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Re: Allow EXI as characterization for XML in the JMS body ?

From: Jean-Baptiste Bugeaud <bugeaud@gmail.com>
Date: Tue, 9 Nov 2010 20:26:41 +0100
Message-ID: <AANLkTimmY1DBYiNf99VQL2=VKm7D2+GrDaQaVbfsjc8B@mail.gmail.com>
To: Amelia A Lewis <alewis@tibco.com>
Cc: public-soap-jms@w3.org
Hello Amy,

I do fully agree with your statements. And basically, I was simply
thinking of making sure the specification does not prevent EXI (or
GZip) from beeing used as a way to encode the content in an
interroperable way.

At this time, there are things that prevent a content encoding (such
as EXI) from beeing used :
 - no way to store the exact content encoding used
 - mandatory alignment of octet and content type
 - no clarification of error scenari

To solve those issues, an idea would be to add content encoding
feature inspired with the existing Content Coding HTTP 1.1 feature.

Practically, this means add a SOAPJMS property for tagging the feature
and WSDL property to indicate the content encoding features available
on the destination.

Doing so, there will be very with minimal impact for implementers but
clear interroperability and extensibility. If you don't plan to suport
any content encoding, on the client side you have nothing to do. And,
on server side, you only need to make sure that you cancel any message
send with a content encoding (aka not "identity" encoding) according
to the spec (aka send the specified fault).

Here is the draft of the specification impact for such a proposition.

===========================

Addendum to section 2.2.1 :


[Definition: soapjms:acceptEncoding] (list of xsd:string)
	* Identifies the list of accepted values for content encoding that
can be set using soapjms:contentEncoding.
	* [Definition: Each values indicated as accept content encoding MUST
be supported by the target destination implementation.†]
	* [Definition: A caller SHOULD only use Each values indicated as
accept content encoding MUST be supported by the target.†]


Addendum to section 2.2.3 :


[Definition: soapjms:contentEncoding] (xsd:string)
	* Identifies the transformation that has been applied to the message
payload body.
        * [Definition: If the content encoding is specified, it is
checked to ensure that it matches the content encoding values
supported. A fault MUST be generated with subcode
contentEncodingNotSupported if the encoding values do not match.†]
	* [Definition: If the content encoding is specified, it is checked to
ensure that it matches the encoding value from the supplied XML. A
fault MUST be generated with subcode contentEncodingMismatch if the
content encoding values do not match the encoded content.†]
	* [Definition: If no content encoding property is set or no value is
set, the property MUST be assumed as "identity".†]
	* [Definition: If soapjms:acceptEncoding was set, the contentEncoding
value SHOULD be set to any of those value.†]
	
Update to section 2.4 :

change
"The bytes or characters of the JMS Message payload correspond to the
MIME format as indicated by the definition of the contentType
property"
with
"The bytes or characters of the JMS Message payload correspond to the
MIME format as indicated by the definition of the contentType property
and the contentEncoding property".

change
"and specifies an appropriate value for the contentType property which"
by
"and specifies an appropriate value for the contentType property and
contentEncoding property which

Alter of 2.4.1 :
 a new point in the list of consideration for TextMessage :
	- Messages using the SOAP JMS content encoding will need to use
Content-Transfer-Encoding for attachment parts.


Addendum to section 2.8 :

 Add of :
 - contentEncodingNotSupported
 - contentEncodingMismatch

Addendum to section 3.4 :
 Add the element acceptEncoding in the list.

Add of a new section  :
 X.X Content Encoding
 Content coding values indicate an encoding transformation that has
been or can be applied to the JMS message body content.
 Content codings are primarily used to allow a message body to be
compressed or otherwise usefully transformed without losing the
identity of its underlying media type and without loss of information.

 All content-coding values are case-sensitive.

 The Internet Assigned Numbers Authority (IANA) acts as a registry for
content encoding value tokens. Initially the list of valid values is
taken from the HTTP 1.1 Content Coding values (see
http://www.iana.org/assignments/http-parameters/http-parameters.xml#http-parameters-1
).

 New content-coding value tokens SHOULD be registered to allow
interoperability between clients and servers, specifications of the
content coding algorithms needed to implement a new value SHOULD be
publicly available and adequate for independent implementation, and
conform to the purpose of content coding defined in this section.

 An implementation SHOULD support gzip or (and ?) exi content encoding.

=====================

Regards,
JB


2010/11/9 Amelia A Lewis <alewis@tibco.com>:
> What specific changes would need to be made to the specification in
> order to avoid ruling out the use of EXI?
>
> I'm phrasing this differently than you have, of course: I do not think
> incorporating an EXI *requirement* is in scope for the SOAP/JMS working
> group.  In fact, I do not think, at this stage of the specification
> work, that we ought to introduce a new optional dependency.  However, I
> will readily acknowledge that a vendor might wish to enable EXI in SOAP
> over JMS, and if our specification forbids it, we shouldn't.
>
> Rephrasing: I think we should not forbid, nor require, nor even specify
> as optional behavior the use of EXI in SOAP over JMS, but should phrase
> our specification in such a way that a person or group writing an
> extension specification could make using EXI possible and interoperable.
>
> Amy!
> On Mon, 8 Nov 2010 19:40:58 +0100, Jean-Baptiste Bugeaud wrote:
>> Dear SOAP-JMS Editors,
>>
>> Could it be possible to allow EXI characterisation (see
>> http://www.w3.org/TR/exi/) in the message body §2.4 as well ?
>>
>> Using EXI makes sense in a JMS context for any mission critical system
>> where latency has to be kept at a the minimum.
>>
>> EXI would also help a lot :
>>  - keeping XML processing CPU overhead low (message inspection for
>> active routing for instance)
>>  - handling & streaming of huge attachement (base64bin saved as octet
>> binary set for instance)
>>  - etc
>>
>> Regards,
>> JB BUGEAUD
>>
>>
> --
> Amelia A. Lewis
> Senior Architect
> TIBCO/Extensibility, Inc.
> alewis@tibco.com
>
Received on Tuesday, 9 November 2010 19:27:10 GMT

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