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.
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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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