Network Working Group J. Gregorio, Ed. Internet-Draft IBM Intended status: Standards Track B. de hOra, Ed. Expires: August 9, 2007 Propylon Ltd. February 5, 2007 The Atom Publishing Protocol draft-ietf-atompub-protocol-13.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 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 August 9, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Gregorio & de hOra Expires August 9, 2007 [Page 1] Internet-Draft The Atom Publishing Protocol February 2007 Abstract The Atom Publishing Protocol (APP) is an application-level protocol for publishing and editing Web resources. The protocol is based on HTTP transport of Atom-formatted representations. The Atom format is documented in the Atom Syndication Format [RFC4287]. Gregorio & de hOra Expires August 9, 2007 [Page 2] Internet-Draft The Atom Publishing Protocol February 2007 Editorial Note To provide feedback on this Internet-Draft, join the atom-protocol mailing list (http://www.imc.org/atom-protocol/index.html) [1]. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 6 2.1. XML-related Conventions . . . . . . . . . . . . . . . . . 6 2.1.1. Referring to Information Items . . . . . . . . . . . . 6 2.1.2. RELAX NG Schema . . . . . . . . . . . . . . . . . . . 6 2.1.3. Use of xml:base and xml:lang . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Client Implementation Considerations . . . . . . . . . . . 9 5. Protocol Operations . . . . . . . . . . . . . . . . . . . . . 11 5.1. Retrieving a Service Document . . . . . . . . . . . . . . 11 5.2. Listing Collection Members . . . . . . . . . . . . . . . . 11 5.3. Creating a Resource . . . . . . . . . . . . . . . . . . . 12 5.4. Editing a Resource . . . . . . . . . . . . . . . . . . . . 12 5.4.1. Retrieving a Resource . . . . . . . . . . . . . . . . 12 5.4.2. Updating a Resource . . . . . . . . . . . . . . . . . 13 5.4.3. Deleting a Resource . . . . . . . . . . . . . . . . . 13 5.5. Use of HTTP Response codes . . . . . . . . . . . . . . . . 13 6. Atom Publishing Protocol Documents . . . . . . . . . . . . . . 14 6.1. Document Types . . . . . . . . . . . . . . . . . . . . . . 14 6.2. Document Extensibility . . . . . . . . . . . . . . . . . . 14 7. Category Documents . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 16 7.2. Element Definitions . . . . . . . . . . . . . . . . . . . 16 7.2.1. The "app:categories" element . . . . . . . . . . . . . 16 8. Service Documents . . . . . . . . . . . . . . . . . . . . . . 18 8.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 19 8.2. Element Definitions . . . . . . . . . . . . . . . . . . . 20 8.2.1. The "app:service" Element . . . . . . . . . . . . . . 20 8.2.2. The "app:workspace" Element . . . . . . . . . . . . . 20 8.2.3. The "app:collection" Element . . . . . . . . . . . . . 21 8.2.4. The "app:accept" Element . . . . . . . . . . . . . . . 21 8.2.5. The "app:categories" Element . . . . . . . . . . . . . 22 9. Creating and Editing Resources . . . . . . . . . . . . . . . . 24 9.1. Member URIs . . . . . . . . . . . . . . . . . . . . . . . 24 9.2. Creating resources with POST . . . . . . . . . . . . . . . 24 9.2.1. Example . . . . . . . . . . . . . . . . . . . . . . . 25 9.3. Updating Resources with PUT . . . . . . . . . . . . . . . 26 9.4. Deleting Resources with DELETE . . . . . . . . . . . . . . 26 9.5. Media Resources and Media Link Entries . . . . . . . . . . 26 Gregorio & de hOra Expires August 9, 2007 [Page 3] Internet-Draft The Atom Publishing Protocol February 2007 9.5.1. Examples . . . . . . . . . . . . . . . . . . . . . . . 27 9.6. The Slug: Header . . . . . . . . . . . . . . . . . . . . . 32 9.6.1. Slug: Header syntax . . . . . . . . . . . . . . . . . 33 9.6.2. Example . . . . . . . . . . . . . . . . . . . . . . . 33 10. Listing Collections . . . . . . . . . . . . . . . . . . . . . 34 10.1. Collection Paging . . . . . . . . . . . . . . . . . . . . 34 10.2. The "app:edited" Element . . . . . . . . . . . . . . . . . 35 11. Atom Format Link Relation Extensions . . . . . . . . . . . . . 36 11.1. The "edit" Link Relation . . . . . . . . . . . . . . . . . 36 11.2. The "edit-media" Link Relation . . . . . . . . . . . . . . 36 12. The Atom Format Type Parameter . . . . . . . . . . . . . . . . 37 12.1. The 'type' parameter . . . . . . . . . . . . . . . . . . . 37 12.1.1. Conformance . . . . . . . . . . . . . . . . . . . . . 37 13. Atom Publishing Controls . . . . . . . . . . . . . . . . . . . 38 13.1. The "app:control" Element . . . . . . . . . . . . . . . . 38 13.1.1. The "app:draft" Element . . . . . . . . . . . . . . . 38 14. Securing the Atom Publishing Protocol . . . . . . . . . . . . 39 15. Security Considerations . . . . . . . . . . . . . . . . . . . 40 15.1. Denial of Service . . . . . . . . . . . . . . . . . . . . 40 15.2. Replay Attacks . . . . . . . . . . . . . . . . . . . . . . 40 15.3. Spoofing Attacks . . . . . . . . . . . . . . . . . . . . . 40 15.4. Linked Resources . . . . . . . . . . . . . . . . . . . . . 40 15.5. Digital Signatures and Encryption . . . . . . . . . . . . 40 15.6. URIs and IRIs . . . . . . . . . . . . . . . . . . . . . . 40 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41 16.1. Content-type registration for 'application/atomserv+xml' . . . . . . . . . . . . . . . . 41 16.2. Content-type registration for 'application/atomcat+xml' . 42 16.3. Header field registration for 'SLUG' . . . . . . . . . . . 43 16.4. The Link Relation registration "edit" . . . . . . . . . . 44 16.5. The Link Relation registration "edit-media" . . . . . . . 44 16.6. The Atom Format Media Type Parameter . . . . . . . . . . . 44 17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 45 17.1. Normative References . . . . . . . . . . . . . . . . . . . 45 17.2. Informative References . . . . . . . . . . . . . . . . . . 46 Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 48 Appendix B. RELAX NG Compact Schema . . . . . . . . . . . . . . . 49 Appendix C. Revision History . . . . . . . . . . . . . . . . . . 55 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 58 Intellectual Property and Copyright Statements . . . . . . . . . . 59 Gregorio & de hOra Expires August 9, 2007 [Page 4] Internet-Draft The Atom Publishing Protocol February 2007 1. Introduction The Atom Publishing Protocol is an application-level protocol for publishing and editing Web resources using HTTP [RFC2616] and XML 1.0 [W3C.REC-xml]. The protocol supports the creation of Web resources and provides facilities for: o Collections: Sets of resources, which can be retrieved in whole or in part. o Service: Discovering and describing Collections. o Editing: Creating, updating and deleting resources. The Atom Publishing Protocol is different from many contemporary protocols in that the server is given wide latitude in processing requests from clients. See Section 4 for more details. Gregorio & de hOra Expires August 9, 2007 [Page 5] Internet-Draft The Atom Publishing Protocol February 2007 2. Notational Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2.1. XML-related Conventions 2.1.1. Referring to Information Items Atom Protocol Document formats are specified in terms of the XML Information Set [W3C.REC-xml-infoset], serialized as XML 1.0 [W3C.REC-xml]. The Infoset terms "Element Information Item" and "Attribute Information Item" are shortened to "element" and "attribute" respectively. Therefore, when this specification uses the term "element", it is referring to an Element Information Item, and when it uses the term "attribute", it is referring to an Attribute Information Item. 2.1.2. RELAX NG Schema Some sections of this specification are illustrated with fragments of a non-normative RELAX NG Compact schema [RNC]. However, the text of this specification provides the definition of conformance. Complete schemas appear in Appendix B. 2.1.3. Use of xml:base and xml:lang XML elements defined by this specification MAY have an xml:base attribute [W3C.REC-xmlbase-20010627]. When xml:base is used, it serves the function described in Section 5.1.1 of URI Generic Syntax [RFC3986], by establishing the base URI (or IRI) for resolving relative references found within the scope of the xml:base attribute. Any element defined by this specification MAY have an xml:lang attribute, whose content indicates the natural language for the element and its descendents. The language context is only significant for elements and attributes declared to be "Language- Sensitive" by this specification. Requirements regarding the content and interpretation of xml:lang are specified in Section 2.12 of XML 1.0 [W3C.REC-xml]. Gregorio & de hOra Expires August 9, 2007 [Page 6] Internet-Draft The Atom Publishing Protocol February 2007 3. Terminology For convenience, this protocol can be referred to as the "Atom Protocol" or "APP". URI/IRI - A Uniform Resource Identifier and Internationalized Resource Identifier. These terms and the distinction between them are defined in [RFC3986] and [RFC3987]. Before an IRI found in a document is used by HTTP, the IRI is first converted to a URI (see Section 4). The phrase "the URI of a document" in this specification is shorthand for "a URI which, when dereferenced, is expected to produce that document as a representation". Resource - A network-accessible data object or service identified by an IRI, as defined in [RFC2616]. See [W3C.REC-webarch-20041215] for further discussion on resources. Representation - An entity included with a request or response as defined in [RFC2616]. Collection - A resource that contains a set of Member Entries. See Section 9. Member - A resource whose IRI is listed in a Collection by a link element with a relation of "edit" or "edit-media". See Section 9.1. Workspace - A named group of Collections. See Section 8. Service Document - A document that describes the location and capabilities of one or more Collections. See Section 8. Category Document - A document that describes the categories allowed in a Collection. See Section 7. Gregorio & de hOra Expires August 9, 2007 [Page 7] Internet-Draft The Atom Publishing Protocol February 2007 4. Protocol Model The Atom Publishing Protocol uses HTTP methods to author Member Resources as follows: o GET is used to retrieve a representation of a known resource. o POST is used to create a new, dynamically-named, resource. When the client submits non-Atom-Entry representations to a Collection for creation, two resources are always created - a Media Entry for the requested resource, and a Media Link Entry for metadata (in Atom Entry format) about the resource. o PUT is used to update a known resource. o DELETE is used to remove a known resource. This document does not specify the form of the URIs that are used. HTTP ([RFC2616]) specifies that the URI space of each server is controlled by that server and the Atom Protocol imposes no constraints on that control. What this RFC does specify are the formats of the representations that are exchanged and the actions that can be performed on the IRIs embedded in those documents. This document only covers the creation, update and deletion of Entry and Media resources. Other resources can be created, updated, and deleted as the result of manipulating a Collection, but the number of those resources, their media-types, and effects of Atom Protocol operations on them are outside the scope of this specification. Since all aspects of client-server interaction are defined in terms of HTTP, [RFC2616] should be consulted for any areas not covered in this specification. Along with operations on Member Resources, the Atom Protocol defines Collection Resources for managing and organizing Member Resources. Collections are represented by Atom Feed documents and contain the IRIs of, and metadata about, their Member Resources. The Atom Protocol does not make a structural distinction between Feeds used for Collections and other Atom Feeds. The only mechanism that this specification supplies for distinguishing a Collection Feed is its appearance in a Service Document. Atom Protocol documents allow the use of IRIs [RFC3987], as well as URIs [RFC3986]. Before an IRI found in a document is used by HTTP, the IRI is first converted to a URI according the procedure defined in Section 3.1 of [RFC3987]. In accordance with that specification, this conversion SHOULD be applied as late as possible. The IRI, and Gregorio & de hOra Expires August 9, 2007 [Page 8] Internet-Draft The Atom Publishing Protocol February 2007 the URI into which it is converted, identify the same resource. There are two kinds of Member Resources - Member Entry Resources and Media Resources. Member Entry Resources are represented as Atom Entries [RFC4287]. Media Resources can have representations in any media type. A Media Link Entry is a Member Entry that contains metadata about a Media Resource. This diagram shows the classification of the resources: Member Resource -> Member Entry Resource -> Media Link Entry Resource -> Media Resource A Collection's Atom Entries contain the Member Entry and Media Resources IRIs of the Collection. A Collection can contain any number of Entries for either kind. In the diagram of a Collection below, there are two Entries. The first contains the IRI of a Member Entry Resource. The second contains the IRIs of both a Media Resource and a Media Link Entry Resource, which contains the metadata for that Media Resource: Collection Entry Member Entry IRI -> Member Entry Resource Entry Member Entry IRI -> Media Link Entry Resource Media IRI -> Media Resource Service Documents represent server-defined groups of Collections, and are used to initialize the process of creating and editing resources. 4.1. Client Implementation Considerations The Atom Protocol imposes few restrictions on the actions of servers. Unless a constraint is specified here, servers can be expected to vary in behavior, in particular around the manipulation of Atom Entries sent by clients. For example, although this specification only defines the expected behavior of Collections with respect to GET and POST, this does not imply that PUT, DELETE, PROPPATCH and others are forbidden on Collection resources - only that this specification does not define what the servers response would be to those methods. Similarly while some HTTP status codes are mentioned explicitly, clients should be prepared to handle any status code from a server. Servers can choose to accept, reject, delay, moderate, censor, reformat, translate, relocate or recategorize the content submitted Gregorio & de hOra Expires August 9, 2007 [Page 9] Internet-Draft The Atom Publishing Protocol February 2007 to them. Only some of these choices are immediately relayed back to the client in responses to client requests; other choices may only become apparent later, in the feed or published entries. The same series of requests to two different publishing sites can result in a different series of HTTP responses, different resulting feeds or different entry contents. As a result, client software has to be written flexibly to accept what the server decides are the results of its submissions. Any server response or server content modification not explicitly forbidden by this specification or HTTP ([RFC2616]) is therefore allowed. Gregorio & de hOra Expires August 9, 2007 [Page 10] Internet-Draft The Atom Publishing Protocol February 2007 5. Protocol Operations 5.1. Retrieving a Service Document Client Server | | | 1.) GET to Service Document | |------------------------------------------>| | | | 2.) Service Document | |<------------------------------------------| | | 1. The client sends a GET request using the URI of the Service Document. 2. The server responds with the document enumerating the IRIs of a group of Collections and the capabilities of those Collections supported by the server. The content of this document can vary based on aspects of the client request, including, but not limited to, authentication credentials. 5.2. Listing Collection Members To list the members of a Collection, the client sends a GET request to the URI of a Collection. An Atom Feed Document is returned whose Entries contain the IRIs of Member Resources. The returned Feed may describe all, or only a subset, of the Members in a Collection (see Section 10). Section 11 describes extensions to the Atom Syndication Format used in the Atom Protocol. Client Server | | | 1.) GET to Collection URI | |------------------------------->| | | | 2.) Atom Feed Doc | |<-------------------------------| | | 1. The client sends a GET request to the URI of the Collection. 2. The server responds with an Atom Feed Document containing the IRIs of the Collection members. Gregorio & de hOra Expires August 9, 2007 [Page 11] Internet-Draft The Atom Publishing Protocol February 2007 5.3. Creating a Resource Client Server | | | 1.) POST to URI of Collection | |------------------------------------------>| | | | 2.) 201 Created | | Location: Member Entry URI | |<------------------------------------------| | | 1. The client POSTs a representation of the Member to the URI of the Collection. 2. If the Member Resource was created successfully, the server responds with a status code of 201 and a Location: header that contains the IRI of the newly created Member Entry Resource. Media Resources could have also been created and their IRIs can be found through the Member Entry Resource. See Section 9.5 for more details. 5.4. Editing a Resource Once a resource has been created and its Member URI is known, that URI can be used to retrieve, update, and delete the resource. 5.4.1. Retrieving a Resource Client Server | | | 1.) GET to Member URI | |------------------------------------------>| | | | 2.) Member Representation | |<------------------------------------------| | | 1. The client sends a GET request to the URI of a Member Resource to retrieve its representation. 2. The server responds with the representation of the resource. Gregorio & de hOra Expires August 9, 2007 [Page 12] Internet-Draft The Atom Publishing Protocol February 2007 5.4.2. Updating a Resource Client Server | | | 1.) PUT to Member URI | |------------------------------------------>| | | | 2.) 200 OK | |<------------------------------------------| 1. The client PUTs an updated representation to the URI of a Member Resource. 2. If the update is successful the server responds with a status code of 200. 5.4.3. Deleting a Resource Client Server | | | 1.) DELETE to Member URI | |------------------------------------------>| | | | 2.) 200 Ok | |<------------------------------------------| | | 1. The client sends a DELETE request to the URI of a Member Resource. 2. If the deletion is successful the server responds with a status code of 200. A different approach is taken for deleting Media Resources, see Section 9.5 for details. 5.5. Use of HTTP Response codes The Atom Protocol uses the response status codes defined in HTTP to indicate the success or failure of an operation. Consult the HTTP specification [RFC2616] for detailed definitions of each status code. Implementers are asked to note that according to the HTTP specification, HTTP 4xx and 5xx response entities SHOULD include a human-readable explanation of the error. Gregorio & de hOra Expires August 9, 2007 [Page 13] Internet-Draft The Atom Publishing Protocol February 2007 6. Atom Publishing Protocol Documents 6.1. Document Types This specification describes two kinds of Documents - Category Documents and Service Documents. A Category Document (Section 7) contains lists of categories specified using the "atom:category" element from the Atom Syndication Format. A Service Document (Section 8) describes Workspaces, which are server-defined groups of Collections. This specification assigns no meaning to Workspaces; that is, a Workspace does not imply any specific processing assumptions. Operations on Workspaces themselves, such as creation or deletion, are not defined by this specification. The namespace name [W3C.REC-xml-names] for either kind of document is: http://purl.org/atom/app# [[anchor8: The namespace name needs to be updated with the final URI upon publication]] This specification uses the prefix "app:" for the namespace name. The prefix "atom:" is used for "http://www.w3.org/2005/Atom", the namespace name of the Atom Syndication Format [RFC4287]. The namespace prefixes are not semantically significant. Atom Publishing Protocol Documents MUST be well-formed XML. This specification does not define any DTDs for Atom Protocol formats, and hence does not require them to be "valid" in the sense used by XML. 6.2. Document Extensibility Unrecognized markup in an Atom Publishing Protocol document is considered "foreign markup" as defined in [RFC4287]. Such foreign markup can be used anywhere within a Category or Service Document unless it is explicitly forbidden. Processors that encounter foreign markup MUST NOT stop processing and MUST NOT signal an error. Clients SHOULD preserve foreign markup when transmitting such documents. The namespace name "http://purl.org/atom/app#" is reserved for forward compatible revisions of the Category and Service Document types - this does not exclude the addition of elements and attributes that might not be recognized by processors conformant to this specification. Such unrecognized markup from the "http://purl.org/atom/app#" namespace MUST be treated as foreign Gregorio & de hOra Expires August 9, 2007 [Page 14] Internet-Draft The Atom Publishing Protocol February 2007 markup. [[anchor9: The namespace name needs to be updated with the final URI upon publication]] Gregorio & de hOra Expires August 9, 2007 [Page 15] Internet-Draft The Atom Publishing Protocol February 2007 7. Category Documents Category Documents contain lists of categories described using the "atom:category" element from the Atom Syndication Format [RFC4287]. Categories can also appear in Service Documents, where they describe the categories allowed in a Collection (see Section 8.2.5). Category Documents are identified with the "application/atomcat+xml" media type (see Section 16). 7.1. Example This Category Document contains three categories, with the terms "animal", "vegetable", and "mineral". None of the categories use the 'label' attribute defined in [RFC4287]. They all inherit the "http://example.com/cats/big3" 'scheme' attribute declared on the app:categories element. Therefore if the "mineral" category were to appear in an Atom Entry or Feed Document, it would appear as: 7.2. Element Definitions 7.2.1. The "app:categories" element The root of a Category Document is the "app:categories" element. An app:categories element can contain zero or more "atom:category" elements from the Atom namespace ("http://www.w3.org/2005/Atom"). An app:category child element that has no "scheme" attribute inherits the attribute from its app:categories parent. An app:category child element with an existing "scheme" attribute does not inherit the "scheme" value of its "app:categories" parent element. 7.2.1.1. Attributes of "app:categories" The app:categories element can contain a "fixed" attribute, with a value of either "yes" or "no", indicating whether the list of Gregorio & de hOra Expires August 9, 2007 [Page 16] Internet-Draft The Atom Publishing Protocol February 2007 categories is a fixed or an open set. Attempts to create or update members whose categories are not listed in the Collection Document MAY be rejected by the server. Collections that indicate the category set is open SHOULD NOT reject otherwise acceptable members whose categories are not listed by the Collection. Alternatively, the app:categories element MAY contain an "href" attribute, whose value MUST be an IRI reference identifying a Category Document. If the "href" attribute is provided, the app: categories element MUST be empty and MUST NOT have the "fixed" or "scheme" attributes. atomCategory = element atom:category { atomCommonAttributes, attribute term { text }, attribute scheme { atomURI }?, attribute label { text }?, undefinedContent } appInlineCategories = element app:categories { attribute fixed { "yes" | "no" }?, attribute scheme { atomURI }?, (atomCategory*) } appOutOfLineCategories = element app:categories { attribute href { atomURI }, undefinedContent } appCategories = appInlineCategories | appOutOfLineCategories Gregorio & de hOra Expires August 9, 2007 [Page 17] Internet-Draft The Atom Publishing Protocol February 2007 8. Service Documents For authoring to commence, a client needs to discover the capabilities and locations of the available Collections. Service Documents are designed to support this discovery process. How Service Documents are discovered is not defined in this specification. A Service Document describes Workspaces, which are server-defined groups of Collections. Service Documents are identified with the "application/atomserv+xml" media type (see Section 16). There is no requirement that a server support multiple Workspaces. In addition, a Collection MAY appear in more than one Workspace. Gregorio & de hOra Expires August 9, 2007 [Page 18] Internet-Draft The Atom Publishing Protocol February 2007 8.1. Example Main Site My Blog Entries Pictures image/* Side Bar Blog Remaindered Links entry This Service Document describes two Workspaces. The first Workspace is called "Main Site", has two Collections called "My Blog Entries" and "Pictures" whose IRIs are "http://example.org/reilly/main" and "http://example.org/reilly/pic" respectively. The "Pictures" Workspace includes an "accept" element indicating that a client can post image files to the Collection to create new Media Resources. Entries with associated Media Resources are discussed in Section 9.5. The second Workspace is called "Side Bar Blog" and has a single Collection called "Remaindered Links" whose IRI is "http://example.org/reilly/list". Gregorio & de hOra Expires August 9, 2007 [Page 19] Internet-Draft The Atom Publishing Protocol February 2007 Within each of the two Entry collections, the categories element provides a list of available categories for Member Entries. In the "My Blog Entries" Collection, the list of available categories is obtainable through the "href" attribute. The "Side Bar Blog" Collection provides a category list within the Service Document, but states the list is fixed, signaling a request from the server that Entries be POSTed using only those two categories. 8.2. Element Definitions 8.2.1. The "app:service" Element The root of a Service Document is the "app:service" element. The "app:service" element is the container for service information associated with one or more Workspaces. An app:service element MUST contain one or more app:workspace elements. namespace app = "http://purl.org/atom/app#" start = appService appService = element app:service { appCommonAttributes, ( appWorkspace+ & extensionElement* ) } 8.2.2. The "app:workspace" Element The "app:workspace" element contains information elements about the Collections of resources available for editing. The app:workspace element contains zero or more app:collection elements. appWorkspace = element app:workspace { appCommonAttributes, ( atomTitle & appCollection* & extensionSansTitleElement* ) } atomTitle = element atom:title { atomTextConstruct } Gregorio & de hOra Expires August 9, 2007 [Page 20] Internet-Draft The Atom Publishing Protocol February 2007 8.2.2.1. The "atom:title" Element The app:workspace element MUST contain one "atom:title" element (as defined in [RFC4287]), giving a human-readable title for the Workspace. 8.2.3. The "app:collection" Element The "app:collection" element describes a Collection. The app: collection element MAY contain one app:accept element and MAY contain any number of app:categories elements. The app:collection element MUST NOT contain more than one app:accept element. appCollection = element app:collection { appCommonAttributes, attribute href { atomURI }, ( atomTitle & appAccept? & appCategories* & extensionSansTitleElement* ) } 8.2.3.1. Usage in Atom Feed Documents The app:collection element MAY appear as a child of an atom:feed or atom:source element in an Atom Feed Document. Its value identifies a Collection by which new Entries can be added to appear in the feed. The app:collection element is considered foreign markup as defined in Section 6 of [RFC4287]. 8.2.3.2. The "href" Attribute The app:collection element MUST contain an "href" attribute, whose value gives the IRI of the Collection. 8.2.3.3. The "atom:title" Element The app:collection Element MUST contain one "atom:title" element (as defined in [RFC4287]), giving a human-readable title for the Collection. 8.2.4. The "app:accept" Element The "app:accept" element value specifies a comma-separated list of media-ranges (see [RFC2616]) identifying the types of representations that can be POSTed to the URI of a Collection. Whitespace around and Gregorio & de hOra Expires August 9, 2007 [Page 21] Internet-Draft The Atom Publishing Protocol February 2007 between media-range values is considered insignificant and MUST be ignored. The app:accept element is similar to the HTTP Accept request-header [RFC2616] with the exception that app:accept has no notion of preference. As a result, the value syntax of app:accept does not use "accept-params" or "q" arguments as specified in [RFC2616], section 14.1. The order of media-ranges is not significant. The following lists are all equivalent: image/png,image/* image/*, image/png image/* A value of "entry" may appear in any list of media-ranges in an accept element and indicates that Atom Entry Documents can be POSTed to the Collection. If the accept element exists but is empty, clients SHOULD assume that the Collection does not support the creation of new Entries. If the accept element is not present, clients SHOULD treat this as equivalent to entry. appAccept = element app:accept { appCommonAttributes, ( appTypeValue? ) } appTypeValue = ( "entry" | media-type |entry-or-media-type ) media-type = xsd:string { pattern = "entry,(.+/.+,?)*" } entry-or-media-type = xsd:string { pattern = "(.+/.+,?)*" } 8.2.5. The "app:categories" Element The "app:categories" element provides a listing of the categories that can be applied to the members of a Collection. The absence of an "app:categories" element means that the category handling of a server is unspecified. Gregorio & de hOra Expires August 9, 2007 [Page 22] Internet-Draft The Atom Publishing Protocol February 2007 atomCategory = element atom:category { atomCommonAttributes, attribute term { text }, attribute scheme { atomURI }?, attribute label { text }?, undefinedContent } appInlineCategories = element app:categories { attribute fixed { "yes" | "no" }?, attribute scheme { atomURI }?, (atomCategory*) } appOutOfLineCategories = element app:categories { attribute href { atomURI }, undefinedContent } appCategories = appInlineCategories | appOutOfLineCategories The app:categories element MAY contain a "fixed" attribute, with a value of either "yes" or "no", indicating whether or not the listing of categories is considered to be a fixed, or closed set. The absence of the "fixed" attribute is equivalent to the presence of a "fixed" attribute with a value of "no". Collections that indicate a fixed set MAY reject members that include categories not specified in the provided listing. Collections that indicate an open set SHOULD NOT reject otherwise acceptable members whose categories are not present in the provided list. The app:categories element MAY contain an "href" attribute, whose value MUST be an IRI reference identifying a Category Document. If the "href" attribute is provided, the app:categories element MUST be empty and the "fixed" and "scheme" attributes MUST NOT be present. Gregorio & de hOra Expires August 9, 2007 [Page 23] Internet-Draft The Atom Publishing Protocol February 2007 9. Creating and Editing Resources 9.1. Member URIs The Member URI supports retrieving, updating and deleting the resource using HTTP GET, PUT and DELETE. Retrieval and updating of Member Entry Resources are done by exchanging Atom Entry representations. Member Entry URIs appear in two places. First, they are returned in a Location header after successful resource creation using POST, as described below. Second, they appear in the Entries of a Collection document as atom:link elements with a link relation of "edit". Each Member Entry SHOULD contain such an atom:link element providing its Member Entry URI. 9.2. Creating resources with POST To add members to a Collection, clients send POST requests to the URI of a Collection. Successful member creation is normally indicated with a 201 ("Created") response code. Collections MAY generate a response with a status code of 415 ("Unsupported Media Type") to indicate that the media-type of the POSTed entity is not allowed or supported by the Collection. When a Member Resource is created in the Collection which received the POST, its Member Entry URI MUST be returned in an HTTP Location header. When the server generates a response with a status code of 201 ("Created"), it SHOULD also return a response body, which if provided, MUST be an Atom Entry Document representing the newly- created resource. Since the server is free to alter the POSTed Entry, for example by changing the content of the "id" element, returning the Entry as described in the previous paragraph can be useful to the client, enabling it to correlate the client and server views of the new Entry. If the POST request contained an Atom Entry Document, and the subsequent response from the server contains a Content-Location header that matches the Location header character-for-character, then the client is authorized to interpret the response entity as being the representation of the newly created Entry. Without a matching Content-Location header the client MUST NOT assume the returned entity is a complete representation of the created resource. Gregorio & de hOra Expires August 9, 2007 [Page 24] Internet-Draft The Atom Publishing Protocol February 2007 The request body sent with the POST need not be an Atom Entry. For example, it might be a picture, or a movie. For a discussion of the issues in POSTing such content, see Section 9.5. 9.2.1. Example Below, the client sends a POST request containing an Atom Entry representation to the URI of the Collection: POST /myblog/entries HTTP/1.1 Host: example.org User-Agent: Thingio/1.0 Authorization: Basic ZGFmZnk6c2VjZXJldA== Content-Type: application/atom+xml Content-Length: nnn Slug: First Post Atom-Powered Robots Run Amok urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2003-12-13T18:30:02Z John Doe Some text. The server signals a successful creation with a status code of 201. The response includes a Location: header indicating the Member Entry URI of the Atom Entry and a representation of that Entry in the body of the response. HTTP/1.1 201 Created Date: Fri, 7 Oct 2005 17:17:11 GMT Content-Length: nnn Content-Type: application/atom+xml; charset="utf-8" Location: http://example.org/edit/first-post.atom Atom-Powered Robots Run Amok urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2003-12-13T18:30:02Z John Doe Some text. Gregorio & de hOra Expires August 9, 2007 [Page 25] Internet-Draft The Atom Publishing Protocol February 2007 The created Entry returned by the server might not match the Entry POSTed by the client. A server MAY change the values of various elements in the Entry such as the atom:id, atom:updated and atom: author values and MAY choose to remove or add other elements and attributes, or change element and attribute values. 9.3. Updating Resources with PUT To update a resource, clients send PUT requests to its Member URI, as specified in [RFC2616]. To avoid unintentional loss of data when editing Member Entries or Media Link Entries, Atom Protocol clients SHOULD preserve all metadata that has not been intentionally modified, including unknown foreign markup as defined in Section 6 of [RFC4287]. 9.4. Deleting Resources with DELETE To delete a resource, clients send DELETE requests to its Member URI, as specified in [RFC2616]. For Media Resources, deletion of a Media Link Entry SHOULD result in the deletion of the associated Media Resource. 9.5. Media Resources and Media Link Entries A client can POST a media type other than application/atom+xml to a Collection. Such a request always creates two new resources - one that corresponds to the entity sent in the request, called the Media Resource, and an associated Member Entry, called the Media Link Entry. Media Link Entries are represented as Atom Entries. The server can signal the media types it will accept via the "accept" element in the Service Document (Section 8.2.4). The Media Link Entry contains the IRI of, and metadata about, the (perhaps non-textual) Media Resource. The Media Link Entry makes the metadata about the Media Resource separately available for retrieval and update. Successful responses to creation requests MUST include the URI of the Media Link Entry in the Location header. The Media Link Entry SHOULD contain an atom:link element with a link relation of "edit-media" that contains the Media Resource IRI. The Media Link Entry MUST have an "atom:content" element with a "src" attribute. The value of the "src" attribute is an IRI of the newly created Media Resource. It is OPTIONAL that the IRI of the "src" attribute on the atom:content element be the same as the Media Resource IRI. For example, the "src" attribute value might instead be a link into a static cache or content distribution network and not the Media Resource IRI. Gregorio & de hOra Expires August 9, 2007 [Page 26] Internet-Draft The Atom Publishing Protocol February 2007 Implementers are asked to note that according to the requirements of [RFC4287], Entries, and thus Media Link Entries, MUST contain an atom:summary element. Upon successful creation of a Media Link Entry, a server MAY choose to populate the atom:summary element (as well as any other required elements such as atom:id, atom:author and atom:title) with content derived from the POSTed entity or from any other source. A server might not allow a client to modify the server selected values for these elements. For resource creation this specification only defines cases where the POST body has an Atom Entry entity declared as an Atom media type ("application/atom+xml"), or a non-Atom entity declared as a non-Atom media type. It does not specify any request semantics or server behavior in the case where the POSTed media-type is "application/ atom+xml" but the body is something other than an Atom Entry. In particular, what happens on POSTing an Atom Feed Document to a Collection using the "application/atom+xml" media type is undefined. The Atom Protocol does not specify a means to create multiple representations of the same resource (for example a PNG and a JPG of the same image) on creation or update. 9.5.1. Examples Below, the client sends a POST request containing a PNG image to the URI of a Collection that accepts PNG images: POST /media/ HTTP/1.1 Host: example.org Content-Type: image/png Slug: The Beach Authorization: Basic ZGFmZnk6c2VjZXJldA== Content-Length: nnn ...binary data... The server signals a successful creation with a status code of 201. The response includes a Location header indicating the Member URI of the Media Link Entry and a representation of that entry in the body of the response. The Media Link Entry includes a content element with a src attribute. It also contains a link using the link relation "edit-media" specifying the IRI to be used for modifying the Media Resource. Gregorio & de hOra Expires August 9, 2007 [Page 27] Internet-Draft The Atom Publishing Protocol February 2007 HTTP/1.1 201 Created Date: Fri, 7 Oct 2005 17:17:11 GMT Content-Length: nnn Content-Type: application/atom+xml; charset="utf-8" Location: http://example.org/media/edit/the_beach.atom The Beach urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2005-10-07T17:17:08Z Daffy Later, the client PUTS a new PNG to the URI indicated in the Media Link Entry's "edit-media" link: PUT /edit/the_beach.png HTTP/1.1 Host: media.example.org Content-Type: image/png Authorization: Basic ZGFmZnk6c2VjZXJldA== Content-Length: nnn ...binary data... The server signals a successful update with a status code of 200. HTTP/1.1 200 Ok Date: Fri, 8 Oct 2006 17:17:11 GMT Content-Length: nnn The client can update the metadata for the picture. First GET the Media Link Entry: GET /media/edit/the_beach.atom HTTP/1.1 Host: example.org Authorization: Basic ZGFmZnk6c2VjZXJldA== The Media Link Entry is returned. Gregorio & de hOra Expires August 9, 2007 [Page 28] Internet-Draft The Atom Publishing Protocol February 2007 HTTP/1.1 200 Ok Date: Fri, 7 Oct 2005 17:18:11 GMT Content-Length: nnn Content-Type: application/atom+xml; charset="utf-8" The Beach urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2005-10-07T17:17:08Z Daffy The metadata can be updated, in this case to add a summary, and then PUT back to the server. PUT /media/edit/the_beach.atom HTTP/1.1 Host: example.org Authorization: Basic ZGFmZnk6c2VjZXJldA== Content-Type: application/atom+xml Content-Length: nnn The Beach urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6a 2005-10-07T17:17:08Z Daffy A nice sunset picture over the water. The update was successful. Gregorio & de hOra Expires August 9, 2007 [Page 29] Internet-Draft The Atom Publishing Protocol February 2007 HTTP/1.1 200 Ok Date: Fri, 7 Oct 2005 17:19:11 GMT Content-Length: 0 Multiple media resources can be added to the Collection. POST /media/ HTTP/1.1 Host: example.org Content-Type: image/png Slug: The Pier Authorization: Basic ZGFmZnk6c2VjZXJldA== Content-Length: nnn ...binary data... The resource is created successfully. HTTP/1.1 201 Created Date: Fri, 7 Oct 2005 17:17:11 GMT Content-Length: nnn Content-Type: application/atom+xml; charset="utf-8" Location: http://example.org/media/edit/the_pier.atom The Pier urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efe6b 2005-10-07T17:26:43Z Daffy The client can now create a new Atom Entry in the blog Entry Collection that references the two newly created Media Resources. Gregorio & de hOra Expires August 9, 2007 [Page 30] Internet-Draft The Atom Publishing Protocol February 2007 POST /blog/ HTTP/1.1 Host: example.org Content-Type: application/atom+xml Slug: A day at the beach Authorization: Basic ZGFmZnk6c2VjZXJldA== Content-Length: nnn A fun day at the beach urn:uuid:1225c695-cfb8-4ebb-aaaa-80da344efa6b 2005-10-07T17:40:02Z Daffy We had a good day at the beach. Later we walked down to the pier. The resource is created successfully. Gregorio & de hOra Expires August 9, 2007 [Page 31] Internet-Draft The Atom Publishing Protocol February 2007 HTTP/1.1 200 Ok Date: Fri, 7 Oct 2005 17:20:11 GMT Content-Length: nnn Content-Type: application/atom+xml; charset="utf-8" Location: http://example.org/blog/atom/a-day-at-the-beach.atom A fun day at the beach http://example.org/blog/a-day-at-the-beach.xhtml 2005-10-07T17:43:07Z Daffy We had a good day at the beach. Later we walked down to the pier. Note that the returned Entry contains a link with a relation of "alternate" that points to the associated XHTML page that was created. This is not required by this specification, but is included to show the kinds of changes a server may make to an Entry. 9.6. The Slug: Header Slug is a HTTP entity-header whose value is a short name that, when accompanying a POST to a Collection, constitutes a request by the client that its value be used as part of the URI for the to-be- created Member Resource. When POSTing an entity to a Collection to add a new Member, the server MAY use this information when creating the Member URI of the newly-created resource, for instance by using some or all of the words in the last URI segment. It MAY also use it when creating the atom:id or as the title of a Media Link Entry (see Section 9.5.). Gregorio & de hOra Expires August 9, 2007 [Page 32] Internet-Draft The Atom Publishing Protocol February 2007 Servers MAY ignore the Slug entity-header and MAY alter its value before using it. For example, the server MAY filter out some characters or replace accented letters with non-accented ones, spaces with underscores, etc. 9.6.1. Slug: Header syntax The syntax of this header MUST conform to the augmented BNF grammar in section 2.1 of the HTTP/1.1 specification [RFC2616]. The TEXT rule is described in section 2.2 of the same document. Slug = "Slug" ":" *TEXT Clients MAY send non-ASCII characters in the Slug entity-header, which they MUST encode using "encoded-words", as defined in [RFC2047]. Servers SHOULD treat the slug as [RFC2047] encoded if it matches the "encoded-words" production. 9.6.2. Example Here is an example of the Slug: header that uses the encoding rules of [RFC2047]. POST /myblog/entries HTTP/1.1 Host: example.org Content-Type: image/png Slug: =?iso-8859-1?q?The_Beach?= Authorization: Basic ZGFmZnk6c2VjZXJldA== Content-Length: nnn ...binary data... See Section 9.2.1 for an example of the Slug: header applied to the creation of a Member Entry Resource. Gregorio & de hOra Expires August 9, 2007 [Page 33] Internet-Draft The Atom Publishing Protocol February 2007 10. Listing Collections Collection Resources MUST provide representations in the form of Atom Feed documents whose Entries contain the IRIs of the Members in the Collection. No structural distinction is made between Collection Feeds and other kinds of Feeds - a Feed might act both as a 'public' feed for subscription purposes and as a Collection Feed. Each Entry in the Feed Document SHOULD have an atom:link element with a relation of "edit" (See Section 11.1). The Entries in the returned Atom Feed SHOULD be ordered by their "atom:updated" property, with the most recently updated Entries coming first in the document order. Clients SHOULD be constructed in consideration of the fact that changes which do not alter the atom: updated value of an Entry will not affect the position of the Entry in a Collection. That is, the Atom Syndication Format states that the value of atom:updated is altered when the changes to an Entry are something that "the publisher considers significant." The atom: updated value is not equivalent to the HTTP Last-Modified: header and can not be used to determine the freshness of cached responses. Clients MUST NOT assume that an Atom Entry returned in the Feed is a full representation of a Member Entry Resource and SHOULD perform a GET on the URI of the Member Entry before editing. 10.1. Collection Paging Collections can contain large numbers of resources. A naive client such as a web spider or web browser could be overwhelmed if the response to a GET contained every Entry in the Collection, and the server would waste large amounts of bandwidth and processing time on clients unable to handle the response. For this reason, servers MAY return a partial listing of the most recently updated Member Resources. Such partial feed documents MUST have an atom:link with a "next" relation whose "href" value is the URI of the next partial listing of the Collection (the next most recently updated Member Resources) where it exists. This is called "Collection paging". The returned Atom Feed MAY contain a subset the Member Entries for a Collection. In addition, the Atom Feed document MAY contain link elements with "rel" attribute values of "next", "previous", "first" and "last" that can be used to navigate through the complete set of matching Entries. For instance, suppose a client is supplied the URI "http://example.org/entries/go" of a Collection of Member entries, where the server as a matter of policy avoids generating feed Gregorio & de hOra Expires August 9, 2007 [Page 34] Internet-Draft The Atom Publishing Protocol February 2007 documents containing more than 10 Entries. The Atom Feed document for the Collection will then represent the first 'page' in a set of 10 linked feed documents. The "first" relation will reference the initial feed document in the set and the "last" relation references the final Atom Feed Document in the set. Within each document, the "next" and "previous" link relations reference the preceding and subsequent documents. ... The "next" and "previous" link elements for the feed 'page' located at "http://example.org/entries/2" would look like this: ... 10.2. The "app:edited" Element The "app:edited" element is a Date construct as defined by [RFC4287] whose value indicates the most recent instant in time when an Entry was edited, including when created. Atom Entry elements in Collection documents SHOULD contain one "app:edited" element, and MUST NOT contain more than one. appEdited = element app:edited ( atomDateConstruct ) The server SHOULD change the value of this element every time a Collection Member Resource or an associated Media Resource has been edited. Gregorio & de hOra Expires August 9, 2007 [Page 35] Internet-Draft The Atom Publishing Protocol February 2007 11. Atom Format Link Relation Extensions 11.1. The "edit" Link Relation This specification adds the value "edit" to the Atom Registry of Link Relations (see section 7.1 of [RFC4287]). The value of "edit" specifies that the value of the href attribute is the IRI of an editable Member Entry. When appearing within an atom:entry, the href IRI can be used to retrieve, update and delete the resource represented by that Entry. An atom:entry MUST contain no more than one "edit" link relation. 11.2. The "edit-media" Link Relation This specification adds the value "edit-media" to the Atom Registry of Link Relations (see section 7.1 of [RFC4287]). When appearing within an atom:entry, the value of the href attribute is an IRI that can be used to modify a Media Resource associated with that Entry. An atom:entry element MAY contain zero or more "edit-media" link relations. An atom:entry MUST NOT contain more than one atom:link element with a rel attribute value of "edit-media" that has the same "type" and "hreflang" attribute values. All "edit-media" link relations in the same Entry reference the same resource. If a client encounters multiple "edit-media" link relations in an Entry then it SHOULD choose a link based on the client preferences for "type" and "hreflang". If a client encounters multiple "edit-media" link relations in an Entry and has no preference based on the "type" and "hreflang" attributes then the client SHOULD pick the first "edit- media" link relation in document order. Gregorio & de hOra Expires August 9, 2007 [Page 36] Internet-Draft The Atom Publishing Protocol February 2007 12. The Atom Format Type Parameter The Atom Syndication Format (RFC 4287) defines the 'application/ atom+xml' media type to identify both Atom Feed and Atom Entry Documents. Implementation experience has demonstrated that Atom Feed and Entry Documents can have different processing models and that there are situations where they need to be differentiated. This document defines an optional 'type' parameter used to differentiate the two types of Atom documents. 12.1. The 'type' parameter This document defines a new "type" parameter for use with the 'application/atom+xml' media type. type = "entry" / "feed" Neither the parameter name nor its value are case sensitive. The value 'entry' indicates that the media type identifies an Atom Entry Document. The root element of the document MUST be atom:entry. The value 'feed' indicates that the media type identifies an Atom Feed Document. The root element of the document MUST be atom:feed. If not specified, the type is assumed to be unspecified, requiring Atom processors to examine the root element to determine the type of Atom document. 12.1.1. Conformance New specifications MAY require that the type parameter be used to identify the Atom Document type. Producers of Atom Entry Documents SHOULD use the type parameter regardless of whether or not it is required. Producers of Atom Feed Documents MAY use the parameter. Atom processors that do not recognize the 'type' parameter MUST ignore its value and examine the root element to determine the document type. Atom processors that do recognize the parameter SHOULD detect and report inconsistencies between the parameter's value and the actual type of the document's root element. Gregorio & de hOra Expires August 9, 2007 [Page 37] Internet-Draft The Atom Publishing Protocol February 2007 13. Atom Publishing Controls This specification defines an Atom Format Structured Extension, as defined in Section 6 of [RFC4287], for publishing control within the "http://purl.org/atom/app#" namespace. 13.1. The "app:control" Element namespace app = "http://purl.org/atom/app#" pubControl = element app:control { atomCommonAttributes, pubDraft? & extensionElement } pubDraft = element app:draft { "yes" | "no" } The "app:control" element MAY appear as a child of an atom:entry which is being created or updated via the Atom Publishing Protocol. The app:control element MUST appear only once in an Entry. The app: control element is considered foreign markup as defined in Section 6 of [RFC4287]. The app:control element and its child elements MAY be included in Atom Feed or Entry Documents. The app:control element can contain an optional "app:draft" element as defined below, and can contain extension elements as defined in Section 6 of [RFC4287]. 13.1.1. The "app:draft" Element The number of app:draft elements in app:control MUST be zero or one. Its value MUST be one of "yes" or "no". A value of "no" indicates a client request that the Member Resource be made publicly visible. If the app:draft element is missing then the value MUST be understood to be "no". The inclusion of the app:draft element represents a request by the client to control the visibility of a Member Resource and the app:draft element MAY be ignored by the server. Gregorio & de hOra Expires August 9, 2007 [Page 38] Internet-Draft The Atom Publishing Protocol February 2007 14. Securing the Atom Publishing Protocol The Atom Publishing Protocol is based on HTTP. Authentication requirements for HTTP are covered in Section 11 of [RFC2616]. The use of authentication mechanisms to prevent POSTing or editing by unknown or unauthorized clients is RECOMMENDED but not required. When authentication is not used, clients and servers are vulnerable to trivial spoofing, denial of service and defacement attacks, however, in some contexts, this is an acceptable risk. The type of authentication deployed is a local decision made by the server operator. Clients are likely to face authentication schemes that vary across server deployments. At a minimum, client and server implementations MUST be capable of being configured to use HTTP Basic Authentication [RFC2617] in conjunction with a TLS connection as specified by [RFC2818]. See [RFC4346] for more information on TLS. The choice of authentication mechanism will impact interoperability. The minimum level of security referenced above (Basic Authentication with TLS) is considered good practice for Internet applications at the time of publication of this specification and sufficient for establishing a baseline for interoperability. Implementers can investigate and use alternative mechanisms regarded as equivalently good or better at the time of deployment. It is RECOMMENDED that clients be implemented in such a way that allows new authentication schemes to be deployed. Because this protocol uses HTTP response status codes as the primary means of reporting the result of a request, servers are advised to respond to unauthorized or unauthenticated requests using an appropriate 4xx HTTP response code (e.g. 401 "Unauthorized" or 403 "Forbidden") in accordance with [RFC2617]. Gregorio & de hOra Expires August 9, 2007 [Page 39] Internet-Draft The Atom Publishing Protocol February 2007 15. Security Considerations As an HTTP-based protocol, APP is subject to the security considerations found in Section 15 of [RFC2616]. 15.1. Denial of Service Atom Publishing server implementations need to take adequate precautions to ensure malicious clients cannot consume excessive server resources (CPU, memory, disk, etc). 15.2. Replay Attacks Atom Publishing server implementations are susceptible to replay attacks. Specifically, this specification does not define a means of detecting duplicate requests. Accidentally sent duplicate requests are indistinguishable from intentional and malicious replay attacks. 15.3. Spoofing Attacks Atom Publishing implementations are susceptible to a variety of spoofing attacks. Malicious clients may send Atom Entries containing inaccurate information anywhere in the document. 15.4. Linked Resources Atom Feed and Entry documents can contain XML External Entities as defined in Section 4.2.2 of [W3C.REC-xml]. Atom implementations are not required to load external entities. External entities are subject to the same security concerns as any network operation and can alter the semantics of an Atom document. The same issues exist for resources linked to by Atom elements such as atom:link and atom: content. 15.5. Digital Signatures and Encryption Atom Entry Documents sent to a server might contain XML Digital Signatures [W3C.REC-xmldsig-core] and might be encrypted using XML Encryption [W3C.REC-xmlenc-core] as specified in Section 5 of [RFC4287]. Servers are allowed to modify received resource representations in ways that can invalidate signatures covering those representations. 15.6. URIs and IRIs Atom Publishing Protocol implementations handle URIs and IRIs. See Section 7 of [RFC3986] and Section 8 of [RFC3987]. Gregorio & de hOra Expires August 9, 2007 [Page 40] Internet-Draft The Atom Publishing Protocol February 2007 16. IANA Considerations 16.1. Content-type registration for 'application/atomserv+xml' An Atom Publishing Protocol Service Document, when serialized as XML 1.0, can be identified with the following media type: MIME media type name: application MIME subtype name: 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. [[anchor32: 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. [[anchor33: update upon publication]] Applications that use this media type: No known applications currently use this media type. Additional information: Magic number(s): As specified for "application/xml" in [RFC3023], section 3.2. File extension: .atomsrv Gregorio & de hOra Expires August 9, 2007 [Page 41] Internet-Draft The Atom Publishing Protocol February 2007 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 Intended usage: COMMON Author/Change controller: This specification's author(s). [[anchor34: update upon publication]] 16.2. Content-type registration for 'application/atomcat+xml' An Atom Publishing Protocol Category Document, when serialized as XML 1.0, can be identified with the following media type: MIME media type name: application MIME subtype name: atomcat+xml Mandatory parameters: None. Optional parameters: "charset": This parameter has identical semantics to the charset parameter of the "application/xml" media type as specified in [RFC3023]. Encoding considerations: Identical to those of "application/xml" as described in [RFC3023], section 3.2. Security considerations: As defined in this specification. [[anchor35: 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. Gregorio & de hOra Expires August 9, 2007 [Page 42] Internet-Draft The Atom Publishing Protocol February 2007 Published specification: This specification. [[anchor36: update upon publication]] Applications that use this media type: No known applications currently use this media type. Additional information: Magic number(s): As specified for "application/xml" in [RFC3023], section 3.2. File extension: .atomcat Fragment identifiers: As specified for "application/xml" in [RFC3023], section 5. Base URI: As specified in [RFC3023], section 6. Macintosh File Type code: TEXT Person and email address to contact for further information: Joe Gregorio Intended usage: COMMON Author/Change controller: This specification's author(s). [[anchor37: update upon publication]] 16.3. Header field registration for 'SLUG' Header field: SLUG Applicable protocol: http [RFC2616] Status: standard. Author/Change controller: IETF (iesg@ietf.org) Internet Engineering Task Force Specification document(s): draft-ietf-atompub-protocol-13.txt ([[anchor38: update on rfc number assignment]]) Related information: Gregorio & de hOra Expires August 9, 2007 [Page 43] Internet-Draft The Atom Publishing Protocol February 2007 16.4. The Link Relation registration "edit" Attribute Value: edit Description: An IRI of an editable Member Entry. When appearing within an atom:entry, the href IRI can be used to retrieve, update and delete the resource represented by that Entry. Expected display characteristics: Undefined; this relation can be used for background processing or to provide extended functionality without displaying its value. Security considerations: Automated agents should take care when this relation crosses administrative domains (e.g., the URI has a different authority than the current document). 16.5. The Link Relation registration "edit-media" Attribute Value: edit-media Description: An IRI of an editable Media Resource. When appearing within an atom:entry, the href IRI can be used to retrieve, update and delete the Media Resource associated with that Entry. Expected display characteristics: Undefined; this relation can be used for background processing or to provide extended functionality without displaying its value. Security considerations: Automated agents should take care when this relation crosses administrative domains (e.g., the URI has a different authority than the current document). 16.6. The Atom Format Media Type Parameter IANA is requested to add a reference to this specification in the 'application/atom+xml' media type registration. Gregorio & de hOra Expires August 9, 2007 [Page 44] Internet-Draft The Atom Publishing Protocol February 2007 17. References 17.1. Normative References [RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text", RFC 2047, November 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types", RFC 3023, January 2001. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC3987] Duerst, M. and M. Suignard, "Internationalized Resource Identifiers (IRIs)", RFC 3987, January 2005. [RFC4287] Nottingham, M. and R. Sayre, "The Atom Syndication Format", RFC 4287, December 2005. [RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.1", RFC 4346, April 2006. [W3C.REC-xml] Yergeau, F., Paoli, J., Bray, T., Sperberg-McQueen, C., and E. Maler, "Extensible Markup Language (XML) 1.0 (Fourth Edition)", World Wide Web Consortium Recommendation REC-xml-20060816, August 2006, . [W3C.REC-xml-infoset] Cowan, J. and R. Tobin, "XML Information Set (Second Edition)", World Wide Web Consortium Recommendation REC- Gregorio & de hOra Expires August 9, 2007 [Page 45] Internet-Draft The Atom Publishing Protocol February 2007 xml-infoset-20040204, February 2004, . [W3C.REC-xml-names] Hollander, D., Bray, T., Tobin, R., and A. Layman, "Namespaces in XML 1.0 (Second Edition)", World Wide Web Consortium Recommendation REC-xml-names-20060816, August 2006, . [W3C.REC-xmlbase-20010627] Marsh, J., "XML Base", W3C REC W3C.REC-xmlbase-20010627, June 2001. [W3C.REC-xmldsig-core] Solo, D., Reagle, J., and D. Eastlake, "XML-Signature Syntax and Processing", World Wide Web Consortium Recommendation REC-xmldsig-core-20020212, February 2002, . [W3C.REC-xmlenc-core] Eastlake, D. and J. Reagle, "XML Encryption Syntax and Processing", World Wide Web Consortium Recommendation REC- xmlenc-core-20021210, December 2002, . 17.2. Informative References [RNC] Clark, J., "RELAX NG Compact Syntax", December 2001, . [W3C.REC-webarch-20041215] Walsh, N. and I. Jacobs, "Architecture of the World Wide Web, Volume One", W3C REC REC-webarch-20041215, December 2004. Gregorio & de hOra Expires August 9, 2007 [Page 46] Internet-Draft The Atom Publishing Protocol February 2007 URIs [1] Gregorio & de hOra Expires August 9, 2007 [Page 47] Internet-Draft The Atom Publishing Protocol February 2007 Appendix A. Contributors The content and concepts within are a product of the Atom community and the Atompub Working Group. [[anchor42: chairs to compile a contribution list for 1.0 --dehora]] Gregorio & de hOra Expires August 9, 2007 [Page 48] Internet-Draft The Atom Publishing Protocol February 2007 Appendix B. RELAX NG Compact Schema This appendix is informative. The Relax NG schema explicitly excludes elements in the Atom Protocol namespace which are not defined in this revision of the specification. Requirements for Atom Protocol processors encountering such markup are given in Section 6.2 and Section 6.3 of [RFC4287]. The Schema for Service Documents: # -*- rnc -*- # RELAX NG Compact Syntax Grammar for the Atom Protocol namespace app = "http://purl.org/atom/app#" namespace atom = "http://www.w3.org/2005/Atom" namespace xsd = "http://www.w3.org/2001/XMLSchema" namespace xhtml = "http://www.w3.org/1999/xhtml" namespace local = "" start = appService # common:attrs atomURI = text appCommonAttributes = attribute xml:base { atomURI }?, attribute xml:lang { atomLanguageTag }?, undefinedAttribute* atomCommonAttributes = appCommonAttributes undefinedAttribute = attribute * - (xml:base | xml:lang | local:*) { text } atomLanguageTag = xsd:string { pattern = "[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*" } atomDateConstruct = appCommonAttributes, xsd:dateTime Gregorio & de hOra Expires August 9, 2007 [Page 49] Internet-Draft The Atom Publishing Protocol February 2007 # app:service appService = element app:service { appCommonAttributes, ( appWorkspace+ & extensionElement* ) } # app:workspace appWorkspace = element app:workspace { appCommonAttributes, ( atomTitle & appCollection* & extensionSansTitleElement* ) } atomTitle = element atom:title { atomTextConstruct } # app:collection appCollection = element app:collection { appCommonAttributes, attribute href { atomURI }, ( atomTitle & appAccept? & appCategories* & extensionSansTitleElement* ) } # app:categories atomCategory = element atom:category { atomCommonAttributes, attribute term { text }, attribute scheme { atomURI }?, attribute label { text }?, undefinedContent } appInlineCategories = element app:categories { attribute fixed { "yes" | "no" }?, attribute scheme { atomURI }?, Gregorio & de hOra Expires August 9, 2007 [Page 50] Internet-Draft The Atom Publishing Protocol February 2007 (atomCategory*) } appOutOfLineCategories = element app:categories { attribute href { atomURI }, undefinedContent } appCategories = appInlineCategories | appOutOfLineCategories # app:accept appAccept = element app:accept { appCommonAttributes, ( appTypeValue? ) } appTypeValue = ( "entry" | media-type |entry-or-media-type ) media-type = xsd:string { pattern = "entry,(.+/.+,?)*" } entry-or-media-type = xsd:string { pattern = "(.+/.+,?)*" } # above is an approximation, rnc doesn't support interleaved text # Simple Extension simpleSansTitleExtensionElement = element * - (app:*|atom:title) { text } simpleExtensionElement = element * - (app:*) { text } # Structured Extension structuredSansTitleExtensionElement = element * - (app:*|atom:title) { (attribute * { text }+, (text|anyElement)*) | (attribute * { text }*, (text?, anyElement+, (text|anyElement)*)) Gregorio & de hOra Expires August 9, 2007 [Page 51] Internet-Draft The Atom Publishing Protocol February 2007 } structuredExtensionElement = element * - (app:*) { (attribute * { text }+, (text|anyElement)*) | (attribute * { text }*, (text?, anyElement+, (text|anyElement)*)) } # Other Extensibility extensionSansTitleElement = simpleSansTitleExtensionElement|structuredSansTitleExtensionElement extensionElement = simpleExtensionElement | structuredExtensionElement undefinedContent = (text|anyForeignElement)* # Extensions anyElement = element * { (attribute * { text } | text | anyElement)* } anyForeignElement = element * - app:* { (attribute * { text } | text | anyElement)* } atomPlainTextConstruct = atomCommonAttributes, attribute type { "text" | "html" }?, text atomXHTMLTextConstruct = atomCommonAttributes, attribute type { "xhtml" }, xhtmlDiv atomTextConstruct = atomPlainTextConstruct | atomXHTMLTextConstruct Gregorio & de hOra Expires August 9, 2007 [Page 52] Internet-Draft The Atom Publishing Protocol February 2007 anyXHTML = element xhtml:* { (attribute * { text } | text | anyXHTML)* } xhtmlDiv = element xhtml:div { (attribute * { text } | text | anyXHTML)* } # EOF The Schema for Category Documents: # -*- rnc -*- # RELAX NG Compact Syntax Grammar for the Atom Protocol namespace app = "http://purl.org/atom/app#" namespace atom = "http://www.w3.org/2005/Atom" namespace xsd = "http://www.w3.org/2001/XMLSchema" namespace local = "" start = appCategories atomCommonAttributes = attribute xml:base { atomURI }?, attribute xml:lang { atomLanguageTag }?, undefinedAttribute* undefinedAttribute = attribute * - (xml:base | xml:lang | local:*) { text } atomURI = text atomLanguageTag = xsd:string { pattern = "[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*" } atomCategory = element atom:category { atomCommonAttributes, attribute term { text }, attribute scheme { atomURI }?, attribute label { text }?, undefinedContent Gregorio & de hOra Expires August 9, 2007 [Page 53] Internet-Draft The Atom Publishing Protocol February 2007 } appInlineCategories = element app:categories { attribute fixed { "yes" | "no" }?, attribute scheme { atomURI }?, (atomCategory*) } appOutOfLineCategories = element app:categories { attribute href { atomURI }, (empty) } appCategories = appInlineCategories | appOutOfLineCategories # Extensibility undefinedContent = (text|anyForeignElement)* anyElement = element * { (attribute * { text } | text | anyElement)* } anyForeignElement = element * - atom:* { (attribute * { text } | text | anyElement)* } # EOF Gregorio & de hOra Expires August 9, 2007 [Page 54] Internet-Draft The Atom Publishing Protocol February 2007 Appendix C. Revision History [[anchor44: This section to be removed upon publication.]] draft-ietf-atompub-protocol-13: Added Lisa's verbiage. Folded in James' Atom Format media type 'type' parameter spec. Updated document references to be more consistent, added URLs to some, and shortened up their anchors. Debugged rnc. draft-ietf-atompub-protocol-11: Parts of PaceAppEdited. PaceSecurityConsiderationsRevised. draft-ietf-atompub-protocol-10: PaceRemoveTitleHeader2, PaceSlugHeader4, PaceOnlyMemberURI,PaceOneAppNamespaceOnly, PaceAppCategories, PaceExtendIntrospection, UseElementsForAppCollectionTitles3, renamed Introspection to Service, lots of good editorials suggestions, updated media example with slug, moved xml conventions to convention sections, renamed XMl related Conventions to Atom Publishing Protocol Documents, added auth header to examples, consolidated definition of all resource types into the model section, added IANA reg info for application/atomcat+xml. draft-ietf-atompub-protocol-09: PaceWorkspaceMayHaveCollections, PaceMediaEntries5, http://www.imc.org/atom-protocol/mail-archive/msg05322.html, and http://www.imc.org/atom-protocol/mail-archive/msg05272.html draft-ietf-atompub-protocol-08: added infoset ref; added wording re IRI/URI; fixed URI/IRI ; next/previous fixed as per Atom LinkRelations Attribute (http://www.imc.org/atom-protocol/mail-archive/msg04095.html); incorporated: PaceEditLinkMustToMay; PaceMissingDraftHasNoMeaning, PaceRemoveMemberTypeMust, PaceRemoveMemberTypePostMust, PaceTitleHeaderOnlyInMediaCollections, PacePreserveForeignMarkup, PaceClarifyTitleHeader, PaceClarifyMediaResourceLinks, PaceTwoPrimaryCollections; draft-ietf-atompub-protocol-07: updated Atom refs to RFC4287; incorporated PaceBetterHttpResponseCode; PaceClarifyCollectionAndDeleteMethodByWritingLessInsteadOfMore; PaceRemoveAcceptPostText; PaceRemoveListTemplate2; PaceRemoveRegistry; PaceRemoveWhoWritesWhat; PaceSimplifyClarifyBetterfyRemoveBogusValidityText; PaceCollectionOrderSignificance; PaceFixLostIntrospectionText; PaceListPaging; PaceCollectionControl; element typo in Listing collections para3 (was app:member-type, not app:list-template); changed post atom entry example to be valid. Dropped inline use of 'APP'. Removed nested diagram from section 4. Added ed notes in the Gregorio & de hOra Expires August 9, 2007 [Page 55] Internet-Draft The Atom Publishing Protocol February 2007 security section. draft-ietf-atompub-protocol-06 - Removed: Robert Sayre from the contributors section per his request. Added in PaceCollectionControl. Fixed all the {daterange} verbage and examples so they all use a dash. Added full rnc schema. Collapsed Introspection and Collection documents into a single document. Removed {dateRange} queries. Renamed search to list. Moved discussion of media and entry collection until later in the document and tied the discussion to the Introspection element app:member-type. draft-ietf-atompub-protocol-05 - Added: Contributors section. Added: de hOra to editors. Fixed: typos. Added diagrams and description to model section. Incorporates PaceAppDocuments, PaceAppDocuments2, PaceSimplifyCollections2 (large-sized chunks of it anyhow: the notions of Entry and Generic resources, the section 4 language on the Protocol Model, 4.1 through 4.5.2, the notion of a Collection document, as in Section 5 through 5.3, Section 7 "Collection resources", Selection resources (modified from pace which talked about search); results in major mods to Collection Documents, Section 9.2 "Title: Header" and brokeout para to section 9.1 Editing Generic Resources). Added XML namespace and language section. Some cleanup of front matter. Added Language Sensitivity to some attributes. Removed resource descriptions from terminology. Some juggling of sections. See: http://www.imc.org/atom-protocol/mail-archive/msg01812.html. draft-ietf-atompub-protocol-04 - Add ladder diagrams, reorganize, add SOAP interactions draft-ietf-atompub-protocol-03 - Incorporates PaceSliceAndDice3 and PaceIntrospection. draft-ietf-atompub-protocol-02 - Incorporates Pace409Response, PacePostLocationMust, and PaceSimpleResourcePosting. draft-ietf-atompub-protocol-01 - Added in sections on Responses for the EditURI. Allow 2xx for response to EditURI PUTs. Elided all mentions of WSSE. Started adding in some normative references. Added the section "Securing the Atom Protocol". Clarified that it is possible that the PostURI and FeedURI could be the same URI. Cleaned up descriptions for Response codes 400 and 500. Rev draft-ietf-atompub-protocol-00 - 5Jul2004 - Renamed the file and re-titled the document to conform to IETF submission guidelines. Changed MIME type to match the one selected for the Atom format. Numerous typographical fixes. We used to have two 'Introduction' sections. One of them was moved into the Abstract the other absorbed Gregorio & de hOra Expires August 9, 2007 [Page 56] Internet-Draft The Atom Publishing Protocol February 2007 the Scope section. IPR and copyright notifications were added. Rev 09 - 10Dec2003 - Added the section on SOAP enabled clients and servers. Rev 08 - 01Dec2003 - Refactored the specification, merging the Introspection file into the feed format. Also dropped the distinction between the type of URI used to create new entries and the kind used to create comments. Dropped user preferences. Rev 07 - 06Aug2003 - Removed the use of the RSD file for auto- discovery. Changed copyright until a final standards body is chosen. Changed query parameters for the search facet to all begin with atom- to avoid name collisions. Updated all the Entries to follow the 0.2 version. Changed the format of the search results and template file to a pure element based syntax. Rev 06 - 24Jul2003 - Moved to PUT for updating Entries. Changed all the mime-types to application/x.atom+xml. Added template editing. Changed 'edit-entry' to 'create-entry' in the Introspection file to more accurately reflect its purpose. Rev 05 - 17Jul2003 - Renamed everything Echo into Atom. Added version numbers in the Revision history. Changed all the mime-types to application/atom+xml. Rev 04 - 15Jul2003 - Updated the RSD version used from 0.7 to 1.0. Change the method of deleting an Entry from POSTing to using the HTTP DELETE verb. Also changed the query interface to GET instead of POST. Moved Introspection Discovery to be up under Introspection. Introduced the term 'facet' for the services listed in the Introspection file. Rev 03 - 10Jul2003 - Added a link to the Wiki near the front of the document. Added a section on finding an Entry. Retrieving an Entry now broken out into its own section. Changed the HTTP status code for a successful editing of an Entry to 205. Rev 02 - 7Jul2003 - Entries are no longer returned from POSTs, instead they are retrieved via GET. Cleaned up figure titles, as they are rendered poorly in HTML. All content-types have been changed to application/atom+xml. Rev 01 - 5Jul2003 - Renamed from EchoAPI.html to follow the more commonly used format: draft-gregorio-NN.html. Renamed all references to URL to URI. Broke out introspection into its own section. Added the Revision History section. Added more to the warning that the example URIs are not normative. Gregorio & de hOra Expires August 9, 2007 [Page 57] Internet-Draft The Atom Publishing Protocol February 2007 Authors' Addresses Joe Gregorio (editor) IBM 4205 South Miama Blvd. Research Triangle Park, NC 27709 US Phone: +1 919 272 3764 Email: joe@bitworking.org URI: http://ibm.com/ Bill de hOra (editor) Propylon Ltd. 45 Blackbourne Square, Rathfarnham Gate Dublin, Dublin D14 IE Phone: +353-1-4927444 Email: bill.dehora@propylon.com URI: http://www.propylon.com/ Gregorio & de hOra Expires August 9, 2007 [Page 58] Internet-Draft The Atom Publishing Protocol February 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Gregorio & de hOra Expires August 9, 2007 [Page 59]