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RE: An analysis of mustUnderstand and related issues

From: Doug Davis <dug@us.ibm.com>
Date: Wed, 16 May 2001 20:16:25 -0400
To: Noah_Mendelsohn@lotus.com
Cc: "Henrik Frystyk Nielsen" <henrikn@microsoft.com>, xml-dist-app@w3.org
Message-ID: <OF9AE1F833.6E3E7637-ON85256A4F.0000DE9B@raleigh.ibm.com >
Why wouldn't a header like:
  <t:orderMeansSomething xmlns:t="some-uri" mustUnderstand="1">
  1
  </t:orderMeansSomething>
who's semantics are defined to mean that if you understand
this header then you will make sure all headers are processed
in the order in which they appear in the xml, work?  One of the
issues Glen brought up was how to verify that this header
will be noticed before all others (assuming that's important),
well just add that to the semantics/definition of this header.
By that I mean, require the understanding of this header to
include the notion that the XMLP processor must have scanned
enough of the headers to do this additional processing, and
if it can't do it or doesn't know how to do it then it will
fault - which is what they would want anyway.  It seems like
this shouldn't require a change to the spec (even though it
probably would make it easier  8-)
-Dug


Noah_Mendelsohn@lotus.com@w3.org on 05/16/2001 05:45:11 PM

Sent by:  xml-dist-app-request@w3.org


To:   "Henrik Frystyk Nielsen" <henrikn@microsoft.com>
cc:   Doug Davis/Raleigh/IBM@IBMUS, xml-dist-app@w3.org
Subject:  RE: An analysis of mustUnderstand and related issues



Henrik writes:

>> One of the points that Noah brings up
>> is if the extensibility mechanism
>> indeed is good enough and that is a valid concern.

On the call just now, Glen brought up what I think is the area requiring
greatest attention:  if several headers for the same header all indicate
mustUnderstand, can we say anything about the order processed?  In SOAP
1.1, I think the answer is "no".  Henrik suggests (a) that lexical order
be significant -- I think that's a change to SOAP 1.1, though possibly a
good idea (b) that rollback be required if later processing fails--I'm not
sure this is practical, but we should consider it.  Also:  I don't think
anything suggests that different actor URI's are necessarily different
processors---so multiple header blocks addressed to what appear to be
different actors might, in fact, interleave.  Consider "next" as just one
example.  I'm not sure a lexical order dependency handles these cases
gracefully.

------------------------------------------------------------------------
Noah Mendelsohn                                    Voice: 1-617-693-4036
Lotus Development Corp.                            Fax: 1-617-693-8676
One Rogers Street
Cambridge, MA 02142
------------------------------------------------------------------------
Received on Wednesday, 16 May 2001 20:16:34 GMT

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