Network Working Group                                      S. St.Laurent
Internet-Draft                                     O'Reilly & Associates
Expires: July 21, 2002                                  January 20, 2002


                Registration of xmlns Media Feature Tag
                  draft-stlaurent-feature-xmlns-00.txt

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
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   This Internet-Draft will expire on July 21, 2002.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document registers a media feature tag 'xmlns', per RFC 2506,
   intended for use in a Content-features features header to indicate
   the XML namespaces used in an XML document.  This information
   augments MIME content-type information, providing a finer granularity
   of content description for XML documents.










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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Registration . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Registration issues  . . . . . . . . . . . . . . . . . . . . .  6
   3.1 General interest to the Internet Community . . . . . . . . . .  6
   3.2 Namespaces as media  . . . . . . . . . . . . . . . . . . . . .  6
   3.3 Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   3.4 IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  6
       References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
       Author's Address . . . . . . . . . . . . . . . . . . . . . . .  9
   A.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   B.  Revision History . . . . . . . . . . . . . . . . . . . . . . . 11
       Full Copyright Statement . . . . . . . . . . . . . . . . . . . 12





































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1. Introduction

   MIME Content-Type identifiers have proven very useful as tools for
   describing homogeneous information.  They do not fare as well at
   describing content which is unpredictably heterogeneous.  XML
   documents may be homogeneous, but are also frequently heterogeneous.
   It is not difficult to create, for instance, an XHTML [25] document
   which also contains RDF [19] metadata, MathML [20] equations,
   hypertext using XLink [22], and SVG [21] graphics.  XSLT [17]
   stylesheets routinely include information in both the XSLT namespace
   and in the namespace of the format resulting from proper execution of
   the stylesheet.

   This document specifies a Media Feature which identifies the URIs
   used as XML namespaces [14] in a given XML document.  While a list of
   namespaces cannot tell a recipient application everything about the
   use of those namespaces and there interactions in a given document,
   it can provide a baseline understanding.

   A program may be better able to choose among a set of XSLT
   stylesheets if it knows the namespaces of the results they generate,
   or a renderer may take advantage of foreknowledge to begin setting up
   components before content actually arrives.  Processors working with
   SOAP [18] envelopes may find it useful to know what they will be
   facing inside the envelope.  Applications faced with "unknown" XML
   namespaces may want to attempt to download RDDL [16] documents to
   collect information on how to process them.  Applications may also
   choose to reject documents containing unknown namespaces.

   This feature is designed primarily to be used with the XML Media
   Types defined in RFC 3023 [12].  By providing additional information
   about the content of the document beyond its overall type, it
   provides XML applications with a more comprehensive view of
   information they may (or may not) wish to process, potentially
   avoiding wasted parsing and processing.
















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2. Registration

   Media feature tag name: xmlns

   ASN.1 identifier associated with feature tag: New assignment by IANA

   Summary of the media feature indicated by this feature tag: This
      feature tag is used to identify XML namespaces either contained in
      a given document or processable by a given recipient.

   Values appropriate for use with this feature tag: The feature tag
      must contain a String conforming to the RFC 2396 [4] syntax for
      URI references, as restricted by plenary [15].  URI references
      must be absolute.

   The feature tag is intended primarily for use in the following
   applications, protocols, services, or negotiation mechanisms: Any
      protocol that exchanges XML-formatted information in MIME
      encapsulation

      Examples of typical use:

      For an XHTML document containing SVG, MathML, SMIL, and XLink
      content:

        Content-Type: application/xhtml+xml
        Content-features: (|
           (xmlns="http//www.w3.org/1999/xhtml")
           (xmlns="http//www.w3.org/2000/svg")
           (xmlns="http//www.w3.org/1998/Math/MathML")
           (xmlns="http//www.w3.org/2001/SMIL20/")
           (xmlns="http//www.w3.org/1999/xlink")
        )

      Or, using multiple Content-features headings:

        Content-Type: application/xhtml+xml
        Content-features (xmlns="http//www.w3.org/1999/xhtml")
        Content-features (xmlns="http//www.w3.org/2000/svg")
        Content-features (xmlns="http//www.w3.org/1998/Math/MathML")
        Content-features (xmlns="http//www.w3.org/2001/SMIL20/")
        Content-features (xmlns="http//www.w3.org/1999/xlink")









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      For an application indicating that it accepts SMIL, XHTML, or SVG
      content:

     (| (xmlns="http//www.w3.org/2001/SMIL20/");q=1.0
        (xmlns="http//www.w3.org/1999/xhtml");q=0.9
        (xmlns="http//www.w3.org/2000/svg");q=0.8
        )

      Applications that want to specify combinations of namespaces they
      consider acceptable may do so using combinations of & and |, and
      may also mix the xmlns feature with other media features, as
      described in RFC 2533 [6].

   Related standards or documents: Namespaces in XML [14], XML Media
      Types [12]

   Considerations particular to use in individual applications,
   protocols, services, or negotiation mechanisms: None

   Interoperability considerations: None.

   Security considerations: If it is known that there is a security bug
      in the handling of a particular namespace in a particular
      environment, knowing that a device can accept that namespace may
      slightly help an attacker.

   Additional information: None

   Name(s) & email address(es) of person(s) to contact for further
   information: Simon St.Laurent <simonstl@simonstl.com>

   Intended usage COMMON

   Author/Change controller: IETF

















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3. Registration issues

3.1 General interest to the Internet Community

   While XML processing may generally seem like something specific to
   the XML community, XML's reach is growing rapidly.  XML is now in
   regular use for Web Services (XML-RPC, SOAP), vector graphics (SVG),
   mathematics (MathML), instant messaging (Jabber), information
   transformation (XSLT), and a wide variety of other projects.

   Because of this general and growing interest, this document
   recommends registering the 'xmlns' feature in the IETF tree per RFC
   2506 [5].

3.2 Namespaces as media

   Namespaces are not strictly presentational media information, as are
   many of the previously registered media features.  They do, however,
   define the set of tools used to present information, much as the type
   [10], charset [11], and language [11] media features do.

3.3 Security Considerations

   Security considerations for this registration are listed in the
   registration above.  Considerations for Media Features in general are
   described in RFC 2506.

3.4 IANA Considerations

   Section 2 of this document calls for the registration of a media
   feature tag, per RFC 2506.




















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References

   [1]   Freed, N. and N. Borenstein, "Multipurpose Internet Mail
         Extensions (MIME) Part One: Format of Internet Message Bodies",
         RFC 2045, November 1996.

   [2]   Freed, N. and N. Borenstein, "Multipurpose Internet Mail
         Extensions (MIME) Part Two: Media Types", RFC 2046, November
         1996.

   [3]   Freed, N., Klensin, J. and J. Postel, "Multipurpose Internet
         Mail Extensions (MIME) Part Four: Registration Procedures", RFC
         2048, November 1996.

   [4]   Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
         Resource Identifiers (URI): Generic Syntax", RFC 2396, August
         1998.

   [5]   Holtman, K., Mutz, A. and T. Hardie, "Media Feature Tag
         Registration Procedure", RFC 2506, March 1999.

   [6]   Klyne, G., "A Syntax for Describing Media Feature Sets", RFC
         2533, March 1999.

   [7]   Fielding, R., Gettys, J., Mogul, J., Nielsen, H., Masinter, L.,
         Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
         HTTP/1.1", RFC 2616, June 1999.

   [8]   Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, June
         1999.

   [9]   Klyne, G., "Indicating Media Features for MIME Content", RFC
         2912, September 2000.

   [10]  Klyne, G., "MIME Content Types in Media Feature Expressions",
         RFC 2913, September 2000.

   [11]  Hoffman, P., "Registration of Charset and Languages Media
         Features Tags", RFC 2987, November 2000.

   [12]  Murata, M., St.Laurent, S. and D. Kohn, "XML Media Types", RFC
         3023, January 2001.

   [13]  Bray, T., Paoli, J. and C. Sperberg-McQueen, "Extensible Markup
         Language (XML) 1.0", World Wide Web Consortium Recommendation
         REC-xml, February 1998, <http://www.w3.org/TR/REC-xml>.

   [14]  Bray, T., Hollander, D. and A. Layman, "Namespaces in XML",



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         World Wide Web Consortium Recommendation REC-xml-names, January
         1999, <http://www.w3.org/TR/REC-xml-names/>.

   [15]  Connolly, D., "W3C XML Plenary Decision on relative URI
         References In namespace declarations", September 2000, <http://
         lists.w3.org/Archives/Public/xml-uri/2000Sep/0083.html>.

   [16]  Borden, J. and T. Bray, "Resource Directory Description
         Language (RDDL)", June 2001, <http://www.rddl.org>.

   [17]  Clark , J., "XSL Transformations (XSLT) Version 1.0", World
         Wide Web Consortium Recommendation XSLT, November 1999, <http:/
         /www.w3.org/TR/xslt>.

   [18]  Mitra , N., "SOAP Version 1.2", World Wide Web Consortium
         Working Draft SOAP, December 2001, <http://www.w3.org/TR/
         soap12-part0/>.

   [19]  Lassila, O. and R. Swick, "Resource Description Framework (RDF)
         Model and Syntax Specification", World Wide Web Consortium
         Recommendation RDF-syntax, February 1999, <http://www.w3.org/
         TR/REC-rdf-syntax>.

   [20]  Carlisle, D., Ion, P., Miner, R. and N. Poppelier,
         "Mathematical Markup Language 2.0 (MathML)", World Wide Web
         Consortium Recommendation MathML, February 2001, <http://
         www.w3.org/TR/MathML2/>.

   [21]  Ferraiolo, J., "Scalable Vector Graphics (SVG)", World Wide Web
         Consortium Working Draft SVG, August 1999, <http://www.w3.org/
         TR/SVG>.

   [22]  DeRose, S., Maler, E. and D. Orchard, "XML Linking Language
         (XLink)", World Wide Web Consortium Recommendation XLink, June
         2001, <http://www.w3.org/TR/xlink/>.

   [23]  DeRose, S., Daniel Jr., R. and E. Maler, "XML Pointer Language
         (XPointer)", World Wide Web Consortium Working Draft XPointer,
         July 1999, <http://www.w3.org/TR/xptr>.

   [24]  Marsh, J., "XML Base", World Wide Web Consortium Recommendation
         XML Base, June 2000, <http://www.w3.org/TR/xmlbase>.

   [25]  Pemberton, S. and  et al, "XHTML 1.0: The Extensible HyperText
         Markup Language", World Wide Web Consortium Recommendation REC-
         xhtml1, January 2000, <http://www.w3.org/TR/xhtml1>.

   [26]  Altheim, M. and S. McCarron, "XHTML 1.1: Module-based XHTML",



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         World Wide Web Consortium Recommendation REC-xhtml11, January
         2000, <http://www.w3.org/TR/xhtml11/>.


Author's Address

   Simon St.Laurent
   O'Reilly & Associates
   1259 Dryden Road
   Ithaca, New York  14850
   USA

   EMail: simonstl@simonstl.com
   URI:   http://www.simonstl.com/





































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Appendix A. Acknowledgements

   Thanks to Graham Klyne, Jonathan Borden, Murata Makoto, Edd Dumbill,
   and Eric van der Vlist for editorial and technical comments on an
   early version of this document.  Their help does not, of course,
   constitute endorsement.













































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Appendix B. Revision History

   First version.

   [To be deleted before publication.]














































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Full Copyright Statement

   Copyright (C) The Internet Society (2002).  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.



















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