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ordering [was: regarding the resolution of issue 431]

From: Mark Nottingham <mark.nottingham@bea.com>
Date: Wed, 16 Jul 2003 11:11:15 -0700
Cc: Marc Hadley <Marc.Hadley@Sun.COM>, Jacek Kopecky <jacek@systinet.com>, "Xml-Dist-App@W3. Org" <xml-dist-app@w3.org>
To: Christopher Ferris <chrisfer@us.ibm.com>
Message-Id: <E3916B98-B7B8-11D7-9C60-00039396E15A@bea.com>

I certainly agree that preserving order shouldn't be required, but it 
may be that ordering profoundly affects the nature of the optimisation, 
and therefore may be interesting to model (probably as a property).

I.e., because we're doing optimisation, the message will always be 
isomorphic to XML, so the ordering of MIME parts in the serialization 
doesn't matter. There may be cases, however, where the ordering does 
affect the message's performance characteristics.

For example, SOAP with Attachments allows for the SOAP envelope to 
appear anywhere in the MIME package, as long as it's referenced 
properly with the start parameter; this is derived from MIME multipart 
packaging. If one were to place the SOAP envelope after all of the 
attachments, however, intermediaries would be forced to buffer 
everything before it (potentially many megabytes) before making a 
decision about the message.

This is an extreme example, but I believe there may be use cases for 
ordered optimisation that are more subtle (including some where the 
SOAP envelope is still packaged up-front).

The alternative is to not talk about ordering at all. The status quo is 
that the sending implementation determines the optimal ordering, which 
may or may not be correct.

Without the ability to direct the ordering of MIME parts, MTOM only 
allows optimisation by reduced size on the wire and reduced processing 
overhead. If those are our only goals, it seems to me that we can 
easily adopt a much less convoluted representation than SOAP over MIME 
multipart.

Cheers,


On Tuesday, July 15, 2003, at 06:23 AM, Christopher B Ferris wrote:

> Hmmm...
>
> It isn't clear to me that preserving order is a necessarily good idea. 
> In
> fact, I think
> that no significance should be accorded the order of parts carried as
> attachments.
>
> Cheers,
>
> Christopher Ferris
> STSM, Emerging e-business Industry Architecture
> email: chrisfer@us.ibm.com
> phone: +1 508 234 3624
>
> xml-dist-app-request@w3.org wrote on 07/14/2003 01:50:30 PM:
>
>>
>> On Friday, Jul 11, 2003, at 07:41 US/Eastern, Jacek Kopecky wrote:
>>>
>>> I also motion to close the (narrower) issue 431 because there seems 
>>> to
>>> be consensus in the WG that intermediaries can, in general, change
> what
>>> is optimized. If we come up with a requirement that is contrary to
> this
>>> (which seems extremely unlikely, considering the voices in the group)
>>> the requirement will be a new information and we'll happily reopen 
>>> the
>>> issue.
>>>
>> As an example, somebody (I don't remember who) mentioned, during the
>> last telcon, a requirement that attachment order be preserved. I think
>> its premature to start closing potentially related issues until such
>> requirements are clear. Of course we can always close then re-open
>> issues, but what's the point in doing that ?
>>
>> Marc.
>>
>> --
>> Marc Hadley <marc.hadley@sun.com>
>> Web Technologies and Standards, Sun Microsystems.
>>
Received on Wednesday, 16 July 2003 14:11:44 GMT

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