . . . . . . . . . .  15
       3.6.8  created  . . . . . . . . . . . . . . . . . . . . . . .  15
       3.6.9  author . . . . . . . . . . . . . . . . . . . . . . . .  15
       3.6.10   contributor  . . . . . . . . . . . . . . . . . . . .  15
       3.6.11   generator  . . . . . . . . . . . . . . . . . . . . .  15
     3.7  Securing the Atom Protocol . . . . . . . . . . . . . . . .  16
       3.7.1  [@@TBD@@ CGI Authentication] . . . . . . . . . . . . .  16
   4.   Security Considerations  . . . . . . . . . . . . . . . . . .  16
   5.   IANA Considerations  . . . . . . . . . . . . . . . . . . . .  17




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   6.   Appendix A - SOAP Enabling . . . . . . . . . . . . . . . . .  17
     6.1  Servers  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.2  Clients  . . . . . . . . . . . . . . . . . . . . . . . . .  17
   7.   Appendix B - Examples  . . . . . . . . . . . . . . . . . . .  17
     7.1  Example for a weblog . . . . . . . . . . . . . . . . . . .  17
     7.2  Example for a wiki . . . . . . . . . . . . . . . . . . . .  18
   8.   Revision History . . . . . . . . . . . . . . . . . . . . . .  18
   9.   Normative References . . . . . . . . . . . . . . . . . . . .  19
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  20
        Intellectual Property and Copyright Statements . . . . . . .  21










































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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.


1.1  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].


1.2  Terminology


   Atom Entry: An Atom Entry is a fragment of a full Atom feed.  In this
      case, the fragment is a single 'entry' element and all its child
      elements.  Each Atom Entry describes a single Web resource,
      providing metadata and optionally a textual representation of that
      resource.
   PostURI: A URI that is used to create new resources.  POSTing an Atom
      Entry to this URI will create a new resource.
   EditURI: A URI that is used to edit a resource.  The editing is done
      using the HTTP verbs GET, PUT and DELETE.  The representation of
      the resource is always that of an Atom Entry.
   FeedURI: The URI which identifies an Atom Feed.


2.  The Atom Publishing Protocol Model


   The Atom Publishing Protocol is an application-level protocol for
   publishing and editing Web resources.  Using the common HTTP verbs
   provides a pattern for working with all such Web resources:
   o  GET is used to retrieve a representation of a resource or perform
      a read-only query.
   o  PUT is used to update a known resource.
   o  POST is used to create a new dynamically-named resource.
   o  DELETE is used to remove a resource.


   There are four major classes of URI [RFC2396] in this specification:
   PostURI, ResourcePostURI, FeedURI, and EditURI.  This specification
   defines the expected actions for each of the methods listed.  A URI
   MAY support methods not listed here.  For example, an EditURI could
   support a POST or OPTIONS method.  However, what those methods do is
   beyond the scope of this specification.
   o  EditURI: PUT, GET, DELETE
   o  PostURI: POST
   o  FeedURI: GET
   o  ResourcePostURI: POST


   This document does not specify the form of the URIs that are used.




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   The URI space of each server is controlled, as defined by HTTP, by
   the server alone.  What this document does specify are the formats of
   the files that are exchanged and the actions that can be performed on
   the URIs embedded in those files.


3.  Functional Specification


3.1  PostURI


   The PostURI is used to create entries.  These can be either full
   entries, such as a weblog post, or they can be comments, or even a
   wiki page.  The client POSTs a filled-in Atom Entry to this URI.  If
   the request is successful, one or more Web resources MAY be created.
   For example, POSTing an Atom entry to a PostURI may create two new
   Web resources, an HTML representation and an Atom representation.


3.1.1  Locating the PostURI


   The PostURI can be discovered in a link element with an @rel of
   'service.post'.  The link element containing a PostURI used to create
   a new entry MAY be discovered in three different places.  The first
   place it may be found is in a <link> element in the 'head' element of
   an HTML document.


   The second place a PostURI may be found an atom:link element that is
   a child of the atom:feed element.  The third place a PostURI may be
   found is in the atom:link element of an atom:entry.


   @@ TBD @@ - Discuss subordinate resources and what a PostURI means
   based on where the URI was found.


   <link rel="service.post"
         type="application/atom+xml"
         href="URI for Posting goes here"
         title="The name of the site." />


3.1.2  Request


   The request contains a filled-in Atom entry, subject to the
   constraints in section Section 3.6.


3.1.3  Response


   The possible status codes from a POST are 201, 303, 400, 404, 409,
   410 and 500.







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3.1.3.1  Response code 201


   The Response MUST include a Location: header with the URI of the
   created resource.  The URI returned must be the EditURI of the entry
   just created.  The body of the response SHOULD contain the newly
   created entry.  If the entry is present in the response body then it
   MUST conform to the same constraints listed for responses to a GET on
   an EditURI.  User agents MUST NOT depend on the server returning a
   response body.  If the server does return a response body then the
   user agents MUST NOT depend on the response body having a
   content-type of 'application/atom+xml".  Note that the server may
   choose to omit the content in the response, particularly if it is
   large.


   A 201 response MAY contain an ETag response header field indicating
   the current value of the entity tag for the requested variant just
   created.


   If the entry returned is subsequently changed the user agent can
   update the entry by submitting it via PUT to the EditURI.  If an ETag
   was returned with the creation of the entry then the user agent
   SHOULD include an If-Match: header in the request that contains that
   ETag.


3.1.3.2  Response code 303


   The body of this response does not contain the filled-in Entry, but
   the filled-in Entry can be found under a different URI and can be
   retrieved using a GET method on that resource.  The URI SHOULD be
   given by the Location field in the response.


3.1.3.3  Response code 400


   Indicates that the server believes that the data sent constitutes an
   invalid request.  As an example, the data posted may not be
   well-formed XML.  The server SHOULD include an entity containing an
   explanation of the error situation, and whether it is a temporary or
   permanent condition.


3.1.3.4  Response code 409


   The request contained a valid Atom Entry, but it conflicts with state
   on the server.  The response SHOULD contain enough for information
   for the user to resolve the conflict.


   [[@@TBD@@ more about response body format]]






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3.1.3.5  Response code 500


   Indicates that the server detected an internal error on the server
   processing this request (such as an unhandled exception).  The server
   SHOULD include an entity containing an explanation of the error
   situation, and whether it is a temporary or permanent condition.


3.2  EditURI


   An EditURI is used to edit a single entry.  Each entry that is
   editable MUST have a unique URI.  This URI supports both GET and PUT
   and they are used in tandem for an editing cycle.  The client GETs
   the representation which is formatted as an Atom entry.  The client
   may then update the entry and then PUT it back to the same URI.  The
   PUT will cause all the related resources to be updated, for example,
   the HTML representation.


   Note that the value of the content element in the Atom entry does not
   have to exactly match the content element for the same entry when it
   is represented in an Atom feed.  For example, a server may allow the
   client to post entries whose content is formatted as WikiML, yet the
   server may clean up such markup and transform it into well-formed
   XHTML before placing it in the publicly available Atom feed.  Another
   scenario is summaries--the EditURI is for editing the full content of
   an entry, but the server may only present excerpts when it produces
   an Atom feed.


   A client will send a DELETE to the EditURI to delete an entry.


3.2.1  Locating


   For editing a site Entry, the link tag is used.  Note that a link tag
   is used in both HTML and in the Atom format.  A link tag of the
   following format points to the EditURI for a site.  In HTML, the link
   tags for editing are always found in the head element, while in Atom
   they may appear as children of the entry elements.


   <link rel="service.edit"
         type="application/atom+xml"
         href="URI for Editing goes here"
         title="Readable desc of the entry." />


   Note: The critical characteristic of this link tag is the @rel of
   'service.edit' and the @type of 'application/atom+xml'.


3.2.2  Request


   A PUT request, and a GET response both contain a filled-in Atom




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   entry, subject to the constraints in section Section 3.6.


   The expected status codes from a GET are 200, 301, 307, and 500.
   400, 404, and 410 are also possible.


   The expected status codes from a PUT are 2xx, 301, 307, 500 and 501.
   400, 404, 409, and 410 are also possible.


3.2.2.1  Successful Requests


   Servers MUST indicate successful GET requests with a 200 response.


   Servers MUST indicate successful PUT requests with a 2xx response.
   Servers MAY include additional information in the PUT response.
   Clients SHOULD NOT expect any additional information in a PUT
   response.


3.2.2.2  Response code 301


   The entry has moved permanently, the new URI is given in the Location
   header.  The client SHOULD retry the GET using the URI returned in
   the Location header.  When a PUT operation is attempted the user
   agent should prompt the user before attempting the PUT on the URI
   returned in the Location header.


3.2.2.3  Response code 307


   The entry has moved temporarily, the new URI is given in the Location
   header.  The client SHOULD retry the GET using the URI returned in
   the Location header.  When a PUT operation is attempted the user
   agent should prompt the user before attempting the PUT on the URI
   returned in the Location header.


3.2.2.4  Response code 401


   Indicates that the server believes that the data sent constitutes an
   invalid request.  As an example, the data posted may not be
   well-formed XML.  The server SHOULD include an entity containing an
   explanation of the error situation, and whether it is a temporary or
   permanent condition.


3.2.2.5  Response code 409


   The request contained a valid Atom Entry, but it conflicts with the
   state of the resource, or other state on the server.


   For example, a server could signal that the client has erred in this
   manner if it receives a request containing an atom:id element whose




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   value differs from that of the resource found at the requested URI.


   The response SHOULD contain enough for information for the user to
   resolve the conflict.


   [[@@TBD@@ more about response body format ]]


3.2.2.6  Response code 410


   Indicates that the requested resource is gone permanently.  The
   client SHOULD NOT repeat the request.


3.2.2.7  Response code 500


   Indicates that the server detected an internal error on the server
   processing this request (such as an unhandled exception).  The server
   SHOULD include an entity containing an explanation of the error
   situation, and whether it is a temporary or permanent condition.


3.3  FeedURI


   The FeedURI is used to retrieve a representation in Atom format.
   Note that this feed is different from a typical Atom feed in that it
   contains "link" elements for navigating and manipulating the content
   of the site.  For example there should be a "link" element with
   rel="next" whose URI points to the next block of entries on the site.
   Similarly, the feed element can contain a "link" element with
   rel="service.post", the URI of which is a PostURI.  Individual
   entries should contain "link" elements with rel="service.edit" whose
   URIs are EditURIs.


   This document only uses some of the methods available for each type
   of URI.  For example, the only method described by this document for
   the FeedURI is GET.  Any other method may be supported by the URI
   types described, but defining their behavior is beyond the scope of
   this document.  In this light you may notice that the PostURI only
   supports the POST method.  It is possible, and allowable, that for
   some implementations the PostURI and the FeedURI are the same URI.


   @@ Editor's Note: @@ Note that the "service.feed" takes the place of
   the Introspection File and the Search facet in previous versions of
   the specification.  That is, facet discovery, which was previously
   done by inspecting the Introspection file is now done by looking for
   "link" tags with an attribute "rel" set to "service.[something]" in
   the "service.feed" file.  At the same time the same representation
   replaces the search facet by having "link" tags that point to other
   feeds using well-known 'rel' attribute values such as 'next' and
   'prev', or the search can branch in multiple directions by specifying




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   multiple link tags with rel="service.feed" and having differing title
   attributes that announce the kind of search results in that feed.


3.3.1  Locating


   A link tag of the following format points to the FeedURI.


   <link rel="service.feed"
         type="application/atom+xml"
         href="URI goes here"
         title="The name of the site." />


3.3.2  Request


   The request is a simple GET.  No other verbs are currently specified
   for this URI.


3.3.3  Response


   The expected status codes from a GET are 200, 301, 307, and 500.
   401, 404, and 410 are also possible.


3.3.3.1  Response code 301


   The Feed has moved permanently, the new URI is given in the Location
   header.  The client SHOULD do a GET on the URI returned in the
   Location header.


3.3.3.2  Response code 307


   The Feed has moved temporarily, the new URI is given in the Location
   header.  The client SHOULD do a GET on the URI returned in the
   Location header.


3.4  ResourcePostURI


   The ResourcePostURI is used to create new non-entry resources.  The
   client POSTs a resource of the desired MIME type directly to this
   URI.


3.4.1  Locating


   For creating a new non-entry resource, the link tag is used.  Note
   that a link tag is used in both HTML and in the Atom format.  A link
   tag of the following format points to the ResourcePostURI for a site.
   In HTML the link tags are always found in the head element, while in
   Atom they may appear as children of the Feed and entry elements.





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   <link rel="resource.post" href="URI for Resource Posting goes here"
   title="The name of the site.">


3.4.2  Request


   The request contains a resource, sent through a standard HTTP POST,
   e.g.:


   POST /_do/exampleblog/post_resource HTTP/1.1
   Host: www.example.com
   Content-Type: image/jpeg
   Content-Length: nnn


   ...raw bytes of image go here...



3.4.3  Response


   The expected status codes from a POST are 201, 303, 400, 415, and
   500.  401, 404, 409, and 410 are also possible.


3.4.3.1  Response code 201


   The response MUST include a Location: header with the URI of the
   created resource, i.e.  the URI used to retrieve the resource
   representation in a subsequent HTTP GET.  The server SHOULD omit the
   content of the resource in the response, since it would be redundant
   to return it to the client.


3.4.3.2  Response code 303


   Similar to 201 but no caching is allowed.  The response MUST include
   a Location: header.


3.4.3.3  Response code 400


   Indicates that the server believes that the data sent constitutes an
   invalid request.  The server SHOULD include an entity containing an
   explanation of the error situation, and whether it is a temporary or
   permanent condition.


3.4.3.4  Response code 415


   The MIME type of the request entity is not supported by the server
   for this resource.


   The response SHOULD contain enough for information for the user to
   resolve the conflict.




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   [[@@TBD@@ more about response body format ]]


3.4.3.5  Response code 500


   Indicates that the server detected an internal error on the server
   processing this request (such as an unhandled exception).  A short
   description of the error will appear on the status line itself.  A
   longer description will appear in the body.


3.5  Link Tag


   The link tag is used in both HTML and Atom formats.  There are slight
   differences between the two usages.  Here are the commonalities,
   differences, and a list of well-known values for the rel attribute.


   <http://www.w3.org/TR/html4/struct/links.html#edef-LINK> appears in
   the 'head' of the document.  The 'head' section only allows a linear
   list of 'link' tags.  The Atom format allows 'link' tags as children
   of both the 'feed' element and of the 'entry' element.  Note that
   this gives the information present in the link tag more context.  For
   example ...  @@ TBD @@


3.5.1  rel


   This attribute describes the relationship from the current document,
   be it HTML or Atom, to the anchor specified by the href attribute.
   The value of this attribute is a space-separated list of link types.
   Note that these values are case insensitive.  When used in concert
   with type="application/atom+xml", the relations may be interpreted as
   follows.
   alternate: The URI in the href attribute points to an alternate
      representation of the containing resource.
   start: The Atom feed at the URI supplied in the href attribute
      contains the first feed in a linear sequence of entries.
   next: The Atom feed at the URI supplied in the href attribute
      contains the next N entries in a linear sequence of entries.
   prev: The Atom feed at the URI supplied in the href attribute
      contains the previous N entries in a linear sequence of entries.
   service.edit: The URI given in the href attribute is used to edit a
      representation of the referred resource.
   service.post: The URI in the href attribute is used to create new
      resources.
   service.feed: The URI given in the href attribute is a starting point
      for navigating content and services.


3.5.2  href


   URI of the resource being described by this link element.




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3.5.3  title


   Offers advisory information about the link.  Rendered to the user to
   help them choose among a set of links with the same rel and type
   attributes.


3.5.4  type


   The content type of the resource available at the URI given in the
   href attribute of the link element.  Most of the link types in this
   specification are on type 'application/atom+xml'.


3.6  Atom Request and Response Body Constraints


   The Atom format is used as the representation of all the resources in
   this specification.  As it is used in differing contexts, there are
   different constraints of which elements may be present, and how their
   values should be interpreted.


3.6.1  id


   PostURI MUST NOT be present.
   FeedURI MUST be present.
   EditURI
      GET MUST be present.
      PUT MUST be present.


3.6.2  link


   PostURI MAY be present.  Servers MAY use the information to determine
      the URI of the created resource.  Relative URLs are to be
      interpreted relative to xml:base.
   FeedURI MUST be present.
   EditURI
      GET MUST be present.
      PUT MUST be present.


3.6.3  title


   PostURI MUST be present.  The element may be empty, to explicitly
      indicate "no title".  Servers SHOULD NOT try to generate a title
      if one is not provided.  The type attribute MAY be present, and if
      not it defaults to "text/plain".  If present, it MUST represent a
      MIME type that the server supports.  The mode attribute MAY be
      present.  If not present, it defaults to "xml".  If present, it
      MUST be "xml", "base64", or "escaped".






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   FeedURI MUST be present.
   EditURI
      GET MUST be present.
      PUT MUST be present.  The element may be empty, to explicitly
         indicate "no title".  Servers SHOULD NOT try to generate a
         title if one is not provided.


3.6.4  summary


   PostURI MAY be present.  If not present, the server is welcome to
      produce its own summary.  If present but empty, the server SHOULD
      NOT generate a summary of its own.  The type attribute MAY be
      present.  If not, it defaults to "text/plain".  If present, it
      must represent a MIME type that the server supports.  The mode
      attribute MAY be present and defaults to "xml".  If present, it
      must be "xml","base64", or "escaped".
   FeedURI MAY be present.
   EditURI
      GET MAY be present.
      PUT MAY be present.  The element may be empty, to explicitly
         indicate "no summary".  Servers SHOULD NOT try to generate a
         title if one is not provided.


3.6.5  content


   PostURI MAY be present but may be empty, to explicitly indicate "no
      content".  The type attribute MAY be present, but defaults to
      "text/plain" if not present.  It must represent a MIME type that
      the server supports.  The MODE attribute may be present and
      defaults to "xml" if not present.  It must be "xml","base64", or
      "escaped".
   FeedURI MAY be present.
   EditURI
      GET MAY be present.
      PUT MAY be present.  The element may be empty, to explicitly
         indicate "no content".


3.6.6  issued


   PostURI MUST be present, but may be empty, in which case it signifies
      "now" in the time zone of the server.
   FeedURI MUST be present.
   EditURI
      GET MUST be present.
      PUT MUST be present.  Server policy determines if an updated time
         is accepted.






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3.6.7  modified


   PostURI MUST NOT be present.
   FeedURI MAY be present.
   EditURI
      GET MAY be present.
      PUT MAY be present.  The element may be empty, to explicitly
         indicate that 'now' on the server time is to be used.


3.6.8  created


   PostURI MAY be present.
   FeedURI MAY be present.
   EditURI
      GET MAY be present.
      PUT MAY be present.  The server may or may not accept an updated
         value.  If the server does not allow updating the issued time
         then any PUT request with a different issued value MUST be
         rejected.


3.6.9  author


   PostURI MAY be present.  If not present, the server determines the
      author.  If present, and conflicting with valid values as
      determined by the server, then the server may change the value of
      author.
   FeedURI MAY be present.
   EditURI
      GET MAY be present.
      PUT MAY be present.


3.6.10  contributor


   PostURI MAY be present.
   FeedURI MAY be present.
   EditURI
      GET MAY be present.
      PUT MAY be present.


3.6.11  generator


   PostURI MUST be present and contain a URI.  The value of the element
      indicates the code base used to create this request.  MUST also
      have an attribute 'version' with a version number.
   FeedURI MUST NOT be present.







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   EditURI
      GET MUST NOT be present.
      PUT MUST NOT be present.


3.7  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.


3.7.1  [@@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.


4.  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.




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   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.


5.  IANA Considerations


   This document has no actions for IANA.


6.  Appendix A - SOAP Enabling


   All servers SHOULD support the following alternate interface
   mechanisms to enable a wider variety of clients to interact with Atom
   Publishing Protocol servers.  The following requirements are in
   addition to the ones listed in the Functional Specification Section.
   If a server supports SOAP Enabling then it MUST support all of the
   following.


6.1  Servers


   1.  All servers MUST support the limited use of the SOAPAction HTTP
       Header as described below in the Client section.
   2.  All servers MUST be able to process well formed XML.  Servers
       need not be able to handle processing instructions or DTDs.
   3.  Servers MUST accept content in a SOAP Envelope, and if they
       receive a request that is wrapped in a SOAP Envelope then they
       MUST wrap their responses in SOAP envelopes or produce a SOAP
       Fault.


6.2  Clients


   1.  Clients SHOULD use the appropriate HTTP Method when possible.
       When not possible, they should use POST and include a SOAPAction
       HTTP header which is constrained as follows:
   2.  SOAPAction: "http://schemas.xmlsoap.org/wsdl/http/[METHOD]"
   3.  Where [METHOD] is replaced by the desired HTTP Method.
   4.  Clients MAY wrap their XML payload in a SOAP Envelope.  If so,
       they must also wrap it in an element which exactly matches the
       HTTP Method.


7.  Appendix B - Examples


7.1  Example for a weblog


   Fill this in with an example for how all the above is used for a




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   weblog.  Start with main HTML page, link tag of type service.feed to
   the 'introspection' file.  1.  Creating a new entry 2.  Finding an
   old entry 3.  editing an old entry 4.  commenting on a entry (via
   HTML and Atom)


7.2  Example for a wiki


   Fill this in like above but for a wiki.


8.  Revision History


   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.





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   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 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.


9  Normative References


   [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.


   [RFC2396]  Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
              Resource Identifiers (URI): Generic Syntax", RFC 2396,
              August 1998.


   [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.





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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)
   Boswijck Memex Consulting
   148 N 9th St. 4R
   Brooklyn, NY  11211
   US


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































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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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