Network Working Group G. Klyne Internet-Draft MIMEsweeper Group Expires: May 7, 2002 Nov 6, 2001 A URN sub-namespace for media feature tags draft-klyne-urn-ietf-conneg-01 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 May 7, 2002. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract This specification defines a form of URN to be used for media feature tags registered according to RFC 2506. The URN namespace used is 'ietf', defined by RFC 2648 and extended by RFC????. Klyne Expires May 7, 2002 [Page 1] Internet-Draft URNs for media feature tags Nov 2001 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Registration template . . . . . . . . . . . . . . . . . . . . 3 3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. IANA considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security considerations . . . . . . . . . . . . . . . . . . . 5 References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 6 A. Revision history . . . . . . . . . . . . . . . . . . . . . . . 6 A.1 draft-klyne-urn-ietf-conneg-00 . . . . . . . . . . . . . . . . 6 B. Todo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 7 Klyne Expires May 7, 2002 [Page 2] Internet-Draft URNs for media feature tags Nov 2001 1. Introduction This specification defines a form of URN to be used for media feature tags registered according to RFC 2506 [3]. The URN namespace used is 'IETF', defined by RFC 2648 [5] and extended by RFC???? [10] to include names for IETF protocol parameters. 1.1 Background RFC 2506 [3] defines a registry for feature tags used to describe media features of systems and documents. These tags can be used to describe the capabilities and preferences of systems that send or receive data, and also the features used by specific data instances. A companion document, RFC 2533 [4], describes a format for combining these tags into expressions that describe the combined media features of a system or document. W3C have also been working on an XML [6] format for expressing client capabilities called CC/PP [9]. It is based on RDF [8], a generic XML metadata format that uses URIs to identify objects and the relationships between them. It has for some time been a goal that RFC2506-registered media feature tags will be usable by CC/PP profiles, providing some basis for interworking between IETF and W3C content negotiation schemes. By defining a URI form based on the urn: scheme, this specification satsifies that goal. Thus, any new media feature tag registered will also have a defined form of URI for use in CC/PP, or any other scheme that uses URIs for identification od media features. 2. Registration template The URN sub-namespace for media feature tags is defined as follows. Registry name: media-feature Specification: RFC 2506 [3] Repository: http://www.iana.org/assignments/media-feature-tags Index value: The feature tag name is the registry index value. RFC 2506 allows this tag name to contain uppercase letters, lowercase letters, digits, colon (":"), slash ("/"), dot ("."), percent ("%"), and dash ("-"). Media feature tags are case-insensitive. Klyne Expires May 7, 2002 [Page 3] Internet-Draft URNs for media feature tags Nov 2001 URN formation: The URN for a media feature tag is formed as: "urn:ietf:params:media-feature:", where is the media feature registry index value. RFC 2141 [1] defines the format of URNs. Allowable characters include all of those noted above, with the following exceptions: * '%' is used to introduced an escape sequence and if present in the feature tag name. * '/' is reserved for future use and is recommended to be escaped. These characters, if they appear as part of a media feature tag name should be replaced by their %-encoded equivalent (per URI specification [2]); i.e. '%' is represented as '%25', and '/' as '%2f'. URNs are defined by RFC 2141 [1] as lexically equivalent if they are identical following case normalization of the urn scheme name, the namespace name and any %-escaping used. Media feature tags are defined such that upper- and lower-case ASCII characters are not distinguished. Thus, in forming a URN, all ASCII characters in the media feature tag must be expressed in lower case. 3. Examples This table lists some media feature tags, and the corresponding urn: URIs. dpi urn:ietf:params:media-feature:dpi pix-x urn:ietf:params:media-feature:pix-x JBIG-stripe-size urn:ietf:params:media-feature:jbig-stripe-size g.acme.special/param urn:ietf:params:media-feature:g.acme.special%2fparam Klyne Expires May 7, 2002 [Page 4] Internet-Draft URNs for media feature tags Nov 2001 4. IANA considerations This document calls for the creation of a new IETF sub-namespace, per RFC???? [10]. Registration details are in the preceding section. 5. Security considerations No security considerations are introduced by this specification beyond those already inherent in use of media feature tags. References [1] Moats, R., "URN Syntax", RFC 2141, May 1997. [2] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [3] Holtman, K., Mutz, A. and T. Hardie, "Media Feature Tag Registration Procedure", BCP 31, RFC 2506, March 1999. [4] Klyne, G., "A Syntax for Describing Media Feature Sets", RFC 2533, March 1999. [5] Moats, R., "A URN Namespace for IETF Documents", RFC 2648, August 1999. [6] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C Recommendation xml, October 2000, . [7] Bray, T., Hollander, D. and A. Layman, "Namespaces in XML", W3C Recommendation xml-names, January 1999, . [8] Lassila, O. and R. Swick, "Resource Description Framework (RDF) Model and Syntax Specification", W3C Recommendation rdf-syntax, February 1999, . [9] Klyne, G., Reynolds, F., Woodrow, C. and H. Ohta, "Composite Capability/Preference Profiles (CC/PP): Structure and Vocabularies", W3C Working Draft CCPP-struct-vocab, March 2001, . [10] Mealling, M., Masinter, L., Hardie, T. and G. Klyne, "An IETF URN Sub-namespace for Registered Protocol Parameters", Internet draft draft-mealling-iana-urn-02, August 2001, Klyne Expires May 7, 2002 [Page 5] Internet-Draft URNs for media feature tags Nov 2001 . Author's Address Graham Klyne MIMEsweeper Group 1310 Waterside Arlington Business Park Theale, Reading RG7 4SA UK Phone: +44 118 903 8000 Fax: +44 118 903 9000 EMail: Graham.Klyne@MIMEsweeper.com Appendix A. Revision history [[[This section to be removed on final publication]]] A.1 draft-klyne-urn-ietf-conneg-00 00a 17-Sep-2001: document initially created. 00b 18-Sep-2001: added examples, revision history. 00c 24-Sep-2001: Small editorial fixes. 01a 06-Nov-2001: More small editorial fixes. Appendix B. Todo o Align with urn:ietf:params: draft as it develops. o Replace RFC???? with appropriate RFC numbers, when issued. o Remove [[[editorial comments]]]. Klyne Expires May 7, 2002 [Page 6] Internet-Draft URNs for media feature tags Nov 2001 Full Copyright Statement Copyright (C) The Internet Society (2001). 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 assigns. 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 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Klyne Expires May 7, 2002 [Page 7]