From: http://www.ietf.org/internet-drafts/draft-sayre-atompub-protocol-basic-06.txt Title: The Atom Publishing Protocol (Basic) Reference: IETF Working Group, Internet-Draft 'draft-sayre-atompub-protocol-basic-06.txt' Date: January 24, 2006 See: "Atom Publishing Format and Protocol" http://xml.coverpages.org/atom.html ======================================================================== Atompub Working Group R. Sayre Internet-Draft January 24, 2006 Expires: July 28, 2006 The Atom Publishing Protocol (Basic) draft-sayre-atompub-protocol-basic-06 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 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 July 28, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This memo presents a protocol that uses XML and HTTP to publish and edit Web resources. Sayre Expires July 28, 2006 [Page 1] Internet-Draft APP Basic January 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3 3. The Atom Publishing Protocol Model . . . . . . . . . . . . . . 3 4. Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5. Listing . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6. Authoring . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7. Atom Protocol Feeds . . . . . . . . . . . . . . . . . . . . . 6 8. Media Feeds . . . . . . . . . . . . . . . . . . . . . . . . . 8 9. Service Description . . . . . . . . . . . . . . . . . . . . . 10 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 11. Security Considerations . . . . . . . . . . . . . . . . . . . 14 12. Informative References . . . . . . . . . . . . . . . . . . . . 15 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 15 Appendix B. Change History . . . . . . . . . . . . . . . . . . . 15 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16 Intellectual Property and Copyright Statements . . . . . . . . . . 17 Sayre Expires July 28, 2006 [Page 2] Internet-Draft APP Basic January 2006 1. Introduction The Atom Publishing Protocol uses HTTP [RFC2616] and XML [W3C.REC- xml-20040204] to publish and edit Web resources. 2. Notational Conventions The Atom Protocol namespace is "http://purl.org/atom/app#". This specification refers to it by using the prefix "pub", but that prefix is arbitrary. The terms 'URI' and 'IRI' are shorthand for the identifiers specified in [RFC3986] and [RFC3987]. 3. The Atom Publishing Protocol Model The Atom Protocol uses HTTP to operate on collections of Web resources represented by Atom feeds [AtomFormat]. This section illustrates the editing cycle for Atom entries. 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. Discovery To discover the location of the feeds exposed by an Atom Protocol service, the client must locate and request a Service Description Document (Section 6). Client Server | | | 1.) GET Service URI | |------------------------------->| | | | 2.) Service Description Doc | |<-------------------------------| | | 1. The client sends a GET request to the Service Description URI. Sayre Expires July 28, 2006 [Page 3] Internet-Draft APP Basic January 2006 2. The server responds with a Service Description Document containing the locations of feeds 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. 5. Listing Once the client has discovered the location of a feed in the outline, it can request a listing of the feed's entries. However, a feed might contain an extremely large number of entries, so servers are likely to list a small subset of them by default. Client Server | | | 1.) GET to Atom Feed URI | |------------------------------->| | | | 2.) 200 OK, Atom Feed Doc | |<-------------------------------| | | 1. The client sends a GET request to the Atom Feed's URI. 2. The server responds with an Atom Feed Document containing a full or partial listing of the feed's membership. 6. Authoring After locating a feed, a client can add entries by sending a POST request to the feed; other changes are accomplished by sending HTTP requests to each entry. 6.1. Create Client Server | | | 1.) POST Entry to Feed URI | |------------------------------->| | | | 2.) 201 Created @ Location | |<-------------------------------| | | Sayre Expires July 28, 2006 [Page 4] Internet-Draft APP Basic January 2006 1. The client sends an Atom Entry to the server via HTTP POST. The Request URI is that of the Atom Feed. 2. The server responds with a response of "201 Created" and a "Location" header containing the URI of the newly-created Atom Entry. 6.2. Read Client Server | | | 1.) GET or HEAD to Entry URI | |------------------------------->| | | | 2.) 200 OK Atom Entry | |<-------------------------------| | | 1. The client sends a GET (or HEAD) request to the entry's URI. 2. The server responds with an Atom Entry document. 6.3. Update Client Server | | | 1.) PUT to Entry URI | |------------------------------->| | | | 2.) 200 OK | |<-------------------------------| | | 1. The client PUTs an updated Atom Entry Document to the entry's URI. 2. The server responds with a successful status code. 6.4. Delete Client Server | | | 1.) DELETE to Entry URI | |------------------------------->| | | | 2.) 204 No Content | Sayre Expires July 28, 2006 [Page 5] Internet-Draft APP Basic January 2006 |<-------------------------------| | | 1. The client sends a DELETE request to the entry's URI. 2. The server responds with successful status code. 6.5. 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. 7. Atom Protocol Feeds 7.1. GET Feeds 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 contained every entry in the feed, 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 entries in the feed. Sayre Expires July 28, 2006 [Page 6] Internet-Draft APP Basic January 2006 An example Atom Protocol feed: My Posts1 urn:uuid:ce61592c-14e2-4557-978e-dfbd444aefa6 2005-12-21T04:11:00-08:00 title 25 2005-12-21T04:11:00-08:00 Foo It started out looking simple enough... urn:uuid:941e12b4-6eeb-4753-959d-0cbc51875387 ... Each member entry is represented by an atom:entry element, but those entries are not an editable representation of the entry. To retrieve the source representation of the entry, clients send a GET request to the URI found in each entry's pub:edit element (see Section 4.3.1). Derived resources are located by examining an entry's atom:link elements. 7.2. POST An Atom Protocol feed also accepts POST requests. The client POSTs a representation of the desired resource to the APP feed. Some feeds only accept POST requests with certain media-types, so a POST request could result in a response with a status code of 415 ("Unsupported Media Type"). In the case of a successful creation, the status code is 201 ("Created"). Sayre Expires July 28, 2006 [Page 7] Internet-Draft APP Basic January 2006 Example request creating a new entry in a feed: POST /collection HTTP/1.1 Host: example.org User-Agent: Cosimo/1.0 Content-Type: application/atom+xml Content-Length: nnnn ...data... Example response. HTTP/1.1 201 Created Date: Mon, 21 Mar 2005 19:20:19 GMT Server: CountBasic/2.0 ETag: "4c083-268-423f1dc6" Location: http://example.org/stuff/foo13241234.atom 8. Media Feeds The entries within Media Feeds do not represent uniform types of content. For example, they might contain JPEG images, text documents, MPEG movies, or any other type of resource the server allows. 8.1. GET Media Feeds return an Atom feed much like the textual Atom Protcol feeds described above, but with a few additions. The entries also contain an atom:content element with a 'src' attribute pointing to the media resource. This URI can be used to edit the uploaded media resource, using PUT and DELETE. Such entries may contain edit links used to edit the entry metadata. As with any Atom entry, related and derived resources can be located by inspecting an entry's atom:link elements. Sayre Expires July 28, 2006 [Page 8] Internet-Draft APP Basic January 2006 An example Media Feed: My Posts1 Foo urn:uuid:ce61592c-14e2-4557-978e-dfbd444aefa6 2005-12-21T04:11:00-08:00 Title25 2005-12-21T04:11:00-08:00 urn:uuid:941e12b4-6eeb-4753-959d-0cbc51875387 This was awesome. ... The Atom Syndication Format requires that each such entry contain an atom:title and atom:summary element. This requirement can be challenging to meet without requiring users to enter tedious metadata, but servers should attempt to provide textual data about the resource in the interests of accessibility. The atom:title element will likely be provided by the client, as a way for users to associate their local resources with those they have uploaded to the server (see POST below). 8.2. POST To add an entry to a Media Feed, clients POST the resource to the Media Feed's URI. Clients should provide a 'Title' request header to provide the server with a short string identifying the resource to users. Clients may include a 'Content-Description' header [RFC2045] providing a more complete description of the content. In addition, servers may inspect the POSTed entity for additional metadata to be exposed in an atom:entry element when listed in a Media Feed. For example, the server might inspect a JPEG file for EXIF headers containing creator data. Sayre Expires July 28, 2006 [Page 9] Internet-Draft APP Basic January 2006 An example request: POST /collection HTTP/1.1 Host: example.org User-Agent: Cosimo/1.0 Content-Type: image/tiff Content-Length: nnnn Title: A Trip to the beach Content-Description: It was so fun. ...binary data... An example response: HTTP/1.1 201 Created Date: Mon, 21 Mar 2005 19:20:19 GMT Server: CountBasic/2.0 ETag: "4c083-268-423f1dc6" Location: http://example.org/stuff/beach.tiff [@@ deal with response ambiguity noted in WG] 9. Service Description Many Atom Protocol applications require a basic resource layout in order to ease configuration requirements. Servers use Service Description documents to convey information about related groups of Atom Protocol feeds. On a blogging service, for example, each group might represent a distinct blog and associated resources. Example Service Description document: Sayre Expires July 28, 2006 [Page 10] Internet-Draft APP Basic January 2006 Servers are not required to expose a Service Description document, but experimental deployment experience has shown that a single document which signals some basic information about the server's configuration can greatly simplify client implementations. The simplest useful Service Description document shows the location of a single resource: If another service is added, the document can be upgraded to reflect new resources. Finally, more extensive services could require some amount of hierarchical grouping. Sayre Expires July 28, 2006 [Page 11] Internet-Draft APP Basic January 2006 This example shows that links to APP feeds can appear in elements used to group other resources. The element named "Other Things" does not contain an 'href' attribute, so it functions as a simple named group of the services it contains. 9.1. Categories [@@ tbd] 9.2. Document Format Service Description documents MUST be well-formed XML [W3C.REC-xml- 20040204]. The root element of an APP Service Description Document is "". This specification does not define any attributes of the element, but the element can have any number of attributes. Zero or more elements appear as child elements of . Also, elements may contain zero or more elements. This specification defines three attributes of the element. elements contain at least a 'name' or 'href' attribute. Additional service properties too large or structured to include in attribute values could appear as child elements of the service element. elements can contain any number of elements that are not elements, and elements can contain any number of elements that are not elements. 9.2.1. The 'name' Attribute The 'name' attribute contains a short string describing the service element. Entities such as "&" and "<" represent their corresponding characters ("&" and "<" respectively), not markup. 9.2.2. The 'href' Attribute The 'href' attribute contains an IRI reference interpreted relative to the in-scope base IRI [RFC3987]. Most protocols require URIs [RFC3986], so IRIs usually need to be converted to URIs before being dereferenced. 9.2.3. The 'class' Attribute The 'class' attribute contains a space-separated list of strings used to classify the service element. This specification defines two values for the 'class' attribute: Sayre Expires July 28, 2006 [Page 12] Internet-Draft APP Basic January 2006 o feed o media feed These values correspond to standard feeds and media feeds, respectively. If the 'class' attribute is not present, the element can be processed as if the attribute were present with a value of 'feed'. 9.2.4. Relax NG Schema Service Description documents conform to the schema below. default namespace = "http://purl.org/atom/app#" start = app app = element app { anyAttribute*, (service* & anyElement*) } service = element service { (nameAtt | hrefAtt), anyAttribute*, (service* & anyElement*) } nameAtt = attribute name { text } hrefAtt = attribute href { text } classAtt = attribute class { text } anyElement = element * { (anyAttribute | text | anyElement)* } anyAttribute = attribute * { text } 9.2.5. Extending Service Description The Service Description document format can be freely extended by adding attributes and elements not defined by this specification. Valid Service Description document with extensions: 42 hmm Sayre Expires July 28, 2006 [Page 13] Internet-Draft APP Basic January 2006 Additional service properties too large or structured to include in attribute values could appear as child elements of the or elements. elements may contain any number of elements that are not elements, and elements may contain any number of elements that are not elements. 9.2.6. User Agent Conformance Foreign markup is markup not defined by this specification. Software consuming Service Description documents must not halt processing when any foreign markup is encountered. Software may ignore the markup and process any content of foreign elements as though the surrounding markup were not present. For example, software may process ... as though the and elements were not present. Software conforming to this specification may halt processing when documents that do not conform to the schema are encountered. 10. IANA Considerations [@@ fill out in for application/sd+xml (service description)] 11. Security Considerations Sayre Expires July 28, 2006 [Page 14] Internet-Draft APP Basic January 2006 12. Informative References Appendix A. Acknowledgements This draft is a variant of the in-progress Atom Publishing Protocol specification from the IETF Atompub WG, and owes a debt to the WG's members. Appendix B. Change History -06: Change service description format. Change IPR terms to full3978 -interlude: More unproductive WG thrashing. -05: Death to collections! Switch APPO instead of XOXO. State the obvious about the extension elements. Remove RFC2119 reference. Change "Normative References" to "References". -04: Add pub:control element. Reword collection POST. Prophesize about atom:id. -03: Remove search/query capabilities added in -02 Drop round- tripping. Most of them were writable, some folks wanted to edit atom:updated, that leaves atom:id, and that seems foolish to try and edit, so go ahead and try it if you think you can. -02: Add search/query capabilities. -01: Split from WG draft, cut SOAP, and much other cruft. -interlude: Becomes WG draft. -00: Split from WG draft. Sayre Expires July 28, 2006 [Page 15] Internet-Draft APP Basic January 2006 Author's Address Robert Sayre Email: rfsayre@boswijck.com Sayre Expires July 28, 2006 [Page 16] Internet-Draft APP Basic January 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Sayre Expires July 28, 2006 [Page 17]