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Appsawg                                                        Z. Shelby
Internet-Draft                                                 Sensinode
Intended status: Standards Track                          March 29, 2012
Expires: September 30, 2012


                       The +exi Media Type Suffix
                    draft-shelby-exi-registration-01

Abstract

   Efficient XML Interchange (EXI) is an XML representation technique
   specified by the W3C to provie a binary alternative to the standard
   text XML representation.  This document defines a new Structure
   Syntax Suffix "+exi" for use in a specific class of protocols, where
   "exi" content-type encoding or the generic "application/exi" Media
   Type are not applicable.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on September 30, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as



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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  When to Use the +exi Suffix . . . . . . . . . . . . . . . . . . 3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 5
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 5




































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1.  Introduction

   Efficient XML Interchange (EXI) [W3C.REC-exi-20110310] is an XML
   representation technique specified by the W3C to provie a binary
   alternative to the standard text XML representation.  EXI is not a
   generic compression technique like gzip or deflate, but an encoding
   technique specifically for XML that uses either learnt or pre-
   informed schema information.

   This document defines a new Structure Syntax Suffix "+exi" for use in
   a specific class of protocols, where the "exi" content-type encoding
   or generic "application/exi" Media Type defined in
   [W3C.REC-exi-20110310] are not applicable.


2.  When to Use the +exi Suffix

   The EXI standard already defines both an "exi" content-type encoding
   and an "application/exi" Media Type.  This sections discusses when it
   is appropriate to use the new "+exi" Structured Syntax Suffix when
   registring a Media Type.

   Appendix F.1 of [W3C.REC-exi-20110310] clearly describes when the exi
   content-type encoding should be used: "Protocols that can identify
   and negotiate the content coding of XML information independent of
   its media type, SHOULD use the content coding "exi" (case-
   insensitive) to convey the acceptance or actual use of EXI encoding
   for XML information."

   Thus when a protocol depends on the media type to identify that the
   payload is EXI, it can make use of the "application/exi" Media Type
   defined in Appendix F.2 of [W3C.REC-exi-20110310].  This works
   particularly well for applications using EXI in a generic way, and in
   particular in non Schema-informed mode, where protocol specific
   information is not needed to process the payload, in particular the
   XML schema used.  In these cases it is recommended to use the
   "application/exi" Media Type or "exi" content-type encoding.

   The "+exi" Structure Syntax Suffix defined in this document is
   appropriate for use with a special class of protocols that:

   o  Make use of a Media Type to identify the semantics of the protocol
      payload, and offer more that one serialization of the payloads.
      For example, some protocols may offer JSON, XML and EXI
      representations, and

   o  use EXI as a native encoding (without the use of XML as an
      interemediate) in Schema-informed mode, and the base Media Type



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      together with the SchemaID indicates to the protocol the Schema
      that was used to produce the EXI grammar as described in
      Section 4.


3.  Security Considerations

   Security considerations are discussed in Section 4.


4.  IANA Considerations

   This document requests registration of the Structured Syntax Suffix
   "+exi" as follows, following the registration template from Section
   6.2 of [I-D.ietf-appsawg-media-type-regs].

   Name:  Efficient XML Interchange

   +suffix:  "+exi"

   References:  The EXI standard is defined in [W3C.REC-exi-20110310],
      in particular Schema-informed Grammars are defined in Section 8.5
      and the "applicatio/exi" Media Type is defined in Appendix F.2.

   Encoding considerations:  Binary

   Interoperability considerations:  The registration of a Media Type
      using this suffix MUST describe how to determine the XML Schema
      that is used to encode/decode a payload identified by that Media
      Type.  In particular this description defines how to determine the
      Schema used to encode a payload using the SchemaID option of the
      EXI header.  The format of the identifier to be used in the
      SchemaID, a reference to where the corresponding Schema is
      defined, and a description of how future versions of such Schemas
      will be handled MUST be included.  A default Schema version in the
      absence of the SchemaID field MAY be defined.

   Security considerations:  The "+exi" suffix shares the same security
      considerations as XML, described in [RFC3023], Section 10.  In
      addition, the security considerations discussed in the Media Type
      registration for "application/exi" apply as defined in Appendix
      F.2 of [W3C.REC-exi-20110310].

   Contact:  Apps Area Working Group (apps-discuss@ietf.org)







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   Author/Change controller:  The Apps Area Working Group has change
      control over this registration.


5.  Acknowledgments

   This draft is the result of discussions on the Apps Area Working
   Group mailing list.  Thanks to Carine Bournez and Guido Moritz for
   their helpful comments.


6.  Changelog


7.  References

7.1.  Normative References

   [I-D.ietf-appsawg-media-type-regs]
              Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures",
              draft-ietf-appsawg-media-type-regs-03 (work in progress),
              March 2012.

   [W3C.REC-exi-20110310]
              Kamiya, T. and J. Schneider, "Efficient XML Interchange
              (EXI) Format 1.0", World Wide Web Consortium
              Recommendation REC-exi-20110310, March 2011,
              <http://www.w3.org/TR/2011/REC-exi-20110310>.

7.2.  Informative References

   [RFC3023]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media
              Types", RFC 3023, January 2001.


Author's Address

   Zach Shelby
   Sensinode
   Kidekuja 2
   Vuokatti  88600
   FINLAND

   Phone: +358407796297
   Email: zach@sensinode.com





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