Network Working Group J. Snell Internet-Draft October 10, 2006 Expires: April 13, 2007 Atom Publishing Protocol Features Extension draft-snell-atompub-feature-01.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 April 13, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document introduces extensions to the Atom Publishing Protocol introspection format for expressing metadata about the features supported by an Atom Publishing Protocol server implementation. Snell Expires April 13, 2007 [Page 1] Internet-Draft APP Features October 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3 3. Feature Introspection and the 'f:feature' element . . . . . . . 3 3.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Publishing Controls and the 'f:control' element . . . . . . . . 5 4.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . . . 9 Snell Expires April 13, 2007 [Page 2] Internet-Draft APP Features October 2006 1. Introduction This document introduces extensions for the Atom Publishing Protocol introspection format for expressing metadata about the features supported by an Atom Publishing Protocol server implementation. 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 BCP 14, [RFC2119]. This specification uses XML Namespaces [W3C.REC-xml-names-19990114] to uniquely identify XML element names. It uses the following namespace prefix for the indicated namespace URI; "f": "http://purl.org/atompub/features/1.0" This specification uses terms from the XML Infoset [W3C.REC-xml- infoset-20040204]. However, this specification uses a shorthand; the phrase "Information Item" is omitted when naming Element Information Items. Therefore, when this specification uses the terms "element" and "attribute" it is referring, respectively, to the Element and Attribute Information Items in Infoset terms. 3. Feature Introspection and the 'f:feature' element A feature is an abstract behavior, function and capability supported by an Atom Publishing Protocol server. Examples of features that might be supported by an APP server include support for a particular set of Atom format extensions, a particular authentication scheme, or a specific set of behaviors. The presence of a f:feature element in an app:collection element is an indication that the collection supports the feature and may require that a client wishing to use the endpoint use that feature. Features are identified using permanent, universally unique IRI's. feature = element f:feature { atomCommonAttributes, attribute ref { atomUri }, attribute required { 'yes' | 'no' }?, attribute href { atomURI }?, attribute label { text }?, (extensionElement*) } Snell Expires April 13, 2007 [Page 3] Internet-Draft APP Features October 2006 The "ref" attribute specifies an IRI that uniquely identifies a feature supported by a collection. The value of the ref attribute MUST be compared on a case-sensitive, character-by-character basis. Relative references MUST NOT be used. A 'required' attribute value of "yes" indicates that clients MUST utilize the identified feature when interacting with the collection. A server MAY reject requests from clients that do not support or use the feature. If not specified, the value is assumed to be "no". An optional 'href' attribute MAY be used to specify the URI of a human-readable description of the feature. The optional 'label' attribute MAY be used to specify a human- readable label for the feature. The value of the 'label' attribute is Language-Sensitive as defined by Section 2 of [RFC4287]. The f:feature element MAY contain child elements and attributes other than those defined in this specification. Such "foreign markup" are considered to be metadata applicable to the feature identified by the f:feature element. Software agents MUST NOT stop processing or signal an error or change their behavior as a result of encountering such foreign markup. An app:collection element MAY contain zero or more f:feature elements but MUST NOT contain more than one with the same ref attribute value. The order in which f:feature elements appears is insignificant. 3.1. Example The following is an example of a collection supporting one required and one optional feature. ... Snell Expires April 13, 2007 [Page 4] Internet-Draft APP Features October 2006 4. Publishing Controls and the 'f:control' element Publishing Controls are a mechanism provided by the Atom Publishing Protocol to embed metadata within atom:entry elements designed to influence the way a server processes the entry. The pub:control element is provided as a convenient container for this metadata within an atom:entry. The Atom Publishing Protocol does not define a mechanism by which clients can discover which publishing controls a server supports. The presence of a f:control element in an app:collection element is an indication that the collection supports the control and may require that a client wishing to use the endpoint use that control. Controls are identified using permanent, universally unique IRI's. control = element f:control { atomCommonAttributes, attribute ref { atomUri }, attribute required { 'yes' | 'no' }?, attribute href { atomURI }?, attribute label { text }?, (extensionElement*) } The "ref" attribute specifies an IRI that uniquely identifies a control supported by a collection. The value of the ref attribute MUST be compared on a case-sensitive, character-by-character basis. Relative references MUST NOT be used. A 'required' attribute value of "yes" indicates that clients MUST utilize the identified control when interacting with the collection. A server MAY reject requests from clients that do not support or use the control. If not specified, the value is assumed to be "no". An optional 'href' attribute MAY be used to specify the URI of a human-readable description of the control. The optional 'label' attribute MAY be used to specify a human- readable label for the control. The value of the 'label' attribute is Language-Sensitive as defined by Section 2 of [RFC4287]. The f:control element MAY contain child elements and attributes other than those defined in this specification. Such "foreign markup" are considered to be metadata applicable to the control identified by the f:control element. Software agents MUST NOT stop processing or Snell Expires April 13, 2007 [Page 5] Internet-Draft APP Features October 2006 signal an error or change their behavior as a result of encountering such foreign markup. An app:collection element MAY contain zero or more f:control elements but MUST NOT contain more than one with the same ref attribute value. The order in which f:control elements appear is insignificant. 4.1. Example The following is an example of a collection supporting one required and one optional control. ... markdown wiki line-breaks An example atom:entry using the listed controls could appear as: ... yes markdown line-breaks ... 5. Security Considerations Specific features and controls supported by a collection may introduce security considerations and concerns beyond those discussed Snell Expires April 13, 2007 [Page 6] Internet-Draft APP Features October 2006 by the Atom Publishing Protocol and Atom Syndication Format specifications. Implementors must refer to the specifications and description of each feature and control to determine the security considerations relevant to each. 6. IANA Considerations This specification does not specify any considerations for IANA. 7. References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom Syndication Format", RFC 4287, December 2005. [W3C.REC-xml-infoset-20040204] Cowan, J. and R. Tobin, "XML Information Set (Second Edition)", World Wide Web Consortium Recommendation REC- xml-infoset-20040204, February 2004, . [W3C.REC-xml-names-19990114] Layman, A., Bray, T., and D. Hollander, "Namespaces in XML", World Wide Web Consortium Recommendation REC-xml- names-19990114, January 1999, . Appendix A. Acknowledgements The author acknowledges the feedback from Elias Torres, Robert Yates, David Johnson, Byrne Reese, Joe Gregorio and the other members of the IETF Atom Publishing working group during the development of this specification. Snell Expires April 13, 2007 [Page 7] Internet-Draft APP Features October 2006 Author's Address James M Snell Phone: Email: jasnell@gmail.com URI: http://snellspace.com Snell Expires April 13, 2007 [Page 8] Internet-Draft APP Features October 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. Snell Expires April 13, 2007 [Page 9]