Network Working Group J. Snell Internet-Draft September 10, 2007 Intended status: Standards Track Expires: March 13, 2008 Atom Publishing Protocol Features Extension draft-snell-atompub-feature-09.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 March 13, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document introduces extensions to the Atom Publishing Protocol service document format for expressing metadata about the behaviors, functions and capabilities supported by an Atom Publishing Protocol collection. Snell Expires March 13, 2008 [Page 1] Internet-Draft Atompub Features September 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3 3. The f:feature element . . . . . . . . . . . . . . . . . . . . 4 3.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Contradictory Features . . . . . . . . . . . . . . . . . . 7 4. The f:type element . . . . . . . . . . . . . . . . . . . . . . 8 4.1. An example f:feature using the f:type element . . . . . . 9 5. Digitally Signing Service Documents . . . . . . . . . . . . . 9 6. The "http://purl.org/atompub/features/1.0" Namespace . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8.1. Registry of Atom Publishing Features . . . . . . . . . . . 10 8.1.1. Initial Assignments . . . . . . . . . . . . . . . . . 11 9. Normative References . . . . . . . . . . . . . . . . . . . . . 24 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 25 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 25 Intellectual Property and Copyright Statements . . . . . . . . . . 27 Snell Expires March 13, 2008 [Page 2] Internet-Draft Atompub Features September 2007 1. Introduction This document introduces extensions for the Atom Publishing Protocol service document [I-D.ietf-atompub-protocol] format for expressing metadata about the behaviors, functions and capabilities supported by an Atom Publishing Protocol collection. 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-20060816] 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. This specification uses the terms "atomUri" and "atomCommonAttributes" from the non-normative RELAX NG Compact schema included in [RFC4287]. Where used, these serve the same purpose and have the same meaning as their use in [RFC4287]. Atom allows the use of IRIs [RFC3987]. Every URI [RFC3986] is also an IRI, so a URI may be used wherever below an IRI is named. There are two special considerations: (1) when an IRI that is not also a URI is given for dereferencing, it MUST be mapped to a URI using the steps in Section 3.1 of [RFC3987] and (2) when an IRI is serving as an identifier, it MUST NOT be so mapped. Any element 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 [RFC3986], establishing the base URI (or IRI) for resolving any relative references found within the effective 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 Snell Expires March 13, 2008 [Page 3] Internet-Draft Atompub Features September 2007 element and its descendents. The language context is only significant for elements and attributes declared to be "Language- Sensitive". Requirements regarding the content and interpretation of xml:lang are specified in XML 1.0 [W3C.REC-xml-20060816], Section 2.12. 3. The f:feature element A feature is an abstract behavior, function and capability supported by an Atom Publishing Protocol collection. Examples of features that might be supported by an Atom publishing server include support for draft entries, scheduled publication of entries, use of a particular set of Atom format extensions, use of a particular authentication scheme, and so on. The f:feature element can be used in an app: collection element to declare that a collection supports the feature specified and may require that a client use that feature when interacting with the endpoint. Features are identified using permanent, universally unique IRI's. namespace f = "http://purl.org/atompub/features/1.0" feature = element f:feature { atomCommonAttributes, attribute ref { atomUri }, attribute status { 'supported' | 'preferred' | 'required' | 'unsupported'}?, attribute href { atomUri }?, attribute label { text }?, (anyElement)* } anyElement = element * - f:feature { (attribute * { text } | text | anyElement)* } The ref attribute specifies a globally unique IRI identifying 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. The status attribute indicates a collection's level of support for the identified feature. The value of the attribute can be "supported", "preferred", "required" or "unsupported". If not specified, the value is assumed to be "supported". If any value other than those listed in this specification is specified, the Snell Expires March 13, 2008 [Page 4] Internet-Draft Atompub Features September 2007 attribute MUST be interpreted as being "supported". Support attribute values are case-insenstive. o The value "supported" indicates that the server supports the identified feature. Clients MAY utilize the feature when interacting with the collection. If the client does not support or recognize a "supported" feature, the client can safely ignore it. o The value "preferred" indicates that the server prefers the use of the identified feature over other contradictory features or over not using the feature at all. The "preferred" support level is applicable to any feature the "supported" level can be applied to. Clients SHOULD utilize the feature when interacting with the collection. o The value "required" indicates that server supports the identified feature and requires that clients utilize it when interacting with a collection. A client that does not support or understand a required feature SHOULD NOT attempt to interact with the collection. o The value "unsupported" indicates that the server explicitly does not support a feature. Clients SHOULD NOT utilize the feature when interacting with the collection. Some features supported by a collection might not require that the client take any specific action when interacting with the server. For such features, the "required" and "preferred" support levels SHOULD be considered to be synonymous with "supported". An optional href attribute MAY be used to specify the URI of a human- readable description of the feature. Relative references MAY be used. 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 any number of child elements and attributes from any XML namespace, with the exception of the f:feature element itself. Such markup is 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 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 appear within the app: collection element is insignificant. Snell Expires March 13, 2008 [Page 5] Internet-Draft Atompub Features September 2007 The f:feature element MAY contain attributes included as part of the atomCommonAttributes production defined by Section 2 of [RFC4287] or any update thereof. When used on an f:feature element, such attributes serve the same purpose described in [RFC4287] or their corresponding specifications. It is important to point out that implementors who add "required" features to existing collections can cause existing client applications to fail and can limit the ability of client applications to evolve independently of a specific server implementation. A better strategy would be to indicate that new features are "preferred". Doing so can allow existing clients to continue to function while communicating the servers preference that new clients utilize the new feature. Server implementors also need to remember that, as an extension to the Service Document syntax, not all Atom Publishing Protocol client applications will recognize and support the use of the f:feature element. Such clients will be incapable of determining which features are supported, preferred, or required. Snell Expires March 13, 2008 [Page 6] Internet-Draft Atompub Features September 2007 3.1. Example The following is an example of a collection supporting one hypothetical required feature, one unsupported feature, and a number of supported features. My Workspace My Atom Collection application/atom+xml;type=entry 3.2. Contradictory Features Some combinations of features can be contradictory when the support level of one or more of those features is "required" and the others are "supported" or "preferred". For instance, a collection that specifies that XHTML values in the atom:title is required and that HTML in an atom:title is supported is contradictory. Such contradictions can cause problems for clients that are attempting to select an appropriate collection based on the support level of various features. A service document MUST NOT specify contradictory features. If a client determines that the features specified in a Snell Expires March 13, 2008 [Page 7] Internet-Draft Atompub Features September 2007 service document are contradictory, the client SHOULD proceed as if the support level for each of those features is "supported". When multiple, potentially contradictory features are specified such that the support level for one is marked as "preferred" and the others are "supported", clients SHOULD use the "preferred" feature. If more than one potentially contradictory feature is marked as "preferred", the client SHOULD proceed as if the support level for each of those features is "supported". 4. The f:type element The content of an f:type element is a media-range as defined in [RFC2616]. type = element f:type { atomCommonAttributes, ( text? ) } Media type parameters are allowed within f:type, but f:type has no notion of preference - "accept-params" or "q" arguments, as specified in Section 14.1 of [RFC2616] are not significant. White space (as defined in [W3C.REC-xml-20060816]) around the f:type element's media-range is insignificant and MUST be ignored. Any number of f:type elements MAY appear as children of an f:feature element. When used with features whose ref attributes identify the "XML Content", "Binary Content" or "Reference Content" features as defined in Section 6.1.1, the f:type elements specify the set of media types that can be specified in the atom:content elements type attribute and thereby the type of content that be included within or referenced by the atom:content. If no f:type elements are specified for these features, clients SHOULD treat this as equivalent to an f:type element with the content "*/*". The order of f:type elements within a f:feature element is insignificant. Snell Expires March 13, 2008 [Page 8] Internet-Draft Atompub Features September 2007 4.1. An example f:feature using the f:type element image/jpg image/png image/gif text/* 5. Digitally Signing Service Documents Because the mechanisms defined in this specification can be used to compel client applications to implement certain behaviors when interacting with a collection, implementors who specify required features are encouraged to sign Service Documents containing the features extension using an Enveloped Signature, as described by XML- Signature and Syntax Processing [W3C.REC-xmldsig-core-20020212]. Processors of Service Documents MUST NOT reject signed documents because they are not capable of verifying it; they MUST continue processing and MAY inform the user of their failure to validate the signature. In other words, the presence of an element with the namespace URI "http://www.w3.org/2000/09/xmldsig#" and a local name of "Signature" as a child of the document element MUST NOT cause a Processor to fail merely because of its presence. Section 6.5.1 of [W3C.REC-xmldsig-core-20020212] requires support for Canonical XML [W3C.REC-xml-c14n-20010315]. However, many implementers do not use it because signed XML documents enclosed in other XML documents have their signatures broken. Thus, Processors that verify signed Service Documents MUST be able to canonicalize with the exclusive XML canonicalization method identified by the URI "http://www.w3.org/2001/10/xml-exc-c14n#", as specified in Exclusive XML Canonicalization [W3C.REC-xml-exc-c14n-20020718]. Section 4.4.2 of [W3C.REC-xmldsig-core-20020212] requires support for DSA signatures and recommends support for RSA signatures. However, because of the much greater popularity in the market of RSA versus DSA, Processors that verify signed Atom Service Documents MUST be able to verify RSA signatures, but do not need be able to verify DSA signatures. Due to security issues that can arise if the keying material for message authentication code (MAC) authentication is not handled properly, Service Documents SHOULD NOT use MACs for signatures. Snell Expires March 13, 2008 [Page 9] Internet-Draft Atompub Features September 2007 6. The "http://purl.org/atompub/features/1.0" Namespace The "http://purl.org/atompub/features/1.0" XML namespace is reserved for future forward-compatible revisions of this specification. Future updates to this document can add new elements and attributes to the namespace. Software written to conform to this version of the specification will not be able to process such markup correctly and, in fact, will not be able to distinguish it from markup error. Processors that encounter such markup MUST NOT stop processing or signal an error. It might be the case that the Processor is able to handle such markup correctly, and does so. Otherwise, processors MAY bypass the markup and MUST NOT change their behavior as a result of the markups presence. 7. Security Considerations Specific features supported by a collection may introduce security considerations and concerns beyond those discussed by the Atom Publishing Protocol and Atom Syndication Format specifications. Implementors must refer to the specifications and description of each feature to determine the security considerations relevant to each. Service documents can be signed using [W3C.REC-xmldsig-core-20020212] and are subject to the security considerations implied by its use. Digital signatures provide authentication, message integrity, and non-repudiation with proof of origin. 8. IANA Considerations 8.1. Registry of Atom Publishing Features The Registry of Atom Publishing Features is maintained by IANA and contains information about known features that can be supported by Atom Publishing Protocol implementations. New assignments are subject to IESG approval, as outlined in [RFC2434]. Requests should be made by email to IANA, which will then forward the request to the IESG, requesting approval. The request should use the following template: o Ref: (A globally unique IRI identifying the feature) o Label: (A human-readable label for the feature) o Support Levels: (A description of the relevant support levels for the feature) Snell Expires March 13, 2008 [Page 10] Internet-Draft Atompub Features September 2007 o Contradictory Features: (A listing of features that are contradictory to this feature when one or more are marked as "required") o Href: (A URI referencing a document containing a detailed definition of the feature) o Security Considerations: 8.1.1. Initial Assignments The Registry of Features initially contains the following assignments: 8.1.1.1. Drafts o Ref: http://www.w3.org/2007/app/drafts o Label: Drafts o Support Levels: * "supported" indicates that the collection accepts entries that contain the app:draft control element. * "required" indicates that the collection requires all entries to contain the app:draft control element. * "unsupported" indicates that the collection does not accept entries that use the app:draft control element or that the server will ignore the element if present. o Contradictory Features: none 8.1.1.2. XHTML Content o Ref: http://www.w3.org/2007/app/xhtml-content o Label: XHTML Content o Support Levels: * "supported" indicates that the collection accepts entries that provide XHTML in the atom:content element. * "required" indicates that the collection requires all entries to provide XHTML in the atom:content element. * "unsupported" indicates that the collection does not accept entries that provide XHTML in the atom:content element. o Contradictory Features: http://www.w3.org/2007/app/html-content, http://www.w3.org/2007/app/text-content, http://www.w3.org/2007/app/xml-content, http://www.w3.org/2007/app/binary-content, http://www.w3.org/2007/app/ref-content 8.1.1.3. HTML Content o Ref: http://www.w3.org/2007/app/html-content Snell Expires March 13, 2008 [Page 11] Internet-Draft Atompub Features September 2007 o Label: HTML Content o Support Levels: * "supported" indicates that the collection accepts entries that provide HTML in the atom:content element. * "required" indicates that the collection requires all entries to provide HTML in the atom:content element. * "unsupported" indicates that the collection does not accept entries that provide HTML in the atom:content element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-content, http://www.w3.org/2007/app/text-content, http://www.w3.org/2007/app/xml-content, http://www.w3.org/2007/app/binary-content, http://www.w3.org/2007/app/ref-content 8.1.1.4. Text Content o Ref: http://www.w3.org/2007/app/text-content o Label: Text Content o Support Levels: * "supported" indicates that the collection accepts entries that provide plain text in the atom:content element. * "required" indicates that the collection requires all entries to provide plain text in the atom:content element. * "unsupported" indicates that the collection does not accept entries that provide plain text in the atom:content element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-content, http://www.w3.org/2007/app/html-content, http://www.w3.org/2007/app/xml-content, http://www.w3.org/2007/app/binary-content, http://www.w3.org/2007/app/ref-content 8.1.1.5. XML Content o Ref: http://www.w3.org/2007/app/xml-content o Label: XML Content o Support Levels: * "supported" indicates that the collection accepts entries that provide well-formed XML in the atom:content element. * "required" indicates that the collection requires all entries to provide well-formed XML in the atom:content element. * "unsupported" indicates that the collection does not accept entries that provide XML in the atom:content element. The MIME media type of acceptable XML formats is specified using one or more f:type elements within the f:feature. o Contradictory Features: http://www.w3.org/2007/app/xhtml-content, http://www.w3.org/2007/app/html-content, http://www.w3.org/2007/app/text-content, http://www.w3.org/2007/app/binary-content, Snell Expires March 13, 2008 [Page 12] Internet-Draft Atompub Features September 2007 http://www.w3.org/2007/app/ref-content 8.1.1.6. Binary Content o Ref: http://www.w3.org/2007/app/binary-content o Label: Binary Content o Support Levels: * "supported" indicates that the collection accepts entries that provide binary content in the atom:content element. * "required" indicates that the collection requires all entries to provide binary content in the atom:content element. * "unsupported" indicates that the collection does not accept entries that provide binary content in the atom:content element. The MIME media type of acceptable binary formats is specified using one or more f:type elements within the f:feature. o Contradictory Features: http://www.w3.org/2007/app/xhtml-content, http://www.w3.org/2007/app/html-content, http://www.w3.org/2007/app/text-content, http://www.w3.org/2007/app/xml-content, http://www.w3.org/2007/app/ref-content 8.1.1.7. Referenced Content o Ref: http://www.w3.org/2007/app/ref-content o Label: XHTML Content o Support Levels: * "supported" indicates that the collection accepts entries that use the atom:content src attribute to reference external content. * "required" indicates that the collection requires all entries to use the atom:content src attribute to reference external content. * "unsupported" indicates that the collection does not accept entries that use the atom:content src attribute. The MIME media type of acceptable referenced resources is specified using one or more f:type elements within the f:feature. o Contradictory Features: http://www.w3.org/2007/app/xhtml-content, http://www.w3.org/2007/app/html-content, http://www.w3.org/2007/app/text-content, http://www.w3.org/2007/app/xml-content, http://www.w3.org/2007/app/binary-content 8.1.1.8. XHTML Title o Ref: http://www.w3.org/2007/app/xhtml-title Snell Expires March 13, 2008 [Page 13] Internet-Draft Atompub Features September 2007 o Label: XHTML Title o Support Levels: * "supported" indicates that the collection accepts entries that provide XHTML in the atom:title element. * "required" indicates that the collectionrequires all entries to provide XHTML in the atom:title element. * "unsupported" indicates that the collection does not accept entries that provide XHTML in the atom:title element. o Contradictory Features: http://www.w3.org/2007/app/html-title, http://www.w3.org/2007/app/text-title 8.1.1.9. HTML Title o Ref: http://www.w3.org/2007/app/html-title o Label: HTML Title o Support Levels: * "supported" indicates that the collection accepts entries that provide HTML in the atom:title element. * "required" indicates that the collection requires all entries to provide HTML in the atom:title element. * "unsupported" indicates that the collection does not accept entries that provide HTML in the atom:title element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-title, http://www.w3.org/2007/app/text-title 8.1.1.10. Text Title o Ref: http://www.w3.org/2007/app/text-title o Label: Text Title o Support Levels: * "supported" indicates that the collection accepts entries that provide plain text in the atom:title element. * "required" indicates that the collection requires all entries to provide plain text in the atom:title element. * "unsupported" indicates that the collection does not accept entries that provide plain text in the atom:title element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-title, http://www.w3.org/2007/app/html-title 8.1.1.11. Summary o Ref: http://www.w3.org/2007/app/summary o Label: Summary o Support Levels: * "supported" indicates that the server will allow the use of the atom:summary element to provide a summary or excerpt that is independent of the atom:content. Snell Expires March 13, 2008 [Page 14] Internet-Draft Atompub Features September 2007 * "required" indicates that the server requires the presence of an atom:summary element to provide a summary or excerpt that is independent of the atom:content. * "unsupported" indicates that the server does not support the use of the atom:summary element to provide a summary or excerpt independent of the atom:content. When an atom:summary is provided by a client, the server will either reject the request or ignore the element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-summary, http://www.w3.org/2007/app/html-summary, http://www.w3.org/2007/app/text-summary 8.1.1.12. Auto Summary o Ref: http://www.w3.org/2007/app/auto-summary o Label: Auto Summary o Support Levels: * "supported" indicates that the server will automatically generate an atom:summary element if the entry provided by the client does not already contain one. * For this feature,"required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the server will not automatically generate an atom:summary element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-summary, http://www.w3.org/2007/app/html-summary, http://www.w3.org/2007/app/text-summary 8.1.1.13. XHTML Summary o Ref: http://www.w3.org/2007/app/xhtml-summary o Label: XHTML Summary o Support Levels: * "supported" indicates that the collection accepts entries that provide XHTML in the atom:summary element. * "required" indicates that the collection requires all entries to provide XHTML in the atom:summary element. * "unsupported" indicates that the collection does not accept entries that provide XHTML in the atom:summary element. o Contradictory Features: http://www.w3.org/2007/app/html-summary, http://www.w3.org/2007/app/text-summary 8.1.1.14. HTML Summary o Ref: http://www.w3.org/2007/app/html-summary o Label: HTML Summary Snell Expires March 13, 2008 [Page 15] Internet-Draft Atompub Features September 2007 o Support Levels: * "supported" indicates that the collection accepts entries that provide HTML in the atom:summary element. * "required" indicates that the collection requires all entries to provide HTML in the atom:summary element. * "unsupported" indicates that the collection does not accept entries that provide HTML in the atom:summary element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-summary, http://www.w3.org/2007/app/text-summary 8.1.1.15. Text Summary o Ref: http://www.w3.org/2007/app/text-summary o Label: Text Summary o Support Levels: * "supported" indicates that the collection accepts entries that provide plain text in the atom:summary element. * "required" indicates that the collection requires all entries to provide plain text in the atom:summary element. * "unsupported" indicates that the collection does not accept entries that provide plain text in the atom:summary element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-summary, http://www.w3.org/2007/app/html-summary 8.1.1.16. XHTML Rights o Ref: http://www.w3.org/2007/app/xhtml-rights o Label: XHTML Rights o Support Levels: * "supported" indicates that the collection accepts entries that provide XHTML in the atom:rights element. * "required" indicates that the collection requires all entries to provide XHTML in the atom:rights element. * "unsupported" indicates that the collection does not accept entries that provide XHTML in the atom:rights element. o Contradictory Features: http://www.w3.org/2007/app/html-rights, http://www.w3.org/2007/app/text-rights 8.1.1.17. HTML Rights o Ref: http://www.w3.org/2007/app/html-rights o Label: HTML Rights o Support Levels: * "supported" indicates that the collection accepts entries that provide HTML in the atom:rights element. * "required" indicates that the collection requires all entries to provide HTML in the atom:rights element. Snell Expires March 13, 2008 [Page 16] Internet-Draft Atompub Features September 2007 * "unsupported" indicates that the collection does not accept entries that provide HTML in the atom:rights element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-rights, http://www.w3.org/2007/app/text-rights 8.1.1.18. Text Rights o Ref: http://www.w3.org/2007/app/text-rights o Label: Text Rights o Support Levels: * "supported" indicates that the collection accepts entries that provide plain text in the atom:rights element. * "required" indicates that the collection requires all entries to provide plain text in the atom:rights element. * "unsupported" indicates that the collection does not accept entries that provide plain text in the atom:rights element. o Contradictory Features: http://www.w3.org/2007/app/xhtml-rights, http://www.w3.org/2007/app/html-rights 8.1.1.19. Authenticated Author o Ref: http://www.w3.org/2007/app/auth-author o Label: Authenticated Author o Support Levels: * "supported" indicates that the server will automatically generate the atom:author element based on the client's authenticated identity. * For this feature,"required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the server will not automatically generate the atom:author for an entry based on the client's authenticated identity. o Contradictory Features: http://www.w3.org/2007/app/multiple-authors, http://www.w3.org/2007/app/person-email, http://www.w3.org/2007/app/person-uri 8.1.1.20. Slug o Ref: http://www.w3.org/2007/app/slug o Label: Slug o Support Levels: * "supported" indicates that the collection accepts the use of the Slug header in POST requests. * "required" indicates that the collection requires that the Slug header be used for all POST requests. Snell Expires March 13, 2008 [Page 17] Internet-Draft Atompub Features September 2007 * "unsupported" indicates that the collection will not accept the use of the Slug header in POST requests or that the header will be ignored. o Contradictory Features: none 8.1.1.21. Multiple Categories o Ref: http://www.w3.org/2007/app/multiple-categories o Label: Multiple Categories o Support Levels: * "supported" indicates that the collection accepts the use of multiple atom:category elements within an entry. * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection will not accept entries with multiple atom:category elements or that that additional atom:category elements will be ignored. o Contradictory Features: none 8.1.1.22. Multiple Authors o Ref: http://www.w3.org/2007/app/multiple-authors o Label: Multiple Authors o Support Levels: * "supported" indicates that the collection accepts the use of multiple atom:author elements within an entry. * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection will not accept entries with multiple atom:author elements or that the additional atom:author elements will be ignored. o Contradictory Features: http://www.w3.org/2007/app/auth-author 8.1.1.23. Multiple Contributors o Ref: http://www.w3.org/2007/app/contributors o Label: Multiple Contributors o Support Levels: * "supported" indicates that the collection accepts the use of multiple atom:contributor elements within an entry. * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection will not accept entries with multiple atom:contributor elements or that the additional atom:contributor elements will be ignored. o Contradictory Features: none Snell Expires March 13, 2008 [Page 18] Internet-Draft Atompub Features September 2007 8.1.1.24. Preserve Infoset o Ref: http://www.w3.org/2007/app/preserve-infoset o Label: Preserve Infoset o Support Levels: * "supported" indicates that the collection will store entries in such a way as to preserve the complete XML infoset of the entry document. * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection may not preserve the complete XML infoset of the entry when storing. o Contradictory Features: none 8.1.1.25. Preserve IDs o Ref: http://www.w3.org/2007/app/preserve-id o Label: Preserve IDs o Support Levels: * "supported" indicates that the collection will preserve the value of the atom:id element as provided by the client. * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection may not preserve the value of the atom:id element as provided by the client (e.g. the server will generate it's own value for the atom:id element. o Contradictory Features: none 8.1.1.26. Preserve Dates o Ref: http://www.w3.org/2007/app/preserve-dates o Label: Preserve Dates o Support Levels: * "supported" indicates that the collection will preserve the value of all date elements as provided by the client. * For this feature,"required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection may not preserve the value of date elements as provided by the client (e.g. the server will generate it's own value for the date elements. o Contradictory Features: none 8.1.1.27. Preserve Title o Ref: http://www.w3.org/2007/app/preserve-title Snell Expires March 13, 2008 [Page 19] Internet-Draft Atompub Features September 2007 o Label: Preserve Title o Support Levels: * "supported" indicates that the collection will preserve the value of the atom:title element as provided by the client. * For this feature,"required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection may not preserve the value of the atom:title as provided by the client (e.g. the server will generate it's own value for the atom:title element. o Contradictory Features: none 8.1.1.28. Preserve Extensions o Ref: http://www.w3.org/2007/app/preserve-extensions o Label: Preserve Extensions o Support Levels: * "supported" indicates that the collection will preserve all extensions contained within an entry. * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection may not preserve all extensions contained within an entry, however some extensions may be preserved. o Contradictory Features: none 8.1.1.29. Preserve Links o Ref: http://www.w3.org/2007/app/preserve-links o Label: Preserve Links o Support Levels: * "supported" indicates that the collection will preserve all atom:link elements contained within an entry. * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection may not preserve all atom:links contained within an entry, however some atom: link elements may be preserved. o Contradictory Features: none 8.1.1.30. Preserve Rights o Ref: http://www.w3.org/2007/app/preserve-rights o Label: Preserve Rights o Support Levels: * "supported" indicates that the collection will preserve the value of the atom:rights element as well as all License Links [RFC4946] contained within an entry. Snell Expires March 13, 2008 [Page 20] Internet-Draft Atompub Features September 2007 * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection may not preserve the value of the atom:rights element or all License Links [RFC4946], however, some rights information may be preserved. o Contradictory Features: none 8.1.1.31. Threading o Ref: http://purl.org/syndication/thread/1.0 o Label: Threading o Support Levels: * "supported" indicates that the collection accepts entries that contain the in-reply-to element as defined by [RFC4685]. * "required" indicates that the collection requires that all entries contain an in-reply-to element. * "unsupported" indicates that the collection will not accept entries containing the in-reply-to element or that the element will be ignored if present. o Contradictory Features: none 8.1.1.32. Scheduled Publishing o Ref: http://www.w3.org/2007/app/scheduled-publishing o Label: Scheduled Publishing o Support Levels: * "supported" indicates that the collection allows clients to specify a future instant in time for the atom:published element when the entry should be made publicly available. * "required" indicates that the collection requires clients to specify a future instant in time for the atom:published element. * "unsupported" indicates that the collection will not allow clients to specify a future instance in time for the atom: published element. o Contradictory Features: none 8.1.1.33. Signed Entries o Ref: http://www.w3.org/2007/app/signed-entries o Label: Signed Entries o Support Levels: * "supported" indicates that the collection may reject entries that do not contain a valid XML Signature as specified in section 5.1 of [RFC4287]. * "required" indicates that the collection requires that all entries contain a valid XML Signature as specified in section 5.1 of [RFC4287]. Snell Expires March 13, 2008 [Page 21] Internet-Draft Atompub Features September 2007 * "unsupported" indicates that the collection will ignore XML Signatures contained in an entry. o Contradictory Features: none 8.1.1.34. Person Email o Ref: http://www.w3.org/2007/app/person-email o Label: Person Email o Support Levels: * "supported" indicates that the collection may reject entries whose atom:author and atom:contributor elements do not contain a non-empty atom:email element. * "required" indicates that the collection requires that all atom:author and atom:contributor elements in an entry contain a non-empty atom:email element.. * "unsupported" indicates that the collection will reject or ignore the atom:email element in all atom:author and atom: contributor elements contained in an entry. o Contradictory Features: http://www.w3.org/2007/app/auth-author 8.1.1.35. Person URI o Ref: http://www.w3.org/2007/app/person-uri o Label: Person URI o Support Levels: * "supported" indicates that the collection may reject entries whose atom:author and atom:contributor elements do not contain a non-empty atom:uri element. * "required" indicates that the collection requires that all atom:author and atom:contributor elements in an entry contain a non-empty atom:uri element.. * "unsupported" indicates that the collection will reject or ignore the atom:uri element in all atom:author and atom: contributor elements contained in an entry. o Contradictory Features: http://www.w3.org/2007/app/auth-author 8.1.1.36. Publish Email o Ref: http://www.w3.org/2007/app/publish-email o Label: Publish Email o Support Levels: * "supported" indicates that the collection will include the value of atom:email elements in public, non-editable representations of an entry. * For this feature, "required" and "preferred" are synonymous with "supported". Snell Expires March 13, 2008 [Page 22] Internet-Draft Atompub Features September 2007 * "unsupported" indicates that the collection will not include the value of atom:email elements in public, non-editable representations of an entry. o Contradictory Features: none 8.1.1.37. Publish URI o Ref: http://www.w3.org/2007/app/publish-uri o Label: Publish URI o Support Levels: * "supported" indicates that the collection will include the value of atom:uri elements in public, non-editable representations of an entry. * For this feature, "required" and "preferred" are synonymous with "supported". * "unsupported" indicates that the collection will not include the value of atom:uri elements in public, non-editable representations of an entry. o Contradictory Features: none 8.1.1.38. XML Language o Ref: http://www.w3.org/2007/app/xml-lang o Label: XML Language o Support Levels: * "supported" indicates that the collection will accept and preserve the value of xml:lang attributes used on an atom:entry element. * "required" indicates that the collection may reject atom:entry elements that do not contain an xml:lang attribute. * "unsupported" indicates that the collection will ignore the xml:lang attribute. o Contradictory Features: none 8.1.1.39. Conditional Modification o Ref: http://www.w3.org/2007/app/conditional o Label: Conditional Modification o Support Levels: * "supported" indicates that the collection provides an Entity Tag or Last Modified timestamp for member resources and supports the use of the HTTP If-Match, If-None-Match, If- Modified-Since or If-Unmodified-Since request headers. * "supported" indicates that the collection provides an Entity Tag or Last Modified timestamp for member resources and requires the use of the HTTP If-Match, If-None-Match, If- Modified-Since or If-Unmodified-Since request headers. Snell Expires March 13, 2008 [Page 23] Internet-Draft Atompub Features September 2007 * "unsupported" indicates that the collection either does not provide an Entity Tag or Last Modified timestamps for member resources or does not otherwise support the use of the HTTP If- Match, If-None-Match, If-Modified-Since and If-Unmodified-Since request headers. o Contradictory Features: none 9. Normative References [I-D.ietf-atompub-protocol] Hora, B. and J. Gregorio, "The Atom Publishing Protocol", draft-ietf-atompub-protocol-17 (work in progress), July 2007. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [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., Ed. and R. Sayre, Ed., "The Atom Syndication Format", RFC 4287, December 2005. [RFC4685] Snell, J., "Atom Threading Extensions", RFC 4685, September 2006. [RFC4946] Snell, J., "Atom License Extension", RFC 4946, July 2007. [W3C.REC-xml-20060816] Paoli, J., Sperberg-McQueen, C., Yergeau, F., Maler, E., and T. Bray, "Extensible Markup Language (XML) 1.0 (Fourth Edition)", World Wide Web Consortium Recommendation REC- xml-20060816, August 2006, . Snell Expires March 13, 2008 [Page 24] Internet-Draft Atompub Features September 2007 [W3C.REC-xml-c14n-20010315] Boyer, J., "Canonical XML Version 1.0", World Wide Web Consortium Recommendation REC-xml-c14n-20010315, March 2001, . [W3C.REC-xml-exc-c14n-20020718] Boyer, J., 3rd, D., and J. Reagle, "Exclusive XML Canonicalization Version 1.0", World Wide Web Consortium Recommendation REC-xml-exc-c14n-20020718, July 2002, . [W3C.REC-xml-infoset-20040204] Tobin, R. and J. Cowan, "XML Information Set (Second Edition)", World Wide Web Consortium Recommendation REC- xml-infoset-20040204, February 2004, . [W3C.REC-xml-names-20060816] Layman, A., Hollander, D., Bray, T., and R. Tobin, "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", World Wide Web Consortium Recommendation REC-xmlbase-20010627, June 2001, . [W3C.REC-xmldsig-core-20020212] Eastlake, D., Solo, D., and J. Reagle, "XML-Signature Syntax and Processing", World Wide Web Consortium Recommendation REC-xmldsig-core-20020212, February 2002, . Appendix A. Acknowledgements The author acknowledges the feedback from the other members of the IETF Atom Publishing working group during the development of this specification. Snell Expires March 13, 2008 [Page 25] Internet-Draft Atompub Features September 2007 Author's Address James M Snell Phone: Email: jasnell@gmail.com URI: http://snellspace.com Snell Expires March 13, 2008 [Page 26] Internet-Draft Atompub Features September 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). Snell Expires March 13, 2008 [Page 27]