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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 March 19, 2002.
Copyright (C) The Internet Society (2001). All Rights Reserved.
1 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???? and extended by RFC????
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2 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 [3] and extended by RFC???? [10] to include names for IETF protocol parameters.
3 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.
4 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.
5 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 for of URI for use in CC/PP, or any other scheme that uses URIs for identification od media features.
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6 The URN sub-namespace for media feature tags is defined as follows.
- Registry name:
- 7 Media-features
- Specification:
- 8 RFC 2506
- Repository:
- 9 http://www.iana.org/assignments/media-feature-tags
- Index value:
- 10 The feature tag name is the registry index value. RFC2506 allows this tag name to contain uppercase letters, lowercase letters, digits, colon (":"), slash ("/"), dot ("."), percent ("%"), and dash ("-"). Feature tags are case-insensitive.
- URN formation:
- 11 The URN for a media feature tag is formed as: "urn:ietf:params:media-features: <tag-name>", where <tag-name> 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:
- 12 '%' is used to introduced an escape sequence and if present in the feature tag name.
- 13 '/' 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.
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14 This table lists some media feature tags, and the corresponding urn: URIs.
- dpi
- 15 urn:ietf:params:dpi
- pix-x
- 16 urn:ietf:params:pix-x
- JBIG-stripe-size
- 17 urn:ietf:params:jbig-stripe-size
- g.acme.special/param
- 18 urn:ietf:params:g.acme.special%2fparam
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19 This document calls for the creation of a new IETF sub-namespace, per RFC???? [10]. Registration details are in the preceding section.
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20 No security considerations are introduced by the specification beyond those already inherrent in use of media feature tags.
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| 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 |
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32
- 00a
- 33 17-Sep-2001: document initially created.
- 00b
- 34 18-Sep-2001: added examples, revision history.
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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.
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