Network Working Group M. Nottingham Internet-Draft January 2003 Expires: July 2, 2003 The 'dns' Media Type Registration Tree draft-nottingham-dns-media-tree-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on July 2, 2003. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document specifies the 'dns' media subtype registration tree, which is intended to ease the deployment of new Internet applications and their associated media types without the need for coordination with a central registry. 1. Requirements notation 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. Introduction Nottingham Expires July 2, 2003 [Page 1] Internet-Draft The 'dns' Media Type Tree January 2003 The registration proceedures for Internet media types [RFC2048] allow for the specification of media type trees, which allow for faceted names to be described in order to increase the efficiency and flexibility of the registration process. They also allows for the creation of new registration trees, with the advice and consent of the IESG. This specification describes one such tree. 3. Motivation The Internet media type system was designed to encourage certain properties, and arguably has been quite successful because of its approach. In particular, IANA acts as a central registry to bring coordination and convenience, and various levels of community review are required before a media type may be registered, to assure some level of quality in and appropriate application of media types. However, the arrival of the Web, and in particular XML, has changed the conditions under which formats are created and used. XML allows the creation of business-specific document and protocol formats by end users. Often, these parties are unfamiliar with IETF and IANA process for registration of media types, and do not have a requirement for recognition by a centralized registry. As such, the cost of media type registration is not justified in the view of some parties that are minting new formats. As a result, many formats are created without corresponding media types (often under the umbrella of 'text/xml' or 'application/xml'). Such formats are not first-class citizens on the Internet or the Web; one cannot content negotiate for them, for example, and one cannot use existing software dispatch mechanisms in MIME software to accommodate them. It should be noted that these undesirable effects disproportionately affect those who wish to use a format in ways that may not have been forseen by its creators. As such, the registration system indirectly discourages the wide use of those mechanisms that leverage media types. Current registration proceedures do allow for some flexibility to accommodate vendor-specific formats (the .vnd tree), "vanity" formats (the .prs tree) and ad hoc, experimental formats (the x. tree and its predecessor, the 'x-' convention). Unfortunately, these mechanisms do not address the problems described here; the x- convention is too brittle for most uses (and indeed its use has been discouraged for some time), and the .vnd and .prs trees are still based on a centralized registry. Nottingham Expires July 2, 2003 [Page 2] Internet-Draft The 'dns' Media Type Tree January 2003 This specification proposes that the widely recognized DNS infrastructure be leveraged to act as a distributed registry, to avoid the possibility of collision, whilst removing the need for an additional centralized registry. The approach is similar to URI schemes that also leverage the DNS to provide locally-managed name spaces. 4. The 'dns' Tree The 'dns' media subtype tree is intended to be used to identify proprietary, ad hoc, experimental, or limited deployment formats. It follows the conventions of faceted name trees as specified by [RFC2048], and is distinguished by the leading facet 'dns.'. This facet MUST be followed by one or more dot-delimited facets that are derived from a domain name, in reverse order. Finally, those facets MUST be followed by on or more facets that indicate the format's identity within that name space. Media types using this tree MUST be minted with the knowledge and permission of the authority responsible for the corresponding Internet domain name. The domain name used MUST be registered in the Internet Registry, as delegated by IANA (see [RFC1591]). For example, if the entity responsible for example.com wished to register a textual media type with the name 'foo' in this fashion, its media type might be: text/dns.com.example.foo XML-based formats SHOULD be conformant with [RFC3023], e.g.: application/dns.com.example.foo+xml If example.com were a multinational concern, it may wish to delegate authority for minting new types to regional departments. It could do so by mandating an additional facet; an application media type minted by the Australian division might be: application/dns.com.example.au.bar whilst a completely separate application format, also identified as 'bar' and minted by the U.S. division might be distinguished as: application/dns.com.example.us.bar 4.1 The 'doc' Attribute Nottingham Expires July 2, 2003 [Page 3] Internet-Draft The 'dns' Media Type Tree January 2003 Media types in the dns tree MAY use the 'doc' attribute, which indicates a URL [RFC2396] that can be used to locate documentation of the identified format. For example: application/dns.com.example.foo; doc="http://www.example.com/formats/ foo.html" The 'doc' attribute is only informative, and MUST NOT be interpreted to alter the nature of the format identified; i.e., a media type with a 'doc' attribute of "foo" MUST be considered equivalent to the same media type with a 'doc' attribute of "bar", or one without a 'doc' attribute. 4.2 Format-Specific Attributes Formats using this dns tree MAY designate their own attributes, which SHOULD be documented at or referenced from the URL specified in the 'doc' attribute, if present. 5. IANA Considerations Implementation of the dns tree does not require IANA coordination. Any media type conformant with this specification is considered to be registered with IANA. 6. Security Considerations 6.1 Change of Ownership Over time, domain names may change ownership. Without proper care, media types created by a domain name's previous owner might collide with those created by the new owner. As a result, when domains which have been used in the registration of media types in the dns tree change hands, the previous owner SHOULD take care to communicate existing media types to the new owner, and the new owner SHOULD take care to avoid collisions. Previous owners MAY publish a transition plan to a new domain, if doing so is judged to cause minimal disruption. 6.2 Unauthorized Registration Media types using the dns tree have no enforced relationship to the domain names that they are based upon; the use of domain names is only a convention to assure proper name spacing. Implementations SHOULD NOT make any assumptions about this relationship, especially Nottingham Expires July 2, 2003 [Page 4] Internet-Draft The 'dns' Media Type Tree January 2003 regarding security issues. References [RFC1591] Postel, J., "Domain Name System Structure and Delegation", RFC 1591, March 1994. [RFC2048] Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures", BCP 13, RFC 2048, November 1996. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2396] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [RFC3023] Murata, M., St. Laurent, S. and D. Kohn, "XML Media Types", RFC 3023, January 2001. Author's Address Mark Nottingham EMail: mailto:mnot@pobox.com Appendix A. Acknowledgements The following people gave input and feedback during the creation of this document; Mark Baker, Don Box, Yaron Goland, Ted Hardie, John Kemp, Graham Klyne, and David Orchard. All errors are the responsibility of the author. Nottingham Expires July 2, 2003 [Page 5] Internet-Draft The 'dns' Media Type Tree January 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. Full Copyright Statement Copyright (C) The Internet Society (2003). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Nottingham Expires July 2, 2003 [Page 6] Internet-Draft The 'dns' Media Type Tree January 2003 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Nottingham Expires July 2, 2003 [Page 7]