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Re: New XMLP Issue Relating to Canonical Forms

From: <noah_mendelsohn@us.ibm.com>
Date: Thu, 9 Oct 2003 16:53:47 -0400
To: xml-dist-app@w3.org
Message-ID: <OFBDD9B82E.C5F5D3DA-ON85256DBA.007203F2@lotus.com>

On Oct 1, at the request of the WG, I requested opening of an issue 
relating to canonical forms.  The note is at [1], and we have indeed 
opened issue 441 [2] (thank you Yves!)  Here I provide my personal opinion 
on this issue.  The questions raised are:

> On the call, there was debate as to whether it would or
> would not be OK for the lexical form of an infoset item
> to change during transmission.  One opinion expressed
> was: yes, no problem, c14n can be run on the sent or
> received infosets in any case where you really care.
> The converse opinion was: no, don't let it change,
> because the SOAP Rec requires that all bindings (MTOM
> or otherwise) transmit the Infoset with full fidelity.

> So, we need to discuss whether to indicate that only
> canonical forms can be optimized by MTOM.

My answer is:

* The SOAP Rec is unambiguous, to be a SOAP binding you must preserve the 
Infoset, which means you must preserve the characters even if in 
non-canonical form (especially since SOAP doesn't even know about types!) 
If it's an integer, you must preserve leading zeros, and if it's 
base64Binary you must preserve whitespace, etc.

* The MTOM optimization seems incapable of distinguishing more than one 
lexical form for a value.

From these two points I conclude that MTOM can optimize at most one 
lexical representation of each value.

> If yes, we need to decide whether to adopt the canonical
> form suggested in the errata to XML schema [1] or some
> other form.

Well, I can see the case for a form with no linebreaks at all, but on 
balance I think it's best to use whatever the Schema WG defines as 
canonical.  So:  "yes", use the canonical form as defined in the Schema 


[1] http://lists.w3.org/Archives/Public/xml-dist-app/2003Oct/0001.html
[2] http://www.w3.org/2000/xp/Group/xmlp-issues#x441

Noah Mendelsohn                              Voice: 1-617-693-4036
IBM Corporation                                Fax: 1-617-693-8676
One Rogers Street
Cambridge, MA 02142
Received on Thursday, 9 October 2003 16:54:30 UTC

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